engleski

A 40 year dataset on the species composition and ecology of the genus Dinophysis in the open waters of the northern Adriatic

The marine dinoflagellate genus Dinophysis is an important component of HAB blooms in coastal ecosystems worldwide, however the knowledge on the ecology and species composition of this genus in the open waters of the Adriatic Sea is limited. Annual dynamics, seasonality and ecological characteristics of the genus Dinophysis spp. associated with shellfish toxicity were studied before but only in coastal areas where shellfish farms are present (Ninčević Gladan, 2008). Our aim was to analyze the Dinophysis species composition on a spatial temporal scale across the NA basin and look into details over the last four decades to see if there were some changes in species composition, abundances, frequency of appearance and contribution to the phytoplankton community over last 40 years. We looked at Dinophysis distribution over 46 stations spread over the whole northern Adriatic in more that 10000 samples. To get clear data on the vertical distribution, Niskin samples in 5 depths at each sampling station were analyzed. Dinophysis spp. was found in approximately 1800 times. According to the checklist from 2002 there are 24 species from this genus in the Northern Adriatic. In our dataset we found 20 of them. Twelve species were very rare (e.g. D. hastata, D. parvula, D. schroederi, D. sphaerica…) while 6 species were significantly more frequent. The frequency of appearance for most frequently found species were: D. sacculus (3.8 %), D. caudata (3.75 %), D. fortii (2.65 %), D. ovum (1.3 %) and D. tripos (0.93%). Those species were found to be the most abundant as well. Maximal abundances were recorded during 1996 for D. fortii (8.8 x103 cells l1) and D. caudata (7.4 x103 cells l-1) at stations at western part of the basin. While D. ovum showed maximal abundances in the offshore waters in the middle of the basin. In the 1970s D. ovum bloomed in May while in the 1980s the bloom switched to July. Similar behavior was observed also for D. sacculus. We also observed that D. caudata and D. fortii reached their maximum in late summer months while D. tripos was present from autum until January.

phytoplankton ; Adriatic Sea ; dinoflagelates ; Dinophyisis

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