DIVERSITY OF THE DINOFLAGELLATE GENUS ALEXANDRIUMIN THE MEDITERRANEAN SEA
Santiago Fraga*, Isabel Bravo, Roberto González, Nagore Sampedro, Esther Garcés, Magda Vila, Jordi Camp,
Memé Masó, Mariagrazia Giacobbe, Antonella Lugliè and Olympia Gotsis
* Instituto Español de Oceanografía, Subida á Radio Faro 50, 36390 Vigo, Spain - Santiago.email@example.com
Harmful Algal Blooms (HAB) are a growing problem in the world. The dino?agellate Alexandrium, with 12 species recorded from the
Mediterranean Sea, is one of the most important genera causing HAB. Some Alexandriumspecies produce potent Saxitoxins that may
enter the food web through filter feeding mollusks, and cause intoxications in humans.
Alexandriummay also produce massive blooms in confined areas like beaches or harbours, that, even when non toxic, affect tourism, an
important industry in the Mediterranean.
Keywords : Harmful Algal Blooms, Alexandrium, Mediterranean
Rapp. Comm. int. Mer Médit., 37,2004
The EU project strategy ((EVK3-CT-2001-00046) (http://www.
icm.csic.es/bio/projects/strategy) focuses on the dino?agellate genus
Alexandrium. This genus includes species causing Paralytic Shellfish
Poisoning (PSP), and most Harmful Algal Blooms (HAB) in the
Mediterranean. Problems associated with this genus have increased in
the last decade. The project analyzes different aspects of Alexandrium
in the Mediterranean in order to develop a theoretical framework of its
expansion. A sampling network has been developed in four areas
along the northern Mediterranean (Fig.1), and a database has been
created with the input of the STRATEGY network. One of the
objectives of this network is to follow the progress of Alexandrium
species in the region and to compare areas with the same bloom
The propagation of the genus Alexandriumwithin the
Mediterranean is difficult to assess as reliable distributional
information is scarce. Routine monitoring (mainly related to shellfish
farming) is not addressed to elucidate if an increment or/and a species
propagation is actually occurring. Identification of the blooming
species requires taxonomic expertise and careful examination of the
plate pattern, uncommon in routine analysis of plankton samples, so
we suspect some reports may be misidentifications. Most bloom
descriptions are published in the “grey” literature and in most cases,
only the first detection in a specific area is described. Therefore a key
point in the study of the expansion of Alexandriumis to learn how
many species are present in the Mediterranean, and to trace their
Nine species of Alexandriumhave been obtained in culture from
vegetative cells or from resting cysts, that, in addition to another
species already in culture, make an important collection of strains, and
the source of material for works in progress. With two other species,
already reported from the Mediterranean, a total of 12 species is
known from the sea. Balech (1) has divided genus Alexandriumin two
subgenera: Alexandriumand Gessneriumdepending on the contact of
plates 1’and Po which is direct in the first and absent in the second.
The type species of the genus is A. minutum, described from
Alexandria, Egypt (2), but widespread in the Mediterranean, and
known from blooms elsewhere in the sea. This species is toxic (PSP).
Alexandriumcatenella, a very toxic species frequently causing
summer blooms in harbours (3) or in coastal lagoons with shellfish
farms, is more common in the western Mediterranean. Among the
non-toxic species of concern to recreational use is A. taylori. This
species blooms in the pristine waters of highly frequented beaches
turning the water turbid, and providing a source of complaints by
tourists that think it is some kind of pollution (4). Alexandriumcf.
peruvianumwas found in the Catalan coast but its potential toxicity is
yet unknown, but of concern as A. peruvianumis a close relative of A.
ostenfeldii, a species which is toxic in the North Atlantic.
Alexandrium tamutum, a new species (5), was already observed in the
northern Adriatic, off Naples, Sardinia and the Catalan coasts. The
other species are not so important as some of them are very rare or non
toxic, and hence harmless.
List of species:
A. minutum- Widespread in the Mediterranean. Toxic bloom species.
A. catenella- Western Mediterranean. Very toxic bloom species.
A. tamutum- Adriatic, Tyrrhenian, and Catalan coast. Non Toxic.
A. tamarense- East and West Mediterranean. Toxic and non toxic
A. affine- Alboran Sea. Non toxic.
A. andersonii- Italy and Greece. Toxic and non toxic strains.
A. cf.peruvianum- Catalan coast. Toxicity unknown.
A. taylori- East and west Mediterranean. Non toxic bloom species
A. pseudogonyaulax- Western Mediterranean - Unknown toxicity
A. margalefi- Western Mediterranean. Unknown toxicity
A. balechii-Tyrrhenian Sea. Non toxic.
A. foedum. -Tyrrhenian Sea. Toxicity unknown.
1-Balech E, 1995. The genus AlexandriumHalim (Dino?agellata).
Sherkin Island Marine Station. Sherkin Island, Co. Cork, Ireland.151 p.
2-Halim, Y., 1960. Alexandrium minutum, n. gen. n. sp. dino?agelle
provocant des eaux rouges. Vie Milieu, 11: 102-105.
3-Vila, M., Garcés, E., Masó, M. and Camp, J., 2001. Is the distribution
of the toxic dino?agellate Alexandrium catenellaexpanding along the NW
Mediterranean coast? Mar. Ecol. Prog. Ser.,222: 7383.
4-Garcés, E., Masó, M., Camp, J., 1999. A recurrent and localised
dino?agellate bloom in a Mediterranean beach. J. Plankton Res., 21:
5-Montresor, M., John, U., Beran, A., Poletti, R. and Medlin, L. 2002.
Alexandrium tamutum sp. nov., a new species closely related to A.
minutum. Abstracts of the X International Conference on Harmful Algae.
St. Pete Beach, Florida. p. 204.