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 and environmen tal factors were studied in open areas of the central and eastern Gulf of Finland in late summer 1993. The data was collected using unattend ed water sampling, as well as spatially and temporally frequent measur ements on in vivo fluorescence of chlorophyll a, temperature and salin ity on board a passenger ferry, which plied between Helsinki and St. P etersburg. The relative abundances of phytoplankton species, concentra tions of nutrients (Tot-N, NO2-N+NO3-N, NH4-N, Tot-P, PO4-P, Si) and c hlorophyll a were analysed from the water samples. The collected data set enabled the use of various statistical methods in order to explain the phytoplankton community structure in the study area. The multivar iate analyses were carried out using SAS software procedures (GLM, CLU STER, CANCORR). Variability in the phytoplankton community (biomass, s pecies composition) was high, and this paper clearly demonstrates that valuable information regarding pelagial biological dynamics, connecte d to extreme values, will be lost if the data is incorrectly simplifie d.