Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in the Bizerte Lagoon. Forty eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium pacificum, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cyst ranged from 1276 to 20126 cysts g−1 dry weight sediment. Significant difference in cyst distribution pattern was recorded among the zones, with the higher cyst abundance occurring in the inner parts of the lagoon near shellfish aquaculture farms. Redundancy analyses showed two distinct associations of dinocysts according to locations and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially the harmful ones namely A. pacificum and P. zoharyi, and currents play a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in Bizerte Lagoon.
Keywords:dinocysts; mapping; enviromental factors; hydrodynamics; Bizerte Lagoon.