桑沟湾春季海–气界面CO2交换通量及其与养殖活动的关系分析

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

关键词:  桑沟湾  交换通量  CO2分压  海水养殖

Key words:  Sanggou Bay  Sea-air flux  pCO2  Mariculture

摘要:

为研究不同养殖活动对海–气界面CO2交换通量(F)的影响，于2014年5月采用走航式CO2分压仪对中国北方典型的多营养层次混合养殖海域—桑沟湾养殖区的表层水CO2分压(pCO2)进行了大面调查，并通过数据计算桑沟湾海区的F值。在调查过程中，选择在网箱养殖区、贝类养殖区、藻类养殖区等区域内进行24 h定点连续观测。探讨了春季桑沟湾海–气界面CO2的交换通量及其主要影响因素。大面调查结果显示，桑沟湾内海水中pCO2总体变化趋势是由湾内向湾外递减，网箱养殖区海水中pCO2远远高于其他区域。在大面调查中，贝类、藻类、贝藻混养、网箱养殖区的F值分别为(–1.02±0.83)、(–15.40±1.28)、(–4.32±1.41)、8.14 mmol/(m2·d)。定点连续监测显示，藻类、贝类、网箱养殖区的pCO2 24 h平均值分别为(320±14)、(330±10)、(413±37) μatm。研究表明，光合作用是海–气界面CO2交换通量的主要影响因素之一，不同养殖区之间的海–气界面CO2交换通量差异显著。影响各养殖区海–气界面CO2交换通量日变化规律的影响因子与走航调查结果一致。养殖活动是影响海–气界面CO2交换通量的主导因素。

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.