不同单养及混养海水实验围隔水化学的研究

STUDIES ON WATER CHEMISTRY OF SEAWATER EXPERIMENTAL ENCLOSURES WITH DIFFERENT MONOCULTURE AND POLYCULTURE

1995年 6～ 10月和 1996年 6～ 8月对不同单养和混养海水实验围隔的水化学研究结果表明 :围隔中盐度、总氮、总磷和化学耗氧量 (COD)在雨季前逐渐升高 ,进入雨季后降低 ;投饵养殖时围隔中磷浓度较低氮浓度较高 ,其中混养中国对虾与台湾红罗非鱼的围隔活性磷 (PO4 -P)浓度相对较高 ,混养对虾与菲律宾蛤仔的围隔氨氮 (NH3 -N)浓度较高 ,投饵兼酌情施肥养殖时围隔中氮浓度较低磷浓度较高 ,其中混养中国对虾与缢蛏的围隔NH3 -N较高 ;两年实验中混养贝类的围隔COD通常较低。实验结果显示人工投饵和施肥是围隔水化学环境变动的主要原因 ,混养罗非鱼或贝类对围隔水化学也会产生一定的影响。

Two enclosure experiments were carried out from June to October in 1995 and June to August in 1996 to evaluate the effect of different types of monoculture or polyculture on water chemistry in enclosures. The results showed that concentration of total nitrogen and total phosphorus, chemical oxygen demand, and salinity increased before rainy season then dropped rapidly after rain. When only feed was adopted,the concentration of reactive phosphate and total phosphorus was relatively low and the concentration of nitrite, nitrate, ammonia and total nitrogen was high. When both feed and fertilizer was provided,the concentration of nitrite, nitrate, ammonia and total nitrogen was low and the concentration of reactive phosphate and total phosphorus was high. Concentration of reactive phosphate was usually higher in enclosures stocked with hybrid tilapia, Oreochromis mossambicus×O. niloticus, while the concentration of ammonia was higher in enclosures stocked with Ruditapes philippinarum or Sinonvacula constricta. Chemical oxygen demand in present experiments was not as high as that usually reported in freshwater fishponds or seawater shrimp ponds, and much lower in those enclosures stocked with bivalves. Present experiments suggest that water chemistry in experimental enclosures was mainly dependent on daily management activities such as feeding and fertilizing, and partly influenced by stocked shrimp, tilapia and bivalves at the same time.