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Harmful or nuisance algal blooms can cause economic damage to fisheries and tourism. Additionally, toxins produced by harmful algae and ingested via contaminated shellfish can be potentially fatal to humans. The seas around the Orkney Islands, UK currently hold a number of toxic algal species which cause shellfishery closures in most years. Extensive and costly monitoring programs are carried out to detect harmful microalgae before they reach action levels. However, the ability to distinguish between toxic and non-toxic strains of some algae is not possible using these methods. The microarrays for the detection of toxic algae (MIDTAL) microarray contains rRNA probes for toxic algal species/strains which have been adapted and optimized for microarray use. In order to investigate the use of the chip for monitoring in the Orkney Islands, samples were collected between 2009 and 2011 from Brings Deep, Scapa Flow, Orkney Islands, UK; RNA was extracted and hybridized with generation 2 and 3.1 of the chip. The data were then compared to cell counts performed under light microscopy and in the case of Alexandrium tamarense to qPCR data targeting the saxitoxin gene and the LSU-rRNA gene . A good agreement between cell numbers and microarray signal was found for A. tamarense, Pseudo-nitzschia sp., Dinophysis sp. ( r < 0.5, for all) in addition to this there the chip successfully detected a large bloom of Karenia mikimotoi ( r < 0.70) in August and September 2011. Overall, there was good improvement in probe signal between generation 2 and generation 3.1 of the chip with much less variability and more consistent results and better correlation between the probes. The chip performed well for A. tamarense group I signal to cell numbers in calibrations ( r > 0.9). However, in field samples, this correlation was slightly lower suggesting interactions between all species in the sample may affect signal. Overall, the chip showed it could identify the presence of target species in field samples although some work is needed to improve the quantitative nature of the chip before it would be suitable for monitoring in the Orkney Islands. [ABSTRACT FROM AUTHOR]

An investigation into the diversity of the dinoflagellate Alexandrium was carried out during August 2007 within two fjordic sea lochs in the Shetland Isles, Scotland. The co-occurrence in the water column of the non-toxic West European (W.E. or Gr.III) and the neurotoxic North American (N.A. or Gr.I) ribotypes of A. tamarense was demonstrated using fluorescent in situ hybridisation. A patch of A. tamarense (W.E.) localised at ∼10m depth and extending over 6km was detected in ‘Clift Sound’ with concentrations locally reaching ∼1×104 cellsl−1. A. tamarense (N.A.) was also observed there but despite the presence of toxins in net haul samples collected locally, concentrations were low and near limits of detection. Alexandrium concentrations were ∼1.5×103 cellsl−1 in ‘Vaila Sound’, where both W.E. and N.A. ribotypes were detected with equal relative abundances in some samples. Given the patchiness of A. tamarense populations and their possible organisation in thin layer structures, better vertical resolution through fine-scale sampling will be necessary for population dynamic studies. Implications for the shellfish industry are substantial since harmful microalgae patches may not be detected during routine monitoring. Moreover, the co-occurrence of morphologically indistinct toxic and non-toxic ribotypes will necessitate implementing molecular methods for their discrimination. [Copyright &y& Elsevier]

To determine the composition, abundance and horizontal distribution of resting cysts in modern coastal sediments from Scapa Flow, Orkney, Scotland, sediment samples were collected from 12 stations. Twenty-six dinoflagellate cyst types representing eight motile-defined genera and one cyst-defined genus were observed. Four species or species groups dominated the assemblage for the Flow as a whole, Scrippsiella trochoidea, unidentified round brown cysts, Polykrikos schwartzii and Alexandrium tamarense. Total cyst abundance ranged from 37-1524 cysts ml-1 wet sediment. The majority of cysts occurred in the central area of the Flow, where higher densities were observed. Of particular importance is the distribution and abundance of cysts of A. tamarense. Since 1991 there have been annual toxic episodes of paralytic shellfish poisoning, caused by the vegetative stage of A. tamarense, in Scapa Flow, leading to widespread bans on all shellfish activities for months at a time. Cysts of A. tamarense were widely distributed within the Flow and ranged from 0-212 cysts ml-1 wet sediment. The overall widespread distribution and higher abundances of cysts of A. tamarense in the central areas of the Flow indicate potential seedbeds for initiation of future vegetative growth and subsequent outbreaks of paralytic shellfish poisoning. [ABSTRACT FROM AUTHOR]