Changes in Toxin Production, Morphology and Viability of Gymnodinium catenatum Associated with Allelopathy of Chattonella marina var. marina and Gymnodinium impudicum

Allelopathy between phytoplankton organisms is promoted by substances released into the marine environment that limit the presence of the dominating species. We evaluated the allelopathic effects and response of cell-free media of Chattonella marina var. marina and Gymnodinium impudicum in the toxic dinoflagellate Gymnodinium catenatum. Additionally, single- and four-cell chains of G. catenatum isolated from media with allelochemicals were cultured to evaluate the effects of post exposure on growth and cell viability. Cell diagnosis showed growth limitation and an increase in cell volume, which reduced mobility and led to cell lysis. When G. catenatum was exposed to cell-free media of C. marina and G. impudicum, temporary cysts and an increased concentration of paralytic shellfish toxins were observed. After exposure to allelochemicals, the toxin profile of G. catenatum cells in the allelopathy experiments was composed of gonyautoxins 2/3 (GTX2/3), decarcarbamoyl (dcSTX, dcGTX2/3), and the sulfocarbamoyl toxins (B1 and C1/2). A difference in toxicity (pg STXeq cell(-1)) was observed between G. catenatum cells in the control and those exposed to the filtrates of C. marina var. marina and G. impudicum. Single cells of G. catenatum had a lower growth rate, whereas chain-forming cells had a higher growth rate. We suggest that a low number of G. catenatum cells can survive the allelopathic effect. We hypothesize that the survival strategy of G. catenatum is migration through the chemical cloud, encystment, and increased toxicity.

Automated summary

Allelopathy between phytoplankton organisms is promoted by the release of substances that limit the presence of dominating species. In this study, the allelopathic effects of Chattonella marina var. marina and Gymnodinium impudicum were evaluated on the toxic dinoflagellate Gymnodinium catenatum. Experiments showed that exposure to cell-free media of C. marina and G. impudicum resulted in growth limitation, increased cell volume, cell lysis, and increased concentration of paralytic shellfish toxins in G. catenatum. Differences in toxicity were observed between G. catenatum cells exposed to the filtrates of C. marina var. marina and G. impudicum and those in the control group. The study suggests that G. catenatum's survival strategy involves migration through the chemical cloud, encystment, and increased toxicity.