Vertical and geographic distribution of copepod communities at late summer in the Amerasian Basin, Arctic Ocean.

Zooplankton plays a pivotal role in linking primary production to higher level consumers in the food webs of marine ecosystems. The distribution of zooplankton is affected by general water conditions, monsoons, currents, and spatial and temporal factors. In the Arctic Ocean, the sea surface is naturally covered with ice. Under ice, water masses interplay to create complex environments that facilitate the transport and distribution of zooplankton, thus altering community structures at geospatial and vertical scales. The present study investigated the species composition and copepod community structures by using geospatial and multiple depth scales, and using multivariate analyses to evaluate the relation of sampling stations and layers. During July-August 2010, zooplankton samples were collected and the temperature and salinity of seawater measured from three stations in the Canada Basin and two stations in the Makarov Basin of the Arctic Ocean (maximum distance of approximately 1400 km). A total of 55 copepod species (including 25 species that were solely identified to the generic level) and 7 taxa of copepodites, altogether belonging to 28 genera, 11 families, and 2 orders were identified, and significant differences were detected in copepod community structures among sampling strata and at geospatial scales. Numerically, Calanus hyperboreus, Calanus copepodite, Calanoida copepodite, Calanus glacialis, and Metridia longa were the most dominant species and taxa. At the local scale, copepod compositions responded differently at each of the sampling stations. At the geospatial scale, the distance between stations MS03 and ICE explained variations in the pattern of dominant species and of copepod community richness. Our study demonstrated varied spatial distribution which indicates that (1) the abundance of copepods at 0-200 m was significantly higher than at other strata, (2) vertical strata affected the distribution of copepod communities, and (3) the interplay of North Pacific and Atlantic waters shaping the copepod assemblage structure at geospatial scales in the Arctic Ocean. The results of our research provide base data for Arctic zooplankton biodiversity and biogeographic distribution.