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Using algal-derived mycosporine-like amino acids (MAAs) in sunscreen formulations is constrained by low cellular concentrations of MAAs and by the high costs associated with harvesting algal cells and extracting the MAAs. Here, we report an industrial scalable method using a membrane filtration approach to purify and concentrate aqueous extracts of MAAs. The method includes an additional biorefinery step enabling purification of phycocyanin, an established valuable natural product. Cultivated cells of the cyanobacterium Chlorogloeopsis fritschii (PCC 6912) were concentrated and homogenised to produce a feed for sequential processing through three membranes of decreasing pore size to obtain a retentate and permeate for each step. Microfiltration (0.2 µm) was used to remove cell debris. Ultrafiltration (10,000 Da) was used to remove large molecules and recover phycocyanin. Finally, nanofiltration (300–400 Da) was used to remove water and other small molecules. Permeate and retentate were analysed using UV-visible spectrophotometry and HPLC. The initial homogenised feed had a shinorine concentration of 5.6 ± 07 mg L−1. The final nanofiltered retentate resulted in a 3.3 times-purified concentrate (shinorine concentration of 18.71 ± 0.29 mg L−1). Significant process losses (35%) highlight scope for improvement. Results confirm the potential of membrane filtration to purify and concentrate aqueous solutions of MAAs with simultaneous separation of phycocyanin highlighting a biorefinery approach.

Digestate produced from the anaerobic digestion of food and farm waste is primarily returned to land as a biofertiliser for crops, with its potential to generate value through alternative processing methods at present under explored. In this work, valorisation of a digestate resulting from the treatment of kitchen and food waste was investigated, using dilution, settlement and membrane processing technology. Processed digestate was subsequently tested as a nutrient source for the cultivation of Chlorella vulgaris, up to pilot-scale (800L). Dilution of digestate down to 2.5% increased settlement rate and induced release of valuable compounds for fertiliser usage such as nitrogen and phosphorus. Settlement, as a partial processing of digestate offered a physical separation of liquid and solid fractions at a low cost. Membrane filtration demonstrated efficient segregation of nutrients, with micro-filtration recovering 92.38% of phosphorus and the combination of micro-filtration, ultra-filtration, and nano-filtration recovering a total of 94.35% of nitrogen from digestate. Nano-filtered and micro-filtered digestates at low concentrations were suitable substrates to support growth of Chlorella vulgaris. At pilot-scale, the microalgae grew successfully for 28 days with a maximum growth rate of 0.62 day−1 and dry weight of 0.86 g⋅L−1. Decline in culture growth beyond 28 days was presumably linked to ammonium and heavy metal accumulation in the cultivation medium. Processed digestate provided a suitable nutrient source for successful microalgal cultivation at pilot-scale, evidencing potential to convert excess nutrients into biomass, generating value from excess digestate and providing additional markets to the anaerobic digestion sector.

The “UV sunscreen” compounds, the mycosporine-like amino acids (MAAs) are widely reported in cyanobacteria and are known to be induced under ultra-violet (UV) light. However, the impact of far red (FR) light on MAA biosynthesis has not been studied. We report results from two experiments measuring transcriptional regulation of MAA and aromatic amino acid pathways in the filamentous cyanobacterium Chlorogloeopsis fritschii PCC 6912. The first experiment, comparing UV with white light, shows the expected upregulation of the characteristic MAA mys gene cluster. The second experiment, comparing FR with white light, shows that three genes of the four mys gene cluster encoding up to mycosporine-glycine are also upregulated under FR light. This is a new discovery. We observed corresponding increases in MAAs under FR light using HPLC analysis. The tryptophan pathway was upregulated under UV, with no change under FR. The tyrosine and phenylalanine pathways were unaltered under both conditions. However, nitrate ABC transporter genes were upregulated under UV and FR light indicating increased nitrogen requirement under both light conditions. The discovery that MAAs are upregulated under FR light supports MAAs playing a role in photon dissipation and thermoregulation with a possible role in contributing to Earth surface temperature regulation.

Grazer-induced colony formation as a defense strategy in microalgae such as Scenedesmus species has been widely reported, but the associated costs and reversibility of the colonies are rarely studied. We experimentally showed that Scenedesmus obliquus formed chained colonies in the presence of a predator, including predators separated from the algae by a membrane, but quickly reverted to single cells after the removal of the predator—a defining characteristic of an inducible defense. We detected stress indicators—astaxanthin esters—in the algal populations in the presence of grazers but not when grazers were absent. We found significant costs associated with S. obliquus colony formation in terms of lower population growth rate, lower photosystem II efficiency and lower cellular chlorophyll a content. These results together show that colony formation as an inducible defense in S. obliquus against grazers comes at a substantial cost such that the defense must be switched off and the colonies revert to single cells when the predation risk disappears.

Ultraviolet A (UV-A) is the major component of UV radiation reaching the Earth’s surface, causing indirect damage to photosynthetic organisms via the production of reactive oxygen species (ROS). In comparison, UV-B causes both direct damage to biomolecules and indirect damage. UV-B is well studied in cyanobacterial research due to their long evolutionary history and adaptation to high levels of UV, with less work on the effects of UV-A. In this study, the response of key metabolites in Chlorogloeopsis fritschii (C. fritschii) during 48 h of photosynthetically active radiation (PAR, 15 µmol·m−2·s−1) supplemented with UV-A (11 µmol·m−2·s−1) was investigated using gas chromatography- mass spectrometry (GC-MS). Results showed an overall significant increase in metabolite levels up to 24 h of UV-A exposure. Compared with previously reported UV-B (PAR + UV-B) and PAR only results, UV-A showed more similarity compared to PAR only exposure as opposed to supplemented UV-B. The amino acids glutamate, phenylalanine and leucine showed differences in levels between UV (both supplemented UV-A and supplemented UV-B) and PAR only (non-supplemented PAR), hinting to their relevance in UV stress response. The fatty acids, palmitic and stearic acid, showed positive log2 fold-change (FC) in supplemented UV-A and PAR only experiments but negative log2 FC in UV-B, indicating the more harmful effect of UV-B on primary metabolism. Less research has been conducted on UV-A exposure and cyanobacteria, a potential environmental stimuli for the optimisation of metabolites for industrial biotechnology. This study will add to the literature and knowledge on UV-A stress response at the metabolite level in cyanobacteria, especially within the less well-known species C. fritschii.

For the growing human population to be sustained during present climatic changes, enhanced quality and quantity of crops are essential to enable food security worldwide. The current consensus is that we need to make a transition from a petroleum-based to a bio-based economy via the development of a sustainable circular economy and biorefinery approaches. Both macroalgae (seaweeds) and microalgae have been long considered a rich source of plant biostimulants with an attractive business opportunity in agronomy and agro-industries. To date, macroalgae biostimulants have been well explored. In contrast, microalgal biostimulants whilst known to have positive effects on development, growth and yields of crops, their commercial implementation is constrained by lack of research and cost of production. The present review highlights the current knowledge on potential biostimulatory compounds, key sources and their quantitative information from algae. Specifically, we provide an overview on the prospects of microalgal biostimulants to advance crop production and quality. Key aspects such as specific biostimulant effects caused by extracts of microalgae, feasibility and potential of co-cultures and later co-application with other biostimulants/biofertilizers are highlighted. An overview of the current knowledge, recent advances and achievements on extraction techniques, application type, application timing, current market and regulatory aspects are also discussed. Moreover, aspects involved in circular economy and biorefinery approaches are also covered, such as: integration of waste resources and implementation of high-throughput phenotyping and -omics tools in isolating novel strains, exploring synergistic interactions and illustrating the underlying mode of microalgal biostimulant action. Overall, this review highlights the current and future potential of microalgal biostimulants, algal biochemical components behind these traits and finally bottlenecks and prospects involved in the successful commercialisation of microalgal biostimulants for sustainable agricultural practices.

Carotenoids in cyanobacteria play an important role in protecting against and in repairing damage against low level UV-B radiation. Here we use transcriptomics and metabolomic HPLC pigment analysis to compare carotenoid pathway regulation in the filamentous cyanobacterium Chlorogloeopsis fritschii PCC 6912 exposed to white light and to white light supplemented with low level UV-B. Under UV-B changes in carotenoid transcription regulation were found associated with carotenogenesis (carotenoid synthesis), photoprotection and carotenoid cleavage. Transcriptional regulation was reflected in corresponding pigment signatures. All carotenogenesis pathway genes from geranylgeranyl-diphosphate to lycopene were upregulated. There were significant increases in expression of gene homologs (crtW, crtR, cruF, and cruG) associated with routes to ketolation to produce significant increases in echinenone and canthaxanthin concentrations. There were gene homologs for four β-carotene-ketolases (crtO and crtW) present but only one crtW was upregulated. Putative genes encoding enzymes (CruF, CrtR, and CruG) for the conversion of γ-carotene to myxol 2'-methylpentoside were upregulated. The hydroxylation pathway to nostaxanthin via zeaxanthin and caloxanthin (gene homologs for CrtR and CrtG) were not upregulated, reflected in the unchanged corresponding pigment concentrations in zeaxanthin, caloxanthin and nostaxanthin, Transcripts for the non-photochemical quenching related Orange-Carotenoid-Protein (OCP) and associated Fluoresence-Recovery-Protein (FRP) associated with photoprotection were upregulated, and one carotenoid binding Helical-Carotenoid-Protein (HCP) gene homolog was downregulated. Multiple copies of genes encoding putative apocarotenoid related carotenoid oxygenases responsible for carotenoid cleavage were identified, including an upregulated apo-β-carotenal-oxygenase gene homologous to a retinal producing enzyme. Our study provides holistic insight into the photoregulatory processes that modulate the synthesis, photoprotection and cleavage of carotenoids in cyanobacterial cells exposed to low level UV-B. This is important to understanding how regulation of metabolism responds to a changing environment and how metabolism can be modulated for biotechnological purposes.

A two-phase outdoor cultivation bioprocess for Arthrospira maxima LJGR1 combined with phycocyanin induction in concentrated cultures under controlled conditions was evaluated using a modified low-cost Zarrouk medium. Growth was monitored during 4 cycles in 2018 and 4 cycles in 2019. Biomass was harvested and concentrated using membrane technology at the end of each cycle for further phycocyanin induction using blue LED light (controlled conditions, 24 h). The highest biomass productivity was observed during spring and summer cycles (13.63–18.97 gDWm−2 d−1); during mid-fall and mid-end fall, a decrease was observed (9.93–7.76 gDWm−2 d−1). Under favorable growth conditions, phycocyanin induction was successful. However, during cycles with unfavorable growth condition, phycocyanin induction was not observed. Reactive-grade phycocyanin (3.72 ± 0.14) was recovered and purified using microfiltration and ultrafiltration technologies.

Microalgae are the foundation of aquatic food webs. Their ability to defend against grazers is paramount to their survival, and modulates their ecological functions. Here, we report a novel anti-grazer strategy in the common green algaChlorella vulgarisagainst two grazers,Daphnia magnaandSimocephalussp. The algal cells entered the brood chamber of both grazers, presumably using the brood current generated by the grazer's abdominal appendages. Once inside, the alga densely colonized the eggs, significantly reducing reproductive success. The effect was apparent under continuous light or higher light intensity. The algal cells remained viable following removal from the brood chamber, continuing to grow when inoculated in fresh medium. No brood chamber colonization was found when the grazers were fed the reference dietRaphidocelis subcapitataunder the same experimental conditions, despite the fact that both algal species were readily ingested by the grazers and were small enough to enter their brood chambers. These observations suggest thatC. vulgariscan directly inflict harm on the grazers' reproductive structure. There is no known prior example of brood chamber colonization by a microalgal prey; our results point to a new type of grazer–algae interaction in the plankton that fundamentally differs from other antagonistic ecological interactions.

Planctomycetes are ubiquitous and environmentally important Gram-negative aquatic bacteria with key roles in global carbon and nitrogen cycles. Many planctomycetal species have a pink or orange colour and have been suggested to produce carotenoids. Potential applications as food colorants or anti-oxidants have been proposed. Hitherto, the planctomycetal metabolism is largely unexplored and the strain pigmentation has not been explored. For a holistic view of the complex planctomycetal physiology, we analysed carotenoid profiles of the pink-pigmented strain Rhodopirellula rubra LF2

Several factors have the potential to influence microalgae growth. In the present study, nitrogen concentration and light intensity were evaluated in order to obtain high biomass production and high phycoerythrin accumulation from Porphyridium purpureum. The range of nitrogen concentrations evaluated in the culture medium was 0.075&ndash, 0.450 g L&minus, 1 and light intensities ranged between 30 and 100 &mu, mol m&minus, 2 s&minus, 1. Surprisingly, low nitrogen concentration and high light intensity resulted in high biomass yield and phycoerythrin accumulation. Thus, the best biomass productivity (0.386 g L&minus, 1 d&minus, 1) and biomass yield (5.403 g L&minus, 1) were achieved with NaNO3 at 0.075 g L&minus, 1 and 100 &mu, 1. In addition, phycoerythrin production was improved to obtain a concentration of 14.66 mg L&minus, 1 (2.71 mg g&minus, 1 of phycoerythrin over dry weight). The results of the present study indicate that it is possible to significantly improve biomass and pigment production in Porphyridium purpureum by limiting nitrogen concentration and light intensity.

This chapter focuses on the challenges associated with achieving economic value from metabolites derived from cyanobacteria. Significant advances have been made in cyanobacterial biotechnology in the last few years. However, the field is still immature, and many challenges remain. We start with a critical overview of the main technologies associated with cultivation, cell disruption and metabolite extraction. Then, we provide an overview of current significant metabolite groups from cyanobacteria relevant to industry covering phycobilins, carotenoids, polysaccharides, peptides, lipids, mycosporine-like amino acids, polyhydroxyalkanoates, cyanotoxins and platform chemicals, and the potential for stable isotopes production. We cover metabolites that are already in the market and those with future potential with a focus on spirulina (Arthrospira) the most commercially developed species of cyanobacteria. As large-scale cultivation and down-stream processing techniques continue to develop further, combining this with a systems biology and biorefinery approach will ensure that the best economic and environmental sustainability value can be achieved.

Advances in science and technology have revealed a far greater complexity in the marine world than previously thought with the discovery of many new species of microbial life living in habitats believed to be unsuitable for survival. This has led to the discovery of many new biochemical processes producing novel chemicals and proteins with potential applications in a wide range of fields. An overview is provided of how marine science, with a particular emphasis on microscopic organisms, is being applied to diverse areas such as health and well being, the environment, energy, and chemistry. Specific examples, where appropriate, are given of how marine organisms and their chemical products are being applied in industry and medicine.

Planctomycetes are ubiquitous and environmentally important Gram‐negative aquatic bacteria with key roles in global carbon and nitrogen cycles. Many planctomycetal species have a pink or orange colour and have been suggested to produce carotenoids. Potential applications as food colorants or anti‐oxidants have been proposed. Hitherto, the planctomycetal metabolism is largely unexplored and the strain pigmentation has not been explored. For a holistic view of the complex planctomycetal physiology, we analysed carotenoid profiles of the pink‐pigmented strain Rhodopirellula rubra LF2T and of the orange strain Rubinisphaera brasiliensis Gr7. During LC–MS/MS analysis of culture extracts, we could identify three saproxanthin‐type carotenoids including a rare C45 carotenoid. These compounds, saproxanthin, dehydroflexixanthin and 2′‐isopentenyldehydrosaproxanthin, derive from the common carotenoid precursor lycopene and are characterized by related end groups, namely a 3‐hydroxylated β‐carotene‐like cyclohexene ring as one end group and simple hydration on the other end of the molecule. Based on the observed molecule structure we present putative pathways for their biosynthesis. Results support Planctomycetes as a promising, yet mostly untapped source of carotenoids. This research was partially supported by the Strategic Funding UID/Multi/04423/2019 through national funds pro- vided by FCT - Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programme PT2020 and by the German Research Foundation (DFG), Grant KA 4967/1-1, Project Number 405562673.

There is increasing interest in the use of microalgae grown on wastewater to provide useful metabolites. Several bacteria have been shown to affect the growth rate and quality of the algae, but it is not clear if this is specific to a particular group of bacteria or if nutrient conditions can also influence this interaction. The bacterial community associated with a freshwater Chlorella sp. isolated from open pond textile factory wastewater was characterised and a diverse group of bacteria isolated. We provide evidence that nutrient concentrations affect bacterial community composition. When grown in BG11 medium, the community was dominated by Pseudomonas sp., but when grown in Chu 10 medium (which contains lower nitrogen and phosphorus), the relative abundance of a Brevundimonas spp. increased. Several of the bacteria isolated were able to influence the growth of an axenic Chlorella vulgaris culture. The Pseudomonas sp. had a negative effect in all media tested whereas several isolates enhanced C. vulgaris growth, but only in Chu 10 medium. This supports the theory that bacterial stimulation of algal growth is not limited to species-specific interactions but is influenced by environmental conditions. In low nutrient conditions, Chlorella sp. may be increasingly dependent on bacteria for growth.

Managing organic waste streams is a major challenge for the agricultural industry. Anaerobic digestion (AD) of organic wastes is a preferred option in the waste management hierarchy, as this process can generate renewable energy, reduce emissions from waste storage, and produce fertiliser material. However, Nitrate Vulnerable Zone legislation and seasonal restrictions can limit the use of digestate on agricultural land. In this paper we demonstrate the potential of cultivating microalgae on digestate as a feedstock, either directly after dilution, or indirectly from effluent remaining after biofertiliser extraction. Resultant microalgal biomass can then be used to produce livestock feed, biofuel or for higher value bio-products. The approach could mitigate for possible regional excesses, and substitute conventional high-impact products with bio-resources, enhancing sustainability within a circular economy. Recycling nutrients from digestate with algal technology is at an early stage. We present and discuss challenges and opportunities associated with developing this new technology.

Phytoplankton total chlorophyll concentration (TCHLa) and phytoplankton size structure are two important ecological indicators in biological oceanography. Using high performance liquid chromatography (HPLC) pigment data, collected from surface waters along the Atlantic Meridional Transect (AMT), we examine temporal changes in TCHLa and phytoplankton size class (PSC: micro-, nano- and pico-phytoplankton) between 2003 and 2010 (September to November cruises only), in three ecological provinces of the Atlantic Ocean. The HPLC data indicate no significant change in TCHLa in northern and equatorial provinces, and an increase in the southern province. These changes were not significantly different to changes in TCHLa derived using satellite ocean-colour data over the same study period. Despite no change in AMT TCHLa in northern and equatorial provinces, significant differences in PSC were observed, related to changes in key diagnostic pigments (fucoxanthin, peridinin, 19′-hexanoyloxyfucoxanthin and zeaxanthin), with an increase in small cells (nano- and pico-phytoplankton) and a decrease in larger cells (micro-phytoplankton). When fitting a three-component model of phytoplankton size structure — designed to quantify the relationship between PSC and TCHLa to each AMT cruise, model parameters varied over the study period. Changes in the relationship between PSC and TCHLa have wide implications in ecology and marine biogeochemistry, and provide key information for the development and use of empirical ocean-colour algorithms. Results illustrate the importance of maintaining a time-series of in-situ observations in remote regions of the ocean, such as that acquired in the AMT programme.

Metabolomics provides an unbiased assessment of a wide range of metabolites and is an emerging ‘omics technique in the marine sciences. We use ‘non-targeted’ community metabolomics to determine patterns in metabolite profiles associated with particulate organic matter (POM) at four locations from two long-term monitoring stations (L4 and E1) in the western English Channel. The polar metabolite fractions were measured using ultra-high performance liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry (UHPLC-FT-ICR-MS), and the lipid fractions by direct infusion Fourier transform ion cyclotron resonance mass spectrometry (DI-FT-ICR-MS); these were then analysed to statistically compare the metabolite distributions. Results show significantly different profiles of metabolites across the four locations with the largest differences for both the polar and lipid fractions found between the two stations relative to the smaller differences associated with depth. We putatively annotate the most discriminant metabolites revealing a range of amino-acid derivatives, diacylglyceryltrimethylhomoserine (DGTS) lipids, oxidised fatty acids (oxylipins), glycosylated compounds, oligohexoses, phospholipids, triacylglycerides (TAGs) and oxidised TAGs. The majority of the polar metabolites were most abundant in the surface waters at L4 and least abundant in the deep waters at E1 (E1-70m). In contrast, the oxidised TAGs were more abundant at E1 and most abundant at E1-70m. The differentiated metabolites are discussed in relation to the health of the phytoplankton as indicated by nutrients, carbon and chlorophyll, and to the dominance (determined from metatranscript data) of the picoeukaryote Ostreococcus. Our results show proof of concept for community metabolomics in discriminating and characterising polar and lipid metabolite patterns associated with marine POM.

Although viruses can significantly reduce primary production-mediated carbon cycling, the effect of viral infection on the principal photosynthetic pigment that enables auto- trophic production, chlorophyll a (chl a), remains unresolved. We compared the production of chl a transformation compounds in Emiliania huxleyi cultures undergoing viral infection with that in control cultures left to decline in the stationary phase of growth. A high performance liquid chromatography mass spectrometry method developed for the detection of Type I chl a transfor- mation products was used. A rapid decline in cellular concentrations of chl a, C-13 2 diastereomer of chl a (chl a') and phaeophytin a (phytin a) was observed in both infected and control cultures. The most notable finding was the significant increase in the cellular concentrations of Type I chl oxidation products (allomers) in the infected cultures, and we hypothesise that this may be due to increased oxidative stress and reactive oxygen species.

The seasonal and intra-annual variation of Pseudo-nitzschia species and domoic acid (DA) concentrations, at a long term monitoring site (L4) in the Western English Channel, is reported over an annual cycle (January to December 2009). To determine what drives Pseudo-nitzschia spp. occurrence and DA production at L4 we relate results to a range of physical and chemical environmental parameters. Pseudo-nitzschia spp. occurred throughout the year ranging from 40 cells L −1 and 250×10 3 cells L −1 with two peaks in abundance occurring in June/July and in August. In August Pseudo-nitzschia spp. accounted for 100% of the total diatom community. Three distinct groups or categories of species were enumerated according to morphology and size; those resembling Pseudo-nitzschia delicatissima cell types, those resembling Pseudo-nitzschia seriata , and those resembling Pseudo-nitzschia pungens/multiseries. The P. delicatissima -group was responsible for the high abundance in August. BEST analysis showed that the three groups were ecologically different with a number of environmental parameters influencing the abundance of the groups. The P. delicatissima -group was significantly influenced by the physical environmental factors of temperature, hours of light, rainfall, as well as phosphate, and salinity, whereas P. pungens/multiseries- group were significantly influenced by macronutrients. The P. seriata -group was significantly influenced by temperature and nitrate. DA was detected over a five week period from May to July with a maximum in June (0.4 ng DA L −1 ). When DA was present the surface waters were limited by silicate and nitrate. DA was significantly correlated with the presence of the P. seriata -group and the P. pungens/multiseries- group ( p

The photoprotective response in the dinoflagellate Glenodinium foliaceum F. Stein exposed to ultraviolet-A (UVA) radiation (320-400 nm; 1.7 W · m(2) ) and the effect of nitrate and phosphate availability on that response have been studied. Parameters measured over a 14 d growth period in control (PAR) and experimental (PAR + UVA) cultures included cellular mycosporine-like amino acids (MAAs), chls, carotenoids, and culture growth rates. Although there were no significant effects of UVA on growth rate, there was significant induction of MAA compounds (28 ± 2 pg · cell(-1) ) and a reduction in chl a (9.6 ± 0.1 pg · cell(-1) ) and fucoxanthin (4.4 ± 0.1 pg · cell(-1) ) compared to the control cultures (3 ± 1 pg · cell(-1) , 13.3 ± 3.2 pg · cell(-1) , and 7.4 ± 0.3 pg · cell(-1) , respectively). In a second investigation, MAA concentrations in UVA-exposed cultures were lower when nitrate was limited (P 0.05) but were higher when phosphate was limiting. Nitrate limitation led to significant decreases (P 0.05) in cellular concentration of chls (chl c1 , chl c2 , and chl a), but other pigments were not affected. Phosphate availability had no effect on final pigment concentrations. Results suggest that nutrient availability significantly affects cellular accumulation of photoprotective compounds in G. foliaceum exposed to UVA.

Efficient and economical large scale bioprocessing of microalgae to produce a range of bio-products, working towards a biorefinery approach, is critical for the success of algal industrial biotechnology. The key process variables that affect the recovery of products from different sub-cellular locations were investigated using a high throughput cell disruption system and a cyanobacterium as model organism. This information was then used to design and test a differential recovery procedure at pilot scale using a custom designed ball mill that consumed 1.87 kWh/kg of dry biomass used approximately 34% lower than the best algal disruption system reported. The balance between the number of collisions and force of each collision between grinding media and the microorganism were manipulated to achieve differential recovery. Greater than 99 and 95% solids were recovered at the end of first and second ball milling step respectively through gravity sedimentation, an energy efficient solid-liquid separation technique. Based on these results and the release rates of intracellular and/or extracellular products tested, a theoretical framework is presented for the design of a differential recovery process using ball mills.

A numerical model describing xanthophyll dynamics in phytoplankton has been developed and used to investigate cellular photoprotective response. The model assumes that, under the transition from limiting to supra-saturating light, the xanthophyll cycling pigments (PX) synthesis implies first (on a time scale of tens of minutes) a stoichiometric conversion of the already existing fucoxanthin (FUCO) and then (on time scales of an hour onwards) an up-regulation of the investment of newly synthesized carbon to PX. The latter is concomitant with a reduction in the new carbon invested in FUCO production, which down-regulates the lightharvesting apparatus. We hypothesize that these dynamics play a major role in those phytoplankton species adapted to live in highly dynamic environments requiring rapid photoprotective response. In fact, under high light-induced stress, the conversion between photosynthetic and photoprotective compounds may be a metabolically efficient photoprotective mechanism not requiring the use of newly assimilated (and then energetically expensive) carbon.

The photoprotective response in the dinoflagellate Glenodinium foliaceum F. Stein exposed to ultraviolet-A (UVA) radiation (320-400 nm; 1.7 W · m(2) ) and the effect of nitrate and phosphate availability on that response have been studied. Parameters measured over a 14 d growth period in control (PAR) and experimental (PAR + UVA) cultures included cellular mycosporine-like amino acids (MAAs), chls, carotenoids, and culture growth rates. Although there were no significant effects of UVA on growth rate, there was significant induction of MAA compounds (28 ± 2 pg · cell(-1) ) and a reduction in chl a (9.6 ± 0.1 pg · cell(-1) ) and fucoxanthin (4.4 ± 0.1 pg · cell(-1) ) compared to the control cultures (3 ± 1 pg · cell(-1) , 13.3 ± 3.2 pg · cell(-1) , and 7.4 ± 0.3 pg · cell(-1) , respectively). In a second investigation, MAA concentrations in UVA-exposed cultures were lower when nitrate was limited (P < 0.05) but were higher when phosphate was limiting. Nitrate limitation led to significant decreases (P < 0.05) in cellular concentration of chls (chl c1 , chl c2 , and chl a), but other pigments were not affected. Phosphate availability had no effect on final pigment concentrations. Results suggest that nutrient availability significantly affects cellular accumulation of photoprotective compounds in G. foliaceum exposed to UVA.

Microalgal culture experiments to track chlorophyll-a (chl-a) transformation during senescence were characterised by the production of demetallated Type I chl-a transformation products in Pavlova gyrans and by the production of oxidative Type I transformation products in Isochrysis galbana. Dark-induced senescence in I. galbana produced a different distribution of Type I products from nutrient depletion induced senescence. Several novel Type I compounds were detected, including a chl-d like compound in I. galbana and a chl-a precursor like compound in P. gyrans. Type II chl-a transformation products were detected in the dissolved phase of I. galbana cultures; this is the first report of such compounds associated with marine algae.

Mycosporine-like amino acids (MAAs), phytoplankton pigments, and inherent optical properties were analyzed in sea surface microlayer (SSM), near-surface (0-2 m), and subsurface (0–110 m) samples from stations off the Iberian Peninsula in June-July 2005. During a visible surface slick, MAA concentrations reached 290 µg L−1 in the SSM, which correlated with an increase in abundance of the dinoflagellate, Prorocentrum micans (> 4000 cells mL−1) and covaried with low Ekman transport. High levels of colored dissolved organic material (CDOM) were also found in the SSM, and a prominent absorption shoulder between 300 and 340 nm was evident in the CDOM absorption spectra, indicative of MAAs in the dissolved fraction. Low CDOM slope ratios (SCDOM(275-295) : (350-400)) during the development of the surface slick suggest microbial production of CDOM, possibly exuded from the sudden proliferation in P. micans. In the absence of a well-defined SSM, higher SCDOM(275–295) : (350–400) ratios were found, suggesting photobleaching of CDOM at the surface. The particulate absorption spectra of MAAs (aPMAA(λ)) were effective at absorbing ultraviolet (UV) radiation in a narrow spectral band between 310 and 350 nm. Since aCDOM(λ) exhibits an exponential rise in absorption in the UV and was high in the SSM and the subsurface compared with aPMAA (λ), CDOM would be the principal mechanism of UVA and B attenuation in the water column, providing an additional sunscreen to phytoplankton.

Atmospheric pressure chemical ionisation liquid chromatography/multistage mass spectrometry (APCI LC/MS n ) is an ideal tool for the analysis of complex mixtures of natural compounds produced in the aquatic environment. In contrast to extensive reports of open chain (type II) chlorophyll (chl) transformation products (also known as chl catabolites) in terrestrial plants, there have been no reports relating to aquatic equivalents. This study examines the fragmentation pathways of type II chl transformation products from APCI LC/MS n analysis in order to determine whether it is a suitable analytical method for detecting and distinguishing among such compounds if they are present in samples from the aquatic environment. An extract from the medium of a laboratory culture of the alga Chlorella protothecoides was analysed and found to contain a number of structurally similar compounds assigned as being either red chlorophyll catabolites (RCCs) or fluorescent chlorophyll catabolites (FCCs). The five structures examined were found to exhibit one of three distinct fragmentation patterns, a result that highlights the potential of APCI LC/MS n for distinguishing among different type II chl transformation products.

The influences of physico-chemical and biological variables on the concentrations of di- methyl sulphide (DMS) and its precursor β-dimethylsulphoniopropionate (DMSP) were investigated through an annual cycle in the temperate shelf seas of the western English Channel. Total DMSP to chlorophyll a ratios (DMSPt/chl a) varied seasonally by 40-fold, and DMS and DMSP concentrations became temporally uncoupled, with elevated relative DMS concentrations during spring and mid- summer. Taxonomic succession of high DMSP-producing phytoplankton, including Phaeocystis pouchetii, Scrippsiella trochoidea and Prorocentrum minimum, is apparent in the seasonal pattern of DMSPt concentrations. Peridinin and DMSPt concentrations showed similar seasonal trends (p < 0.0001), illustrating the substantial contribution by dinoflagellate taxa to DMSP production. Summer- time stratification of the water column coincided with increased mixed layer doses of photosyntheti- cally active radiation (PAR), increased surface ultraviolet-B (UVB) irradiance relative to PAR and a de- crease in nitrate and phosphate availability. PAR dose explained 68% of the variability in DMSP/chl a during the seasonal study; whilst nitrate concentrations were inversely related to DMSP/chl a and explained 64% of the variability in log-transformed DMSP/chl a. PAR dose explained only 25% of the variation in DMS concentration, whilst nitrate concentration was inversely related to DMS and explained 49% of the variation in log-transformed DMS concentration. The highly significant relation- ship between DMSP/chl a and PAR dose was similar to those observed for the chlorophyll-specific accumulation of the photoprotective xanthophyll compounds diadinoxanthin and diatoxanthin and the chlorophyll-specific concentrations of UV-absorbing mycosporine-like amino acids. These results lend further, indirect evidence for a photoprotective role of DMSP, possibly associated with physiological stress caused by high PAR and UV radiation and intensified by nutrient limitation.

The microbial dynamics during a spring diatom bloom decline was monitored in the Northeast Atlantic during a 5-day Lagrangian study (8-12 April 2002). Phytoplankton abundance, composition and health status were related to viral and bacterial abundance, zooplankton abundance and grazing rates, as well as bacterial production. Phytoplankton reached maximum concentration on Day 3 (Chl a >5 μg L −1 ) and declined on Day 5 (Chl a ∼2 μg L −1 ) and was dominated (70% of Chl a) by diatoms. Bacterial production increased substantially to >20 μg C L −1 day −1 on Day 3 and concomitantly large viruses decreased in number by half to

We report the response of carotenoids and chlorophylls during 120 h time series virus infection experiments of the marine coccolithophorid Emiliania huxleyi (Lohm.) Hay et Mohler culture. The response of individual carotenoids to infection varied: Diatoxanthin (Dtx) increased rapidly relative to chlorophyll-a, whereas diadinoxanthin (Ddx) and β-carotene showed a rapid decrease and fucoxanthin and 19′hexanoyloxyfucoxanthin a slight increase. The response of the individual carotenoids reflects their role in epoxy/de-epoxidation cycling, antioxidant protection, biosynthetic conversion and vulnerability to photooxidative destruction. We observed for the first time the operation of the diadinoxanthin cycle occurring in response to viral infection in E. huxleyi with the de-epoxidation ratio (Dtx / (Dtx + Ddx)) increasing exponentially with time (R2 = 0.92) and decreasing exponentially with FV / FM (R2 = 0.97). Our findings contribute to our understanding of the conversion and fate of key biochemical cell constituents in algae and are important in understanding the physiological stress response to virus infection.

A new tool combining the use of HPLC pigment markers with ecological similarity indices, to provide a fast and effective environmental tool for monitoring water quality, was investigated. HPLC pigment concentrations from a 4-year time series data set (2000-2003) from the western English Channel were used to calculate six similarity indices to assess changes in phytoplankton community structure. Indices obtained from HPLC data were compared with those produced from the corresponding phytoplankton biomass derived from microscopic analysis. Multivariate RELATE analyses (P

The phytoplankton community assemblage in surface water of the English Channel (Station L4) was measured and compared from March 1999 to October 2002 using two different methods. Pigment-CHEMTAX was used to derive class apportioned chlorophyll a (Chl a) and cell counts obtained using microscopy were used to derive phytoplankton carbon (phyto-C) estimations. Phyto-C (10-340 μg C L -1 ) showed a strong linear relationship with total Chl a (0.5-4.8 μg Chl a L -1 ) when the Chl a:phyto-C ratio was >0.04 (r2 = 0.80; average Chl a:phyto-C = 0.044) but the relationship was weaker when the Chl a:phyto-C ratio was

Characterisation of natural phytoplanktonic communities is currently being advanced through flow cytometry and high resolution pigment analyses. To date, toxicological methods to assess impacts of herbicides on natural phytoplankton populations are lacking. Here, we report the novel use of these techniques in combination to study changes in phytoplankton populations exposed to 2-methylthio-4-tertiary-butylamino-6-cyclopropylamino- s -triazine (Irgarol 1051 ® ), a herbicide used in antifouling paints. Flow cytometry results revealed that following a 72-h exposure to approximately 100 ng L −1 , eukaryote abundance was less than half that in the controls. High performance liquid chromatographic analyses of pigments demonstrated that 19 ′ -hexanoyloxyfucoxanthin was selectively lost relative to the control. This carotenoid is specific to the prymnesiophytes which are key constituents of phytoplanktonic communities within temperate marine waters. Values of EC 50 (72 h) as low as 70 ng L −1 were calculated from the selective reduction in this compound. Concentrations substantially exceeding this level have been reported in UK and other European coastal waters.

A seasonal survey was undertaken, over a year, of phytoplankton from surface water in the western English Channel (Station L4) measuring mycosporine-like amino acids (MAAs), photosynthetic pigments and microscopic counts. Ground level solar radiation (ultraviolet-B, ultraviolet-A and photosynthetically active radiation; UV-B, UV-A and PAR) was measured at a nearby site. From this we estimated in situ solar irradiance received by phytoplankton using measurements of the mixed layer depth and calculations of the 50% light level cut-off. The MAAs occurred year round, with concentrations increasing rapidly during spring and summer (maximum 8·5 μg l−1) to levels exceeding those of chlorophyll-a (chl-a maximum 3·6 μg l−1). On two occasions, increases in specific MAAs coincide with algal blooms. In spring, increases in mycosporine-glycine (λmax 310 nm in the UV-B) coincide with a bloom of the prymnesiophyte Phaeocystis pouchetii and in July and August increases in an unidentified MAA (λmax 328 nm) match a bloom of the diatom, Guinardia striata (=Rhizosolenia stolterfothii). Concentration of MAAs, but not chlorophyll, correlate with in situ irradiance. The ratio of MAA to chl-a increases linearily with in situ irradiance received by phytoplankton reaching 13·9 nmol MAA (nmol chl-a)−1 at 101 W m−2. Evidence of photoinduction is observed during the P. pouchetii bloom with a four fold increase in the concentration of mycosporine-glycine (maximum 2 pg cell−1) as UV-B:PAR ratio increases from 0·0011 to 0·0014. Dinoflagellates, although contributing to a values for the English Channel are similar to those measured in coastal areas of southern USA. Similarities with studies on Antarctic phytoplankton are also found with the dominance of porphra-334 and the presence of mycosporine-glycine in P. pouchetti.

The phytoplankton community structure and abundance in the south-eastern Black Sea was measured from February to December 2009 using and comparing high performance liquid chromatography pigment and microscopy analyses. The phytoplankton community was characterized by diatoms, dinoflagellates and coccolithophores, as revealed by both techniques. Fucoxanthin, diadinoxanthin, peridinin and 19′-hexanoyloxyfucoxanthin were the main accessory pigments showing significant correlation with diatom-Cr2 = 0.56–0.71,P r2 = 0.85–0.91,P r2 = 0.39–0.88,P r2 = 0.80–0.71,P adeep maximum. Average phyto-C was higher at the coastal station (291 ± 66 µg l−1) than at the offshore station (258 ± 35 µg l−1), not statistically different (P > 0.05). The coastal station also had higher Chl-aconcentrations (0.52–3.83 µg l−1) compared to the offshore station (0.63–2.55 µg l−1), not significant (P > 0.05). Our results are consistent with other studies and indicate that the southern Black Sea is shifting towards mesotrophy with the increasing prevalence of dinoflagellates compared to diatoms.

A research cruise in the North Atlantic during the annual diatom bloom provided an ideal platform to study chlorophyll-a (chl-a) transformations associated with a large scale diatom bloom and export below the photic zone. On one deployment, Lagrangian sediment traps captured a significant flux of aggregated diatom cells produced during the termination of the main bloom. We examined the distribution of chl-a transformation products in sinking particles from the sediment traps and in suspended particles from the water column using high-resolution HPLC with multistage mass spectrometry (LC–MSn). There was a dramatic change in the distribution of chl-a and its transformation products between the pre-sinking period, when the average chl-a concentration integrated over the upper 50 m was 68 ± 36 mg m− 2, and the post-sinking period, when it was 30 ± 11 mg m− 2. Before the diatom bloom left the euphotic zone (pre-sinking), suspended particles contained a considerably higher percentage of pheophorbide-a and other chl-a transformation products (27%) than during the post-sinking period (10%). Despite high levels of spatial variability in the chl-a concentration, and despite sampling from both within and outside a main bloom patch, the chl-a transformation products in suspended particles did not exhibit spatial variability. Sinking particles associated with the diatom bloom export had low POC:chl-a ratios (52–97), suggesting undegraded phytoplankton cells. However, the samples with especially low POC:chl-a ratios exhibited similar distributions of chl-a transformation products to those with a higher ratio. The proportions of demetalated and de-esterified transformation products increased with depth of suspended particles, although significant levels of these products were also found in the uppermost 20 m during the bloom. This suggests processes in both surface waters and through the water column led to the formation of these products.

Phytoplankton and microzooplankton community structure and the impact of microzooplankton grazing were investigated during a one-day study of an Emiliania huxleyi bloom off the coast of Devon during July 1999. Vertical profiles were undertaken at four stations, along a transect which crossed from a low reflectance to a high reflectance area as seen by satellite imagery. Microzooplankton dilution grazing experiments, coupled with pigment analysis to determine class specific grazing rates, were performed at two of these stations.Highest concentrations of chlorophyll-a (5·3 mg m−3) and accessory pigments were measured inside the area of high reflectance. Phytoplankton standing stocks ranged between 1588 and 5460 mg C m−2 and were also highest in the area of high reflectance. The phytoplankton community was dominated by coccolithophores and diatoms in low reflectance waters and by photosynthetic dinoflagellates in high reflectance areas. Microzooplankton standing stocks ranged between 905 and 2498 mg C m−2. Protozoa dominated the microzooplankton community. The protozoan community comprised a relatively even mixture of heterotrophic dinoflagellates, non-choreotrich and choreotrich ciliates in low reflectance waters. However, non-choreotrich ciliates dominated the communities inside the high reflectance area. Of the heterotrophic ciliates, a predatory ciliate Askenasia sp. dominated both non-choreotrich abundance and biomass.Results from grazing experiments showed that 60–64% of the chlorophyll-a biomass was consumed daily by the microzooplankton. Highest grazing mortality was associated with peridinin (dinoflagellates) and alloxanthin (cryptophytes). Lower grazing rates were found on fucoxanthin (diatoms and prymnesiophytes). Our results indicate that grazing on E. huxleyi in the area of remotely sensed high reflectance was low and highest grazing was on photosynthetic dinoflagellates and cryptophytes.

Optical profiles taken aboard the Belgica 98/15 cruise during the Iberian upwelling season were applied to five empirical and two semi-analytical models from the literature and the results compared to in situ HPLC chlorophyll- a (chla) concentrations. When applied to the limited Belgica data set the Carder et al . (1999) model gave the most accurate semi-analytical and the Kahru and Mitchell (1999) algorithm the most accurate empirical estimates of chla. When the current SeaWiFS processing algorithm (OC4) and Carder semi-analytical approaches were applied to SeaWiFS data and compared with in situ pigment measurements, the Carder algorithm was shown to give closer agreement with in situ values at both high (>1 mg m- 3 ) and low (