Edna Graneli | Linnaeus University (original) (raw)
Papers by Edna Graneli
JAWRA Journal of the American Water Resources Association, 2010
Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allel... more Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin ⁄ allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins ⁄ allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to Nstarved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.
Toxicon, 2006
Accumulation of Nodularia spumigena toxins by Mytilus edulis was studied during laboratory and me... more Accumulation of Nodularia spumigena toxins by Mytilus edulis was studied during laboratory and mesocosm experiments in order to investigate the possible pathways of nodularin in mussels and calculate toxin budgets. Mussels were exposed to 0.2-15.6 mg nodularin l À1 , fed for up to 5 days with Nodularia cells from culture, or blooming in different nutrient-treated seawater. Toxin concentration was monitored with LC-ESI-MS.
Marine Ecology-progress Series, 2002
Interactions between the ctenophore Pleurobrachia pileus, copepods, ciliates and phytoplankton in... more Interactions between the ctenophore Pleurobrachia pileus, copepods, ciliates and phytoplankton in a late spring natural plankton community were studied experimentally using mesocosms consisting of 300 l polyethene cylinders. Mesocosms were filled with 90 µm filtered nutrient-enriched seawater from Gullmar Fjord on the Swedish Skagerrak coast. Mesozooplankton (primarily copepods and marine cladocerans) or ctenophores were added, either alone or in combination, to examine topdown predation and grazing effects on phytoplankton abundance and composition. Predation impact of ctenophores on copepods appeared to be minimal in that it did not significantly decrease the biomass of the copepods until the last day of the experiment. However, in the presence of ctenophores, ciliates increased compared to controls both with and without added zooplankton, suggesting that ctenophore predation on copepods reduced copepod predation on ciliates. In the absence of ctenophores, ciliates declined precipitously, presumably due to copepod predation. This was particularly severe in treatments with zooplankton added at 10 × the natural abundance but without ctenophores. Copepods heavily grazed on the diatom Skeletonema costatum, and most phytoflagellates increased in mesocosms with copepod additions, suggesting that they were not substantially grazed by copepods. However, copepods did graze to some extent on larger dinoflagellates of the genus Gymnodinium/Karenia. Ciliates were important phytoplankton grazers, especially of phytoflagellates and picoplankton. It appears that the primary top-down effect of ctenophore predation on copepods was to reduce copepod predation on ciliates, thereby increasing ciliate grazing on the small flagellates that dominated the phytoplankton.
Strong evidence has accumulated on the last years that some algal species are able to kill not o... more Strong evidence has accumulated on the last years that some algal species are able to kill not only their grazers but also other algal species, a process called allelopathy. Killing the nutrient-competing phytoplankton species enable these species to freely utilize limiting resources such as nitrogen and phosphorus. While for some algal species like e.g. the flagellate Pryntnesium sp., the allelochemicals seem to be the same substances as their toxins, for some other algal species they are not. Alexandrium spp. are among the latter case: their internal toxins (such as saxitoxins) are not able to inhibit the growth of other algal species. However, these species by producing other substances than their internal toxins also cause allelopathic effects. Emphasis is placed here on the flagellate species Prymnesium parvum: which is not only able of allelopathy but mixotrophy as well. Mixotrophy, i.e. the capability to ingest bacteria, other algae and even potential grazers, also contributes to the bloom-forming ability of Prytnnesium spp. Allelopathy, mixotrophy and grazer deterrence increase dramatically when Prymnesium spp. cells are grown under N or P deficiency, and so does toxicity, but decrease in intensity or cease completely if cells are grown with high amounts of N and P in balanced proportions. Prymnesium filtrates from nutrient deficient cultures have almost the same strong effect on grazers and other plankton cells as Pryntnesium cells grown together with their target. It seems that toxin production in Pryrnnesium spp. works not only as a defense mechanism, but also, by killing competitors, improve the alga competitive ability under conditions of severe nutrient depletion. We can assume thus that a consequence of the increased input of N and P to aquatic ecosystems is provoking an unbalanced nutrient situation for Prymnesium spp., as well as many of the other HAB species producing toxins, to growth but ideal to produce toxins instead.
Ecological Studies, 2006
... 1993; Jeong et al. 2005a),Alexandrium ostenfeldii and A. tamarense (Jacobson and Anderson 199... more ... 1993; Jeong et al. 2005a),Alexandrium ostenfeldii and A. tamarense (Jacobson and Anderson 1996; Jeong et al. 2005a), Ceratium furca (Smalley et al. ... Species Evidence for Phagotrophya References Alexandrium ostenfeldii Obs. of food vacuoles with electron microscopy ...
Journal of Plankton Research, 1991
ABSTRACT
Limnology and …, 2001
... Toxicity can be greatly affected by the growth phase and stress conditions of the alga (ie, l... more ... Toxicity can be greatly affected by the growth phase and stress conditions of the alga (ie, light, salinity, nutrients; Edvardsen and Paasche ... Most attention has been directed to-ward the physiology of these mixotrophs (ie, the influence of biotic/abiotic factors on their heterotrophic ...
Toxicon, 2001
The brackish water cyanobacterium Nodularia spumigena produce the hepatotoxic cyclic pentapeptide... more The brackish water cyanobacterium Nodularia spumigena produce the hepatotoxic cyclic pentapeptide nodularin. Intoxications for both human as well as animal may arise when water reservoirs are contaminated with potentially toxic Nodularia species. Here, results of three independent methods for the determination of nodularin in different strains of N. spumigena are presented. The results obtained with a protein phosphatase assay and a HPLC/UV/MS method are compared with the results obtained with a bioluminescence assay, which is successfully introduced here for nodularin determination. Statistical evaluation of the three applied methods revealed a good comparability towards the detected toxin content. The methods were evaluated taking into consideration the parameters: handling, ef®ciency, sensitivity and selectivity. The detection limit in the protein phosphatase assay is highest (0.05 ng nodularin) and lowest (250 ng nodularin) in the bioluminescence assayÐ it was determined with 5 ng (MS) and 25 ng (UV) for the HPLC/UV/MS methods. The different selectivities and sensitivities are critically discussed and an analytical pathway for the determination of the biotoxin nodularin from Nodularia samples is proposed. q
Parasitology Research, 2000
Parasitism within the group of dinoflagellates is a widespread phenomenon. Whether the parasitic ... more Parasitism within the group of dinoflagellates is a widespread phenomenon. Whether the parasitic dinoflagellates exhibit specificity in their infection is not well known, but this possibility has become an important issue in the development of biological control of harmful algal blooms. The 18S rDNA sequences from the parasite Amoebophrya sp. and its dinoflagellate host Dinophysis norvegica were determined and compared with the published sequence of Amoebophrya sp. infecting Gymnodinium sanguineum and other dinoflagellates. The results showed that the sequence from the parasite within D. norvegica was clustered with that of the one from G. sanguineum with 100% bootstrap support in a maximum-likelihood analysis. The observed identity between these two sequences was 93%, which indicates that they are not identical species. The two sequences from Amoebophrya sp. were deeply branched within the group of dinoflagellate sequences and represent the earliest diverging dinoflagellates. The sequence from the parasite Parvilucifera infectans, also infecting D. norvegica, was not closely related to the Amoebophrya sp. sequences. The sequence from D. norvegica appeared as a sister group to a cluster containing Prorocentrum lima and Alexandrium spp. without significant bootstrap support. The data presented herein support the hypothesis that A. ceratii comprises more than one species, and this opens the possibility that infections of harmful algal species might involve more than one Amoebophrya species.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999
The occurrence of annual marine phytoplankton blooms is becoming a global problem. In Europe, the... more The occurrence of annual marine phytoplankton blooms is becoming a global problem. In Europe, the NUTOX project supported by the EC investigates if unbalanced nutrient compositions in the water promote the dominance of harmful phytoplankton species. One of the tasks is the determination of the elemental composition of single phytoplankton cells. This is carried out using the Lund Nuclear Microprobe with a special focus on C, N, P and K. The overall aim is to understand the mechanism leading to toxin production, model it and eventually propose a counteracting method. The preparative method, used to isolate single living cells while reducing their salt environment, is an important part of the analytical procedure. A comparison of light element detection using backscattering from protons and nuclear reaction analysis using deuterons is made. Ó 0168-583X/99/$ -see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 9 ) 0 0 3 7 2 -9
Marine Pollution Bulletin, 2008
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversi... more The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.
Marine Ecology Progress Series, 2005
... 1996, Schramm & Nienhuis 1996, Johansson et al. 1998, Eriksson et al. 2002), incl... more ... 1996, Schramm & Nienhuis 1996, Johansson et al. 1998, Eriksson et al. 2002), including the Baltic Sea (Hällfors et al. 1984, Cederwall & Elmgren 1990, Eriksson et al. 1998, Rönnberg & Mathiesen 1998, Lotze et al. 1999, Vahteri et al. 2000). ...
Marine Ecology Progress Series, 2003
The allelopathic effect of Prymnesium parvum (Prymnesiophyta), which produces toxins with haemoly... more The allelopathic effect of Prymnesium parvum (Prymnesiophyta), which produces toxins with haemolytic, ichthyotoxic and cytotoxic properties, was investigated on a natural plankton community. Under controlled conditions, 3 laboratory bioassays were performed by adding cell-free filtrate from a P. parvum culture into different size fractions (<150, <100 and 20 to 150 µm) of a natural Baltic Sea plankton community. The effect of P. parvum cell-free filtrate was determined by measuring chlorophyll a, cell numbers (phytoplankton, ciliates, bacteria), carbon ( 14 C) uptake by phytoplankton and the incorporation of 3 H-leucine by bacteria. P. parvum cell-free filtrate affected the whole phytoplankton community, resulting in a decrease in both chlorophyll a and carbon uptake. Furthermore, the plankton groups present in the community exhibited different sensitivity to the cellfree filtrate. While growth of cyanobacteria and dinoflagellates was inhibited, that of diatoms and ciliates was not only completely suppressed, but no cells were present at the end of the experiment in the bottles with P. parvum filtrate. In all experiments, therefore, cyanobacteria and dinoflagellates were the most resistant groups, which led to their dominance in the treatments with filtrate compared to controls. Bacterial production was also negatively affected by P. parvum filtrate. The results show that compounds released by P. parvum induce changes in the plankton community structure, killing other members of the marine food-web, especially other phytoplankton (allelopathy), and suggest that secreted compounds of P. parvum are inhibitory to potential grazers (ciliates). It is proposed that allelopathy is an important process in the ecology of P. parvum.
Marine Ecology Progress Series, 2007
Summer N 2 -fixing cyanobacterial blooms are a common feature in the Baltic Sea, and the occurren... more Summer N 2 -fixing cyanobacterial blooms are a common feature in the Baltic Sea, and the occurrence of Nodularia spumigena toxic blooms is of particular concern. Cyanobacterial blooms can be favoured by certain conditions including high concentrations of dissolved organic matter, which may increase the availability of iron critical for N 2 fixation. Cyanobacteria may negatively affect grazers because many species produce toxins and generally lack fatty acids essential for zooplankton reproduction. In this study we investigated the effect of riverine high-molecular weight dissolved organic matter (DOM-)/iron-stimulated cyanobacteria on the development of proto-and metazooplankton, and evaluated the role of DOM in stimulating the zooplankton part of the microbial food web. A plankton community was incubated in cylinders with either nitrate (NO 3 ) or DOM alone or combined with iron (Fe) or zooplankton >100 µm (G). The development of proto-and metazooplankton was followed for 10 d. Trophic relationships between metazooplankton taxa and their potential food items were assessed by ordination analysis and by feeding and reproduction bottle incubations with the calanoid copepod Acartia bifilosa. Contrary to our expectations, DOM did not stimulate the microbial food web, and proto-and metazooplankton developed similarly in all treatments until the middle of the experiment. However, by the end of the experiment, the biomass of proto-and metazooplankton as well as the biomass of diatoms and dinoflagellates was greatly depressed in all DOM and NO 3 Fe treatments. In these treatments, cyanobacterial and bacterial biomasses were highest leading up to phosphate depletion. Plankton development seemed to be bottom-up controlled and to be affected by extracellular compound(s) produced by the dominant cyanobacteria, possibly triggered by phosphate limitation. Diatoms, dinoflagellates, protozoans and metazooplankton were instead stimulated in the NO 3 and NO 3 G treatments, where cyanobacterial biomass was low. Accordingly, A. bifilosa reproduction and survival were sustained in NO 3 bottles. Deleterious effects of cyanobacteria on metazooplankton were diminished in NO 3 and NO 3 G tanks where other food resources were available. Overall, the results suggest that increases in the input of DOM to the Baltic Sea can potentially stimulate cyanobacterial blooms that may disrupt the microbial food web and inhibit metazooplankton development.
Marine Ecology Progress Series, 1993
The effects of additions of river isolated hurnic compounds on biomass formation and primary prod... more The effects of additions of river isolated hurnic compounds on biomass formation and primary production of a natural phytoplankton community were compared with the effects of additions of nitrate or phosphate in a batch culture experiment lasting for 10 d during late summer. Mesozooplankton (> 150 pm) were excluded in the experiment, but micrograzers such as heterotrophic nanoflagellates, ciliates and copepod nauplii were present. The humic substances were isolated from river water using a macroporous resin (XAD-8). Trace metals, iron and vitamins were added in order to avoid growth limitation caused by these compounds. Phytoplankton biomass and primary production became significantly higher in treatments where nitrate or humic substances were added than in control flasks. Bacterial numbers became significantly higher in the treatments where humic substances were added compared with controls. Ammonium concentrations became elevated in the treatments where nitrate or hurnic substances were added. It seems likely that humic substances were utilized by bacteria both as a carbon and a nitrogen source and that nitrogen was incorporated in bacteria and later regenerated as inorganic nitrogen due to the activity of bacterial grazers and other grazers of higher trophic levels. We suggest that this is the mechanism by which nitrogen in hurnic substances becomes available for coastal phytoplankton communities.
Marine Ecology Progress Series, 1995
... 1988) or amino acids (Flynn & Butler 1986). Inorganic nitrogen sources include nitrite or... more ... 1988) or amino acids (Flynn & Butler 1986). Inorganic nitrogen sources include nitrite or nitrate produced by bacterial miner-alization (Tupas & Koike 1990) and ammonia produced by excretion by grazers (Bbmstedt 1985, Probyn 1987, Caron & Goldman 1990). ...
Marine Ecology Progress Series, 2003
We studied the growth and feeding response of the ciliate Euplotes affinis when exposed to algal ... more We studied the growth and feeding response of the ciliate Euplotes affinis when exposed to algal cultures of Prymnesium parvum and Rhodomonas cf. baltica as monocultures or as mixtures. Cultures of P. parvum grown under nutrient-limited (N or P) or nutrient-sufficient conditions were tested for toxicity against E. affinis. Ciliates grew well when fed R. cf. baltica, but avoided grazing on monocultures of P. parvum, regardless of algal concentration. Increasing abundances of P. parvum decreased survival of the ciliate, even if supplied as a mixture together with high concentrations of R. cf. baltica as an alternative prey. This implies that P. parvum produces substances that were fatal to the ciliate when released to the medium. The lethal effect of P. parvum was dependent on the physiological status of the cells, with the highest toxicity in nutrient-stressed cultures. Our results suggest that toxin production in P. parvum may be a chemical defense to repel predators.
JAWRA Journal of the American Water Resources Association, 2010
Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allel... more Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin ⁄ allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins ⁄ allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to Nstarved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.
Toxicon, 2006
Accumulation of Nodularia spumigena toxins by Mytilus edulis was studied during laboratory and me... more Accumulation of Nodularia spumigena toxins by Mytilus edulis was studied during laboratory and mesocosm experiments in order to investigate the possible pathways of nodularin in mussels and calculate toxin budgets. Mussels were exposed to 0.2-15.6 mg nodularin l À1 , fed for up to 5 days with Nodularia cells from culture, or blooming in different nutrient-treated seawater. Toxin concentration was monitored with LC-ESI-MS.
Marine Ecology-progress Series, 2002
Interactions between the ctenophore Pleurobrachia pileus, copepods, ciliates and phytoplankton in... more Interactions between the ctenophore Pleurobrachia pileus, copepods, ciliates and phytoplankton in a late spring natural plankton community were studied experimentally using mesocosms consisting of 300 l polyethene cylinders. Mesocosms were filled with 90 µm filtered nutrient-enriched seawater from Gullmar Fjord on the Swedish Skagerrak coast. Mesozooplankton (primarily copepods and marine cladocerans) or ctenophores were added, either alone or in combination, to examine topdown predation and grazing effects on phytoplankton abundance and composition. Predation impact of ctenophores on copepods appeared to be minimal in that it did not significantly decrease the biomass of the copepods until the last day of the experiment. However, in the presence of ctenophores, ciliates increased compared to controls both with and without added zooplankton, suggesting that ctenophore predation on copepods reduced copepod predation on ciliates. In the absence of ctenophores, ciliates declined precipitously, presumably due to copepod predation. This was particularly severe in treatments with zooplankton added at 10 × the natural abundance but without ctenophores. Copepods heavily grazed on the diatom Skeletonema costatum, and most phytoflagellates increased in mesocosms with copepod additions, suggesting that they were not substantially grazed by copepods. However, copepods did graze to some extent on larger dinoflagellates of the genus Gymnodinium/Karenia. Ciliates were important phytoplankton grazers, especially of phytoflagellates and picoplankton. It appears that the primary top-down effect of ctenophore predation on copepods was to reduce copepod predation on ciliates, thereby increasing ciliate grazing on the small flagellates that dominated the phytoplankton.
Strong evidence has accumulated on the last years that some algal species are able to kill not o... more Strong evidence has accumulated on the last years that some algal species are able to kill not only their grazers but also other algal species, a process called allelopathy. Killing the nutrient-competing phytoplankton species enable these species to freely utilize limiting resources such as nitrogen and phosphorus. While for some algal species like e.g. the flagellate Pryntnesium sp., the allelochemicals seem to be the same substances as their toxins, for some other algal species they are not. Alexandrium spp. are among the latter case: their internal toxins (such as saxitoxins) are not able to inhibit the growth of other algal species. However, these species by producing other substances than their internal toxins also cause allelopathic effects. Emphasis is placed here on the flagellate species Prymnesium parvum: which is not only able of allelopathy but mixotrophy as well. Mixotrophy, i.e. the capability to ingest bacteria, other algae and even potential grazers, also contributes to the bloom-forming ability of Prytnnesium spp. Allelopathy, mixotrophy and grazer deterrence increase dramatically when Prymnesium spp. cells are grown under N or P deficiency, and so does toxicity, but decrease in intensity or cease completely if cells are grown with high amounts of N and P in balanced proportions. Prymnesium filtrates from nutrient deficient cultures have almost the same strong effect on grazers and other plankton cells as Pryntnesium cells grown together with their target. It seems that toxin production in Pryrnnesium spp. works not only as a defense mechanism, but also, by killing competitors, improve the alga competitive ability under conditions of severe nutrient depletion. We can assume thus that a consequence of the increased input of N and P to aquatic ecosystems is provoking an unbalanced nutrient situation for Prymnesium spp., as well as many of the other HAB species producing toxins, to growth but ideal to produce toxins instead.
Ecological Studies, 2006
... 1993; Jeong et al. 2005a),Alexandrium ostenfeldii and A. tamarense (Jacobson and Anderson 199... more ... 1993; Jeong et al. 2005a),Alexandrium ostenfeldii and A. tamarense (Jacobson and Anderson 1996; Jeong et al. 2005a), Ceratium furca (Smalley et al. ... Species Evidence for Phagotrophya References Alexandrium ostenfeldii Obs. of food vacuoles with electron microscopy ...
Journal of Plankton Research, 1991
ABSTRACT
Limnology and …, 2001
... Toxicity can be greatly affected by the growth phase and stress conditions of the alga (ie, l... more ... Toxicity can be greatly affected by the growth phase and stress conditions of the alga (ie, light, salinity, nutrients; Edvardsen and Paasche ... Most attention has been directed to-ward the physiology of these mixotrophs (ie, the influence of biotic/abiotic factors on their heterotrophic ...
Toxicon, 2001
The brackish water cyanobacterium Nodularia spumigena produce the hepatotoxic cyclic pentapeptide... more The brackish water cyanobacterium Nodularia spumigena produce the hepatotoxic cyclic pentapeptide nodularin. Intoxications for both human as well as animal may arise when water reservoirs are contaminated with potentially toxic Nodularia species. Here, results of three independent methods for the determination of nodularin in different strains of N. spumigena are presented. The results obtained with a protein phosphatase assay and a HPLC/UV/MS method are compared with the results obtained with a bioluminescence assay, which is successfully introduced here for nodularin determination. Statistical evaluation of the three applied methods revealed a good comparability towards the detected toxin content. The methods were evaluated taking into consideration the parameters: handling, ef®ciency, sensitivity and selectivity. The detection limit in the protein phosphatase assay is highest (0.05 ng nodularin) and lowest (250 ng nodularin) in the bioluminescence assayÐ it was determined with 5 ng (MS) and 25 ng (UV) for the HPLC/UV/MS methods. The different selectivities and sensitivities are critically discussed and an analytical pathway for the determination of the biotoxin nodularin from Nodularia samples is proposed. q
Parasitology Research, 2000
Parasitism within the group of dinoflagellates is a widespread phenomenon. Whether the parasitic ... more Parasitism within the group of dinoflagellates is a widespread phenomenon. Whether the parasitic dinoflagellates exhibit specificity in their infection is not well known, but this possibility has become an important issue in the development of biological control of harmful algal blooms. The 18S rDNA sequences from the parasite Amoebophrya sp. and its dinoflagellate host Dinophysis norvegica were determined and compared with the published sequence of Amoebophrya sp. infecting Gymnodinium sanguineum and other dinoflagellates. The results showed that the sequence from the parasite within D. norvegica was clustered with that of the one from G. sanguineum with 100% bootstrap support in a maximum-likelihood analysis. The observed identity between these two sequences was 93%, which indicates that they are not identical species. The two sequences from Amoebophrya sp. were deeply branched within the group of dinoflagellate sequences and represent the earliest diverging dinoflagellates. The sequence from the parasite Parvilucifera infectans, also infecting D. norvegica, was not closely related to the Amoebophrya sp. sequences. The sequence from D. norvegica appeared as a sister group to a cluster containing Prorocentrum lima and Alexandrium spp. without significant bootstrap support. The data presented herein support the hypothesis that A. ceratii comprises more than one species, and this opens the possibility that infections of harmful algal species might involve more than one Amoebophrya species.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999
The occurrence of annual marine phytoplankton blooms is becoming a global problem. In Europe, the... more The occurrence of annual marine phytoplankton blooms is becoming a global problem. In Europe, the NUTOX project supported by the EC investigates if unbalanced nutrient compositions in the water promote the dominance of harmful phytoplankton species. One of the tasks is the determination of the elemental composition of single phytoplankton cells. This is carried out using the Lund Nuclear Microprobe with a special focus on C, N, P and K. The overall aim is to understand the mechanism leading to toxin production, model it and eventually propose a counteracting method. The preparative method, used to isolate single living cells while reducing their salt environment, is an important part of the analytical procedure. A comparison of light element detection using backscattering from protons and nuclear reaction analysis using deuterons is made. Ó 0168-583X/99/$ -see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 9 ) 0 0 3 7 2 -9
Marine Pollution Bulletin, 2008
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversi... more The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.
Marine Ecology Progress Series, 2005
... 1996, Schramm &amp; Nienhuis 1996, Johansson et al. 1998, Eriksson et al. 2002), incl... more ... 1996, Schramm &amp; Nienhuis 1996, Johansson et al. 1998, Eriksson et al. 2002), including the Baltic Sea (Hällfors et al. 1984, Cederwall &amp; Elmgren 1990, Eriksson et al. 1998, Rönnberg &amp; Mathiesen 1998, Lotze et al. 1999, Vahteri et al. 2000). ...
Marine Ecology Progress Series, 2003
The allelopathic effect of Prymnesium parvum (Prymnesiophyta), which produces toxins with haemoly... more The allelopathic effect of Prymnesium parvum (Prymnesiophyta), which produces toxins with haemolytic, ichthyotoxic and cytotoxic properties, was investigated on a natural plankton community. Under controlled conditions, 3 laboratory bioassays were performed by adding cell-free filtrate from a P. parvum culture into different size fractions (<150, <100 and 20 to 150 µm) of a natural Baltic Sea plankton community. The effect of P. parvum cell-free filtrate was determined by measuring chlorophyll a, cell numbers (phytoplankton, ciliates, bacteria), carbon ( 14 C) uptake by phytoplankton and the incorporation of 3 H-leucine by bacteria. P. parvum cell-free filtrate affected the whole phytoplankton community, resulting in a decrease in both chlorophyll a and carbon uptake. Furthermore, the plankton groups present in the community exhibited different sensitivity to the cellfree filtrate. While growth of cyanobacteria and dinoflagellates was inhibited, that of diatoms and ciliates was not only completely suppressed, but no cells were present at the end of the experiment in the bottles with P. parvum filtrate. In all experiments, therefore, cyanobacteria and dinoflagellates were the most resistant groups, which led to their dominance in the treatments with filtrate compared to controls. Bacterial production was also negatively affected by P. parvum filtrate. The results show that compounds released by P. parvum induce changes in the plankton community structure, killing other members of the marine food-web, especially other phytoplankton (allelopathy), and suggest that secreted compounds of P. parvum are inhibitory to potential grazers (ciliates). It is proposed that allelopathy is an important process in the ecology of P. parvum.
Marine Ecology Progress Series, 2007
Summer N 2 -fixing cyanobacterial blooms are a common feature in the Baltic Sea, and the occurren... more Summer N 2 -fixing cyanobacterial blooms are a common feature in the Baltic Sea, and the occurrence of Nodularia spumigena toxic blooms is of particular concern. Cyanobacterial blooms can be favoured by certain conditions including high concentrations of dissolved organic matter, which may increase the availability of iron critical for N 2 fixation. Cyanobacteria may negatively affect grazers because many species produce toxins and generally lack fatty acids essential for zooplankton reproduction. In this study we investigated the effect of riverine high-molecular weight dissolved organic matter (DOM-)/iron-stimulated cyanobacteria on the development of proto-and metazooplankton, and evaluated the role of DOM in stimulating the zooplankton part of the microbial food web. A plankton community was incubated in cylinders with either nitrate (NO 3 ) or DOM alone or combined with iron (Fe) or zooplankton >100 µm (G). The development of proto-and metazooplankton was followed for 10 d. Trophic relationships between metazooplankton taxa and their potential food items were assessed by ordination analysis and by feeding and reproduction bottle incubations with the calanoid copepod Acartia bifilosa. Contrary to our expectations, DOM did not stimulate the microbial food web, and proto-and metazooplankton developed similarly in all treatments until the middle of the experiment. However, by the end of the experiment, the biomass of proto-and metazooplankton as well as the biomass of diatoms and dinoflagellates was greatly depressed in all DOM and NO 3 Fe treatments. In these treatments, cyanobacterial and bacterial biomasses were highest leading up to phosphate depletion. Plankton development seemed to be bottom-up controlled and to be affected by extracellular compound(s) produced by the dominant cyanobacteria, possibly triggered by phosphate limitation. Diatoms, dinoflagellates, protozoans and metazooplankton were instead stimulated in the NO 3 and NO 3 G treatments, where cyanobacterial biomass was low. Accordingly, A. bifilosa reproduction and survival were sustained in NO 3 bottles. Deleterious effects of cyanobacteria on metazooplankton were diminished in NO 3 and NO 3 G tanks where other food resources were available. Overall, the results suggest that increases in the input of DOM to the Baltic Sea can potentially stimulate cyanobacterial blooms that may disrupt the microbial food web and inhibit metazooplankton development.
Marine Ecology Progress Series, 1993
The effects of additions of river isolated hurnic compounds on biomass formation and primary prod... more The effects of additions of river isolated hurnic compounds on biomass formation and primary production of a natural phytoplankton community were compared with the effects of additions of nitrate or phosphate in a batch culture experiment lasting for 10 d during late summer. Mesozooplankton (> 150 pm) were excluded in the experiment, but micrograzers such as heterotrophic nanoflagellates, ciliates and copepod nauplii were present. The humic substances were isolated from river water using a macroporous resin (XAD-8). Trace metals, iron and vitamins were added in order to avoid growth limitation caused by these compounds. Phytoplankton biomass and primary production became significantly higher in treatments where nitrate or humic substances were added than in control flasks. Bacterial numbers became significantly higher in the treatments where humic substances were added compared with controls. Ammonium concentrations became elevated in the treatments where nitrate or hurnic substances were added. It seems likely that humic substances were utilized by bacteria both as a carbon and a nitrogen source and that nitrogen was incorporated in bacteria and later regenerated as inorganic nitrogen due to the activity of bacterial grazers and other grazers of higher trophic levels. We suggest that this is the mechanism by which nitrogen in hurnic substances becomes available for coastal phytoplankton communities.
Marine Ecology Progress Series, 1995
... 1988) or amino acids (Flynn & Butler 1986). Inorganic nitrogen sources include nitrite or... more ... 1988) or amino acids (Flynn & Butler 1986). Inorganic nitrogen sources include nitrite or nitrate produced by bacterial miner-alization (Tupas & Koike 1990) and ammonia produced by excretion by grazers (Bbmstedt 1985, Probyn 1987, Caron & Goldman 1990). ...
Marine Ecology Progress Series, 2003
We studied the growth and feeding response of the ciliate Euplotes affinis when exposed to algal ... more We studied the growth and feeding response of the ciliate Euplotes affinis when exposed to algal cultures of Prymnesium parvum and Rhodomonas cf. baltica as monocultures or as mixtures. Cultures of P. parvum grown under nutrient-limited (N or P) or nutrient-sufficient conditions were tested for toxicity against E. affinis. Ciliates grew well when fed R. cf. baltica, but avoided grazing on monocultures of P. parvum, regardless of algal concentration. Increasing abundances of P. parvum decreased survival of the ciliate, even if supplied as a mixture together with high concentrations of R. cf. baltica as an alternative prey. This implies that P. parvum produces substances that were fatal to the ciliate when released to the medium. The lethal effect of P. parvum was dependent on the physiological status of the cells, with the highest toxicity in nutrient-stressed cultures. Our results suggest that toxin production in P. parvum may be a chemical defense to repel predators.