Diverse nature of the seasonally coastal eutrophication dominated by oceanic nutrients: An eco-system based analysis characterized by salmon migration and aquaculture.

Previously, studies of coastal eutrophication have usually focused on the nutrients input from adjacent land sectors, such as rivers, submarine-ground discharges, and atmospheric depositions. Here we report two examples of well-managed seasonal eutrophication phenomena in coastal marine environments, where nutrients come predominantly from offshore: one by humans and the other by nature (higher trophic animals). In the Sanggou Bay of North China, the total amount of incoming nutrients from the open Yellow Sea is taken up by seaweeds. Seaweed, in turn, supports bivalves culture activities and absorbs nutrients emitted by finfish. In the Academy Bay of Russian Far East, a relatively high plankton primary production sustains throughout the salmon-returning season when nutrients are released from the massive carcasses of dead fish after return from the ocean to their natal streams to spawn and die. This high plankton productivity, in turn, fuels higher trophic ecosystem constituents, including whale populations of global importance. In the future, dominance of nutrients from marine sources needs to be seriously considered in studies of coastal eutrophication.