Abstract

Seamounts and oceanic islands of the Chilean Exclusive Economic Zone at the intersection of the Nazca and Salas y Gómez ridges lie within one of the least explored areas in the world. The sparse information available, mainly for seamounts outside Chilean jurisdiction and shallow-water fauna of the Desventuradas Islands, suggests that the area is a hotspot of endemism. This apparent uniqueness of the fauna motivated the creation of the large Nazca-Desventuradas Marine Park (NDMP, ~ 300,000 km2) around the small islands San Felix and San Ambrosio in 2015. We report for the first time a detailed description of benthic microhabitats (i.e., centimeter to meter scale), macrohabitats (i.e., meter to kilometer-scale) and associated megafauna within the NDMP. Descriptions were based on analysis of fauna collected by trawling and ROV video observations from ~ 50 to 370 m depth. Rocky, coarse sand and silty sediment bottom habitats were observed at island slopes. In contrast, rocky and coarse sandy bottom habitats with a predominance of rhodoliths, thanatocoenosis, and other biogenic components were observed at seamounts. Mobile fauna and predators dominated the oceanic islands and nearby seamounts, whereas seamounts farther from the islands were dominated by sessile and hemisessile fauna that were mainly suspension and deposit feeders. Based on the register of 118 taxonomic units, our results provide an expanded and updated baseline for the benthic biodiversity of NDMP habitats, which seemed pristine, without evidence of trawling or anthropogenic debris.

Highlights

  • IntroductionDespite studies being conducted on SGR and NR s­ eamounts[15, 17,18,19], only one of the many seamounts within the Chilean EEZ adjacent to the Desventuradas Islands (San Felix and San Ambrosio islands) has been investigated

  • To explore relationships among micro- and macrohabitats and the fauna living on the summit of the seamounts and upper slope of oceanic islands of the Nazca Desventuradas Marine Park (NDMP), we describe the benthic habitats and associated fauna of the upper slope (50–370 m) of Desventuradas Islands and the summits and upper slopes (150–305 m) of seven nearby seamounts

  • We are aware of the limitations of the present study, we consider that our information presents a fundamental base-line knowledge of the benthic fauna and environment in this relatively understudied region of the Pacific Ocean, with a high value for conservation

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Summary

Introduction

Despite studies being conducted on SGR and NR s­ eamounts[15, 17,18,19], only one of the many seamounts within the Chilean EEZ adjacent to the Desventuradas Islands (San Felix and San Ambrosio islands) has been investigated In addition to this seamount, known as Stockman G­ uyot[11, 15], the Desventuradas Islands were studied on two expeditions: Marine Research Cruises in Remote Areas (CIMAR 6) conducted by the National Oceanographic Committee of Chile (CONA) in 2001 and the "Pristine Seas Expedition" carried out by the National Geographic Society and Oceana in 2013. The heterogeneity and topographic complexity of seamounts is affected by the presence of organisms that can change spatial conditions and, directly or indirectly, affect the availability of habitat and resources for other ­species[25] These organisms are called habitat-forming species and are characterized by being small-scale engineers of autogenous ecosystems. Microhabitats operate at centimeters and smaller scales and include seafloor features such as sand, silt, gravel, pebbles, small cracks, crevices and f­ractures[31, 32]

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