Phytoplankton distribution in Mikawa Bay of Japan in relation to temperature and salinity variables

Abstract

Abstract. Djumanto, Rasul E, InoueT, Aoki S. 2017. Phytoplankton distribution in Mikawa Bay of Japan in relation to temperature and salinity variables. Bonorowo Wetlands 7: 16-25. Species composition and horizontal distribution of phytoplankton in relation to temperature and salinity variables were investigated in Mikawa Bay of Japan. Surface seawater was filtered with a 30 cm diameter conical plankton net with a mesh size of 53 µm weekly from mid-August to late September 2011. Surface layer temperature and salinity were measured with a CTD sensor. Phytoplankton samples were observed with an inverted microscope with phase contrast at 100-400 magnification. The salinity and surface temperature data and the density of the phytoplankton horizontally were made contour maps by connecting the location of each sampling station having the same value. Contour maps were created using surfer software. The result showed that the average temperature at the 1 m surface layer ranged from 22.7 to 28.7^oC. Meanwhile, salinity was ranged from 11.8 psu to 30.0 psu. Phytoplankton was abundant in the area with high temperatures and low salinity. The most abundant species among sampling stations in Bacillariophyceae was Chaetoceros sp(p). (52.2%) followed by Pseudo-Nitzschia sp(p) (27,7%), and then Coscinodiscus sp(p). (6.3%). On the other hand, the most abundant in Dinophyceae was Dinophysis sp(p). (1.1%) followed by Ceratium fusus (0.9%) and then Ceratium furca (0.8%), which was most dominant in the off-river mouth area. The phytoplankton population's density center and contour lines were changed and moved depending on salinity or temperature profiles.