Phytoplankton species abundance in Lake Inba (Japan) from 1986 to 2016

Lake Inba is one of the most eutrophic lakes in Japan. This data paper reports the abundance of phytoplankton species sampled biweekly from April 1986 to March 2016 at four stations in Lake Inba. Monitoring has been carried out by Chiba Prefectural Government, and phytoplankton count data have been collected since 1986. A total of 340 phytoplankton species were identified and enumerated by microscopy, as numbers of cells or colonies. The abundance of each species was expressed as cells per milliliter lake water. Total cell density ranged from 102 to 108 cells per ml. The dominant cell class density was Cyanobacteria throughout the year. Cyanobacteria, such as Phormidium spp., Microcystis aeruginosa, and Anabaena spp. (Dolicospermum spp.), were the most dense in all months. The dominant cyanobacteria species reached concentrations of 107 cells per ml. Diatoms, such as Aulacoseira granulata and A. ambigua, were also abundant, reaching 106 cells per ml. These data can be used to appreciate how anthropogenic disturbances, such as eutrophication and global warming, affect density and community composition of phytoplankton.