Morphology and ecology of dinoflagellate Prorocentrum arcuatum Issel in lake Zmajevo oko

Vrsta Prorocentrum arcuatum Issel je fotosintetski dinoflagelat specifičan po rijetkoj pojavnosti u okolišu, dok je u meromiktičnom jezeru Zmajevo oko zabilježen kao dominanta vrsta u fitoplanktonskoj zajednici. Istražena je morfometrija stanica i dinamika pojavljivanja vrste P. arcuatum u euksiničnom jezeru Zmajevo oko. Učestalost pojavljivanja vrste P. arcuatum, za analizirano razdoblje od 1998. do 2021. godine, iznosila je 22,4%. Razvijala se većinom u toplijem dijelu godine, u razdoblju od lipnja do rujna, s najvećom abundancijom u lipnju 2018. godine (90530 st. L-1). Najveća brojnost vrste zabilježena je u sloju iznad kemokline, a temperatura je glavni čimbenik koji pozitivno korelira s pojavnošću. Morfometrijske značajke stanica su odstupale od dosadašnjih podataka te su stanice bile manje s prosječnom dužinom stanica 58,26 ± 4,45 µm. Morfometrija vrste je varirala kroz istraživano razdoblje, a značajno je korelirana s ekološkim čimbenicima, prvenstveno temperaturom te koncentracijom otopljene i čestične organske tvari.Species Prorocentrum arcuatum Issel is a photosynthetic dinoflagellate specific for its rare occurrence in the environment, while in the meromictic lake Zmajevo oko it was recorded as the dominant species in the phytoplankton community. Cell morphometry and the dynamics of the appearance of P. arcuatum in the euxinic Lake Zmajevo oko were investigated. The frequency of appearance of the species P. arcuatum for the analyzed period from 1998 to 2021 was 22.4%. Its occurrence and abundance are highest in the warmer period of the year, from June to September, while the highest abundance of the species was recorded in June 2018 (90530 cells L-1 ). It reached the highest abundances in the layer above the chemocline, the temperature as the main factor positively correlated with its occurrence. The morphometric characteristics of the cells deviated from the previous data, and the cells were smaller with an average cell length of 58.26 ± 4.45 µm. Morphometry of species varied throughout the researched period, and was significantly correlated with environmental factors, primarily temperature, and the concentration of dissolved and particulate organic matter