Pelagic Food Chain of the Bering Sea

The order of magnitude of biomass and production at various trophic levels in the epipelagic community has been calculated, and the main pathways for the transformation of matter and energy in the Bering Sea have been identified. For each group of aquatic organisms, the average indicators of biomass, production, and grazing (feeding) consumption were estimated. According to long-term average data (1986–2020), 1054.7 million tons C/year of organic matter was produced in epipelagic zone of the Bering Sea at the 1st trophic level, 120.4 million tons C/year, at the 2nd trophic level, 20.7 million tons C/year, at the 3rd trophic level, 0.93 million tons C/year, at the 4th one, 0.015 million tons C/year, at the 5th level. The annual production of aquatic organisms in the epipelagic zone of the Bering Sea is exceeds 1 billion tons C/year (1196.8 million tons C/year) or 21.4 billion tons of wet weight. Excluding primary production, which is 72.6% of gross production in carbon equivalent, microheterotrophs (15.5%) and dominant zooplankton groups (copepods—7.3%, euphausiids—1.9%, chaetognaths—1.1%, and hyperiids—0.5%) contribute most significantly to annual production. The contribution of the functional groups of the nekton (pollock Gadus chalcogrammus, squid, salmon, and mesopelagic fish) is approximately 1–2 orders of magnitude lower. Altogether, the share of the heterotrophic part of the biocenosis in the epipelagic zone of the Bering Sea accounts for about 27% of production. The powerful development of representatives of the 2nd trophic level (mainly copepods and, to a lesser extent, euphausiids) suggests that the level of grazing pressure from planktonic and nektonic predators may be higher. The forage base of the Bering Sea is capable of providing food for nekton stock exceeding the current level. This conclusion is important from the standpoint of the development of grazing aquaculture of valuable pelagic fish, including salmon.