Eileen Bresnan

Distribution, diversity and toxin composition of the genus Alexandrium (Dinophyceae) in Scottish waters

Alexandrium is detected throughout Scottish coastal waters on a near annual basis, and corresponding paralytic shellfish poisoning (PSP) toxins are found in Scottish shellfish. Previous studies at selected Scottish sites have shown diversity within the genus Alexandrium. In order to examine the distribution, diversity and toxicity of Alexandrium populations around the Scottish coast, historic cyst and cell data were compiled and cultures established from sediment and water samples. Historic data showed high cell densities of Alexandrium in Shetland, Orkney, the Western Isles and mainland east coast. Low abundances of Alexandrium cysts were observed along the west coast. Four species of Alexandrium (A. tamarense, A. ostenfeldii, A. minutum and A. tamutum) were established in laboratory culture and identified using morphological criteria. Sequencing of LSU rDNA from isolates of A. ostenfeldii, A. minutum and A. tamutum confirmed their identification and showed them to be similar to other European strains. Alexandrium tamarense, identified by morphological criteria, was observed to have a widespread distribution around the coast. Both toxin- and non toxin-producing strains of this species were isolated, suggesting the presence of A. tamarense Groups I and III. Alexandrium ostenfeldii was isolated from the east coast and Shetland Isles and was observed to produce both spirolide and PSP toxins. Alexandrium tamutum was identified from cultures isolated from Shetland and Orkney, the most northerly observation of this species to date. PSP toxins were not detected in isolates of A. minutum from the east coast and Orkney or of A. tamutum under the culture conditions used. This study has highlighted the diversity of Alexandrium in Scottish waters and reveals the requirement for temporal and regional studies on a species level in order to understand the variation in cell densities and PSP toxicity that is observed on an annual and decadal scale.

Shellfish toxicity in UK waters: a threat to human health?

The potential for poisoning of humans through their consumption of shellfish which have themselves consumed biotoxin producing marine phytoplankton exists in the UK. Toxins are bio-accumulated within the shellfish flesh allowing them to reach harmful concentrations. This threat is in most part mitigated by monitoring programmes that assess both the presence of potentially harmful phytoplankton and shellfish flesh toxicity. However, the medical profession in the UK remains relatively ignorant of the potential for biotoxin derived shellfish toxicity, preventing quantification of magnitude, frequency, and severity of health effects in the community or the medical significance of more recently discovered toxins. While the current causative species and their toxins are relatively well characterised there remains a lack of understanding of the factors governing the temporal and spatial appearance of harmful phytoplankton. Expansion of shellfish aquaculture is likely both worldwide and in the UK. Better understanding of how harmful phytoplankton interact with their environment to promote the sporadic harmful blooms that we observe is required to underpin risk assessments.

An adaptive approach to detect high-biomass algal blooms from EO chlorophyll-a data in support of harmful algal bloom monitoring

High-biomass harmful algal blooms can kill farmed fish through toxicity, physical effects or de-oxygenation of the water column. These blooms often form over spatially large areas meaning that Earth observation is well placed to monitor and study them. In this letter, we present a statistical-based background subtraction technique that has been modified to detect high-biomass algal blooms. The method builds upon previous work and uses a statistical framework to combine spatial and temporal information to produce maps of bloom extent. Its statistical nature allows the approach to characterize the region of interest meaning that region-specific tuning is not needed. The accuracy of the approach has been evaluated using Moderate Resolution Imaging Spectroradiometer (MODIS) data and an in situ cell concentration dataset, resulting in a correct classification rate of 68.0% with a false alarm rate of 0.24 (n = 25). The method is then used to study the surface coverage of a large high-biomass harmful algal bloom of Karenia mikimotoi. The approach shows promise for the early warning of spatially large high-biomass algal blooms, providing valuable information to support in situ sampling campaigns.

Diversity and seasonality of Pseudo-nitzschia (Peragallo) at two North Sea time-series monitoring sites

Abstract Species within the diatom genus Pseudo-nitzschia (Peragallo) have been identified as producers of domoic acid, the toxin responsible for amnesic shellfish poisoning. Toxin- and non-toxin-producing species of Pseudo-nitzschia have been reported globally; however, as Pseudo-nitzschia species cannot be routinely identified to species level using light microscopy, cells are rarely recorded to species level during long-term monitoring studies. Here, we report the results of a comparative survey of Pseudo-nitzschia species at two monitoring sites in the North Sea: Stonehaven on the east coast of Scotland and Helgoland Roads in the German Bight. A difference in the seasonality of this genus was observed between the sites with Pseudo-nitzschia cells playing a major role in the spring bloom as well at the summer and autumn diatom community at Stonehaven. In contrast, Pseudo-nitzschia was abundant only during the summer months at Helgoland. Pseudo-nitzschia cells constitute a higher proportion of the diatom community at Stonehaven than at Helgoland, particularly during the late summer, autumn and winter and thus may be considered more ‘ecologically important’ at this site. A total of eight different species were recorded during this survey with five Pseudo-nitzschia species observed at the Helgoland site: P. pungens, P. fraudulenta, P. americana, P. cf. delicatissima and the potentially toxic species P. multiseries. Six species were also recorded at Stonehaven; P. australis, P cf. delicatissima, P. pungens, P. cf. pseudodelicatissima, P. subpacifica and P. seriata. This study represents the first examination of the seasonality of Pseudo-nitzschia species around Helgoland and the first comparison between two long-term monitoring sites in the North Sea. P. americana and P. multiseries are also recorded at the Helgoland Roads time-series site for the first time.

GlobalHAB: Fostering International Coordination on Harmful Algal Bloom Research in Aquatic Systems

GlobalHAB, “Global Harmful Algal Blooms,” is a new scientific programme on harmful algal blooms (HABs) cosponsored by the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the Scientific Committee on Oceanic Research (SCOR) that will operate for 10 years from 2016 to 2025. GlobalHAB builds on the solid foundation established by the former programme GEOHAB and will continue to promote coordinated international scientific activities, which is fundamental to keep progressing on the comprehension of the global complexity of HABs and that will contribute to the management and mitigation of their impacts worldwide. The GlobalHAB Scientific and Implementation Plan is briefly presented in this chapter.

The relationship between Pseudo-nitzschia (Peragallo) and domoic acid in Scottish shellfish

The diatom genus Pseudo-nitzschia (Peragallo) associated with the production of domoic acid (DA), the toxin reposnsible for amnesic shellfish poisoning, is abundant in Scottish waters. A two year study examined the relationship between Pseudo-nitzschia cells in the water column and DA concentration in blue mussels (Mytilus edulis) at two sites, and king scallops (Pecten maximus) at one site. The rate of DA uptake and depuration differed greatly between the two species with M. edulis whole tissue accumulating and depurating 7μgg-1 (now expressed as mgkg-1) per week. In contrast, it took 12 weeks for DA to depurate from P. maximus gonad tissue from a concentration of 68μgg-1 (now mgkg-1) to <20μgg-1 (now mgkg-1). The DA depuration rate from P. maximus whole tissue was <5% per week during both years of the study. Correlations between the Pseudo-nitzschia cell densities and toxin concentrations were weak to moderate for M. edulis and weak for P. maximus. Seasonal diversity on a species level was observed within the Pseudo-nitzschia genus at both sites with more DA toxicity associated with summer/autumn Pseudo-nitzschia blooms when P. australis was observed in phytoplankton samples. This study reveals the marked difference in DA uptake and depuration in two shellfish species of commercial importance in Scotland. The use of these shellfish species to act as a proxy for DA in the environment still requires investigation.

Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea

The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to shelf break and oceanic stations in the study area.

Harmful algal blooms in the Eastern North Atlantic Ocean

Applying a mathematical model to the period 1982–2016, in PNAS Gobler et al. (1) propose that ocean warming has expanded the niche for harmful algal blooms (HABs) of the species Dinophysis acuminata and Alexandrium fundyense , which can generate shellfish toxicity and pose risks to human health. The authors’ model predicts an increase in the growth rate and in the duration of the bloom season for these species, with a “hot spot” being the North Eastern Atlantic (NEA) and North Sea (NS) waters surrounding the United Kingdom. Using ships of opportunity, the Continuous Plankton Recorder (CPR) has surveyed offshore phytoplankton populations (including Dinophysis , but not Alexandrium ) in this region since 1958 (2). We used Dinophysis spp. data to evaluate the model’s predictions, as species data … [↵][1]1To whom correspondence should be addressed. Email: paul.dees{at}sams.ac.uk. [1]: #xref-corresp-1-1

Pelagic habitat: exploring the concept of good environmental status

Acknowledgements This food for thought contribution was initiated by theme session J “What is a good pelagic habitat?” at the 2016 ICES annual science conference http://www.ices.dk/news-and-events/asc/ASC2016/Pages/Theme-session-J.aspx. All who took part in the session are thanked for their contributions. All participants were welcome to contribute to this article. Funding J. F. Tweddle was supported by the Natural Environment Research Council [NERC grant reference number NE/P005756/1]. E. Bresnan was supported by the Scottish Government’s schedules of service ST02a and ST03r. A. McQuatters-Gollop was supported by the Natural Environment Research Council [NERC grant reference number NE/L002663/1].

Environmental control of harmful dinoflagellates and diatoms in a fjordic system

Fjordic coastlines provide an ideal protected environment for both finfish and shellfish aquaculture operations. This study reports the results of a cruise to the Scottish Clyde Sea, and associated fjordic sea lochs, that coincided with blooms of the diarrhetic shellfish toxin producing dinoflagellate Dinophysis acuta and the diatom genus Chaetoceros, that can generate finfish mortalities. Unusually, D. acuta reached one order of magnitude higher cell abundance in the water column (2840cellsL-1) than the more common Dinophysis acuminata (200cellsL-1) and was linked with elevated shellfish toxicity (maximum 601±237μg OA eq/kg shellfish flesh) which caused shellfish harvesting closures in the region. Significant correlations between D. acuta abundance and that of Mesodinium rubrum were also observed across the cruise transect potentially supporting bloom formation of the mixotrophic D. acuta. Significant spatial variability in phytoplankton that was related to physical characteristics of the water column was observed, with a temperature-driven frontal region at the mouth of Loch Fyne being important in the development of the D. acuta, but not the Chaetoceros bloom. The front also provided important protection to the aquaculture located within the loch, with neither of the blooms encroaching within it. Analysis based on a particle-tracking model confirms the importance of the front to cell transport and shows significant inter-annual differences in advection within the region, that are important to the harmful algal bloom risk therein.