Variable thermal and biochemical stress responses of tissue balls from Lithophyllon repanda, Pocillopora damicornis and Acropora muricata

抄録

This study examined the effects of thermal stress (28 and 31°) and biochemical stress (sponge Haliclona madrepora and ascidian Didemnum molle crude methanolic extracts) on density of coral tissue balls (TBs) and on their symbiont photosystem II functioning. Coral TBs were obtained from scleractinian corals harbouring symbionts Cladocopium [Lithophyllon repanda, Pocillopora damicornis and Acropora muricata] and symbionts Durusdinium [Acropora muricata]. Thermal stress experiments at 28 and 31°C tended to have negative effect on TB density from A. muricata (harbouring Cladocopium or Durusdinium) and L. repanda (harbouring Cladocopium) but not from P. damicornis (harbouring Cladocopium). Effective quantum yield, ΦPSII, decreased at temperature 31°C in A. muricata (Cladocopium) but remained stable in A. muricata (Durusdinium). Combined thermal (31°C) and biochemical (50µg ml^－1 D. molle extract) stressors had a relatively more pronounced effect on TB density, but did not affect ΦPSII in the three species, irrespective of symbiont genus. Thermal stress and 200µg ml^－1 D. molle affected ΦPSII in A. muricata (Cladocopium) and L. repanda (Cladocopium) as compared to P. damicornis (Cladocopium). Thermal stress and 50µg ml^－1 H. madrepora affected TB density in three coral species but caused a drop in ΦPSII only in A. muricata (Cladocopium). Thermal stress and 200µg ml^－1 H. madrepora affected both TB density and ΦPSII in the three tested coral species. These results suggest a variable susceptibility among corals, with A. muricata (Cladocopium) being the most susceptible and P. damicornis (Cladocopium) the least susceptible to studied thermal and biochemical stressors.