Otto Grahl-Nielsen

Variations in the fatty acid profile of marine animals caused by environmental and developmental changes

Abstract A method for the assessment of the fatty acid profile in single eggs or larvae of marine fish has been developed. The method, which only requires 50 μg or less of tissue, is based on methanolysis, high-resolution gas chromatography and multivariate data-analysis. In four examples employing cod eggs and larvae, shrimp and periwinkles it is demonstrated that the fatty acid profile changes with changes in the environment, like temperature change, and also with man-induced changes, like oil-pollution. The fatty acid profile of cod eggs is shown to change during the development from newly spawned to just before hatching.

Stratification, Composition, and Function of Marine Mammal Blubber: The Ecology of Fatty Acids in Marine Mammals

This study of vertical fatty acid profiles, based on analysis of 58 fatty acids sampled at 3‐mm intervals throughout the blubber column of a model marine mammal, the ringed seal (Pusa hispida), revealed three chemically distinct layers. The average depths of the outer and inner layers were quite consistent (∼1.5 and ∼1 cm, respectively). Consequently, the middle layer varied greatly in thickness, from being virtually absent in the thinnest animals to 2.5 cm thick in the fattest. The relative consistencies of the thickness and composition of the layers as well as the nature of the fatty acids making up each layer support the generally assumed function of the various layers: (1) the outer layer is primarily structural and thermoregulatory, (2) the inner layer is metabolically active with a fatty acid composition that is strongly affected by recent/ongoing lipid mobilization/deposition, and (3) the middle layer is a storage site that contracts and expands with food availability/consumption. The remarkable dynamics of the middle layer along with the discrete pattern of stratification found in the vertical fatty acid profiles have important implications for methodological sampling design for studies of foraging ecology and toxicology based on analyses of blubber of marine mammals.

Dietary influence on fatty acid composition of blubber fat of seals as determined by biopsy: A multivariate approach

A method for determination of the fatty acids of blubber fat from living seals is demonstrated: fat samples are retrieved by a small syringe, the fat is directly methanolysed, the resulting fatty acid methyl esters are gas-chromatographed and the chromatographic results are treated by multivariate principal-component analysis. The blubber fat of two grey seals [Halichoerus grypus (Fabricius, 1791)] and two harbor seals (Phoca vitulina L.) at the Aquarium of Bergen, Norway, as well as their diet, herring and mackerel, were monitored over a period of 7 mo in 1989. Fatty acid composition of the blubber fat was significantly different from that of the diet.

SIMCA multivariate data analysis of blue mussel components in environmental pollution studies

Abstract Blue mussels (Mytilus edulis) from one pristine and one polluted location on the Norwegian coast were transferred to an aquarium. After 4 months under controlled unpolluted conditions, samples of muscle tissue and gonad tissue from ten specimens of each of the two classes of mussels were characterized by capillary gas chromatography (g.c.) after methanolysis and silylation. The g.c. patterns of the 50–60 predominant peaks representing naturally occurring components were treated by SIMCA multivariate data analysis implemented to run on a HP-85 desk-top computer. This analysis discriminated clearly between two classes of mussels for both the muscle and gonad tissue. Similarly, the g.c. patterns of the gonad tissue differentiated between male and female mussels. Multivariate data treatment of naturally occurring components might thus be an alternative to the Mussel Watch survey which is based on measurements of foreign components in the mussel tissues.

Distribution of trace elements from industrial discharges in the Hardangerfjord, Norway : A multivariate data analysis of saithe, flounder and blue mussel as sentinel organisms

Arsenic, copper, zinc, cadmium, lead and mercury were determined in the muscle and liver of two species of fish, saithe (Gadus virens) and flounder (Platichthys flesus), and in the soft tissues of blue mussels (Mytilus edulis). These were sampled from eight locations along the Hardangerfjord up to 100 km from the source of the pollution at the head of the fjord. Both relative and absolute amounts of the six elements differed between the two species of fish, and, more so, between the two tissues. The mussel contained higher amounts of the elements than the fish. The pattern of the elements was also very different in the mussel. Differences and similarities among the various types of samples from the eight locations were evaluated by principal component analysis. Correlation between the six elements was also tested by this method. A concentration gradient away from the source of pollution was only found for arsenic in the saithe tissues, while the only gradient detected in flounder was for mercury in the liver tissue. In mussels the gradient for arsenic was marginal, while gradients were detected in varying degrees for the other elements. Cadmium did not correlate with the other elements in mussels. The mussel was found to be a much better sentinel organism for these elements, except arsenic, than the two fish species.

Genotypic and phenotypic fatty acid composition in the tissues of salmon, Salmo salar☆

Abstract 1. 1. Two-year-old salmon were fed for 8 months with three diets with small, but significant, differences in lipid content and fatty acid composition. 2. 2. The fatty acid composition in abdominal fat, red muscle, white muscle, liver and heart of the fish was determined at the end of the feeding period by a chemometric method. 3. 3. The fatty acid composition of all tissues differed from that of the diets, least in the abdominal fat, most in the liver and heart tissue. 4. 4. The fatty acid composition of the tissues, the heart tissue in particular, was independent of the fatty acid composition of the diets. 5. 5. Large differences in the fatty acid compositions were observed between different fish. 6. 6. The advantage of multivariate interpretation of fatty acid compositions is demonstrated.

Transfer of fatty acids from female seal blubber via milk to pup blubber

Abstract Fatty acids were determined by gas chromatography followed by principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) in the blubber of 18 female grey seals, Halichoerus grypus, in their milk and in the blubber of their 1-week-old nursing pups. Large individual differences were observed in both blubber and milk content of fatty acids. The fatty acid composition of the milk was systematically different from the composition in maternal blubber, with higher relative amounts of the saturated acids, the monounsaturated with 20 carbon atoms and the n3 polyunsaturated, except 18:3n3. The composition of the fatty acids in the blubber of the pups was different from that of the milk. The same fatty acids that were enriched in the milk were depleted in the blubber of the pups. Therefore the fatty acid composition in the blubber of the pups was similar to that in the adults, although not identical. The results from this investigation imply that the composition of the fatty acids in the blubber of female seals and in the blubber of their pups cannot be determined directly by analysis of fatty acid composition of milk.

Identification of weathered oils

Abstract Crude oils from the Cook and Brent formations in the same well at the Gullfaks field in the North Sea were weathered for one year under natural conditions. Samples of the oils were collected at intervals and analysed by GC-MS for the common so-called biomarkers: steranes at m/z 217, and pentacyclic triterpanes at m/z 191 and m/z 177. The resulting fragmentograms were treated by multivariate analysis. The patterns of steranes differed between the unweathered oils, but weathering affected them in such a way that identification was impossible after 4 months. The pattern of pentacyclic triterpanes were different for the two oils during the year, rendering these a good tool for identification of weathered oils, the demethylated triterpanes in particular.

Fatty acid composition in blubber, heart and brain from phocid seals

The fatty acid composition of phocid seals was investigated in order to map the possible stratification of fatty acids in the depot fat and to detect possible differences between different tissues and between the four species grey seal (Halichoerus grypus), harbour seal (Phoca vitulina), ringed seal (Phoca hispida) and harp seal (Phoca groenlandica). We used a chemometric method in this analysis: the fatty acids were determined by gas chromatography, and the relative amounts of fatty acids were treated by principal component analysis. Analysis of the depot fat in the four species indicates that the fatty acid composition of the blubber varies along a gradient from the epidermis. We are able to distinguish between three distinct vertical layers. With increasing depth from the epidermis, the amount of saturated and long-chained monounsaturated fatty acids in the blubber fat increased, while the amount of short-chained monounsaturated fatty acids decreased. The four seal species exhibited differences in fatty acid composition in the outermost layer of the blubber. In contrast, the middle and inner layers did not show differences between species. We also analysed the fatty acid composition of heart and brain tissue from harp seals. The three tissues had distinctly different profiles.

Discrimination of Sebastes viviparus, Sebastes marinus and Sebastes mentella from Faroe Islands by chemometry of the fatty acid profile in heart and gill tissues and in the skull oil

The composition of fatty acids in the tissue of heart, gill and skull oil of the three redfish species, Sebastes viviparus, Sebastes marinus and Sebastes mentella was determined by a chemometric method. The method consists of methanolysis of samples of the tissues and of the oils, gas chromatography of the resulting fatty acid methyl esters and multivariate statistical treatment, by principal component analysis, of the analytical data. Although the differences in fatty acid composition among the three tissues were the dominating features of the data, the three species had significantly different fatty acid profiles within each tissue, even though variation among the individuals was considerable. The fatty acid profiles appear to be species specific. The mutual relationship between S. marinus and S. mentella is closer than the relationship between either of them and S. viviparus.