Composition of marine nematode communities across broad longitudinal and bathymetric gradients in the Northeast Chukchi and Beaufort Seas

Benthic communities are responding to rapid environmental change in the Arctic, yet the ecologically important meiofauna remain poorly studied, leaving little baseline information for evaluating such changes. We investigated the community structure of meiofaunal nematodes (> 63 µm) on the Northeast Chukchi Sea (NEC) continental shelf (< 50 m), and along a broad longitudinal and bathymetric gradient in the Beaufort Sea (BEAU; 20–1200 m). In total, 139 nematode genera representing 32 families were identified. Nematode communities differed between the NEC and BEAU, but the opportunistic genera Sabatieria (Comesomatidae) and Daptonema (Xyalidae) were abundant in both seas. Despite the relatively small sampling area of similar depth across the NEC, spatial variation was reflected by the high abundance of Sabatieria at a subset of sites with higher proportion of fine sediment. Nematode communities in the western BEAU offshore of the Colville River showed little difference among depths, in contrast to areas further east where shelf and upper slope communities were more distinct. Diversity indices were higher in the BEAU than in the NEC, with maximum values in the easternmost area (Banks Island); lower evenness was recorded in the western BEAU (Colville Plume), which was dominated by Sabatieria at all depths. Organic matter quality and quantity influenced community structure in the BEAU. This study provides the first genus-level characterization of nematode communities across this environmentally heterogeneous region. With increased exploration for natural resources and reduced ice coverage, the baseline community structure information provided here supports evaluation of ecosystem change in the Arctic.