Energy expenditure in a warmer Arctic

Climate change is one of the factors with an influence on food web structure. This month’s question is: Will animals have the necessary capacity to adjust their energetic expenditure and behaviour, based on available resources, without altering their fitness? In the Arctic, where temperatures are increasing at a faster rate than anywhere else on Earth, its organisms are strong models in understanding the biological implications in light of climate change.

The authors of this study analysed the plasticity of the daily energy expenditure (DEE) of an Arctic seabird, the little auk (Alle alle), in response to the sea surface temperature (SST) and summer ice cover (SIC), which affect copepod availability, their main food source. Data from colonies in East Greenland and Southwest Spitsbergen, Svalbard was analysed. In addition, the bioenergetic characteristics may also be influenced by exposure to chemical substances, and as such they also tested their response to the presence of mercury, typically released in the Arctic with the melting of permafrost (1).

In bird species, the DEE during the chick-rearing season is usually about 4 times the basal metabolic rate (BMR, 2), with a superior limit of 7x BMR, and little auks have a BMR of approximately 1.09KJ per day, per gram of body weight. In Greenland, the high costs of flying associated with a low SIC and a high SST elevated the DEE from below 4x BMR to above that value, without reaching the superior limit. In Svalbard, the DEE was even higher, associated with a higher investment in diving in search of prey (Figure 1). The observed values are typical of the reproductive season, and thus there was no evidence of an unsustainable energetic expenditure associated with SST, SIC and mercury exposure.

Figure 1. Relationship between daily energy expenditure (DEE) of little auks and the sea surface temperature (SST) in three sites (Greenland: Ukaleqarteq; Svalbard: Hornsund e Kongsfjorden). The horizontal dotted lines indicate the DEE values correspondent to 4x and 7x the metabolic basal rate (BMR).

Little auks demonstrated plasticity in managing their energy use towards an oscillation in oceanic conditions and prey availability. Strategies to maintain resource intake include increased time and area when in search of food and altering the breeding season to match high available resource peaks. Nonetheless, species with lower energy amplitudes may show less plasticity. And on top of that, modelling future scenarios suggests a continuous increase in SST, which may threaten the physical capability of these birds.

Understanding the limits and energy trades of various species in a context of environmental variability should be a priority in future research. Little auks are true ecosystem engineers because they contribute to the flux of nutrients between the terrestrial and marine domains. As such, changes in these population dynamics due to a possible unsustainable energy expenditure may result in a cascade effect for the ecosystems.

(1) Permafrost = Underground layer of the Earth’s crust that is permanently frozen.

(2) Basal metabolic rate = Energy quantity necessary to maintain vital functions of an organism during 24 hours, measured in calories.

Author: Débora Carmo

Source: Grunst, M. L., Grunst, A. S., David, G., Kato, A., Bustamante, P., Albert, C., Brisson-Curadeau, E., Manon, C., Cruz-Flores, M., Gentès, S., Grissot, A., Perret, S., Eric, S.-M., Jakubas, D., Wojczulanis-Jakubas, K., & Fort, J. (2023). A keystone avian predator faces elevated energy expenditure in a warming Arctic. Ecology, March, 1–12. DOI:


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