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Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis

Marleen De Troch (UGent) , Pascal Boeckx (UGent) , Clio Cnudde (UGent) , Dirk Van Gansbeke (UGent) , Ann Vanreusel (UGent) , Magda Vincx (UGent) and Maria José Caramujo
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Biotechnology for a sustainable economy (Bio-Economy)
Abstract
Polyunsaturated fatty acids (PUFA) are essential compounds that can limit the productivity of primary consumers in aquatic food webs, where the efficiency in energy transfer at the plant-animal interface has been related to food quality in terms of fatty acids (FA). At this interface, copepods play a pivotal role both as consumers of primary production and as a food source for higher trophic levels. Understanding the role of grazing copepods in the transfer of FA is therefore essential for our knowledge on the overall functioning of marine ecosystems. The harpacticoid copepod Microarthridion littorale grazed for 9 d on C-13 labelled diatoms and bacteria in the laboratory and was then subjected to FA-specific stable isotope analysis. The objective of this analysis was to inspect the copepod's ability to bioconvert short-chain FA (SC-PUFA, <20 carbons) into long-chain PUFA (LC-PUFA, >= 20 carbons) and the FA involved in the potential bioconversion pathways. Diatoms and bacteria were chosen as test diets because of their different FA composition, i.e. docosahexaenoic acid (DHA; 22: 6 omega 3) was absent in the bacteria, and eicosapentaenoic acid (EPA; 20: 5 omega 3) was <5% of the total FA weight of bacteria. The presence of labelled DHA in copepods feeding on bacteria showed that this PUFA must have been converted from other FA, possibly EPA. The FA composition of copepods in the laboratory was different from that of field copepods, which suggests the availability of more food sources in the field than those offered in the experiment. The weight proportion of C18 FA decreased in copepods feeding on either bacteria or diatoms relative to field copepods, while the proportion of both EPA and DHA increased. In contrast to planktonic calanoid copepods that have limited ability to bioconvert FA, benthic harpacticoid copepods apparently developed the ability to elongate FA and to exploit niches with poor quality food. Moreover, by improving the quality of the food they graze upon, especially in terms of EPA and DHA, harpacticoid copepods upgrade the nutritive value of food available to the higher trophic levels in marine food webs.
Keywords
Fatty acids, Bioconversion, Harpacticoid copepods, Compound-specific stable isotope analysis, MEIOBENTHIC HARPACTICOID COPEPODS, LIVE FOOD, EICOSAPENTAENOIC ACID, COMMUNITY STRUCTURE, TROPHIC MARKERS, FISH LARVAE, BACTERIA, CARBON, BIOSYNTHESIS, DIATOM

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Citation

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Chicago
De Troch, Marleen, Pascal Boeckx, Clio Cnudde, Dirk Van Gansbeke, Ann Vanreusel, Magda Vincx, and Maria José Caramujo. 2012. “Bioconversion of Fatty Acids at the Basis of Marine Food Webs: Insights from a Compound-specific Stable Isotope Analysis.” Marine Ecology-progress Series 465: 53–67.
APA
De Troch, Marleen, Boeckx, P., Cnudde, C., Van Gansbeke, D., Vanreusel, A., Vincx, M., & Caramujo, M. J. (2012). Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis. MARINE ECOLOGY-PROGRESS SERIES, 465, 53–67.
Vancouver
1.
De Troch M, Boeckx P, Cnudde C, Van Gansbeke D, Vanreusel A, Vincx M, et al. Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis. MARINE ECOLOGY-PROGRESS SERIES. 2012;465:53–67.
MLA
De Troch, Marleen, Pascal Boeckx, Clio Cnudde, et al. “Bioconversion of Fatty Acids at the Basis of Marine Food Webs: Insights from a Compound-specific Stable Isotope Analysis.” MARINE ECOLOGY-PROGRESS SERIES 465 (2012): 53–67. Print.
@article{3068984,
  abstract     = {Polyunsaturated fatty acids (PUFA) are essential compounds that can limit the productivity of primary consumers in aquatic food webs, where the efficiency in energy transfer at the plant-animal interface has been related to food quality in terms of fatty acids (FA). At this interface, copepods play a pivotal role both as consumers of primary production and as a food source for higher trophic levels. Understanding the role of grazing copepods in the transfer of FA is therefore essential for our knowledge on the overall functioning of marine ecosystems. The harpacticoid copepod Microarthridion littorale grazed for 9 d on C-13 labelled diatoms and bacteria in the laboratory and was then subjected to FA-specific stable isotope analysis. The objective of this analysis was to inspect the copepod's ability to bioconvert short-chain FA (SC-PUFA, {\textlangle}20 carbons) into long-chain PUFA (LC-PUFA, {\textrangle}= 20 carbons) and the FA involved in the potential bioconversion pathways. Diatoms and bacteria were chosen as test diets because of their different FA composition, i.e. docosahexaenoic acid (DHA; 22: 6 omega 3) was absent in the bacteria, and eicosapentaenoic acid (EPA; 20: 5 omega 3) was {\textlangle}5\% of the total FA weight of bacteria. The presence of labelled DHA in copepods feeding on bacteria showed that this PUFA must have been converted from other FA, possibly EPA. The FA composition of copepods in the laboratory was different from that of field copepods, which suggests the availability of more food sources in the field than those offered in the experiment. The weight proportion of C18 FA decreased in copepods feeding on either bacteria or diatoms relative to field copepods, while the proportion of both EPA and DHA increased. In contrast to planktonic calanoid copepods that have limited ability to bioconvert FA, benthic harpacticoid copepods apparently developed the ability to elongate FA and to exploit niches with poor quality food. Moreover, by improving the quality of the food they graze upon, especially in terms of EPA and DHA, harpacticoid copepods upgrade the nutritive value of food available to the higher trophic levels in marine food webs.},
  author       = {De Troch, Marleen and Boeckx, Pascal and Cnudde, Clio and Van Gansbeke, Dirk and Vanreusel, Ann and Vincx, Magda and Caramujo, Maria Jos{\'e}},
  issn         = {0171-8630},
  journal      = {MARINE ECOLOGY-PROGRESS SERIES},
  keyword      = {Fatty acids,Bioconversion,Harpacticoid copepods,Compound-specific stable isotope analysis,MEIOBENTHIC HARPACTICOID COPEPODS,LIVE FOOD,EICOSAPENTAENOIC ACID,COMMUNITY STRUCTURE,TROPHIC MARKERS,FISH LARVAE,BACTERIA,CARBON,BIOSYNTHESIS,DIATOM},
  language     = {eng},
  pages        = {53--67},
  title        = {Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis},
  url          = {http://dx.doi.org/10.3354/meps09920},
  volume       = {465},
  year         = {2012},
}

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