Deep-sea biodiversity at the extremes of the Salas y Gómez and Nazca ridges with implications for conservation

RESEARCH ARTICLE Deep-sea biodiversity at the extremes of the Salas y Go ´mez and Nazca ridges with implications for conservation Alan M. FriedlanderID1,2*, Whitney Goodell1,3, Jonatha GiddensID3, Erin E. Easton4,5, Daniel Wagner6 1 Pristine Seas, National Geographic Society, Washington, DC, United States of America, 2 Hawaiʿi Institute of Marine Biology, University of Hawaiʿi, Kāne‘ohe, Hawaiʿi, United States of America, 3 Exploration Technology Lab, National Geographic Society, Washington, DC, United States of America, 4 Ecology and Sustainable Management of Oceanic Islands, Universidad Cato´ lica del Norte, Coquimbo, Chile, 5 School of Earth, Environmental, and Marine Sciences, University of Texas Rio Grande Valley, Brownsville, Texas, United States of America, 6 Conservation International, Center for Oceans, Arlington, VA, United States of America * alan.friedlander@hawaii.edu Abstract The Salas y Go´ mez and Nazca ridges are underwater mountain chains that stretch across 2,900 km in the southeastern Pacific and are recognized for their high biodiversity value and unique ecological characteristics. Explorations of deep-water ecosystems have been limited in this region, and elsewhere globally. To characterize community composition of mesopho- tic and deep-sea demersal fauna at seamounts in the region, we conducted expeditions to Rapa Nui (RN) and Salas y Go´ mez (SyG) islands in 2011 and Desventuradas Islands in 2013. Remote autonomous baited-cameras were used to conduct stationary video surveys

between 150–1,850 m at RN/SyG (N = 20) and 75–2,363 m at Desventuradas (N = 27). Indi- vidual organisms were identified to the lowest possible taxonomic level and relative abun- dance was quantified with the maximum number of individuals per frame. Deployments were attributed with associated environmental variables (temperature, salinity, dissolved oxygen, nitrate, silicate, phosphate, chlorophyll-a, seamount age, and bathymetric position index [BPI]). We identified 55 unique invertebrate taxa and 66 unique fish taxa. Faunal com- munity structure was highly dissimilar between and within subregions both for invertebrate (p < 0.001) and fish taxa (p = 0.022). For fishes, dogfish sharks (Squalidae) accounted for the greatest dissimilarity between subregions (18.27%), with mean abundances of 2.26 ± 2.49 at Desventuradas, an order of magnitude greater than at RN/SyG (0.21 ± 0.54). Depth, seamount age, broad-scale BPI, and nitrate explained most of the variation in both inverte- brate (R2 = 0.475) and fish (R2 = 0.419) assemblages. Slightly more than half the deploy- ments at Desventuradas (N = 14) recorded vulnerable marine ecosystem taxa such as corals and sponges. Our study supports mounting evidence that the Salas y Go´ mez and Nazca ridges are areas of high biodiversity and high conservation value. While Chile and Peru have recently established or proposed marine protected areas in this region, the major- ity of these ridges lie outside of national jurisdictions and are under threat from overfishing,

plastic pollution, climate change, and potential deep-sea mining. Given its intrinsic value, PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0253213 June 30, 2021 1 / 27 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Friedlander AM, Goodell W, Giddens J, Easton EE, Wagner D (2021) Deep-sea biodiversity at the extremes of the Salas y Go´mez and Nazca ridges with implications for conservation. PLoS ONE 16(6): e0253213. https://doi.org/10.1371/ journal.pone.0253213 Editor: Jeffrey A. Eble, Florida Institute of Technology, UNITED STATES Received: February 1, 2021 Accepted: May 29, 2021 Published: June 30, 2021 Copyright: © 2021 Friedlander et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Our data are publicly available at Data Dryad: doi.org/10.5061/dryad. c866t1g6j. Funding: The expeditions were funded by the National Geographic Society and Pristine Seas donors with support to AMF. Conservation International, the Paul M. Angell Family Foundation, Tom and Currie Barron, and Alan Eustace provided additional support to DW, WG and JG. The Chilean Millennium Science Initiative Program grant #NC120030 provided support to EEE. The funders