Periodic Reporting for period 1 - BioenergArc (Bioenergetic Effects of Anthropogenic Contaminants and Climate Change on a Keystone Arctic Seabird)
Période du rapport: 2021-05-01 au 2023-04-30
Global climate change is transforming bioenergetic landscapes, challenging organisms’ capacity to maintain energy balance. Repercussions are particularly profound in Arctic regions, where rates of warming exceed the global average by a factor of ~4. Animals can display plasticity in behavior and physiology, expanding the breadth of the ecological niche. However, there are limits to animals’ ability to make phenotypic modifications that support energetic homeostasis. The bioenergetic effects of climate change are attracting increasing research attention, but studies are still limited, especially in Arctic endotherms.
Furthermore, diverse chemical contaminants have neurotoxic, endocrine disrupting, and energetic effects that may interact with biological impacts of climate change to modify bioenergetic outcomes. Volatile and persistent chemical contaminants can reach remote regions through long-range transport mechanisms and bioaccumulate up food chains. Climate change is changing dynamics of contaminant cycling in Arctic ecosystems, which can result in increases in exposure. The Arctic Monitoring and Assessment Programme has highlighted elucidating joint effects of climate change and anthropogenic contaminants as a research priority.
The aim of this project (BioenergArc) was to contribute to this objective, using an Arctic seabird (Alle alle) as a model system, and to investigate the following questions: (1) Does contaminant exposure affect metabolic rate and thermoregulatory capacity in a fashion that could undermine capacity to cope with climate change? (2) How does environmental variation and contaminant exposure affect activity budgets and daily energy expenditure (DEE)? (3) Does variation in bioenergetic traits, potentially related to contamination levels, translate into fitness effects?
Several conclusions have resulted from this work. Among the most important are that changes in environmental conditions associated with climate change are transforming activity budgets of little auks, driving energetic costs upward. Behavioral plasticity currently appears to buffer fitness effects, but threatens to become unsustainable as temperatures continue to rise. In addition, results suggest important thermoregulatory implications of the changing cryosphere, with loss of sea ice as a resting substrate increasing thermoregulatory challenge during foraging trips at sea. Although Hg contamination was not associated with variation in activity budgets, DEE, or fitness, there was evidence for effects of Hg contamination on thermoregulatory dynamics. A literature review also revealed diverse avenues through which contaminants and climate change may interactively affect biological response variables.
Furthermore, diverse chemical contaminants have neurotoxic, endocrine disrupting, and energetic effects that may interact with biological impacts of climate change to modify bioenergetic outcomes. Volatile and persistent chemical contaminants can reach remote regions through long-range transport mechanisms and bioaccumulate up food chains. Climate change is changing dynamics of contaminant cycling in Arctic ecosystems, which can result in increases in exposure. The Arctic Monitoring and Assessment Programme has highlighted elucidating joint effects of climate change and anthropogenic contaminants as a research priority.
The aim of this project (BioenergArc) was to contribute to this objective, using an Arctic seabird (Alle alle) as a model system, and to investigate the following questions: (1) Does contaminant exposure affect metabolic rate and thermoregulatory capacity in a fashion that could undermine capacity to cope with climate change? (2) How does environmental variation and contaminant exposure affect activity budgets and daily energy expenditure (DEE)? (3) Does variation in bioenergetic traits, potentially related to contamination levels, translate into fitness effects?
Several conclusions have resulted from this work. Among the most important are that changes in environmental conditions associated with climate change are transforming activity budgets of little auks, driving energetic costs upward. Behavioral plasticity currently appears to buffer fitness effects, but threatens to become unsustainable as temperatures continue to rise. In addition, results suggest important thermoregulatory implications of the changing cryosphere, with loss of sea ice as a resting substrate increasing thermoregulatory challenge during foraging trips at sea. Although Hg contamination was not associated with variation in activity budgets, DEE, or fitness, there was evidence for effects of Hg contamination on thermoregulatory dynamics. A literature review also revealed diverse avenues through which contaminants and climate change may interactively affect biological response variables.
Fieldwork campaigns were conducted during two breeding seasons at Ukaleqarteq, East Greenland (70°44′N, 21°35′W). Central among biologging techniques, was fitting birds with accelerometers to quantify activity budgets. Past work recorded activity using accelerometers, while also measuring energy expenditure using doubly label water. This allowed derivation of an equation to estimate daily energy expenditure (DEE) from accelerometer data. Variation in body temperature (Tb) was measured using ingested loggers. An on-site weather station provided weather data at the colony, while information on sea surface temperature (SST) and sea ice coverage (SIC) was available online. Blood samples were obtained to measure Hg and analyzed using an Advanced Mercury Analyser spectrophotometer.
Key results include that variation in climate change-sensitive environmental conditions (SST; SIC) can transform time-activity budgets of little auks, driving increases in DEE. Behavioral plasticity currently appears to buffer fitness effects. However, modeling suggested accelerating increases in SST and DEE, which could ultimately become unsustainable. Hg levels were unrelated to activity budgets or DEE. These results have been published open access in Ecology, with an accompanying photo gallery article in the Bulletin of the Ecological Society of America.
Second, little auks regulated Tb with activity patterns and environmental conditions. Tb was highest when birds were on land, and increased when birds were resting on sea-ice, following declines while foraging in cold waters. Tb was positively associated with Hg levels when birds were at the colony. These results suggest that loss of sea ice as a resting substrate may increase energy expenditure during foraging trips at sea, and that higher Tb in Hg-contaminated birds could challenge thermoregulatory equilibrium under climate change scenarios. These results are in review in Functional Ecology, with a pre-print available through BioRxiv.
A literature review was also conducted, examining interactive effects of contaminant exposure and environmental variables across five bioenergetic domains. This review highlights diverse pathways through which contaminant-by-climate change interactive effects may arise, and suggests areas for future research. This work is in revision at Global Change Biology.
Results have been further disseminated through presentation at two professional conferences: the 2022 virtual conference of the Animal Behavior Society (Talk), and the 2021 virtual conference of the Association for the Study of Animal Behaviour (Poster).
Key results include that variation in climate change-sensitive environmental conditions (SST; SIC) can transform time-activity budgets of little auks, driving increases in DEE. Behavioral plasticity currently appears to buffer fitness effects. However, modeling suggested accelerating increases in SST and DEE, which could ultimately become unsustainable. Hg levels were unrelated to activity budgets or DEE. These results have been published open access in Ecology, with an accompanying photo gallery article in the Bulletin of the Ecological Society of America.
Second, little auks regulated Tb with activity patterns and environmental conditions. Tb was highest when birds were on land, and increased when birds were resting on sea-ice, following declines while foraging in cold waters. Tb was positively associated with Hg levels when birds were at the colony. These results suggest that loss of sea ice as a resting substrate may increase energy expenditure during foraging trips at sea, and that higher Tb in Hg-contaminated birds could challenge thermoregulatory equilibrium under climate change scenarios. These results are in review in Functional Ecology, with a pre-print available through BioRxiv.
A literature review was also conducted, examining interactive effects of contaminant exposure and environmental variables across five bioenergetic domains. This review highlights diverse pathways through which contaminant-by-climate change interactive effects may arise, and suggests areas for future research. This work is in revision at Global Change Biology.
Results have been further disseminated through presentation at two professional conferences: the 2022 virtual conference of the Animal Behavior Society (Talk), and the 2021 virtual conference of the Association for the Study of Animal Behaviour (Poster).
This project combined a suite of sophisticated biologging approaches to advance understanding of how animals respond to the joint pressures of climate change and chemical contaminant exposure, yielding novel results. For example, by combining accelerometry data with the doubly labeled water approach, while incorporating information about environmental conditions, we demonstrate the potential for warming temperatures to force organismal energy expenditure upward, which may eventually challenge the ability of individuals to maintain high fitness. In addition, combining accelerometry data with body temperature logging allows new insight into how body temperature is regulated with activity patterns, and suggests that the evolving cryosphere may have non-trivial impacts on thermoregulatory dynamics. Furthermore, this work contributes to filling a void in understanding regarding interactive effects of climate change and contaminant exposure on bioenergetics, with a focus on effects of mercury (Hg). Although no effects of Hg emerged when considering overall energy expenditure and time activity budgets, there were concerning effects on thermoregulatory dynamics, which could be amplified under climate change. On-going work is further examining the potential effects of Hg on thermoregulation, using infrared thermography. Little auks are a keystone species, which play a critical role in transferring resources between marine and terrestrial habitats. Thus, declines in the abundance of this species, or changes in its behavior, may have downstream effects on an array of other organisms, and the productivity of ecosystems. In addition to advancing basic scientific understanding, this research will help inform conservation initiative of the Arctic Council. Furthermore, communication of results to the general public will aim to increase societal understanding of, and appreciation for, the impacts of climate change.