Extrapolating Contaminant Effects from Individuals to Populations: A Case Study on Nanoparticle Toxicity to Daphnia Fed Environmentally Relevant Food Levels

Ecological risk assessment (ERA) is charged with assessing the likelihood a chemical will have adverse environmental or ecological effects. When assessing the risk of a potential contaminant to biological organisms, ecologists are most concerned with the sustainability of populations of organisms, r...

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Bibliographic Details
Published in:Archives of environmental contamination and toxicology 2022-11, Vol.83 (4), p.361-375
Main Authors: Stevenson, Louise M., Krattenmaker, Katherine E., McCauley, Edward, Nisbet, Roger M.
Format: Article
Language:English
Subjects:
Contaminants
Earth and Environmental Science
Ecological effects
Ecological risk assessment
Ecotoxicology
Environment
Environmental Chemistry
Environmental Health
Environmental risk
ENVIRONMENTAL SCIENCES
Estimates
Exposure
Extinction
Extrapolation
Food
Growth rate
Monitoring/Environmental Analysis
Nanoparticles
Pollution
Population
Population growth
Population studies
Risk assessment
Silver
Soil Science & Conservation
Sustainability
Toxicity
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Summary:Ecological risk assessment (ERA) is charged with assessing the likelihood a chemical will have adverse environmental or ecological effects. When assessing the risk of a potential contaminant to biological organisms, ecologists are most concerned with the sustainability of populations of organisms, rather than protecting every individual . However, ERA most commonly relies on data on the effect of a potential contaminant on individuals because these experiments are more feasible than costly population-level exposures. In this work, we address the challenge of extrapolating these individual-level results to predict population-level effects. Previous per-capita population growth rate estimates calculated from individual-level exposures of Daphnia pulicaria to silver nanoparticles (AgNPs) at different food rations predict a critical daily food requirement for daphnid populations exposed to 200 μg/L AgNPs to avoid extinction. To test this, we exposed daphnid populations to the same AgNP concentration at three different food inputs, with the lowest ration close to the extinction threshold predicted from data on individuals. The two populations with the higher food inputs persisted, and the population with the lowest food input went extinct after 50 days but did persist through two generations. We demonstrate that we can extrapolate between these levels of biological organization by parameterizing an individual-level biomass model with data on individuals’ response to AgNPs and using these parameters to predict the outcome for control and AgNP-exposed populations. Key to successful extrapolation is careful modeling of temporal changes in resource density, driven by both the experimental protocols and feedback from the consumer. The implication for ecotoxicology is that estimates of extinction thresholds based on studies of individuals may be reliable predictors of population outcomes, but only with careful treatment of resource dynamics.
ISSN:0090-4341
1432-0703
DOI:10.1007/s00244-022-00950-7