LAUSR

Integrated Multi-Trophic Aquaculture (IMTA) is an effective method for sustainable aquaculture as species from different trophic levels could reduce negative effects from fed species in the environment. A proper proportion of different trophic species in an IMTA system could improve the aquaculture production and environmental sustainability. At present, research on the proper proportions for farming species is scarce. We investigated the effects of IMTA modes of oyster ( Crassostrea gigas ) and kelp ( Saccharina japonica ) in different weight ratios on water quality and carbonate system in a closed enclosure experiment for three days in the Sanggou Bay in Shandong Province, China, in December 2017. Nine collocation modes in oyster:kelp weight ratio were tested showing as 24:3, 24:2, 24:1, 16:3, 16:2, 16:1, 8:3, 8:2, and 8:1. The water parameters were determined at 17:00 on Day 1 (D1), and 6:00 and 17:00 on Days 2 (D2) and 3 (D3). As two-way ANOVA showed, all increased parameters (dissolved oxygen (DO), pH, chl a , the carbonate system and p CO 2 ) were significantly related to oyster-kelp modes, and interaction between modes and time were also significant ( P <0.05). On the 3 th day, the 8:3 mode was the highest in DO, pH, chl a , CO 3 2− ( P <0.05), and dissolved inorganic carbon (DIC), HCO 3 − , CO 2 and p CO 2 were the lowest ( P <0.05). According to previous references and the results of this study, the appropriate oyster:kelp proportion at the beginning of winter is from 8:2 to 8:3. The results of this study may help government to optimize the aquaculture structure of Sanggou Bay.