This study was conducted to investigate the effects of temperature, pH, ammonia nitrogen content and salinity on the bleaching of Acropora millepora and Palythoa sp. This study included two experiments ： Experiment 1...This study was conducted to investigate the effects of temperature, pH, ammonia nitrogen content and salinity on the bleaching of Acropora millepora and Palythoa sp. This study included two experiments ： Experiment 1 was designed to test the effects of different gradients of temperature, pH, ammonia nitrogen con- tent and salinity at a time point （6h） on Palythoa sp. breeding; and Experiment 2 tested the effects of different levels of temperature, pH, ammonia nitrogen con- tent and salinity at three time points （24, 48 and 72h） on A. millepora bleaching. Before the experiments, A. millepora and Palythoa sp. were washed with filtered seawater （0.45 p,m microporous membrane filtration） and then reared in interior seawater aquurium cylinder. The experiments were carried out when the coral ten- tacles extended and the growth condition were good. The results showed that under high temperature （32 -40 ~C ） , both A. millepora and Palythoa sp. showed drastic reactions in the course of time, reflecting considerably significant stress responses. The number of releasing zooxanthellae increased with increase or de- creaseof the pH value （pH 0, 4, 6, 10, 12） over time. Meanwhile, a relatively thick layer of mucus was found on the upper zone of the seawater and the corals started to bleach. As the concentration of ammonia nitrogen （ NH4 , 0 mmool/L） increased in the course of time, the number of zooxanthellae floating on A. millepo- ra and Palythoa sp. had the tendency to rise. When the salinity level were at 15%o and 40%o for A. miUepora and below 34‰ for Palythoa sp. , a considerable number of zuoxanthellae floated out and had rising trend in their number over time at 24 -72 h and 6 h, respectively. In this occasion, the corals stopped growing and started to bleach. In conclusion, it revealed that temperature, pH, ammonia nitrogen content and salinity are the potential impact factors on coral breeding. It is suggested that, as temperature, pH value and salinity decrease or increase, as well as anmlonia nitrogen content rises, the quantity of phycobiont would be raised, and the bleaching would be more severe.展开更多
Coral bleaching, which is defined as the loss of colour in corals due to the loss of their symbiotic algae (commonly called zooxanthellae) or pigments or both, is oc-curring globally at increasing rates, and its harm ...Coral bleaching, which is defined as the loss of colour in corals due to the loss of their symbiotic algae (commonly called zooxanthellae) or pigments or both, is oc-curring globally at increasing rates, and its harm becomes more and more serious during these two decades. The sig-nificance of these bleaching events to the health of coral reef ecosystems is extreme, as bleached corals exhibited high mortality, reduced fecundity and productivity and increased susceptibility to diseases. This decreased coral fitness is easily to lead to reef degradation and ultimately to the breakdown of the coral reef ecosystems. Recently, the reasons leading to coral bleaching are thought to be as follows: too high or too low temperature, excess ultraviolet exposure, heavy metal pollution, cyanide poison and seasonal cycle. To date there has been little knowledge of whether mariculture can result in coral bleaching and which substance has the worst effect on corals. And no research was conducted on the effect of hypoxia on corals. To address these questions, effects of tem-perature, hypoxia, ammonia and nitrate on bleaching of three coral species were studied through examination of morphology and the measurement of the number of symbi-otic algae of three coral species Acropora nobilis, Palythoa sp. and Alveopora verrilliana. Results showed that increase in temperature and decrease in dissolved oxygen could lead to increasing number of symbiotic algae and more serious bleaching. In addition, the concentration of 0.001 mmol/L ammonia or nitrate could increase significantly the expulsion of the symbiotic algae of the three coral species. Except for Acropora nobilis, the numbers of symbiotic algae of other two corals did not significantly increase with the increasing con-centration of ammonia and nitrate. Furthermore, different hosts have different stress susceptibilities on coral bleaching.展开更多
基金Supported by Major Science and Technology Projects in Hainan Province from Science and Technology Department of Hainan Province Government,China(ZDKJ2016013ZDKJ2016009)+1 种基金Hainan Key laboratory for Conservation and Utilization of Tropical Marine Fishery ResourcesKey Laboratory of Seawater Aquaculture Research of Sanya City(L1507)
文摘This study was conducted to investigate the effects of temperature, pH, ammonia nitrogen content and salinity on the bleaching of Acropora millepora and Palythoa sp. This study included two experiments ： Experiment 1 was designed to test the effects of different gradients of temperature, pH, ammonia nitrogen con- tent and salinity at a time point （6h） on Palythoa sp. breeding; and Experiment 2 tested the effects of different levels of temperature, pH, ammonia nitrogen con- tent and salinity at three time points （24, 48 and 72h） on A. millepora bleaching. Before the experiments, A. millepora and Palythoa sp. were washed with filtered seawater （0.45 p,m microporous membrane filtration） and then reared in interior seawater aquurium cylinder. The experiments were carried out when the coral ten- tacles extended and the growth condition were good. The results showed that under high temperature （32 -40 ~C ） , both A. millepora and Palythoa sp. showed drastic reactions in the course of time, reflecting considerably significant stress responses. The number of releasing zooxanthellae increased with increase or de- creaseof the pH value （pH 0, 4, 6, 10, 12） over time. Meanwhile, a relatively thick layer of mucus was found on the upper zone of the seawater and the corals started to bleach. As the concentration of ammonia nitrogen （ NH4 , 0 mmool/L） increased in the course of time, the number of zooxanthellae floating on A. millepo- ra and Palythoa sp. had the tendency to rise. When the salinity level were at 15%o and 40%o for A. miUepora and below 34‰ for Palythoa sp. , a considerable number of zuoxanthellae floated out and had rising trend in their number over time at 24 -72 h and 6 h, respectively. In this occasion, the corals stopped growing and started to bleach. In conclusion, it revealed that temperature, pH, ammonia nitrogen content and salinity are the potential impact factors on coral breeding. It is suggested that, as temperature, pH value and salinity decrease or increase, as well as anmlonia nitrogen content rises, the quantity of phycobiont would be raised, and the bleaching would be more severe.
文摘Coral bleaching, which is defined as the loss of colour in corals due to the loss of their symbiotic algae (commonly called zooxanthellae) or pigments or both, is oc-curring globally at increasing rates, and its harm becomes more and more serious during these two decades. The sig-nificance of these bleaching events to the health of coral reef ecosystems is extreme, as bleached corals exhibited high mortality, reduced fecundity and productivity and increased susceptibility to diseases. This decreased coral fitness is easily to lead to reef degradation and ultimately to the breakdown of the coral reef ecosystems. Recently, the reasons leading to coral bleaching are thought to be as follows: too high or too low temperature, excess ultraviolet exposure, heavy metal pollution, cyanide poison and seasonal cycle. To date there has been little knowledge of whether mariculture can result in coral bleaching and which substance has the worst effect on corals. And no research was conducted on the effect of hypoxia on corals. To address these questions, effects of tem-perature, hypoxia, ammonia and nitrate on bleaching of three coral species were studied through examination of morphology and the measurement of the number of symbi-otic algae of three coral species Acropora nobilis, Palythoa sp. and Alveopora verrilliana. Results showed that increase in temperature and decrease in dissolved oxygen could lead to increasing number of symbiotic algae and more serious bleaching. In addition, the concentration of 0.001 mmol/L ammonia or nitrate could increase significantly the expulsion of the symbiotic algae of the three coral species. Except for Acropora nobilis, the numbers of symbiotic algae of other two corals did not significantly increase with the increasing con-centration of ammonia and nitrate. Furthermore, different hosts have different stress susceptibilities on coral bleaching.
