Interactions of habitat complexity and environmental characteristics with macrobenthic community structure at multiple spatial scales in the northeastern Chukchi Sea

Spatial trends in macrobenthic communities from the northeastern Chukchi Sea are evaluated to understand how ecological processes influencing macrofauna differ between small and large scales. Macrobenthos was sampled with a van Veen grab in a mesoscale study (distances ~10–200 km) in 1986 and in a midscale study (distances ~2–20 km) in 2008–2010. Common field and laboratory methods allowed for a direct comparison of the data sets. Environmental characteristics influencing spatial structures of macrobenthic communities varied with the scale of sampling. Midscale variations of macrofaunal community structure in the 2008–2010 study were associated with the local topographic variations resulting in an enhanced carbon deposition and a greater biological production; total density increased with the increasing water depth and organic carbon. Mesoscale environmental gradients in the 1986 study, reflecting physical dynamics, water mass movements, and oceanographic conditions, were associated with an inshore to offshore faunal gradient as density declined with greater water depth. Differences in environmental and biological community relationships between scales included shifts in the regression relationships between water depth and macrobenthic density with declining density at the mesoscale and the increasing density with greater depth at the midscale. Biomass declined more sharply with increased bottom-water temperature in the midscale study than in the mesoscale investigation. Multivariate analyses demonstrated similar shifts in the relationship between biotic summary measures and water depth. Increased benthic production is noted in other areas of the Chukchi Sea in association with topographic variations, and such variations may be predictive of increased benthic production. Ecologically significant changes in relationships of environmental and biological gradients between spatial scales indicate the need for small-scale sampling to detect long-term change in marine communities.