Effects of environmental factors on the phytoplankton community in the Gulf of Finland – unattended high frequency measurements and multivariate analyses

Relationships between phytoplankton species composition andenvironmental factors were studied in open areas of the central and easternGulf of Finland in late summer 1993. The data was collected using unattendedwater sampling, as well as spatially and temporally frequent measurements onin vivo fluorescence of chlorophyll a, temperature and salinity on board apassenger ferry, which plied between Helsinki and St. Petersburg. Therelative abundances of phytoplankton species, concentrations of nutrients(Tot-N, NO2-N+NO3-N, NH4-N,Tot-P, PO4-P, Si) and chlorophyll a were analysed from thewater samples. The collected data set enabled the use of various statisticalmethods in order to explain the phytoplankton community structure in thestudy area. The multivariate analyses were carried out using SAS softwareprocedures (GLM, CLUSTER, CANCORR). Variability in the phytoplanktoncommunity (biomass, species composition) was high, and this paper clearlydemonstrates that valuable information regarding pelagial biologicaldynamics, connected to extreme values, will be lost if the data isincorrectly simplified.