수치모델을 활용한 사천만 해역의 담수방류에 따른 식물플랑크톤 종조성 변화

Abstract

Phytoplankton species composition change according to freshwater discharge in Sachen Bay using a numerical model

Abstract

The dam blocks fresh water from flowing into the coastal area. The pulse inflow of the nutrients load accelerates the oligotriphic in the coastal area. Depending on the cycle and amount of freshwater discharge, it causes changes in the stoichiometry ratio of limiting nutrients and alters species compositions of phytoplankton. Therefore, this study investigated changes in nutrients and phytoplankton community structure following the discharge of Namgang Dam in Sacheon bays. And a numerical model was constructed to elucidate whether changing of phytoplankton species. As a result, nutrient loading decreased in the long term. As a result of the summer linear regression analysis of the discharge and the nutrient load, it was found that the nutrients in the coastal area tend to increase when the discharge exceeds the average discharge(88m2). Phytoplankton grows through assimilation after storing nutrients in environmental water in the intracellular nutrient pool. Internal nutrient pools vary in size from species to species. When the nutrient concentration in the environmental water is low, species with a large pool size are advantageous for growth. Two phytoplankton species, a diatom Skeletonema sp., a dinoflagellate Alexandrium sp., were introduced into the model. To simulate environmental conditions of the Sacheon bay were applied to the model. When each modeled species was included individually, they showed characteristic responses to different intervals of nutrient supply. Skeletonema sp. was sensitive, showing large fluctuations in cell density in response to pulses of nutrients. In simulations of mixed-species, a pulsed nutrient supply with an intermediate frequency interval led to a longer period of coexistence than continuous nutrient supply. In simulations of mixed-species, a pulsed nutrient supply with an 30 days frequency interval led to Alex to become dominant species. Implications of the present study are discussed: The discharge of the dam may change the phytoplankton cluster structure in the estuary. Therefore, when discharging the dam, the period and amount of discharge should be considered.