Abstract
Many 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.
Original language | English |
---|---|
Pages (from-to) | 1-17 |
Number of pages | 17 |
Journal | Marine Biology Research |
Volume | 16 |
Issue number | 1 |
DOIs | |
Publication status | Published - 8 Jan 2020 |
Funding
Support was given by the European Community for the access provided at the Sven Lovén Centre for Marine Sciences, Tjärnö, Sweden (ASSEMBLE grant agreement no. 227799). We thank the local technical and administrative staff for assistance and logistic support during the sponge experiments in Sweden. Karel Bakker, Santiago Gonzalez, Richard Doggen and Kirsten Kooijman and Jort Ossebaar of NIOZ-Texel are thanked for their analyses of inorganic nutrients, dissolved organic matter analyses, bacterial abundance and bulk stable isotope analyses. The analytical lab of NIOZ-Yerseke is thanked for PLFA analyses.