Abstract
We have investigated changes in specific contents of protein, glycogen and lipid, and fatty acids of blue mussels, Mytilus edulis, under different conditions in the field and in laboratory feeding experiments using different microalgae. Specific contents of glycogen and lipid increased in mussels relocated to net bags at a location in Kerteminde Bay (Great Belt, Denmark) in contrast to mussels relocated to a location in Sallingsund (Limfjorden, Denmark). The polyunsaturated fatty acid, eicosapentaenoic acid, reached 3 times higher values in the mussels in Kerteminde Bay. Mussels fed pure cultures of Crypthecodinium cohnii, which is rich in the polyunsaturated fatty acid, docosahexaenoic acid, and glycogen, gained the highest specific contents of this fatty acid and glycogen. Mussels feeding on the most protein rich of the microalgae, Bracteacoccus sp., gained the highest protein contents. The specific glycogen content of the mussels was influenced by their “condition” (body dry weight/shell length ratio) while specific protein and lipid contents were not. Starvation affected mainly the specific glycogen content. These results show that biomass composition of blue mussels is affected by living site and local phytoplankton species and that the fatty acids composition of mussels reflects the content of fatty acids in the diet.
Highlights
The growth rate of filter feeding blue mussels, Mytilus edulis, is mainly determined by the concentration of suspended phytoplankton in the water [1, 2] while the biomass produced by the mussels can be of a variable biochemical composition
The mussels in Salling Sund maintained a relatively constant biomass composition, these mussels had been moved from one location to another, while the mussels in Kerteminde Bay tripled their specific glycogen content and doubled their specific contents of fatty acids in 70 days (Figure 1)
The biomass composition of Mytilus edulis is variable and the composition of proteins, glycogen, and lipids is affected by the location where it lives and the available amount and composition of phytoplankton which vary during the season
Summary
The growth rate of filter feeding blue mussels, Mytilus edulis, is mainly determined by the concentration of suspended phytoplankton in the water [1, 2] while the biomass produced by the mussels can be of a variable biochemical composition. Seasonal dependent variations in biomass composition of blue mussels are well described [3,4,5,6,7] and spawning occurs at the expense of stored glycogen and lipid [8]. Lipids, carbohydrates, and other components from phytoplankton and use these compounds to build their own biomass. The efficiency by which biomass components are retained during trophic upgrading depends largely on the number of steps in the food chain the compounds are passed through [17]. Mussels being primary consumers represent the shortest possible route of biomass compounds from phytoplankton to fishable or cultivable marine resources
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