Changes in marine environmental factors and phytoplankton community composition by short-term investigation in the harbor of the eastern part of the South Sea, Korea

Abstract

To understand the relationship between the environmental factors and phytoplankton community structures, and the possibility in which early outbreaks of Cochlodinium polykrikoides occur in the inner bay of Korea, short-term investigations were conducted at 17 stations in the eastern part of the South Sea every two weeks from July 7 to August 24, 2016. The water temperature increased from 22.3 °C on the first survey to 28.4 °C on the fourth survey, which was about 6.01 °C higher than the first. The salinity was relatively high at Stns. 8&#8211 13 in the inner bay. In the first survey, rainfall of about 150 mm was observed, so nutrients were supplied at a high level and a high concentrate of Chl. a was observed. Cryptophyta (Crpytomonas spp.) was 58.3 %, followed by Bacillariophyta was 33.8 %. In particular, at Stn. 5, Dinophyta Prorocentrum spp. accounted for a very high ratio of 32.2%. In the second survey, low phytoplankton populations were characterized, and Bacillariophyta (Chaetoceros spp.) accounted for 61.0 %. At station 4, Skeletonema spp. showed high populations but did not appear in the other stations nor was observed at a low density. In the third survey and the fourth survey, the phytoplankton populations were very low. Bacillariophyta were occupied to 78.0 % in the third and 73.3 % in the fourth. Interestingly, although we investigated the appearance of C. polykrikoides at the beginning of the red ti were conducted at 17 stations in the eastern part of the South Sea every two weeks from July 7 to August 24, 2016. The water temperature increased from 22.3 °C on the first survey to 28.4 °C on the fourth survey, which was about 6.01 °C higher than the first. The salinity was relatively high at Stns. 8&#8211 13 in the inner bay. In the first survey, rainfall of about 150 mm was observed, so nutrients were supplied at a high level and a high concentrate of Chl. a was observed. Cryptophyta (Crpytomonas spp.) was 58.3 %, followed by Bacillariophyta was 33.8 %. In particular, at Stn. 5, Dinophyta Prorocentrum spp. accounted for a very high ratio of 32.2%. In the second survey, low phytoplankton populations were characterized, and Bacillariophyta (Chaetoceros spp.) accounted for 61.0 %. At station 4, Skeletonema spp. showed high populations but did not appear in the other stations nor was observed at a low density. In the third survey and the fourth survey, the phytoplankton populations were very low. Bacillariophyta were occupied to 78.0 % in the third and 73.3 % in the fourth. Interestingly, although we investigated the appearance of C. polykrikoides at the beginning of the red ti