Individual-based modelling of the development and transport of a Karenia mikimotoi bloom on the North-west European continental shelf

In 2006, a large and prolonged bloom of the dinoflagellate Karenia mikimotoi occurred in Scottish coastal waters, causing extensive mortalities of benthic organisms including annelids and molluscs and some species of fish (Davidson et al., 2009). A coupled hydrodynamic-algal transport model was developed to track the progression of the bloom around the Scottish coast during June–September 2006 and hence investigate the processes controlling the bloom dynamics. Within this individual-based model, cells were capable of growth, mortality and phototaxis and were transported by physical processes of advection and turbulent diffusion, using current velocities extracted from operational simulations of the MRCS ocean circulation model of the North-west European continental shelf. Vertical and horizontal turbulent diffusion of cells are treated using a random walk approach. Comparison of model output with remotely sensed chlorophyll concentrations and cell counts from coastal monitoring stations indicated that it was necessary to include multiple spatially distinct seed populations of K. mikimotoi at separate locations on the shelf edge to capture the qualitative pattern of bloom transport and development. We interpret this as indicating that the source population was being transported northwards by the Hebridean slope current from where colonies of K. mikimotoi were injected onto the continental shelf by eddies or other transient exchange processes. The model was used to investigate the effects on simulated K. mikimotoi transport and dispersal of: (1) the distribution of the initial seed population; (2) algal growth and mortality; (3) water temperature; (4) the vertical movement of particles by diurnal migration and eddy diffusion; (5) the relative role of the shelf edge and coastal currents; (6) the role of wind forcing. The numerical experiments emphasized the requirement for a physiologically based biological model and indicated that improved modelling of future blooms will potentially benefit from better parameterisation of temperature dependence of both growth and mortality and finer spatial and temporal hydrodynamic resolution.     

The potential threat of algal blooms to the abalone (Haliotis midae) mariculture industry situated around the South African coast

Toxic algal blooms are common world-wide and pose a serious problem to the aquaculture and fishing industries. Dinoflagellate species such as Karenia brevis, Karenia mikimotoi, Heterosigma akashiwo and Chatonella cf. antiqua are recognised toxic species implicated in various faunal mortalities. Toxic blooms of Karenia cristata were observed on the south coast of South Africa for the first time in 1988 and were responsible for mortalities of wild and farmed abalone. K. cristata and various other dinoflagellate species common along the South African coast, as well as K. mikimotoi (Isolation site: Norway, Univ. of Copenhagen) and K. brevis (Isolation site: Florida, BIGELOW), were tested for toxicity by means of a bioassay involving Artemia larvae as well as abalone larvae and spat. K. cristata, like K. brevis, contains an aerosol toxin; however, the toxin present in K. cristata has not yet been isolated and remains unknown. K. brevis was, therefore, used to determine which developmental phase of the bloom would affect abalone farms most, and whether ozone could be used as an effective mitigating agent. Of the 17 dinoflagellate species tested, K. cristata, Akashiwo sanguinea, K. mikimotoi and K. brevis pose the greatest threat to the abalone mariculture industry. K. brevis was most toxic during its exponential and stationary phases. Results suggest that ozone is an effective mitigation agent but its economic viability for use on abalone farms must still be investigated.     

A review of karenia mikimotoi: Bloom events,physiology, toxicity and toxic mechanism

Karenia mikimotoi is a worldwide bloom-forming dinoflagellate in the genus Karenia. Blooms of this alga have been observed since the 1930s and have caused mass mortalities of fish, shellfish, and other invertebrates in the coastal waters of many countries, including Japan, Norway, Ireland, and New Zealand. This species has frequently bloomed in China, causing great financial losses (more than 2 billion yuan, Fujian Province, 2012). K. mikimotoi can adapt to various light, temperature, salinity, and nutrient conditions, which together with its complex life history, strong motility, and density-dependent allelopathy, allows it to form blooms that are lethal to almost all marine organisms. However, its toxicity differs between subspecies and some target-species-specific toxicity has also been recorded. Significant gill disorder is observed in affected fish, to which the massive fish kills are attributed, rather than to the hypoxia that occurs in the fading stage of a bloom. However, although this species is haemolytic and cytotoxic, and generates reactive oxygen species, none of the isolated toxins or lipophilic extracts have toxic effects as extreme as those of the intact algal cells. The toxic effects of K. mikimotoi are strongly related to contact with intact cells. Several reasonable hypotheses of how and why this species blooms and causes mass mortalities have been proposed, but further research is required.     

Detrimental impacts of the dinoflagellate Karenia mikimotoi in Fujian coastal waters on typical marine organisms

Blooms of the toxic dinoflagellate Karenia mikimotoi (K. mikimotoi) have occurred frequently in the East China Sea in recent decades and were responsible for massive mortalities of abalones in Fujian coastal areas in 2012, however, little is known about the effects of these blooms on other marine organisms. In this study, the toxic effects and the possible mechanisms of toxicity of K. mikimotoi from Fujian coastal waters on typical marine organisms at different trophic levels, including zooplankton (Brachionus plicatilis, Artemia salina, Calanus sinicus, and Neomysis awatschensis) and aquaculture species (Penaeus vannamei and Scophthalmus maximus) were investigated. At a bloom density of 3 × 10⁴ cells/mL, the Fujian strain of K. mikimotoi significantly affected the tested organisms, which had mortality rates at 96 h of 100, 23, 20, 97, 33, and 53%, respectively. Moreover, the intact cell suspension was toxic to all tested species, whereas cell-free culture and the ruptured cell suspension had no significant effects on the tested organisms. Possible mechanisms for this toxic effect, including reactive oxygen species (ROS) and hemolytic toxins, were evaluated. For K. mikimotoi, 0.014 ± 0.004 OD/(10⁴ cells) superoxide (O₂⁻) and 3.00 ± 0.00 nmol/(10⁴ cells) hydrogen peroxide (H₂O₂) were measured, but hydrogen peroxide did not affect rotifers at that concentration, and rotifers were not protected from the lethal effects of K. mikimotoi when the enzymes superoxide dismutase and catalase were added to counteract the ROS. The lipophilic extract of K. mikimotoi had a hemolytic effect on rabbit erythrocytes but exhibited no significant toxicity. These results suggest that this strain of K. mikimotoi can have detrimental effects on several typical marine organisms and that its toxicity may be associated with intact cells but is not related to ROS or hemolytic toxins.     

Use of dissolved inorganic and organic phosphorus by axenic and nonaxenic clones of Karenia brevis and Karenia mikimotoi

Nearly annual blooms of the marine dinoflagellate Karenia brevis, which initiate offshore on the West Florida Shelf in oligotrophic waters, cause widespread environmental and economic damage. The success of K. brevis as a bloom-former is partially attributed to its ability to use a diverse suite of nutrients from natural and anthropogenic sources, although relatively little is known about the ability of K. brevis and the closely related Karenia mikimotoi to use a variety of organic sources of phosphorus, including phosphomonoesters, phosphodiesters, and phosphonates. Through a series of bioassays, this study characterized the ability of axenic and nonaxenic K. brevis and K. mikimotoi clones isolated from Florida waters to use a variety of organic phosphorus compounds as the sole source of phosphorus for growth, comparing this utilization to that of inorganic sources of phosphate. Differing abilities of axenic and nonaxenic K. brevis and K. mikimotoi cultures to use phosphorus from the compounds evaluated were documented. Specifically, growth of axenic cultures was greatest on inorganic phosphorus and was not supported on the phosphomonoester phytate, or generally on phosphodiesters or phosphonates. The nonaxenic cultures were able to use organic compounds that the axenic cultures were not able to use, often after lags in growth, highlighting a potential role of co-associated bacterial communities to transform nutrients to bioavailable forms. Given the ability of K. brevis and K. mikimotoi to use a diverse suite of inorganic and organic phosphorus, bloom mitigation strategies should consider all nutrient forms.     

Impacts of a ‘black tide’ harmful algal bloom on rocky-shore intertidal communities on the West Coast of South Africa

Algal blooms commonly occur along the South African west coast. In March 1994 a dense bloom developed within St Helena Bay. Its subsequent decay caused near-shore hypoxia and elevated hydrogen sulphide levels, leading to it being termed a ‘black tide’. The bloom caused immediate massive intertidal mortalities (95% reduction of biomass), significant changes in community structure, and declines in richness and diversity. Only four taxa were not diminished: ephemeral algae, the gastropod Afrolittorina knysnaensis, the anemone Bunodactis reynaudi and the false limpet Siphonaria capensis. This limpet species subsequently increased at impacted sites relative to controls, probably reflecting reduced competition from other grazers. Ephemeral algae flourished during early recolonisation while grazers were depleted, but declined as grazers re-established. Manipulative experiments demonstrated that grazers do have this capability. Perennial algae also flourished, but lagged behind ephemerals, possibly contributing to their decline. Predators took longest to recover. Differences in the responses of species reflect differing tolerances, zonation patterns and biological interactions. Communities at control sites remained unchanged over the four-year study, and those exposed to a low intensity of the bloom were little affected, but communities exposed to its full intensity failed to recover fully within four years. Increasing frequency of harmful algal blooms along the west coast of South Africa could, therefore, significantly alter rocky-shore communities if intervals between bloom events become shorter than recovery times.     

Occurrence of Amoebophrya spp. infection in planktonic dinoflagellates in Changjiang (Yangtze River) Estuary,China

The parasitic dinoflagellates in the genus of Amoebophrya can infect broad ranges of planktonic dinoflagellates, and transform algal biomass into organic matter that can be recycled within the planktonic community. The ecological significance of Amoebophrya spp. during harmful algal bloom (HAB) events was gradually recognized along with revelation of its host specificity and diversity in picoplankton communities. The eutrophicated coastal waters of China are frequently affected by HABs, particularly in Changjiang (Yangtze River) estuary and the adjacent East China Sea; while, no research has been conducted to explore the ecological roles of parasitism during HAB events and the related dinoflagellate bloom dynamics. For the first time, we confirmed the presence of Amoebophrya infections in the planktonic community of this region; six species of dinoflagellates were infected, including Ceratium tripos, Scrippsiella trochoidea, Gonyaulax spinifera, Gymnodinium sp., Gonyaulax sp. and an Alexandrium sp. Molecular sequences retrieved from environmental water samples revealed high genetic diversity of Amoebophryidae-like organisms in the water column. Amoebophrya-infected dinoflagellates were only observed in high salinity (>20) stations suggesting that salinity may be a factor limiting the distribution of Amoebophyra infections in natural environment. Whereas, no evidence of Amoebophrya infection was observed in the bloom-forming species Karenia mikimotoi, suggesting that K. mikimotoi in this region was likely free of Amoebophridae infection.     

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.     

Evidence for Production of Sexual Resting Cysts by the Toxic Dinoflagellate Karenia mikimotoi in Clonal Cultures and Marine Sediments

The toxic dinoflagellate Karenia mikimotoi has been well-known for causing large-scale and dense harmful algal blooms (HABs) in coastal waters worldwide and serious economic loss in aquaculture and fisheries and other adverse effects on marine ecosystems. Whether K. mikimotoi forms resting cysts has been a puzzling issue regarding to the mechanisms of bloom initiation and geographic expansion of this species. We provide morphological and molecular confirmation of sexually produced thin-walled resting cysts by K. mikimotoi based on observations of laboratory cultures and their direct detection in marine sediments. Light and scanning electron microscopy evidences for sexual reproduction include attraction and pairing of gametes, gamete fusion, formation of planozygote and thin-walled cyst, and the documentation of the thin-walled cyst germination processes. Evidence for cysts in marine sediments was in three aspects: positive PCR detection of cysts using species-specific primers in the DNA extracted from whole sediments; fluorescence in situ hybridization detection of cysts using FISH probes; and single-cell PCR sequencing for cysts positively labeled with FISH probes. The existence of sexually produced, thin-walled resting cysts by K. mikimotoi provides a possible mechanism accounting for the initiation of annually recurring blooms at certain regions and global expansion of the species during the past decades.     

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 (2840 cells L⁻¹) than the more common Dinophysis acuminata (200 cells L⁻¹) and was linked with elevated shellfish toxicity (maximum 601 ± 237 μg 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.     

Potential impact of an exceptional bloom of Karenia mikimotoi on dissolved oxygen levels in waters off western Ireland

In the summer of 2005 an exceptional bloom of the dinoflagellate Karenia mikimotoi occurred along Ireland's Atlantic seaboard and was associated with the mass mortality of both benthic and pelagic marine life. Oxygen depletion, cellular toxicity and physical smothering, are considered to be the main factors involved in mortality. In this paper we use a theoretical approach based on stoichiometry (the Anderson ratio) and an average K. mikimotoi cellular carbon content of 329 pg C cell⁻¹ (n = 20) to calculate the carbonaceous and nitrogenous oxygen demand following bloom collapse. The method was validated against measurements of biochemical oxygen demand and K. mikimotoi cell concentration. The estimated potential oxygen utilisation (POU) was in good agreement with field observations across a range of cell concentrations. The magnitude of POU following bloom collapse, with the exception of three coastal areas, was considered insufficient to cause harm to most marine organisms. This indicates that the widespread occurrence of mortality was primarily due to other factors such as cellular toxicity and/or mucilage production, and not oxygen depletion or related phenomena. In Donegal Bay, Kilkieran Bay and inner Dingle Bay, where cell densities were in the order of 10⁶ cells L⁻¹, estimated POU was sufficient to cause hypoxia. Of the three areas, Donegal Bay is considered to be the most vulnerable due to its hydrographic characteristics (seasonally stratified, weak residual flow) and hypoxic conditions (2.2 mg L⁻¹ O₂) were directly observed in the Bay post bloom collapse. Here, depending on the time of bloom collapse, depressed DO levels could persist for weeks and continue to have a potentially chronic impact on the Bay.     

Prorocentrum minimum (Pavillard) Schiller: A review of a harmful algal bloom species of growing worldwide importance

Prorocentrum minimum (Pavillard) Schiller, a common, neritic, bloom-forming dinoflagellate, is the cause of harmful blooms in many estuarine and coastal environments. Among harmful algal bloom species, P. minimum is important for the following reasons: it is widely distributed geographically in temperate and subtropical waters; it is potentially harmful to humans via shellfish poisoning; it has detrimental effects at both the organismal and environmental levels; blooms appear to be undergoing a geographical expansion over the past several decades; and, a relationship appears to exist between blooms of this species and increasing coastal eutrophication. Although shellfish toxicity with associated human impacts has been attributed to P. minimum blooms from a variety of coastal environments (Japan; France; Norway; Netherlands; New York, USA), only clones isolated from the Mediterranean coast of France, and shellfish exposed to P. minimum blooms in this area, have been shown to contain a water soluble neurotoxic component which killed mice. Detrimental ecosystem effects associated with blooms range from fish and zoobenthic mortalities to shellfish aquaculture mortalities, attributable to both indirect biomass effects (e.g., low dissolved oxygen) and toxic effects. P. minimum blooms generally occur under conditions of high temperatures and incident irradiances and low to moderate salinities in coastal and estuarine environments often characterized as eutrophic, although they have been found under widely varying salinities and temperatures if other factors are conducive for growth. The physiological flexibility of P. minimum in response to changing environmental parameters (e.g., light, temperature, salinity) as well as its ability to utilize both inorganic and organic nitrogen, phosphorus, and carbon nutrient sources, suggest that increasing blooms of this species are a response to increasing coastal eutrophication.     

Establishment and application of hyperbranched rolling circle amplification coupled with lateral flow dipstick for the sensitive detection of Karenia mikimotoi

The dinoflagellate Karenia mikimotoi is a noxious and harmful algal bloom (HAB)-forming microalga. Establishing a rapid, accurate, and sensitive method of detecting this harmful alga is necessary to provide warnings of imminent HABs through field monitoring. Here, an isothermal amplification technique combined with a rapid analytical method for nucleic acid-based amplified products, i.e., hyperbranched rolling circle amplification (HRCA) coupled with lateral flow dipstick (LFD), hereafter denoted as HRCA-LFD, was established to detect K. mikimotoi. The HRCA-LFD assay relied on a padlock probe (PLP) targeting DNA template and an LFD probe targeting PLP. The sequenced internal transcribed spacer of K. mikimotoi through molecular cloning was used as the target of PLP. The optimized HRCA conditions was determined to be as follows: PLP concentration, 20 pM; ligation temperature, 65 °C; ligation time, 10 min; amplification temperature, 61 °C; and amplification time, 30 min. The developed HRCA-LFD assay was specific for K. mikimotoi, displaying no cross-reactivity with other common microalgae. Sensitivity-comparison tests indicated that HRCA-LFD assay was 100-fold more sensitive than PCR, with a detection limit of 0.1 cell mL⁻¹ when used to analyze spiked field samples. The analysis with field samples also indicated that HRCA-LFD assay was suitable for samples with a target cell density range of 1–1000 cells mL⁻¹. All of these results suggested that HRCA-LFD assay is an alternative method for the sensitive and reliable detection of K. mikimotoi from marine water samples.     

Molecular ecological responses of the dinoflagellate Karenia mikimotoi to phosphate stress

Karenia mikimotoi is a toxic, widespread dinoflagellate which could produce hemolytic toxins and ichthyotoxins affecting fisheries within the area of its bloom. Previous ecophysiological studies indicated that the enhance of environmental phosphate concentration could promote the growth of K. mikimotoi. Intrinsic mechanisms regarding the effects of external phosphate on its photosynthesis, cell cycle succession and differential proteins’ expressions are still unknown. K. mikimotoi was cultured in phosphate-deprived medium, while the culture in f/2 medium (Guillard, 1975) was introduced as phosphate-sufficient control experiment. Cell counts and phosphate concentration detection were performed every other day. Flowcytometry was applied to measure cell cycle succession and chlorophyll fluorescence intensity fluctuation. Differential proteomics expression was examined by SDS-PAGE tandem LTQ Orbitrap MS/MS spectrometry. Functions of each differential protein were searched within NCBInr protein database and Swissprot database. Our study demonstrated that phosphate stress inhibited growth and cell cycle succession of K. mikimotoi remarkably (p < 0.01). Algal chlorophyll fluorescence intensity was significantly affected by phosphate deprivation (p < 0.05). 11 species of differential proteins were detected only in phosphate-limited culture sample which related to stress signal transduction, vacuolar phosphate release, phospholipid degradation, organic acid synthesis and phagotrophy. 4 kinds of differential proteins were identified only in f/2 medium culture sample which referred to cell proliferation, glycolysis, SAM cycle and polyamine production. Based on analysis of differential proteomic functional annotation, we hypothesized proteomic response mechanism of K. mikimotoi to phosphate stress. Molecular biological responses of dinoflagellate K. mikimotoi to phosphate stress was explored.     

Integrating multiple data sources to assess the distribution and abundance of bottlenose dolphins Tursiops truncatus in Scottish waters

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Combined physical,chemical and biological factors shape Alexandrium ostenfeldii blooms in The Netherlands

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations. Since 2012, dense Alexandrium ostenfeldii blooms (up to 4500 cells mL⁻¹) have recurred annually in a creek located in the southwest of the Netherlands, an area characterized by intense agriculture and aquaculture. We investigated how physical, chemical and biological factors influenced A. ostenfeldii bloom dynamics over three consecutive years (2013–2015). Overall, we found a decrease in the magnitude of the bloom over the years that could largely be linked to changing weather conditions during summer. More specifically, low salinities due to excessive rainfall and increased wind speed corresponded to a delayed A. ostenfeldii bloom with reduced population densities in 2015. Within each year, highest population densities generally corresponded to high temperatures, low DIN:DIP ratios and low grazer densities. Together, our results demonstrate an important role of nutrient availability, absence of grazing, and particularly of the physical environment on the magnitude and duration of A. ostenfeldii blooms. Our results suggest that predicted changes in the physical environment may enhance bloom development in future coastal waters and embayments.     

Roles of mixotrophy in blooms of different dinoflagellates: Implications from the growth experiment

Studies over the last two decades suggested that mixotrophy could be an important adaptive strategy for some bloom-forming dinoflagellates. In the coastal waters adjacent to the Changjiang River estuary in the East China Sea, recurrent blooms of dinoflagellates Prorocentrum donghaiense, Karenia mikimotoi and Alexandrium catenella started to appear from the beginning of the 21 century, but roles of mixotrophy in the formation of dinoflagellate blooms were not well understood. In the current study, mixotrophy-based growth of four selected bloom-causative dinoflagellate species, i.e. K. mikimotoi, A. catenella, P. donghaiense and Prorocentrum micans, were studied. Dinoflagellates were co-cultured with different prey organisms, including bacterium Marinobacter sp., microalgae Isochrysis galbana and Hemiselmis virescens, under a variant of nutrient conditions. It was found that growth of dinoflagellate K. mikimotoi was significantly promoted with the presence of prey organisms. Growth of P. donghaiense and P. micans was only slightly improved. For A. catenella, the addition of prey organisms has no effects on the growth, while both of the two prey microalgae I. galbana and H. virescens were killed, probably by allelochemicals released from A. catenella. There was no apparent relationship between nutrient conditions and the mixotrophy-based growth of the tested dinoflagellates. Based on the results of the growth experiment, it is implicated that mixotrophy may play different roles in the growth and bloom of the four dinoflagellate species. It can be an important competitive strategy for K. mikimotoi. For the two Prorocentrum species and A. catenella, however, the role of mixotrophy is much limited. They may depend more on other competitive strategies, such as phototrophy-based growth and allelopathic effect, to prevail in the phytoplankton community and form blooms.     

An extensive Cochlodinium bloom along the western coast of Palawan, Philippines

A massive fish kill and water discoloration were reported off the western coast of Puerto Princesa, Palawan, Philippines in March 2005. Phytoplankton analysis revealed a near monospecific bloom of the dinoflagellate, Cochlodinium polykrikoides, with cell concentrations ranging from 2.5 × 10⁵ to 3.2 × 10⁶ cells per liter. Ground truth data were supplemented by processed satellite images from MODIS Aqua Level 2 data (1 km resolution) from January to April 2005, which revealed high surface chlorophyll-a levels (up to 50 mg/m³) offshore of west and southwest Palawan as early as February 2005. The bloom extended 310 km in length and 80 km in width at its peak in March off the central coast (Puerto Princesa). By April, the bloom declined in intensity, but was still apparent along the northern coast (El Nido). Fluctuations in chlorophyll levels off the western coast of Sabah, Malaysia and Brunei during this time period suggested that the bloom was not limited to the coast of Palawan. Satellite imagery from Sabah in late January revealed a plume of chl-a that is believed to be the source of the C. polykrikoides bloom in Palawan. This plume drifted offshore, advected northward via the basin-wide counterclockwise gyre, and reached nutrient-rich, upwelled waters near Palawan (due to a positive wind stress curl) where the dinoflagellate bloomed and persisted for 2 months from March to April 2005.     

Temporal and spatial patterns of sea lice levels on sea trout in western Scotland in relation to fish farm production cycles

The relationship between aquaculture and infestations of sea lice on wild sea trout (Salmo trutta) populations is controversial. Although some authors have concluded that there is a link between aquaculture and lice burdens on wild fish, others have questioned this interpretation. Lice levels have been shown to be generally higher on Atlantic salmon farms during the second years of two-year production cycles. Here we investigate whether this pattern relates to lice burdens on wild fish across broad temporal and spatial axes. Within Loch Shieldaig across five successive farm cycles from 2000 to 2009, the percentage of sea trout with lice, and those above a critical level, were significantly higher in the second year of a two-year production cycle. These patterns were mirrored in 2002–2003 across the Scottish west coast. The results suggest a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland.     

Development and application of LSU rRNA probes for Karenia brevis in the Gulf of Mexico, USA

The brevetoxin producing dinoflagellate, Karenia brevis, is the target of several monitoring and research programs in the Gulf of Mexico, where it forms extensive and frequently long-lived annual blooms that can cause human intoxication and fish kills, as well as severe economic losses to coastal communities. Rapid, reliable methods for the detection and enumeration of K. brevis cells, as well as their discrimination from morphologically similar species, are valuable tools for managers and scientists alike. Our aim was to produce a species-specific molecular probe that would serve as a tool to facilitate the efficient and reliable detection of K. brevis in the Gulf of Mexico. We sequenced a fragment of the large-subunit ribosomal RNA gene (LSU rDNA) from five K. brevis cultures isolated from the Texas Gulf coast, the Florida Gulf coast, and the Atlantic coast of Florida, and detected no differences among these isolates. A consensus sequence was thus compiled and compared to a previously published sequence from Karenia mikimotoi, the closest known phylogenetic relative to K. brevis, for the purpose of identifying unique K. brevis signature sequences. Fluorescently-labeled (FITC) oligonucleotide probes targeting these regions of the K. brevis LSU rRNA were designed to include at least two base pair differences, as compared to K. mikimotoi. Among seven probes designed, one uniquely identified all K. brevis isolates to the exclusion of all other species tested (Kbprobe-7), including a Gulf of Mexico K. mikimotoi isolate (Sarasota, FL) and several additional Gymnodinium species, as well as other dinoflagellate, diatom, and raphidophyte taxa. Importantly, K. brevis cells in samples taken during a 2001 bloom, fixed with a mixture of modified saline ethanol and 10% formalin, and stored at 4 °C for 7 months were successfully labeled with Kbprobe-7. In addition, preliminary analysis of labeled cells by flow cytometry revealed that K. brevis could be distinguished from K. mikimotoi in solution, suggesting other potential applications of this probe.