Fatty Acid Composition in Blubber, Liver, and Muscle of Marine Mammals in the Southern Baltic Sea

Abstract

To date, only limited results on the fatty composition in different tissues of the top predators in the Baltic Sea are available. In the current study, tissue samples of blubber, skeletal muscle, and liver from 8 harbour porpoise (Phocoena phocoena) and 17 grey seals (Halichoerus grypus) in the Baltic Sea off Mecklenburg-Western Pomerania were included in the investigation. While the total fatty acid content in liver and blubber tissue revealed no differences between both species, the total fatty acid content of muscle tissue was significantly differentand showed higher concentrations in harbour porpoise muscle compared with grey seals. The most abundant fatty acids in the blubber of grey seals and harbour porpoises (18:1cis-9, 16:1cis-9, 16:0 and 22:6n-3) were present in similar quantities and ratios to each other as known from other marine top predators. If future studies can show that differences in tissue fatty acid content are caused by variation in the nutritional status, and this may lead to the development of a more objective assessment of body condition in seals and porpoises recovered via stranding schemes.

Hepatic Fatty Acid Profiles Associated with Exposure to Emerging and Legacy Halogenated Contaminants in Two Harbor Seal Populations across the North Atlantic

“…Varying FA profiles were observed in the two seal populations. The most abundant FAs in the liver of harbor seals from the south coast of Sweden were 18:0, 16:0, 18:1 ( n – 9), and 20:4 ( n – 6), consistent with the hepatic FA profiles of gray seals and harbor porpoise in the South Baltic Sea . The most abundant FAs in harbor seals from the Gulf of Maine, on the other hand, were 18:1 ( n – 9), 16:0, 18:0, and 18:1 ( n – 7).…”

“…The most abundant FAs in the liver of harbor seals from the south coast of Sweden were 18:0, 16:0, 18:1 (n − 9), and 20:4 (n − 6), consistent with the hepatic FA profiles of gray seals and harbor porpoise in the South Baltic Sea. 9 The most abundant FAs in harbor seals from the Gulf of Maine, on the other hand, were 18:1 (n − 9), 16:0, 18:0, and 18:1 (n − 7). In general, seals from the south coast of Sweden had a higher abundance of ∑SFAs and ∑n − 3 PUFAs, but a lower abundance of ∑MUFAs, compared to those in the Gulf of Maine (Table 1).…”

“…1 Indeed, altered proportions of saturated FAs (SFAs) and unsaturated FAs (UFAs) have been associated with various metabolic diseases such as type 2 diabetes and nonalcoholic fatty liver disease. 6,7 In addition to the influence by dietary uptake, 8,9 hepatic FA profiles are also determined by multiple metabolic pathways regulated by many factors including nuclear receptors and transcription factors. 10,11 These factors are also potential targets of many endocrine-disrupting chemicals (EDCs), 12 specifically those metabolism-disrupting chemicals that could cause metabolism dysregulation.…”

“…Fatty acids (FAs) are essential constituents of biological membrane lipids, the most commonly stored and circulating forms of energy, and the contributor to the regulation of a wide variety of biological activities. , In diving mammals such as seals, FAs are involved in vital functions, including thermoregulation and development, as well as the survival-related diving capacity. , Because the liver plays a central role in FA synthesis and disposal, disruption of hepatic FA metabolism may have wide impacts on metabolic health. , In addition, the biological effects and physico-chemical properties of FAs largely depend on their chain length and degree of saturation . Indeed, altered proportions of saturated FAs (SFAs) and unsaturated FAs (UFAs) have been associated with various metabolic diseases such as type 2 diabetes and nonalcoholic fatty liver disease. , In addition to the influence by dietary uptake, , hepatic FA profiles are also determined by multiple metabolic pathways regulated by many factors including nuclear receptors and transcription factors. , These factors are also potential targets of many endocrine-disrupting chemicals (EDCs), specifically those metabolism-disrupting chemicals that could cause metabolism dysregulation. , …”

Age group differences in blubber fatty acid profiles in northern elephant seals (Mirounga angustirostris)

“…In fact, these six individual FA accounted for nearly 80% of total blubber FAs regardless of age group. These FAs appear to be conserved across phocids, as these same individual FAs are commonly found in high proportions in many other pinnipeds, including Antarctic phocids (e.g., crabeater seals, Lobodon carcinophagus (Guerrero and Rogers, 2017); leopard seals, Hydrurga leptonyx (Guerrero et al, 2016); Weddell seals, Leptonychotes weddellii (Wheatley et al, 2008) and northern phocids (harbour seals, Phoca vitulina (Neises et al, 2021); ringed seals, Pusa hispida (Strandberg et al, 2008a); harp seals, Pagophilus groenlandicus (Haug et al, 2017); gray seals, Halichoerus grypus (Dannenberger et al, 2020).…”