| 1. |
- Fistarol, G. O., et al.
(författare)
-
Allelopathy in Alexandrium spp.: effect on a natural plankton community and on algal monocultures
- 2004
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 35:1, s. 45-56
-
Tidskriftsartikel (refereegranskat)abstract
- We studied allelopathy in the dinoflagellate genus Alexandrium by testing the effect of A. tamarense on a natural plankton community from Hopavagen Bay, Trondheimsfjord, Norway, and the effect of toxic and non-toxic strains of A. tamarense and a toxic strain of A. minutum on algal monocultures. Also, a possible relation between the allelopathic effect and the production of paralytic shellfish poison (PSP) toxin was investigated. A. tamarense affected the whole phytoplankton community by decreasing the growth rate and changing the community structure (relative abundance of each species, dominant species). A negative effect of A. tamarense was also observed on ciliates, but not on bacteria numbers, In the bioassay with algal monocultures, the diatom Thalassiosira weissflogii and the cryptophyte Rhodomonas sp. were exposed to the filtrate of Alexandrium spp. All tested Alexandrium strains negatively affected T weissflogii and Rhodomonas sp. cultures, independent of whether PSP toxins were produced. The compounds released by Alexandrium caused lysis of natural and cultured algal cells, suggesting that the allelopathic effect may be connected with previously described ichthyotoxic and haemolytic properties of Alexandrium. Furthermore, the observation that several components of the plankton community were affected by compounds released by A. tamarense emphasizes the importance of allelopathy for the ecology of this species.
|
|
| 2. |
- Fistarol, Giovana, et al.
(författare)
-
Temporary cyst formation in phytoplankton: a response to allelopathic competitors?
- 2004
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 6:8, s. 791-798
-
Tidskriftsartikel (refereegranskat)abstract
- Competition among phytoplankton for limiting resources may involve direct or indirect interactions. A direct interaction of competitors is the release of chemicals that inhibit other species, a process known as allelopathy. Here, we investigated the allelopathic effect of three toxic microalgae species (Alexandrium tamarense, Karenia mikimotoi and Chrysochromulina polylepis) on a natural population of the dinoflagellate Scrippsiella trochoidea. Our major findings were that in addition to causing death of S. trochoidea cells, the allelopathic species also induced the formation of temporary cysts in S. trochoidea. Because cysts were not lysed, encystment may act as a defence mechanism for S. trochoidea to resist allelochemicals, especially when the allelopathic effect is moderate. By forming temporary cysts, S. trochoidea may be able to overcome the effect of allelochemicals, and thereby have an adaptive advantage over other organisms unable to do so.
|
|
| 3. |
- Legrand, Catherine, et al.
(författare)
-
Allelopathy in phytoplankton – biochemical, ecological and evolutionary aspects
- 2003
-
Ingår i: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 42:4, s. 406-419
-
Tidskriftsartikel (refereegranskat)abstract
- It is considered self-evident that chemical interactions are a component of competition in terrestrial systems, but they are largely unknown in aquatic systems. In this review, we propose that chemical interactions, specifically allelopathy, are an important part of phytoplankton competition. Allelopathy, as defined here, applies only to the inhibitory effects of secondary metabolites produced by one species on the growth or physiological function of another phytoplankton species. A number of approaches are used to study allelopathy, but there is no standard methodology available. One of the methods used is cross-culturing, in which the cell-free filtrate of a donor alga is added to the medium of the target species. Another is to study the effect of cell extracts of unknown constituents, isolated exudates or purified allelochemicals on the growth of other algal species. There is a clear lack of controlled field experiments because few allelochemicals have been identified. Molecular methods will be important in future to study the expression and regulation of allelochemicals. Most of the identified allelochemicals have been described for cyanobacteria but some known toxins of marine dinoflagellates and freshwater cyanobacteria also have an allelochemical effect. The mode of action of allelochemicals spans a wide range. The most common effect is to cause cell lysis, blistering, or growth inhibition. The factors that affect allelochemical production have not been studied much, although nutrient limitation, pH, and temperature appear to have an effect. The evolutionary aspects of allelopathy remain largely unknown, but we hypothesize that the producers of allelochemicals should gain a competitive advantage over other phytoplankton. Finally, we discuss the possibility of using allelochemicals to combat harmful algal blooms (HABs). Allelopathic agents are used for biological control in agriculture, e.g. green manures to control soil diseases in Australia, but they have not yet been applied in the context of HABs. We suggest that phytoplankton allelochemicals have the potential for management of HABs in localized areas.
|
|
| 4. |
- Pérez Blanco, Eva, et al.
(författare)
-
Cellular nutrient content measured with the nuclear microprobe and toxins produced by Dinophysis norvegica (Dinophyceae) from the Trondheim fjord (Norway)
- 2015
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 75:3, s. 259-269
-
Tidskriftsartikel (refereegranskat)abstract
- Dinophysis norvegica is a commonly occurring dinoflagellate species and a producer of diarrhetic shellfish poisons. Natural samples were collected from Trondheim fjord, Norway, to analyse nutrient (O, C, N, P) and toxin (dinophysitoxins [DXTs], okadaic acid [OA], pectenotoxins [PTXs]) content in D. norvegica cells. Nutrient and toxin analyses were also carried out on cells grown under nutrient-sufficient and nutrient-deficient conditions to determine how intracellular nutrient and toxin content varied under different nutrient availability conditions. Nutrient analyses were conducted using nuclear microprobe techniques that can accurately analyse single cells, and toxin analyses were carried out using liquid chromatography and mass spectroscopy. The intracellular carbon, nitrogen and phosphorus content in individual cells varied greatly, and intracellular C:N:P ratios showed that the cells were both N- and P-deficient when compared to the Redfield ratio. The ideal N:P ratio in the media for D. norvegica was found to be below the Redfield ratio, but intracellular ratios did not show a clear relationship with those in the media. N:P ratios of D. norvegica were higher than expected, which is likely due to their phagotrophy on zooplankon. The highest toxin values found were traces of PTX2, 24.72 pg PTX2SA cell(-1), 2.19 pg DTX1 cell(-1), and 1.01 pg OA cell(-1). However, we found no clear relationship between the content of intracellular nutrients and toxins.
|
|
| 5. |
- Sundbäck, Kristina, 1949, et al.
(författare)
-
Dissolved organic nitrogen : an important source of nitrogen for the microphytobenthos in sandy sediment
- 2011
-
Ingår i: Aquatic Microbial Ecology. - : Inter research. - 0948-3055 .- 1616-1564. ; 63:1, s. 89-100
-
Tidskriftsartikel (refereegranskat)abstract
- To test the hypothesis that dissolved organic nitrogen (DON) is important for sustaining microphytobenthic (MPB) primary production during nitrogen-limited conditions, the uptake of 15N-labelled urea, the amino acids glycine (GLY) and glutamic acid (GLU), and nitrate and ammonium were measured under simulated in-situ light and temperature conditions. Microphytobenthic primary production and chlorophyll a (Chl a) were also measured. MPB was dominated by diatoms attached to sand grains, cyanobacteria making up ~30% of the biomass. Activities of the hydrolytic ectoenzymes leucin aminopeptidase (AMA), alkaline phosphatase (APA), and β-glucosidase (GLA) in filter-fractionated sediment showed that the microbenthic community was strongly N deficient, with the bacterial fraction (<1 µm) also phosphorus limited. DON uptake (urea + glutamic acid + glycine) accounted for ~ 50–65% of the uptake of 15N-labeled substrates, with higher proportion of DON uptake at low substrate concentrations (≤2 µM). Except for nitrate, the kinetics fitted a linear model. Calculated relative preference index (RPI) based on porewater concentrations, suggested that the order of preference of the microbenthic community was NH4+ > urea > GLU > NO3- > GLY. Using a prokaryotic inhibitor (chloramphenicol) and theoretical calculations of algal uptake based on C/Chl a ratios, it was estimated that “algal” nitrogen uptake accounted for ~ 55-90% of DON uptake. Uptake rates were, however, estimated to cover only 26% –50% of the N-demand of MPB, suggesting that porewater N concentrations were not sufficient to meet the microalgal demand in early summer and that MPB in sandy sediments of micro-tidal waters may often be severely N-limited.
|
|
| 6. |
- Weich, R G, et al.
(författare)
-
Extracellular alkaline phosphatase activity in Ulva lactuca L
- 1989
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 129:1, s. 33-44
-
Tidskriftsartikel (refereegranskat)abstract
- Extracellular alkaline phosphatase activity (APA) was detected in the marine macroalga Ulva lactuca, cultivated in laboratory conditions under phosphate limitation. Algal discs were grown in continuous light and in darkness for a maximum of 205 h in sterilized seawater supplied with ammonium nitrate and various phosphate concentrations. APA and phosphate uptake in U. lactuca was stimulated in light whereas inhibition was detected in darkness. APA increased significantly during the cultivation in a phosphate-deficient medium but was suppressed at high external phosphate concentrations. In addition, pretreatment in penicillin over 48 h markedly enhanced enzyme activity during P limitation. The pretreatment in penicillin reduced the number of surface-associated bacteria. Our results indicate that APA in U. lactuca was dependent on the external phosphate concentration, energy from photophosphorylation and bacteria. Since intracellular polyphosphates and an orthophosphate pool still were displayed in 31P NMR spectra after cultivation at phosphate-limiting conditions, P deficiency was not suggested. Unfortunately, NMR spectra reflect total amounts of P compounds and local differences in the P status of the multicellular tissue could not be distinguished. Postulating a negative correlation between the P status and APA, a lower P status in meristematic areas during P limitation was suggested. Alkalisation of the growth medium during algal growth in light, and/or intracellular pH changes may additionally have affected enzyme production.
|
|
| 7. |
|
|
| 8. |
- Granéli, Edna, et al.
(författare)
-
Allelopathy in marine ecosystems
- 2006
-
Ingår i: Allelopathy. - Dordrecht : Springer Netherlands. - 9781402042799 ; , s. 415-431
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 9. |
|
|
| 10. |
- Stoecker, D, et al.
(författare)
-
Phagotrophy in harmful algae
- 2006
-
Ingår i: Ecology of Harmful Algae. - : Springer Berlin/Heidelberg. - 9783540322108 ; , s. 177-187
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
