981 resultados para Marine animals
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Toxicity of effluent from a titanium dioxide factory containing sulphuric acid residue with soluble iron metallic salts and insoluble material such as silica, etc. on fishes, decapods and molluscs was studied. The effluent caused changes in pH and oxygen depletion of the sea water. Sublethal effects of the precipitate of ferrous salts were also studied. Dilutions of effluent up to 1:150 were LC100 for all organisms used while 1:200 dilution was LC50 for fishes at 36 hr and for other organisms at 48 hr. But death of organisms at this concentration was caused by pH changes and oxygen depletion and did not account for the effects of the precipitate. Below this level precipitation started soon after mixing with sea water causing death of organisms by choking their gills and siphons. Dilutions,< 1:1000 were 96 hr LCO.
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Lipid extraction of biomass prior to stable isotope analysis is known to cause variable changes in the stable nitrogen isotopic composition (d15N) of residual biomass. However, the underlying factors causing these changes are not yet clear. Here we address this issue by comparing the d15N of bulk and residual biomass of several marine animal tissues (fish, crab, cockle, oyster, and polychaete), as well as the d15N of the extracted lipids. As observed previously, lipid extraction led to a variable offset in d15N of biomass (differences ranging from -2.3 to +1.8 per mil). Importantly, the total lipid extract (TLE) was highly depleted in 15N compared to bulk biomass, and also highly variable (differences ranging from -14 to +0.7 per mil). The TLE consisted mainly of phosphatidylcholines, a group of lipids with one nitrogen atom in the headgroup. To elucidate the cause for the 15N-depletion in the TLE, the d15N of amino acids was determined, including serine because it is one of the main sources of nitrogen to N-containing lipids. Serine d15N values differed by -7 to +2 per mil from bulk biomass d15N, and correlated well with the 15N depletion in TLEs. On average, serine was less depleted (-3 per mil) than the TLE (-7 per mil), possibly due to fractionation during biosynthesis of N-containing headgroups, or that other nitrogen-containing compounds, such as urea and choline, or recycled nitrogen contribute to the nitrogen isotopic composition of the TLE. The depletion in 15N of the TLE relative to biomass increased with the trophic level of the organisms.
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The deep-sea environment is difficult to sample, and often only small quantities of samples can be obtained when using less destructive methods than dredging. When working with marine animals that are difficult to sample and with limited quantities of tissue to extract lipids, it is essential to ensure that the used method extracts the maximum possible quantity of lipids. This study evaluates the efficiency of introducing modifications to the method originally described by Bligh & Dyer (1959). This lipid extraction method is broadly used with modifications, although these usually lack proper description and evaluation of increment in lipids. In this study we consider the improvement in terms of amount of lipids extracted by changing the method. Lipid content was determined by gravimetric measurements in eight invertebrates from the deep-sea, including deep-sea hydrothermal vents animals, using three different approaches. Results show increases of 14% to 30% in lipid contents obtained from hydrothermal vent invertebrate tissues and whole animals by placing the samples in methanol for 24 hours before applying the Bligh & Dyer mixture. Efficiency of the extractions using frozen and freeze-dried samples was also compared. For large sponges, the use of lyophilized materials resulted in increases of 3 to 7 times more lipids extracted when compared with extractions using frozen samples.
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pt. 1
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v.81 (1983)