Productivity and abundance of bacteria and phytoplankton in Incheon Dock, western coast of Korea.

The monthly variations of abundance and productivity of bacteria and phytoplankton were investigated in 2002 at Incheon Dock in Korea, almost closed marine ecosystem. Incheon Dock has unique marine environment with scarcely a current and waves such as in a lake. The bacterial abundance was 0.4-6.3 x 10(6) cells x ml(-1), while the bacterial productivity showed in the range of 0.7-26.3 mgC m(-3) hr(-1). The phytoplankton chlorophyll-a concentrations fell between 2.1 and 18.1 microg x l(-1), where nanoplankton fractions contributed in 32.5-96.78% (average: 73.2%). The algal bloom occurred in March and August, and primary productivity measured by using 14C method, showed a fluctuation ranging from 49.4 to 4,359.4 mgC m(-2) day(-1). The primary productivity of nanotoplankton accounted for 79% of total phytoplankton. Meanwhile, the ratio of bacterial productivity over primary productivity was between 2.0 and 7.7. This study showed that the abundance and productivity of bacteria and phytoplankton were higher at Incheon Dock than those at other coastal areas in Korea. Especially the assimilation number was higher at Incheon Dock than that at lake Shihwa which is a severely eutrophicated area. This result indicates that Incheon Dock has unique ecosystem oceanographically and topographically and it differs from other coastal areas in terms of the low trophic level organisms being abundant and highly productive.

Morphological variation of dinoflagellate Prorocentrum lima (Ehrenberg) Dodge with geographical difference.

Prorocentrum lima (Ehrenberg) Dodge, one of the cosmopolitan dinoflagellates, is basically benthic and is found on the surface of macroalgae and detritus. The identification of this species requires detailed morphological observation because of its close similarity to other benthic Prorocentrum species. The purpose of this study is to detect the morphological variability of P. lima using culture clones collected from several areas to find an adequate way of subdividing the species. In this study, 33 clones of P. lima were collected from Saipan, Tahiti, Indonesia, Japan and Bermuda, and their thecal valves and periflagellar area were observed by means of light microscopy with differential interference contrast optics and scanning electron microscopy. In general cells have two centrally located pyrenoids and a posterior nucleus. The surface of both valves has many valve pores except the center. Evenly spaced marginal pores are located along the edge of the valves. P. lima samples studied herein were subdivided into four major types (ellipsoidal, general, short, and elongate ovoid) according to their shapes, length-to-width ratio and number of valve pores. The length-to-width ratios of ellipsoidal, general, short, and elongate ovoid types were 1.32, 1.33-1.43, 1.20-1.27, and 1.53-1.60 microm respectively. Also there were slight differences in the number of valve pores. The number of valve pores examined in this study ranges from 40 to 97: ellipsoidal, general, and short ovoid types range from 40 to 91, while an elongate ovoid type ranges from 80 to 97. The combination of valve shape, number of valve pores and length-to-width ratio provides useful information on the morphological variation of P. lima.