Development of Molecular Identification Method for Genus Alexandrium (Dinophyceae) Using Whole-Cell FISH

Differential feeding by common heterotrophic protists on 12 different Alexandrium species

N. Touzet and R. Raine. 2007. Discrimination of Alexandrium andersoni and A. minutum (Dinophyceae) using LSU rRNA-targeted oligonucleotide probes and fluorescent whole-cell hybridization. Phycologia 46: 168–177. DOI: 10.2216/06-11.1Toxic marine dinoflagellates from the genus Alexandrium have been responsible for paralytic shellfish poisoning (PSP) throughout the world. Their monitoring relies on spatial and temporal sampling strategies and requires the reliable identification and enumeration of vegetative stages in order to enable the development of early warning policies. The accurate discrimination between Alexandrium species is labour intensive and requires taxonomic expertise as the genus contains morphologically similar toxic and non-toxic species. In Ireland, PSP outbreaks so far have been limited to Cork Harbour, a retentive inlet located on the south coast of the country, where the causative organism has been identified as A. minutum. Recently, the non-toxic and morphologically similar species A. andersoni has been detected on the south west coast of Ireland. In routine monitoring, Alexandrium spp. are identified on the basis of morphological features by conventional light microscopy, a method which does not allow their characterization at the species level. The development and application of large subunit (LSU) rRNA-targeted oligonucleotide probes for the detection and quantification of A. minutum (Global clade) and A. andersoni by whole-cell fluorescent in situ hybridization (FISH) is reported. The specificity and sensitivity of the two probe sets (MinA and AndA′ +C) were evaluated against Alexandrium species, including A. tamarense, A. tamutum and A. ostenfeldi, and a range of common dinoflagellates usually co-occurring with Alexandrium in Irish coastal waters. No cross-reactivity was observed with any of the strains tested or with phytoplankton species present in field samples rich in dinoflagellates. The format of the assay overcame possible matrix effects, such as probe adsorption, and allowed the reliable labelling of at least 1000 cells. Furthermore, the simultaneous use of calcofluor during the assays permitted the confirmation of the probe diagnostics by examining the general plate structure of the thecae of labelled cells.

Discovery of a New Clade Nested Within the Genus Alexandrium (Dinophyceae): Morpho-molecular Characterization of Centrodinium punctatum (Cleve) F.J.R. Taylor

The dinoflagellate genus Alexandrium is one of the major harmful algal bloom (HAB) genera with respect to the diversity, magnitude and consequences of blooms. The ability of Alexandrium to colonize multiple habitats and to persist over large regions through time is testimony to the adaptability and resilience of this group of species. Three different families of toxins, as well as an as yet incompletely characterized suite of allelochemicals are produced among Alexandrium species. Nutritional strategies are equally diverse, including the ability to utilize a range of inorganic and organic nutrient sources, and feeding by ingestion of other organisms. Many Alexandrium species have complex life histories that include sexuality and often, but not always, cyst formation, which is characteristic of a meroplanktonic life strategy and offers considerable ecological advantages. Due to the public health and ecosystem impacts of Alexandrium blooms, the genus has been extensively studied, and there exists a broad knowledge base that ranges from taxonomy and phylogeny through genomics and toxin biosynthesis to bloom dynamics and modeling. Here we present a review of the genus Alexandrium, focusing on the major toxic and otherwise harmful species.

Gene duplication, loss and selection in the evolution of saxitoxin biosynthesis in alveolates

Seasonal change and subniche dynamics of three Alexandrium species in the Korea Strait

The present study describes the morphology, taxonomy, and distribution of species belonging to the diatom genus Rhizosolenia in Korea's marine coastal waters.From September 2008 to February 2010, we collected phytoplankton samples at 30 sites along the Korean coastline and studied them by light and scanning electron microscopy.We found 6 rhizosolenid genera in our samples: Rhizosolenia, Dactyliosolen, Guinardia, Pseudosolenia, Proboscia, and Neocalyptrella.In the present paper, we studied the following rhizosolenid species and compared them with congeners: R. pungens, R. fallax, R. imbricata, Rhizosolenia sp. 1, and Rhizosolenia sp. 2. The morphology of R. pungens exhibits important diagnostic characteristics in its girdle segment structure in the column and in its external process.To distinguish R. fallax and R. imbricata, the most important characteristics are the striation and the velum structure.R. pungens occurred in our samples all along the Korean coast.Only rarely did we find R. imbricata in the samples and at low abundance.We recorded R. fallax, Rhizosolenia sp. 1 and Rhizosolenia sp. 2 for the first time in Korean waters, but they rarely occurred.

Tributyltin (TBT) concentrations were determined in seawater, sediments and bivalve samples collected from Korean coastal areas during 2001-2005, to investigate the levels and temporal variation in TBT contamination in relation to the timing of the imposition of regulations on TBT use in Korea. TBT concentrations ranged from <5.0 to 164 ng/L in seawater, from <7.0 to 9,576 ng/g dry weight in sediments, and from <7.0 to 6,296 ng/g dry weight in bivalves. The highest concentrations of TBT were found at locations close to intensive shipping traffic and industrial complexes, and the contamination at some hot spot areas was high enough to cause harmful effects on marine organisms. TBT concentrations and their occurrence in Korean coastal waters have been decreasing annually. In particular, TBT concentrations in seawater have dramatically decreased. This result is consistent with regulations and bans on the use of TBT in Korea.

This paper summarizes information on the resting cysts of the dinoflagellate genus Alexandrium Halim, 1960 from the northwestern Pacific Ocean and the Chukchi Sea. Species of the genus Alexandrium, which are known as producers of paralytic toxins, cause large-scale algal blooms that pose a serious threat to marine coastal ecosystems and human health. Data are presented on the diversity, abundance, and distribution of Alexandrium spp. cysts in the Far Eastern seas of Russia and adjacent waters. The possible role of resting cysts in initiating toxic blooms of Alexandrium spp. is discussed.

Hypoxia and benthic community recovery in Korean coastal waters

Occurrence and accumulation features of polycyclic aromatic hydrocarbons and synthetic musk compounds in finless porpoises (Neophocaena phocaenoides) from Korean coastal waters

In this study, single-input transfer function model is applied to forecast monthly mean sea surface temperature(SST) in 2010 at Yeosu in Korean coastal waters. As input series, monthly mean air temperature series for ten years(2000-2009) at Yeosu in Korea is used, and Monthly mean SST at Yeosu station in Korean coastal waters is used as output series(the same period of input). To build transfer function model, first, input time series is prewhitened, and then cross-correlation functions between prewhitened input and output series are determined. The cross-correlation functions have just two significant values at time lag at 0 and 1. The lag between input and output series, the order of denominator and the order of numerator of transfer function, (b, r, s) are identified as (0, 1, 0). The selected transfer function model shows that there does not exist the lag between monthly mean air temperature and monthly mean SST, and that transfer function has a first-order autoregressive component for monthly mean SST, and that noise model was identified as . The forecasted values by the selected transfer function model are generally higher than actual SST in 2010 and have 6.4 % mean absolute percentage error(MAPE). The error is 2 % lower than MAPE by ARIMA model. This implies that transfer function model could be more available than ARIMA model in terms of forecasting performance of SST.

Morphology and molecular phylogeny of a new PST-producing dinoflagellate species: Alexandrium fragae sp. nov. (Gonyaulacales, dinophyceae)

Various species of Alexandrium can produce a number of bioactive compounds, e.g., paralytic shellfish toxins (PSTs), spirolides, gymnodimines, goniodomins, and also uncharacterised bioactive extracellular compounds (BECs). The latter metabolites are released into the environment and affect a large range of organisms (from protists to fishes and mammalian cell lines). These compounds mediate allelochemical interactions, have anti-grazing and anti-parasitic activities, and have a potentially strong structuring role for the dynamic of Alexandrium blooms. In many studies evaluating the effects of Alexandrium on marine organisms, only the classical toxins were reported and the involvement of BECs was not considered. A lack of information on the presence/absence of BECs in experimental strains is likely the cause of contrasting results in the literature that render impossible a distinction between PSTs and BECs effects. We review the knowledge on Alexandrium BEC, (i.e., producing species, target cells, physiological effects, detection methods and molecular candidates). Overall, we highlight the need to identify the nature of Alexandrium BECs and urge further research on the chemical interactions according to their ecological importance in the planktonic chemical warfare and due to their potential collateral damage to a wide range of organisms.

D.E. Buetow The Biology of Euglena. Volume IV: Subcellular Biochemistry and Molecular Biology 1989 Academic Press, Inc. San Diego 0-12-139904-4 etc., 528 pp., £ 95.-