Assessing the impacts of an artificial breakwater on phytoplankton abudance and community structures: a case study of Sihwa Lake, Korea

Abstract

In order to assessing the current ecological health of the Shihwa artificial estuarine lake, located on the western coast of Korea. A monitoring study covered the inner and outer areas of Shihwa artificial breakwater, focused on phytoplankton biomass, community structure and related abiotic factors, was carried out from May 2007 to May 2008. The result displayed phytoplankton community in inner area was characterized higher abundance with a Chlorophyll a (Chl.a) annual average of 36.0 μg/l and a range from 1.2 to 342 μg/l in comparison with an annual average of 9.6 μg/l and a range from 1.2 to 37.7 μg/l in outer area respectively. However, a lower species richness and cell ratio of diatom in total phytoplankton were observed in inner area with a species number average of 22.4 and a diatom ratio average of 55.8%(50.43%) in comparison with 27.2 and 71.4%(73.13%) in outer area respectively. Moreover phyoplankton abundance in inner area had significant relationships with nutrient concentrations, whereas in outer area significant relationships between phytoplankton abundance with nutrient ratios appeared. Moreover, a relatively higher occurring frequency of flagellate blooms, such as Heterosigma akashiwo and Prorocentrum minimum, was observed in inner area paralleling with a lower occurring frequency in outer area during the study period. The results suggest the current semi-closed inn