Journal article Open Access

The First Cut Is the Deepest: Trawl Effects on a Deep-Sea Sponge Ground Are Pronounced Four Years on

Morrison, Katelin M; Meyer, Heidi Kristina; Roberts, Emyr Martyn; Rapp, Hans Tore; Colaço, Ana; Pham, Christopher Kim


Few studies have described the effects of physical disturbance and post-recovery of deep-sea benthic communities. Here, we explore the status of deep-sea sponge ground communities four years after being impacted by an experimental bottom trawl. The diversity and abundance of epibenthic megafauna of two distinct benthic communities in disturbed versus control areas were surveyed using a remotely operated vehicle on the Schulz Bank, Arctic Ocean. Four years after disturbance, megafaunal densities of the shallow (∼600 m depth) and deep (∼1,400 m depth) sites were significantly lower on the disturbed patches compared to the control areas. Multivariate analyses revealed a distinct separation between disturbed and control communities for both sites, with trawling causing 29–58% of the variation. Many epibenthic morphotypes were significantly impacted by the trawl, including ascidians, Geodia parva, Hexactinellida spp., Craniella infrequensLissodendoryx complicataHaliclonia sp. Stylocordyla borealisGersemia rubiformis and Actiniaria sp. However, we found some smaller morphospecies to be equally abundant with control transects, including Polymastia thieleiGeodia hentscheli, and Stelletta rhaphidiophora, reflecting lower trawl impact for these morphotypes. Overall, our results suggest that these are fragile ecosystems that require much more time than four years to recover from physical disturbance typical of trawling activities.

ACKNOWLEDGEMENTS Thanks are due to the SponGES team for their guidance, advice on our study design, and help with epifaunal morphospecies identification in the image data. Thanks to the IMAR staff for providing office space and resources. And thanks to the G.O.Sars crew, AEGIR6000 crew, and science team that carried out the ROV surveys. Finally, we would like to dedicate this contribution to our friend and colleague Hans Tore Rapp. AUTHOR CONTRIBUTIONS CP and KM conceived and carried out the study. HM, ER, and HR advised on identification of species and analysis methods. KM analyzed the data, wrote the manuscript, and prepared the figures. All authors revised drafts of the manuscript and gave final approval for publication. SUPPLEMENTARY MATERIAL The Supplementary Material for this article can be found online at: CONFLICT OF INTEREST STATEMENT The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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