Hydrological connectivity influences the aquatic metacommunity structure of an Arctic delta floodplain

Hydrological connectivity is fundamental determinant of aquatic metacommunity structure, but the potential response to altered patterns of connectivity in a changing climate remain poorly understood, particularly in regards to vulnerable systems such as Arctic deltaic lakes. Here we present the first study to examine the metacommunity structure of aquatic invertebrates in a major Arctic floodplain system (Mackenzie Delta, Northwest Territories). We sampled macroinvertebrate communities across the longitudinal span of the Delta and utilized three complementary techniques (variance partitioning, elements of metacommunity structure, and fourth corner analysis) to determine the relative influence of environmental versus spatial variation, metacommunity structure across dispersal modes, and the functional metacommunity structure. Environmental factors explained the most variation (23%) compared to spatial factors (2%) or environmental/spatial covariance (4%). Functional structure was primarily related to dispersal mode and lake isolation, with distributions of aerial dispersers determined mainly by environmental factors and aquatic dispersers by both dispersal limitation and environmental factors. We attribute these results to the inter-lake mixing effects of annual flooding and the lack of barriers to aerial dispersal, and discuss how a loss of aquatic invertebrate biodiversity could result from projected climate-mediated alterations to ice jam dynamics in the Delta.