Synthesis of the state of knowledge about species richness of macroalgae, macroinvertebrates and fishes in coastal and oceanic waters of Easter and Salas y Gomez islands

Abstract

ABSTRACT. From the beginning of the 19th century on, several small sampling trips as well as large national and international scientific expeditions have been carried out to Easter Island (EI) and Salas y Gómez Island (SGI). The objective of this study is to compile, synthesize and analyze published information about the biodiversity of macroalgae, macroinvertebrates and fishes associated with EI-SGI, updating the state of knowledge and making it available for the development of conservation plans. We searched all the available sources of information, such as scientific publications, scientific expeditions, fisheries data, technical reports, books, databases and online sources. We found 964 species reported within EI-SGI (143 species of macroalgae, 605 macroinvertebrates and 216 fishes), the majority for EI (923); for SGI 171 species have been reported. Species richness has increased over time, without leveling off, as sampling effort increases. However, seamounts and hydrothermal vents have been poorly studied in Chile´s Exclusive Economic Zone (EEZ). A high percentage of endemism has been determined for the majority of the taxonomic groups, with mollusks and poriferans exhibiting the highest levels of endemism (33-34%). Thus, the Rapanuian biogeographic province can be clearly identified, but information to differentiate between EI and SGI, and direct island-specific conservation efforts, is lacking. Nevertheless, the most vulnerable yet unprotected habitats (hydrothermal vents, higher diversity of seamounts size) are located towards the western limit of the EEZ.

Overview of recent advances in oceanographic, ecological and fisheries research on oceanic islands in the southeastern Pacific Ocean

“…This low sampling effort explains why the species richness of seamounts inside the EEZ is only 7% of that found on seamounts near Salas y Gómez Island, outside the EEZ . The same pattern is found when analysing different taxa individually (7.4% fishes, 2.6% for crustaceans; in Fernández et al, 2014, estimated from Parin et al, 1997Stocks, 2009;Friedlander et al, 2013). These results show how little we currently know about biodiversity on seamounts.…”

“…Only during the last decade were conducted the first explorations to characterize the biodiversity of marine communities associated with seamounts in the Juan Fernández Archipelago (Yañez et al, 2009) and Salas y Gómez Island (Friedlander et al, 2013). Although we highlight these contributions within the EEZ of Chile, the review by Fernández et al (2014) suggests that sampling effort is still poor for this area. This low sampling effort explains why the species richness of seamounts inside the EEZ is only 7% of that found on seamounts near Salas y Gómez Island, outside the EEZ .…”

“…Fernández et al (2014) compiled, synthesized and analyzed published information about the biodiversity of macroalgae, macroinvertebrates and fishes associated with Easter and Salas y Gómez islands, advancing the characterization of this biogeographic province. Species richness in Eastern Island has increased over time, as sampling effort has increased, suggesting that more studies are needed to characterize marine biodiversity even in the most studied areas and even for conspicuous groups, such as seabirds .…”

“…Easter and Salas y Gómez region shows higher species richness of mollusks, fishes and total (all taxa) than the Juan Fernández Archipelago, although only 6.4% of the species are shared, suggesting a different colonization origin between both groups of oceanic islands . However, when compared with other oceanic Pacific islands, species richness is low (e.g., fish; Fernández et al, 2014, based on Randall & Cea, 2011, which is explained by a combination of factors, including the geological age of the island (relatively young), the low diversity of habitats, and the location at intermediate latitudes. Species richness of seabirds and marine mammals is also low, most likely related to the small sampling effort directed towards these conspicuous groups.…”

“…than in Salas y Gómez Island (16 spp. ; Flores et al, 2014;Fernández et al, 2014, for other taxa). Easter and Salas y Gómez islands share a significant number of species of birds while fewer species are shared between Salas y Gómez and Desventuradas islands, supporting the hypothesis that Desventuradas Islands belong to a different biogeographic province and that the waters surrounding Easter and Salas y Gómez islands can be considered a single biogeographic province.…”