Dynamic energy budgets and bioaccumulation : a model for marine mammals and marine mammal populations

Submitted to the Department of Biology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biological Oceanography at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2006Energy intake of individuals affects growth of organisms and, therefore, populations. Persistent lipophilic toxicants acquired with the energy can bioaccumulate and harm individuals. Marine mammals are particularly vulnerable because of their large energy requirements, and transfer of energy and toxicants from mothers to their young during gestation and lactation. Dynamic energy budget (DEB) models for energy assimilation and utilization, coupled with pharmacokinetic models that calculate distribution of toxicants in individuals, can help investigate the vulnerability. In this dissertation I develop the first individual DEB model tailored specifically to marine mammals and couple it to a pharmacokinetic model for lipophilic toxicants. I adapt the individual model to the right whale and use it to analyze consequences of energy availability on individual growth, reproduction, bioaccumulation, and transfer of toxicants between generations. From the coupled model, I create an individual-based model (IBM) of a marine mammal population. I use it to investigate how interactions of food availability, exposure to toxicants, and maternal transfer of toxicants affect populations. I also present a method to create matrix population models from a general DEB model to alleviate some of the drawbacks of the IBM approach.This work has been supported by the David and Lucile Packard Foundation, the US National Science foundation (DEB-9973518 and OCE-0083976), the US Environmental Protection Agency (R-82908901-0), the National Oceanographic and Atmospheric Administration (NAO 3NMF4720491) and the WHOI/MIT Joint Program in Oceanography

A model for energetics and bioaccumulation in marine mammals with applications to the right whale

Author Posting. © Ecological Society of America, 2007. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 17 (2007): 2233–2250, doi:10.1890/06-0426.1.We present a dynamic energy budget (DEB) model for marine mammals, coupled with a pharmacokinetic model of a lipophilic persistent toxicant. Inputs to the model are energy availability and lipid-normalized toxicant concentration in the environment. The model predicts individual growth, reproduction, bioaccumulation, and transfer of energy and toxicant from mothers to their young. We estimated all model parameters for the right whale; with these parameters, reduction in energy availability increases the age at first parturition, increases intervals between reproductive events, reduces the organisms' ability to buffer seasonal fluctuations, and increases its susceptibility to temporal shifts in the seasonal peak of energy availability. Reduction in energy intake increases bioaccumulation and the amount of toxicant transferred from mother to each offspring. With high energy availability, the toxicant load of offspring decreases with birth order. Contrary to expectations, this ordering may be reversed with lower energy availability. Although demonstrated with parameters for the right whale, these relationships between energy intake and energetics and pharmacokinetics of organisms are likely to be much more general. Results specific to right whales include energy assimilation estimates for the North Atlantic and southern right whale, influences of history of energy availability on reproduction, and a relationship between ages at first parturition and calving intervals. Our model provides a platform for further analyses of both individual and population responses of marine mammals to pollution, and to changes in energy availability, including those likely to arise through climate change.This research was supported by the David and Lucile Packard Foundation, the U.S. National Science Foundation (DEB-9973518 and OCE-0083976), the U.S. Environmental Protection Agency (R-82908901-0), NOAA grant NA03NMF4720491, and the WHOI/MIT Joint Program in Oceanography

Quantifying research waste in ecology

Research inefficiencies can generate huge waste: evidence from biomedical research has shown that most research is avoidably wasted and steps have been taken to tackle this costly problem. Although other scientific fields could also benefit from identifying and quantifying waste and acting to reduce it, no other estimates of research waste are available. Given that ecological issues interweave most of the United Nations Sustainable Development Goals, we argue that tackling research waste in ecology should be prioritized. Our study leads the way. We estimate components of waste in ecological research based on a literature review and a meta-analysis. Shockingly, our results suggest only 11–18% of conducted ecological research reaches its full informative value. All actors within the research system—including academic institutions, policymakers, funders and publishers—have a duty towards science, the environment, study organisms and the public, to urgently act and reduce this considerable yet preventable loss. We discuss potential ways forward and call for two major actions: (1) further research into waste in ecology (and beyond); (2) focused development and implementation of solutions to reduce unused potential of ecological research

Quantifying impacts of plastic debris on marine wildlife identifies ecological breakpoints

Quantifying sublethal effects of plastics ingestion on marine wildlife is difficult, but key to understanding the ontogeny and population dynamics of affected species. We developed a method that overcomes the difficulties by modelling individual ontogeny under reduced energy intake and expenditure caused by debris ingestion. The predicted ontogeny is combined with a population dynamics model to identify ecological breakpoints: cessation of reproduction or negative population growth. Exemplifying this approach on loggerhead turtles, we find that between 3% and 25% of plastics in digestive contents causes a 2.5–20% reduction in perceived food abundance and total available energy, resulting in a 10–15% lower condition index and 10% to 88% lower total seasonal reproductive output compared to unaffected turtles. The reported plastics ingestion is insufficient to impede sexual maturation, but population declines are possible. The method is readily applicable to other species impacted by debris ingestion

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Predicting climate change impacts on polar bea

Predictions of SCW and BD by two types (M1—linear, and M2—saturating) of models ‘<i>m</i>_<i>I</i>’, ‘<i>m</i>_{<i>II</i> + <i>III</i>}’, and ‘<i>m</i>_{<i>I</i> + <i>II</i> + <i>III</i>}’.

<p>Predictions are given for average sizes at specific events (hatching, recruitment, nesting). Symbols are coded based on the model (each symbol corresponds to one model), and type (full or empty symbol).</p

Fit of suggested subset-specific (‘<i>m</i>_<i>I</i>’, ‘<i>m</i>_{<i>II</i> + <i>III</i>}’, panels (a), (c), (e)), and non-specific (‘<i>m</i>_{<i>I</i> + <i>II</i> + <i>III</i>}’, panels (b), (d), (f)) linear scaling models to data.

<p>The relationship of log(<i>SCW</i>) to log(<i>SCL</i>) is shown in panels (a) and (b), the relationship of log(<i>BD</i>) to log(<i>SCL</i>) in panels (c) and (d), and the relationship of log(<i>BD</i>) to log(SCW) in panels (e) and (f). The recommended regression equations are displayed in the plot, while parameters for remaining equations are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143747#pone.0143747.t005" target="_blank">Table 5</a>. Dashed lines mark the 95% confidence intervals of the predictions. Black arrows in panels (b), (d), and (f) point to the size range in which predictions are underestimated.</p