Multi-platform study of the extreme bloom of the barrel jellyfish <em>Rhizostoma pulmo</em> (Cnidaria: Scyphozoa) in the northernmost gulf of the Mediterranean Sea (Gulf of Trieste) in April 2021

Reyes Suàrez, Nydia Catalina; Tirelli, Valentina; Ursella, Laura; Ličer, Matjaž; Celio, Massimo; Cardin, Vanessa

doi:https://doi.org/10.5194/egusphere-2022-393

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https://doi.org/10.5194/egusphere-2022-393

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31 May 2022

Multi-platform study of the extreme bloom of the barrel jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in the northernmost gulf of the Mediterranean Sea (Gulf of Trieste) in April 2021

Nydia Catalina Reyes Suàrez¹, Valentina Tirelli¹, Laura Ursella¹, Matjaž Ličer^2,3, Massimo Celio⁴, and Vanessa Cardin¹ Nydia Catalina Reyes Suàrez et al.

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¹National Institute of Oceanography and Applied Geophysics - OGS, Trieste, Italy
²Slovenian Environment Agency, Ljubljana, Slovenia
³National Institute of Biology, Marine Biology Station, Piran, Slovenia
⁴Regional Environmental Protection Agency of Friuli Venezia Giulia - FVG, Palmanova, Udine, Italy

Received: 24 May 2022 – Discussion started: 31 May 2022

Abstract. On 7 April 2021, an exceptional bloom of the scyphomedusa Rhizostoma pulmo was observed in the Gulf of Trieste (Italy). Blooms of this species in the northern Adriatic Sea have been reported since the late 1800s, however, the density of jellyfish observed in 2021 reached more than 10 specimens per square metre. In this work, we analyse the bloom from a multiplatform approach using observations and model data at different time scales. We attempt to explain the intensity of the bloom as a consequence of thermohaline and hydrodynamical conditions in the gulf. Meteo-oceanographic conditions that may have contributed to the exceptional aggregation of jellyfish observed along the northernmost coast of the Adriatic Sea are discussed in detail. Specifically, our results indicate that this bloom was enabled by 1) the presence of a high number of jellyfish in the Gulf probably linked to the anomalously warm sea conditions in spring 2020 and winter 2021 which may have favoured a longer reproductive period and enhanced survival of adult R. pulmo respectively; 2) strong wind events, such as the Bora wind for the Gulf of Trieste, which enhanced upwelling and mixing processes in the Gulf bringing the jellyfish from the deeper waters to the surface and clustering them along the coast.

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Journal article(s) based on this preprint

13 Sep 2022

Multi-platform study of the extreme bloom of the barrel jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in the northernmost gulf of the Mediterranean Sea (Gulf of Trieste) in April 2021

Nydia Catalina Reyes Suárez, Valentina Tirelli, Laura Ursella, Matjaž Ličer, Massimo Celio, and Vanessa Cardin

Ocean Sci., 18, 1321–1337, https://doi.org/10.5194/os-18-1321-2022,https://doi.org/10.5194/os-18-1321-2022, 2022

Short summary

Nydia Catalina Reyes Suàrez et al.

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-393', Anonymous Referee #1, 04 Jul 2022

The authors describe what was observed in spring 2021 in the Gulf of Trieste using different data sources. In this respect, the paper is rich in information and details.

My main remark is that the authors only took into account the 2021 event although a longer time series of jellyfish observations is available (Fig. 3). The 2021 event appears to be the most remarkable one because of its persistence, but other intense events occurred. For instance, in January 2020 a ‘3-degree’ event took place suddenly after weeks of weak or no jellyfish presence. Was that event connected with the atmospheric forcing in the same way as the 2021 one?

The analysis of the whole time series of fig. 3 also poses the question if it can be considered homogeneous. As observations are provided by citizens, the number of sightings might be influenced by previous observations: When a remarkable phenomenon is observed once, then many more people are stimulated to pay attention and report their own observation.

In any case, provided that in the specific event of 2021 things went as described in the paper, can the information be generalised on the basis of observations?

I recommend a major revision.

Minor points:

Line 59: Scirocco blows from SE (ESE-SSE), SSW is approximately Libeccio (SW); I suggest ‘warmer southerly wind blowing from SE to SSW directions’.

Lines 77-78: ‘… 2020). When the water column is stratified, the surface layer …’.

Lines 112, 126, 127: What is ‘pi:’?

Lines 113-119: Are the CTD and hydrometer data publicly available?

Line 123: I suggest to replace the ‘=’ character with ‘corresponds to’, otherwise it is misleading. Please define ‘ind’ (individuals?). According to the definition, 1 ind m^-2 is both included in case 1 and case 2. The same occurs in fig. 3 (page 8). Please solve the ambiguity.

Line 131: Please define ‘L1’ (layer 1?).

Lines 132-134: ‘Model and reanalysis data were used …’. How big were the gaps in the observations?

Line 164: Please describe how the RMSE is normalised.

Table 2 (page 9): Please outline the meaning of ‘corr-u’, ‘corr-v’ and ‘corr-sp’ in the caption.

Lines 176-177: Please note that the variables used for the statistics have a non-normal distribution. The authors should explain how correlation was computed and how significant the results are. ‘Fairly good’ does not mean much.

Line 179: Here there is ‘0.5540’ but in Table 2 it is ‘0.4633’. Please check.

Line 181 and 187: ‘wind speed’ (m s^-1) not ‘wind intensity’.

Line 212: There are different responses of the sea to wind forcing. For instance, surface cooling near the eastern coast in case of Bora requires just a few hours. Please clarify.

Line 213: ‘occupied’ instead of ‘filled’.

Figure 6 (page 12): The moving-average curve within the data gap has no meaning; please delete it.

Fig. 7 (page 13): ‘left black dashed line’ and ‘right black dashed line’.

Line 239: ‘north Adriatic Sea’.

Lines 243-244: Also –200 is <50. Do the authors mean ‘from –200 to approximately +50 W m^-2’? Please rephrase. Also, 50% of what? See also previous comment.

Citation: https://doi.org/10.5194/egusphere-2022-393-RC1
- AC2: 'Reply on RC1', Nydia Catalina Reyes Suarez, 22 Jul 2022
  
  Dear reviwer1,
  We would like to thank your constructive observations. We have rearranged the manuscript considering the reviewer’s comments. Please find in the attachment point-by-point responses your comments.
  
  Citation: https://doi.org/10.5194/egusphere-2022-393-AC2
RC2:
'Comment on egusphere-2022-393', Anonymous Referee #2, 05 Jul 2022

In general, the scientific significance of the paper submitted by Reyes-Suárez et al. to EGUSPHERE is excellent (1). The manuscript represents a substantial contribution to scientific progress within the scope of Ocean Science regarding the population dynamics of the jellyfish in the Gulf of Trieste, linking the biology of this organism with different oceanographic and meteorologic features that characterize the area.

Moreover, the scientific quality is also of the same level that the scientific significance (1), due to the fact that the scientific approach and applied methods are valid. The results are discussed in an appropriate and balanced way, taking into account the consideration of related work and including appropriate references.

In general, again, few times a first version of a manuscript has such a high presentation quality (1). The scientific results and conclusions are presented in a clear, concise, and well-structured way, being the number and quality of figures/tables good. The appropriate use of English language I will not give a score as it is not my mother language.

Detail comments:

Line 109: a space is need after “al.”

Line 132: a space is need before “Data”

Table 2: In the legend or in the head table itself should be detailed that “sp” corresponds to “speed”

Line 255: a space is need before “The”

Line 263: spaces are need after “C” of the mentioned temperatures

Figure 10d: the rest of the plots in this figure, the “y axis” are well representing the range, but in the case of the Autumn, my opinion is that the authors could short the range. I understand that in the other 3 plots always a range of 10 degrees are used.

Citation: https://doi.org/10.5194/egusphere-2022-393-RC2
- AC1: 'Reply on RC2', Nydia Catalina Reyes Suarez, 22 Jul 2022
  
  In general, the scientific significance of the paper submitted by Reyes-Suárez et al. to EGUSPHERE is excellent (1). The manuscript represents a substantial contribution to scientific progress within the scope of Ocean Science regarding the population dynamics of the jellyfish Rhizostoma pulmo in the Gulf of Trieste, linking the biology of this organism with different oceanographic and meteorologic features that characterize the area.
  Moreover, the scientific quality is also of the same level that the scientific significance (1), due to the fact that the scientific approach and applied methods are valid. The results are discussed in an appropriate and balanced way, taking into account the consideration of related work and including appropriate references.
  In general, again, few times a first version of a manuscript has such a high presentation quality (1). The scientific results and conclusions are presented in a clear, concise, and well-structured way, being the number and quality of figures/tables good. The appropriate use of English language I will not give a score as it is not my mother language.
  First, we would like to thank anonymous reviewer 2 for her/his useful and constructive remarks and kind comments on our manuscript. All requested revisions were incorporated into the revised version of the manuscript. Responses to the reviewer's comments and changes in the manuscript are reproduced below in bold font.
  
  Detail comments:
  
  Line 109: a space is need after “al.”
  The sentence has been rearranged. Please see lines 110 in the revised version of the manuscript.
  
  Line 132: a space is need before “Data”
  The space has been added. Please see line 134 in the revised version of the manuscript.
  
  Table 2: In the legend or in the head table itself should be detailed that “sp” corresponds to “speed”
  The legend in Table 2 has been modified and abbreviations have been added.
  
  Line 255: a space is need before “The”
  Amended
  
  Line 263: spaces are need after “C” of the mentioned temperatures
  Done
  
  Figure 10d: the rest of the plots in this figure, the “y axis” are well representing the range, but in the case of the Autumn, my opinion is that the authors could short the range. I understand that in the other 3 plots always a range of 10 degrees are used.
  We understand the reviewer's point, but to facilitate comparison between the seasons (Figure 11 a, b, and c in the revised manuscript), we would prefer to leave this figure as it is.
  
  Citation: https://doi.org/10.5194/egusphere-2022-393-AC1

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2022-393', Anonymous Referee #1, 04 Jul 2022

The authors describe what was observed in spring 2021 in the Gulf of Trieste using different data sources. In this respect, the paper is rich in information and details.

My main remark is that the authors only took into account the 2021 event although a longer time series of jellyfish observations is available (Fig. 3). The 2021 event appears to be the most remarkable one because of its persistence, but other intense events occurred. For instance, in January 2020 a ‘3-degree’ event took place suddenly after weeks of weak or no jellyfish presence. Was that event connected with the atmospheric forcing in the same way as the 2021 one?

The analysis of the whole time series of fig. 3 also poses the question if it can be considered homogeneous. As observations are provided by citizens, the number of sightings might be influenced by previous observations: When a remarkable phenomenon is observed once, then many more people are stimulated to pay attention and report their own observation.

In any case, provided that in the specific event of 2021 things went as described in the paper, can the information be generalised on the basis of observations?

I recommend a major revision.

Minor points:

Line 59: Scirocco blows from SE (ESE-SSE), SSW is approximately Libeccio (SW); I suggest ‘warmer southerly wind blowing from SE to SSW directions’.

Lines 77-78: ‘… 2020). When the water column is stratified, the surface layer …’.

Lines 112, 126, 127: What is ‘pi:’?

Lines 113-119: Are the CTD and hydrometer data publicly available?

Line 123: I suggest to replace the ‘=’ character with ‘corresponds to’, otherwise it is misleading. Please define ‘ind’ (individuals?). According to the definition, 1 ind m^-2 is both included in case 1 and case 2. The same occurs in fig. 3 (page 8). Please solve the ambiguity.

Line 131: Please define ‘L1’ (layer 1?).

Lines 132-134: ‘Model and reanalysis data were used …’. How big were the gaps in the observations?

Line 164: Please describe how the RMSE is normalised.

Table 2 (page 9): Please outline the meaning of ‘corr-u’, ‘corr-v’ and ‘corr-sp’ in the caption.

Lines 176-177: Please note that the variables used for the statistics have a non-normal distribution. The authors should explain how correlation was computed and how significant the results are. ‘Fairly good’ does not mean much.

Line 179: Here there is ‘0.5540’ but in Table 2 it is ‘0.4633’. Please check.

Line 181 and 187: ‘wind speed’ (m s^-1) not ‘wind intensity’.

Line 212: There are different responses of the sea to wind forcing. For instance, surface cooling near the eastern coast in case of Bora requires just a few hours. Please clarify.

Line 213: ‘occupied’ instead of ‘filled’.

Figure 6 (page 12): The moving-average curve within the data gap has no meaning; please delete it.

Fig. 7 (page 13): ‘left black dashed line’ and ‘right black dashed line’.

Line 239: ‘north Adriatic Sea’.

Lines 243-244: Also –200 is <50. Do the authors mean ‘from –200 to approximately +50 W m^-2’? Please rephrase. Also, 50% of what? See also previous comment.

Citation: https://doi.org/10.5194/egusphere-2022-393-RC1
- AC2: 'Reply on RC1', Nydia Catalina Reyes Suarez, 22 Jul 2022
  
  Dear reviwer1,
  We would like to thank your constructive observations. We have rearranged the manuscript considering the reviewer’s comments. Please find in the attachment point-by-point responses your comments.
  
  Citation: https://doi.org/10.5194/egusphere-2022-393-AC2
RC2:
'Comment on egusphere-2022-393', Anonymous Referee #2, 05 Jul 2022

In general, the scientific significance of the paper submitted by Reyes-Suárez et al. to EGUSPHERE is excellent (1). The manuscript represents a substantial contribution to scientific progress within the scope of Ocean Science regarding the population dynamics of the jellyfish in the Gulf of Trieste, linking the biology of this organism with different oceanographic and meteorologic features that characterize the area.

Moreover, the scientific quality is also of the same level that the scientific significance (1), due to the fact that the scientific approach and applied methods are valid. The results are discussed in an appropriate and balanced way, taking into account the consideration of related work and including appropriate references.

In general, again, few times a first version of a manuscript has such a high presentation quality (1). The scientific results and conclusions are presented in a clear, concise, and well-structured way, being the number and quality of figures/tables good. The appropriate use of English language I will not give a score as it is not my mother language.

Detail comments:

Line 109: a space is need after “al.”

Line 132: a space is need before “Data”

Table 2: In the legend or in the head table itself should be detailed that “sp” corresponds to “speed”

Line 255: a space is need before “The”

Line 263: spaces are need after “C” of the mentioned temperatures

Figure 10d: the rest of the plots in this figure, the “y axis” are well representing the range, but in the case of the Autumn, my opinion is that the authors could short the range. I understand that in the other 3 plots always a range of 10 degrees are used.

Citation: https://doi.org/10.5194/egusphere-2022-393-RC2
- AC1: 'Reply on RC2', Nydia Catalina Reyes Suarez, 22 Jul 2022
  
  In general, the scientific significance of the paper submitted by Reyes-Suárez et al. to EGUSPHERE is excellent (1). The manuscript represents a substantial contribution to scientific progress within the scope of Ocean Science regarding the population dynamics of the jellyfish Rhizostoma pulmo in the Gulf of Trieste, linking the biology of this organism with different oceanographic and meteorologic features that characterize the area.
  Moreover, the scientific quality is also of the same level that the scientific significance (1), due to the fact that the scientific approach and applied methods are valid. The results are discussed in an appropriate and balanced way, taking into account the consideration of related work and including appropriate references.
  In general, again, few times a first version of a manuscript has such a high presentation quality (1). The scientific results and conclusions are presented in a clear, concise, and well-structured way, being the number and quality of figures/tables good. The appropriate use of English language I will not give a score as it is not my mother language.
  First, we would like to thank anonymous reviewer 2 for her/his useful and constructive remarks and kind comments on our manuscript. All requested revisions were incorporated into the revised version of the manuscript. Responses to the reviewer's comments and changes in the manuscript are reproduced below in bold font.
  
  Detail comments:
  
  Line 109: a space is need after “al.”
  The sentence has been rearranged. Please see lines 110 in the revised version of the manuscript.
  
  Line 132: a space is need before “Data”
  The space has been added. Please see line 134 in the revised version of the manuscript.
  
  Table 2: In the legend or in the head table itself should be detailed that “sp” corresponds to “speed”
  The legend in Table 2 has been modified and abbreviations have been added.
  
  Line 255: a space is need before “The”
  Amended
  
  Line 263: spaces are need after “C” of the mentioned temperatures
  Done
  
  Figure 10d: the rest of the plots in this figure, the “y axis” are well representing the range, but in the case of the Autumn, my opinion is that the authors could short the range. I understand that in the other 3 plots always a range of 10 degrees are used.
  We understand the reviewer's point, but to facilitate comparison between the seasons (Figure 11 a, b, and c in the revised manuscript), we would prefer to leave this figure as it is.
  
  Citation: https://doi.org/10.5194/egusphere-2022-393-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Nydia Catalina Reyes Suarez on behalf of the Authors (04 Aug 2022) Author's response Author's tracked changes Manuscript

ED: Publish subject to minor revisions (review by editor) (08 Aug 2022) by Mario Hoppema

Dear Dr. Reyes-Suàrez and co-authors,

Thank you for the revision of your manuscript. I am generally satisfied with your response and with the changes in the manuscript. After reading the manuscript myself, I have listed some minor comments below. Please prepare your final revision accounting for my comments, after which the manuscript can be published in Ocean Science.

As to the data downloaded or obtained from other sources: Please check again if the data originators request a particular acknowledging of data use. If this be the case, please add this.

L2 delete: however ; There are no data from the late 1800s on to show that the 10 spec/m2 is extremely high, so “however” is not appropriate here.

L3 delete: In this work

Figure 2 Please enter all geographical names to the figure used in the text. Most are certainly in the figure, but Istrian coast and Grado, for example are not.

L85 delete: were considered to ; either the data characterize this period (which means they are exactly from this period) or not.

L92 and further whole Sect 3.1 Please give an indication of the errors of all data used

L121-126 Using citizen science data is great but there is a risk of non-representativeness. The least you can do is scale to the number of observations. If there are many observations, the chance that a high number of individuals will be observed is greater. The data are shown in Fig. 3. I think you should also show that the number of individuals is highest while accounting for the number of observations.

L170 define max-min difference (or write out full)
L170 magnitude instead of: measure?
L170 define NRMSE as this has not been done before (e.g., normalized RMSE)

L172 SSC instead of SCC (typo)

Caption Table 2: “Comparison statistics between observed and model time series.” Please mention that it concerns correlation coefficients in this first sentence.
Table 2: Please provide the sample number (n) and whether the correlations are statistically significant.

Figure 7 There is no red line and moving average in the figure, as mentioned in the caption.

L227-228 please add when the online page was visited.
L318 … due to redistribution or redistribution of a … (redistribution twice; please correct what you mean here)

L320-326 First you argue that you observed a “true” bloom. However, the role of the Bora in the blooming event really seems to point to an “apparent bloom”, I think. Actually, the arguing in the following paragraph reads like the description of an apparent bloom. Please comment on this.

L426 After the last author of the list there are some strange symbols
L463-465 This reference does not seem to be complete
L469 This reference does not seem to be complete

Thanks and best wishes
Mario Hoppema

Hide

AR by Nydia Catalina Reyes Suarez on behalf of the Authors (09 Aug 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (10 Aug 2022) by Mario Hoppema

Journal article(s) based on this preprint

13 Sep 2022

Multi-platform study of the extreme bloom of the barrel jellyfish Rhizostoma pulmo (Cnidaria: Scyphozoa) in the northernmost gulf of the Mediterranean Sea (Gulf of Trieste) in April 2021

Nydia Catalina Reyes Suárez, Valentina Tirelli, Laura Ursella, Matjaž Ličer, Massimo Celio, and Vanessa Cardin

Ocean Sci., 18, 1321–1337, https://doi.org/10.5194/os-18-1321-2022,https://doi.org/10.5194/os-18-1321-2022, 2022

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Nydia Catalina Reyes Suàrez et al.

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On 7 April 2021, an exceptional bloom of barrel jellyfish was observed in the Gulf of Trieste (Italy), where the observed density reached more than 10 jellyfish per square metre. In this paper, we analyse the bloom using observations and model data to try to explain the intensity of the bloom as a consequence of oceanographic conditions in the gulf and how these may have contributed to the exceptional jellyfish aggregation observed.


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