大亚湾鱼类深水网箱养殖对环境的影响

2016年5月(养殖开始前)和2016年8月(养殖投饵高峰期)对大亚湾大碓鱼类深水网箱区、外围区(网箱外0.1 km)和非养殖区(网箱外10~15 km)的海水和沉积环境进行了调查,采用有机污染指数(A)法、营养状态质量指数(NQI)法对水环境进行评价,用潜在生态危害指数(RI)法对表层沉积物重金属潜在生态危害进行评价。结果显示,与传统网箱养殖化学需氧量(COD)由网箱区中心向四周递减的趋势不同,深水网箱养殖CODMn浓度在3个区域间无显著性差异。深水网箱养殖海域水质较好(A1),水质处于贫营养水平(NQI2)。深水网箱养殖海域表层沉积物重金属铅(Pb)和锌(Zn)含量均符合第一类海洋沉积物质量标准,但铜(Cu)和镉(Cd)含量轻微超标。沉积环境处于轻微生态危害状态(Eir30,RI100),与中国同类型海区相比,污染危害程度相对并不严重。深水网箱养鱼对周围海域环境的影响较小。

Impact of deep-water net cage fish farming in Daya Bay,southern China on environment

We investigated the seawater and sediments in a deep-water net cage area in Dadui,southwest Daya Bay,to assess the impact of farming activities on the ambient environment.The water and sediment samples were collected from cage culture ar ea,surrounding area (located ca.0.1 km from the nearest farming cage) and non-culture area (where no culture activities were practiced,located ca.10 ～ 15 km from the nearest farming cage) in May (before the farming) and August 2016 (the most feeding activities and metabolism of cultured fish),respectively.The water environment was assessed using organic pollution in dex (A) and nutrient quality index (NQI),while the heavy metals potential ecological risk in surface sediment was assessed using potential ecological risk index (RI).The results show no significant difference of CODMn concentration among the three areas of deep-water net cage farming,while COD of the traditional cage farming showed a decreasing trend from the center to the surrounding of the cage area.The A value (＜ 1) of cage culture area indicates that the water quality was in a general condition,and the relatively low NQI value (＜ 2) indicates that the water quality was in a relatively poor nutrient condition.The contents of heavy metals in surface sediments of cage area were lower than the marine sediment quality standards Class Ⅰ except for those of Cu and Cd.The Eir value (＜ 30) and RI value (＜ 100) were relatively low,compared with many other culture areas in China,which indicates that the surface sedimentary environment of deep-water net cage area in Daya Bay is in slight ecological harm.It is suggested that the influence of deep-water net cage fish farming on the ambient water and sedimentary environment is relatively low or acceptable..