菲律宾蛤仔对急性海水酸化和重金属(Cu和Cd)胁迫的生理响应

Physiological Response of Ruditapes philippinarum to the Acute Stress of Seawater Acidification and Heavy Metal(Cu and Cd)Incubation

为研究海水酸化和重金属污染物对滩涂贝类的联合影响,采用静态急性毒性实验方法,以自然海水(pH 8.2)为对照,研究了不同酸化条件下(pH 7.7和7.3),菲律宾蛤仔(Ruditapes philippinarum)耗氧率(OR)、滤水率(FR)和心率对重金属Cu(0、0.06和0.60 mg/L)和Cd(0、0.03和0.30 mg/L)胁迫的生理响应。结果显示,Cu胁迫显著降低了蛤仔的OR和FR(P<0.05),随胁迫时间的延长,蛤仔心率显著下降(P<0.05)。Cd胁迫对蛤仔OR和FR无显著影响(P>0.05),但在0.30 mg/L Cd胁迫下,随着时间的增加,蛤仔心率显著升高(P<0.05)。pH 7.7和7.3两种酸化胁迫对蛤仔的OR和FR无显著影响(P>0.05),但在pH 7.3的海水中,蛤仔心率出现短暂下降并快速恢复的现象。研究表明,蛤仔短期暴露于Cu、Cd或酸化海水中均会影响其生理功能,影响程度排序为Cu>Cd>pH。实验中未发现短期海水酸化与Cu或Cd对菲律宾蛤仔存在联合毒性效应。本研究分析了菲律宾蛤仔响应海水酸化和重金属胁迫的机制,同时探讨了把贝类心率作为环境胁迫指标的可行性。

Intertidal bivalves experience broad fluctuations of abiotic factors including pH,salinity and temperature,which could affect their physiology and biochemistry.They are also exposed to trace metals such as copper(Cu)and cadmium(Cd)that accumulate in their tissues and may negatively affect respiration and cardiac activity.Therefore,understanding the impact of pH and heavy metals on intertidal bivalve physiology is of prime importance especially in the context of global ocean acidification.We determined the interactive effects of low pH(7.7 and 7.3)and the addition of heavy metals(Cu or Cd)on the physiological functions including oxygen consumption rate(OR),filtration rate(FR)and heart rate of a common intertidal bivalve,Ruditapes philippinarum.The experiment was conducted under laboratory conditions with pH 8.2 as the control treatment.Addition of Cu at concentrations of 0.06 and 0.60 mg/L suppressed OR,FR,and heart rate(P<0.05).The clams’heart rate decreased from 23.8 bpm(beats per minute)to 10.5 bpm after being exposed to 0.06 mg/L Cu for 20 min.No significant effect of Cd(0.03,0.30 mg/L)was found on OR or FR(P>0.05),however clams incubated in the 0.30 mg/L Cd group had a significantly higher heart rate(39.0 bpm)than the control(25.3 bpm)(P<0.05).Low pH had no effect on OR and FR(P>0.05),but clams´heart rate in the pH 7.3 treatment decreased at the beginning of incubation and recovered rapidly.Our findings suggest that short-term exposure to Cu,Cd,or low pH,all impact the cardiac activity of clams,and the order of toxicity was Cu>Cd>pH.Heart rate was a more sensitive endpoint than OR and FR.There were no interactive effects of low pH and Cu or Cd on the respiration of clams.Our study provides referential data for studying the response of intertidal bivalves to heavy metal exposure and ocean acidification,which may be helpful in the prevention and biological reparation of potential heavy metal pollution in coastal areas.