Phytoplankton Bloom in the Northern Adriatic - Dominant Groups and Species during the Spring-Summer Period 1988.

Abstract

Daje se osvrt na sastav dominantnih grupa i vrsta fitoplanktona u vodama sjevernog Jadrana tijekom perioda »cvjetanja« u proljetno-ljetnom razdoblju 1988. godine. Razmatraju se neke ekološke karakteristike sredine, koje bi mogle imati utjecaj na sastav fitoplanktonske zajednice, te na razvitak specifičnog oblika »cvjetanja«, praćenog tvorbom sluzavih agregata.During the late spring-summer period 1988 an exceptional phytoplankton bloom, accompanied by mucous aggregates formation occurred in the whole of the northern Adriatic region. Nanoplankton dominated the phytoplankton community, while within the microplankton, diatoms (Chaetoceros sp., Rhizosolenia fragilissima, Leptocylindrus danicus, Nitzschia delicatissima compl., Skeletonema costatum) were dominant. The long-term investigation data indicate nanoplankton blooms, as well as di- noflagellate dominance in the late spring period, when the phytoplankton bloom 1988 was determined. An analysis of oceanographic data for the period of initial bloom phase 1988 show unusual values. Salinity was lowered to 16 X 10-3, while all the nutrient concentrations were exceptionally high (Tab. 2). Surface water temperature was higher than usually by about 2”C. On the base of literature data, it is hypothesized that the observed shift in the phytoplankton community structure with appearance of diatoms bloom 1988 could be related to the unusually high nutrient concentrations, originating from freshwater inflows, especially those of the Po river, in the vicinity of which the bloom began