Distribution of resting cysts of the potentially toxic dinoflagellate Alexandrium pseudogonyaulax in recently-deposited sediment within Bizerte Lagoon (Mediterranean coast, Tunisia)

Abstract

This study investigated the spatial distribution of Alexandrium pseudogonyaulax resting cysts in recently deposited sediment of Bizerte lagoon (South-Western Mediterranean, Tunisia). This lagoon is the subject

of many anthropogenic impacts, such as holding important fishing and aquaculture activities. A. pseudogonyaulax has been shown to produce Goniodomin A, which is a biologically-active compound. We

showed that this dinoflagellate produces two types of resting cysts, which could be distinguished by the presence or the absence of a paratabulate wall. The average cyst density across the whole lagoon was rather high, reaching 639 cysts g1 of dry sediment (DS). Cyst densities varied widely among the sampled stations, with the highest density of 1685 cyst g1 DS being recorded at station 51 near a mussel

farm. With respect to sediment characteristics, the highest cyst densities were found within silty sediments with high water content values. The distribution of A. pseudongoyaulax cysts in Bizerte lagoon

appears to be related to hydrodynamic factors.