인공생태계를 이용하여 연안환경에서 N/P ratio의 변화에 따른 식물플랑크톤의 군집변화 예측

Abstract

Two mesocosm (enclosed ecosystem) experiments were performed to monitor the influence of inorganic nutrient addition to phytoplankton communities. Experiments were conducted in four enclosed mesocosms that made of polyethylene (1 m in diameter and 4 m in depth) and is located in the Jangmok Marine Station of KORDI. In first experiment of two experiments were studied during 4 weeks in 17 September to 12 October 2001. Nitrogen (NaNO3) were added to three mesocosms 70, 250, 700 ㎍/ℓ (final concentration), respectively and the other was no added (inner-control). The second experiment was carried out during 2 weeks in 26 November to 7 December 2001. Phosphorus (K2HPO4) were added to three experimental mesocosms 15, 35, 55 ㎍/ℓ caused N/P ratio gradient to among the mesocosms.The initial phytoplankton community in all mesocosms were dominated by diatoms, mainly Skeletonema costatum, Pseudonitzschia sp. Chaetoceros sp., Thalassiosira sp. After addition nitrate biomass of this dominant species sharply increased along with reduced inorganic nutrient causing rapidly uptake of this species in the mesocosms. Under the environment of exhausted inorganic nutrients, dropped DO (dissolved oxygen) and low pH, the species composition changed from the initial dominance to the doatom Cylindrotheca closterium. As the result of a phosphorus input the phytoplankton communities composition and biomass were not appeared to the distinct difference between with and without addition. The species composition changed from a diatom community dominated Pseudonitzschia sp. to undefined microflagellates through the time.These results suggest that major limiting factors for increased the biomass of phytoplankton have been nitrate deficiency, low N/P ratio.