Analysis of the Air-Sea Surface Carbon Dioxide Flux and Its Interaction with Aquaculture Activities in Sanggou Bay

Abstract:

To study the impact of different aquaculture activities on the air-sea carbon dioxide flux (F), a cruise research was carried out in May, 2014 in Sanggou Bay, the most representative area of integrated multi-trophic aquaculture in northern China. During the study, the partial pressure (pCO2) of the surface sea water was measured using the pCO2 underway system (OceanPack, SubCtech Co., German). The CO2 flux of the Sanggou Bay was evaluated through following parameters. Twenty-four hours monitoring was set up and performed in the caging culture area, bivalves culture area and kelp culture areas. Furthermore, the in situ hydrodynamic, chemical, biological and culture conditions, the impact factor of the air-sea CO2 flux in Sanggou Bay in spring were discussed. The results showed that the pCO2 in cage culture areas was much higher than the other culture areas. The F value was (–1.02±0.83) mmol/(m2·d) in bivalves culture area, (–15.40±1.28) mmol/(m2·d)in kelp culture area, (–4.32±1.41) mmol/(m2·d) in bivalves-kelp culture area, and 8.14 mmol/(m2·d) in cage culture area. The continuous 24 h observation showed that the average values of pCO2 in kelp, bivalves and cage culture area were (320±14) μatm, (330±10) μatm, (413± 37) μatm, respectively. The results showed that the Chl-a value was one of the key factors for the air-sea carbon-dioxide flux F, with significant differences in F value among different culture areas. The F value was negative in the bivalves, kelp and bivalves-kelp multi-culture areas, which means these areas 'sank' or absorbed the atmospheric CO2. By contrast, F value in cage culture area was positive, which indicated that it was a 'source' or producer of the atmospheric CO2.