CHARACTERIZATION OF NW MEDITERRANEAN KARLODINIUM SPP. (DINOPHYCEAE) STRAINS USING MORPHOLOGICAL, MOLECULAR, CHEMICAL, AND PHYSIOLOGICAL METHODOLOGIES¹

Abstract

Recurrent fish kills in the Spanish Alfacs Bay (NW Mediterranean) have been detected during winter seasons since 1994, and were attributed to an unarmored, ichthyotoxic, dinoflagellate, initially identified as Gyrodinium corsicum Paulmier, Berland, Billard, & Nezan. Several strains were isolated from the bay and their clonal cultures were compared by combined techniques, including light and electron microscopy, internal transcribed spacer and 5.8S rDNA nucleotide sequencing, and HPLC pigment analyses, together with studies of their photochemical performance, growth rates, and toxicity. Using phylogenetic analyses, all strains were identified as members of the genus Karlodinium, but they were separated into two genetically distinct groups. These groups, identified as Karlodinium veneficum (Ballantine) J. Larsen and K. armiger Bergholtz, Daugbjerg et. Moestrup, were also supported by the other techniques used. Detailed analyses of fine structural characteristics (including plug-like structures in amphiesma and a possible layer of semi-opaque material beneath the outer membrane) allowed discrimination of the mentioned two species. Specific differences in pigment patterns coincided with that expected for low-(K. veneficum) and high-light (K. armiger) adapted relatives. The higher photosynthetic efficiency of K. veneficum and the longer reactivation times of the PSII reaction centers observed for K. armiger were in agreement with this hypothesis. The two species differed in toxicity, but the strains used always induced mortality when incubated with bivalves, rotifers, and finfish. Compared with K. armiger, strains of K. veneficum yielded higher cell densities, but had lower growth rates.

Marine microalgae attack and feed on metazoans

“…cultures (410 000 cells ml À 1 ) ( Table 1). The densities used represent commonly occurring Karlodinium bloom densities (blooms are often o10 000 cells ml À 1 and sometimes 100 000 cells ml À 1 ) (Garcés et al, 2006;Place et al, 2012). As control copepod treatments, we included copepods fed 20 000 cells ml À 1 of an unidentified phototrophic gymnodinoid dinoflagellate (North-East Atlantic origin; strain ID unavailable) and the cryptophyte Rhodomonas salina.…”

“…The widespread species K. veneficum represents one of the most problematic and well-studied toxic bloom-forming microalgae known (Garcés et al, 2006;Place et al, 2008;Mooney et al, 2009;Calbet et al, 2011) and has been recognised for its ichtyotoxicity (toxic to fish) since the 1950s (Braarud, 1957). Several aspects of its biology (Adolf et al, 2008), toxins (Deeds et al, 2002;Van Wagoner et al, 2010) and harmful effects on fish (Nielsen, 1993) have been described in detail and were recently reviewed (Place et al, 2011).…”

“…armiger is much less studied than K. veneficum (Daugbjerg et al, 2000;Bergholtz et al, 2005), and Karlotoxin production has not been reported in any strains of K. armiger. The species has been reported to produce a different substance with neurotoxic activity (Garcés et al, 2006), but the specific toxin has not been isolated and chemically characterised. While K. veneficum seems to prefer cryptophytes as food (Li et al, 1999;Adolf et al, 2008), K. armiger ingests most types of unicellular prey offered.…”

Taming the smallest predators of the oceans

“…Scanning electron microscopy (SEM) SEM was performed as in Garcés et al (2006). Samples were fixed for 2 h in 2% OsO 4 diluted in seawater, or with 2% glutaraldehyde.…”

Toxigenic algae and associated phycotoxins in two coastal embayments in the Ebro Delta (NW Mediterranean)

“…Other dinoflagellates known to produce lipophilic phycotoxins have also been detected in both bays, including Protoceratium reticulatum, a possible source of yessotoxins in Ebro Delta shellfish , Lingulodinium polyedrum and Prorocentrum lima. In addition, high biomass blooms dominated by the ichthyotoxic dinoflagellates Karlodinium armiger and Karlodinium veneficum (formerly known collectively as Gyrodinium corsicum in this area, compare Garcé s et al, 2006) has led to severe fish-kills in Alfacs Bay and land-based aquaculture facilities . In Fangar Bay, no high cell abundances were detected until June 2010 (Busch et al, 2012;Ferná ndez-Tejedor et al, 2010;Llebot et al, 2011).…”