Américo Montiel

Spatial and temporal variability of the benthic assemblages associated to the holdfasts of the kelp Macrocystis pyrifera in the Straits of Magellan, Chile

Macrocystis pyrifera (L.) C. Agardh is a characteristic macroalga in the Magellan region covering almost 30% of the shallow coastal waters. The focus of this study was to analyse the spatial and seasonal patterns in macrofauna communities associated to the holdfasts of Macrocystis pyrifera at two study sites in the Straits of Magellan, South Chile. In total, 114 species from 10 major taxa were isolated from the holdfasts. MDS clearly separated the holdfast fauna collected in different seasons, with autumn and winter collections being richer in terms of species richness and abundance as compared to the spring and summer situation. MDS also clearly separated the holdfast associated faunas of the two study sites, Bahía Laredo and Fuerte Bulnes. The community structure and species composition of the associated macro-invertebrates and vertebrates appeared rather heterogeneous, probably due to the extremely heterogeneous environmental conditions along the entire coastline of the Subantarctic Magellan region.

Distribution patterns and biodiversity in polychaete communities of the Weddell Sea and Antarctic Peninsula area (Southern Ocean)

During the expedition EASIZ II with RV ‘POLARSTERN’ in 1998 a multibox corer yielded 151 quantitative samples from 26 stations between 120 and 2415 m water depth for benthic community analysis. From this material a total of 235 polychaete species out of 37 families was determined. Forty-seven species are new to science. The polychaete fraction contributed 41.9% to total benthic abundance and 6.5% to total benthic biomass at these stations. Overall mean polychaete abundance (ind m −2 ) and biomass (g wet weight m −2 ) at the stations were 1617 and 49, respectively. Multidimensional scaling procedure clearly grouped the stations into south-eastern Weddell Sea shelf stations, deep-water stations, and stations mostly around the Antarctic Peninsula. Differences between these groups existed in terms of polychaete abundance and biomass as well as species composition, diversity, and evenness.

ESTIMACIÓN DE PRODUCCIÓN SECUNDARIA Y PRODUCTIVIDAD PARA UNA POBLACIÓN INTERMAREAL DE TROPHON GEVERSIANUS (BAHÍA LAREDO, ESTRECHO DE MAGALLANES)

RESUMENEl gastropodo carnivoro Trophon geversianus (Pallas, 1774) es una de las especies bentonicas explotadas comercialmente en la region de Magallanes, de la cual no existe informacion relacionada a su productividad biologica. En este trabajo, se estimo la produccion secundaria y productividad de una poblacion intermareal de T. geversianus a traves del modelo de redes neurales. Los muestreos se realizaron estacionalmente en Bahia Laredo, estrecho de Magallanes entre los meses de agosto 2007 y abril 2008. La longitud de los ejemplares de T. geversianus fluctuo de 12,4 a 55,4 mm (28,4 ± 7,4). La poblacion presento una distribucion unimodal. Las densidades medias estacionales oscilaron entre 0,23 ind m -2 y 0,97 ind m -2 , mientras que la biomasa media vario entre 0,041 g PSLC m -2 y 0,194 g PSLC m -2 . La produccion secundaria anual promedio estimada para T. geversianus vario entre 0,03 y 0,16 g PSLC m -2 ano -1 y la productividad estimada fue de 0,7 ano. En la razon P/B se observo una correlacion significativa con el peso corporal de T. geversianus. La productividad estimada para T. geversianus es consistente con los valores reportados en la literatura para otras especies de moluscos marinos de las areas Antartica, Subantartica y Chilenas.Palabras clave: Gastropoda, Muricidae, razon P/B.

ESTRUCTURA DE LA COMUNIDAD MACROFAUNÍSTICA BENTÓNICA EN LA BOCA ORIENTAL DEL ESTRECHO DE MAGALLANES, CHILE AUSTRAL

Se describe la variabilidad en riqueza de especies y abundancia de los organismos bentonicos asociados a fondos blandos sublitorales de la entrada oriental del estrecho de Magallanes. Se identificaron un total de 49 taxa, pertenecientes a 9 categorias taxonomicas superiores. El taxon mas diverso fue poliquetos con 27 taxa (56% de los grupos macrobentonicos). Los crustaceos comprendieron 11 taxa (20%), moluscos 4 taxa (8%) y equinodermos 3 taxa (6%). Los grupos cnidarios, nemertinos, priapulidos, ascidias y braquiopodos estuvieron representados por una especie cada uno (10% en total). Los resultados obtenidos muestran que la comunidad bentonica se caracteriza por la presencia de una estructura de especies relativamente simple, con poblaciones numericamente empobrecidas y una dominancia especifica relativamente baja. Se observo un alto reemplazo de especies tanto entre muestras dentro de cada sector estudiado como entre los sectores de muestreo. Se sugiere que el disturbio fisico causado por las corrientes del area con una consecuente disrupcion de los sedimentos y una alteracion significativa en los patrones de movimiento, sedimentacion y erosion, seria un factor clave en el control de la composicion temporal y espacial de la comunidad bentonica en el area estudiada.

New records to Chile of the Family Paraonidae (Annelida: Polychaeta)

Abstract. The Paraonidae are a polychaete family of small body size which have not been reported for Chile until recently. Mainly due to improved sample-processing methods, research campaigns carried out in 1994 and 1996 on three areas off southern Chile have yielded numerous records. Several species proved to be new to the Chilean polychaete fauna, including species that have been known previously only from Antarctic areas. These new records and range extensions are reported in this paper.

Influence of a Glacier Melting Cycle on the Seasonal Hydrographic Conditions and Sediment Flux in a Subantarctic Glacial Fjord

Four hydrographic surveys were carried out in Gallegos Sound (54 ∘ 28 ′58 ″S–69 ∘ 50 ′55 ″ W), a subantarctic glacial fjord. This is the first comprehensive seasonal study for the extreme isolated areas in the Cordillera Darwin Ice Field, Chile. The fjord exhibits a strong seasonal pattern in its oceanographic characteristics. The highest values of total suspended solid concentrations were observed in summer (>15 mg L −1), with the lowest concentrations in winter (<5 mg L −1). Seasonality of the oceanographic characteristics in Gallegos Sound is significantly correlated with the air temperature. In spite of the high pluviosity and maritime climate in this region, the Cordillera Darwin mountain range creates drier conditions that contrast with the climate that influences glacial fjords of Alaska. The relatively high salinity observed in the surface layer during winter confirms that the influence of precipitacion on freshwater and TSS concentration is negligible. As Garibaldi Glacier is the most significant freshwater source in the basin of Gallegos Sound, ice melting represents the main forcing that influences the seasonal characteristics of the surface layer. The mean TSS concentrations observed in Gallegos Sound exhibit a higher range in comparison to other Chilean fjords and are more similar to the concentrations observed in the ice-proximal environment of an Antarctic fjords. In general, TSS concentrations in Gallegos Sound are much lower than those of glacial fjords of the Northern Hemisphere.

PRIMEROS REGISTROS DE OCTOCORALLIA (CNIDARIA: ANTHOZOA) PARA LA RESERVA DE BIOSFERA CABO DE HORNOS, REGION MAGALLÁNICA, CHILE

Information about benthic communities of the Magellan region is largely restricted to ecological studies undertaken in the intertidal boulder-cobble fields and subtidal soft bottoms (Guzman & Rios 1981, Rios & Guzman 1982, Benedetti-Cecchi & Cinelli 1997, Rios & Gerdes 1997, Canete et al. 1999, Gerdes & Montiel 1999, Rios & Mutschke 1999, Thatje & Mutschke 1999, Rios et al. 2003, Montiel 2005, Rios et al. 2005). Despite the rocky bottoms in the shallow subtidal of the Magellan region are very common, data regarding of taxonomical composition and spatial - temporal distribution of benthic organisms are almost absent (Forsterra et al. 2005).On the other hand, improvement in the taxonomic knowledge of benthic groups poorly understo-od such as sea anemones (Haussermann 2004, Haussermann & Forsterra 2005, Haussermann 2006), hydrocorals (Haussermann & Forsterra 2007) and ascidians (Sanamyan & Schories 2003) have been done. In this context, the inventory of the soft coral fauna (Octocorallia) from the Magellan region is based on a few records from the shallow waters (van Ofwegen et al. 2006, 2007). Nowadays, few species have been described for Chilean waters; Clavularia magelhaenica Studer, 1878, which belongs to the group of stoloniferous, was originally described from the Strait of Magellan and several species belonging to the genus Alcyonium such as Alcyonium antarcticum Wright & Studer, 1889, Alcyonium haddoni Wright & Studer, 1889, Alcyonium sollasi Wright & Studer, 1889, Alcyonium paessleri May, 1899 (synonymized with A. antarcticum by Verseveldt & van Ofwegen 1992) have been recorded. Recently, van Ofwegen et al. (2007) recognize eight different species of genus Alcyonium, half of them from the Magellan region and four new species found north of the Magellan region. Other soft corals described from Chilean waters include the species Renilla chilensis Philippi, 1892, and the recently described clavulariid Incrustatus comauensis van Ofwegen et al. 2006 (Riveros 1948, Verseveldt 1967, Verseveldt & van Ofwegen 1992, Casas et al. 1997, Perez & Zamponi 1999, van Ofwegen et al. 2006).

Polychaete diversity in the Scotia Arc benthic realm: Are polychaetes tracers for faunal exchange?

The Scotia Arc is the only shallow-water and island bridge linking nowadays Patagonia and the Antarctic. The Antarctic Circumpolar Current as an oceanographic peculiarity makes this region an interesting biogeographic transition zone, because this frontal system traditionally is said to isolate the Antarctic fauna from that of the adjacent northern ecosystems. Based on benthos samples from three expeditions onboard R/V Polarstern, we studied distribution patterns of 200 polychaete species and 34 major benthic taxa in order to evaluate the role of polychaetes in the benthic realm of this part of the Southern Ocean. ANOSIM test distinguished three station groups: the central eastern Scotia Sea, the continental shelf off South America and stations at the tip of the Antarctic Peninsula. These station groups differed in organism densities and diversities with stations at the tip of the Antarctic Peninsula hosting the most diverse and dense community. The polychaete diversity patterns in the three assemblages evidenced closer connectivity between the tip of the Antarctic Peninsula and the central eastern Scotia Sea than between the continental shelf off South America with either the stations off the tip of the Peninsula or the central eastern Scotia Sea. This is probably supported by the Polar Front, which divides the island chain into two branches. Species distribution and community patterns of polychaetes appear to be associated with oceanographic and sediment conditions in this region. Most of the shared species showed the capability to tolerate differences in hydrostatic pressure. We suggest that the islands of the Scotia Sea may constitute a bridge for exchange of benthic species, particularly for polychaetes with eurybathic distribution and high dispersal capabilities.

Composición y Estructura de la Comunidad Macrobentónica en el Sitema Interior de Canales y Fiordos del Extremo Austral de Chile

La composicion de la comunidad, en conjunto con la distribucion y abundancia de los macroinvertebrados bentonicos, fue estudiada en el sector de canales y fiordos interiores de la zona austral de Chile. El trabajo de terreno fue realizado durante el Crucero CIMAR 15 FIORDOS, a bordo del buque oceanografico de la Armada de Chile “AGOR Vidal Gormaz”. Se utilizo una red de arrastre Agassiz modificada (AGT) para tomar datos semi-cuantitativos en 19 estaciones de muestreo, con profundidades que variaron entre 26-620 m. Un total de 61 taxones fueron identificados en 13 estaciones con lances exitosos. Los moluscos (16 taxones) y los equinodermos (15 taxones) fueron los grupos dominantes en terminos de riqueza especifica, en tanto que numericamente los equinodermos fueron el grupo mayoritario (54%). El asteroideo Ctenodiscus procurator resulto ser la especie dominante (43%) en el conjunto de estaciones. Los resultados mostraron diferencias espaciales en la estructura y composicion de macroinvertebrados, sugiriendo la existencia de dos ensambles asociados a la profundidad como factor principal. Se sugiere que la relativamente alta biodiversidad en estas areas se mantiene por un alto remplazo de especies entre sitios, con sectores bien definidos y ademas diferenciados respecto de su composicion biotica. Para futuros estudios, es altamente deseable una mayor densidad de estaciones de muestreo y la inclusion de metodos cuantitativos de toma de muestras complementarios a los semi-cuantitativos con una AGT.

Foramíferos Bentónicos de Seno Gallegos y Bahía Brookes (54,5° S - 69,5° S), Chile: patrones de distribución y diversidad

ABSTRACTThis paper describes the distribution pattern and diversity of benthic foraminifera from Gallegos sound and Brookes Bay (XII Region, Chile) and the relationships with the particle size and concentration of the organic matter. Fourteen samples were obtained using a Van Veen grab between 22 and 65 m water depth in January 2010.The sediment at all stations was predominantly sand. Thirty-five species of foraminifera were de-termined from 1601 collected specimens. Mean abundance was 14.8 ind g -1 per station. Diversity, mea-sured using Shannon-Wiener index (H’) varied between 1.7 and 2.8. The highest diversity was recorded in stations at Brookes Bay and the lowest in the stations from Gallegos sound off Ventisquero Garibaldi. Cluster analysis identified two stations groups. Only sediment texture and particle size were significantly related to mean abundance, diversity and eveness. There was no relationship between depth, concentration of organic matter and the community’s parameters. Our results suggest that interstitial space in the sandy habitat play an important role in the establishment of foraminifera communities within Gallegos sound and Brookes Bay.Key words: benthos, microfauna, meiofauna, fjords, marine periglacial.