Authors: Yukiko Taniuchi Tsuyoshi Watanabe Shigeho Kakehi Tomoko Sakami Akira Kuwata
Publish Date: 2015/11/17
Volume: 73, Issue: 1, Pages: 1-9
Abstract
Sendai Bay is located on the Pacific coast of northern Japan and suffered serious damage following the 2011 off the Pacific coast of Tohoku earthquake and tsunami in March 2011 To assess the impact on the marine ecosystem information was needed on the phytoplankton communities and their seasonal variation However such information was limited Therefore an intensive monitoring of the phytoplankton was carried out from March 2012 to April 2014 Seasonal variation of the phytoplankton community was similar at coastal and offshore stations Total phytoplankton biomass based on Chl a concentration peaked in spring and then decreased to a minimum in summer before gradually increasing during early winter and peaking again in the following spring This seasonal pattern was consistent with previous studies conducted before the earthquake and tsunami Also size structure of the phytoplankton community and its four main groups was estimated from the sizefractioned samples of Chl a Our results also showed that the spring bloom consisted of large diatoms with their growth ceasing due to nitrogen depletion The bloom was followed by a summer period where cyanobacteria and picoeukaryote became dominant with high cell densities in spite of low nutrient concentrations In addition sporadic environmental changes such as those following typhoons were observed These resulted in large increases/decreases in individual phytoplankton groupsWe particularly wish to thank Y Sasaki and Dr H Saito for nutrient analyses and the captain and crews of Wakatakamaru and Dai5Taikaimaru for their cooperation We also thank Dr D Jewson for his critical reading of the manuscript This work was supported by CREST JST
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