Robin Raine

CONFIRMATION OF DOMOIC ACID PRODUCTION BY PSEUDO‐NITZSCHIA AUSTRALIS (BACILLARIOPHYCEAE) ISOLATED FROM IRISH WATERS1

A nonaxenic isolate of the potentially toxic diatom Pseudo‐nitzschia australis (Frenguelli) from Irish waters was tested in two separate batch culture experiments. When grown under a low irradiance (∼12 μmol photons·m−2·s− 1 ; 16:8‐h light:dark cycle) for up to 40 days, the culture produced only trace amounts of the neurotoxin domoic acid (DA) during late stationary phase. Growth at a higher irradiance (∼115 μmol photons·m−2·s− 1 ; 12:12‐h light:dark cycle) resulted in DA production starting during late exponential phase and reaching a maximum concentration of 26 pg DA·cell− 1 during late stationary phase. Liquid chromatography coupled to mass spectrometry was used to confirm the identity of DA in the culture. Irradiance and photoperiod could be important factors that contribute directly or indirectly to the control of DA production in P. australis. This is the first record of a DA‐producing diatom in Irish waters, and results indicate P. australis may have been the source of DA that has recently contaminated shellfisheries in this area.

Megacities and Large Urban Agglomerations in the Coastal Zone: Interactions Between Atmosphere, Land, and Marine Ecosystems

Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management.

Characterization of Nontoxic and Toxin-Producing Strains of Alexandrium minutum (Dinophyceae) in Irish Coastal Waters

ABSTRACT A comparative analysis of the morphology, toxin composition, and ribosomal DNA (rDNA) sequences was performed on a suite of clonal cultures of the potentially toxic dinoflagellate Alexandrium minutum Halim. These were established from resting cysts or vegetative cells isolated from sediment and water samples taken from the south and west coasts of Ireland. Results revealed that strains were indistinguishable, both morphologically and through the sequencing of the D1-D2 domain of the large subunit and the ITS1-5.8S-ITS2 regions of the rDNA. High-performance liquid chromatography fluorescence detection analysis, however, showed that only strains derived from retentive inlets on the southern Irish coast synthesized paralytic shellfish poisoning (PSP) toxins (GTX2 and GTX3), whereas all strains of A. minutum isolated from the west coast were nontoxic. Toxin analysis of net hauls, taken when A. minutum vegetative cells were in the water column, revealed no PSP toxins in samples from Killary Harbor (western coast), whereas GTX2 and GTX3 were detected in samples from Cork Harbor (southern coast). These results confirm the identity of A. minutum as the most probable causative organism for historical occurrences of contamination of shellfish with PSP toxins in Cork Harbor. Finally, random amplification of polymorphic DNA was carried out to determine the degree of polymorphism among strains. The analysis showed that all toxic strains from Cork Harbor clustered together and that a separate cluster grouped all nontoxic strains from the western coast.

Evaluation of taxa-specific real-time PCR, whole-cell FISH and morphotaxonomy analyses for the detection and quantification of the toxic microalgae Alexandrium minutum (Dinophyceae), Global Clade ribotype.

The dinoflagellate genus Alexandrium contains neurotoxin-producing species that have adversely affected the aquaculture industry in many countries. The morphological similarity between Alexandrium species has led to the development of molecular methods for the discrimination, enumeration and monitoring of toxic and nontoxic species. A quantitative real-time PCR assay (qRT-PCR) targeting the internal transcribed spacer 1-5.8S rRNA gene using hybridization probe technology was developed for the potentially toxic species Alexandrium minutum (Global Clade) (GC). The assay was specific with a detection limit of less than one cell equivalent. The assay was used to detect and quantify A. minutum (GC) in seawater samples collected during summer 2007 in Cork Harbour, Ireland. The results were compared with those obtained using whole-cell FISH (WC-FISH) and morphotaxonomy analyses. Alexandrium minutum did not reach high bloom concentrations over the sampling period (maximum of c. 6 x 10(4) cells L(-1)), and the average concentrations determined using qRT-PCR, WC-FISH and morphotaxonomy did not significantly differ in eight of nine comparisons. Regression curves showed positive relationships between the methods; WC-FISH and qRT-PCR slightly under- and overestimated, respectively, the A. minutum concentrations compared with the morphotaxonomy method. The qRT-PCR assay for A. minutum (GC) offers high-throughput sample analysis and may prove suitable for implementation in microalgae monitoring programmes and assist in population dynamics studies of the species.

A satellite and field portrait of a Karenia mikimotoi bloom off the south coast of Ireland, August 1998

An extensive surface bloom of the dinoflagellate Karenia mikimotoi occurred off southwestern Ireland during August, 1998. The bloom was evident both from remotely sensed satellite ocean colour data and as visibly discoloured water, from the mouth of Bantry Bay around towards Cork, extending some 60 km offshore. The timing of the bloom co-incided with a field survey in the area. This paper compares the surface distributions of chlorophyll and K. mikimotoi concentrations with satellite ocean colour and thermal infra-red sea surface temperature images, from which may be derived the origins of the bloom. It would appear that weak coastal upwelling transported a thermocline population of K. mikimotoi up to the surface in the region of the Fastnet Rock, where it was wind-dispersed eastwards across the northern Celtic Sea.

Phytoplankton and particulate matter in Carlingford Lough, Ireland: An assessment of food availability and the impact of bivalve culture

In an attempt to assess the impact of bivalve culture in Carlingford Lough, Ireland, the seasonal cycles of nutrients, particulate matter, chlorophylla, and phytoplankton in the lough was investigated in 1992. Chlorophyll levels showed an increase in April, corresponding to the annual spring bloom, and levels remained relatively high (2–12 mg m−3) throughout the summer before dropping to a winter minimum by December. Throughout the summer the phytoplankton community was dominated by diatoms, with microflagellates becoming an increasingly larger fraction of the biomass in autumn and winter. Dinoflagellates were only present on occasion in low numbers during the summer months. Seasonal variations in nitrate, phosphate, and silicate concentrations at all stations showed characteristic winter maxima and summer minima. Nitrate concentrations had reached a minimum undetectable level by June, at a time when the main freshwater input from the Clanrye River had dropped to <0.3 m3 s−1. Particulate organic carbon (POC) composed approximately 5% of the suspended matter, with highest values in winter due to resuspension. Levels of biologically available POC, as determined by a modified BOD technique, were greatest in summer, and an inverse relationship was observed between total POC and its fraction that was biologically available. Most of the labile fraction was considered to be phytoplankton, and remineralization during the summer is suggested as a mechanism for maintaining high productivity during the summer months. Although the phytoplankton biology was uncoupled with that outside the lough, it is concluded that there is scope for expansion of the local bivalve mariculture industry without altering the ecosystem of the lough. The upper limit on such expansion would be set by practical considerations such as availability of space and site suitability due to water quality.

Discrimination of Alexandrium andersoni and A. minutum (Dinophyceae) using LSU rRNA-targeted oligonucleotide probes and fluorescent whole-cell hybridization

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: 10.2216/06-11.1 Toxic 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.

Import, mortality and accumulation of coastal phytoplankton in a partially mixed estuary (Kinsale harbour, Ireland)

In order to study the importance of phytoplankton as a food source for benthic consumers, Kinsale harbour, a small estuary in the southwest of Ireland, was sampled on a monthly basis during the course of 1994. Nutrients, salinity, temperature, pigments (chlorophyll a and phaeopigments) and phytoplankton species composition were determined along longitudinal and vertical profiles. Based on salinity distributions, Kinsale harbour can be classified as a partially mixed estuary. River discharge and tidal mixing result in a strong estuarine circulation and an intensive exchange between the estuary and coastal waters. As a result, residence time is too low (< 1 day) for autochthonous phytoplankton populations to develop and phytoplankton observed in Kinsale harbour is predominantly advected from coastal waters. High concentrations of phaeopigments, exceeding those of chlorophyll a, were observed at the uppermost stations sampled, suggesting mass mortality and accumulation of coastal phytoplankton within the estuary. Possible causes for this phenomenon include osmotic stress or grazing by macrozooplankton within the estuary and the subsequent entrapment of senescent phytoplankton or faecal pellets in the baroclinic circulation near the salt wedge. It is suggested that in small estuaries, like Kinsale harbour, which are strongly influenced by river discharge, estuarine circulation induces the import of coastal phytoplankton into the estuary and provides an allochthonous carbon source to consumers within the estuary.

An evaluation of the applicability of microarrays for monitoring toxic algae in Irish coastal waters

The applicability of microarrays to monitor harmful algae across a broad range of ecological niches and toxic species responsible for harmful algal events has been one of the key tasks in the EU Seventh Framework Programme (FP7)-funded Microarrays for the Detection of Toxic Algae project. The technique has a strong potential for improving speed and accuracy of the identification of harmful algae and their toxins to assist monitoring programmes. Water samples were collected from a number of coastal sites around Ireland, including several that are used in the Irish National Phytoplankton and Biotoxin Monitoring Programme. Ribosomal RNA was extracted from filtered field samples, labelled with a fluorescent dye, and hybridised to probes spotted in a microarray format on a glass slide. The fluorescent signal intensity of the hybridisation to >120 probes on the chip was analysed and compared with actual field counts. There was a general agreement between cell counts and microarray signal. Results are presented for field samples taken from a range of stations along the Irish coastline known for harmful algal events during the first field trial (July 2009–April 2010).

The influence of bloom intensity on the encystment rate and persistence of Alexandrium minutum in Cork Harbor, Ireland

Toxic Alexandrium minutum blooms recur annually in Cork Harbor, Ireland where they initiate in an inlet known as the North Channel. The dynamics of these blooms have been studied since 2003, and a high degree of inter-annual variability in the cell densities has been observed. Two intense blooms, with maximum cell densities >500,000cellsL-1, were observed in the summers of 2004 and 2011. Annual cyst surveys during winter found that cyst densities decreased after the 2004 bloom, and by 2010 an average of ca. 40 cystsg dry wt sediment-1 was recorded. The intensity of blooms was found to be independent of the cyst density measured the previous winter. The cyst input to the sediment during both intense and low density blooms was measured directly through the deployment of sediment traps in the North Channel. The data allowed an estimate of the proportion of the A. minutum vegetative cells that underwent successful encystment, which averaged at 2.5% across a range of cell densities spanning three orders of magnitude. Maturation times of fresh cysts were determined at 5, 10 and 15°C. The maturation time at 15°C was found to be approximately 5 months, a value which increased by two months for a 5° decrease in temperature. A cyst dynamics model was constructed based on the field data to simulate the temporal variation of A. minutum cysts in the oxic layer of sediment. It revealed that a degree of resuspension is required to prevent cyst stocks from becoming exhausted in the thin oxic layer at the surface of the sediment. The model also demonstrated that the cysts supplied by periodic intense blooms, which occur with a frequency of every 7-8 years, are not in themselves enough to allow the population to persist over long time scales (decades). The cyst input from interim blooms of lower density is however enough to ensure the annual inoculation of the water column with A. minutum cells.