Composition and structure of macrozoobenthos of exposed sandy littoral on Bering Island

Abstract

This paper presents key primary data from the initial phase of a longitudinal ecological monitoring project on the composition and spatial structure, and temporal change of the macrozoobenthos species on an exposed sandy beach on Bering Island (Commander Islands, northwestern Pacific Ocean) collected during May 2016 – April 2017. Five species are found (in order of decreasing of occurrence): Eogammarus schmidti (Amphipoda, Crustacea), Archaeomysis grebnitzkii (Mysidacea, Crustacea), Microspio theeli (Spionidae, Annelida), Eteone longa (Phyllodocidae, Annelida), and Locustogammarus locustoides (Amphipoda, Crustacea). Thus, this work builds upon and extends the list of species previously reported in literature. The mean biomass varied from 1.85 g/m2 in April to 78.47 g/m2 in November with an annual mean of 36.98 g/m2 (standard error of the mean = 7.02). The mean abundance varied from 43 individuals/m2 in April to 2257 individuals/m2 in November with an annual mean of 1013 individuals/m2 (standard error of the mean = 187), which is relatively low compared to literature data for other sites in the North Pacific. The abundance is higher in the lower littoral and remarkably lower in the middle and higher littoral. The ecological relationships between these described species could not be elucidated yet. Within the population of A. grebnitzkii the number of females significantly exceeds the number of males (the percentage of females varies from 53% in September to 98.7% in June with an overall mean of 75%). In the study area, A. grebnitzkii breeds from May to August. The diurnal dynamics previously espoused in literature have been affirmed in that A. grebnitzkii and E. schmidti presides during the night, unlike at day. Additionally, the distribution of the two key dominant benthic species in the intertidal zone are shown here to prefer the lower littoral regardless of high or low tide, in good agreement with previous literature findings.

Keywords

• abundance
• Bering Sea
• biomass
• nature reserve
• North Pacific