Spatial variation in biodiversity and abundance of benthic macrofauna in Chukchi Sea and Northern Behring Sea. Sediments are collected by Smith-Mclntyre grab sampler to quantify the diversity of benthic invertebrates. Target animals are separated from sediments with 1mm sieve. Epifaunal benthic invertablates are collected by sled trawl. Collected samples are sorted out the species and counted for estimating abundance and biomass.