Dissolved organic carbon (DOC) is essential to balance the metabolic demands of North-Atlantic deep-sea sponges

• Main Authors: Bart, Martijn C, Mueller, Benjamin, Rombouts, Titus, van de Ven, Clea, Tompkins, Gabrielle J, Osinga, Ronald, Brussaard, Corina PD, MacDonald, Barry, Engel, Anja, Rapp, Hans Tore, de Goeij, Jasper M
• Format: Report
• Language: unknown
• Published: 2020
• Subjects: Deep-sea sponge grounds; demosponge; hexactinellid; respiration; carbon budget; DOC; ex situ incubation; European Union (EU); Horizon 2020; Grant Agreement No 679849; Deep-sea Sponge Grounds Ecosystems of the North Atlantic: an integrated approach towards their preservation and sustainable exploitation; SponGES; Bedford; Bergen; Canada; Norway; North Atlantic
• Online Access: https://zenodo.org/record/4293853; https://doi.org/10.1101/2020.09.21.305086

ABSTRACT Sponges are ubiquitous components of various deep-sea habitats, including cold water coral reefs and deep-sea sponge grounds. Despite being surrounded by oligotrophic waters, these ecosystems are known to be hotspots of biodiversity and carbon cycling. To assess the role of sponges in the carbon cycling of deep-sea ecosystems, we studied the energy budgets of six dominant deep-sea sponges (the hexactinellid species Vazella pourtalesi, and demosponge species Geodia barretti, Geodia atlantica, Craniella zetlandica, Hymedesmia paupertas and Acantheurypon spinispinosum) in an ex situ aquarium setup. Additionally, we determined morphological metrics for all species (volume, dry weight (DW), wet weight (WW), carbon (C) content, and ash-free dry weight (AFDW)) and provide species-specific conversion factors. Oxygen (O2) removal rates averaged 3.3 ± 2.8 µmol O2 DWsponge h−1 (all values mean ± SD), live particulate (bacterial and phytoplankton) organic carbon (LPOC) removal rates averaged 0.30 ± 0.39 µmol C DWsponge h−1 and dissolved organic carbon (DOC) removal rates averaged 18.70 ± 25.02 µmol C DWsponge h−1. Carbon mass balances were calculated for four species (V. pourtalesi, G. barretti, G. atlantica and H. paupertas) and revealed that the sponges acquired 1.3–6.6 times the amount of carbon needed to sustain their minimal respiratory demands. These results indicate that irrespective of taxonomic class, growth form, and abundance of microbial symbionts, DOC is responsible for over 90 % of the total net organic carbon removal of deep-sea sponges and allows them to sustain in otherwise food-limited environments on the ocean floor. ACKNOWLEDGEMENTS We thank all our collaborators at the EU Horizon 2020 SponGES project; Dr. Ellen Kenchington at the Bedford Institute of Oceanography (BIO), Nova Scotia, Canada, and the Department of Biological Sciences at the University of Bergen, Norway, for the use of facilities and equipment. Many thanks to the ROV crews of both the ÆGIR 6000 in Norway and the Deep Sea Systems ...