| 23 Jun 2026
A 3,000-yr lacustrine record of climate and environmental change and their influence on aquatic communities from Andean Puna lakes
Abstract. High Mountain Lakes in the Central Andean Altiplano experienced significant fluctuations in water levels during the Late Quaternary, which have affected the composition of aquatic communities. In this study, Casiri Hembra and Casiri Macho Lakes (Northern Chile, > 4,800 m a.s.l.) sediment cores were obtained and analyzed by combination of different proxies: analyses of geochemistry, magnetic properties, and pollen assemblage, joint to ecological proxies, such as the structure of benthic macroinvertebrates, to identify environmental changes that occurred in the Altiplano region during the late Holocene, with particular emphasis on distinguishing local influences from broader regional processes and their impacts on aquatic community structure and surrounding vegetation of these isolated high-mountain lakes. Results showed a progressive change in depositional dynamics from the Late Holocene to the present, 900 years in Casiri Hembra Lake, and over 3,000 years in Casiri Macho Lake. Older sediments show a general dominance of fine-grained sediments, with episodes suggesting the influence of high-energy clastic inputs, likely reflecting episodic flooding or increased basin runoff. Recent deposits indicate the development of low-energy lacustrine conditions, increased productivity, and reduced terrigenous input. Volcanic activity of the surrounding complex was recorded. The aquatic community of Casiri Lakes shows a significant replacement of taxa, from Ostracoda and Diptera in older sediments to Anostraca Crustacea in the most recent sediments. In addition, the presence of local microhabitats for the observed community is noted. High sedimentation rates in Casiri Lakes suggest complementary depositional sources to authigenic processes, such as sustained atmospheric deposition, which likely represents a significant contribution to the sediment budget.
This ms presents peleoenvironmental changes from two sediment cores collected in high mountain lakes of the Central Andean Altiplano in Chile. Changes in water level are reconstructed from multiproxy analyses (geochemistry, magnetic properties, pollen assemblages, benthic macroinvertebrates). Chronology was obtained from radiocarbon dating with 4 measures for the first lake dated to 900 cal BP and 6 measures for the second lake dated to 3000 cal BP. Results show phases of increased basin run off and low terrigeneous input while an increase in sedimentation rate suggests additional sources like aeolian deposits on the first core shown by change in magnetic susceptibility.
The data presented by the authors are rare, located in a remote area, and of excellent quality. However, I regret that the authors limit themselves to the data without delving into the explanations that would allow for a better understanding of the significance of the changes described. Furthermore, the scientific question justifying this work is not clearly formulated.
For example, it is not clearly established when the wetter phase, the drier phase, and the phase involving aeolian inputs occur, which makes understanding the situation as a whole very complex.Furthermore, we lack all the information that would enable us to understand the modern environment and depositional conditions of these lakes.
Below, you will find some detailed comments—which I hope are constructive—intended to help the authors revise the manuscript.
ABSTRACT
-The abstract is very factual and lacks detail in the presentation of the results (e.g., the chronology).-The results of the pollen analyses are not mentioned.-Finally, it is unclear whether the observations align with those recorded at a more regional scale.
MATERIAL AND METHODSAmong the elements I most lacked in approaching this work, one might cite:descriptions of the vegetation and pollen assemblages—in conjunction with pollen-vegetation calibration studies—, information on the region's climate, and a discussion of the chronological and spatial context of the area or its immediate surroundings.
RESULTS
Furthermore, I regret that the geochemical results—which lie at the heart of this study—are presented in a conventional format, without using better practices for the processing and interpretation of bulk inorganic geochemical data. Log-ratio transformation is essential for the rigorous statistical analysis of geochemical datasets. Furthermore, an accurate interpretation of inorganic geochemical data requires a sound understanding of the sediment's main constituents (organic matter, biogenic silica, carbonates, lithogenic particles) as well as its mineralogical assemblages.
See for instance Bertrand, S., Tjallingii, R., Kylander, M. E., Wilhelm, B., Roberts, S. J., Arnaud, F., et al.: Inorganic geochemistry of Lake sediments: A review of analytical techniques and guidelines for data interpretation, Earth-Science Reviews, 249, 104639, doi.org/10.1016/j.earscirev.2023.104639, 2024.
Above all, we need a single synthetic figure showing the main results of the multiproxy analyses (geochemistry, pollen, benthic macro invertebrates), a table with information on the radiocarbon dates: laboratory where the measures were performed, lab number, sample depth, C14 dates, calibrated ages.
MISCELLANEOUS
-The description of the geochemical results is too long.
-The pollen diagram does not show any pollen zones why?
In addition, it is extremely difficult to follow the results without references to pollen calibration and vegetation physiognomies of the study area.
Discussion:
-The discussion is very difficult to follow. -Indicate the regional and local phases of the observed changes, clearly specifying the depth and age, and represent them in a figure.
-To which period do the episodes suggesting the influence of high-energy clastic input correspond? (line 379)
Line 382: What is the duration of the event? What is the thickness of the associated sediments?-Where is it located on your figures?-When did the aeolian deposit form? What are the hypotheses explaining its origin?
-What are the main changes observed in the study area? When?
-Show on a map the location of the records discussed in the text