不同珊瑚对酸化、苯并[a]芘单一和复合胁迫的生理响应

Physiological Responses of Different Corals under Single and Combined Stress of Acidification and Benzo[a]pyrene

海洋酸化和持久性有机污染物的排放对珊瑚礁生态系统的健康具有负面影响。为阐明酸化、苯并[a]芘(benzo[a]pyrene,BaP)单一及复合胁迫对2种不同形态珊瑚共生虫黄藻光合生理指标和抗氧化酶活性的影响,本研究以澄黄滨珊瑚(Porites lutea)和多孔鹿角珊瑚(Acropora milllepora)为研究对象,分析了不同胁迫处理(酸化、BaP胁迫、酸化与BaP复合胁迫)对2种珊瑚的共生虫黄藻密度、叶绿素a含量以及抗氧化酶活性的毒性效应。研究结果显示,单一酸化胁迫(pH=7.8)下,多孔鹿角珊瑚共生虫黄藻密度、叶绿素a含量和超氧化物歧化酶(SOD)酶活性呈显著下降(P<0.01),过氧化物酶(POD)酶活性显著上升(P<0.01);澄黄滨珊瑚共生虫黄藻密度、叶绿素a含量无显著变化,SOD、POD酶活性显著下降(P<0.01)。单一BaP(10μg·L^(-1))胁迫下,多孔鹿角珊瑚共生虫黄藻的密度、叶绿素a含量显著下降(P<0.01),SOD、POD酶活性无显著变化;澄黄滨珊瑚共生虫黄藻密度无显著变化,叶绿素a含量显著下降(P<0.01),SOD、POD酶活性明显升高(P<0.01);在海水酸化复合BaP胁迫下,多孔鹿角珊瑚的共生虫黄藻叶绿素a含量、SOD酶活性显著下降(P<0.01),澄黄滨珊瑚共生虫黄藻密度显著升高(P<0.05),POD酶活性显著下降(P<0.01)。研究结果表明,珊瑚对不同环境的胁迫响应存在种间差异,多孔鹿角珊瑚较澄黄滨珊瑚更加敏感;珊瑚共生虫黄藻叶绿素a含量变化更适合作为海洋酸化、BaP胁迫的指示因子。

The health of coral reef ecosystem has been negatively impacted by ocean acidification(OA)and the discharge of persistent organic pollutants(benzo[a]pyrene,BaP).In order to elucidate the individual and combined effects of OA and BaP on the algal photo-physiology and antioxidant system of coral holobionts,we measured the Symbiodiniaceae density and chlorophyll a content,as well as antioxidant enzyme activities of holobionts in two reef-building corals,Acropora milllepora and Porites lutea,respectively.The results showed that OA(pH=7.8)caused a significant decrease in Symbiodiniaceae density,chlorophyll a content,and superoxide dismutase(SOD)activity,but a significant increase in peroxide(POD)activity(P<0.01)in A.millepora,whereas no significant variation in two algal photo-physiological indexes and a significant decrease(P<0.01)in SOD and POD activities of P.lutea.An exposure of 10μg·L^(-1)induced significant decrease in Symbiodiniaceae density and chlorophyll a content(P<0.01),but there has no significant change in SOD and POD activities of A.millepora.Additionally,chlorophyll a content significantly decreased(P<0.01),but SOD and POD activities were significantly elevated in P.lutea(P<0.01).Under combined stressors exposure,the chlorophyll a content and SOD activity significantly declined(P<0.01)in A.millepora,while Symbiodiniaceae density significantly increased(P<0.05)in P.lutea accompanied with significantly decreased POD activity(P<0.01).Our findings suggested that A.millepora is more sensitive than P.lutea to the environmental stress.The chlorophyll a content appears suitable as the bio-indicator to monitor ocean acidification and BaP pollution.