| 1. |
- Lindahl, Odd, et al.
(författare)
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Improving marine water quality by mussel farming: A profitable solution for Swedish society
- 2005
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Ingår i: Ambio. - : Allen Press Inc.. - 0044-7447 .- 1654-7209. ; 34:2, s. 131-138
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Tidskriftsartikel (refereegranskat)abstract
- Eutrophication of coastal waters is a serious environmental problem with high costs for society globally. In eastern Skagerrak, reductions in eutrophication are planned through reduction of nitrogen inputs, but it is unclear how this can be achieved. One possible method is the cultivation of filter-feeding organisms, such as blue mussels, which remove nitrogen while generating seafood, fodder and agricultural fertilizer, thus recycling nutrients from sea to land. The expected effect of mussel farming on nitrogen cycling was modeled for the Gullmar Fjord on the Swedish west coast and it is shown that the net transport of nitrogen (sum of dissolved and particulate) at the fjord mouth was reduced by 20%. Existing commercial mussel farms already perform this service for free, but the benefits to society could be far greater. We suggest that rather than paying mussel farmers for their work that nutrient trading systems are introduced to improve coastal waters. In this context an alternative to nitrogen reduction in the sewage treatment plant in Lysekil community through mussel farming is presented. Accumulation of bio-toxins has been identified as the largest impediment to further expansion of commercial mussel farming in Sweden, but the problem seems to be manageable through new techniques and management strategies. On the basis of existing and potential regulations and payments, possible win-win solutions are suggested.
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| 2. |
- Bayne, B. L., et al.
(författare)
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Seasonal variability in feeding behaviour, metabolic rates and carbon and nitrogen balances in the Sydney oyster, Saccostrea glomerata (Gould)
- 2006
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 332:1, s. 12-26
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Tidskriftsartikel (refereegranskat)abstract
- To establish if nutrients limit the growth of bivalves requires information not only on the quality of food available, but also the animals' feeding behaviour and endogenous metabolic demands. We hypothesized that growth of the Sydney rock oyster (Saccostrea glomerata) would vary in response to seasonal changes in food quality rather than quantity. We also predicted that the oysters would show feeding preferences for nitrogen over carbon, and this behaviour would result in carbon/nitrogen (C/N) ratios for ingested and absorbed matter that would be lower than the C/N of both the seston and the oysters' estimated metabolic maintenance requirements. The experiments were done in two phases under natural conditions. In phase 1, feeding behaviour was assessed on a single occasion and the results used to pose hypotheses for testing in phase 2, which included measurements made on three occasions encompassing autumn, winter and spring conditions. Growth rates varied with changes in ambient food quality and not with the concentration of total suspended matter. Feeding behaviour responded to food quality and, in most cases, resulted in nitrogen enrichment. For example, when nitrogen was potentially limiting to growth and/or maintenance.. due to high food C/N (July) or high nitrogen demand (March), pre-ingestive selection ensured nitrogen enrichment of ingested matter and UN ratios of ingested matter which were below the maintenance requirement. However, in November, when endogenous demands indicated an increased requirement for carbon, feeding behaviour resulted in carbon enrichment, an increase in carbon conversion efficiency, and ingested C/N ratios greater than the maintenance requirement. The results support the assertion of variable feeding physiology in oysters, responsive to both exogenous (seasonal differences in carbon and nitrogen availability) and endogenous (cycles of reproduction and growth) factors. (c) 2005 Elsevier B.V. All rights reserved.
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| 3. |
- Godhe, Anna, 1967, et al.
(författare)
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Oceanographic settings explain fluctuations in Dinophysis spp. and concentrations of diarrhetic shellfish toxin in the plankton community within a mussel farm area on the Swedish west coast
- 2002
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 240, s. 71-83
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Tidskriftsartikel (refereegranskat)abstract
- The influence of hydrographic, biological and meteorological variables on the abundance of Dinophysis spp. and the concentration of diarrhetic shellfish toxin (DST) in the plankton population were investigated in a mussel (Mytilus edulis) farm area on the Swedish west coast. This location provided an opportunity to simultaneously compare Dinophysis spp. cell numbers, concentration of DST in natural phytoplankton assemblages and toxicity of mussel tissues. Sampling was performed every other day from October 10 to November 5, 2000, and on each occasion, 5 randomly selected sites were sampled. During this period, 3 distinct water masses passed through the vicinity of the mussel farm. The second water mass, characterized by low salinity and nitrogen concentration, was probably advected into the area from surface waters in the nearby Skagerrak. This low salinity water also contained a high abundance of Dinophysis spp., and high concentrations of DST were recorded in the phytoplankton population. Multivariate analysis (projection to latent structures by means of partial least squares, PLS) determined that the principal variables influencing the concentration of DST in the plankton assemblage were the causative species (D. acuminata, D. acuta and D. norvegica) and salinity. The abundance of the 3 Dinophysis spp. was inversely correlated to salinity. A rapid increase in the toxicity of mussels in response to the high levels of DST was observed. The concentration of DST had doubled within 2 d of the appearance of Dinophysis spp. After 8 d, the water mass containing Dinophysis spp. was replaced and cell numbers again returned to low levels. The concentration of DST in the phytoplankton samples remained high for another 2 d after the number of Dinophysis spp. had declined and the toxicity of mussels continued to be high for the remainder of the study. Causes of the rapid intoxication versus slow detoxification of mussels are discussed. These results suggest that present monitoring programs are insufficient to provide early warning of toxic blooms to aquaculturists on the Swedish west coast.
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| 4. |
- Svensson, Per, 1949, et al.
(författare)
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Pleasing everyone?
- 2004
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Ingår i: Critical Perspectives on Projects.
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Konferensbidrag (refereegranskat)
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| 5. |
- Svensson, Susanne, 1964, et al.
(författare)
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Analysis of the importance of lipid breakdown for elimination of okadaic acid (diarrhetic shellfish toxin) in mussels, Mytilus edulis: results from a field study and a laboratory experiment
- 2004
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Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X. ; 66:4, s. 405-418
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Tidskriftsartikel (refereegranskat)abstract
- Okadaic acid (OA) is a lipophilic phycotoxin, which accumulates in the digestive organs of mussels and may cause diarrhetic shellfish poisoning (DSP) in humans. Depuration of toxic mussels is a potential option for the shellfish industry to increase the availability of marketable mussels. To develop cost-effective deputation methods for DSP toxins, knowledge about the environmental conditions and physiological processes regulating the rate of depuration is essential. In this paper, the importance of lipid breakdown for elimination of OA in mussels was investigated by performing a field study and a manipulative laboratory experiment. First, total lipid content and concurrent concentration of OA in the digestive glands of farmed blue mussels, Mytilus edulis, was analysed on a monthly basis from January to June 2000. A significant positive correlation between levels of OA and lipid content was observed between January and March, when lipid levels were showing a decreasing trend. This supported a previously proposed model that breakdown of lipid stores may affect the release and elimination of this lipophilic toxin. To test this causal model, a laboratory experiment was performed. Mussels containing OA were exposed to experimental treatments (increased seawater temperature and/or food limitation) for 24 days in order to increase the energy requirements and need to use lipids as an energy source. It was predicted that mussels exposed to these treatments would have a faster elimination rate of OA compared to feeding mussels kept in ambient seawater temperature. The results showed that lipid content was significantly reduced in mussels exposed to an increased water temperature (24 degreesC) compared to ambient temperature (18 degreesC). The amount of lipids was not affected by food limitation. Although lipid content was-reduced in 24 degreesC, the rate of depuration of OA was not faster for mussels in this treatment and no correlation was detected between lipid content and, OA. Depuration rates were very similar for all treatments and followed an exponential decrease relationship (t(1/2) = 8 days). Thus, the proposed model that lipid breakdown affects the mechanism of elimination of OA was not supported. Nevertheless, the observed rates of depuration provide useful information and a potential predictive too] for large-scale depuration methods of mussels. The difficulties to influence the rate of depuration of this toxin by changing the environmental conditions suggest that processes, insensitive to short-term manipulation of the external environment, regulate depuration of OA. (C) 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Svensson, Susanne, 1964
(författare)
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Depuration of Okadaic acid (Diarrhetic Shellfish Toxin) in mussels, Mytilus edulis (Linnaeus), feeding on different quantities of nontoxic algae
- 2003
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Ingår i: Aquaculture. - 0044-8486. ; 218:1-4, s. 277-291
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Tidskriftsartikel (refereegranskat)abstract
- Depuration of mussels contaminated by Diarrhetic Shellfish Toxins (DST) is a potential option for the shellfish industry to manage the impact of DST. Field observations have suggested that the main factor regulating the rate of deputation of DST is the quantity of nontoxic algae available for the mussels to feed upon. In this paper, the effects of the quantity of food, which mussels feed upon, on the rate of deputation of DST in Mytilus edulis L. was tested in a laboratory experiment. Mussels naturally contaminated by the DST okadaic acid (OA) were collected from a mussel farm located on the Swedish west coast during a bloom event. Individual mussels were placed in filtered seawater and given daily rations of a mixture of nontoxic algae as follows: no food, 0.5% and 1.5% of dry weight body mass day(-1). Depuration was performed over 1, 2, 4, 8, 16 or 32 days. The levels of OA decreased in all treatments with time, with an average of approximately 50% reduction after 32 days. No significant differences in content of OA among food rations were detected. In contrast to predictions, a trend towards lower levels of toxins in the mussels receiving no food compared to both food treatments was observed after 32 days of deputation. The loss of toxins in mussels that were not feeding correlated with a considerable loss in the mass of the digestive gland between 16 and 32 days. It was concluded that the rate of depuration of OA in mussels is not positively correlated with digestive activity and fecal production. Instead, the lipophilic character of the OA molecule suggests that OA may have affinity for lipid-rich cellular and intracellular components. Increased usage of lipid stores, which occur during starvation, may accelerate the release of OA. This model could explain the observations made during the last part of this experiment. In management of toxic mussels, depuration in waters free of toxic algae is not likely to be enhanced by increasing the food supply to mussels; however, long periods of deputation in the absence of food should be avoided because of the negative effects on the condition of the mussels. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 7. |
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| 8. |
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| 9. |
- Svensson, Susanne, 1964, et al.
(författare)
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Mussel blood cells, resistant to the cytotoxic effects of okadaic acid, do not express cell membrane p-glycoprotein activity (multixenobiotic resistance)
- 2003
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Ingår i: Aquatic Toxicology. - 0166-445X. ; 65:1, s. 27-37
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Tidskriftsartikel (refereegranskat)abstract
- Okadaic acid (OA) is a dinoflagellate toxin, accumulating in shellfish and causing diarrhetic shellfish poisoning (DSP) in humans. OA is a highly cytotoxic agent in most cell lines because of its inhibiting properties of protein phosphatases. So far, the cytotoxicity of OA in mussels, the main vectors of DSP, has not been investigated. In this paper, the viability of mussel (Mytilus edulis) blood cells incubated in 10 nM-1 muM OA was studied. After 72 It of exposure, viability was reduced to 54% in 1 muM OA compared with 88% in control cells. This yielded a LC50 of > 1 muM for OA, which is 30-1000-times higher compared with other cell types. It was hypothesised that P-glycoprotein (p-gp) activity (multixenobiotic resistance, MXR) contributed to the resistance to OA. Vincristine and rhodamine B was used as p-gp substrates and verapamil or staurosporine (ST) as inhibitors of p-gp transport. However, no indications of cell membrane p-gp activity were detected. Instead, experimental observations led to the conclusion that a MXR transport system was present within lysosomal membranes. Various concentrations of OA did not affect the dynamics of vincristine in blood cells. As a positive control for the assay, p-gp activity was measured in mussel gill tissue. The efflux of rhodamine B was reduced by verapamil, which is, considered evidence for cell membrane p-gp activity, thus the accuracy of the method was confirmed. Rhodamine B efflux was also reduced by OA in gill tissue, which suggested that OA is either a competitive substrate or inhibitor of p-gp activity. When the volume of the lysosomal compartment was measured in blood cells pre-exposed to OA, a significant increase was detected compared with control cells. It was proposed that uptake and storage of OA within the lysosomal system might protect mussel blood cells from the cytotoxic effects of this compound. (C) 2003 Elsevier B.V. All rights reserved.
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| 10. |
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