Degradation and recovery of an Arctic benthic community under organic enrichment

Fast development of mariculture in the world leads to increasing of the load on natural habitats, especially due to organic enrichment. There are a few investigations concerning the effect of additional organic loading on the Arctic benthic communities. The main goal of our research was to ascertain the impact of mussel farm on the benthic community in the White Sea and its following recovery after mussel farm removal. We performed annual observations from 1988 to 2011. During the mussel farm functioning, two stages of organic enrichment impact on community structure were recorded: in the first 2 years, diversity and proportion of deposit feeders increased but later all studied characteristics of the benthic community decreased significantly. After the mussel farm removal, the benthic community started to restore and we distinguished several stages of recovery succession. Native structure of benthic community began to recover 8 years after organic loading had ceased, when selective deposit feeding bivalves Portlandia arctica Gray appeared in the benthos. 4-6 years later it became the only dominating species in the studied benthic community. Therefore, in the White Sea, native structure recovery of the Arctic benthic community after the severe disturbance took about 15 years.