Areas of Research

My students, colleagues and I comprise a multidisciplinary research group of environmental scientists. We study the movement of metals (such as mercury and arsenic) through aquatic food webs; toxicogenomics of Daphnia pulex; conservation and restoration of Atlantic salmon; and decision-making by fish. We work in streams and lakes throughout the New England region and as far away as New Zealand and China.

1. Accumulation and Biomagnification of Metals (mercury, arsenic, cadmium and zinc) in Aquatic Food Webs. Collaborators include Dr. Celia Chen, Dr. Joseph Shaw, Dr. Joshua Hamilton, and graduate students Roxanne Karimi and Darren Ward.

The ecological fate and impact of metals in aquatic systems involves both their trophic transfer to fish (i.e., the movement of metal through food webs) as well as the exposure and toxic effects on individuals and populations. Consumption of contaminated fish is a public health concern. For both humans and wildlife, fish are important agents of exposure to metals such as mercury. Forty-eight states currently issue advisories against consumption of fish due to the buildup of metals such as mercury and other toxins in their tissues. However, differences in water chemistry and food web structure can produce significant lake-to-lake variation in the amount of metal that moves from the water through the food chain to fish. Hence, fish in different lakes frequently carry different metal burdens even when lakes receive apparently similar inputs. By determining key factors and mechanisms driving this variation within and across lakes (such as productivity, adjacent land use, food web structure, habitat use, timing of metal deposition, etc.), we seek to predict more accurately the lakes and habitats containing fish with high metal levels. This information could eventually lead to site-specific consumption advisories that are more useful to the public, municipal planners and regulators.

2. Environment-Gene Responses in the Aquatic Crustacean, Daphnia pulex. Collaborators include Dr. Celia Chen, Dr. Joseph Shaw, Dr. Joshua Hamilton, Dr. John Colbourne and Dr. Michael Lynch.

Our interdisciplinary team is also working to develop the cladoceran Daphnia pulex as a toxicogenomic model organism to understand gene-environment interactions subject to the action of multiple metal stressors in aquatic ecosystems, and to provide biomarkers of short-term molecular stress as an early warning system for metal exposure in field populations. Large cladocerans (in the genus Daphnia) are called keystone species due to their central role in lake ecology. Commonly used in environmental toxicological testing, we have shown that they carry greater mass-specific burdens of some metals, and are favored prey items of fish. Hence their abundance in a lake signals the potential for increased rates of metal trophic transfer from water to fish. By focusing on toxicogenomics of Daphnia in the context of multiple environmental stressors we seek to improve the relevance of toxicological studies to natural populations across a range of realistic environmental conditions.

3. Restoration of Atlantic Salmon. Collaborators include Dr. Keith Nislow, Dr. Brian Kennedy and graduate student Darren Ward.

With our Atlantic salmon research, my students, colleagues and I seek to predict the effects of changes in habitat quality on the growth and survival of freshwater phase salmonids in New England streams. We are also very involved in the development of stable isotope technologies to track fish movements and to estimate fish consumption. We see the value of our work that (1) it forms a sound scientific basis for a mechanistic understanding of fish community interactions and dynamics, and (2) it can lead to more effective strategic stocking practices, inform stream fishery and forest management, and lead to long-term restoration and sustainability of salmonid populations in a variety of regions world-wide.

4. Information Gathering and Decision-Making in Animal Behavior. Collaborators include Dr. Deborah Chiavelli and graduate student Wenjing Dai.

The distribution of aquatic organisms is notoriously patchy, and yet quantitative investigations of this patchiness and its influence on species interactions are relatively rare. Our group has been studying aspects of prey patchiness in aquatic ecosystems for more than 20 years. Most recently we have focused on effects of prey patchiness on animal decision-making. Fish foraging decisions are likely to be affected by the uncertainty in encountering prey that accompanies prey patchiness in natural situations. One common effect of prey patchiness is to increase the delay between captures. As delay increases, predators are assumed to become more uncertain about the likelihood of future prey captures. The influence of such uncertainty on decision-making is referred to as temporal discounting in economics and psychology. Temporal discounting as applied to foraging behavior is the extent to which the subjective (or perceived) value of a prey item to a forager decreases as the delay between prey captures increases. We are currently developing methods to quantify temporal discounting experimentally using pumpkinseed sunfish (Lepomis gibbosus) and to compare temporal discounting in single and mixed-prey treatments using zooplankton as prey.


		Areas of Research My students, colleagues and I comprise a multidisciplinary research group of environmental scientists. We study the movement of metals (such as mercury and arsenic) through aquatic food webs; toxicogenomics of Daphnia pulex; conservation and restoration of Atlantic salmon; and decision-making by fish. We work in streams and lakes throughout the New England region and as far away as New Zealand and China. 1. Accumulation and Biomagnification of Metals (mercury, arsenic, cadmium and zinc) in Aquatic Food Webs. Collaborators include Dr. Celia Chen, Dr. Joseph Shaw, Dr. Joshua Hamilton, and graduate students Roxanne Karimi and Darren Ward. The ecological fate and impact of metals in aquatic systems involves both their trophic transfer to fish (i.e., the movement of metal through food webs) as well as the exposure and toxic effects on individuals and populations. Consumption of contaminated fish is a public health concern. For both humans and wildlife, fish are important agents of exposure to metals such as mercury. Forty-eight states currently issue advisories against consumption of fish due to the buildup of metals such as mercury and other toxins in their tissues. However, differences in water chemistry and food web structure can produce significant lake-to-lake variation in the amount of metal that moves from the water through the food chain to fish. Hence, fish in different lakes frequently carry different metal burdens even when lakes receive apparently similar inputs. By determining key factors and mechanisms driving this variation within and across lakes (such as productivity, adjacent land use, food web structure, habitat use, timing of metal deposition, etc.), we seek to predict more accurately the lakes and habitats containing fish with high metal levels. This information could eventually lead to site-specific consumption advisories that are more useful to the public, municipal planners and regulators. 2. Environment-Gene Responses in the Aquatic Crustacean, Daphnia pulex. Collaborators include Dr. Celia Chen, Dr. Joseph Shaw, Dr. Joshua Hamilton, Dr. John Colbourne and Dr. Michael Lynch. Our interdisciplinary team is also working to develop the cladoceran Daphnia pulex as a toxicogenomic model organism to understand gene-environment interactions subject to the action of multiple metal stressors in aquatic ecosystems, and to provide biomarkers of short-term molecular stress as an early warning system for metal exposure in field populations. Large cladocerans (in the genus Daphnia) are called keystone species due to their central role in lake ecology. Commonly used in environmental toxicological testing, we have shown that they carry greater mass-specific burdens of some metals, and are favored prey items of fish. Hence their abundance in a lake signals the potential for increased rates of metal trophic transfer from water to fish. By focusing on toxicogenomics of Daphnia in the context of multiple environmental stressors we seek to improve the relevance of toxicological studies to natural populations across a range of realistic environmental conditions. 3. Restoration of Atlantic Salmon. Collaborators include Dr. Keith Nislow, Dr. Brian Kennedy and graduate student Darren Ward. With our Atlantic salmon research, my students, colleagues and I seek to predict the effects of changes in habitat quality on the growth and survival of freshwater phase salmonids in New England streams. We are also very involved in the development of stable isotope technologies to track fish movements and to estimate fish consumption. We see the value of our work that (1) it forms a sound scientific basis for a mechanistic understanding of fish community interactions and dynamics, and (2) it can lead to more effective strategic stocking practices, inform stream fishery and forest management, and lead to long-term restoration and sustainability of salmonid populations in a variety of regions world-wide. 4. Information Gathering and Decision-Making in Animal Behavior. Collaborators include Dr. Deborah Chiavelli and graduate student Wenjing Dai. The distribution of aquatic organisms is notoriously patchy, and yet quantitative investigations of this patchiness and its influence on species interactions are relatively rare. Our group has been studying aspects of prey patchiness in aquatic ecosystems for more than 20 years. Most recently we have focused on effects of prey patchiness on animal decision-making. Fish foraging decisions are likely to be affected by the uncertainty in encountering prey that accompanies prey patchiness in natural situations. One common effect of prey patchiness is to increase the delay between captures. As delay increases, predators are assumed to become more uncertain about the likelihood of future prey captures. The influence of such uncertainty on decision-making is referred to as temporal discounting in economics and psychology. Temporal discounting as applied to foraging behavior is the extent to which the subjective (or perceived) value of a prey item to a forager decreases as the delay between prey captures increases. We are currently developing methods to quantify temporal discounting experimentally using pumpkinseed sunfish (Lepomis gibbosus) and to compare temporal discounting in single and mixed-prey treatments using zooplankton as prey.
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