The Stress Of NO₃^-、NH₄⁺ And PO₄^3- On Corals

The study focused on Goniopora stutchburyi, Goniopora duofasciata and Porites lutea.Under laboratory conditions studied effects of different concentrations of N,P on corals,clarified the effects of entrofication on catlase and superoxide dismutase enzymes, growth of corals and symbiotic algal, the restoration of indicators in corals, provided theory basis for the degradation of coral reef ecosystem restoration and reconstruction. The main results were as follows:1 The effects of NO₃^- 、 NH₄⁺ and PO₄^3- on catalase and superoxidase dismutase enzyme activities of coralsThe effects of different concentrations nitrate, ammonium and phosphate on catalase（CAT） and superoxidase dismutase（SOD） enzymatic activity of G. stutchburyi, G.duofasciata and P. lutea were investigated for 8 weeks, respectively, three levels were set as follows: low, medium and high level. Results indicated that The results indicated that activities of CAT in G. stutchburyi exposed to medium concentration of nitrate and ammonium, activities of SOD exposed to high concentrations of nitrate and phosphate and to medium concentrations of ammonium reached the highest; Activities of CAT in G.duofasciata exposed to medium concentration of nitrate, ammonium and phosphate,activities of SOD exposed to medium concentrations of nitrate and ammonium and to high concentrations of phosphate reached the highest; Activities of CAT and SOD in P. Lutea with control group reached the highest,it showed poor tolerance to nutrients; CAT and SOD in G. stutchburyi, G. duofasciata and P. lutea had peaks, and there were significant differences in enzymatic activity among different time points（P<0.05）.It was the critical value from adaptation to toxic reaction under stress of nutrients.2 The effects of NO₃^-,NH₄⁺and PO₄^3- on growth of corals and symbiotic algalUnder condition of laboratory,the study focused on the effect of NO₃^-、NH₄⁺ and PO₄^3- on growth and symbiotic algae in G. stutchburyi, G. duofasciata and P. lutea. The results indicated that each index reached the highest in the early time.Under the same nutrient concentration, with time went by, the growth rate increased then decreased or decreased all the time. Content of chlorophyll a and zooxanthella density decreased gradually, there were significantly difference between them（P<0.05）.（1） nitrate, the growth rate of G. stutchburyi, G. duofasciata and P. lutea. respectively exposed to control group, medium group（20.51μmol/L） and in the early time exposed to mediumconcentration then low concentration16.45μmol/L) reached the highest, Content of chlorophyll a and zooxanthella density of control group reached the highest.（2） ammonium,the growth rate of G. stutchburyi, G. duofasciata and P. lutea. respectively exposed to control group, low concentration group（3.95μmol/L） and low concentration group, in the early time, Chl-a of the high concentration, lately, control, medium concentration（9.81μmol/L） and low concentration group respectively reached the highest,zooxanthella density of high concentration group reached the highest.（3） phosphorus, the growth rate of G. stutchburyi, G. duofasciata and P. lutea. respectively exposed to control group, mediunm concentration（7.31μmol/L） group reached the highest, early, Chl- a of high concentration group, latterly, respectively the low concentration group, low concentration group and medium concentration group reached the highest, zooxanthella density of control group reached the highest. It indicated that in early time adaptation mechnisms were not damaged, latterly, they were damaged deeply, the level of each index were lower than control group, under high nutrient concentration growth rate were inhibated, the index of Chl-a and zooxanthella density were sensitive, were more suitable for being the indictive index of environment, was conducive to evaluate the suitable nutrient concentration of corals.3 Recoveration of corals after NO₃^-、NH₄⁺ and PO₄^3- stressThe study focused on recoveration of corals after NO₃^-、NH₄⁺ and PO₄^3- stress, under the condition of laboratory, after expoed to stress for 8 weeks, corals recovery for 4 weeks,detected enzyme activity during the restoration.the results show that:（1） nitrates, CAT and SOD activities, Chl-a and zooxanthella density were higher than that of initial value, there were significantly difference（P<0.05）, each index turn down then went up. In low, medium and high concentration group, CAT activity and zooxanthella density of G. Stutchburyis and G. duofasciata in high recoveration at most time points reached the highest. SOD activity and Chl-a of low concentration recoveration group reached the highest; CAT activity and zooxanthella density of P. Lutea in high recoveration, Chl-a of low recoveration group and SOD activity of medium recoveration; ammonium, CAT activity and zooxanthella density of G. Stutchburyis in low recoveration, SOD activity of high recoveration and Chl-a of low recoveration reached the highest; CAT activity of medium recoveration, SOD activities of high recoveration and Chl-a, zooxanthella density of low recoveration in G. Duofasciata reached the highest; Phosphorus, CAT, SOD of low recoveration, Chl-a of high recoveration and zooxanthella density of medium recoveration in G. Stutchburyis; CAT, SOD activities and Chl-a of high recoveration, zooxanthella density of medium recoveration in G. Duofasciata reached the highest; CAT activity andzooxanthella density of high recoveration in P. Lutea, SOD activities and Chl-a of low recoveration reached the highest; each index of corals exposed to nutrient recovered, but couldn’t recover better than control group, might be due to the coral stress damage can’t repair, also might be due to shorter recovery time. Provide theoretical basis for restoration research of coral reefs district nutrient.