Macroinvertebrates in Arctic Lakes

The kinds of insects found in waterbodies can tell us about water quality and environmental conditions.

Ongoing environmental change across the Arctic is affecting many freshwater ecosystems. These changes may in turn impact macroinvertebrates, important forage for fish and bird species. To predict how wildlife species may be affected by ecosystem change at high latitudes, understanding the factors that influence macroinvertebrate abundance is critical. To better understand patterns in abundance, we collected aquatic macroinvertebrates from 33 ponds on the Arctic Coastal Plain in Northern Alaska. We then estimated abundance in relation to pond type and seasonal patterns in water temperature and nutrient levels for five taxonomic groups. For three of the five taxa we considered, abundance varied by pond type and was lower in ponds where water temperature increased more rapidly. In addition, our results suggest that seasonal patterns in abundance were influenced by changes in water temperature. Overall, these findings suggest that increases in water temperature in northern areas could alter macroinvertebrate phenology, with possible consequences for other wildlife species dependent on them. Our results will be useful in improving predictions of how changing conditions could affect freshwater systems in northern areas.

In hot water? Patterns of macroinvertebrate abundance in Arctic thaw ponds and relationships with environmental variables

Abstract

1. Ongoing environmental change across the Arctic is affecting many freshwater ecosystems, including small thaw ponds that support macroinvertebrates, thus potentially affecting important forage for fish and bird species. To accurately predict how fish and wildlife that depend on these macroinvertebrates will be affected by ecosystem change at high latitudes, understanding proximate factors that influence macroinvertebrate abundance is critical.

2. To better understand factors that affect spatial and seasonal (i.e. phenology) patterns in abundance, we collected macroinvertebrates throughout the growing season of a single year from 33 thaw ponds on the Arctic Coastal Plain in northern Alaska. We used hierarchical N-mixture models to provide detection-corrected estimates of abundance (of the population exposed to sampling) in relation to pond type and seasonal patterns in environmental variables (i.e., cumulative water temperature, nutrient levels) for five taxonomic groups representing key food items for birds and fish—Anostraca (Arthropoda: Branchiopoda), Chironomidae (Insecta: Diptera), Cladocera (Arthropoda: Branchiopoda), Limnephilidae (Insecta: Trichoptera), and Physidae (Mollusca: Gastropoda).

3. For three of five taxa (Anostraca, Cladocera, Limnephilidae), abundance varied across pond types and was lower in pond types where water temperatures increased more rapidly. Further, seasonal temperature profiles in ponds affected phenology, suggesting that seasonal patterns in abundance were influenced by changes in water temperature.

4. These findings suggest that increases in water temperature in northern areas could alter macroinvertebrate phenology, possibly with consequences for upper level predators if availability of macroinvertebrate prey is reduced or shifted seasonally. Our results will facilitate improved predictions of how changing abiotic conditions could affect inland waters in northern areas, a critical need for conservation of Arctic wildlife and ecosystems.

Gurney, K. E. B., J. C. Koch, J. A. Schmutz, J. H. Schmidt, and M. S. Wipfli. 2022. In hot water? Patterns of macroinvertebrate abundance in Arctic thaw ponds and relationships with environmental variables. Freshwater Biology 67(10): 1832-1844.