Contribution of the thraustochytrid Corallochytrium limacisporum Raghu-Kumar to microbial biomass in coral reef lagoons

ATP and organic carbon (OC) contents of cells of 5 isolates of thraustochytrids, including one of C. limacisporum were estimated from cultures. OC:ATP ratio in these isolates averaged 99. Based on these and the data collected on the number of C. limacisporum , total viable bacteria (saprophyte numbers), chlorophyll a content and total ATP in the lagoon waters, the contribution of C. limacisporum to the microbial biomass in coral reef lagoons of the Lakshadweep islands was calculated. The thraustochytrid contributed 2.88 to 213.57% ATP and 1.15 to 85.43% OC relative to total viable bacteria and 0.024 to 3.09% ATP and 0.002 to 1.24% OC to total microbial biomass. C. limacisporum and total viable bacteria together contributed only 0.844 to 6.02% ATP and 0.822 to 4.97% OC to the biomass. About 90% of the microbial biomass in the lagoons appeared to be from organisms other than the thraustochytrid, total viable bacteria and phytoplankton.