| 1. |
- Godhe, Anna, et al.
(author)
-
PCR amplification of microalgal DNA for sequencing and species identification : studies on fixatives and algal growth stages
- 2002
-
In: Harmful Algae. - 1568-9883 .- 1878-1470. ; 1:4, s. 375-382
-
Journal article (peer-reviewed)abstract
- Cultured strains and individually isolated dinoflagellate cells from field samples were preserved in different fixatives to find a method of cell preservation that could provide DNA template in PCR reactions and preserve cell morphology for microscopic studies. Lugol’s solution and various ethanol concentrations all showed shortcomings, whereas an initial formalin preservation step followed by storage in 100% methanol fulfilled both demands. Cells could be stored up to 1 year and still provide functional DNA template for positive PCR reactions. The amplified fragment was approximately 700 bp of the D1/D2 region of the LSU rDNA, which is to our knowledge significantly longer than the low-molecular-weight DNA typically reported from formalin preserved samples. By cloning and sequencing the PCR product and subsequently aligning the sequences with previously sequenced fragments of the same or similar species, we confirmed that no base pair alteration had taken place during the time that the cells were fixed and frozen. In another experiment it was demonstrated that the growth phase of cultured Alexandrium minutum did not have any influence on the result of PCR reactions. This was true for extracted DNA from cultures and for direct PCR with a small number of disrupted cells. Phenol/chlorophorm/isoamylalcohol extraction proved to be an unpredictable method for DNA extraction, whereas direct PCR on isolated cells was more reliable. Extracted DNA purified with a commercial DNA cleaning kit always rendered a positive PCR. The environmental condition for cells to be used as DNA template in PCR is discussed.
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| 2. |
- Godhe, Anna, et al.
(author)
-
PCR detection of dinoflagellate cysts in field sediment samples from tropic and temperate environments
- 2002
-
In: Harmful Algae. - 1568-9883 .- 1878-1470. ; 1:4, s. 361-373
-
Journal article (peer-reviewed)abstract
- Species-specific primers were constructed for Scrippsiella trochoidea, Protoceratium reticulatum and Lingulodinium polyedrum, which all are common cosmopolitan cyst forming dinoflagellates. The designed primers amplified a product of expected size from cultured planktonic cells of the three species, and did not yield any product with a wide range of other algal species used as negative controls. The PCR method for detection and identification of dinoflagellate cysts from the three species was applied on field samples. Undisturbed surface sediment was collected along the southwest coast of India and the west coast of Sweden. DNA extract from sediment including DNA from dinoflagellate cysts could be obtained after repeated grinding with mortar and pestle under liquid nitrogen followed by microwave boiling. All sediment samples that contained any of the target species as confirmed by microscopy, were also positive for PCR. Field samples negative for any of the target species by microscopy, were also negative by PCR. Restriction enzyme digestion and/or DNA sequencing confirmed the specificity of all the PCR products from field samples. The yield of DNA from sediment extraction was low, and therefore nested PCR was necessary for accurate species-specific detection of the three species in most of the field samples.
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| 3. |
- Godhe, Anna, et al.
(author)
-
PCR detection of dinoflagellate cysts in field sediment samples from tropic and temperate environments
- 2002
-
In: Harmful Algae. - : Elsevier. - 1568-9883. ; 1:4, s. 361-373
-
Journal article (peer-reviewed)abstract
- Species-specific primers were constructed for Scrippsiella trochoidea, Protoceratium reticulatum and Lingulodinium polyedrum, which all are common cosmopolitan cyst forming dinoflagellates. The designed primers amplified a product of expected size from cultured planktonic cells of the three species, and did not yield any product with a wide range of other algal species used as negative controls. The PCR method for detection and identification of dinoflagellate cysts from the three species was applied on field samples. Undisturbed surface sediment was collected along the southwest coast of India and the west coast of Sweden. DNA extract from sediment including DNA from dinoflagellate cysts could be obtained after repeated grinding with mortar and pestle under liquid nitrogen followed by microwave boiling. All sediment samples that contained any of the target species as confirmed by microscopy, were also positive for PCR. Field samples negative for any of the target species by microscopy, were also negative by PCR. Restriction enzyme digestion and/or DNA sequencing confirmed the specificity of all the PCR products from field samples. The yield of DNA from sediment extraction was low, and therefore nested PCR was necessary for accurate species-specific detection of the three species in most of the field samples.
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| 4. |
- Aguilera, Anabella, et al.
(author)
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Cyanobacterial bloom monitoring and assessment in Latin America
- 2023
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 125
-
Journal article (peer-reviewed)abstract
- Cyanobacterial blooms have serious adverse effects on human and environmental health. In Latin America, one of the main world's freshwater reserves, information on this phenomenon remains sparse. To assess the current situation, we gathered reports of cyanobacterial blooms and associated cyanotoxins in freshwater bodies from South America and the Caribbean (Latitude 22 degrees N to 45 degrees S) and compiled the regulation and monitoring procedures implemented in each country. As the operational definition of what is a cyanobacterial bloom remains controversial, we also analyzed the criteria used to determine the phenomena in the region. From 2000 to 2019, blooms were reported in 295 water bodies distributed in 14 countries, including shallow and deep lakes, reservoirs, and rivers. Cyanotoxins were found in nine countries and high concentrations of microcystins were reported in all types of water bodies. Blooms were defined according to different, and sometimes arbitrary criteria including qualitative (changes in water color, scum presence), quantitative (abundance), or both. We found 13 different cell abundance thresholds defining bloom events, from 2 x 10(3) to 1 x 10(7) cells mL(-1). The use of different criteria hampers the estimation of bloom occurrence, and consequently the associated risks and economic impacts. The large differences between countries in terms of number of studies, monitoring efforts, public access to the data and regulations regarding cyanobacteria and cyanotoxins highlights the need to rethink cyanobacterial bloom monitoring, seeking common criteria. General policies leading to solid frameworks based on defined criteria are needed to improve the assessment of cyanobacterial blooms in Latin America. This review represents a starting point toward common approaches for cyanobacterial monitoring and risk assessment, needed to improve regional environmental policies.
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| 5. |
- Angeler, David, et al.
(author)
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Algal invasions, blooms and biodiversity in lakes: Accounting for habitat-specific responses
- 2013
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In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 23, s. 60-69
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Journal article (peer-reviewed)abstract
- Range expansions of species comprise a pervasive environmental problem worldwide and can cause substantial ecological and economic impact. However, the magnitude of impact may vary across habitats, highlighting the need to account for spatial heterogeneity in assessment studies. Here we compare invertebrate community structure in three habitats (littoral, sublittoral, and profundal) of boreal lakes that suffer recurring blooms of a regionally expanding, nuisance flagellate, Gonyostomum semen (Raphidophyta), with the assemblage structure in lakes were no blooms occur. We contrast community structure over a 6-year period using univariate metrics (total abundance, community evenness, species richness, and Simpson diversity) and multivariate community similarity to infer habitat-specific associations of local (alpha) diversity. We also calculated indices of multivariate dispersion to infer associations with beta diversity; i.e., whether or not habitats in bloom lakes show faunal homogenisation. Results show that the magnitude of assemblage alteration in bloom relative to bloom-free lakes varied with habitat and increased from the littoral to the profundal habitats. Littoral assemblages in bloom and bloom-free lakes shared similar alpha (taxon richness, evenness and Simpson diversity) and beta diversity characteristics, despite differing in multivariate community similarity. By contrast, alteration of assemblage structure was most severe in the profundal and manifested in reduced diversity and faunal homogenisation (i.e. decreased beta diversity) in bloom relative to bloom-free lakes. This was due to numerical dominance of the predatory phantom midge, Chaoborus flavicans, in the profundal of bloom lakes. Not only do the results highlight that spatial heterogeneity should be accounted for to assess the potential broader impact of nuisance species on biodiversity within lakes; more generally, the dominance of a single species suggests a reduced overall resilience of bloom lakes, making them more susceptible to environmental perturbation. (C) 2013 Elsevier B.V. All rights reserved.
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| 6. |
- Bonilla, Sylvia, et al.
(author)
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Nutrients and not temperature are the key drivers for cyanobacterial biomass in the Americas
- 2023
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 121
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Journal article (peer-reviewed)abstract
- Cyanobacterial blooms imperil the use of freshwater around the globe and present challenges for water man-agement. Studies have suggested that blooms are trigged by high temperatures and nutrient concentrations. While the roles of nitrogen and phosphorus have long been debated, cyanobacterial dominance in phytoplankton has widely been associated with climate warming. However, studies at large geographical scales, covering diverse climate regions and lake depths, are still needed to clarify the drivers of cyanobacterial success. Here, we analyzed data from 464 lakes covering a 14,000 km north-south gradient in the Americas and three lake depth categories. We show that there were no clear trends in cyanobacterial biomass (as biovolume) along latitude or climate gradients, with the exception of lower biomass in polar climates. Phosphorus was the primary resource explaining cyanobacterial biomass in the Americas, while nitrogen was also significant but particularly relevant in very shallow lakes (< 3 m depth). Despite the assessed climatic gradient water temperature was only weakly related to cyanobacterial biomass, suggesting it is overemphasized in current discussions. Depth was critical for predicting cyanobacterial biomass, and shallow lakes proved more vulnerable to eutrophication. Among other variables analyzed, only pH was significantly related to cyanobacteria biomass, likely due to a biologically mediated positive feedback under high nutrient conditions. Solutions toward managing harmful cyanobacteria should thus consider lake morphometric characteristics and emphasize nutrient control, independently of tem-perature gradients, since local factors are more critical - and more amenable to controls - than global external forces.
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| 7. |
- Bravo, I, et al.
(author)
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Alexandrium catenella and Alexandrium minutum blooms in the Mediterranean Sea: Toward the identification of ecological niches
- 2008
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In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 7:4, s. 515-522
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Journal article (peer-reviewed)abstract
- Annual recurrent blooms of the toxic dinoflagellates Alexandrium catenella and Alexandrium minutum were detected from 2000 to 2003 in harbours along the Catalan coast. The interrelation study between the occurrence of the blooms and specific external conditions at the study sites demonstrated that different factors are required for the bloom of each Alexandrium species. Concentrations higher than 105 cells l−1 of A. catenella were only detected in Tarragona harbour. These blooms were associated with water surface temperature between 21 and 25 °C and salinities of around 34 psu or higher than 37 psu. A. minutum appeared widely spread along the Catalan coast, though the most intensive and recurrent blooms of this species were observed in Arenys de Mar harbour. Concentrations of millions of cells per litre of A. minutum were associated with water temperatures below 14 °C and salinities of around 34–36 psu. A. minutum cell densities showed a positive significant correlation with NO3 but a negative correlation with NH4. On the other hand, A. catenella blooms dominated when both NO3 and NH4 levels were high. The prevailing inorganic nitrogen form (NO3 vs. NH4) could explain why these two species rarely coincide in the same harbours. Accumulation of cysts in the sediment was found to be an important potential factor for the recurrence of these species. The 4.3 × 103 A. catenella cysts cm−3 of wet sediment in Tarragona harbour and the 3.02 × 103 A. minutum cysts cm−3 of wet sediment in Vilanova harbour were the highest concentrations observed from the cyst study. Confined waters such as harbours play an important role as reservoirs for the accumulation of cysts and vegetative cells, which contributes to the expansion of these dinoflagellates in the region. However, the particular environmental conditions are also decisive factors of bloom intensity.
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| 8. |
- Bravo, Isabel, et al.
(author)
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Cellular and nuclear morphological variability within a single species of the toxigenic dinoflagellate genus Gambierdiscus: Relationship to life-cycle processes
- 2014
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 40, s. 1-8
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Journal article (peer-reviewed)abstract
- Dinoflagellates belonging to the genus Gambierdiscus are the causative agent of ciguatera fish poisoning (CFP). This syndrome, which is widespread in tropical and subtropical regions, has recently been reported also in temperate latitudes. Taxonomic studies of Gambierdiscus have yet to completely couple the morphological features of member species with their genetics. In this study, the cellular and nuclear morphology of a single strain of one species of Gambierdiscus was determined in cells grown under different culture conditions. The results showed a wide-ranging variability of cell sizes, together with a clear relationship between cell size and nuclear morphology. Thus, small cells were associated with round to oval or slightly U-shaped nuclei and large cells with obviously U-shaped nuclei. Most cells exhibited the typical anterio-posteriorly compressed lenticular, shape of Gambierdiscus, with the exception of a few small globular-shaped specimens. In all cells, regardless of their size, the arrangement of the thecal plates was typical of lenticular Gambierdiscus. Dividing cells were consistently the largest. In these cells, nuclear morphology, karyokinesis, and cytokinesis were characterized. Cells underwent division only during the dark. period, thus demonstrating their spontaneous synchronized division. Cellular forms related to the sexual cycle were also present in the cultures and included gamete pairs and putative meiotic planozygotes. The effect of the culture medium was studied by means of principal component analyses, which showed a positive correlation between the medium used and nuclear size and shape but not cell size. (C) 2014 The Authors. Published by Elsevier B.V.
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| 9. |
- Brutemark, Andreas, et al.
(author)
-
Role of mixotrophy and light for growth and survival of the toxic haptophyte Prymnesium parvum
- 2011
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In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 10, s. 388-394
-
Journal article (peer-reviewed)abstract
- Mixotrophy in Prymnesium parvum was investigated using carbon (δ13C) and nitrogen (δ15N) stable isotopes. The experiment was performed in light and dark. In the dark treatment we expected that the mixotrophic P. parvum would rely solely on its prey and therefore reflect the prey isotopic signatures. In the light treatment P. parvum can perform photosynthesis as well as utilize its prey, thus we expect the isotopic signatures to be between the dark mixed cultures and the monocultures, depending on how much prey was utilized. In the light treatment, addition of the ciliate Myrionecta rubra resulted in higher P. parvum cell numbers compared to monocultures. During the experiment, cell numbers in the dark monocultures and the mixed dark cultures did not increase. P. parvum had 2.5-3 times higher cellular phosphorus and nitrogen content in the dark compared to the cultures in the light whereas no difference in carbon content between treatments could be observed. This suggests that P. parvum can utilize nitrogen and phosphorus but not carbon in the dark. It thus seems as if P. parvum relies on photosynthesis to meet the carbon and energy demand required for growth. The expected isotopic signatures “become what you eat…plus a few per mil” were not observed. In the dark treatment, the δ13C did not differ between monocultures and mixed cultures. In the light treatments P. parvum δ13C became less negative then the corresponding dark treatments indicating that P. parvum used CO2 rather than carbon from the added prey. No difference in δ15N between monocultures and mixed cultures could be observed during the experiment. We argue that light is necessary for P. parvum growth and that the ability to utilize nutrients originating from their prey may be important in bloom formation.
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| 10. |
- Burford, M. A., et al.
(author)
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Perspective: Advancing the research agenda for improving understanding of cyanobacteria in a future of global change
- 2020
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 91
-
Journal article (peer-reviewed)abstract
- Harmful cyanobacterial blooms (=cyanoHABs) are an increasing feature of many waterbodies throughout the world. Many bloom-forming species produce toxins, making them of particular concern for drinking water supplies, recreation and fisheries in waterbodies along the freshwater to marine continuum. Global changes resulting from human impacts, such as climate change, over-enrichment and hydrological alterations of waterways, are major drivers of cyanoHAB proliferation and persistence. This review advocates that to better predict and manage cyanoHABs in a changing world, researchers need to leverage studies undertaken to date, but adopt a more complex and definitive suite of experiments, observations, and models which can effectively capture the temporal scales of processes driven by eutrophication and a changing climate. Better integration of laboratory culture and field experiments, as well as whole system and multiple-system studies are needed to improve confidence in models predicting impacts of climate change and anthropogenic over-enrichment and hydrological modifications. Recent studies examining adaptation of species and strains to long-term perturbations, e.g. temperature and carbon dioxide (CO 2 ) levels, as well as incorporating multi-species and multi-stressor approaches emphasize the limitations of approaches focused on single stressors and individual species. There are also emerging species of concern, such as toxic benthic cyanobacteria, for which the effects of global change are less well understood, and require more detailed study. This review provides approaches and examples of studies tackling the challenging issue of understanding how global changes will affect cyanoHABs, and identifies critical information needs for effective prediction and management. © 2019
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| 11. |
- Carlsson, Per, et al.
(author)
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Sedimentation of Nodularia spumigena and distribution of nodularin in the food web during transport of a cyanobacterial bloom from the Baltic Sea to the Kattegat
- 2019
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In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 86, s. 74-83
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Journal article (peer-reviewed)abstract
- Nodularia spumigena is a toxic cyanobacteria that blooms in the Baltic Sea every year. In the brackish water of the Baltic Sea, its toxin, nodularin, mainly affects the biota in the surface water due to the natural buoyancy of this species. However, the fate of the toxin is unknown, once the cyanobacteria bloom enters the more saline waters of the Kattegat. In order to investigate this knowledge gap, a bloom of N. spumigena was followed during its passage, carried by surface currents, from the Baltic Sea into the Kattegat area, through the Öresund strait. N. spumigena cells showed an increased cell concentration through the water column during the passage of the bloom (up to 130 103 cells ml−1), and cells (4.2 103 cells ml−1)could be found down to 20 m depth, below a pycnocline. Sedimentation trap samples from below the pycnocline (10–12 m depth)also showed an increased sedimentation of N. spumigena filaments during the passage of the bloom. The toxin nodularin was detected both in water samples (0.3–6.0 μg l−1), samples of sedimenting material (a toxin accumulation rate of 20 μg m-2 day−1), zooplankton (up to 0.1 ng ind.−1 in copepods), blue mussels (70–230 μg kg−1 DW), pelagic and benthic fish (herring (1.0–3.4 μg kg−1 DW in herring muscle or liver)and flounder (1.3-6.2 μg kg−1 DW in muscle, and 11.7-26.3 μg kg−1 DW in liver). A laboratory experiment showed that N. spumigena filaments developed a decreased buoyancy at increased salinities and that they were even sinking with a rate of up to 1,7 m day−1 at the highest salinity (32 PSU). This has implications for the fate of brackish water cyanobacterial blooms, when these reach more saline waters. It can be speculated that a significant part of the blooms content of nodularin will reach benthic organisms in this situation, compared to blooms decaying in brackish water, where most of the bloom is considered to be decomposed in the surface waters.
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| 12. |
- Carvalho, Wanderson, et al.
(author)
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Dinophysis norvegica (Dinophyceae), more a predator than a producer?
- 2008
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In: Harmful Algae. - : Elsevier B.V. - 1568-9883 .- 1878-1470. ; 7:2, s. 174-183
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Journal article (peer-reviewed)abstract
- Several studies have proved that some Dinophysis species are capable of ingesting particulate organic matter besides of being photosynthetic, a form of nutrition termed mixotrophy. Phagotrophy may be an important aspect of the life history of the genus Dinophysis and the key to understand its ecology. We used modern techniques coupling flow cytometry and acidotropic probes to detect and score food vacuolated Dinophysis norvegica cells in natural samples. In addition, feeding experiments were conduced under controlled conditions to observe if D. norvegica would grow feeding on the cryptophyte Teleaulax amphioxeia. The results of the field observations showed a frequency of phagotrophy between 25 and 71% in a natural D. norvegica population from the Baltic Sea, which is higher than previous reports (1–20%). Although molecular methods have proved that the kleptoplastids of the D. norvegica from the Baltic Sea are from T. amphioxeia, the laboratory experiments showed that the presence of T. amphioxeia in the cultures did not enhance the survival rate of D. norvegica neither in phototrophic nor in heterotrophic conditions. We suggest that the D. norvegica Kleptoplats are obtained through a heterotrophic or mixotrophic protist, which have been feeding on cryptophytes, as it has recently been shown for Dinophysis acuminata. Our main conclusion is that D. norvegica, and probably all other species from the genus Dinophysis, is mainly phagotrophic and feeds on a larger prey than T. amphioxeia. Autotrophy through kleptoplastidy would be a secondary feature used as a complementary or short-term survival strategy.
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| 13. |
- Diaz, Patricio A., et al.
(author)
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Coupling planktonic and benthic shifts during a bloom of Alexandrium catenella in southern Chile: Implications for bloom dynamics and recurrence
- 2014
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 40, s. 9-22
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Journal article (peer-reviewed)abstract
- Cell abundances and distributions of Alexandrium catenella resting cysts in recent sediments were studied along time at two locations in the Chilean Inland Sea exposed to different oceanographic conditions: Low Bay, which is much more open to the ocean than the more interior and protected Ovalada Island. The bloom began in interior areas but maximum cyst concentrations were recorded in locations more open to the ocean, at the end of the Moraleda channel. Our results showed a time lapse of around 3 months from the bloom peak (planktonic population) until the number of resting cysts in the sediments reached a maximum. Three months later, less than 10% of the A. catenella cysts remained in the sediments. Maximum cyst numbers in the water column occurred one month after the planktonic peak, when no cells were present. The dinoflagellate assemblage at both study sites was dominated by heterotrophic cysts, except during the A. catenella bloom. CCA analyses of species composition and environmental factors indicated that the frequency of A. catenella blooms was associated with low temperatures, but not with salinity, chlorophyll a concentration, and predator presence (measured as clam biomass). However, resting cyst distribution was only related to cell abundance and location. The occurrence of A. catenella cysts was also associated with that of cysts from the toxic species Protoceratium reticulatum. By shedding light on the ecological requirements of A. catenella blooms, our observations support the relevance of encystment as a mechanism of bloom termination and show a very fast depletion of cysts from the sediments (<3 months), which suggest a small role for resting cyst deposits in the recurrence of A. catenella blooms in this area. (C) 2014 The Authors. Published by Elsevier B.V.
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| 14. |
- F de Carvalho, Wanderson, et al.
(author)
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Contribution of phagotrophy versus autotrophy to Prymnesium parvum growth under nitrogen and phosphorus sufficiency and deficiency
- 2010
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In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 9, s. 105-115
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Journal article (peer-reviewed)abstract
- Laboratory experiments were conducted to test the effects of nitrogen (N) and phosphorus (P) sufficiency and deficiency on mixotrophy in Prymnesium parvum (Haptophyta). A parvum was grown with and without algal prey (Rhodomonas salina) and observed for 120 h. Detection and enumeration of cells containing food vacuoles with prey (i.e. phagotrophy) was based on flow cytometric detection of fluorescence of an acidotropic probe. Overall, the presence of R. salina increased phagotrophy in P. parvum suggesting that, at least in this strain of P. parvum, the presence of suitable prey can stimulate phagotrophic behavior in P. parvum. Feeding frequency (the percentage of A parvum cells containing food vacuoles in a given time) was significantly higher under N and P deficiency than in the nutrient-sufficient treatments. A nutrient budget constructed from the data indicated that ingestion of organic matter (OM) supplied with 78 +/- 7% of the N (3.9 +/- 0.3 mu M) incorporated by P. parvum in the N-deficient treatment, and 45 +/- 9% of the P (0.3 +/- 0 mu M) acquired in the P-deficient cultures. Even under nutrient sufficiency, ingestion of OM was estimated to have supplied 43 +/- 16% of the N and 48 +/- 16% of the P incorporated into P. parvum cells. Phagotrophy was observed even in the NP-sufficient cultures (non-axenic mixed and monocultures), although P. parvum cells did not lose their photosynthetic capability, suggesting that phagotrophy is probably a permanent nutritional adaptation to this species. The ingestion of organic nutrients played an important role in P. parvum growth, being a reliable source of nutrition for P. parvum inorganic nutrient limitation, and could explain its capabilities to form persistent blooms. (C) 2009 Elsevier B.V. All rights reserved.
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| 15. |
- Fagerberg, Tony, et al.
(author)
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A large molecular size fraction of riverine high molecular weight dissolved organic matter (HMW DOM) stimulates growth of the harmful dinoflagellate Alexandrium minutum
- 2009
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In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8:6, s. 823-831
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Journal article (peer-reviewed)abstract
- An increase in the concentration of riverine dissolved organic matter (DOM) has been observed during the last decades, and this material can stimulate marine plankton in coastal waters with significant freshwater input. We studied the effect of two size fractions of riverine high molecular weight dissolved organic matter (HMW DOM), isolated with tangential ultrafiltration, on the harmful dinoflagellate Alexandrium minutum and a natural isolate of marine bacteria under laboratory conditions. Both A. minutum and bacteria grew significantly better with the low MW DOM compared to both the high MW DOM fraction and controls (no DOM additions). This experiment demonstrates that the harmful algae A. minutum and bacteria benefit from larger molecules of river HMW DOM, and highlights the potential of A. minutum to utilize organic nitrogen from large DOM molecules. This ability may enhance their likelihood of success in estuaries/costal waters with a humic rich freshwater input, especially when the relative amount of large molecules within DOM is more pronounced.
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| 16. |
- Figueroa, Rosa Isabel, et al.
(author)
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Life histories of microalgal species causing harmful blooms : Haploids, diploids and the relevance of benthic stages
- 2018
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 73, s. 44-57
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Journal article (peer-reviewed)abstract
- In coastal and offshore waters, Harmful Algal Blooms (HABs) currently threaten the well-being of coastal countries. These events, which can be localized or involve wide-ranging areas, pose risks to human health, marine ecosystems, and economic resources, such as tourism, fisheries, and aquaculture. Dynamics of HABs vary from one site to another, depending on the hydrographic and ecological conditions. The challenge in investigating HABs is that they are caused by organisms from multiple algal classes, each with its own unique features, including different life histories. The complete algal life cycle has been determined in <1% of the described species, although elucidation of the life cycles of bloom-forming species is essential in developing preventative measures. The knowledge obtained thus far has confirmed the complexity of the algal life cycle, which is composed of discrete life stages whose morphology, ecological niche (plankton/benthos), function, and lifespan vary. The factors that trigger transitions between the different stages in nature are mostly unknown, but it is clear that an understanding of this process provides the key to effectively forecasting bloom recurrence, maintenance, and decline. Planktonic stages constitute an ephemeral phase of the life cycle of most species whereas resistant, benthic stages enable a species to withstand adverse conditions for prolonged periods, thus providing dormant reservoirs for eventual blooms and facilitating organismal dispersal. Here we review current knowledge of the life cycle strategies of major groups of HAB producers in marine and brackish waters. Rather than providing a comprehensive discussion, the objective was to highlight several of the research milestones that have changed our understanding of the plasticity and frequency of the different life cycle stages as well as the transitions between them. We also discuss the relevance of benthic and planktonic forms and their implications for HAB dynamics.
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| 17. |
- Gao, Yida, et al.
(author)
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Spatiotemporal genetic structure of regional-scale Alexandrium catenella dinoflagellate blooms explained by extensive dispersal and environmental selection
- 2019
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In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 86, s. 46-54
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Journal article (peer-reviewed)abstract
- Paralytic Shellfish Poisoning (PSP) caused by the dinoflagellate Alexandrium catenella is a well-known global syndrome that negatively impacts human health and fishery economies. Understanding the population dynamics and ecology of this species is thus important for identifying determinants of blooms and associated PSP toxicity. Given reports of extensive genetic heterogeneity in the toxicity and physiology of Alexandrium species, knowledge of genetic population structure in harmful algal species such as A. catenella can also facilitate the understanding of toxic bloom development and ecological adaptation. In this study we employed microsatellite markers to analyze multiple A. catenella strains isolated from several sub-regions in the Gulf of Maine (GoM) during summer blooms, to gain insights into the sources and dynamics of this economically important phytoplankton species. At least three genetically distinct clusters of A. catenella were identified in the GoM. Each cluster contained representatives from different sub-regions, highlighting the extent of connectivity and dispersal throughout the region. This shared diversity could result from cyst beds created by previous coastal blooms, thereby preserving the overall diversity of the regional A. catenella population. Rapid spatiotemporal genetic differentiation of A. catenella populations was observed in local blooms, likely driven by natural selection through environmental conditions such as silicate and nitrate/nitrite concentrations, emphasizing the role of short-term water mass intrusions and biotic processes in determining the diversity and dynamics of marine phytoplankton populations. Given the wide-spread intraspecific diversity of A. catenella in GoM and potentially elsewhere, harmful algal blooms will likely persist in many regions despite global warming and changing environmental conditions in the future. Selection of different genetic lineages through variable hydrological conditions might impact toxin production and profiles of future blooms, challenging HAB control and prediction of PSP risk in the future.
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| 18. |
- Ger, Kemal Ali, et al.
(author)
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The interaction between cyanobacteria and zooplankton in a more eutrophic world
- 2016
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In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 54, s. 128-144
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Research review (peer-reviewed)abstract
- As blooms of cyanobacteria expand and intensify in freshwater systems globally, there is increasing interest in their ecological effects. In addition to being public health hazards, cyanobacteria have long been considered a poor quality food for key zooplankton grazers that link phytoplankton to higher trophic levels. While past laboratory studies have found negative effects of nutritional constraints and defensive traits (i.e., toxicity and colonial or filamentous morphology) on the fitness of large generalist grazers (i.e., Daphnia), cyanobacterial blooms often co-exist with high biomass of small-bodied zooplankton in nature. Indeed, recent studies highlight the remarkable diversity and flexibility in zooplankton responses to cyanobacterial prey. Reviewed here are results from a wide range of laboratory and field experiments examining the interaction of cyanobacteria and a diverse zooplankton taxa including cladocerans, copepods, and heterotrophic protists from temperate to tropical freshwater systems. This synthesis shows that longer exposure to cyanobacteria can shift zooplankton communities toward better-adapted species, select for more tolerant genotypes within a species, and induce traits within the lifetime of individual zooplankton. In turn, the function of bloom-dominated plankton ecosystems, the coupling between primary producers and grazers, the stability of blooms, and the potential to use top down biomanipulation for controlling cyanobacteria depend largely on the species, abundance, and traits of interacting cyanobacteria and zooplankton. Understanding the drivers and consequences of zooplankton traits, such as physiological detoxification and selective vs. generalist grazing behavior, are therefore of major importance for future studies. Ultimately, co-evolutionary dynamics between cyanobacteria and their grazers may emerge as a critical regulator of blooms.
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| 19. |
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| 20. |
- Godhe, Anna, 1967, et al.
(author)
-
Intercalibration of classical and molecular techniques for identification of Alexandrium fundyense (Dinophyceae) and estimation of cell densities
- 2007
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 6:1, s. 56-72
-
Journal article (peer-reviewed)abstract
- A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques - nine classical microscopic-based and eight molecular methods - were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100 cells L-1, but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration. (c) 2006 Elsevier B.V. All rights reserved.
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| 21. |
- Gorokhova, Elena
(author)
-
Toxic cyanobacteria Nodularia spumigena in the diet of Baltic mysids : Evidence from molecular diet analysis
- 2009
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 8:2, s. 264-272
-
Journal article (peer-reviewed)abstract
- A PCR-based method was used to detect toxic cyanobacteria Nodularia spumigena in the diet of Baltic mysids, Mysis mixta and Mysis relicta. The decay in detectability of Nodularia DNA in mysid stomachs and feces following the cyanobacterium consumption was examined in laboratory with special references to (1) marker size (780 by vs. 200 bp), (2) mysid developmental stage (juveniles vs. subadults), and (3) feeding regime after consuming the cyanobacteria (continuous vs. interrupted feeding). The Nodularia DNA could be reliably detected in mysid stomachs and feces by PCR technique. In the mysid with interrupted feeding, the calculated half-lives of N. spumigena DNA in the mysid stomachs were 1.2 and 6.1 h for 780 and 200 by fragments, respectively. Continuous feeding, however, facilitated decay in the detectability, most likely due to increased gut evacuation rate. In stomachs of the field-collected mysids, the Nodularia DNA was detected with high frequencies, 60% in M. mixta and 51 % in M. relicta. Moreover, it was higher in immature mysids than in adults and correlated with stomach fullness in age-specific manner: in juveniles and subadults, stomachs containing Nodularia were significantly fuller, while in adults, the presence of the cyanobacteria was associated with empty stomachs. This suggests greater habitat overlap for juvenile mysids and N. spumigena and thus higher encounter and consumption rates. These findings contribute to a growing body of evidence that cyanobacteria in the Baltic Sea are important food for grazers.
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| 22. |
- Granéli, Edna, et al.
(author)
-
Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
- 2011
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 10:2, s. 165-172
-
Journal article (peer-reviewed)abstract
- Ostreopsis ovata Fukuyo is an epiphytic, toxic dinoflagellate, inhabiting tropical and sub-tropical waters worldwide and also in certain temperate waters such as the Mediterranean Sea. Toxic blooms of O. ovata have been reported in SE Brazil in 1998/99 and 2001/02 and the French-Italian Riviera in 2005 and 2006. These blooms had negative effects on human health and aquatic life. Chemical analyses have indicated that O. ovata cells produce palytoxin, a very strong toxin, only second in toxicity to botulism. Increase in water temperature by several degrees has been suggested as the reason for triggering these blooms. Four laboratory experiments were performed with O. ovata isolated from Tyrrhenian Sea, Italy to determine the effects of water temperature and co-occurring algae on the cell growth and/or the toxicity of O. ovata. The cells were grown under different temperatures ranging from 16 °C to 30 °C, and cell densities, growth rates and the cell toxicities were studied. Results indicated high water temperatures (26-30 °C) increased the growth rate and biomass accumulation of O. ovata. In mixed cultures of O. ovata with other co-occurring algae, biomass decreased due to grazing by ciliates. Cell toxicity on the other hand was highest at lower temperatures, i.e., between 20 and 22 °C. The present study suggests that sea surface temperature increases resulted by global warming could play a crucial role inducing the geographical expansion and biomass accumulation by blooms of O. ovata.
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| 23. |
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| 24. |
- Granéli, Edna, et al.
(author)
-
The ecophysiology and bloom dynamics of Prymnesium spp.
- 2012
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 14:SI, s. 260-270
-
Journal article (peer-reviewed)abstract
- Members of Prymnesium belong to the division Haptophyta, class Prymnesiophyceae, order Prymnesialesand family Prymnesiaceae. As most haptophytes, members of the genus Prymnesium are unicellular andplanktonic. The most known of these species is the ichthyotoxic P. parvum, which may form nearlymonospecific dense blooms in coastal and inland waters. This species possesses extraordinary plasticityconcerning life survival strategies, and is specifically addressed in this review.Toxins produced by P. parvum have hemolytic properties, that not only kill fish but also co-existingplankton. These substances are allelopathic (when other algae are killed) and grazer deterrent (whengrazers are killed). Allelopathy enables P. parvum to utilize inorganic nutrients present in the surroundingwater without competition from other algal species; and by eliminating its grazers P. parvum reduces celllosses. The paralized microalgae and/or zooplankton, are therefter ingested by the P. parvum cells, aprocess called phagotrophy. P. parvum is also able of osmotrophy, i.e. utilization of dissolved organicmatter. In this review, the cellular characteristics, life cycles, bloom formation, and factors affectingtoxicity, allelopathy, phagotrophy, and osmotrophy of P. parvum are discussed.
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| 25. |
- Gustafsson, Susanne, et al.
(author)
-
On the control of HAB species using low biosurfactant concentrations
- 2009
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8, s. 857-863
-
Journal article (peer-reviewed)abstract
- Biosurfactants have been suggested as a method to control harmful algal blooms (HABs), but warrant further and more in-depth investigation. Here we have investigated the algicidal effect of a biosurfactant produced by the bacterium Pseudomonas aeruginosa on five diverse marine and freshwater HAB species that have not been tested previously. These include Alexandrium minutum (Dinophycaee), Karenia brevis (Dinophyceae), Pseudonitzschia sp. (Bacillariophyceae), in marine ecosystems, and Gonyostomum semen (Raphidophyceae) and Microcystis aeruginosa (Cyanophyecae) in freshwater. We examined not only lethal but also sub-lethal effects of the biosurfactant. In addition, the effect of the biosurfactant on Daphnia was tested. Our conclusions were that very low biosurfactant concentrations (5 μg mL−1) decreased both the photosynthesis efficiency and the cell viability and that higher concentrations (50 μg mL−1) had lethal effects in four of the five HAB species tested. The low concentrations employed in this study and the diversity of HAB genera tested suggest that biosurfactants may be used to either control initial algal blooms without causing negative side effect to the ecosystem, or to provoke lethal effects when necessary.
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| 26. |
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| 27. |
- Harris, Ted D., et al.
(author)
-
What makes a cyanobacterial bloom disappear? : A review of the abiotic and biotic cyanobacterial bloom loss factors
- 2024
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 133
-
Research review (peer-reviewed)abstract
- Cyanobacterial blooms present substantial challenges to managers and threaten ecological and public health. Although the majority of cyanobacterial bloom research and management focuses on factors that control bloom initiation, duration, toxicity, and geographical extent, relatively little research focuses on the role of loss processes in blooms and how these processes are regulated. Here, we define a loss process in terms of population dynamics as any process that removes cells from a population, thereby decelerating or reducing the development and extent of blooms. We review abiotic (e.g., hydraulic flushing and oxidative stress/UV light) and biotic factors (e.g., allelopathic compounds, infections, grazing, and resting cells/programmed cell death) known to govern bloom loss. We found that the dominant loss processes depend on several system specific factors including cyanobacterial genera -specific traits, in situ physicochemical conditions, and the microbial, phytoplankton, and consumer community composition. We also address loss processes in the context of bloom management and discuss perspectives and challenges in predicting how a changing climate may directly and indirectly affect loss processes on blooms. A deeper understanding of bloom loss processes and their underlying mechanisms may help to mitigate the negative consequences of cyanobacterial blooms and improve current management strategies.
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| 28. |
- Johansson, Karin S L, et al.
(author)
-
Development of a quantitative PCR method to explore the historical occurrence of a nuisance microalga under expansion
- 2016
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 56, s. 67-76
-
Journal article (peer-reviewed)abstract
- A number of marine and freshwater harmful algal bloom (HAB) species have colonized new areas and expanded their habitat range in recent years. Nevertheless it is notoriously difficult to establish when colonization first occurred, what the dispersal routes are, and to separate recent invasion from increases in existent but small populations. The freshwater raphidophyte Gonyostomum semen is a nuisance species that has expanded its habitat range and increased in abundance in northern Europe during the past decades. To evaluate to what extent sediments can be used for determining historic occurrence of G. semen, a quantitative real-time PCR method for detecting cysts of this algae was developed. This paper presents a qPCR protocol with a set of primers that are specific to Gonyostomum and with PCR conditions optimized for sediment samples from humic lakes, which are the common habitat of G. semen. With this sensitive method as few as 1.6 cysts per PCR reaction could be reliably quantified, corresponding to 320 cysts per g wet weight sediment. Cysts were present in sediments with ages ranging from years to decades and their persistence allows detection of historic populations up to at least 50 years old. With this qPCR assay it will be possible to trace the presence of G. semen in environments prior to the onset of algae-specific monitoring programs as well as for quantification in water column samples. © 2016 The Authors.
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| 29. |
- Kahru, Mati, et al.
(author)
-
Cyanobacterial blooms in the Baltic Sea : Correlations with environmental factors
- 2020
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 92
-
Journal article (peer-reviewed)abstract
- Massive cyanobacteria blooms occur almost every summer in the Baltic Sea but the capability to quantitatively predict their extent and intensity is poorly developed. Here we analyse statistical relationships between multi-decadal satellite-derived time series of the frequency of cyanobacteria surface accumulations (FCA) in the central Baltic Sea Proper and a suite of environmental variables. Over the decadal scale (similar to 5-20 years) FCA was highly correlated (R-2 similar to 0.69) with a set of biogeochemical variables related to the amount of phosphorus and hypoxia in bottom layers. Water temperature in the surface layer was also positively correlated with FCA at the decadal scale. In contrast, the inter-annual variations in FCA had no correlation with the biogeochemical variables. Instead, significant correlations were found with the solar shortwave direct flux in July and the sea-surface temperature, also in July. It thus appears that it is not possible to predict inter-annual fluctuations in cyanobacteria blooms from water chemistry. Moreover, environmental variables could only explain about 45% of the inter-annual variability in FCA, probably because year-to-year variations in FCA are significantly influenced by biological interactions.
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| 30. |
- Karlson, Agnes M. L., 1981-, et al.
(author)
-
Benthic fauna affects recruitment from sediments of the harmful cyanobacterium Nodularia spumigena
- 2012
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 20, s. 126-131
-
Journal article (peer-reviewed)abstract
- Physical disturbance and feeding by macrofauna in the sediment can potentially affect bloom initiation of phytoplankton species that have benthic stages in their life cycle. In this experimental study, we investigated how different species of macrozoobenthos can affect the recruitment of Nodularia spumigena from the sediment to the water column. N. spumigena is a toxic, nitrogen-fixing filamentous cyanobacterium, which forms large summer blooms in the Baltic Sea. Benthic recruitment from resting stages (akinetes) and vegetative cells deposited on the seafloor have long been suspected to initiate the blooms. We found that, depending on species-specific traits, deposit-feeding macrofauna (an amphipod, Monoporeia affinis, a bivalve, Macoma balthica and an invasive polychaete, Marenzelleria cf. arctia) has the potential to either reduce or facilitate recruitment of this cyanobacterium. Shorter filament length in treatments with fauna than in the treatment without indicates feeding on or mechanical destruction of N. spumigena by the animals. Our results show the importance of an often overlooked aspect of phytoplankton bloom initiation, the role of macrozoobenthos.
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| 31. |
- Karlson, Agnes M. L., et al.
(author)
-
Deposit-feeders accumulate the cyanobacterial toxin nodularin
- 2011
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 12, s. 77-81
-
Journal article (peer-reviewed)abstract
- Blooms of toxic cyanobacteria may potentially affect food web productivity and even be a human health hazard. In the Baltic Sea, regularly occurring summer blooms of nitrogen-fixing cyanobacteria are often dominated by Nodularia spumigena, which produces the potent hepatotoxin nodularin. Evidence of sedimentation of these blooms indicates that benthic fauna can be exposed to nodularin. In a one month experiment, we simulated the settling of a summer bloom dominated by N. spumigena in sediment microcosms with three species of sediment-dwelling, deposit-feeding macrofauna, the amphipods Monoporeia affinis and Pontoporeia femorata and the bivalve Macoma balthica, and analyzed nodularin in the animals by HPLC-ESI-MS (high-performance liquid chromatography-electrospray ionization-mass spectrometry). We found nodularin in quantities of 50-120ngg-1 DW. The results show that deposit-feeding macrofauna in the Baltic Sea may contribute to trophic transfer of nodularin.
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| 32. |
- Kozlowsky-Suzuki, Betina, et al.
(author)
-
Food selectivity and grazing impact on toxic Dinophysis spp. by copepods feeding on natural plankton assemblages
- 2006
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 5:1, s. 57-68
-
Journal article (peer-reviewed)abstract
- Food selectivity and grazing impact by Acartia bifilosa, Temora longicornis and Centropages typicus on Dinophysis spp. plankton assemblages were experimentally investigated in the Baltic Sea. Toxin analyses were carried out on phyto- and zooplankton-dominated size fractions from field-collected samples to assess if toxins produced by Dinophysis spp. would end up in the zooplankton. All copepod species fed,actively on toxic Dinophysis spp. (Dinophysis acuta and Dinophysis norvegica). Despite the non-selective feeding behaviour by T longicornis and C. typicus, selectivity coefficients on D. acuta progressively decreased as food availability increased. Similar response was not observed for A. bifilosa, which displayed an even less selective behaviour. A. bifilosa had no significant negative effect on the net growth of D. norvegica at the lowest food concentration offered, whereas T longicornis and C typicus had significant negative effects on the net growth of D. acuta at low concentrations, similar to those observed in situ. Both species could potentially contribute as a substantial loss factor for Dinophysis spp. provided they are abundant at the onset of the blooms. The estimated grazing impact by the copepod populations was only considerable when C typicus abundance was high and D. acuta population in sharp decline. Our results suggest that when high abundance of grazers and poor growth condition of prey populations prevail, grazing impact by copepods can contribute considerably to prevent Dinophysis spp. populations to grow or to cause the populations to decline. Okadaic acid was detected in the zooplankton size fraction at one occasion, but the concentration was far lower than the one expected from the ingested toxins. Thus, even if copepods may act as vectors of DSP-toxins to higher trophic levels, the amount of these toxins transported in the food web by copepods seems limited. (C) 2005 Elsevier B.V. All rights reserved.
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| 33. |
- Kozlowsky-Suzuki, Betina, et al.
(author)
-
Glutathione transferase activity and oocyte development in copepods exposed to toxic phytoplankton
- 2009
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8:3, s. 395-406
-
Journal article (peer-reviewed)abstract
- Organisms present a series of cellular mechanisms to avoid the effects of toxic compounds. Such mechanisms include the increase in activity of detoxification enzymes [e.g., 7-ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST)I, which could explain the low retention of ingested toxins generally observed in copepods. In addition, decreasing gross growth efficiency (GGE) of copepods with increasing concentration of toxic diets could be caused either by a high expenditure coping with toxins (e.g., increase in the activity of detoxification enzymes) or by a deterioration of reproductive tissues. To assess the effect of toxic phytoplankton on the activity of detoxification enzymes and on oocyte maturation of Acartia tonsa and Temora longicornis, feeding and egg production experiments were carried out with a variety of toxic diets and an adequate non-toxic food control (Rhodomonas spp.) all provided as single species diets. Toxic diets included the nodularin-producing cyanobacterium Nodularia spumigena, the dinoflagellates Alexandrium minutum, and A. tamarense, which contained Paralytic Shellfish Poisoning (PSP) toxins, the dinoflagellate Prorocentrum lima with Diarrhetic Shellfish Poisoning (DSP) toxins and the haptophyte Prymnesium parvum, which produces ichtyotoxins with haemolytic activity. Feeding on toxic diets was lower than on Rhodomonas spp., except for A. minutum and A. tamarense. In addition, toxic diets negatively affected reproduction in both copepod species with the production of oocytes and oocyte development impaired with A. minutum and N. spumigena. While the negative effect of N. spumigena seemed to be connected to gonad atresia likely caused by severe food limitation (starvation), the negative effect of A. minutum could have been either caused by a direct effect of saxitoxins or nutritional inadequacy on oocyte production. We could not detect EROD activity in the copepods, while the activity of GST was generally higher with the non-toxic food control and positively related to the feeding and egestion rates, suggesting relation to feeding conditions rather than to exposure to toxic diets. No relationship was found between GGE and CST activity. Our results refute the hypothesis that toxic diets, provided at ecologically relevant levels, would induce cellular mechanisms in copepods regarding GST activity. GST activity thus seems to play no role in detoxification of copepods confronted with toxic phytoplankton. Toxin detoxification and its cost for copepods still remain an open question. (C) 2008 Elsevier B.V. All rights reserved.
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| 34. |
- Lage, Sandra, et al.
(author)
-
The effect of exogenous β-N-methylamino-l-alanine (BMAA) on the diatoms Phaeodactylum tricornutum and Thalassiosira weissflogii
- 2016
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 58, s. 85-92
-
Journal article (peer-reviewed)abstract
- β-N-methylamino-l-alanine (BMAA), a non-protein amino acid with neurodegenerative features, is known to be produced by cyanobacteria, diatoms and a dinoflagellate. BMAA research has intensified over the last decade, and knowledge has been gained about its bioaccumulation in aquatic and terrestrial ecosystems, toxic effects in model organisms and neurotoxicity in vivo and in vitro. Nevertheless, knowledge of the actual physiological role of BMAA in the producing species or of the ecological factors that regulate BMAA production is still lacking. A few studies propose that BMAA functions to signal nitrogen depletion in cyanobacteria. To investigate whether BMAA might have a similar role in diatoms, two diatom species – Phaeodactylum tricornutum and Thalassiosira weissflogii – were exposed to exogenous BMAA at environmental relevant concentrations, i.e. 0.005, 0.05 and 0.5 μM. BMAA was taken up in a concentration dependent manner in both species in the BMAA free fraction and in the protein fraction of T. weissflogii. As a result of the treatments, the diatom cells at some of the time points and at some of the BMAA concentrations exhibited lower concentrations of chlorophyll a and protein, in comparison to controls. At the highest (0.5 μM) concentration of BMAA, extracellular ammonia was found in the media of both species at all time points. These results suggest that BMAA interferes with nitrogen metabolism in diatoms, possibly by inhibiting ammonium assimilation via the GS/GOGAT pathway.
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| 35. |
- Lindahl, Odd, et al.
(author)
-
Toxicity of Dinophysis spp. in relation to population density and environmental conditions on the Swedish west coast
- 2007
-
In: Harmful Algae. - 1568-9883. ; 6:2, s. 218-231
-
Journal article (peer-reviewed)abstract
- The aim of this study in the field was to investigate whether there are differences between the outer archipelago (Gullmar Fjord) and a semi-enclosed fjord system (Koljo Fjord) in occurrences of D. acuta and D. acuminata as well as in their content of diarrheic shellfish toxin (DST) per cell. When all data pairs of cell toxicity of D. acuminata and the corresponding number of cells l(-1) from the two sites were tested in a regression analysis, a statistically significant negative correlation became evident and was apparent as a straight line on a log-log plot (p < 0.0001). Obviously, there was an overall inverse relationship between the population density of D. acuminata and the toxin content per cell. Plotted on a linear scale, all data-pairs of cell toxicity and cell number made up a parabolic curve. On this curve the data-pairs could be separated into three groups: (i) D. acuminata occurring in numbers of fewer than approximately 100 cells l(-1), and with a toxin content per cell above 5 rho g cell(-1); (ii) cell numbers between 100 and approximately 250 cells l(-1) with a cell toxin content from 5 to 2 rho g cell(-1); (iii) when the population became greater than 250 cells l(-1), the toxicity, with few exceptions, was less than 2 rho g cell(-1). By applying this subdivision, some clear patterns of the distribution of the differently toxic D. acuminata became evident. When comparing the cell toxicity of the two sites, it was obvious that the D. acuminata cells from all depths from the Gullmar Fjord as a mean were significantly more toxic compared to the Koljo Fjord samples. The results have demonstrated that approximately 100 high-toxicity cells in a low-density population at surface may lead to the same accumulation of DST in a mussel as the ingestion of 1500 low-toxicity cells from a high-density pycnocline population. (c) 2006 Elsevier B.V. All rights reserved.
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| 36. |
- Lindehoff, Elin, et al.
(author)
-
Effect of tertiary sewage effluent additions on Prymnesium parvum cell toxicity and stable isotope ratios
- 2009
-
In: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8:2, s. 247-253
-
Journal article (peer-reviewed)abstract
- We investigated the ability of the ichthyotoxic haptophyte Prymnesium parvum to use sewage-originated nutrients applying stable carbon (C) and nitrogen (N) isotope techniques. P. parvum was cultured under N and phosphorus (P) sufficient and deficient conditions in either sewage effluent-based medium or in a nitrate- and phosphate-based control. Cell densities and toxicities were monitored and stable carbon N isotopes signatures (delta C-13 and delta N-15) of P. parvum and the sewage effluent analysed. Nitrogen and P sufficient cultures achieved the highest biomass followed by P and N deficient cultures, regardless of sewage effluent additions. The P deficient cultures with sewage effluent had higher toxicity, estimated as haemolytic activity (9.4 +/- 0 x 10(-5) mg Saponin equiv. cell(-1)) compared to the P deficient control and to all N deficient and NP sufficient cultures. Nutrient deficient conditions had no effect on the cell delta N-15, but a decreasing effect on delta C-13 in the inorganic N deficient treatment. Growth in sewage-based media was followed by a substantial increase in the cell delta N-15 (10.4-16.1.60) compared to the control treatments (2.4-4.9%o), showing that P. parvum is capable of direct use of sewage-originated N, inorganic as well as organic. Uptake of terrestrial derived C in the sewage treatments was confirmed by a decrease in cell delta C-13, implying that P. parvum is able to utilize organic nutrients in sewage effluent. (C) 2008 Elsevier B.V. All rights reserved.
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| 37. |
- Lindehoff, Elin, et al.
(author)
-
Nitrogen uptake kinetics of Prymnesium parvum (Haptophyte)
- 2011
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 12, s. 70-76
-
Journal article (peer-reviewed)abstract
- The uptake rates of different nitrogen (N) forms (NO3-, urea, and the amino acids glycine and glutamicacid) by N-deficient, laboratory-grown cells of the mixotrophic haptophyte, Prymnesium parvum, weremeasured and the preference by the cells for the different forms determined. Cellular N uptake rates(rcell, fmol N cell-1 h-1) were measured using 15N-labeled N substrates. P. parvum showed highpreference for the tested amino acids, in particular glutamic acid, over urea and NO3 under the culturenutrient conditions. However, extrapolating these rates to Baltic Seawater summer conditions, P. parvumwould be expected to show higher uptake rates of NO3- and the amino acids relative to urea because ofthe difference in average concentrations of these substrates. A high uptake rate of glutamic acid at lowsubstrate concentrations suggests that this substrate is likely used through extracellular enzymes.Nitrate, urea and glycine, on the other hand, showed a non-saturating uptake over the tested substrateconcentration (1–40 mM-N for NO3- and urea, 0.5–10 mM-N for glycine), indicating slower membranetransportrates for these substrates
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| 38. |
- Lundgren, Veronica, et al.
(author)
-
Influence of Acartia cf. bifilosa (Copepoda) on morphology and toxicity of Nodularia spumigena (Cyanophyceae)
- 2012
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 18, s. 35-46
-
Journal article (peer-reviewed)abstract
- Nodularia spumigena was exposed directly and indirectly (grazer cages) to increasing densities of Acartiacf. bifilosa to investigate if the presence of copepods influenced the morphology and/or the toxicity of thecyanobacterium. Monocultures with only N. spumigena and mixed cultures, containing N. spumigena andthe non-toxic Dunaliella tertiolecta, were included in each experiment. Following 6 days of incubation,the morphology and toxicity in grazer treatments were compared with grazer-free controls. Weobserved no effects of A. cf. bifilosa on either morphology or toxicity of N. spumigena. The lack of grazerinduced nodularin production and morphological alterations suggest that these two potential defensestrategies either has evolved as constitutive defenses or never evolved as grazer defenses. The mortalityof copepods was higher in the monoculture than in the mixed culture treatments. Gut contentobservations indicated a low level of grazing in monoculture treatments and a higher level of grazing inmixed culture treatments. This higher level of grazing most likely occurred on the alternative food D.tertiolecta. Given the indications of low grazing and the concentrations of dissolved nodularin observed,we postulate that the higher mortality was not related to toxic effects, but to starvation. This in turn mayhave resulted from bad taste, production of unknown grazer deterrents or morphological constraints;although the size of the filaments would not have imposed an absolute limit for ingestion by A. cf. bifilosa.The higher copepod mortality observed on monocultures of N. spumigena may contribute to the successand maintenance of N. spumigena blooms.
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| 39. |
- Lundgren, Veronica, et al.
(author)
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Metabolic and physiological changes in Prymnesium parvum when grown under, and grazing on prey of, variable nitrogen:phosphorus stoichiometry
- 2016
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 55, s. 1-12
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Journal article (peer-reviewed)abstract
- Mixotrophy is found in almost all classes of phytoplankton in a wide range of aquatic habitats ranging from oligotrophic to eutrophic marine and freshwater systems. Few studies have addressed how the nutritional status of the predator and/or the prey affects mixotrophic metabolism despite the realization that mixotrophy is important ecologically. Laboratory experiments were conducted to examine changes in growth rates and physiological states of the toxic haptophyte Prymnesium parvum when fed Rhodomonas sauna of varying nutritional status. Haemolytic activity of P. parvum and prey mortality of R. sauna were also measured. P. parvum cultures grown to be comparatively low in nitrogen (low-N), phosphorus (low-P) or low in both nutrients (low-NP) were mixed with low-NP, low-N, and low-P R. saline in all possible combinations, i.e., a 3 x 3 factorial design. N deficiency was obtained in the low-N cultures, while true P deficiency may not have been obtained in the low-P cultures. Mortality rates of R. salina (both due to ingestion and/or cell rupture as a function of grazing or toxic effects) were higher when R. sauna cells were low-P, N-rich, regardless of the nutritional state of P. parvum. Mortality rates were, however, directly related to the initial prey:predator cell ratios. On the other hand, growth of the predator was a function of nutritional status and a significant positive correlation was observed between growth rates of P. parvum and cell-specific depletion rates of N, whereas no such relationship was found between P. parvum growth rates and depletion rates of P. In addition, the greatest changes in chlorophyll content and stoichiometric ratios of P. parvum were observed in high N:P conditions. Therefore, P. parvum may show enhanced success under conditions of higher inorganic N:P, which are likely favored in the future due to increases in eutrophication and altered nutrient stoichiometry driven by anthropogenic nutrient loads that are increasingly enriched in N relative to P. (C) 2016 Elsevier B.V. All rights reserved.
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| 40. |
- Lundgren, Veronica, et al.
(author)
-
Prymnesium parvum invasion success into coastal bays of the Gulf of Mexico : Galveston Bay case study
- 2015
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 43, s. 31-45
-
Journal article (peer-reviewed)abstract
- The toxic haptophyte Prymnesium parvum regularly forms fish-killing blooms in inland brackish water bodies in the south-central USA. Along the Texas coast smaller blooms have occurred in isolated areas. There appears to be an increasing risk that harmful P. parvum blooms will propagate into open coastal waters with implementation of future water plans. These plans will include increased interbasin water transfers from the Brazos River, regularly impacted by P. parvum blooms, to the San Jacinto-Brazos Coastal Basin, which ultimately flows into Galveston Bay (GB). Persisting source populations of P. parvum in inland waters elevates this risk. Thus, there is a need for an increased understanding of how P. parvum might perform in coastal waters, such as those found in GB. Here, two in-field experiments were conducted to investigate the influence of various plankton size-fractions of GB water on inoculated P. parvum during fall and winter, periods when blooms are typically initiating and developing inland. Stationary- and log-growth phase P. parvum were used to represent high and low toxicity initial conditions. Results revealed that P. parvum could grow in GB waters and cause acute mortality to silverside minnows (Menidia beryllina). Depending on season and growth phase, however, P. parvum growth and toxicity varied in different size fractions. During the fall, P. parvum inoculated from stationary-, but not log-growth phase culture, was negatively affected by bacteria-sized particles. During the winter, bacteria and nanoplankton together had a negative effect on P. parvum inoculated from stationary- and, to a lesser degree, log-growth phase cultures. Intermediate- and large-sized grazers when combined with bacteria and nanoplankton had complex relationships with inoculated P. parvum, sometimes stimulating and sometimes suppressing population growth. Toxicity to fish occurred in almost all plankton size fractions. The inclusion of progressively larger sized plankton fractions resulted in trends of decreased toxicity in treatments inoculated with stationary-, but not log-growth phase P. parvum in the fall. In the winter, however, inclusion of larger sized plankton fractions resulted in trends of increased toxicity to fish in treatments inoculated with both stationary- and log-growth phase P. parvum. This study indicates that understanding P. parvum population dynamics in open waters of estuaries and bays will be challenging, as there appears to be complex relationships with naturally occurring components of the plankton. The observations that P. parvum is able to grow to high population density and produce fish-killing levels of toxins underscores the need for advanced risk assessment studies, especially in light of water use plans that will result in P. parvum invasions of greater size. (C) 2015 Elsevier B.V. All rights reserved.
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| 41. |
- Lundholm, N., et al.
(author)
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Induction of domoic acid production in diatoms-Types of grazers and diatoms are important
- 2018
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 79, s. 64-73
-
Journal article (peer-reviewed)abstract
- Grazers can induce toxin (domoic acid, DA) production in diatoms. The toxic response has been observed in two species of Pseudo-nitzschia and was induced by Calanus copepods. In this study, interactions between diatoms and copepods were further explored using different species of diatoms and copepods. All herbivorous copepods induced toxin production, whereas exposure to carnivorous copepods did not. In line with this, increasing the number of herbivorous copepods resulted in even higher toxin production. The induced response is thus only elicited by copepods that pose a real threat to the responding cells, which supports that the induced toxin production in diatoms evolved as an inducible defense. The cellular toxin content in Pseudo-nitzschia was positively correlated to the concentration of a group of specific polar lipids called copepodamides that are excreted by the copepods. This suggests that copepodamides are the chemical cues responsible for triggering the toxin production. Carnivorous copepods were found to produce less or no copepodamides. Among the diatoms exposed to grazing herbivorous copepods, only two of six species of Pseudo-nitzschia and none of the Nitzschia or Fragilariopsis strains responded by producing DA, indicating that not all Pseudo-nitzschia species/strains are able to produce DA, and that different diatom species might have different strategies for coping with grazing pressure. Growth rate was negatively correlated to cellular domoic acid content indicating an allocation cost associated with toxin production. Long-term grazing experiments showed higher mortality rates of grazers fed toxic diatoms, supporting the hypothesis that DA production is an induced defense mechanism.
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| 42. |
- McNamee, Sara E., et al.
(author)
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Distribution, occurrence and biotoxin composition of the main shellfish toxin producing microalgae within European waters : A comparison of methods of analysis
- 2016
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 55, s. 112-120
-
Journal article (peer-reviewed)abstract
- Harmful algal blooms (HABs) are a natural global phenomena emerging in severity and extent. Incidents have many economic, ecological and human health impacts. Monitoring and providing early warning of toxic HABs are critical for protecting public health. Current monitoring programmes include measuring the number of toxic phytoplankton cells in the water and biotoxin levels in shellfish tissue. As these efforts are demanding and labour intensive, methods which improve the efficiency are essential. This study compares the utilisation of a multitoxin surface plasmon resonance (multitoxin SPR) biosensor with enzyme-linked immunosorbent assay (ELISA) and analytical methods such as high performance liquid chromatography with fluorescence detection (HPLC-FLD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for toxic HAB monitoring efforts in Europe. Seawater samples (n = 256) from European waters, collected 2009-2011, were analysed for biotoxins: saxitoxin and analogues, okadaic acid and dinophysistoxins 1/2 (VDU /DTX2) and domoic acid responsible for paralytic shellfish poisoning (PSP), diarrheic shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP), respectively. Biotoxins were detected mainly in samples from Spain and Ireland. France and Norway appeared to have the lowest number of toxic samples. Both the multitoxin SPR biosensor and the RNA microarray were more sensitive at detecting toxic HABs than standard light microscopy phytoplankton monitoring. Correlations between each of the detection methods were performed with the overall agreement, based on statistical 2 x 2 comparison tables, between each testing platform ranging between 32% and 74% for all three toxin families illustrating that one individual testing method may not be an ideal solution. An efficient early warning monitoring system for the detection of toxic HABs could therefore be achieved by combining both the multitoxin SPR biosensor and RNA microarray. (C) 2016 Elsevier B.V. All rights reserved.
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| 43. |
- Meriggi, Carlotta, et al.
(author)
-
Species distribution models as a tool for early detection of the invasive Raphidiopsis raciborskii in European lakes
- 2022
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 113
-
Journal article (peer-reviewed)abstract
- In freshwater habitats, invasive species and the increase of cyanobacterial blooms have been identified as a major cause of biodiversity loss. The invasive cyanobacteria Raphidiopsis raciborskii a toxin-producing and bloom-forming species affecting local biodiversity and ecosystem services is currently expanding its range across Europe. We used species distribution models (SDMs) and regional bioclimatic environmental variables, such as temperature and precipitation, to identify suitable areas for the colonization and survival of R. raciborskii, with special focus on the geographic extent of potential habitats in Northern Europe. SDMs predictions uncovered areas of high occurrence probability of R. raciborskii in locations where it has not been recorded yet, e.g. some areas in Central and Northern Europe. In the southeastern part of Sweden, areas of suitable climate for R. raciborskii corresponded with lakes of high concentrations of total phosphorus, increasing the risk of the species to thrive. To our knowledge, this is the first attempt to predict areas at high risk of R. raciborskii colonization in Europe. The results from this study suggest several areas across Europe that would need monitoring programs to determine if the species is present or not, to be able to prevent its potential colonization and population growth. Regarding an undesirable microorganism like R. raciborskii, authorities may need to start information campaigns to avoid or minimize the spread.
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| 44. |
- Nunan, Naoise
(author)
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The phyto-bacterioplankton couple in a shallow freshwater ecosystem: Who leads the dance?
- 2023
-
In: Harmful Algae. - 1568-9883 .- 1878-1470. ; 126
-
Journal article (peer-reviewed)abstract
- Bloom-forming phytoplankton dynamics are still unpredictable, even though it is known that several abiotic factors, such as nutrient availability and temperature, are key factors for bloom development. We investigated whether biotic factors, i.e. the bacterioplankton composition (via 16SrDNA metabarcoding), were correlated with phytoplankton dynamics, through a weekly monitoring of a shallow lake known to host recurrent cyanobacterial blooms. We detected concomitant changes in both bacterial and phytoplankton community biomass and diversity. During the bloom event, a significant decrease in phytoplankton diversity, was detected, with a first co-dominance of Ceratium, Microcystis and Aphanizomenon, followed by a co-dominance of the two cyanobacterial genera. In the same time, we observed a decrease of the particle-associated (PA) bacterial richness and the emergence of a specific bacterial consortium that was potentially better adapted to the new nutritional niche. Unexpectedly, changes in PA bacterial communities occurred just before the development the emergence of the phytoplanktonic bloom and the associated modification of the phytoplanktonic community composition, suggesting that changes in environmental conditions leading to the bloom, were first sensed by the bacterial PA community. This last was quite stable throughout the bloom event, even though there were changes in the blooming species, suggesting that the association between cyanobacterial species and bacterial communities may not be as tight as previously described for monospecific blooming communities. Finally, the dynamics of the freeliving (FL) bacterial communities displayed a different trajectory from those of the PA and phytoplankton communities. This FL communities can be viewed as a reservoir for bacterial recruitment for the PA fraction. Altogether, these data also highlight s that the spatial organization within these different microenvironments in the water column is a relevant factor in the structuring of these communities.
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| 45. |
- Olofsson, Malin
(author)
-
A suggested climate service for cyanobacteria blooms in the Baltic Sea – Comparing three monitoring methods
- 2022
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470.
-
Journal article (peer-reviewed)abstract
- Dense blooms of filamentous cyanobacteria are recurrent phenomena in the Baltic Sea, with occasional negative effects on the surrounding ecosystem, as well as on tourism, human health, aquaculture, and fisheries. Establishing a climate service is therefore suggested; including multi-method observations of cyanobacteria biomass, biodiversity, and biogeography, in correspondence to biotic and abiotic factors. Three different approaches were compared for determination of spatial and temporal variability and trends of the blooms; 1) microscopy-based long-term data, 2) satellite remote sensing, and 3) phycocyanin fluorescence mounted on a merchant vessel. Firstly, microscopy-based data on cyanobacteria biomass from the period 2000–2020 showed that the toxin producing genus Nodularia and non-toxic Aphanizomenon both had summer means of 15 µg C L⁻¹, while Dolichospermum was less dominant with a mean of 8 µg C L⁻¹. Some years also the Kattegat was affected by cyanobacteria blooms, likely transported here by ocean currents. Secondly, the satellite remote sensing time series for the period 2002–2020 indicated that near surface blooms were most frequent in the Northern Baltic Proper and that near surface blooms have increased in the Bothnian Sea, starting later in the season than in the Baltic Proper. The largest extents (i.e., total area covered) were observed in 2005, 2008, and 2018. Thirdly, phycocyanin fluorescence from a flow through sensor mounted on a merchant vessel was used as a proxy for cyanobacteria biomass and correlated to cyanobacteria biomass estimated by microscopy. However, the satellite remote sensing data on surface accumulations showed little resemblance to the data on cyanobacteria biomass based on water sampling and microscopy, interpreted as an effect of methods. Sensors on satellites mainly detect surface accumulations of cyanobacteria while the microscopy data was based on samples 0–10 m, thereby comprising a larger community. Data from satellite remote sensing of cyanobacteria was correlated to the phycocyanin fluorescence indicating that similar bio-optical properties are observed. Finally, results from a downscaled ocean climate model (NEMONordic) were used to produce future scenarios for temperature and salinity, which directly affects cyanobacteria blooms in the Baltic Sea, supposedly by increasing in abundance and change in species composition. Short-term forecasts can be used together with observations for early warning of cyanobacteria blooms, and we suggest an internationally coordinated cyanobacteria observation and warning system for the Baltic Sea area.
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| 46. |
- Pattanaik, Bagmi, 1977, et al.
(author)
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Production of the cyanotoxin nodularin-A multifactorial approach
- 2010
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 10:1, s. 30-38
-
Journal article (peer-reviewed)abstract
- Summer blooms in the Baltic Sea are dominated by the diazotrophic cyanobacteria Nodularia spumigena and Aphanizomenon sp. During the blooms, N. spumigena is concentrated to the water surface and exposed to high irradiances of both photosynthetic active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400 nm), in addition, this organism is exposed to seasonal changes in nutrient conditions. N. spumigena produces nodularin, a hepatotoxin lethal to wild and domestic animals. It has been suggested that the accumulation of nodularin within the cell and the release from the cell are affected by different environmental factors. One laboratory experiment and two outdoor experiments were performed to investigate the interaction of two radiation treatments, PAR and PAR + UV-A + UV-B (PAB); three nutrient treatments, nutrient replete (NP), nitrogen limited (-N), and phosphorus limited (-P) and the presence and absence of Aphanizomenon sp. on intracellular as well as extracellular nodularin concentration in N. spumigena. In this study, we hypothesised that the interaction of ambient radiation, nutrient limitation, and the presence or absence of Aphanizomenon sp. would affect the accumulation and release of nodularin. We further hypothesised that the presence of Aphanizomenon sp. would increase the production and release of nodularin and that this increase would have a negative effect on the specific growth rate of this co-existing species. Significant interaction effects were found between the factors investigated. In all three experiments, the lowest intracellular nodularin concentrations were found under phosphorus limitation. The highest intra- and extracellular nodularin concentrations were observed under nitrogen limitation when shielded from UVR. In our opinion, further increase of nitrogen removal in e.g. sewage treatment, should consider a possible increased toxicity of the N. spumigena blooms. The presence of N. spumigena had no significant effect on the specific growth rate of Aphanizomenon sp. under different radiation and nutrient treatments. Thus, we conclude that although nodularin accumulation and release were dependent on different environmental conditions, it did not affect the co-existing species Aphanizomenon sp. (C) 2010 Elsevier B.V. All rights reserved.
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| 47. |
- Pérez Blanco, Eva, et al.
(author)
-
Detection of Heterosigma akashiwo (Hada) using specific RNA probes : Variability of RNA content with environmental conditions
- 2013
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 24, s. 80-88
-
Journal article (peer-reviewed)abstract
- The raphidophyte Heterosigma akashiwo, which forms toxic blooms, causes major economical losses to the fish industry because of the fish kills involved. It is therefore important to be able to detect not only H. akashiwo but other toxic phytoplankton species as well, rapidly and accurately to reduce losses by fish kills. With this purpose, DNA sequences from H. akashiwo 18S and 28S rRNA gene regions were studied in silico to design species-specific probes to be used in a microarray format. Three strains of H. akashiwo (AC 265, AC 266 and GUMACC 120) were grown at optimal conditions and transferred into new environmental conditions changing either the light intensity, salinity, temperature or nutrient concentrations, to check if any of these environmental conditions induced changes in the cellular RNA concentration. The aim of this experiment was the calibration of several species-specific probes for the quantification of H. akashiwo. Differences on RNA content were not significant (p < 0.05) in any of the treatments, therefore the calibration curves were validated. The designed probes are reliable for the detection and quantification of H. akashiwo cells in natural waters. (C) 2013 Elsevier B.V. All rights reserved.
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| 48. |
- Pérez Blanco, Eva, et al.
(author)
-
Population dynamics of dominant dinoflagellate species in the North Sea : in situ growth rates, photosynthetic potential, and losses due to parasitism
- 2024
-
In: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 134
-
Journal article (peer-reviewed)abstract
- In the North Sea, Tripos and Dinophysis are commonly occurring mixotrophic planktonic dinoflagellate genera. In order to understand their bloom dynamics, an occurring bloom dominated by T. furca and D. norvegica was followed for several days. High cell abundances of these species were located to estimate: in situ growth rates from cell cycle analyses, depth distributions, growth rates sustained by photosynthesis, and parasite infection prevalence in all T. furca, T. fusus, D. norvegica and D. acuminata. Cell abundances were over 10000 cells L−1 for T. furca and up to 18000 cells L−1 for D. norvegica. Cells accumulated between 15-25 m depth and presented low specific in situ growth rates of 0.04-0.15 d−1 for T. furca and 0.02-0.16 d−1 for D. norvegica. Photosynthesis could sustain growth rates of 0.01-0.18 d−1 for T. furca and 0.02 to 0.14 d−1 for D. norvegica, suggesting that these species were relying mainly on photosynthesis. Parasite infections where generally low, with occasional high prevalence in D. norvegica (by Parvilucifera sp.) and T. fusus (by Amoebophrya sp.), while both parasites showed comparable prevalence in D. acuminata, which could offset in situ growth rates by parasite-induced host mortality. The restructuring effect of parasites on dinoflagellate blooms is often overlooked and this study elucidates their effect to cell abundances and their growth at the final stages of a bloom.
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| 49. |
- Persson, Agneta, 1963, et al.
(author)
-
Differences in swimming pattern between life cycle stages of the toxic dinoflagellate Alexandrium fundyense
- 2013
-
In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 21-22, s. 36-43
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Journal article (peer-reviewed)abstract
- Different life stages of Alexandrium fundyense have different swimming behavior; gametes often are said to "swarm" or "dance" before mating. This behavior was studied, and quantitative measures of these motility patterns in two-dimensions were generated using motion-analysis software applied to video records of individual-cell movements. Behavior, swimming patterns, and growth were studied in two strains of A. fundyense and compared in encystment medium and growth medium. Vegetative cells swam straight, rotating around the apical axis until they hit something and then swam straight in a different direction. Gamete swimming behavior was slower and characterized by frequent direction changes and circular motion. Gametes contacted other cells frequently (>5 cell contacts min(-1) cell(-1)). Zygotes swam slowly when newly formed and later became nearly immobile; these cells continued to contact other cells and also surfaces. The results are in accordance with field observations of long swimming distances for vegetative cells, accumulation in thin layers of gametes, and sinking of developing resting cysts attached to marine snow for zygotes. (C) 2012 Elsevier B.V. All rights reserved.
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| 50. |
- Persson, Agneta, 1963, et al.
(author)
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Dinoflagellate gamete formation and environmental cues: Observations, theory, and synthesis
- 2008
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In: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 7:6, s. 798-801
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Journal article (peer-reviewed)abstract
- For some species of cyst-producing dinoflagellates, the sexual life cycle is well studied in laboratory cultures. Dinoflagellate blooms in stratified waters, vertical migration of vegetative cells, and the accumulation of populations within thin layers are well-documented phenomena in nature. We propose a conceptual model that places these phenomena in a functional, ecological context: vegetative cells of a dinoflagellate population display vertical migration, but at the end of the bloom, environmental or internal cues shift the cell cycle to gamete formation. Then the vertical migrations cease, and cells accumulate in a layer at the pycnocline where gametes fuse to form zygotes, which then sink to the sediment as resting cysts. We support this conceptual model with experimental and environmental evidence. (C) 2008 Elsevier B.V. All rights reserved.
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