Tatiana Hromic

DISTRIBUCIÓN BATIMÉTRICA DE FORAMINÍFEROS BENTÓNICOS (PROTOZOA: FORAMINIFERIDA) AL SUR DEL ESTRECHO DE MAGALLANES (52°-56°S), CHILE

RESUMENSe analiza la distribucion batimetrica de los foraminiferos bentonicos en el area de canales y fiordos, al sur del estrecho de Magallanes, (52-56°S), Chile. Para ello se estudiaron 34 muestras recolectadas en la zona de plataforma (35 - 650 m), durante la expedicion CIMAR 3 FIORDOS (1998), organizada por el Comite Oceanografico Nacional (CONA). Se obtuvieron 21.190 ejemplares los que fueron clasificados en 169 especies; solo el 8,3% de las especies alcanzaron una representacion superior al 2%, por lo cual, se seleccionaron 47 especies, segun su abundancia por tramo, para verificar su distribucion.Se reconocieron tres asociaciones: a) de aguas someras (0-150 m); en la porcion mas superficial (50 m) dominaron Buccella frigida, Buliminella elegantissima y Discorbis berthelothi. Entre 50 y 100 m abundaron Cibicides dispars, Buccella frigida y Ammonia beccarii y en la parte mas baja Angulogerina angulosa y Ehrenbergina pupa. b) de aguas intermedias (150 - 350 m); en el estrato mas alto de este horizonte (150 - 200 m) dominaron Uvigerina brunnensis, Bulimina notovata y Nonionoides grateloupi. Entre 200 y 250 m se mantuvo la presencia de Nonionoides grateloupi y Bulimina notovata y se hizo presente Oridorsalis tener. Entre 250 y 300 m, se presentaron Angulogerina angulosa, Cassidulina carinata y Globocassidulina rossensis y finalmente, c) de aguas profundas (>350 m) en donde abundaron Oridorsalis tener y Cibicides refulgens, algo mas profundamente aun se encontraron Discanomalina vermiculata, Cibicides refulgens y Angulogerina angulosa y finalmente, por debajo de los 600 m se encontraron Angulogerina angulosa, Angulogerina carinata y Cassidulina laevigata.Palabras clave: foraminiferos bentonicos, profundidad, canales patagonicos, Chile.

ESTRUCTURA COMUNITARIA DEL TAXA FORAMINIFERIDA (PROTOZOA), SEGÚN PROFUNDIDAD, EN EL FIORDO COMAU, CHILOÉ, CHILE

RESUMENLa composicion de las comunidades foraminiferologicas en sedimentos superficiales de aguas menores a 30 m y mayores a 80 m del fiordo Comau, golfo de Ancud, Chiloe, Chile, aplicando SIMPER, ANOSIM, MDS y analisis de Cluster, muestran una alta diferencia y distinguen dos comunidades: una de aguas someras, en la cual las especies que mas contribuyen a la similitud de las muestras son Ammonia beccarii (87,6 %) y Buccella peruviana (4,48 %) y otra de aguas mas profundas, en la cual, las especies que mas contribuyen a su individualizacion son: Uvigerina bifurcata (24,8%), Bulimna notovata (21,8%), Bulimina patagonica (14,42%), Nonionella auris (10,11%), Globocassidulina minuta (7,37%), Nonio-noides grateloupi (3,94%), Quinqueloculina seminula (3,44%), Buccella frigida (3,13%) y Bulimina marginata (2,93%). Todas ellas eran conocidas en el area de canales y fiordos patagonicos chilenos. Ambas comunidades evidencian tambien diferencias en relacion con el numero de especies, abundancia, diversidad y homogeneidad, parametros que aumentan casi al doble en las aguas mas profundas. La cantidad de foraminiferos con caparazon arenaceo tiende a aumentar hacia las profundidades mientras que los porcelanoides tienden a disminuir.Palabras clave: foraminiferos bentonicos, distribucion batimetricaABSTRACTAssemblages of foraminifera were studied at two depths (surface sediment obtained from shallow water 80m ) in Comau Fjord, Chiloe, Chile. From analyses of results by SIMPER, ANOSIM, MDS, and Cluster Analyses, two distinct communities were described. In the shallow water sediments Ammonia beccarii (87.6 %) and Buccella peruviana (4.48 %) are the species which contributed most to the similarity of the samples. From the deep water sediment, the main species contributing to the internal similarity were: Uvigerina bifurcata (24.8 %), Bulimna notovata (21.8%), Bulimina patago-

Distribución latitudinal de foraminíferos bentónicos (Protozoa: Foraminiferida) a nivel de subórdenes y familias, en canales y fiordos patagónicos chilenos

The latitudinal distribution of benthic foraminifers is studied at the levels of suborder and family. 106 samples were collected on the continental shelf (50-300 m) between 43oS and 55oS in the area of channels and fjords, eastern South Pacific, during Cimar Fiordos Expeditions 2, 3, 7 and 8. The foraminifers (50,480 specimens) were classi - fied in 5 suborders, 46 families and 228 species. The number of suborders, families, and the families by suborder do not depend on the latitudinal gradient. Likewise, abundance at the suborder and family levels does not fluctuate with latitude. A major change was observed at 44oS (Baeza and Memory channels), where the number and abundance of suborders and families, species richness, and diversity decreased drastically. The same occurred between 46o and 48o S (Steffen and Mitchell estuaries and Escape channel). This may suggest that local events, such as oceanic currents, could be more important than latitude in controlling microfauna distribution patterns.

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.