2016 Progress Report: Dynamical Systems Models Based on Energy Budgets for Ecotoxicological Impact Assessment

EPA Grant Number: R835797
Title: Dynamical Systems Models Based on Energy Budgets for Ecotoxicological Impact Assessment
Investigators: Nisbet, Roger M. , Muller, Erik B , Stevenson, Louise M , Whitehead, Andrew
Current Investigators: Nisbet, Roger M. , Muller, Erik B , Whitehead, Andrew
Institution: University of California - Santa Barbara , University of California - Davis
EPA Project Officer: Lasat, Mitch
Project Period: June 1, 2015 through May 31, 2018 (Extended to May 31, 2019)
Project Period Covered by this Report: June 1, 2016 through May 31,2017
Project Amount: $799,723
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:

The overarching questions motivating the research are:

a. How do changes in suborganismal-level endpoints (e.g., molecular, cellular, and tissue level responses) relate qualitatively and quantitatively to changes in apical endpoints such as survival, growth, and reproduction?

b. How can we characterize the qualitative and quantitative relationships between changes in apical endpoints and those at higher levels of biological organization (population, community, landscape)?

The specific objectives are:

Objective 1: Formulate and test new theory relating organismal dynamics to suborganismal responses to toxicant exposure

1a) Develop new DEB models with mechanistic connections to suborganismal processes including those currently used in Adverse Outcome Pathway (AOP) studies

1b) Use data from literature and new experiments to determine for two model organisms the extent to which transcriptomic data relate to DEB model parameters and organismal dynamics

1c) Use the new DEB models for qualitative prediction of “tipping points” caused by failure of feedback processes within an organism.

Objective 2: Use individual-based population models to predict possible population level responses to exposure to toxicants

2a) Formulate and test individual-based population models to project effects on interacting phytoplankton and zooplankton populations

2b) Use models from objective 2a to investigate the likelihood of “tipping points” representing abrupt extinctions

2c) Develop models of adaptation to stress that take account of sub-organismal regulatory processes and thereby provide tools for evaluating the likelihood of evolutionary rescue in chronically polluted environments.

Objective 3: Investigate applicability of new concepts to non-model organisms.

3a) Determine the additional information required for generalizing findings from objectives 1 and 2.

Progress Summary:

Objective 1a. We collaborated with Dr. Cheryl Murphy (also an investigator supported by the STAR program “Systems-Based Research for Evaluating Ecological Impacts of Manufactured Chemicals”) and others in a working group at the National Center for Mathematical and Biological Synthesis (NIMBioS), to develop a new, general, conceptual framework for relating information from Adverse Outcome Pathways (AOP) to processes in DEB models. This is described in a book chapter, and a second publication that emphasizes practical implications of the new framework is in advanced preparation.

Recognizing that many organisms, including the focal fish species in our study, have annual reproductive cycles, we developed a new variant (demandDEB) of the “standard” DEB model. DemandDEB includes within-year changes in energy utilization, that are hypothesized to be a consequence of “demand-driven” allocation to reproduction. The suborganismal fluxes in demandDEB represent hormonally controlled chemical reactions within the animal, thereby permitting connection with much published suborganismal data on the impact of endocrine disruptors.

We completed work on a DEB model (DEBlipid) of lipid dynamics over a fish life cycle based on data froma broad range of species.

Objective 1b. We made progress with work on both focal organisms. We devoted considerable effort to developing a reliable parameterization of the “standard” DEB model for the killifish Fundulus heteroclitus. This was challenging because of the need to integrate information from literature sources involving studies in lab and in multiple field locations with data from Dr. Diane Nacci’s group in EPA’s Atlantic Ecology Division Labs. Dr. Nacci’s group has performed experiments in which the fish experienced periods of starvation followed by reintroduction to food; the pattern of changes in weight and length in these experiments giving direct information on one elusive DEB parameter, “energy conductance”. This was an essential prerequisite for pending work involving interpretation of transcriptomic responses for this model species.

Parameters for DEB models for Daphnia magna had previously been estimated - by us and others. In collaboration with 5 members of the NIMBioS working group, we designed a sampling regime for following changes in gene expression in experiments on individual Daphnia exposed to fly ash. The experiments are in progress at the time of writing this report.

Objective 1c. Work was completed and in described in year 1 report.

Objective 2a. A paper reporting experimental work on the response of Daphnia pulicaria to combined food and toxicity stress was published [8], the key finding being that standardized toxicity testing may underestimate toxicity at environmentally relevant food levels. The data from this paper was used to parametrize a DEB model that underpins an individual based population model of the response of interacting phytoplankton and Daphnia populations to waterborne silver nanoparticles. The primary finding was that feedbacks on zooplankton vital rates, mediated by phytoplankton availability, may to some extent mitigate the impacts of exposure to a toxicant. A paper on this work is in advanced preparation.

Objective 2b. There was no work on this during the reporting period.

Objective 2c. There was no work on this during the reporting period.

Objective 3a. The formulation of the DEBlipid model was based on meta-analysis of data from a diverse range of fish species and is consistent with our objective of demonstrating the applicability of our findings to non-model organisms.

Leveraged activities enhanced by this award included the application of DEB theory and related dynamic models in projects performed in collaboration with investigators in the University of California Center for Environmental Implications of Nanotechnology (UC CEIN), a commentary on challenges in DEB theory, and a comment on the value and limitations of AOPs in ecological risk assessment.

Future Activities:

Top priorities for year 3 are: (i) continuing research relating suborganismal and organismal responses to exposure for the killifish Fundulus heteroclitus (objective 1b); continuation and completion of study relating transcriptomic and organism level responses of Daphnia magna (objective 1b); initiation of models relating to “evolutionary rescue” (objective 2c).


Journal Articles on this Report : 9 Displayed | Download in RIS Format

Other project views: All 38 publications 14 publications in selected types All 13 journal articles
Type Citation Project Document Sources
Journal Article Adeleye AS, Stevenson LM, Su, YM, Nisbet RM, Zhang YL, Keller AA. Influence of phytoplankton on fate and effects of modified zerovalent iron nanoparticles. Environmental Science & Technology 2016;50(11):5597-5605. R835797 (2016)
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  • Journal Article Klanjscek T, Muller EB, Holden PA, Nisbet RM. Host-symbiont interaction model explains non-monotonic response of soybean growth and seed production to nano-CeO2 exposure. Environmental Science & Technology 2017;51(9):4944-4950. R835797 (2016)
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  • Journal Article Martin BT, Heintz R, Danner EM, Nisbet RM. Integrating lipid storage into general representations of fish energetics. Journal of Animal Ecology 2017;86(4):812-825. R835797 (2016)
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  • Journal Article Miller RJ, Muller EB, Cole B, Martin T, Nisbet R, Bielmyer-Fraser GK, Jarvis TA, Keller AA, Cherr G, Lenihan HS. Photosynthetic efficiency predicts toxic effects of metal nanomaterials in phytoplankton. Aquatic Toxicology 2017;183:85-93. R835797 (2015)
    R835797 (2016)
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  • Journal Article Nisbet RM. Challenges for dynamic energy budget theory: omment on "Physics of metabolic organization" by Marko Jusup et al. Physics of Life Reviews 2017;20:72-74. R835797 (2016)
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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. R835797 (2015)
    R835797 (2016)
    R835188 (Final)
    R835800 (2016)
    R835800 (2017)
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  • Journal Article Rohr JR, Salice CJ, Nisbet RM. Chemical safety must extend to ecosystems. Science 2017;356(6341):917. R835797 (2016)
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  • Journal Article Stevenson LM, Krattenmaker KE, Johnson E, Bowers AJ, Adeleye AS, McCauley E, Nisbet RM. Standardized toxicity testing may underestimate ecotoxicity:environmentally relevant food rations increase the toxicity of silver nanoparticles to Daphnia. Environmental Toxicology and Chemistry 2017;36(11):3008-2018. R835797 (2016)
    R835797 (2017)
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  • Journal Article Klanjscek T, Muller EB, Nisbet RM. Feedbacks and tipping points in organismal response to oxidative stress. Journal of Theoretical Biology 2016;404:361-374. R835797 (2015)
    R835797 (2016)
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  • Supplemental Keywords:

    Individual-based model; dynamic energy budget, DEB, DEBtox; adverse outcome pathways; metabolism; ecology; ecosystem; scaling; toxics.

    Progress and Final Reports:

    Original Abstract
  • 2015 Progress Report
  • 2017 Progress Report