the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The Clam Before the Storm: A Meta Analysis Showing the Effect of Combined Climate Change Stressors on Bivalves
Rachel A. Kruft Welton
Daniela N. Schmidt
James D. Witts
Benjamin C. Moon
Abstract. Impacts of a range of climate change on marine organisms have been analysed in laboratory and experimental studies. The use of different taxonomic groupings, and assessment of different processes, though, makes identifying overall trends challenging, and may mask phylogenetically different responses. Bivalve molluscs are an ecologically and economically important data-rich clade, allowing for assessment of individual vulnerability and across developmental stages. We use meta-analysis of 203 unique experimental setups to examine how bivalve growth rates respond to increased water temperature, acidity, deoxygenation, changes to salinity, and combinations of these drivers. Results show that anthropogenic climate change will affect different families of bivalves disproportionally but almost unanimously negatively. Almost all drivers and their combinations have significant negative effects on growth. Combined deoxygenation, acidification, and temperature shows the largest negative effect size. Eggs/larval bivalves are more vulnerable overall than either juveniles or adults. Infaunal taxa, including Tellinidae and Veneridae, appear more resistant to warming and oxygen reduction than epifaunal or free-swimming taxa but this assessment is based on a small number of datapoints. The current focus of experimental set-ups on commercially important taxa and families within a small range of habitats creates gaps in understanding of global impacts on these economically important foundation organisms.
Rachel A. Kruft Welton et al.
Status: open (until 24 Apr 2023)
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RC1: 'Comment on egusphere-2023-287', Lisa Levin, 28 Mar 2023
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This is a valuable, well-written meta analysis of climate change impacts on bivalves, focusing largely on experimental work.  The authors do a good job of explaining what is new about their work - illustrating differential responses at the family-level, among life stages and lifestyles, complexity of responses, and revealing biases in study taxa.  There is thoughtful discussion of life stage differences, mechanisms underlying impacts, and implications for aquaculture, fisheries, conservation and restoration.  For those not working with bivalves, it might be interesting for the authors to speculate in the discussion which of their findings might be general across classes (or phyla) , and which might be specific to bivalves (or possibly other calcifying taxa) and why.
It took me a while to find the link to the 79 articles used in the analysis.  Perhaps indicate this earlier in the methods.  I could not find the original data derived from these articles that formed the basis of the analysis. These should be provided to the reader as a supplement or separate database. I think this is standard practice for this type of work.
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Below are comments, questions and suggestions intended to strengthen the presentation.
Introduction
Line 25-32. These average environmental changes do not really tell the whole story since the regional variability is huge (e.g. some areas have lost 40% of their oxygen).
Methods – It is hard from the text to evaluate what magnitude of stressors were applied (under specific RCP or SSP scenarios?) Were studies limited to coastal species? Perhaps provide a species list - or did I miss this?
Line 90  By selecting one trait (growth) but not including survivorship – how many studies were excluded? There are a number of papers that might have contributed to this study if survivorship were addressed.   I recognize growth is sublethal and the survivorship is lethal ; would you expect results to be very different?
Line 100 Why was deoxygenation not a search term? Did this come up under oxygen or not?
Line 131 preformed or performed?
Natural variability in seawater associated with diel cycles, upwelling/seasonality , respiration as well as warming effects on gas solubility causes stressors to change together.  So warmer temperatures are usually associated with lower oxygen, nighttime respiration draws down pH and O2 together – etc.  Thus bivalves would be expected to be adapted to related changes. Perhaps discuss how this does or does not manifest in your results?
Line 187-88  The results are stated to be unexpected. This means that there were specific expectations. Could these be presented as hypotheses? Is it the different responses among families that were unexpected? Or the contrasting response to combinations of treatments?
This is stylistic – but for sentences where you give the statistical result at the start of the sentence and the scientific meaning at the end of the sentence – I suggest reversing these and leading with the science, which is what the reader cares most about (e.g., lines 204-208).Â
Line 307 – typo in via
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Citation: https://doi.org/10.5194/egusphere-2023-287-RC1
Rachel A. Kruft Welton et al.
Rachel A. Kruft Welton et al.
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