Latitudinal variation in toxicity and sexual compatibility of Alexandrium catenella strains from southern Chile

Póster.-- 12th International Phycological Congress, 22-26 March 2021Harmful algal blooms of the toxic dinoflagellate Alexandrium catenella are the main episodes esponsible for Paralytic Shellfish Poisoning (PSP) in Southern Chile (39.5-55°S). This large geographical area has been affected by intense PSP outbreaks (world record in toxicity levels) since their first detection 50 years ago. Considering, Alexandrium complex life history that involves the formation of benthic resting cysts, we selected nine strains of A. catenella isolated from the three southernmost regions of Chile (Los Lagos, Aysén, Magallanes). Thus, we conducted self and out-crosses in all possible combinations (n=45) and we assessed the effect of geographical distances in: i) toxin profiles of parental strains; ii) reproductive success indexes, and iii) resting cysts production. The toxin profiles were similar for all strains and characterized by C1, C2, GTX4, GTX1, GTX3, and NeoSTX. Nonetheless, both the analogs proportion (%) and the toxins (pg cell-1) presented variation according to strain geographical origin being more toxic strains located at the north (Bahía Mansa ~40.6°S). The highest reproductive success was found in Aysén strains (~45.5°S) followed by Magallanes (~54.9°S) and Bahía Mansa (40.6°S). Neither self-crossed were compatible indicating no evidence of homothallic behavior. Compatible pairings distanced between 1000-1650 km displayed the highest median of resting cysts abundance indicating a strong geographical distance effect. Our results contribute to the understanding of the intensity of PSP outbreaks in the austral region and enhance the importance of the resting cysts to fuel new HAB eventsN