State of the benthic communities in the Novaya Zemlya archipelago bays (Kara Sea) in 2020

In 2020, the bottom communities of Rusanov Bay were studied for the first time and repeated benthic surveys were conducted in Blagopoluchiya and Tsivolki Bays (Novaya Zemlya archipelago, Kara Sea). Mass extinction of adult populations of the bivalve Portlandia arctica, which was dominant in 2013–2016, was noted in the inner parts of the bays. In all tree bays, the main share of the benthos in 2020 consisted of bivalves Mendicula ferruginosa and juveniles of Ennucula tenuis, Portlandia arctica, Yoldiella spp. In Rusanov Bay, the number of small and juvenile bivalves was the highest and reached 2900 ind/m2 (92% of the total density). The high proportion of juveniles indicates instability of benthos and should lead to rapid transformation of inner bay communities over the next years. Environmental variability (terrestrial runoff, sedimentation, temperature characteristics of the bottom layer) and the invasion of the snow crab Chionoecetes opilio can be proposed as the reasons for the benthic community changes.