Feeding Research Of Zoanthus Sp. On Two Microalgae

Zoanthus sp.is one of the zooxanthellae symbiotic corals which can get nutrition not only from photosynthesis,but also directly through food absorption.In present study,two common dietary microalgae:Platymonas subcordiformis and Isochrysis galbana were used as heterotrophic sources and the feeding rate,DNA marker and histological analyses were used to investigate if Zoanthus sp.feed on these two microalgae.Moreover,a 30 days feeding experiment was performed to study the effects of feeding and light intensities on coral growth rate,the content of maximum photochemical efficiency(Fv/Fm),zooxanthellae concentration,concentration of chlorophyll a and chlorophyll C2,the organic content of coral tissue and the particle organic content in waters.The main results are as follows:1.The results of feeding rate,DNA marker and histological analyses all incdicated that Zoanthus sp.could feed on Platymonas subcordiformis and Isochrysis galbana,moreover,Zoanthus sp.took more Isochrysis galbana than Platymonas subcordiformis.2.Zoanthus sp.had the highest growth rate in the group of 40001x light intensity and fed with Platymonas subcordiformis.The mortality rate was the highest in the group of 50001x without feeding.In addition,the combination of autotrophic and heterotrophic nutrients increased the organic content of coral tissue.3.The Fv/Fm decreased when the light intensity was 5000lx which indicated that the corals were under stress.The intake of heterotrophic nutrients could relieve the influence of the above stress.In addition,the content of zooxanthellae was significantly increased when Zoanthus sp.toke in autotrophic nutrition.Heterotrophic nutrients also promoted the zooxanthellae content.The content of chlorophyll a and chlorophyll C2 decreased under high light intensity.4.Light intensity and feeding both could affect the status and quantity of Zoanthus sp.polyps.Corals fed with concentrated algae grew better than corals not fed.The status of Zoanthus sp.polyps under light intensity of 40001x were better than corals under 50001x.5.The concentration of suspended particulate matter in the waters of none feeding group was significantly reduced.And the concentration of particulate organic matter in the waters of feeding groups were increased.