Phytoplankton Species Composition and Abundance in the Sacramento-San Joaquin River Delta: Microscopic Enumeration of USGS Samples, beginning in 2016 (ver. 2.0, December 2025)

This dataset contains multiple types of data characterizing phytoplankton in the Sacramento-San Joaquin Delta (California, USA). 1) Bright field microscopy was used to identify and enumerate phytoplankton community composition; 2) Epifluorescent microscopy was used to enumerate picophytoplankton (phytoplankton cells less than 2 microns in diameter) and, 3) a categorical visual index, Microcystis Visual Index (MVI), was used to rapidly estimate the abundance of Microcystis colonies near the surface. Revision History First release: June 22, 2023 Revision 1.1: December 28, 2023 Revision 2.0: December 11, 2025