Algae. 2001; 16(2): 189-196.

Phytoplankton in Chinhae Bay: Ⅰ. Photosynthetic Properties and Primary Production in Variant Light Environments

Jong-Gyu Park, Sung-Hoi Huh, Hae Jin Jeong

Environmental Research Center for Nakdong River watershed, Inje University, Department of Oceanography, Pukyong National University, Department of Ocean Information Science, Kunsan National University

To investigate the effects of variable light conditions on the primary production of phytoplankton, the biomass and productivities of phytoplankton were measured in Chinhae Bay, 1998. The cell counts and chl. a concentrations of phytoplankton varied from 109 to 36,204 cells·ml super(-1) and from 0.38 to 89.25 μg·l super(-1), respectively. The biomass of phytoplankton in inner bay were higher than those in outer bay off the southern coast of Kadukdo, positioned close to open sea. Primary productivities and chl. a specific primary productivities in surface layer varied from 3.40 (December, St. j4) to 510.51 (June, St. j4) mgC·m super(-3)·h super(-1), and from 0.77 (December, St. J4) to 13.05 (June, St. F5) mgC·mg·Chla super(-1)·h super9-1), respectively. The initial slope of photosynthesis-irradiance curves, α, ranged between 0.01 and 0.1 (mgC·mgChla super(-1)·h super9-1))(μE·m super(-2)·s super(-1)) super(-1) and high values of vertical attenuation coefficients, K sub(d), were observed in summer. When light conditions in surface layer were changed to unfavourable to phytoplankton, chl. a specific daily primary productivities within euphotic zone decreased drastically, showing a close exponential relationship (Y = e super(-0.017x), r super(2) = 0.94, p < 0.0001). This trend was observed at all stations, irrespective of survey time. The decrease rates of primary production owing to disadvantageous light conditions to phytoplankton were high at stations of small K sub(d) than at those of large K sub(d), which implies that phytoplankton in turbid waters is less labile to the variation of light environment.

Keywords : Chinhae Bay, photosynthetic properties, phytoplankton, primary production