Resting cysts of the toxigenic dinofiagellate genus Alexandrium in recent sediments from the Western Mediterranean coast, including the first description of cysts of A-kutnerae and A-peruvianum

Cyst studies carried out in 2002-2003 on Mediterranean Sea sediment from seven different sites along the Catalan and Balearic coasts (Western Mediterranean) revealed a higher diversity of Alexandrium species in the region than was previously known. The cysts of eight species of the toxigenic, marine dinoflagellate genus Alexandrium are described, and some, such as A. kutnerae, A. margalefi, A. peruvianum and A. pseudogoniaulax, are reported from the area for the first time. This is also the first record of resting cysts of A. taylori in Mediterranean sediment, and the first description known to date of resting cysts for A. kutnerae and A. peruvianum. All the cysts were characterized by a smooth wall except for the paratabulated cyst of A. pseudogoniaulax, and most of them had a prominent yellow/orange accumulation body. Nevertheless, we have also detected an unparatabulated cyst of A. pseudogoniaulax, both from the sediment and in cultures. The cyst of A. kutnerae had a roughly cylindrical shape with rounded ends which makes it impossible to distinguish from resting cysts of A. tamarense and A. catenella, while the flattened round cysts of A. peruvianum were very similar to those of A. taylori. The cyst concentration data revealed A. catenella and A. minutum to be the most abundant cysts in the region, and they were detected in semi-enclosed waters, such as harbours. This highlights the importance of water exchange in the accumulation of cyst beds of these species, which has already been reported in the region by other authors for A. minutum. This paper contributes to the biogeographic distribution of some Alexandrium species, such as A. kutneare, A. margalefi, A. peruvianum and A. pseudogoniaulax, which have been reported only infrequently in a global context.