the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Oct 2022
The response of zooplankton network indicators to winter geothermal water warming in shallow reservoirs
Abstract. The increase in the temperature of surface waters has been studied for many decades, and various methods have been used to predict the most probable scenarios. The present study was undertaken to test the following research hypothesis: the warming of surface waters in winter (caused by the inflow of geothermal water) significantly modifies the dynamics, significance and type of relationships in zooplankton communities colonizing mine pit reservoirs. These relationships were examined with the use of network graph analysis for three thermal variants: warm winters (WW), moderate winters (MW), and cold winters (CW). The CW network was most cohesive, and it was controlled by eutrophic Rotifera (Trichocerca pusilla, Pompholyx sulcata, Keratella tecta) and Copepoda, with an equivalent number of positive and negative interspecific relationships. An increase in water temperature in winter led to a decrease in primary production, a decrease in the values of centrality attributes in MW and WW networks, and an increase in the significance of species that communicated with the highest number of species across sub-networks. Moderate winters increased the role of ecologically and functionally diverse species, which contributed to the heterogeneity of the MW network. The WW network was least cohesive, and it was controlled by small-sized psammophilous and phytophilous rotifers (Monommata maculata, Cephalodella spp.) and littoral cladocerans Alona spp. Adults Copepoda were not identified in the network, and the significance of antagonistic relationships decreased, which indicates that the WW network structure was weak and unstable.
The results of the impact of warm winters and the flattening of the annual water temperature amplitude on the zooplankton network may be a projection of the expected global changes. These effects are particularly important in water reservoirs exposed to anthropogenic pressure and where changes in the thermal regime can influence future ecosystem services.
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RC1: 'Comment on egusphere-2022-794', Anonymous Referee #1, 18 Nov 2022
General comments:
This study investigated zooplankton communities in three freshwater mine pit reservoirs differently influenced by geothermal water inflow, using network graph analyses. Zooplankton structure and the type of their relationships were analyzed over a period of ~2.5 years. The coldest reservoir was most cohesive and controlled by rotifers and copepods with an equivalent number of positive and negative interspecific relationships. Increased water temperature led to a decrease in primary production, thus affecting resource availability for zooplankton. Both networks of warmer reservoirs disintegrated into clusters (sub-networks). While moderate winters increased the role of ecologically and functionally diverse rotifer species, small cladocerans and rotifers formed the least cohesive network in the warmest reservoir with an apparent disruption of the phenology of copepods. The authors emphasize the relevance of their study as a potential projection for anthropogenically influenced water reservoirs facing global change by reflecting how the thermal regime might influence future ecosystem services.
Overall, the current study contains an interesting dataset and I like the network analysis approach the authors use to disentangle zooplankton interactions and food web properties. However, temperature was the only factor considered as a determinant for food web properties, while neglecting other equally important determinants that were measured such as nutrients (and other abiotics) or phytoplankton biomass. These other parameters are insufficiently presented and related to zooplankton community structure. Furthermore, all data were pooled across all time points, neglecting temporal/seasonal dynamics, thus leveling out or masking potential effects over time. Given the emphasis the authors put on the differences in seasonal thermal gradients of the different reservoirs, it would be very interesting to also look at the temporal dynamics of zooplankton in conjunction with phytoplankton and abiotic determinants. It might be useful to include additional analyses (such as linear mixed models including time as a factor) testing the effect (and effect strengths) of abiotic parameters on phytoplankton biomass, and the effect (strengths) of abiotics and phytoplankton biomass on zooplankton biomass, possibly also on diversity.
Moreover, the authors try to draw comparisons to warming effects in the course of global change and state that their study might be useful as a projection for reservoirs facing global warming – however, they do not set the investigated temperature regimes sufficiently into a respective context in the discussion. I find it a bit hard to understand how a constant geothermal warm water inflow of this extent can be related to global change scenarios, as it neither reflects a realistic predicted temperature range in the face of global warming, nor a temporal disturbance.
Overall, this study yields a great dataset, which is, however, insufficiently analyzed and presented, hampering the interpretation of the data and derivable conclusions. Therefore, I can recommend this manuscript for publication only after major revision.
Specific comments:Abstract:
• ll. 29-33: before stating the hypotheses, it would be good to give a brief overview of what the study is about
• l. 38: please state what a decrease in the values of centrality attributes indicates as the reader might not be familiar with the network analysis method
• abstract and conclusion contain very similar information and are to a large extent redundant –the results summary in the conclusions section is in my opinion clearer and more confined to the most relevant findings without going into too much detail; I recommend moving parts of the conclusions to the abstract and tighten it, while the conclusions section should take a step forward and set the relevance of the current study into a broader scientific context (e.g. regarding climate change, further steps to do etc.)Introduction:
• l. 65, l. 72: please specify the term “surface waters” and “water bodies” – what kind of water bodies are generally influenced by geothermal waters?
• ll. 73 – 74: what kind of climatic factors?
• ll. 97 – 104: this sentence is very long and mixes up effects of warming and eutrophication, please reformulate
• l. 107 – 110: in this context, the authors should refer to the potential mismatch of phyto- and zooplankton succession that has been observed under warming scenarios, e.g. earlier hatching of copepod nauplii, while phytoplankton spring bloom starts later (differential impact of warming on phototrophs and heterotrophs)
• ll. 136-138: Please specify these potential mutualistic interactions
• l. 139: rather “indicative of indirect negative effects by competing for a common food source” instead of “indicative of grazing on phytoplankton”?
• l. 140: please specify by what mechanism.
• ll. 148-149: why do the authors expect a weakened role of crustaceans under warming? Before they state that warming increases the proportion of copepod larvae and crustacean growth?
• ll. 150-151: It would be useful to state the temperature range already in the introduction and set these into the context of predictions on global warming
• l. 154: please add “seasonal” to the water temperature gradient
• ll. 157 – 160: Why is this relevant in the context of the current study which investigates stable conditions that cannot be compared to a temporal disturbance as the authors stated above?Materials and Methods:
• ll. 166: “CH1, PN, WIW” – the full names should be given at first mentioning
• ll. 172-173: Only temperature? What about inorganic nutrients and other abiotic parameters?
• l. 173: please specify atmospheric water, meltwater, and capillary water, or provide a reference
• ll. 182-185: this is a huge temperature difference – how can that be related to projected climate change scenarios? The authors really need to set their study and the respective temperature regimes into perspective.
• l. 196: coastal zones usually refer to marine systems (rather littoral zone?); please specify the “vicinity of the filter zone”
• l. 197: “Patalas trap” – please specify or provide a reference
• ll. 198-199: this is a field study, not an experiment
• l. 199: how do 3 samples à 5L add up to 20L? Apparently, the 3 different samples were pooled?
• ll. 209-217: a lot of parameters were determined in the reservoir itself (that are not described in the Results section, see below); were these parameters also determined in the geothermal water sources? That would have been great in order to estimate the amount of nutrient input fueling phytoplankton production.
• ll. 220 – 224: please specify your statistical analyses – what were the response variables tested, especially regarding zooplankton (abundances, biomass, diversity?), were these tests repeated for each sampling event, were data pooled across all time points, or was time included as a factor in the analysis? This does not become clear at all. Furthermore, it would be useful to include additional analyses (see above). So far, the authors relate their results exclusively to temperature, while it is well known that other abiotic factors and of course food supply may have equal and also interactive effects on zooplankton communities.
• l. 225: Please specify what parameters you refer you - zooplankton ID based abundances? sizes? functional groups?
• L. 233: please specify “the parameters of the entire network”Results:
• 1st paragraph: does mean annual temp. and mean winter temp. refer to the pooled data across all time points? Which time points were part of the “winter” samples? The authors state that “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp) (Table 1).” HOW did the reservoirs differ?? The authors should describe these differences and relate them to their zooplankton data, as phyto- and zooplankton is strongly influenced by a range of different abiotic parameters and not only by temperature (see also general comments).
ll. 269-274: Correlations have not been mentioned in the methods section – the authors should describe all of the analyses conducted. How was the effect of temperature on zooplankton species richness tested? This is also not specified.
• ll. 282 – 284: Were these analyses conducted across all seasons with all sampling time points pooled? In general, pooling all data over time might level out important seasonal dynamics, which are of utmost importance if the aim is to compare the food web dynamics in reservoirs differing in temporal (seasonal) thermal gradients (see above)
• ll. 285 – 287: How was this tested? As the effect of temperature on single taxa? Or were the actual temperature differences calculated between different seasons?
• ll. 326-327: again, the authors relate all differences solely to temperature without taking the other factors into account
Discussion:
• ll. 363: what do the authors mean with the term “energy of water”? does the thermal gradient refer to the temporal/seasonal gradient?
• l. 364: which processes? Please specify.
• l. 370: how do the authors come to that conclusion? Did they measure organic matter recycling? I don’t really get the argumentation here – in the warmer reservoirs organic matter cycling was already higher in winter due to the warm water inflow and did not increase as much in spring as in the CW?
• ll. 373 – 376: Was that observed in the study in terms of lower Chl. a, or is this an assumption? Wouldn't you assume that phytoplankton production increases more rapidly in spring, when the water is already warmer? How were the reservoirs stratified – was that somehow determined?
• ll. 376-380: I don’t get this point - why would heating lead to less rapid cycling? I can only imagine that under continuous recycling induced by warmer temperature, not as much organic matter accumulates rapidly, leading to clearer water and thus more macrophytes can establish?
• ll. 380 – 382: Why? Because the delta of environmental change (temperature) is higher? Please explain, this is hard to understand.
• l. 394: eutrophic conditions do not necessarily relate to good food conditions, as the food quality is usually constrained under eutrophic conditions. The authors refer to the nutrient concentrations measured in the reservoirs in the next sentence for the first time – these patterns need to be described in the Results section
• ll. 397 – 401: These results differ, but also the conditions investigated in the present study are completely different than climate change scenarios (see above) – so please specify the predictions you're referring to.
• ll. 402- 403: please explain, why would an increase in trophy levels (was that observed?) contribute to a higher content of mineral suspensions?
• ll. 451-452: does this statement refer to the aforementioned study, or to the current study?
• ll. 466-467: Why? Functionally diverse communities do not necessarily mean dynamic zooplankton communities (dynamic over time?)
• l. 474: what does immobilization refer to?
• ll. 487-489: This could also be an indication for an indirect effect of better water quality characterized by less eutrophic conditions and fewer blooms of potentially inedible phytoplankton.Citation: https://doi.org/10.5194/egusphere-2022-794-RC1 -
AC1: 'Reply on RC1', Anna Goździejewska, 07 Dec 2022
Responses to reviewer's comments
Thank you for reading our work and appreciating its value. Thank you for the valuable tips and comments. Below we have included the answers and explanations for the given problems.
Abstract
- 29-33. Before starting the hypotheses, it would be good to give a brief overview of
what the study is about
Re: We believe that the indicated sentence contains optimal (as for the needs of the abstract) information about what the research is about.
- 38. please state what a decrease in the values of centrality attributes indicates as the
reader might not be familiar with the network analysis method
Re: “…a decrease in the values of centrality attributes in the MW and WW…” changed to “…a decrease of centralization in the MW and WW…”
- abstract and conclusion contain very similar information and are to a large extent
redundant –the results summary in the conclusions section is in my opinion clearer and
more confined to the most relevant findings without going into too much detail; I
recommend moving parts of the conclusions to the abstract and tighten it, while the
conclusions section should take a step forward and set the relevance of the current study
into a broader scientific context (e.g. regarding climate change, further steps to do etc.)
Re: Suggested changes will be taken into account
Introduction
L.65-72 – Changed in:
“The fluctuations and/or permanent changes in the thermal profile of surface waters have been largely associated with the discharge of industrial cooling water, eg. coastal seawater (Capuzzo, 1980), lakes and artificial reservoirs (Ejsmont-Karabin and Wągleńska, 1988, Zargar and Ghosh, 2006; Vandysh, 2009; Ejsmont-Karabin, 2011).
There is a general scarcity of research on the hydrobiological impact of geothermal water that reaches water bodies, such as fish culture tanks (Sellami et al., 2009), artificial bathing tanks (Dash et al. 2012), and geothermal water areas (Baksir et al. 2022), and the few available studies have focused mostly on the tropical regions. “
L.73-74 – changed in: „climatic changes”
“In recent decades, climatic changes associated with a rise in global temperature, in particular in northern latitudes, have been recognized as an additional driver of changes in the thermal profile of surface water bodies”
- 97 – 104 – changed in:
“Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces responses in freshwater zooplankton similar to responses to accelerated eutrophication. The reactions observed were: an increase in total zooplankton density and biomass, changes in species composition (Williamson et al., 2002; Visconti, 2008; Vandysh, 2009; Arlic et al., 2013), elimination of seasonal succession, including a decrease in the proportion of cold-water species in spring rotifer communities (Ejsmont- Karabin et al., 2020), degrease in size of copepods, and accelerated growth of cladocerans characterized by small body size/low biomass (Daufresne et al., 2009; Gutierrez, 2016; Evans et al., 2020; Zhou, 2020)”.
107 – 110: in this context, the authors should refer to the potential mismatch of
phyto- and zooplankton succession that has been observed under warming scenarios, e.g. earlier hatching of copepod nauplii, while phytoplankton spring bloom starts later
(differential impact of warming on phototrophs and heterotrophs)
We agree with the highlighted phenomena and dependencies. Here we briefly present the effects of the biological effect of increased water temperature on zooplankton, confirmed by previous research. However, we do not intend to develop the problem of seasonal changes, because it is not the focus of this paper.
- 136-138: Please specify these potential mutualistic interactions???
We assumed that positive interactions between two taxa are correlated with an increase in their biomass as the effect of consumer guilds, where independent species share resources. It refers to the mutualistic interactions in the broader, ecosystemic and evolutionary sense (Krebs, 2009).
- 139: corrected - “indicative of indirect negative effects by competing for a common food source” instead of “indicative of grazing on phytoplankton”
L.140. please specify by what mechanism.
“The temperature gradient differentiates the rate of circulation of organic matter and mineral elements released during decomposition processes. Thus, it affects their availability for the development of primary producers, indirectly determining the resources and type of food for zooplankton”
- 148-149: why do the authors expect a weakened role of crustaceans under warming?
Before they state that warming increases the proportion of copepod larvae and crustacean growth? - corrected, clarified (according l 97-104)
- 150-151: It would be useful to state the temperature range already in the
introduction and set these into the context of predictions on global warming
We do not compare the range and level of temperature, especially in winter, in the studied reservoirs with global warming forecasts. However, we propose to use the obtained results for a broad interpretation of the influence of the thermal factor on the network of interactions between species of zooplankton.
- 154: please add “seasonal” to the water temperature gradient
We analyze the water temperature gradient between the reservoirs, which, as mentioned above, also applies to differences in the average annual temperature. It is therefore not a seasonal gradient. Of course, the thermal classes of the compared reservoirs were determined on the basis of the temperature gradient in winter, but the consequences of the influence/differences in the zooplankton network are assessed on the basis of a database of year-round results. Hence, we believe that it is not necessary to specify the "seasonal gradient"
- 157 – 160: Why is this relevant in the context of the current study which investigates
stable conditions that cannot be compared to a temporal disturbance as the authors stated above?
The term "stable conditions" means their repeatability for many years of reservoir using. Thus, from the perspective of the heated reservoir, "warm winters" affected the ecosystem for long time and the changes found in it are not "an accident" of one disturbance. Since thermal changes on the globe occur slowly, gradually, but over the long term, our results can be helpful in interpreting global changes.
Methods
- 172-173: Only temperature? What about inorganic nutrients and other abiotic
parameters?
The description concerns the temperature as a variable which is the main problem of the analysis, differentiating the compared reservoirs. Other abiotic factors are given in Table 1 and commented on in the Results section.
- 182-185: this is a huge temperature difference – how can that be related to projected
climate change scenarios? The authors really need to set their study and the respective
temperature regimes into perspective.
Please see response for comments L. 150-151
- 196: coastal zones usually refer to marine systems (rather littoral zone?); please
specify the “vicinity of the filter zone”
Changed to „litoral zone” and added reference explaining „filter zone” (Goździejewska et al. 2018). For better explanation, what the filter zone is, please see the description in doi.org/10.1051/kmae/2018020
- 197: “Patalas trap” – please specify or provide a reference
Changed to 5-litre sampler
- 198-199: this is a field study, not an experiment
Changed to “field study”
- 199: how do 3 samples à 5L add up to 20L? Apparently, the 3 different samples were
pooled?
A separate sample of 20 liters was collected at each site. Samples were not combined. Each sample was analyzed separately.
- 209-217: a lot of parameters were determined in the reservoir itself (that are not
described in the Results section, see below); were these parameters also determined in
the geothermal water sources? That would have been great in order to estimate the
amount of nutrient input fueling phytoplankton production.
The chemical parameters of geothermal waters have not been tested for the purposes of this study. Due to their social (angling) and natural role, the owner of the area (Bełchatów Mine) controls the quality and sanitary condition of the waters supplying tested reservoirs. Here we focus on the thermal factor.
- 220 – 224: please specify your statistical analyses – what were the response variables
tested, especially regarding zooplankton (abundances, biomass, diversity?), were these
tests repeated for each sampling event, were data pooled across all time points, or was
time included as a factor in the analysis? This does not become clear at all. Furthermore,
it would be useful to include additional analyses (see above). So far, the authors relate
their results exclusively to temperature, while it is well known that other abiotic factors
and of course food supply may have equal and also interactive effects on zooplankton
communities.
Statistical tests were performed on a set of "raw" data, i.e. the results from each separately analyzed sample. The variability of abundance and biomass, variability of zooplankton taxonomic diversity indices, and variability of water physical and chemical parameters were tested, and the differences between thermal classes are shown in Table 1.
- 225: Please specify what parameters you refer you - zooplankton ID based
abundances? sizes? functional groups?
The biomass values of each of the analyzed zooplankton taxa were compared between thermal classes (Tab. S1).
- 233: please specify “the parameters of the entire network”
Attributes of the entire network refers to its tendency to clustering, centralization, density, heterogeneity and paths lengths.
Results
- 1st paragraph: does mean annual temp. and mean winter temp. refer to the pooled data across all time points? Which time points were part of the “winter” samples? The authors state that “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp) (Table 1).” HOW did the reservoirs differ?? The authors should describe these differences and relate them to their zooplankton data, as phyto- and zooplankton is strongly influenced by a range of different abiotic parameters and not only by temperature (see also general comments).
Winter samples were for months of December–February.
The results of the physical and chemical parameters of water were elaborated in detail and presented in Table 1. Differences in average values were statistically compared. The authors repeatedly relate zooplankton data and the structure of zooplankton networks to abiotic conditions.
- 269-274: Correlations have not been mentioned in the methods section – the authors
should describe all of the analyses conducted. How was the effect of temperature on
zooplankton species richness tested? This is also not specified.
Added: Spearman's rank correlation analysis (p < 0.05) was used to test for correlations between temperature and zooplankton species richness, and between temperature and the others physical and chemical variables of water.
- 282 – 284: Were these analyses conducted across all seasons with all sampling time
points pooled? In general, pooling all data over time might level out important seasonal
dynamics, which are of utmost importance if the aim is to compare the food web dynamics in reservoirs differing in temporal (seasonal) thermal gradients (see above)
We understand that seasonal dynamics periodically change the structure of the food web. However, our goal was not to compare temporal variability across seasons. This concerns a different research topic. The data entered into the model concerned the entire analyzed season, which is consistent with the purpose and methodology of the study. Such an approach synthesizing intra-seasonal variability is needed to answer the question posed in the introduction, which concerned the comparison of entire seasons, not the dynamics within them. This is the approach found in the literature (Kruk et al., 2020, 2021; Goździejewska and Kruk 2022).
- 285 – 287: How was this tested? As the effect of temperature on single taxa? Or were the actual temperature differences calculated between different seasons?
The biomass of each taxon identified in each thermal class was calculated. The K-W test determined the significance of differences in the mean biomass of taxa between thermal classes.
- 326-327: again, the authors relate all differences solely to temperature without taking the other factors into account
Three interspecies zooplankton networks were built based on the main differentiating indicator, i.e. water temperature. On this basis, three thermal classes were determined. Hence, the differences in network attributes were related to thermal conditions. The influence and connection with other abiotic parameters is repeatedly emphasized in the Discussion section.
Discussion
- 363: what do the authors mean with the term “energy of water”? does the thermal
gradient refer to the temporal/seasonal gradient?
“Temperature is a physical factor that modifies flow and transformations of the biologically accumulated energy in the water…” This applies to every aspect of time, but here we compare the differentiated water thermals in the tested reservoirs.
- 364: which processes? Please specify
The processes described above in L140.
- 370: how do the authors come to that conclusion? Did they measure organic matter
recycling? I don’t really get the argumentation here – in the warmer reservoirs organic
matter cycling was already higher in winter due to the warm water inflow and did not
increase as much in spring as in the CW?
The rate of circulation of matter has not been studied. The researched reservoirs are shallow, polymictic. Therefore, there is homothermy in the reservoirs and equalization of oxygen concentration from the surface to the bottom. Due to the higher water temperature, mineralization of organic matter and its circulation in the winter period is faster in warmer reservoirs than in cold ones. The intensive mineralization of organic matter in WW is indicated by a significantly lower concentration of dissolved oxygen in water compared to CW and MW (Table 1). At the same time, nutrients available in water are used by macrophytes, which deposit them in their tissues. Thus, the increase in water temperature in spring has a much clearer effect on the activation of the above processes of circulation of elements in cooler reservoirs than in warmer reservoirs, where their resources are smaller.
- 373 – 376: Was that observed in the study in terms of lower Chl. a, or is this an
assumption? Wouldn't you assume that phytoplankton production increases more rapidly
in spring, when the water is already warmer? How were the reservoirs stratified – was
that somehow determined?
An increase in the concentration of chlorophyll a was observed along with the heating of water in the CW class. However, the chl a values did not change in the WW class. The reservoirs are shallow, and thermal and chemical stratification was not observed (methodology).
- 376-380: I don’t get this point - why would heating lead to less rapid cycling? I can
only imagine that under continuous recycling induced by warmer temperature, not as
much organic matter accumulates rapidly, leading to clearer water and thus more
macrophytes can establish?
Winter warming does not mean an increase in the circulation of matter within the plankton. On the other hand, it may contribute to its capture by macrophytes that find thermal conditions for development (Kruk et al. 2022). In addition, the observations are supported by studies by Wollrab et al. (2021).
- 380 – 382: Why? Because the delta of environmental change (temperature) is higher?
Please explain, this is hard to understand.
The mechanism of the influence of temperature on the feeding conditions of zooplankton in the studied reservoirs was explained above.
- 394: eutrophic conditions do not necessarily relate to good food conditions, as the
food quality is usually constrained under eutrophic conditions. The authors refer to the
nutrient concentrations measured in the reservoirs in the next sentence for the first time – these patterns need to be described in the Results section
We conclude about good nutritional conditions of CW based on the response of specific species (indicators of increased trophy). In the Results section, it was stated that the differences in "trophic" parameters were significant between the thermal classes and referred to Table 1
- 397 – 401: These results differ, but also the conditions investigated in the present
study are completely different than climate change scenarios (see above) – so please
specify the predictions you're referring to.
According to the answer L 150-151, we do not compare, but only propose to use in predicting global changes and their effects.
- 402-403: please explain, why would an increase in trophy levels (was that
observed?) contribute to a higher content of mineral suspensions?
These observations have been confirmed by many previous studies, also in the same reservoirs (please see references).
- 451-452: does this statement refer to the aforementioned study, or to the current
study?
To the current but also earlier by Goździejewska et al. 2018.
- 466-467: Why? Functionally diverse communities do not necessarily mean dynamic
zooplankton communities (dynamic over time?)
In this term, Dynamics means the dynamics (number and strength) of interspecies relationships mentioned above
- 474: what does immobilization refer to?
Immobilization of nutrients/organic matter in macrophyte tissues
- 487-489: This could also be an indication for an indirect effect of better water quality
characterized by less eutrophic conditions and fewer blooms of potentially inedible
phytoplankton.
Of course, such conditions prevailed there, as the results show (Tab.1)
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AC1: 'Reply on RC1', Anna Goździejewska, 07 Dec 2022
-
RC2: 'Comment on egusphere-2022-794', Anonymous Referee #2, 07 Dec 2022
Authors aimed an important aspect of functioning of shallow reservoir ecosystems (three freshwater mine pit reservoirs) under the pressure imaging the global warming, showing the response of zooplankton network and presenting a new approach to examine zooplankton interspecific interactions with the use of the network graph analysis. The study presents interesting both, the dataset and analysis, but apart the temperature the other factors (cofactors) which can structure zooplankton network should also be analyzed and estimated, showing how much temperature and how much other factors (time, food, and other measured parameters, which were collected but not presented in analysis) are responsible for the observed zooplankton pattern. Seasonal changes should also be incorporated into such analysis, as this changes my increase or decrease the effect size. Several models (LMM – Linear Mixed Models including RM – Repeated Measure, NLMMs & GLMMS – Nonlinear and Generalized Linear Mixed Models) may work well in this case with fixed and random effect components. Sample size (20 L collected with the Patalas trap) sims to be correct, but collection of samples 1 m below the surface may underestimate especially the Copepoda group, but also Cladocera, both groups may be very abundant near the bottom (as examples please consult Bittel (1976), PapiÅska & Pijanowska (1980) and Klemetsen et al. (2020).
The Shannon’s diversity index was calculated with the stats software (MVSP 3.22), which calculate the index with its understanding for years before 1990s, which not allows for value comparison. Later, in the early 1990s, introduced was the rarefaction method for abundance standardization and proper comparison of Shannon’s diversity and species richness. For the proper Shannon’s index comparison and rarefaction calculation please consult free software like EstimateS or EcoSimR and Vegan R packages.
In the Results, Discussion and Conclusions – Authors explained all observed zooplankton differences exclusively by temperature, without showing the evidence of the lack of such influence of the other factors. In general, the Discussion should be rewritten (please avoid the speculations, just discuss the observed pattern and provide the “take-home message”).
The study is very valuable, based on the novel approach to examine of zooplankton structure, but due to all facts mention above I recommend this manuscript for publication after major revision.
Specific comments:
English through of the manuscript should be corrected, as an example, among others - Authors often have been using “in” in spite of “of” in many sentences.
The abstract should be rearranged. Before the hypothesis, please describe the state of the subject field knowledge, then characterize the research you did, hypothesis, the results and an info about conclusions.
Line 97-104: “Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces similar responses in freshwater zooplankton to accelerated eutrophication…” – awkward sentence.
Line 135: “biomass parameters” – delete “parameters” or specify what parameters of biomass were used.
Lines 150-156: since physical and chemical parameters (including temperature) are relatively stable – than all of them, not only temperature should structure zooplankton community and it is hard to say that the temperature was the main factor, other parameters (cofactors) should also be analyzed and then an influence of all factors should be estimated, and perhaps the temperature may be primarily responsible for estimated % of the effect size (in ecology we are looking for the effect size at least 20% or larger).
Line 196 – “the coastal zone” should be replaced with “littoral”, or “near shore zone” (as coastal refers exclusively to marine environments). Please explain “vicinity of the filter zone”.
Line 199 – the “experiment” – wrong use, this is a field study, not experiment.
Line 267: “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp)” – how this may affect observed zooplankton pattern?
Lines 272-284: how significant difference of species richness and Shannon’s diversity were estimated without abundance standardization and rarefaction?
Line 363 – please explain “energy of water”.
Line 375 – “less energy was generated” – awkward description, did you really measure the energy generation or just observed the lower/higher temperature of water?
Lines 530-532 – The conclusion about the role of Copepods is doubtful as the sampling procedure underestimated both, the abundance and species richness of this group.
References:
Bittel, L., 1976. Near-bottom plankton as a productive element in the lake ecosystem. Acta UNC, Limnological Papers 9:45-64.
Klemetsen, A., B. M. Aase & P. A. Amundsen, 2020. Diversity, abundance, and life histories of littoral chydorids (Cladocera: Chydoridae) in a subarctic European lake. Journal of Crustacean Biology 40(5):534-543 doi:10.1093/jcbiol/ruaa048.
PapiÅska, K. & J. Pijanowska, 1980. Pelagic and near-bottom crustaceans in five masurian Lakes. Ekologia polska 28:219-229.
Citation: https://doi.org/10.5194/egusphere-2022-794-RC2 -
AC2: 'Reply on RC2', Anna Goździejewska, 14 Dec 2022
Responses to reviewer's comments
Thank you for reading our work and appreciating its value. Thank you for the valuable tips and comments. Below we have included the answers and explanations for the given problems.
Seasonal changes should also be incorporated into such analysis, as this changes my increase or decrease the effect size.
We understand that seasonal dynamics periodically change the structure of the food web. However, our goal was not to compare temporal variability across seasons. This concerns a different research topic. The data entered into the model concerned the entire analyzed season, which is consistent with the purpose and methodology of the study. Such an approach synthesizing intra-seasonal variability is needed to answer the question posed in the introduction, which concerned the comparison of entire seasons, not the dynamics within them. This is the approach found in the literature (Kruk et al., 2020, 2021; Goździejewska and Kruk 2022).
Sample size (20 L collected with the Patalas trap) sims to be correct, but collection of samples 1 m below the surface may underestimate especially the Copepoda group, but also Cladocera, both groups may be very abundant near the bottom (as examples please consult Bittel (1976), Papińska & Pijanowska (1980) and Klemetsen et al. (2020).
The studied reservoirs are very shallow (⁓ 2 m), flow-through and mixed to the bottom (see Methods). Thus, the aerobic and thermal conditions are equal (no stratification). Thus, there is no significant variation in abiotic conditions that could affect the vertical distribution of crustaceans. In addition, it is also confirmed that bottom harpacticoids were often found in the zooplankton samples examined (Table S1). Harpacticoida are poor swimmers and their systematic presence in the water column is usually the result of wind mixing and mechanical resuspension with sediments (e.g. Goździejewska et al. 2006; http://www.ejpau.media.pl/volume9/issue2/art-16.html). Thus, we believe that due to the above factors (morphometry and abiotic factors), taxa of pelagic crustaceans (much better swimmers than Harpacticoida) are evenly distributed throughout the water column. Thus, in the studied reservoirs we find completely different environmental conditions than in the large and deep lakes referred to in the three proposed references.
The Shannon’s diversity index was calculated with the stats software (MVSP 3.22), which
calculate the index with its understanding for years before 1990s, which not allows for
value comparison. Later, in the early 1990s, introduced was the rarefaction method for
abundance standardization and proper comparison of Shannon’s diversity and species
richness. For the proper Shannon’s index comparison and rarefaction calculation please
consult free software like EstimateS or EcoSimR and Vegan R packages.
Thank you for pointing to other tools for calculating biodiversity. The results obtained at present are not and will not be compared in time and place. In this work, they are also not the main research problem. However, after reviewing the proposed packages, they will certainly be used in future research.
In the Results, Discussion and Conclusions – Authors explained all observed zooplankton
differences exclusively by temperature, without showing the evidence of the lack of such
influence of the other factors.
Three interspecies zooplankton networks were built based on the main differentiating indicator, i.e. water temperature. On this basis, three thermal classes were determined. Hence, the differences in network attributes were related to thermal conditions. The influence and connection with other abiotic parameters is repeatedly emphasized in the Discussion section.
In general, the Discussion should be rewritten (please avoid the speculations, just discuss the observed pattern and provide the “take-home message”).
Some changes have been made to the Discussion section. The discussion of each of the researched issues is based on a large set of relevant references, which are intended to prevent any speculation.
Specific comments:
English through of the manuscript should be corrected, as an example, among others -
Authors often have been using “in” in spite of “of” in many sentences.
English has been professional verified.
The abstract should be rearranged. Before the hypothesis, please describe the state of the subject field knowledge, then characterize the research you did, hypothesis, the results and an info about conclusions.
The volume of the abstract does not make it possible to describe the state of knowledge on the subject raised in the work. The relevant content is included in the Introduction. We believe that the sentence in which we present the hypothesis contains concise information about the work problem. Certain Abstract content will be re-written.
Line 97-104: “Previous research has demonstrated that an increase in mean
seasonal/annual water temperature induces similar responses in freshwater zooplankton
to accelerated eutrophication…” – awkward sentence.
Corrected to:
“Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces responses in freshwater zooplankton similar to responses to accelerated eutrophication”
Line 135: “biomass parameters” – delete “parameters” or specify what parameters of
biomass were used. – corrected
Lines 150-156: since physical and chemical parameters (including temperature) are
relatively stable – than all of them, not only temperature should structure zooplankton
community and it is hard to say that the temperature was the main factor, other
parameters (cofactors) should also be analyzed and then an influence of all factors should be estimated, and perhaps the temperature may be primarily responsible for estimated % of the effect size (in ecology we are looking for the effect size at least 20% or larger). Line 267: “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp)” – how this may affect observed zooplankton pattern?
It is obvious that many biotic and abiotic factors determine the functioning of an aquatic ecosystem. Their interaction also shapes planktonic networks. In this study, the structure of the zooplankton network was related to temperature as the main factor differentiating the three studied reservoirs (thermal classes). We did not omit the probable impact of other measured parameters on zooplankton, providing their values and correlating them in the Results section and repeatedly emphasizing them in the Discussion section. In the Discussion, we tried to discuss every relationship between the zooplankton network results obtained and trophic conditions (here measured as Chla, organic matter, nutrients) and suspended solids conditions, based on the appropriate bibliographic database and previously published own results.
Line 196 – “the coastal zone” should be replaced with “littoral”, or “near shore zone” (as
coastal refers exclusively to marine environments). Please explain “vicinity of the filter
zone”.
Changed to „litoral zone” and added reference explaining „filter zone” (Goździejewska et al. 2018). For better explanation, what the filter zone is, please see the description in doi.org/10.1051/kmae/2018020
Line 199 – the “experiment” – wrong use, this is a field study, not experiment.
Changed to “field study”
Lines 272-284: how significant difference of species richness and Shannon’s diversity were estimated without abundance standardization and rarefaction?
Please see answer on biodiversity calculations, above.
Line 363 – please explain “energy of water”- corrected in the text to:
“Temperature is a physical factor that modifies flow and transformations of the energy in the water….
Line 375 – “less energy was generated” – awkward description, did you really measure the energy generation or just observed the lower/higher temperature of water?
Removed: “…less energy was generated”
Lines 530-532 – The conclusion about the role of Copepods is doubtful as the sampling
procedure underestimated both, the abundance and species richness of this group.
Please see the explanation above.
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AC2: 'Reply on RC2', Anna Goździejewska, 14 Dec 2022
Status: closed
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RC1: 'Comment on egusphere-2022-794', Anonymous Referee #1, 18 Nov 2022
General comments:
This study investigated zooplankton communities in three freshwater mine pit reservoirs differently influenced by geothermal water inflow, using network graph analyses. Zooplankton structure and the type of their relationships were analyzed over a period of ~2.5 years. The coldest reservoir was most cohesive and controlled by rotifers and copepods with an equivalent number of positive and negative interspecific relationships. Increased water temperature led to a decrease in primary production, thus affecting resource availability for zooplankton. Both networks of warmer reservoirs disintegrated into clusters (sub-networks). While moderate winters increased the role of ecologically and functionally diverse rotifer species, small cladocerans and rotifers formed the least cohesive network in the warmest reservoir with an apparent disruption of the phenology of copepods. The authors emphasize the relevance of their study as a potential projection for anthropogenically influenced water reservoirs facing global change by reflecting how the thermal regime might influence future ecosystem services.
Overall, the current study contains an interesting dataset and I like the network analysis approach the authors use to disentangle zooplankton interactions and food web properties. However, temperature was the only factor considered as a determinant for food web properties, while neglecting other equally important determinants that were measured such as nutrients (and other abiotics) or phytoplankton biomass. These other parameters are insufficiently presented and related to zooplankton community structure. Furthermore, all data were pooled across all time points, neglecting temporal/seasonal dynamics, thus leveling out or masking potential effects over time. Given the emphasis the authors put on the differences in seasonal thermal gradients of the different reservoirs, it would be very interesting to also look at the temporal dynamics of zooplankton in conjunction with phytoplankton and abiotic determinants. It might be useful to include additional analyses (such as linear mixed models including time as a factor) testing the effect (and effect strengths) of abiotic parameters on phytoplankton biomass, and the effect (strengths) of abiotics and phytoplankton biomass on zooplankton biomass, possibly also on diversity.
Moreover, the authors try to draw comparisons to warming effects in the course of global change and state that their study might be useful as a projection for reservoirs facing global warming – however, they do not set the investigated temperature regimes sufficiently into a respective context in the discussion. I find it a bit hard to understand how a constant geothermal warm water inflow of this extent can be related to global change scenarios, as it neither reflects a realistic predicted temperature range in the face of global warming, nor a temporal disturbance.
Overall, this study yields a great dataset, which is, however, insufficiently analyzed and presented, hampering the interpretation of the data and derivable conclusions. Therefore, I can recommend this manuscript for publication only after major revision.
Specific comments:Abstract:
• ll. 29-33: before stating the hypotheses, it would be good to give a brief overview of what the study is about
• l. 38: please state what a decrease in the values of centrality attributes indicates as the reader might not be familiar with the network analysis method
• abstract and conclusion contain very similar information and are to a large extent redundant –the results summary in the conclusions section is in my opinion clearer and more confined to the most relevant findings without going into too much detail; I recommend moving parts of the conclusions to the abstract and tighten it, while the conclusions section should take a step forward and set the relevance of the current study into a broader scientific context (e.g. regarding climate change, further steps to do etc.)Introduction:
• l. 65, l. 72: please specify the term “surface waters” and “water bodies” – what kind of water bodies are generally influenced by geothermal waters?
• ll. 73 – 74: what kind of climatic factors?
• ll. 97 – 104: this sentence is very long and mixes up effects of warming and eutrophication, please reformulate
• l. 107 – 110: in this context, the authors should refer to the potential mismatch of phyto- and zooplankton succession that has been observed under warming scenarios, e.g. earlier hatching of copepod nauplii, while phytoplankton spring bloom starts later (differential impact of warming on phototrophs and heterotrophs)
• ll. 136-138: Please specify these potential mutualistic interactions
• l. 139: rather “indicative of indirect negative effects by competing for a common food source” instead of “indicative of grazing on phytoplankton”?
• l. 140: please specify by what mechanism.
• ll. 148-149: why do the authors expect a weakened role of crustaceans under warming? Before they state that warming increases the proportion of copepod larvae and crustacean growth?
• ll. 150-151: It would be useful to state the temperature range already in the introduction and set these into the context of predictions on global warming
• l. 154: please add “seasonal” to the water temperature gradient
• ll. 157 – 160: Why is this relevant in the context of the current study which investigates stable conditions that cannot be compared to a temporal disturbance as the authors stated above?Materials and Methods:
• ll. 166: “CH1, PN, WIW” – the full names should be given at first mentioning
• ll. 172-173: Only temperature? What about inorganic nutrients and other abiotic parameters?
• l. 173: please specify atmospheric water, meltwater, and capillary water, or provide a reference
• ll. 182-185: this is a huge temperature difference – how can that be related to projected climate change scenarios? The authors really need to set their study and the respective temperature regimes into perspective.
• l. 196: coastal zones usually refer to marine systems (rather littoral zone?); please specify the “vicinity of the filter zone”
• l. 197: “Patalas trap” – please specify or provide a reference
• ll. 198-199: this is a field study, not an experiment
• l. 199: how do 3 samples à 5L add up to 20L? Apparently, the 3 different samples were pooled?
• ll. 209-217: a lot of parameters were determined in the reservoir itself (that are not described in the Results section, see below); were these parameters also determined in the geothermal water sources? That would have been great in order to estimate the amount of nutrient input fueling phytoplankton production.
• ll. 220 – 224: please specify your statistical analyses – what were the response variables tested, especially regarding zooplankton (abundances, biomass, diversity?), were these tests repeated for each sampling event, were data pooled across all time points, or was time included as a factor in the analysis? This does not become clear at all. Furthermore, it would be useful to include additional analyses (see above). So far, the authors relate their results exclusively to temperature, while it is well known that other abiotic factors and of course food supply may have equal and also interactive effects on zooplankton communities.
• l. 225: Please specify what parameters you refer you - zooplankton ID based abundances? sizes? functional groups?
• L. 233: please specify “the parameters of the entire network”Results:
• 1st paragraph: does mean annual temp. and mean winter temp. refer to the pooled data across all time points? Which time points were part of the “winter” samples? The authors state that “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp) (Table 1).” HOW did the reservoirs differ?? The authors should describe these differences and relate them to their zooplankton data, as phyto- and zooplankton is strongly influenced by a range of different abiotic parameters and not only by temperature (see also general comments).
ll. 269-274: Correlations have not been mentioned in the methods section – the authors should describe all of the analyses conducted. How was the effect of temperature on zooplankton species richness tested? This is also not specified.
• ll. 282 – 284: Were these analyses conducted across all seasons with all sampling time points pooled? In general, pooling all data over time might level out important seasonal dynamics, which are of utmost importance if the aim is to compare the food web dynamics in reservoirs differing in temporal (seasonal) thermal gradients (see above)
• ll. 285 – 287: How was this tested? As the effect of temperature on single taxa? Or were the actual temperature differences calculated between different seasons?
• ll. 326-327: again, the authors relate all differences solely to temperature without taking the other factors into account
Discussion:
• ll. 363: what do the authors mean with the term “energy of water”? does the thermal gradient refer to the temporal/seasonal gradient?
• l. 364: which processes? Please specify.
• l. 370: how do the authors come to that conclusion? Did they measure organic matter recycling? I don’t really get the argumentation here – in the warmer reservoirs organic matter cycling was already higher in winter due to the warm water inflow and did not increase as much in spring as in the CW?
• ll. 373 – 376: Was that observed in the study in terms of lower Chl. a, or is this an assumption? Wouldn't you assume that phytoplankton production increases more rapidly in spring, when the water is already warmer? How were the reservoirs stratified – was that somehow determined?
• ll. 376-380: I don’t get this point - why would heating lead to less rapid cycling? I can only imagine that under continuous recycling induced by warmer temperature, not as much organic matter accumulates rapidly, leading to clearer water and thus more macrophytes can establish?
• ll. 380 – 382: Why? Because the delta of environmental change (temperature) is higher? Please explain, this is hard to understand.
• l. 394: eutrophic conditions do not necessarily relate to good food conditions, as the food quality is usually constrained under eutrophic conditions. The authors refer to the nutrient concentrations measured in the reservoirs in the next sentence for the first time – these patterns need to be described in the Results section
• ll. 397 – 401: These results differ, but also the conditions investigated in the present study are completely different than climate change scenarios (see above) – so please specify the predictions you're referring to.
• ll. 402- 403: please explain, why would an increase in trophy levels (was that observed?) contribute to a higher content of mineral suspensions?
• ll. 451-452: does this statement refer to the aforementioned study, or to the current study?
• ll. 466-467: Why? Functionally diverse communities do not necessarily mean dynamic zooplankton communities (dynamic over time?)
• l. 474: what does immobilization refer to?
• ll. 487-489: This could also be an indication for an indirect effect of better water quality characterized by less eutrophic conditions and fewer blooms of potentially inedible phytoplankton.Citation: https://doi.org/10.5194/egusphere-2022-794-RC1 -
AC1: 'Reply on RC1', Anna Goździejewska, 07 Dec 2022
Responses to reviewer's comments
Thank you for reading our work and appreciating its value. Thank you for the valuable tips and comments. Below we have included the answers and explanations for the given problems.
Abstract
- 29-33. Before starting the hypotheses, it would be good to give a brief overview of
what the study is about
Re: We believe that the indicated sentence contains optimal (as for the needs of the abstract) information about what the research is about.
- 38. please state what a decrease in the values of centrality attributes indicates as the
reader might not be familiar with the network analysis method
Re: “…a decrease in the values of centrality attributes in the MW and WW…” changed to “…a decrease of centralization in the MW and WW…”
- abstract and conclusion contain very similar information and are to a large extent
redundant –the results summary in the conclusions section is in my opinion clearer and
more confined to the most relevant findings without going into too much detail; I
recommend moving parts of the conclusions to the abstract and tighten it, while the
conclusions section should take a step forward and set the relevance of the current study
into a broader scientific context (e.g. regarding climate change, further steps to do etc.)
Re: Suggested changes will be taken into account
Introduction
L.65-72 – Changed in:
“The fluctuations and/or permanent changes in the thermal profile of surface waters have been largely associated with the discharge of industrial cooling water, eg. coastal seawater (Capuzzo, 1980), lakes and artificial reservoirs (Ejsmont-Karabin and Wągleńska, 1988, Zargar and Ghosh, 2006; Vandysh, 2009; Ejsmont-Karabin, 2011).
There is a general scarcity of research on the hydrobiological impact of geothermal water that reaches water bodies, such as fish culture tanks (Sellami et al., 2009), artificial bathing tanks (Dash et al. 2012), and geothermal water areas (Baksir et al. 2022), and the few available studies have focused mostly on the tropical regions. “
L.73-74 – changed in: „climatic changes”
“In recent decades, climatic changes associated with a rise in global temperature, in particular in northern latitudes, have been recognized as an additional driver of changes in the thermal profile of surface water bodies”
- 97 – 104 – changed in:
“Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces responses in freshwater zooplankton similar to responses to accelerated eutrophication. The reactions observed were: an increase in total zooplankton density and biomass, changes in species composition (Williamson et al., 2002; Visconti, 2008; Vandysh, 2009; Arlic et al., 2013), elimination of seasonal succession, including a decrease in the proportion of cold-water species in spring rotifer communities (Ejsmont- Karabin et al., 2020), degrease in size of copepods, and accelerated growth of cladocerans characterized by small body size/low biomass (Daufresne et al., 2009; Gutierrez, 2016; Evans et al., 2020; Zhou, 2020)”.
107 – 110: in this context, the authors should refer to the potential mismatch of
phyto- and zooplankton succession that has been observed under warming scenarios, e.g. earlier hatching of copepod nauplii, while phytoplankton spring bloom starts later
(differential impact of warming on phototrophs and heterotrophs)
We agree with the highlighted phenomena and dependencies. Here we briefly present the effects of the biological effect of increased water temperature on zooplankton, confirmed by previous research. However, we do not intend to develop the problem of seasonal changes, because it is not the focus of this paper.
- 136-138: Please specify these potential mutualistic interactions???
We assumed that positive interactions between two taxa are correlated with an increase in their biomass as the effect of consumer guilds, where independent species share resources. It refers to the mutualistic interactions in the broader, ecosystemic and evolutionary sense (Krebs, 2009).
- 139: corrected - “indicative of indirect negative effects by competing for a common food source” instead of “indicative of grazing on phytoplankton”
L.140. please specify by what mechanism.
“The temperature gradient differentiates the rate of circulation of organic matter and mineral elements released during decomposition processes. Thus, it affects their availability for the development of primary producers, indirectly determining the resources and type of food for zooplankton”
- 148-149: why do the authors expect a weakened role of crustaceans under warming?
Before they state that warming increases the proportion of copepod larvae and crustacean growth? - corrected, clarified (according l 97-104)
- 150-151: It would be useful to state the temperature range already in the
introduction and set these into the context of predictions on global warming
We do not compare the range and level of temperature, especially in winter, in the studied reservoirs with global warming forecasts. However, we propose to use the obtained results for a broad interpretation of the influence of the thermal factor on the network of interactions between species of zooplankton.
- 154: please add “seasonal” to the water temperature gradient
We analyze the water temperature gradient between the reservoirs, which, as mentioned above, also applies to differences in the average annual temperature. It is therefore not a seasonal gradient. Of course, the thermal classes of the compared reservoirs were determined on the basis of the temperature gradient in winter, but the consequences of the influence/differences in the zooplankton network are assessed on the basis of a database of year-round results. Hence, we believe that it is not necessary to specify the "seasonal gradient"
- 157 – 160: Why is this relevant in the context of the current study which investigates
stable conditions that cannot be compared to a temporal disturbance as the authors stated above?
The term "stable conditions" means their repeatability for many years of reservoir using. Thus, from the perspective of the heated reservoir, "warm winters" affected the ecosystem for long time and the changes found in it are not "an accident" of one disturbance. Since thermal changes on the globe occur slowly, gradually, but over the long term, our results can be helpful in interpreting global changes.
Methods
- 172-173: Only temperature? What about inorganic nutrients and other abiotic
parameters?
The description concerns the temperature as a variable which is the main problem of the analysis, differentiating the compared reservoirs. Other abiotic factors are given in Table 1 and commented on in the Results section.
- 182-185: this is a huge temperature difference – how can that be related to projected
climate change scenarios? The authors really need to set their study and the respective
temperature regimes into perspective.
Please see response for comments L. 150-151
- 196: coastal zones usually refer to marine systems (rather littoral zone?); please
specify the “vicinity of the filter zone”
Changed to „litoral zone” and added reference explaining „filter zone” (Goździejewska et al. 2018). For better explanation, what the filter zone is, please see the description in doi.org/10.1051/kmae/2018020
- 197: “Patalas trap” – please specify or provide a reference
Changed to 5-litre sampler
- 198-199: this is a field study, not an experiment
Changed to “field study”
- 199: how do 3 samples à 5L add up to 20L? Apparently, the 3 different samples were
pooled?
A separate sample of 20 liters was collected at each site. Samples were not combined. Each sample was analyzed separately.
- 209-217: a lot of parameters were determined in the reservoir itself (that are not
described in the Results section, see below); were these parameters also determined in
the geothermal water sources? That would have been great in order to estimate the
amount of nutrient input fueling phytoplankton production.
The chemical parameters of geothermal waters have not been tested for the purposes of this study. Due to their social (angling) and natural role, the owner of the area (Bełchatów Mine) controls the quality and sanitary condition of the waters supplying tested reservoirs. Here we focus on the thermal factor.
- 220 – 224: please specify your statistical analyses – what were the response variables
tested, especially regarding zooplankton (abundances, biomass, diversity?), were these
tests repeated for each sampling event, were data pooled across all time points, or was
time included as a factor in the analysis? This does not become clear at all. Furthermore,
it would be useful to include additional analyses (see above). So far, the authors relate
their results exclusively to temperature, while it is well known that other abiotic factors
and of course food supply may have equal and also interactive effects on zooplankton
communities.
Statistical tests were performed on a set of "raw" data, i.e. the results from each separately analyzed sample. The variability of abundance and biomass, variability of zooplankton taxonomic diversity indices, and variability of water physical and chemical parameters were tested, and the differences between thermal classes are shown in Table 1.
- 225: Please specify what parameters you refer you - zooplankton ID based
abundances? sizes? functional groups?
The biomass values of each of the analyzed zooplankton taxa were compared between thermal classes (Tab. S1).
- 233: please specify “the parameters of the entire network”
Attributes of the entire network refers to its tendency to clustering, centralization, density, heterogeneity and paths lengths.
Results
- 1st paragraph: does mean annual temp. and mean winter temp. refer to the pooled data across all time points? Which time points were part of the “winter” samples? The authors state that “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp) (Table 1).” HOW did the reservoirs differ?? The authors should describe these differences and relate them to their zooplankton data, as phyto- and zooplankton is strongly influenced by a range of different abiotic parameters and not only by temperature (see also general comments).
Winter samples were for months of December–February.
The results of the physical and chemical parameters of water were elaborated in detail and presented in Table 1. Differences in average values were statistically compared. The authors repeatedly relate zooplankton data and the structure of zooplankton networks to abiotic conditions.
- 269-274: Correlations have not been mentioned in the methods section – the authors
should describe all of the analyses conducted. How was the effect of temperature on
zooplankton species richness tested? This is also not specified.
Added: Spearman's rank correlation analysis (p < 0.05) was used to test for correlations between temperature and zooplankton species richness, and between temperature and the others physical and chemical variables of water.
- 282 – 284: Were these analyses conducted across all seasons with all sampling time
points pooled? In general, pooling all data over time might level out important seasonal
dynamics, which are of utmost importance if the aim is to compare the food web dynamics in reservoirs differing in temporal (seasonal) thermal gradients (see above)
We understand that seasonal dynamics periodically change the structure of the food web. However, our goal was not to compare temporal variability across seasons. This concerns a different research topic. The data entered into the model concerned the entire analyzed season, which is consistent with the purpose and methodology of the study. Such an approach synthesizing intra-seasonal variability is needed to answer the question posed in the introduction, which concerned the comparison of entire seasons, not the dynamics within them. This is the approach found in the literature (Kruk et al., 2020, 2021; Goździejewska and Kruk 2022).
- 285 – 287: How was this tested? As the effect of temperature on single taxa? Or were the actual temperature differences calculated between different seasons?
The biomass of each taxon identified in each thermal class was calculated. The K-W test determined the significance of differences in the mean biomass of taxa between thermal classes.
- 326-327: again, the authors relate all differences solely to temperature without taking the other factors into account
Three interspecies zooplankton networks were built based on the main differentiating indicator, i.e. water temperature. On this basis, three thermal classes were determined. Hence, the differences in network attributes were related to thermal conditions. The influence and connection with other abiotic parameters is repeatedly emphasized in the Discussion section.
Discussion
- 363: what do the authors mean with the term “energy of water”? does the thermal
gradient refer to the temporal/seasonal gradient?
“Temperature is a physical factor that modifies flow and transformations of the biologically accumulated energy in the water…” This applies to every aspect of time, but here we compare the differentiated water thermals in the tested reservoirs.
- 364: which processes? Please specify
The processes described above in L140.
- 370: how do the authors come to that conclusion? Did they measure organic matter
recycling? I don’t really get the argumentation here – in the warmer reservoirs organic
matter cycling was already higher in winter due to the warm water inflow and did not
increase as much in spring as in the CW?
The rate of circulation of matter has not been studied. The researched reservoirs are shallow, polymictic. Therefore, there is homothermy in the reservoirs and equalization of oxygen concentration from the surface to the bottom. Due to the higher water temperature, mineralization of organic matter and its circulation in the winter period is faster in warmer reservoirs than in cold ones. The intensive mineralization of organic matter in WW is indicated by a significantly lower concentration of dissolved oxygen in water compared to CW and MW (Table 1). At the same time, nutrients available in water are used by macrophytes, which deposit them in their tissues. Thus, the increase in water temperature in spring has a much clearer effect on the activation of the above processes of circulation of elements in cooler reservoirs than in warmer reservoirs, where their resources are smaller.
- 373 – 376: Was that observed in the study in terms of lower Chl. a, or is this an
assumption? Wouldn't you assume that phytoplankton production increases more rapidly
in spring, when the water is already warmer? How were the reservoirs stratified – was
that somehow determined?
An increase in the concentration of chlorophyll a was observed along with the heating of water in the CW class. However, the chl a values did not change in the WW class. The reservoirs are shallow, and thermal and chemical stratification was not observed (methodology).
- 376-380: I don’t get this point - why would heating lead to less rapid cycling? I can
only imagine that under continuous recycling induced by warmer temperature, not as
much organic matter accumulates rapidly, leading to clearer water and thus more
macrophytes can establish?
Winter warming does not mean an increase in the circulation of matter within the plankton. On the other hand, it may contribute to its capture by macrophytes that find thermal conditions for development (Kruk et al. 2022). In addition, the observations are supported by studies by Wollrab et al. (2021).
- 380 – 382: Why? Because the delta of environmental change (temperature) is higher?
Please explain, this is hard to understand.
The mechanism of the influence of temperature on the feeding conditions of zooplankton in the studied reservoirs was explained above.
- 394: eutrophic conditions do not necessarily relate to good food conditions, as the
food quality is usually constrained under eutrophic conditions. The authors refer to the
nutrient concentrations measured in the reservoirs in the next sentence for the first time – these patterns need to be described in the Results section
We conclude about good nutritional conditions of CW based on the response of specific species (indicators of increased trophy). In the Results section, it was stated that the differences in "trophic" parameters were significant between the thermal classes and referred to Table 1
- 397 – 401: These results differ, but also the conditions investigated in the present
study are completely different than climate change scenarios (see above) – so please
specify the predictions you're referring to.
According to the answer L 150-151, we do not compare, but only propose to use in predicting global changes and their effects.
- 402-403: please explain, why would an increase in trophy levels (was that
observed?) contribute to a higher content of mineral suspensions?
These observations have been confirmed by many previous studies, also in the same reservoirs (please see references).
- 451-452: does this statement refer to the aforementioned study, or to the current
study?
To the current but also earlier by Goździejewska et al. 2018.
- 466-467: Why? Functionally diverse communities do not necessarily mean dynamic
zooplankton communities (dynamic over time?)
In this term, Dynamics means the dynamics (number and strength) of interspecies relationships mentioned above
- 474: what does immobilization refer to?
Immobilization of nutrients/organic matter in macrophyte tissues
- 487-489: This could also be an indication for an indirect effect of better water quality
characterized by less eutrophic conditions and fewer blooms of potentially inedible
phytoplankton.
Of course, such conditions prevailed there, as the results show (Tab.1)
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AC1: 'Reply on RC1', Anna Goździejewska, 07 Dec 2022
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RC2: 'Comment on egusphere-2022-794', Anonymous Referee #2, 07 Dec 2022
Authors aimed an important aspect of functioning of shallow reservoir ecosystems (three freshwater mine pit reservoirs) under the pressure imaging the global warming, showing the response of zooplankton network and presenting a new approach to examine zooplankton interspecific interactions with the use of the network graph analysis. The study presents interesting both, the dataset and analysis, but apart the temperature the other factors (cofactors) which can structure zooplankton network should also be analyzed and estimated, showing how much temperature and how much other factors (time, food, and other measured parameters, which were collected but not presented in analysis) are responsible for the observed zooplankton pattern. Seasonal changes should also be incorporated into such analysis, as this changes my increase or decrease the effect size. Several models (LMM – Linear Mixed Models including RM – Repeated Measure, NLMMs & GLMMS – Nonlinear and Generalized Linear Mixed Models) may work well in this case with fixed and random effect components. Sample size (20 L collected with the Patalas trap) sims to be correct, but collection of samples 1 m below the surface may underestimate especially the Copepoda group, but also Cladocera, both groups may be very abundant near the bottom (as examples please consult Bittel (1976), PapiÅska & Pijanowska (1980) and Klemetsen et al. (2020).
The Shannon’s diversity index was calculated with the stats software (MVSP 3.22), which calculate the index with its understanding for years before 1990s, which not allows for value comparison. Later, in the early 1990s, introduced was the rarefaction method for abundance standardization and proper comparison of Shannon’s diversity and species richness. For the proper Shannon’s index comparison and rarefaction calculation please consult free software like EstimateS or EcoSimR and Vegan R packages.
In the Results, Discussion and Conclusions – Authors explained all observed zooplankton differences exclusively by temperature, without showing the evidence of the lack of such influence of the other factors. In general, the Discussion should be rewritten (please avoid the speculations, just discuss the observed pattern and provide the “take-home message”).
The study is very valuable, based on the novel approach to examine of zooplankton structure, but due to all facts mention above I recommend this manuscript for publication after major revision.
Specific comments:
English through of the manuscript should be corrected, as an example, among others - Authors often have been using “in” in spite of “of” in many sentences.
The abstract should be rearranged. Before the hypothesis, please describe the state of the subject field knowledge, then characterize the research you did, hypothesis, the results and an info about conclusions.
Line 97-104: “Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces similar responses in freshwater zooplankton to accelerated eutrophication…” – awkward sentence.
Line 135: “biomass parameters” – delete “parameters” or specify what parameters of biomass were used.
Lines 150-156: since physical and chemical parameters (including temperature) are relatively stable – than all of them, not only temperature should structure zooplankton community and it is hard to say that the temperature was the main factor, other parameters (cofactors) should also be analyzed and then an influence of all factors should be estimated, and perhaps the temperature may be primarily responsible for estimated % of the effect size (in ecology we are looking for the effect size at least 20% or larger).
Line 196 – “the coastal zone” should be replaced with “littoral”, or “near shore zone” (as coastal refers exclusively to marine environments). Please explain “vicinity of the filter zone”.
Line 199 – the “experiment” – wrong use, this is a field study, not experiment.
Line 267: “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp)” – how this may affect observed zooplankton pattern?
Lines 272-284: how significant difference of species richness and Shannon’s diversity were estimated without abundance standardization and rarefaction?
Line 363 – please explain “energy of water”.
Line 375 – “less energy was generated” – awkward description, did you really measure the energy generation or just observed the lower/higher temperature of water?
Lines 530-532 – The conclusion about the role of Copepods is doubtful as the sampling procedure underestimated both, the abundance and species richness of this group.
References:
Bittel, L., 1976. Near-bottom plankton as a productive element in the lake ecosystem. Acta UNC, Limnological Papers 9:45-64.
Klemetsen, A., B. M. Aase & P. A. Amundsen, 2020. Diversity, abundance, and life histories of littoral chydorids (Cladocera: Chydoridae) in a subarctic European lake. Journal of Crustacean Biology 40(5):534-543 doi:10.1093/jcbiol/ruaa048.
PapiÅska, K. & J. Pijanowska, 1980. Pelagic and near-bottom crustaceans in five masurian Lakes. Ekologia polska 28:219-229.
Citation: https://doi.org/10.5194/egusphere-2022-794-RC2 -
AC2: 'Reply on RC2', Anna Goździejewska, 14 Dec 2022
Responses to reviewer's comments
Thank you for reading our work and appreciating its value. Thank you for the valuable tips and comments. Below we have included the answers and explanations for the given problems.
Seasonal changes should also be incorporated into such analysis, as this changes my increase or decrease the effect size.
We understand that seasonal dynamics periodically change the structure of the food web. However, our goal was not to compare temporal variability across seasons. This concerns a different research topic. The data entered into the model concerned the entire analyzed season, which is consistent with the purpose and methodology of the study. Such an approach synthesizing intra-seasonal variability is needed to answer the question posed in the introduction, which concerned the comparison of entire seasons, not the dynamics within them. This is the approach found in the literature (Kruk et al., 2020, 2021; Goździejewska and Kruk 2022).
Sample size (20 L collected with the Patalas trap) sims to be correct, but collection of samples 1 m below the surface may underestimate especially the Copepoda group, but also Cladocera, both groups may be very abundant near the bottom (as examples please consult Bittel (1976), Papińska & Pijanowska (1980) and Klemetsen et al. (2020).
The studied reservoirs are very shallow (⁓ 2 m), flow-through and mixed to the bottom (see Methods). Thus, the aerobic and thermal conditions are equal (no stratification). Thus, there is no significant variation in abiotic conditions that could affect the vertical distribution of crustaceans. In addition, it is also confirmed that bottom harpacticoids were often found in the zooplankton samples examined (Table S1). Harpacticoida are poor swimmers and their systematic presence in the water column is usually the result of wind mixing and mechanical resuspension with sediments (e.g. Goździejewska et al. 2006; http://www.ejpau.media.pl/volume9/issue2/art-16.html). Thus, we believe that due to the above factors (morphometry and abiotic factors), taxa of pelagic crustaceans (much better swimmers than Harpacticoida) are evenly distributed throughout the water column. Thus, in the studied reservoirs we find completely different environmental conditions than in the large and deep lakes referred to in the three proposed references.
The Shannon’s diversity index was calculated with the stats software (MVSP 3.22), which
calculate the index with its understanding for years before 1990s, which not allows for
value comparison. Later, in the early 1990s, introduced was the rarefaction method for
abundance standardization and proper comparison of Shannon’s diversity and species
richness. For the proper Shannon’s index comparison and rarefaction calculation please
consult free software like EstimateS or EcoSimR and Vegan R packages.
Thank you for pointing to other tools for calculating biodiversity. The results obtained at present are not and will not be compared in time and place. In this work, they are also not the main research problem. However, after reviewing the proposed packages, they will certainly be used in future research.
In the Results, Discussion and Conclusions – Authors explained all observed zooplankton
differences exclusively by temperature, without showing the evidence of the lack of such
influence of the other factors.
Three interspecies zooplankton networks were built based on the main differentiating indicator, i.e. water temperature. On this basis, three thermal classes were determined. Hence, the differences in network attributes were related to thermal conditions. The influence and connection with other abiotic parameters is repeatedly emphasized in the Discussion section.
In general, the Discussion should be rewritten (please avoid the speculations, just discuss the observed pattern and provide the “take-home message”).
Some changes have been made to the Discussion section. The discussion of each of the researched issues is based on a large set of relevant references, which are intended to prevent any speculation.
Specific comments:
English through of the manuscript should be corrected, as an example, among others -
Authors often have been using “in” in spite of “of” in many sentences.
English has been professional verified.
The abstract should be rearranged. Before the hypothesis, please describe the state of the subject field knowledge, then characterize the research you did, hypothesis, the results and an info about conclusions.
The volume of the abstract does not make it possible to describe the state of knowledge on the subject raised in the work. The relevant content is included in the Introduction. We believe that the sentence in which we present the hypothesis contains concise information about the work problem. Certain Abstract content will be re-written.
Line 97-104: “Previous research has demonstrated that an increase in mean
seasonal/annual water temperature induces similar responses in freshwater zooplankton
to accelerated eutrophication…” – awkward sentence.
Corrected to:
“Previous research has demonstrated that an increase in mean seasonal/annual water temperature induces responses in freshwater zooplankton similar to responses to accelerated eutrophication”
Line 135: “biomass parameters” – delete “parameters” or specify what parameters of
biomass were used. – corrected
Lines 150-156: since physical and chemical parameters (including temperature) are
relatively stable – than all of them, not only temperature should structure zooplankton
community and it is hard to say that the temperature was the main factor, other
parameters (cofactors) should also be analyzed and then an influence of all factors should be estimated, and perhaps the temperature may be primarily responsible for estimated % of the effect size (in ecology we are looking for the effect size at least 20% or larger). Line 267: “significant variations were also observed in DO, chlorophyll a, TOC, TN, and the parameters describing suspended solids (turbidity, color, SDT, Tot susp)” – how this may affect observed zooplankton pattern?
It is obvious that many biotic and abiotic factors determine the functioning of an aquatic ecosystem. Their interaction also shapes planktonic networks. In this study, the structure of the zooplankton network was related to temperature as the main factor differentiating the three studied reservoirs (thermal classes). We did not omit the probable impact of other measured parameters on zooplankton, providing their values and correlating them in the Results section and repeatedly emphasizing them in the Discussion section. In the Discussion, we tried to discuss every relationship between the zooplankton network results obtained and trophic conditions (here measured as Chla, organic matter, nutrients) and suspended solids conditions, based on the appropriate bibliographic database and previously published own results.
Line 196 – “the coastal zone” should be replaced with “littoral”, or “near shore zone” (as
coastal refers exclusively to marine environments). Please explain “vicinity of the filter
zone”.
Changed to „litoral zone” and added reference explaining „filter zone” (Goździejewska et al. 2018). For better explanation, what the filter zone is, please see the description in doi.org/10.1051/kmae/2018020
Line 199 – the “experiment” – wrong use, this is a field study, not experiment.
Changed to “field study”
Lines 272-284: how significant difference of species richness and Shannon’s diversity were estimated without abundance standardization and rarefaction?
Please see answer on biodiversity calculations, above.
Line 363 – please explain “energy of water”- corrected in the text to:
“Temperature is a physical factor that modifies flow and transformations of the energy in the water….
Line 375 – “less energy was generated” – awkward description, did you really measure the energy generation or just observed the lower/higher temperature of water?
Removed: “…less energy was generated”
Lines 530-532 – The conclusion about the role of Copepods is doubtful as the sampling
procedure underestimated both, the abundance and species richness of this group.
Please see the explanation above.
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AC2: 'Reply on RC2', Anna Goździejewska, 14 Dec 2022
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