Sources, quality and transfers of organic matter in a highly-stratified sub-Arctic coastal system (Saint-Pierre-et-Miquelon, NW Atlantic)

Type Article
Date 2021-01
Language English
Author(s) Bridier Guillaume1, Meziane Tarik2, Grall Jacques1, 3, Chauvaud Laurent1, Donnet Sebastien4, Lazure PascalORCID5, Olivier Frédéric2, 6
Affiliation(s) 1 : Laboratoire des Sciences de l'Environnement Marin (LEMAR) UMR 6539 UBO/CNRS/IRD/Ifremer, rue Dumont D’Urville, 29280 Plouzane, France
2 : Biologie des Organismes et Écosystèmes Aquatiques (BOREA) UMR 7208 MNHN/SU/UNICAEN/UA/CNRS/IRD, 61 Rue Buffon CP53, 75005 Paris, France
3 : Observatoire Marin, UMS 3113, Institut Universitaire Européen de la Mer, rue Dumont D’Urville, 29280 Plouzané, France
4 : Northwest Atlantic Fisheries Center, Fisheries and Oceans Canada, P.O. Box 5667, St John’s, Newfoundland and Labrador (NL), A1C 5X1, Canada
5 : Ifremer, Laboratoire d’Océanographie Physique et Spatiale, Institut Universitaire Européen de la Mer, Plouzané, France
6 : Station Marine de Concarneau, Muséum National d’Histoire Naturelle, Place de la Croix, 29900 Concarneau, France
Source Progress In Oceanography (0079-6611) (Elsevier BV), 2021-01 , Vol. 190 , P. 102483 (13p.)
DOI 10.1016/j.pocean.2020.102483
Keyword(s) Pelagic-benthic coupling, Seasonal stratification, Organic matter, Fatty acids, Stable isotopes, Subarctic ecosystems, Saint-Pierre et Miquelon archipelago, Newfoundland shelf

In response to ongoing global climate change, marine ecosystems in the northwest Atlantic are experiencing one of the most drastic increases in sea surface temperatures in the world. This warming can increase water column stratification and decrease surface nutrient concentrations, in turn impacting primary productivity and phytoplankton assemblages. However, the exact impacts of these changes on sources and quality of organic matter as well as its transfers to the benthic compartment remain uncertain. This survey characterized organic matter sources and quality within a highly-stratified sub-Arctic coastal system (Saint-Pierre and Miquelon) and described its transfer towards a biomass-dominant primary consumer, the sand dollar Echinarachnius parma. This study analyzed fatty acid and stable isotope (δ13C and δ15N) composition of surface and bottom Particulate Organic Matter (s-POM and b-POM, respectively), Sedimentary Organic Matter (SOM) and sand dollar tissue along a near shore to offshore gradient during two contrasting seasons associated either with sharp or weak water column stratification (i.e. High vs Low Stratification Periods). Results revealed high relative abundances of polyunsaturated fatty acids (notably macro- and microalgae markers) in POM during the Low Stratification Period while the High Stratification Period was characterized by elevated relative abundance of saturated fatty acids indicating a higher organic matter degradation state. In addition, strong seasonal differences were also observed in food availability with four-fold higher concentrations in total suspended solids during Low vs High Stratification Periods. These results suggested thus multiple negative effects of stratification on pelagic-benthic coupling and POM quality. Lower nutrient repletion of surface waters during period of sharp stratification diminishes pelagic-benthic coupling by reducing food availability, POM quality and vertical transfer of organic matter. By contrast, the sediment-based diet of E. parma showed a low spatiotemporal variability reflecting the homogenous composition of the SOM. This study suggests that intensified water column stratification due to increasing sea surface temperatures may modify the pelagic-benthic coupling and future quality and composition of POM pools.

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Bridier Guillaume, Meziane Tarik, Grall Jacques, Chauvaud Laurent, Donnet Sebastien, Lazure Pascal, Olivier Frédéric (2021). Sources, quality and transfers of organic matter in a highly-stratified sub-Arctic coastal system (Saint-Pierre-et-Miquelon, NW Atlantic). Progress In Oceanography, 190, 102483 (13p.). Publisher's official version : , Open Access version :