东山八尺门海堤西侧网箱养殖海域营养状态初探

A preliminary study of nutrient condition in cage culture waters west to the Bachimen Bank, Dongshan

本文根据1989年10月和1990年4月在福建东山县八尺门海堤西侧网箱养殖海域现场调查获得的海水化学、浮游植物、叶绿素a等资料,以有机污染指数和营养状态指数为指标,研究了该海域的营养状态,结果表明:1989年4月中旬,该海域有机污染严重,富营养化程度高。底层水呈低氧或无氧状态。推测10月9日夜间网养鱼大量死亡的主要原因是水体缺氧状态加剧所致。

Based on the field survey data of sea-water chemistry, phytoplankton, chlorophyl a, and others obtained in the cage culture waters west to the Bachimen Bank, Dongshan ,Fujian during the period from October, 1989 to April, 1990,the nutrient condition was studied with organic pollution index and nutrient condition index as research indices. The results show that : in the second ten days of October, 1989,the organic pollution index A was between 4.99～19.56,the nutrient condition index E 15.66～34.32, the bottom sulfide mass fraction 0.66×10^(-3)～3.01×10^(-3),the dissolved oxygen volume fraction 0～8.51×10^(-3),the chlorophyl a 3.75～29.83μg/L,the red tide organism Thalassiosira weissflogii 12×10~6ind./L. Up to April, 1990, the A value and E Value by average, were still 13.65 and 9.04 respectively.Serious organic pollution and higher level of eutrophication were caused by both continuous over feeding and poor hydrodynamic conditions. The author infer that the 5.2t cage cultured fishes died over night in October, 1989 was caused by serious oxygen deficit due to eutrophication in the sea area.