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Colonial life under the Humboldt current system: deep-sea corals from O'Higgins I seamount/La vida colonial bajo el sistema de la corriente de Humboldt: corales de aguas profundas en el monte submarino O'Higgins I.

Approximately half of the described coral species inhabit deep, cold and dark waters and their study represents cutting-edge research worldwide (Roberts & Hirshfield, 2004). Their bathymetric distribution down over 200 m complicates their study. Thus, their biology and the role played in the deep-water ecosystem is poorly understood (Andrews et al., 2002). Studies showed that coral associations form a habitat for many invertebrate and vertebrate species of commercial value (Alper, 1998); among them the alfonsino (Beryx splendens) and orange roughy (Hoplostethus atlanticus) (Yanez et al., 2009). Along the Chilean coast, the role that these communities could play at seamounts and along the continental margins is still unknown (Koslow et al., 2001; Levin, 2002), but recent efforts began to discover evidence of deep corals in the southeastern Pacific coast (Haussermann & Forsterra, 2007a).

During an international cruise, performed in December, 2004 to O'Higgins I seamount (Fig. 1), an important evidence of the presence of massive colonial life on the plateau was recorded (Fig. 2). These findings represent a very important discovery because attention in Chilean benthic research has been focused on sublittoral communities such as the continental shelf and slope (Gallardo, 1977; Gallardo et al., 1994, 1996, 2004; Palma et al., 2005; Quiroga et al., 2009; Sellanes et al., 2010). In the present study we demonstrate with graphic evidence that under the Humboldt Current System, some seamount have important assemblages of deep-water corals, showing as for example, the O'Higgins I seamount. This biotope, its fauna and the functional relationships could stimulate new research opportunities around seamounts off the Chilean coast. Features of the colonial life are indeterminate growth, reproduction through fission and budding, slow growth, suspension-feeding or micro-carnivorous and an evident functional specialization of different individuals within a colony (Jackson, 1985).

This paper represents the first reference on only one large colonial assemblages generating habitat for others non-colonial species, still unknown marine benthic species collected on the O'Higgins I seamount, off central Chile.

Sampling was conducted in December, 29, 2004, with a bottom traw net (50 mm mesh size and approx. 30 m width), 74 min of bottom trawling, during the Chilean-Japanese cruise onboard R/V "Koyo Maru" on the plateau of the O'Higgins I seamount, off central Chile (start position: 32[degrees]54.3'S, 73[degrees]55.4'W; final position: 32[degrees]54.2'S, 73[degrees]52.8'W) (Fig. 1) (Zuleta & Hamano, 2004; Hamano, pers. comm.). The deep-sea coral material was collected (Fig. 2), including the megafauna associated (>40 mm). Dry coral samples were sent to specialists for their identification: Dr. Dennis Opresko (Antipatharia and Paragorgiidae) and Dr. Juan Sanchez (Isididae). The height of some complete coral specimens was measured to estimate their importance as habitat.

Further sampled marine invertebrates were identified using Andrade (1986) and specialized literature on echinoids (Antarctic Invertebrates Catalogue of Smithsonian Institution; http://inver tebrates.si.edu) and Chilean crustaceans (Retamal, 2000).

The water column above the seamount was stratified, and had a mixed layer of approx. 40 m depth. The temperature ranged between 17.7[degrees]C (surface) and 5.6[degrees]C (bottom; 820 m), salinity varied between 34.31 (surface) and 34.586 psu (200 m). Oxygen levels varied widely throughout the water column, averaging 5.2 mL [O.sub.2] [L.sup.-1] at the surface and decreasing to <0.5 mL [O.sub.2] [L.sup.-1] between 130 and 280 m depth. Scarce oxygen levels reflect the influence of the Equatorial Subsurface Water (ESSW) associated to an oxygen-minimum zone (OMZ). Below this layer, the Antarctic Intermediate Water (IAW) is responsible for low temperatures and higher oxygen levels, which increased to a maximum of almost 4 mL [O.sub.2] [L.sub.-1] around 550 m depth (Chiang & Quinones, 2007). On the summit of O'Higgins I seamount (400 to 500 m depth), oceanographic conditions were: temperatures from 5.8 to 6.9[degrees]C, dissolved oxygen from 2 to 3 mL [O.sub.2] [L.sup.-1] and the salinity [approximately equal to]34.3 psu (Chiang & Quinones, 2007).

A total of 220 colonies or sections were collected in a single bottom trawling (Fig. 2), belonging to five species, four of which are described and photographed in this paper (Figs. 3a and 3d). The collected deep-sea corals were identified as: Leiopathes sp. (Fig. 3a), belonging to family Leiopathidae Haeckel, 1896 and Chrysopathes sp. (Fig. 3b) belonging to family Cladopathidae Brook, 1889, both are members of the subclass Hexacorallia, Order Antipatharia (black corals). The genus Crysopathes was established by Opresko (2003). The other two species belong to the subclass Octocorallia and are Acanella chilensis (Fig. 3c) and an unidentified member of the family Paragorgidae (Fig. 3d). The most abundant subclass was Hexacorallia (75%).

The rest of megafauna were constituted by six species of crustaceans Heterocarpus reedi (n = 330), Projasus bahamondei (n = 130), Munida propinqua (n = 8), Uroptychus parvulus (abundance no recorded), Chirostylus hendersoni (n = 32) and the stomatopod Pterygosquilla armata (n = 47), two species of ophiuroids (Gorgonocephalus chilensis and Astrotoma agassizi; n = 14 and 102, respectively), an unknown species of asteroid (n = 1) and one species of Anthozoa Hormathia cf. pectinata (n = 2).

Deep-water corals of the O'Higgins I seamount can provide crucial habitat and reproductive grounds for commercially and potential important mid water resources such as the fish orange roughy (Hoplostethus atlanticus) and alfonsino (Beryx splendens) and crustaceans such as the nylon shrimp (Heterocarpus reedi) and the deep-sea tiny lobster (Projasus bahamondei). The most significant finding of this study was the capture of the atypical sea urchin Dermechinus horridus (Cactus sea urchin; 30 cm length; n = 28), which has been previously collected near the Southern Pacific Polar Front (B. David, pers. comm.) and recently in a new seep site over the upper slope off central Chile (J. Sellanes, pers. comm.). Thus, the biogeographic origin of the collected fauna evidenced a mix of species from Sub Antarctic and central Chilean continental margin (Sellanes et al., 2008; Haussermann & Forsterra, 2009).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

These colonial deep-sea corals are fragile due to their slow growth, they are micro carnivorous, suspension-feeders and play an important role for benthic fauna as substrate, mostly for larger ophiuroids G. chilensis and A. agassizi as well as some small galatheids crabs (M. propinqua and U. parvulus). Previous studies on deep-sea corals associated to trawling fishery of the crustaceans Cervimunida johni and Pleuroncodes monodon off central Chile (Andrade, 1986) (250 to 500 m depth), cited the presence of four species of gorgonians (Callogorgia sp., Muriceides sp., Swiftia sp. and an unidentified species of Paramuriceidae) and the Alcyonacea, Anthomastus sp. The present study increase the number of deep-sea coral species described from the Chilean coast. Additionally, Galvez-Larach (2009; fide Molodtsova, 2005), cited the presence of 8 families and 19 genera of Antipatharia and Scleractinia in Nazca Plate and Salas y Gomez seamount. However, no common species with O'Higgins I seamount fauna was observed.

[FIGURE 3 OMITTED]

Biomass level of benthic megafauna from O'Higgins I seamount is higher if compared with other subtidal, benthic system from the Humboldt Current System, such as the central Chilean continental shelf macrobenthos and megabenthos under upwelling effects (Gallardo et al., 1994, 1996, 2004), or the macrobenthic communities associated to the continental slope off Antofagasta (Canete et al., 1999) and for the different oxygen-minimum zone (OMZ) distributed around of the world (Levin, 2002). Near to 1 kg deep-sea corals, excluding the rest of the fauna, taken from three small samples 1 m2 collected through of the trawl net were recorded in the present study (Fig. 2).

This preliminary study offers the opportunity to stimulate new benthic research in open oceans off Chile. Communities dominated by suspension-feeding cnidarians, forming cold-water coral reefs, have been detected in austral channels and fjords (Forsterra & Haussermann, 2003; Haussermann & Forsterra, 2007a, 2007b), at the Chilean continental slope (Andrade, 1986), the Weddell Sea, Antarctic (Gili et al., 2000) and in numerous seamounts around the world (Galvez-Larach, 2009). The knowledge about their ecological services has just recently started to be considered (Turner et al, 1999; SUBPESCA, 2006) (e.g. production of bio-products of pharmaceutical interest and as nursery and fishery ground of species of economical importance).

The presence of this undisturbed association of colonial cnidarians (Hughes, 1987; McFadden, 1991) and others solitary marine invertebrates on O'Higgins I seamount, allow to predict that off the Chilean coast there is probably an unknown high diversity of benthic communities for discovery. This important finding of seamount communities below the Humboldt Current System is located in an area where high endemism and biodiversity has been detected within the Pacific Ocean (De Forges et al., 2000). A network of marine protected areas should be developed here to inhibit the degradation or even loss of this habitat which could need centuries to recover. Oceanic seamounts could be candidates to maintain the biodiversity, allowing the larval connectivity and acting as buffer of coastal, disturbed bottoms with overexploited resources (Turner et al., 1999).

DOI: 10.3856/vol40-issue2-fulltext-23

ACKNOWLEDGEMENTS

We thank the taxonomic specialists for identification: Dennis Opresko (National Museum of Natural History, Smithsonian Institution) and Juan Sanchez (Universidad de los Andes, Colombia). Thanks to Prof. Patricio Arana (Pontificia Universidad Catolica de Valparaiso, Chile), for a copy of the paper of Andrade (1986). Special thanks to Prof. Alejandro Zuleta (CEPES, Universidad Austral de Chile) for the facilities to participate in the international cruise onboard of "Koyo Maru" and the Dean of Faculty of Sciences and the University of Magallanes, providing funds to participate in this cruise.

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Received: 2 August 2011; Accepted: 7 June 2012

Juan I. Canete (1) & Verena Haussermann (2,3)

(1) Facultad de Ciencias, Universidad de Magallanes, P.O. Box 113-D, Punta Arenas, Chile

(2) Escuela de Ciencias del Mar, Pontificia Universidad Catolica de Valparaiso Avda. Altamirano 1480, Valparaiso, Chile

(3) Fundacion San Ignacio de Huinay, P.O. Box 462, Puerto Montt, Chile

Corresponding author: Juan I. Canete (ivan.canete@umag.cl)
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Title Annotation:articulo en ingles; corriente de Humboldt, monte submarino O'Higgins, megafauna bentonica
Author:Canete, Juan I.; Haussermann, Verena
Publication:Latin American Journal of Aquatic Research
Date:Jul 1, 2012
Words:2642
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