Species specific encystment patterns in three Baltic cold‐water dinoflagellates: The role of multiple cues in resting cyst formation

The relationships among cellular nutrient status, environmental conditions (temperature and nutrient availability), and cyst production were studied in batch cultures of three cold‐water dinoflagellates ( Scrippsiella hangoei , Gymnodinium corollarium , and Woloszynskia halophila ) isolated from the Baltic Sea. We tested the effect of increasing temperature while providing nutrient‐replete conditions as well as the effect of ambient nutrient (N, P) deficiency. The results revealed different encystment cues and patterns in the three species. While depletion of ambient nitrogen and subsequent internal N stress were the primary factors behind cyst production of G. corollarium , higher temperature led to substantial encystment of S. hangoei and W. halophila without a direct link to cellular nutrient physiology. In W. halophila , N limitation induced a transition of the population to small cells presumably representing gametes, but this process was not followed by cyst formation. Phosphorus stress was not directly linked to cyst formation in any of the species. Our data indicate that both reliable token cues (such as temperature) and ultimate causes (for example, nutrient depletion) for encystment are likely involved in the cystformation process. Such duality might provide an explanation for multiple triggers inducing encystment in laboratory settings and the lack of evidence for a direct relationship between nutrient depletion and cyst formation in the field.