Organic carbon flux in Shiraho coral reef (Ishigaki Island, Japan)

Abstract

Organic carbon flux and community production rates were estimated on Shiraho coral reef (Ishigaki Island, Japan) from 19 to 26 September 1998. The daily net community production (Pn) and respiration rate (R) during the study period were 3 to 79 and 596 mmol C m-2 d-1, respectively. This resulted in a daily gross community production (Pg) of 599 to 675 mmol C m-2 d-1. The variation of Pn associated with the uncertainty of the curve fitting parameters of light response curves for photosynthesis was estimated using an error propagation formula. The averaged Pn ± SE was 36 ± 12 mmol C m-2 d-1 (n = 23), indicating that the Pn was significantly positive (t-test, p < 0.05). The apparent fluxes of dissolved organic carbon (DOC) and particulate organic carbon (POC) on the reef were estimated as 30 to 36 and 5 to 7 mmol C m-2 d-1, respectively. The sum of which was comparable with the Pn during the study period. The sediment trap study conducted at 1 km off the reef and 40 m depth showed that the vertical flux of POC was 1.0 mmol C m-2 d-1. The results indicated that 6 to 7% of the Pg was exported to offshore and about 14 to 20% of the POC exported from the reef flat and 0.2% of the Pg reached 1 km off and 40 m depth.