The Relationship between Primary Production of Microphytobenthos and Tidal Cycle on the Hwaseong Mudflat, West Coast of Korea

Abstract

The present study examined variation in sediment temperature and irradiance with respect to microphytobenthos primary production at the Hwaseong mudflat, west coast of Korea, under different tidal cycles. The study was carried out during March and April 2009, which encompassed two spring tides and one neap tide. It was not possible to continuously measure primary production in situ across the tidal cycles; hence, photosynthesis irradiance (P-I) curves at different temperatures were obtained experimentally in the laboratory. These readings were then used to calculate primary production, by projecting in situ mooring records of irradiance and temperature onto the P-I curves. The sediment temperature and irradiance were measured continuously, and the averages of 10-minute intervals from the mooring records were used. The results show that changes in primary production simulated from the P-I curves were strongly associated with the tidal cycle. During the two spring tides that were recorded, mean daily primary production was 1005 and 1125 mg C m(-2) d(-1), respectively. However, primary production was lower during the neap tide (898 mg C m(-2) d(-1)). Temperature appeared to influence these differences in mean daily production. In situ mean daily temperatures during exposure were 14 C and 20 C during the first and second spring tides, respectively. In contrast, mean daily total irradiance was noticeably higher in the first spring tide compared with the second spring tide. During the neap tide, the site was exposed in the morning and afternoon, when light intensity and temperature were relatively low. In contrast, during the spring tide, the site was exposed at noon, when light intensity and temperature were high. The current study provided new insights about how changes in environmental parameters during tidal cycles affect microphytobenthic primary production, indicating the complexity of this process and the requirement for further fine-scale research.