Intensive mariculture results in a rise in nutrient concentrations, then leads to serious eutrophication in
coastal waters. Based on the sampling data obtained between August 2012 and July 2013, the eutrophication
status in Yantian Bay was assessed, and the proportion of marine animals co-cultured with seaweeds
was evaluated. The nutritional quality index (NQI) ranged from 4.37 to 13.20, indicating serious
eutrophication conditions. The annual average ratio of nitrogen/phosphorus (N/P) was 25.19, indicating
a nitrogen surplus in this system. DIN was selected as the best parameter to balance seaweed absorption
and marine animal DIN production. Gracilaria lemaneiformis and Laminaria japonica were selected as cocultured
seaweeds. The optimal proportion of G. lemaneiformis production was assessed as 20074.14
tonnes. The optimal proportion of L. japonica production was evaluated as 15890.68 tonnes. High-temperature
adapted seaweeds should be introduced for removing nutrients releasing by farmed aquatic animals
in the summer in Yantian Bay.