Understanding biodiversity in unknown Ecosystems: Eskers

Background/Question/Methods

Eskers are complex geological formations formed by glaciers during the last ice age. Now, Eskers provide crucial resources in northern countries such as drinking water, sand/gravel, outdoor recreational sites, and productive forests. However, there is a huge knowledge gap about the biodiversity and functioning of eskers. Esker lakes are different from other boreal lakes as they are mainly fed by groundwaters and precipitations and are not connected to other aquatic ecosystems. Thus, esker lakes should have reduced or absent fish communities, which promotes a unique diversity and abundance of aquatic invertebrates. This research aims to characterize the waterbird communities associated to esker lakes, identify ecological factors, and characterize the resources such as fish and aquatic macroinvertebrate diversity that determine waterbird presence, abundance, richness, and diversity using a food web approach. Fifty lakes were sampled including lakes situated on eskers and lakes on the clay belt in Abitibi. The observational point and flush count method were applied to study the bird communities. The macroinvertebrate samples were collected using a D-frame net and identified in the laboratory using a stereomicroscope. Additionally, we used minnow traps to catch fish with three replications and measured each species.

Results/Conclusions

We identified 434 waterbirds with a richness of 14 species, 6406 fish with a richness of 10 species, and 19948 macroinvertebrates with a richness of 43 taxa. We found higher Shannon diversity for waterbirds in clay lakes (mean = 0.45) compared to esker lakes (mean = 0.31). It can be explained by the available macroinvertebrate resources, which is higher in clay lakes (mean = 1.29). For fish, the Shannon diversity index value in clay lakes (mean = 0.76) were higher, which could be explained by the isolation of esker lakes into the aquatic ecosystem. Additionally, nutrients, and conductivity in clay lakes were higher than in esker lakes, however, dissolved oxygen was higher in esker lakes. There was a significant effect of macroinvertebrate richness, dissolved oxygen, and macrophyte cover on the waterbird richness. The result suggests, the diversity of esker lakes is lower in all trophic level of the food web but provide habitat to a few rare and important communities such as Bucephala clangula (p < .05). This project represents the first characterization of biodiversity associated to esker lakes; therefore, it will provide the baseline ecological information to establish conservation strategies and the sustainable management of this vulnerable ecosystem.