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Translating crustacean biological responses from CO2 bubbling experiments into population-level predictions
Citation:
Grear, J. Translating crustacean biological responses from CO2 bubbling experiments into population-level predictions. Population Ecology. Springer International Publishing AG, Cham (ZG), Switzerland, 58(4):515-524, (2016).
Impact/Purpose:
This manuscript addresses a key methodological gap in the interpretation of biological response experiments that have previously documented effects of pCO2 manipulation on aquatic organisms. Addressing this gap strengthens the scientific basis of any future efforts that may be needed for developing water quality criteria that are responsive to the effects of ocean and coastal acidification on aquatic life in situ.
Description:
Many studies of animal responses to ocean acidification focus on uniformly conditioned age cohorts that lack complexities typically found in wild populations. These studies have become the primary data source for predicting higher level ecological effects, but the roles of intraspecific interactions in re-shaping biological, demographic and evolutionary responses are not commonly considered. To explore this problem, I assessed responses in the mysid Americamysis bahia to bubbling of CO2-enriched and un-enriched air into the seawater supply in flow-through aquariums. I conducted one experiment using isolated age cohorts and a separate experiment using intact populations. The seawater supply was continuously input from Narragansett Bay (Rhode Island, USA). The 28-day cohort study was maintained without resource or spatial limitations, whereas the 5-month population study consisted of stage-structured populations that were allowed to self-regulate. These differences are common features of experiments and were intentionally retained to demonstrate the effect of methodological approaches on perceptions of effect mechanisms. The CO2 treatment reduced neonate abundance in the cohort experiment (24% reduction due to a mean pH difference of −0.27) but not in the population experiment, where effects were small and were strongest for adult and stage 1 survival (3% change due to a mean pH difference of −0.25). I also found evidence of competition in the population experiment, further complicating relationships with cohort experiments. These results point to limitations of standard cohort tests. Such experiments should be complimented by studies of intact populations where responses may be affected by evolution, acclimation, and competition.
