| 1. |
- Barreiro, A, et al.
(författare)
-
Relative importance of the different negative effects of the toxic haptophyte Prymnesium parvum on Rhodomonas salina and Brachionus plicatilis
- 2005
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 38:3, s. 259-267
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the relative importance of the different processes/mechanisms by which the toxic haptophyte Prymnesium parvum, cultured under different nutrient conditions, affects non-toxic phytoplankton competitors and microzooplankton grazers. P. parvum was cultured under steady-state growth in different nutrient conditions: nitrogen depleted (-N), phosphorus depleted (-P) and balanced nitrogen and phosphorus (+NP). Cells from each nutrient condition and culture cell-free filtrates, alone and combined with non-toxic prey (Rhodomonas salina), were used as food for the rotifer Brachionus plicatilis. An additional experiment was carried out to test the effect of P. parvum cells and culture cell-free filtrate on R. salina. The highest haemolytic activity values were achieved by -P F parvum cultures, followed by -N. However, the negative effect of R parvum on R. salina and rotifers did not correlate with haemolytic activity but with the number of P. parvum cells. -N-cultured P. parvum were the most toxic for both R. salina and rotifers, followed by +NP. Therefore, haemolytic activity is not a good indicator of the total potential toxicity of R parvum. The growth rate of R. salina was negatively affected by cell-free filtrates but the effect of P, parvum predation was greater. Rotifers fed on both toxic and non-toxic algae, indicating that they did not select against the toxic alga. The P. parvum cell-free filtrate had an effect on B. plicatilis, although this was weak, B, plicatilis was also indirectly affected by P. parvum due to the negative effects of the toxic alga on their prey (R. salina). However, the greatest negative effect of P. parvum on the rotifers was due to ingestion of the toxic cells. Therefore, the phytoplankton competitor R. salina is more affected by P. parvum predation and the grazer B. plicatilis is more affected by ingestion of the toxic cells, the effects of excreted compounds being secondary.
|
|
| 2. |
- Fistarol, GO, et al.
(författare)
-
Allelopathic effect on a nutrient-limited phytoplankton species
- 2005
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 41:2, s. 153-161
-
Tidskriftsartikel (refereegranskat)abstract
- For aquatic systems, studies on allelopathic interactions among phytoplankton have increased over recent years, with the main focus on the role of the donor organism. In this study, we report on the response of a target organism to allelochemicals and whether this response was affected by stress conditions (nutrient limitation). We exposed the diatom Thalassiosira weissflogii, grown under different nitrogen (N) and phosphorus (P) conditions (NP, -N, or -P), to single or daily additions of a cell-free filtrate of Prymnesium parvum (grown with no nutrient limitation). When we exposed T weissflogii to a single addition of filtrate, all 3 treatments were inhibited by P. parvum. However, T weissflogii NP was the most resistant, while T weissflogii -N showed the highest sensitivity to P. parvum filtrate, followed by T weissflogii -P. When T weissflogii was exposed. to daily additions of P. parvum, the degree of inhibition of all T weissflogii treatments was higher than when only 1 initial addition was made. In this case, even the treatment that had the highest resistance (T weissflogii NP) was not only inhibited by the filtrate, but also showed a decrease in cell numbers. Nevertheless, T weissflogii -N was still more sensitive than the other treatments. Therefore, nutrient-limiting conditions may increase allelopathic effects, by making the target more susceptive to allelopathic compounds. Under these conditions, allelopathy may play a strong role in phytoplankton competition, especially in natural environments where the allelochemicals are continuously released and, thus, the target species do not have time to recover.
|
|
| 3. |
|
|
| 4. |
- Glibert, PA, et al.
(författare)
-
Ocean urea fertilization for carbon credits poses high ecological risks
- 2008
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 56:6, s. 1049-1056
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Persson, Karl-Johan, et al.
(författare)
-
Detection of nodularin in European flounder (Platichthys flesus) in the west coast of Sweden: evidence of nodularin mediated oxidative stress
- 2009
-
Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 8:6, s. 832-838
-
Tidskriftsartikel (refereegranskat)abstract
- The brackish, bloom-forming cyanobacterium Nodularia spumigena produces a peptide called nodularin, which may induce liver damage in fish. In the summer of 2007, nodularin was detected in liver tissue of European flounder caught in Swedish waters of Öresund, within the upper salinity limit for N. spumigena. Nodularinconcentrations ranging between 22 and 557 μg kg−1 liver (d.w.) were detected in fish liver. Nodularin was not detected in blue mussels (Mytilus edulis). Although N. spumigena blooms can occur in the area, the cyanobacteria were only present in very small amounts in 2007. Results suggested that nodularin accumulated inflounder livers during the summer of 2006, when vast N. spumigena blooms were observed in Öresund, and persisted over several months. Nodularin has previously been shown to induce oxidative stress in mice, crustaceans and mollusks but work on the potential negative effects of nodularin on fish is still scarce. To examine the dynamics of nodularin induced oxidative stress in liver tissue of flounder, the differential responses of the antioxidant enzymes glutathione-S-transferase catalase(CAT) and the formation of malondialdehyde (MDA) were monitored during 14 days in flounder exposed to an intraperitoneal injection of nodularin (0, 2, 10 and 50 μg nodularin kg−1 body weight). The activities of GST and CAT in the liver decreased significantly in the 50 μg nodularin kg−1 exposure after 7 days, but were restored to control levels after an additional 10 days of recovery. The results suggested that nodularin induced oxidative stress in terms of decreased GST and CATactivity, which can result in increased vulnerability of the cell to reactive oxygen species (ROS). No significant changes could be found in MDA levels between the treatments. Thus, the antioxidant defense system presumably managed to prevent oxygen mediated toxicity as seen by the unchanged levels of MDA. Alteration of the enzymatic defense system may increase energetic costs, thus reducing fish growth and survival. The present study also suggests that oxidative stress biomarkers can be used in fish to detect early responses to nodularin.
|
|
| 9. |
- Rengefors, Karin, et al.
(författare)
-
Broad allelopathic activity in Peridinium aciculiferum (Dinophyceae)
- 2007
-
Ingår i: European Journal of Phycology. - : Informa UK Limited. - 1469-4433 .- 0967-0262. ; 42:4, s. 341-349
-
Tidskriftsartikel (refereegranskat)abstract
- The dinoflagellate Peridinium aciculiferum forms blooms underneath the ice in temperate lakes and has previously been shown to have an allelopathic effect on a natural competitor as well as being haemolytic. Hence, we investigated whether P. aciculiferum is allelopathic towards a wide range of different freshwater phytoplankton species. We also tested the hypothesis that nutrient (N and P) deficiency enhances its allelopathic effect. In addition, we explored how target cell density affected the extent of the allelopathic effect. Our findings showed that P. aciculiferum had a negative effect (mortality through lyses) on Synura petersenii (Chrysophyceae), Peridinium inconspicuum (Dinophyceae), Cyclotella sp. (Bacillariophyceae), Cryptomonas sp. and Rhodomonas lacustris (Cryptophyceae). Only Chlamydomonas reinhardtii (Chlorophyceae) cells were not negatively affected. In semi-continuously grown nutrient deficient cultures, we detected no allelopathic activity, in contrast to the findings for batch cultures. Finally, we found that, at donor-target cell ratios above 6:1, the algicidal effect of P. aciculiferum did not increase. We concluded that the allelopathic activity of P. aciculiferum has a wide span of action due to either a single chemical or a cocktail of allelochemicals, but that allelopathic activity is highly variable depending on growth conditions.
|
|
| 10. |
- Skovgaard, Alf, et al.
(författare)
-
Observation of live specimens of Pseudotontonia cornuta (Ciliophora : Oligotrichida) reveals new distinctive characters
- 2005
-
Ingår i: Journal of the Marine Biological Association of the United Kingdom. - 0025-3154 .- 1469-7769. ; 85:4, s. 783-786
-
Tidskriftsartikel (refereegranskat)abstract
- A large planktonic ciliate, Pseudotontonza cornuta, was observed during a cruise in the North Sea, Denmark, in summer 2001. Live cells as well as fixed and protargol-stained specimens were studied. The species possessed the characteristic tail of Tontoniidae, somatic cillature classifying it as a Pseudotontonia, and cell proportions and oral ciliature corresponding to P cornuta. Observation of live cells, however, revealed distinctive features as chloroplast- containing tentacles emerging just below the apical membranelles and an S-shaped proximal rim of the left margin of the oral cavity. These characters are eye-catching in live specimens, but have passed unnoticed till now because all previous studies on P cornuta have been made on fixed samples.
|
|
