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Aquatic Microbial Ecology

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AME 63:231-243 (2011)  -  DOI:

Influence of altered light conditions and grazers on Scrippsiella trochoidea (Dinophyceae) cyst ­formation

Veronica Lundgren*, Edna Granéli

School of Natural Sciences, Linnaeus University, Kalmar, Sweden

ABSTRACT: We investigated whether or not the presence of copepods and different light conditions induced cyst ­formation in dinoflagellates. Scrippsiella trochoidea was exposed to Acartia tonsa directly and indirectly (grazer filtrate), in high light and low light conditions. The ingestion, faecal ­production and egg production of A. tonsa were compared between diets of S. trochoidea vegetative cells and temporary cysts. We found no effect of direct or indirect exposure to A. tonsa on S. ­trochoidea cyst formation in either high light or low light conditions. Controls and A. tonsa treatments kept in light displayed around 20% temporary cysts, whereas controls and A. tonsa treatments in low light were shown to have 50 to 80% temporary cysts. Thus, low light conditions had a strong effect on ­temporary cyst formation. No hypnocysts were observed in any experiment, which is probably related to the longer incubation times needed for their observation. Feeding on diets dominated by temporary cysts compared to vegetative cells decreased ingestion by a factor of 2.7, while faecal and egg production decreased by a factor of 2.2 and 2.9, respectively, suggesting that induction of temporary cysts in response to A. tonsa could be a survival strategy. However, S. trochoidea does not ­possess any grazer-induced defence in terms of temporary cyst formation, as it did not produce ­temporary cysts when exposed to A. tonsa. Rather, induction of temporary cysts seems to be controlled by decreased light intensity, which is a favorable trait for this species when driven to water depths where light is scarce.

KEY WORDS: Scrippsiella trochoidea · Cyst formation · Light intensity · Grazer density · Temporary cysts

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Cite this article as: Lundgren V, Granéli E (2011) Influence of altered light conditions and grazers on Scrippsiella trochoidea (Dinophyceae) cyst ­formation. Aquat Microb Ecol 63:231-243.

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