engleski

Taxonomical study of phytoplankton in the Bay of Kotor, SE Adriatic Sea

The Bay of Kotor is a deeply indented bay located in the south-eastern coast of Adriatic Sea (European Mediterranean Sea). The bay sometimes called Europe's southernmost fjord, is in fact a submerged river canyon surrounded with above 1000 m high mountains. Information on planktonic communities in this area characterized by the extreme seasonal variations of karstic waters discharge is sparse and therefore the aim of the present study was to fill the knowledge gaps on phytoplankton taxonomic composition and distribution of size classes in the plankton assemblages. Sampling was carried out four times from April 2008 to March 2009 at three stations. A total of 76 samples (19 samples per sampling) were collected with Niskin bottles and analyzed. Phytoplankton composition was identified and enumerated using flow cytometer (Partec PAS) and an inverted microscope (Zeiss Axiovert 200) operating with phase contrast and brightfield optics. Additional net samples (mesh size 20µm) were acid cleaned and examined with transmission electron microscope (Zeiss EM10A) for diatom identification. Net samples (mesh size 5µm) were filtered on a 3µm polycarbonate filters mounted on stubs, sputter coated with gold and examined with scanning electron microscope (Phillips XL30). The results showed the high influence of freshwater influx which resulted in a strong vertical thermohaline gradient throughout the year influencing chemical and biological properties of the water column. The picophytoplankton was dominated in all seasons by phycoerythrin-rich cyanobacteria of the Synechococcus type. The nanophytoplankton was dominated by autotrophic/mixotrophic flagellates in the upper part of the water column and the coccolithophores in the lower part. In the winter/spring period Emiliania huxleyi and Helicosphaera carteri dominated among ten species of identified coccolithophores. Among diatoms Skeletonema marinoi was the most prominent in spring. The diatom genus Pseudo-nitzschia was present throughout the year and TEM examination revealed presence of four morphotypes: P. pseudodelicatissima, P. cf. pseudodelicatissima, P. calliantha and P. subfraudulenta. P. calliantha, a species for whom the production of neurotoxin domoic acid, the causative agent of Amnesic Shellfish Poisoning (ASP) is well documented, represented frequent component of phytoplankton assemblages. During summer the harmful dinoflagellate Prorocentrum minimum was also recorded in high abundances. The results indicate the importance of enhanced research effort with the focus on environmental factors driving potentially harmful algae blooms in the area as it sustains active shellfish farming activities.

Phytoplankton ; Kotor Bay ; Adriatic Sea

nije evidentirano