Dark CO2 fixation into phospholipid-derived fatty acids by the cold-water coral associated sponge Hymedesmia (Stylopus) coriacea (Tisler Reef,NE Skagerrak) |
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Authors: | Fleur C van Duyl Sabine K Lengger Stefan Schouten Tomas Lundälv Dick van Oevelen Christina E Müller |
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Institution: | 1. Department of Marine Microbiology and Biogeochemistry, Royal Netherlands Institute for Sea Research (NIOZ-Texel) and Utrecht University, Texel, Netherlandsfleur.van.duyl@nioz.nl;3. School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, UK;4. Department of Marine Microbiology and Biogeochemistry, Royal Netherlands Institute for Sea Research (NIOZ-Texel) and Utrecht University, Texel, Netherlands;5. Sven Lovén Centre for Marine Sciences, Tj?rn?, University of Gothenburg, Str?mstad, Sweden;6. Department of Estuarine and Delta Systems, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), Utrecht University, Yerseke, Netherlands |
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Abstract: | ABSTRACTMany cold-water sponges harbour microorganisms of which the role in the sponge host remains enigmatic. Here, we show a transfer of fixed inorganic carbon by sponge-associated microbes to its host, the cold-water coral encrusting sponge Hymedesmia (Stylopus) coriacea. Sponge were collected at approx. 100?m depth and incubated for 1.5–2.5 days with 13C labelled dissolved inorganic carbon (DIC) as tracer. Total DIC fixation rates ranged from 0.03–0.11?mmol C?×?mmol Csponge × d?1. 13C-tracer was recovered in bacterial-specific (i.e. short and branched) and sponge-specific (very long-chained) phospholipid-derived fatty acids (PLFA's), but was not incorporated into archaeal lipids. 13C-incorporation in biomarkers such as C16:1w7c and C18:1w7c indicated that nitrifying and/or sulphur-oxidizing bacteria (chemoautotrophs) were likely active in the sponge. Trophic transfer of microbially-fixed carbon to the sponge host was confirmed by recovery of label in very long chain fatty acids (VLCFA's) including C26:2 and C26:3. Tracer accumulation into several VLCFA's continued after removal of 13C-DIC, while tracer in most bacteria-specific PLFA's declined, indicating a transfer and elongation of bacterial-specific PLFA's to sponge-specific PLFA's. This implies that PLFA precursors released from chemo- as well as heterotrophic microbes in sponges contributed to the synthesis of VLCFA's, identifying sponge-associated bacteria as symbionts of the sponge. |
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