Decadal Stability of Macrobenthic Zonation along the Estuarine Gradient in the Ob Bay, the Largest Siberian Estuary

Abstract

The Siberian Arctic Shelf is an area of increasing anthropogenic activity and is predicted to be significantly impacted by climate change. Accordingly, there is an increased demand for baseline knowledge on the scales of natural spatiotemporal variation of different ecosystem components. The study aimed to investigate the spatial variability of macrobenthic communities and associated abiotic forcing in the Ob Bay, a major Arctic estuary. Four main zones of macrobenthic communities were identified: a brackish-water zone in the upper part of the estuary, which was divided into two subzones according to the dominant species; a transition zone at the mouth of the Ob Bay; and a marine zone. This zonation remained stable during the study period (2013–2019) and corresponded well with previous studies in the area. The large-scale variation in macrobenthic communities was related mainly to two independent drivers: salinity and sediment type. The within-zone variation increased with the number of coexisting species, but no temporal trends could be assessed. The study highlights the need to account for the small-scale heterogeneity of benthic communities to understand ecosystem functioning and long-term dynamics, particularly in areas where environmental conditions vary markedly.