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Marine epibenthic dinoflagellates have been collected from macroalgae, dead corals, seagrasses and sand in Malaysia and identified using light microscopy, including epifluorescence microscopy, and scanning electron microscopy. Examination of 62 samples revealed that Malaysia has rich diversity of benthic dinoflagellates, with 24 species representing 9 genera. Of these species, 8 were shown to be potentially toxic using the Anemia bioassay test i.e. Prorocentrum arenarium, P. lima, P. concavum, P. cf. faustiae, Gambierdiscus pacificus, Ostreopsis labens, O. ovata and Coolia sp. The diversity of potentially toxic species in Malaysian waters indicates that Malaysia may encounter problems with ciguatera and/or DSP. The highest species diversity was found at Sipadan Island with a total of 18 species identified. One of these is previously undescribed (Prorocentrum sipadanensis sp. nov.). The most common species identified at all sampling sites were Prorocentrum lima and Ostreopsis ovata. Generally, the morphology of the species identified from Malaysian waters is similar to that reported in studies elsewhere. However, new features were also observed (e.g. a pyrenoid in Prorocentrum emarginatum and two different‐sized pores in Ostreopsis labens). The importance of SEM as a tool in taxonomic studies is stressed.

Field sampling was undertaken to investigate the occurrence of Pseudo-nitzschia Peragallo species in eight locations along the coast of Malaysian Borneo. A total of 108 strains of Pseudo-nitzschia species were isolated, and their morphology examined with SEM and TEM. Additionally, molecular data from nuclear-encoded partial LSU rDNA, and ITS regions, were characterized. A total of five species were confidently identified based on a combination of distinct morphological characteristics and supporting molecular evidence: P. brasiliana Lundholm, Hasle & Fryxell, P. cuspidata (Hasle) Hasle, P. dolorosa Lundholm & Moestrup, P. micropora Priisholm, Moestrup & Lundholm, and P. pungens (Grunow) Hasle var. pungens. However, one morphotype from Sarawak, while somewhat similar to P. caciantha, showed significant morphological distinction from this and any other of the currently described species. Most notably this morphotype possessed a characteristic pore arrangement in the poroids, with the fine pores in each perforation sector arranged in circles. Pair-wise sequence comparison of the LSU rDNA between this unidentified morphotype and P. caciantha Lundholm, Moestrup & Hasle, revealed 2.7% genetic divergence. Phylogenetic analyses strongly supported the monophyly of the morphotype. Based upon these supporting data it is here described as a new species, Pseudo-nitzschia circumpora sp. nov. A key to the six species of Pseudo-nitzschia from Malaysian Borneo is presented. Molecular signatures for all species were established based on structural comparisons of ITS2 rRNA transcripts.

Light, electron microscopy and DNA sequences of the dinoflagellate Prorocentrum concavum (syn. P. arabianum) with special emphasis on the periflagellar area

Harmful algal blooms (HABs) resulting in red discoloration of coastal waters in Sepanggar Bay, off Kota Kinabalu, Sabah, East Malaysia, were first observed in January 2005. The species responsible for the bloom, which was identified as Cochlodinium polykrikoides, coincided with fish mortalities in cage-cultures. Determinations of cell density between . Cell abundance reached a maximum value of 6 Â 10 6 cells L À1 at the fish cage sampling station where the water quality was characterized by high NO 3 -N and PO 4 -P concentrations. These blooms persisted into August 2005, were not detected during the north-east monsoon season and occurred again in May 2006. Favorable temperature, salinity and nutrient concentrations, which were similar to those associated with other C. polykrikoides blooms in the Asia Pacific region, likely promoted the growth of this species. Identification of C. polykrikoides as the causative organism was based on light and scanning microscopy, and confirmed by partial 18S ribosomal DNA sequences of two strains isolated during the bloom event (GenBank accession numbers DQ915169 and DQ915170). #

Coolia is a widespread and ecologically important genus of benthic marine dinoflagellates found in tropical regions. Historically, there has been taxonomic confusion about the taxonomy and toxicity of this group. The goal of this study was to resolve morphological questions concerning Coolia tropicalis and determine the taxonomic identity of the Australian Coolia isolate which has been reported to produce cooliatoxins. To accomplish this, the morphology of tropical strains from Belize (the type locality of C. tropicalis), Malaysia, Indonesia, and Australia were examined and compared to published reports. The morphological analysis showed that C. tropicalis differs from the original description in that it has a slightly larger size (35-47 μm long by 30-45 μm wide versus 23-40 μm long by 25-39 μm wide), and the shape of fourth apical plate, and the length of Po plate (7.4-12 μm versus 7 μm). Based on both morphology and phylogenetic analysis using LSU D1- D3 rDNA sequences, the clones of C. tropicalis from Malaysia, Indonesia, and Belize were found to form a monophyletic clade within the genus. The strain producing cooliatoxin was found to be C. tropicalis, not Coolia monotis as originally assumed. To explore the factors influencing the growth of Coolia species, the growth rates of C. tropicalis and Coolia malayensis were determined at different temperatures and salinities. Both species tolerated a wide range of temperatures, but cannot survive at temperatures <20°C or >35°C. C. monotis, the dominant species reported in the literature, probably does not produce toxins.

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