Many species of algae are beneficial to lakes and oceans, providing the basis of the food chain that supports the entire ecosystem. However, when they bloom in significant numbers and produce biotoxins, these events are termed harmful algal blooms (HABs). We are seeing an increase in the number of HABs, toxic algae species, new algal toxins being identified and huge economic losses from HABs than ever before. HABs and their problems can only be of increasing concern for the future. It is therefore paramount that we have early warning methods in place capable of detecting toxic algal blooms. The overall aim of this research was to develop rapid, cost effective, high throughput and multi biotoxin methods for the early warning of toxic algal blooms for the enhancement of seafood, water safety practices and public health. Two biosensor assays were developed; one laboratory based and one potentially portable. The multiplex surface plasmon resonance (SPR) biosensor assay was developed for the semi-quantitative, simultaneous screening of three key marine regulated biotoxins. The performance of this biosensor was characterised by the analysis of seawater samples (n = 256) giving a full biotoxin distribution and toxin composition within European waters. This biosensor was also utilised for monitoring an extensive bloom of the PSP toxin producing Alexandrium minutum during the summer of 2011 in Cork (Ireland). Additionally, the multiplex MBio planar waveguide biosensor assay was developed for the semi-quantitative, simultaneous and potentially portable screening of five types of harmful algal biotoxins with results available in as little as 15 min. Both methods are rapid, easy to use and highly sensitive. They are a major advancement in the field of biotoxin detection and have the capability of being employed as early warning detection systems across a range of aquatic environments for the detection of toxic algal blooms.

The presence of harmful algal blooms (HABs) can result in the accumulation of phycotoxins in shellfish such as mussels, scallops and oysters. Depending on the toxins present, consumption of contaminated shellfish can lead to illness in humans including amnesic, diarrheic or paralytic shellfish poisoning (ASP, DSP or PSP respectively). There is currently a lack of suitable rapid screening tools to complement accepted reference methods for the detection of marine biotoxins. The aims of the thesis were to develop a range of simple and accurate lateral flow immunoassays (LFIA) for the rapid screening of phycotoxins from shellfish extracts, which could be performed either in a laboratory or in the field. As a result, three novel single-step LFIAs were developed and validated for the major regulated toxins responsible for ASP, DSP and PSP, respectively. One of the challenges was to ensure that the thresholds for test~ were based at concentrations relevant to regulations, whilst minimizing the risks of generating positive results from samples deemed compliant to regulations. Qualitative results (negative/positive) were generated using a portable reader to remove subjectivity from results interpretation. Rapid and simple procedures were devised whereby samples could be reliably screened in parallel for key toxins (DA, OA, DTX1, DTX2, STX, NEO, GTX1&4, GTX2&3, dcSTX, dcNEO, dcGTX2&3, C1&C2, GTX5) in 20 min, including sample extractions. To include detection of DTX3 esters, a hydrolysis procedure could be incorporated into the procedure. Validations consisted of evaluating performance characteristics such as accuracy, sensitivity, cross reactivity, stability and robustness/ruggedness. Intra- and inter- laboratory evaluations demonstrated that key toxins could be accurately detected from a variety of shellfish samples (spiked and naturally contaminated) and included comparisons with reference methods.

Seasonal phytoplankton blooms characterize the pelagic communities in temperate oceans and in coastal regions of the Mediterranean Sea. The present study was aimed at understanding the role of trophic interactions in the dynamics ofphytoplankton blooms in a long-term time series in the inner Gulf of Naples (LTER-MC) where phytoplankton and mesozooplankton are dominated by diatoms and copepods, respectively. The abundant calanoids Acartia clausi, Centropages typicus, Paracalanus parvus, and Temora styli/era peak in different seasons and interact with different co-occurring phytoplankton communities, of which the diatoms Chaetoceros socialis, Leptocylindrus spp. and Pseudonitzschia spp. are the most abundant. By following a species-specific approach, the feeding performances and behaviour of the four copepod species on selected bloom-forming diatoms were analyzed by incubation experiments using the food removal method and video recordings of individuals at small scale. Significant differences appeared in the feeding responses of the copepods to the different diatom species, which can be attributed to the species-specific traits of both the predator and prey. Copepods showed behavioral plasticity in presence of different diets, with changes in the duration of feeding bouts and proportion of time allotted to different behaviors, which can in turn affect the feeding rates. Finally, the estimated impact of copepod grazing at st. LTER-MC showed that the copepods can remove a significant portion ofthe bloom-forming diatoms but have a limited impact on total standing stock of a diversified diatom assemblage. The impact also varies depending on the phases of the blooms with respect to the abl;lndance and composition of the plankton communities. This study discloses the role of key copepod species in the dynamics ofphytoplankton blooms for a better understanding of the seasonal and long-term patterns of plankton communities in marine coastal ecosystems.

Every year, the oceans absorb one quarter of the carbon dioxide (CO2) emitted to the atmosphere by human activities. This CO2 sink is part of a very active, natural carbon cycle, through which phytoplankton fix CO2 into organic matter in the surface layer of the ocean. Phytoplankton cells tend to aggregate and sink from this surface layer, exporting carbon to the deep ocean and regulating the atmospheric CO2 on long time scales. In the light of the recent unequivocal evidence of global warming, it appears essential to assess its impact on phytoplankton community and to evaluate the subsequent feedback through the oceanic carbon cycle. In recent years, phytoplankton phenology has been suggested as a systematic indicator to monitor the state of the pelagic ecosystem and detect changes triggered by perturbation of environmental conditions. For the first time, the phenology of phytoplankton growing season is estimated at the global scale using remote-sensing ocean colour data. The tropics and subtropics present generally long growing season (15-20 weeks) of low amplitude (< 0.5 mg m−3), whereas the high-latitudes show short growing season (< 10 weeks) of high amplitude (up to 7 mg m−3). Correlation analyses suggest a close coupling between the development of the growing season and the seasonal increase in insolation in the North Atlantic and Southern Ocean. In the tropics and subtropics, light is rarely limiting and the growing season is controlled by nutrient supply enhanced by water mixing. Over the decade 1998-2008, the duration of growing season shows large interannual variability of up to ± 10 weeks. Globally, positive anomalies follow the major 1997-98 El Ni˜no-La Ni˜na events and persist until 2001. Positive phases of climate indices such as the North Atlantic Oscillation and the Southern Annular Mode, associated with enhanced water mixing and nutrients supply, generally sustain longer growing season. Using in-situ observations, we show that the export of carbon can be related to the length of the phytoplankton growing season, with largest export in regions where the growing season is shortest and the blooms most intense. Using satellite observations, from the sensors CZCS and SeaWiFS, we estimate that North of 45◦S, the phytoplankton growing season increased by 2.4 weeks on average between the periods 1979-1986 and 1998-2008. Longer growing seasons are associated with regional patterns of surface warming on the same time scale. We infer from in-situ data a decrease in carbon export of 0.6 Pg C yr−1 (excluding the Southern Ocean) over two decades. This represents an unexpected, and important, feedback between physical and biological processes in the ocean: global warming modifies phytoplankton growth, reducing the capacity of the ocean to absorb atmospheric CO2 leading to a probable aggravation of global warming. Finally, phenological characteristics of the phytoplankton growing season are used to resolve Sverdrup’s critical depth model. Mixed layer integrated plankton community respiration Rmld and net community production NCPmld are estimated at the global scale using remote-sensing data of incident irradiance level and primary production, and a global mixed layer depth climatology. NCPmld estimates agree with in-situ observations and model results in the tropical and North Atlantic regions. The model estimates a net autotrophic imbalance of + 0.65 Pg C yr−1 in the North Atlantic and a net heterotrophic imbalance of − 1 Pg C yr−1 for the whole tropics and subtropics.

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This study investigated the ecology of subtidal epipelic diatoms in a sea-water loch. A methodology for the sampling and measurement of subtidal epipelic algae was established. The spatial heterogeneity and seasonal distribution of epipelon was investigated and related to physicochemical (salinity, temperature, light) and biological parameters (grazing and disturbance). The relationships between the epipelon and invertebrates were examined by survey and field experiments. The epipelic flora of Loch Goil consisted almost entirely of diatoms (163 spp, 39 genera) and was characterised by a few numerically dominant species (<i>Navicula</i> cf. <i>tripunctata, Navicula</i><i>sp. H, Navicular forcipata</i> var. <i>densistriata; Amphora proteus</i>). The proportion of these species remained relatively constant with depth and season. The abundance of epipelic diatoms was found to be related to microtopography with relatively high densities concentrated on thesides and bases of sedimentary mounds formed by the polychaetes <i>Arenicola marina</i> and <i>Eupolymnia nebulosa</i>. Analysis of the pattern using a 'paired-Quadrat Variance' method showed clumping at intervals of 4cm, 2m and 3m. The bathymetric (6-40m) distribution of epipelic diatoms was investigated and found to be divided into shallow (6m, 12m, 15m) and deep (20m and 30m) water zones, with differences in the density of algae and composition of the rarer species along the depth gradient. The seasonal variability of the epipelon was determined from 1988 to 1990 at 9m and 11m depth. Maximum epipelic growth was recorded from May to September followed by an over-winter period (October to April) of minimum growth. The seasonal distribution of epipelic abundance and chlorophyll-a was found to be correlated with annual cycles of water temperature, irradiance and water clarity.

Plants have developed enzymatic and nonenzymatic antioxidant mechanisms to prevent oxidation of cellular compartments. Enhancing these mechanisms might help plants cope with encountered stresses. Greenhouse and field studies were conducted to examine the influence of seaweed (Ascophyllum nodosum) extract on antioxidant enzymes activities, forage Growth, and persistence of tall fescue (Festuca arundinacea Schreb.). Furthermore. effects of soil moisture, plant genotype, and infection with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon and Hanlin) were investigated. In a greenhouse experiment, seaweed extract was applied to ‘Martin’ tall fescue at 0, 2, 4, 6, 8, and 10 kg ha in a randomized block design with four replicates. Seaweed extract linearly increased ( P 0.05) glutathione reductase activity. Superoxide dismutase and ascorbate peroxidase were also increased but responses differed by time and treatment rates. In a second greenhouse experiment, seaweed extract was applied at 4 kg ha to endophyte-infected and non-infected ‘Georgia Jessup’ and ‘KY-31’ tall fescue grown with 50-100% and 30-100% field capacity soil moisture in a completely randomized design with four replications. Glutathione reductase activity increased (P 0.05) in both genotypes in response to seaweed extract and moisture stress and tended to increase ( P 0.07) in response to the endophyte. Seaweed extract increased (P 0.05) superoxide.

In this study phytoplankton viruses were investigated from a point of view of their genotypic richness, ecology and role in controlling two microalgae species: Emiliania huxleyi and Phaeocystis pouchetii. Host specificity determined for Emiliania huxleyi-virus (EhV) isolates revealed a highly variable host range suggesting a relation between virus specificity and genetic or phenotypic variations within E. huxleyi strains and EhVs. Subsequently the dynamics and genetic richness of Emiliania huxleyi and EhVs were monitored in mesocosm experiments and during the progression of a natural bloom in the sea. The results confirmed the role of virus infection in regulating the intraspecific succession of E. huxleyi in the ocean. Furthermore, they revealed significant differences in genotypic composition and dynamics among blooms. The mesocosm setup appeared to be a very robust experimental system, which allowed reproducibility. The most important factor determining the development of the blooms in the enclosures was the experimental manipulation (i.e. nutrient addition), whereas the effect of filling of the enclosures, delay in nutrient addition and position in the raft were of minor importance. Further laboratory experiments revealed differences in the genomic content of different EhVs. EhV isolates from the English Channel carry a putative phosphate permease gene (ehv117) while the only available EhV from a Norwegian fjord has replaced ehv117 with a putative endonuclease, suggesting different propagation strategies among closely related EhVs. Culture studies using one of the English Channel isolates and E. huxleyi CCMP 1516 showed that the lack of phosphate (P) reduced the growth rate of the host and inhibited the production of viral particles. Furthermore, P availability was shown to have an effect on the level of ehv117 expression. In addition, other mesocosm studies revealed that specific viruses (PpVs) play a significant role in the termination of induced Phaeocystis pouchetii blooms. However, the role of PpVs may be significant only for the flagellated stage of P. pouchetii. Phenotypic characteristics of PpVs isolated during these studies indicate that they are probably members of the Phycodnaviridae family.

No description available.

No description available.