통영 오비도 어류양식장 주변에서 하계 수계 내 단주기 환경요인의 변화에 따른 미세조류 반응

Abstract

In order to assess the potential environmental factors in the vicinity of a fish cage farm, we investigated the biotic and abiotic factors during a short-term period in summer 2016 in two inner stations of Tongyeong Obi. High water temperature on August 10th was apparent among the full depth of up to 29℃, which might have been related to the abnormally high temperatures of large amounts of the Changjiang River discharge along the Tongyeong coast. The concentration of nitrate+nitrite, ammonium, phosphate, and silicate ranged from 0.08 to 5.11 μM, 0.08 to 34.62 μM, 0.01 to 1.15 μM, and 1.46 to 31.79 μM, respectively. The nutrients were mainly supplied by precipitation and leaching from the bottom sediments in the fish culture farm area. It was not retained for a long duration because of the phytoplankton consumption and diffusion by water currents. The chlorophyll a concentration varied from 0.49 μg l-1 to 7.39 μg l-1. At that time, Chaetoceros debilis, C.pseudocurvisetus, and Pseudo-nitzschia delicatissima were rapidly proliferated and reached the level of 4.74 × 109 cells l-1. In particular, the lowest dissolved oxygen was recorded at 4.52 μg l-1 at the bottom layer after bloom. Therefore, even though phytoplankton blooms in summer have frequently occurred in a fish culture farm area, the oxygen-deficient environments were not found in neither the surface nor bottom layers, which implied that the water masses might be well exchanged from the mouth of the northwest and southeast between Obi and Mireuk Island in the study area.