Responses of Planktonic Micro-Algae between Eutrophic Inshore and Oligotrophic Offshore Waters in The East Sea, Korea

Abstract

We investigated the horizontal distribution of phytoplankton assemblages and their relationships with environmental factors at 29 stations that ranged from eutrophic inshore waters to oligotrophic offshore waters, and we also investigated the vertical distribution of physical-chemical-biological factors between Ulleungdo and Dokdo in East Sea, Korea. In addition, we confirmed the phytoplankton community response to nutrient additions using bioassay experiments. Based on the field survey and bio-algal bioassay, the high nutrients in eutrophic waters dramatically affected the growth of diatom assemblages in contrast, the spatial nutrient gradient of the oligotrophic offshore waters of the East Sea had an important role in determining the patterns of phytoplankton distribution and growth response. Our results indicated that a dominant northwestern wind following a low-pressure system led to water mixing, and thus, the phytoplankton did not respondquickly due to the lack of nutrients in the euphotic layer of the offshore waters of the East Sea.he vertical distribution of physical-chemical-biological factors between Ulleungdo and Dokdo in East Sea, Korea. In addition, we confirmed the phytoplankton community response to nutrient additions using bioassay experiments. Based on the field survey and bio-algal bioassay, the high nutrients in eutrophic waters dramatically affected the growth of diatom assemblages in contrast, the spatial nutrient gradient of the oligotrophic offshore waters of the East Sea had an important role in determining the patterns of phytoplankton distribution and growth response. Our results indicated that a dominant northwestern wind following a low-pressure system led to water mixing, and thus, the phytoplankton did not respondquickly due to the lack of nutrients in the euphotic layer of the offshore waters of the East Sea.