Acute Toxicity of Ammonia to Larval Penaeus Japonicus

Abstract

Chlorination to eliminate fouling organisms in the cooling system of acoastal power plant may cause undesirable effect on milkfish(Chanos chanos)larvae in the nearby fry collecting area.This study was to find out the effectof residual chlorine on the mortality of milkfish larvae under various temperatureand salinity regimes.Milkfish larvae of two stages,namely 8(H8)and17(H17)days after hatching were exposed to combinations of five chlorineconcentrations(0.924 to 1.596 mg/l)at three temperatures(26°to 34℃)andthree salinities(26 to 34 ppt)for one hour.Up to second order multipleregression models were constructed to evaluate and compare the resistance ofmilkfish to chlorine at both stages under environment of various chlorineat both stages under environmentment of various chlorine concentration(C),temperature(T),and salinity(S).The resulted optimal models were:Sin^(-1)M^(1/2)=-1.3501+2.7089×10^(-2)×S×C+2.7612×10^(-2)×T×CSin^(-1)M^(1/2)=-1.7616+3.7605×10^(-2)×S×T+4.3621×10^(-2)×T×Cfor H8 and H17 stage,respectively.From these models the average one hourLC(subscript 50)s(mg/l)were 1.3092 and 1.7112 for H8 and H17,respectively.For bothstages,mortality increased with chlorine concentration.Both temperatureand salinity had synergistic effect on chlorine toxicity for H8 stage.Onlytemperature had synergistic effect on chlorine toxicity for H17 stage.Duringthe milkfish larva collecting season,chlorine concentration of the effluentfrom power plant should be kept below 0.066-0.085 mg/l to avoid the impacton milkfish larvae.在沿海發電廠冷却系統加氯來去除附著生物其殘留氯可能會對附近虱目魚苗捕撈區造成不良影響。此研究在找出殘留氯在不同溫度及鹽度狀況下對虱目魚苗死亡率之影響。兩期的虱目魚苗：孵化後8天(H8)及17天(H17)浸在5種氯濃度（0.924～1.596 mg/l）在3種溫度（26～34℃）及3種鹽度（26～34 ppt）下1小時。所求得之二元多項廻歸模式被用來比較及評估兩期的苗在不同氯濃度(C)，溫度(T)及鹽度(S)狀况下對氯的忍受力，對H8及H17苗的最適模式分别如下：sin^(-1)M^(1／2)=-1.3501+2.7089×10^(-2)×S×C+2.7612×10^(-2)×T×Csin^(-1)M^(1／2)=-1.7616+3.7605×10^(-4)×S×T+4.3621×10^(-2)×T×C從這些模式H8及H17苗，一小時平均LC50分别爲1.3092及1.7112 mg/1。對此兩期，死亡率都隨著氯濃度增加，對H8苗溫度及鹽度對氯毒性有加成影響，對H17苗僅溫度對氯毒性有加成影響。在虱目魚苗捕撈期間，發電廠排放水氯濃度應保持在0.066～0.085 mg/l以下，來避免對虱目魚苗的衝擊。