Latitudinal and temporal variability in the community structure and fatty acid composition of deep-sea nematodes in the Southern Ocean

Antarctic (Euphausia superba) and northern krill (Meganyctiphanes norvegica) are characterised by large-scale spatial distributions. Euphausia superba is limited to the Southern Ocean, while M. norvegica is present from the Arctic Ocean to the Mediterranean Sea. Euphausia superba structural lipids showed little mesoscale variability. Specific differences between phosphatidylcholine and phosphatidylethanolamine fatty acid composition exceeded variability related to sampling stations. On a larger scale (Southern Ocean), fatty acid composition of both total polar lipids and phosphatidylcholine confirmed the reduced level of regional variability. Similar comparisons between female M. norvegica collected at two extreme sites in terms of temperature regime (Kattegat and Ligurian Sea) during two seasons (spring-summer and fall-winter) suggested a more complex picture. Levels of phosphatidylethanolamine, lysophosphatidylcholine, and diphosphatidylglycerol showed significant differences between sites. During spring- summer, a lower content of phosphatidylethanolamine and lysophosphatidylcholine was observed for the Ligurian Sea population. Fatty acid composition of total polar lipids was significantly different at both sites. Comparisons between spring-summer populations at both sites showed higher percentages of 22:6n-3 and a lower content in saturated and monoenoic acids for the Ligurian Sea, suggesting some degree of adaptation to temperature regime.

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Factors affecting the fatty acid composition of mesopelagic fish of the continental slope in the South China Sea

10.7287/peerj.preprints.26498v1 ◽

2018 ◽

Author(s):

Fuqiang Wang ◽

Ying Wu ◽

Ying Cui ◽

Zuozhi Chen ◽

Zhongyi Li ◽

...

Keyword(s):

Fatty Acids ◽

Fatty Acid Composition ◽

Fatty Acid ◽

South China Sea ◽

Southern Ocean ◽

Continental Slope ◽

Acid Composition ◽

South China ◽

Physical Factors ◽

Mesopelagic Fish

Study of the ecology of mesopelagic fish is central to assessing the active biological pump in the ocean, especially in the mesopelagic layer. As a consequence of the small size and pressure change, traditional stomach content analysis is not useful for analyzing the feeding behavior of mesopelagic fish. The use of δ13C and fatty acid analyses can help to resolve this problem. The mesopelagic fish examined in this study were collected from the continental slope in the north of the South China Sea (SCS), and are compared with nearshore SCS fish and fish collected from the Southern Ocean. The unusually high lipid content of the mesopelagic fish resulted in △δ13C values (i.e., the difference in δ13C between unextracted and extracted tissues) exceeding 1‰, which is more than the enrichment factor in the food web. Thus, extraction of lipids was conducted prior to δ13C isotope analysis for the study of trophic interactions of mesopelagic fish. Compared with other fish, mesopelagic fish had high C18:1n-9/C18:1n-7 and C20:1n-9/ C18:1n-7 ratios, which confirms that plankton is their main dietary source. Diatoms comprise a higher proportion of phytoplankton in the Southern Ocean and a lower proportion in the SCS, and this is reflected in the C20:5n-3/C22:6n-3 (EPA/DHA) ratio in mesopelagic fish in each region. The low EPA/DHA ratio in SCS fish indicates that diatoms are not the main component in the diet of mesopelagic fish. The SCS mesopelagic fish had higher C20:4n-6/C22:6n-3 (ARA/DHA) and C20:4n-6/C20:5n-3 (ARA/EPA) ratios than fish in the Southern Ocean. This result suggests that physical factors (e.g., temperature) also affect the fatty acid composition of these fish, particularly because certain fatty acids enable the fish to better adapt to extreme environmental conditions. Future studies of the synthesis of fatty acids in particular species should take account of both the dietary sources and physical factors in their environment.

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Factors affecting the fatty acid composition of mesopelagic fish of the continental slope in the South China Sea

10.7287/peerj.preprints.26498 ◽

2018 ◽

Author(s):

Fuqiang Wang ◽

Ying Wu ◽

Ying Cui ◽

Zuozhi Chen ◽

Zhongyi Li ◽

...

Keyword(s):

Fatty Acids ◽

Fatty Acid Composition ◽

Fatty Acid ◽

South China Sea ◽

Southern Ocean ◽

Continental Slope ◽

Acid Composition ◽

South China ◽

Physical Factors ◽

Mesopelagic Fish

Study of the ecology of mesopelagic fish is central to assessing the active biological pump in the ocean, especially in the mesopelagic layer. As a consequence of the small size and pressure change, traditional stomach content analysis is not useful for analyzing the feeding behavior of mesopelagic fish. The use of δ13C and fatty acid analyses can help to resolve this problem. The mesopelagic fish examined in this study were collected from the continental slope in the north of the South China Sea (SCS), and are compared with nearshore SCS fish and fish collected from the Southern Ocean. The unusually high lipid content of the mesopelagic fish resulted in △δ13C values (i.e., the difference in δ13C between unextracted and extracted tissues) exceeding 1‰, which is more than the enrichment factor in the food web. Thus, extraction of lipids was conducted prior to δ13C isotope analysis for the study of trophic interactions of mesopelagic fish. Compared with other fish, mesopelagic fish had high C18:1n-9/C18:1n-7 and C20:1n-9/ C18:1n-7 ratios, which confirms that plankton is their main dietary source. Diatoms comprise a higher proportion of phytoplankton in the Southern Ocean and a lower proportion in the SCS, and this is reflected in the C20:5n-3/C22:6n-3 (EPA/DHA) ratio in mesopelagic fish in each region. The low EPA/DHA ratio in SCS fish indicates that diatoms are not the main component in the diet of mesopelagic fish. The SCS mesopelagic fish had higher C20:4n-6/C22:6n-3 (ARA/DHA) and C20:4n-6/C20:5n-3 (ARA/EPA) ratios than fish in the Southern Ocean. This result suggests that physical factors (e.g., temperature) also affect the fatty acid composition of these fish, particularly because certain fatty acids enable the fish to better adapt to extreme environmental conditions. Future studies of the synthesis of fatty acids in particular species should take account of both the dietary sources and physical factors in their environment.

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Lipid and fatty acid composition of the mantle and digestive gland of four Southern Ocean squid species: implications for food-web studies

Antarctic Science ◽

10.1017/s0954102002000044 ◽

2002 ◽

Vol 14 (3) ◽

pp. 212-220 ◽

Cited By ~ 43

Author(s):

KATRINA L. PHILLIPS ◽

PETER D. NICHOLS ◽

GEORGE D. JACKSON

Keyword(s):

Fatty Acid Composition ◽

Fatty Acid ◽

Southern Ocean ◽

Lipid Class ◽

Digestive Gland ◽

Acid Composition ◽

Lipid Content ◽

Mantle Tissue ◽

Dietary Analysis ◽

The Absolute

Lipid content, lipid class and fatty acid composition of four Southern Ocean cephalopod species – the myopsid Sepioteuthis australis and three oegopsids, Gonatus antarcticus, Moroteuthis robsoni and Todarodes spp. – were analysed. The lipid content of the digestive gland was consistently greater than that of the mantle, and was an order of magnitude greater in oegopsid species. The lipid class and fatty acid composition of the mantle and digestive gland also differed markedly in each species. Digestive gland lipid is likely to be of dietary origin, and large amounts of lipid in the digestive gland of oegopsids may accumulate over time. Thus the digestive gland is a rich source of fatty acid dietary tracers and may provide a history of dietary intake. However, the absolute amount of dietary lipid in the digestive gland of oegopsid species exceeds the absolute lipid content of mantle tissue. Therefore the overall lipid “signature” of an oegopsid may more closely resemble its prey species rather than its mantle tissue. When lipid techniques are used in dietary analysis of teuthophagous predators, squid may not be represented by a unique signature in analyses and their importance in the diets of predators may be underestimated.

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