2018 Progress Report: A Bioenergetics-Based Approach to Understanding and Predicting Individual- to Community-Level Ecological Effects of Manufactured Chemicals

EPA Grant Number: R835800
Title: A Bioenergetics-Based Approach to Understanding and Predicting Individual- to Community-Level Ecological Effects of Manufactured Chemicals
Investigators: J. Salice, Christopher
Institution: Towson University
EPA Project Officer: Lasat, Mitch
Project Period: September 1, 2015 through August 31, 2018 (Extended to February 28, 2020)
Project Period Covered by this Report: January 1, 2018 through December 15,2018
Project Amount: $374,510
RFA: Systems-Based Research for Evaluating Ecological Impacts of Manufactured Chemicals (2014) RFA Text |  Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems , Safer Chemicals

Objective:

Objective: A fundamental goal in ecotoxicology and ecological risk assessment (ERA) is to predict the frequency and magnitude of adverse ecological effects resulting from chemical contaminants. While there is a considerable volume of research generated on the effects of a wide variety of manufactured chemicals on ecologically relevant receptors, the vast majority of studies are focused at levels of biological organization that are most conducive to empirical approaches – the individual and lower. Paradoxically, the levels of biological organization that are most relevant to environmental health and societal value are at the population level and higher (communities and ecosystems). The overarching objective of the proposed research is to develop a bioenergetics-based Adverse Outcome Pathway framework that can translate from individual-level to population- and community-level effects of manufactured chemicals.

Progress Summary:

Specific Aim 1: Establish bioenergetics-based responses and associated mathematical models (e.g., Dynamic Energy Budget (DEB), Von Bertelanffy growth model) of individual study species exposed to PFOS and pyraclostrobin for 2-4 week exposures, which are representative of relatively low-cost, standardized toxicity tests.

Endpoints: Life history traits, cellular energy assimilation, metabolic rate, feeding rate, fatty acid profiles – growth rate as a key endpoint

Models: Single species bioenergetics (DEB) and growth models

Summary Specific Aim 1 Progress: We have successfully conducted a series of relatively short duration toxicity studies to explore the effects of pyraclostrobin, perfluooctane sulfonate (PFOS), and NaCl on Daphnia magna and/or Lymnaea stagnalis. Our research has shown that pyraclostrobin is more toxic than PFOS and NaCl and we have what we think is a well-developed understanding of pyraclostrobin toxicity to our aquatic test species. After extensive toxicity testing in both L. stagnalis and D. magna, the more relevant exposure and effect scenario for pyraclostrobin appears to be related to short duration, acute toxicity. Alternatively, chronic exposure to NaCl appears very relevant and to exert toxicity to D. magna (but not L. stagnalis). Current efforts are aimed at exploring the interactive effects of pyraclostrobin and NaCl in D. magna.

As mentioned, PFOS is less toxic than pyraclostrobin but interestingly appears to exert toxicity in subtle ways and after long duration exposures. As an example, PFOS increased the variability in population size in Daphnia which then translates to an increase in extinction risk. These results were obtained from a novel study design that we developed where cohorts of daphnia are exposed and the laboratory populations are followed through time. This method yields insights into effects of chemicals on population dynamics and implicitly include density dependent.

Additionally, we have explored the impact of the resource environment on toxicity and have generated some very interesting and somewhat counterintuitive results. Two papers on this subject have been published with a third in draft. Moreover, we have conducted a series of acute toxicity studies with Daphnia and pyraclostrobin over a series of resource levels and have shown that as resource levels increase, pyraclostrobin toxicity decreases..

We have measured lipid profiles as a bioenergetics endpoint in Daphnia under different food regimes. Additionally, we have measured lipid, carbohydrate, and protein content in chironomids from streams representing an urban (stressed) to rural (less stressed) environment. The data convincingly show a positive correlation between the energetic environment (carbon in silt/clay) and total energy content in caddisflies. We acquired the means to measure metabolic rate in small organisms (Daphnia) and our preliminary studies show that exposure to pyraclostrobin appears to cause an increase in metabolic rate which preliminarily confirms our hypothesis.

Specific Aim 2: Establish bioenergetics-based responses, life-history effects and population-level effects of individual study species exposed to PFOS and pyraclostrobin using a Life Table Response Experiment study design (full life cycle exposure).

Endpoints: Same as Specific Aim 1 plus population-level endpoints (population growth rate, estimated abundance, stable stage distribution)

Models: Individual-based and cohort-based population models

Summary Specific Aim 2 Progress: Full life-cycle, cohort-based study designs for Daphnia have now become a staple of our laboratory studies. This design involves initiating a laboratory population with a few individuals and allowing them to grow and reproduce with no culling for at least 40 days. This yields a very predictable population cycle of growth, peak, decline and stable phases. We have used this design to test toxicity of PFOS, NaCl and pyraclostrobin to Daphnia magna. In our most recent work, MS student Amanda Isabella has explored the interactive effects of chronic NaCl exposure with a pyraclostrobin pulse exposure occurring during the peak phase of the population cycle of D. magna. Key findings are described below.

We had previously developed a dynamic energy budget – individual based model (DEB-IBM) for daphnia that was spatially explicit and included crowding as a factor important to daphnia population dynamics. The model produces output that closely matches our experimental population data provided, we have resource-specific toxicity values.As well, the model has been applied to data generated by Tim Woo involving the effects of resource environment on toxicity of pyraclostrobin and will be used by Amanda Isabella to predict effects of two chemicals and non-consumptive predator effects in D. magna.

Specific Aim 3: Establish bioenergetics-based responses, life history effects and population-level effects of individual study species exposed to PFOS and pyraclostrobin in addition to the presence of conspecific competitors and predators.

Endpoints: Same as Specific Aim 1 plus modified life history based on species interactions (competition coefficients; predator-prey coefficients)

Models: Density dependent, resource based population models; Modified population models that include mortality from predation

Summary Specific Aim 3 Progress: We have completed studies in which we have combined L. stagnalis and D. magna and are preparing for studies that include predators of D. magna. In this scenario with L. stagnalis, the nature of the interaction is energetic facilitation to D. magna via L. stagnalis. Specifically, L. stagnalis liberates sources of energy (lettuce) making it available to D. magna. This is a relatively under studied form of species interaction but one that is likely common and potentially important. Also, our population study design for D. magna includes density-dependent effects and hence, intra-species competition. Our DEB-IBM also captures these dynamic well and illustrates one important attribute of IBMs – properties and dynamics of populations can emerge from the interactions and behaviors of individuals. To support the D. magna + L. stagnalis studies, we have developed a model that links DEB models for daphnia and snails and yields excellent agreement with study results.

Future Activities:

We have just initiated studies to explore the nonconsumptive effects of predation by fathead minnows on D. magna and have found very strong effects that have reduced the survival of Daphnia when exposed to non-consumptive predator cues.


Journal Articles on this Report : 2 Displayed | Download in RIS Format

Other project views: All 19 publications 2 publications in selected types All 2 journal articles
Type Citation Project Document Sources
Journal Article Reategui-Zirena EG, Fidder BN, Olson AD, Dawson DE, Bilbo TR, Salice CJ. Transgenerational endpoints provide increased sensitivity and insight into multigenerational responses of Lymnaea stagnalis exposed to cadmium. Environmental Pollution 2017;224:572-580. R835800 (2016)
R835800 (2017)
R835800 (2018)
  • Abstract from PubMed
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Rohr JR, Salice CJ, Nisbet RM. The pros and cons of ecological risk assessment based on data from different levels of biological organization. Critical Reviews in Toxicology 2016;46(9):756-784. R835800 (2016)
    R835800 (2017)
    R835800 (2018)
    R835188 (Final)
    R835797 (2015)
    R835797 (2016)
    R835797 (Final)
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  • Abstract from PubMed
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  • Full-text: University of South Florida-Full Text PDF
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  • Abstract: Taylor & Francis-Abstract
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  • Progress and Final Reports:

    Original Abstract
  • 2016 Progress Report
  • 2017 Progress Report
  • 2019