| 1. |
- Godhe, Anna, et al.
(författare)
-
PCR amplification of microalgal DNA for sequencing and species identification : studies on fixatives and algal growth stages
- 2002
-
Ingår i: Harmful Algae. - 1568-9883 .- 1878-1470. ; 1:4, s. 375-382
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Godhe, Anna, et al.
(författare)
-
PCR detection of dinoflagellate cysts in field sediment samples from tropic and temperate environments
- 2002
-
Ingår i: Harmful Algae. - 1568-9883 .- 1878-1470. ; 1:4, s. 361-373
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 3. |
- Godhe, Anna, et al.
(författare)
-
PCR detection of dinoflagellate cysts in field sediment samples from tropic and temperate environments
- 2002
-
Ingår i: Harmful Algae. - : Elsevier. - 1568-9883. ; 1:4, s. 361-373
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Aguilera, Anabella, et al.
(författare)
-
Cyanobacterial bloom monitoring and assessment in Latin America
- 2023
-
Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 125
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Angeler, David, et al.
(författare)
-
Algal invasions, blooms and biodiversity in lakes: Accounting for habitat-specific responses
- 2013
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 23, s. 60-69
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Bonilla, Sylvia, et al.
(författare)
-
Nutrients and not temperature are the key drivers for cyanobacterial biomass in the Americas
- 2023
-
Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 121
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- Bravo, I, et al.
(författare)
-
Alexandrium catenella and Alexandrium minutum blooms in the Mediterranean Sea: Toward the identification of ecological niches
- 2008
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 7:4, s. 515-522
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Bravo, Isabel, et al.
(författare)
-
Cellular and nuclear morphological variability within a single species of the toxigenic dinoflagellate genus Gambierdiscus: Relationship to life-cycle processes
- 2014
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 40, s. 1-8
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 9. |
- Brutemark, Andreas, et al.
(författare)
-
Role of mixotrophy and light for growth and survival of the toxic haptophyte Prymnesium parvum
- 2011
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 10, s. 388-394
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 10. |
- Burford, M. A., et al.
(författare)
-
Perspective: Advancing the research agenda for improving understanding of cyanobacteria in a future of global change
- 2020
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 91
-
Tidskriftsartikel (refereegranskat)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
|
|
| 11. |
- Carlsson, Per, et al.
(författare)
-
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
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 86, s. 74-83
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 12. |
- Carvalho, Wanderson, et al.
(författare)
-
Dinophysis norvegica (Dinophyceae), more a predator than a producer?
- 2008
-
Ingår i: Harmful Algae. - : Elsevier B.V. - 1568-9883 .- 1878-1470. ; 7:2, s. 174-183
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 13. |
- Diaz, Patricio A., et al.
(författare)
-
Coupling planktonic and benthic shifts during a bloom of Alexandrium catenella in southern Chile: Implications for bloom dynamics and recurrence
- 2014
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 40, s. 9-22
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 14. |
- F de Carvalho, Wanderson, et al.
(författare)
-
Contribution of phagotrophy versus autotrophy to Prymnesium parvum growth under nitrogen and phosphorus sufficiency and deficiency
- 2010
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 9, s. 105-115
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 15. |
- Fagerberg, Tony, et al.
(författare)
-
A large molecular size fraction of riverine high molecular weight dissolved organic matter (HMW DOM) stimulates growth of the harmful dinoflagellate Alexandrium minutum
- 2009
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8:6, s. 823-831
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 16. |
- Figueroa, Rosa Isabel, et al.
(författare)
-
Life histories of microalgal species causing harmful blooms : Haploids, diploids and the relevance of benthic stages
- 2018
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 73, s. 44-57
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 17. |
- Gao, Yida, et al.
(författare)
-
Spatiotemporal genetic structure of regional-scale Alexandrium catenella dinoflagellate blooms explained by extensive dispersal and environmental selection
- 2019
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 86, s. 46-54
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 18. |
- Ger, Kemal Ali, et al.
(författare)
-
The interaction between cyanobacteria and zooplankton in a more eutrophic world
- 2016
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 54, s. 128-144
-
Forskningsöversikt (refereegranskat)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.
|
|
| 19. |
|
|
| 20. |
- Godhe, Anna, 1967, et al.
(författare)
-
Intercalibration of classical and molecular techniques for identification of Alexandrium fundyense (Dinophyceae) and estimation of cell densities
- 2007
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 6:1, s. 56-72
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 21. |
- Gorokhova, Elena
(författare)
-
Toxic cyanobacteria Nodularia spumigena in the diet of Baltic mysids : Evidence from molecular diet analysis
- 2009
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 8:2, s. 264-272
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 22. |
- Granéli, Edna, et al.
(författare)
-
Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
- 2011
-
Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 10:2, s. 165-172
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 23. |
|
|
| 24. |
- Granéli, Edna, et al.
(författare)
-
The ecophysiology and bloom dynamics of Prymnesium spp.
- 2012
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 14:SI, s. 260-270
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 25. |
- Gustafsson, Susanne, et al.
(författare)
-
On the control of HAB species using low biosurfactant concentrations
- 2009
-
Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8, s. 857-863
-
Tidskriftsartikel (refereegranskat)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.
|
|
