Eco- fingerprinting of Borghiella dodgei (Dinoflagellata): experimental evidence of a narrow environmental niche

The dinoflagellate Borghiella dodgei Moestrup, Hansen et Daugbjerg, was cultivated in the laboratory under different temperature, nutrients, and light conditions. Growth rates, cell biovolume, cyst formation, pigment content, and MAAs were determined. Experiments showed that this algae grew well at low temperatures, and grew slowly without organic supplements. While it was not able to grow in the dark, Borghiella survived for long periods without a light source. In particular, Borghiella grew well at temperatures of <6 °C. Cell yields increased ten fold with organic supplements and increasing irradiance levels had a positive effect on growth. Cell volume was not affected by light conditions but increased with an increase in temperature or a lack of nutrients. The formation of thick-walled resting cysts was enhanced by an increase in temperature while light conditions did not effect encystment. Chlorophyll a content per cell was inversely related to irradiance levels. Cultures with a high number of resting cysts were characterized by a red-brick colour and altered peridinin/chlorophyll contents. Even after several years of culturing, Borghiella was still capable of MAA synthesis. The temporal spatial occurrence of this species in Lake Tovel was confronted with results from in vitro experiments. Borghiella’s growth requirements make it well suited to the unique habitat of Lake Tovel.