This dataset was compiled from a historical collection of phytoplankton datasheets. These data sheets were used as a protocol for phytoplankton sampling and analysis. They provided information about the metadata (sampling transect, station number, coordinates of the sampling station, sampling depth, sample collection date, name of the researcher who processed the sample, etc.); the equations used to calculate the abundance of phytoplankton species; and data (identified species, cells counted in the subsample, total abundance, and total biomass). Samples were concentrated by sedimentation and surface water removal to increase the phytoplankton density in the sample by following the standard sedimentation technique for sample preparation (Morozova-Vodianitkaia, 1954). After the volume of the concentrated sample was measured, a subsample of 0.1 ml was taken from the concentrated sample, poured into the counting chamber, and analysed under an inverted microscope, in order to identify and count all the phytoplankton species. Phytoplankton abundance per litre was calculated by the following equation: N = V1/V2 x n x 2, where N is the number of cells per litre of water, V1 is the volume of the concentrated sample, V2 is the volume of subsample, n is the number of cells counted in a subsample and 2 is the multiplication factor (Morozova-Vodianitkaia, 1948; Bodeanu, 1987 - 1988). The phytoplankton biomass was determined based on morphometric measurement of phytoplankton units. The biomass of phytoplankton per cubic metre of water was calculated by multiplying the abundance with the average wet weight of the species, following the average weights tables elaborated by Morozova-Vodnițkaia (1948; 1954) and Pițîk (1950), modified and updated by Bodeanu N. and Ruță G. (1995).
The dataset contains phytoplankton data collected in the Black Sea between 2001 and 2005 and processed by Andrei C., Anghel A., Boicenco L., Ionescu C., and Sburlea A. The data were collected from shallow to shelf Romanian waters from various transects such as Sulina, Mila 9, Portita, and Sf. Gheorghe (northern zone, strongly influenced by the freshwater input from the Danube Delta) to Constanta, Mangalia, and Vama Veche (southern zone). The sampling was carried out from standard depths with Niskin bottles. From each depth was collected a sample of 500 ml. The standard sedimentation technique for sample preparation was used (Morozova-Vodianitkaia, 1954). The scientific team identified and counted the phytoplankton species from a subsample with an inverted microscope and calculated the total abundance and biomass of each species. This dataset was compiled from a collection of phytoplankton datasheets and contains abundance (cells per liter) and biomass (mg/m3) data for individual phytoplankton taxa.