Diatom abundance in surface sediments of the northern North Pacific

In order to map the modern distribution of diatoms and to establish a reliable reference data set for paleoenvironmental reconstruction in the northern North Pacific, a new data set including the relative abundance of diatom species preserved in a total of 422 surface sediments was generated, which covers a broad range of environmental variables characteristic of the subarctic North Pacific, the Sea of Okhotsk and the Bering Sea between 30° and 70°N. The biogeographic distribution patterns as well as the preferences in sea surface temperature of 38 diatom species and species groups are documented. A Q-mode factor analysis yields a three-factor model representing assemblages associated with the Arctic, Subarctic and Subtropical water mass, indicating a close relationship between the diatom composition and the sea surface temperatures. The relative abundance pattern of 38 diatom species and species groups was statistically compared with nine environmental variables, i.e. the summer sea surface temperature and salinity, annual surface nutrient concentration (nitrate, phosphate, silicate), summer and winter mixed layer depth and summer and winter sea ice concentrations. Canonical Correspondence Analysis (CCA) indicates 32 species and species groups have strong correspondence with the pattern of summer sea surface temperature. In addition, the total diatom flux data compiled from ten sediment traps reveal that the seasonal signals preserved in the surface sediments are mostly from spring through autumn. This close relationship between diatom composition and the summer sea surface temperature will be useful in deriving a transfer function in the subarctic North Pacific for the quantitative paleoceanographic and paleoenvironmental studies. The relative abundance of the sea-ice indicator diatoms Fragilariopsis cylindrus and F. oceanica of >20% in the diatom composition is used to represent the winter sea ice edge in the Bering Sea. The northern boundary of the distribution of F. doliolus in the open ocean is suggested to be an indicator of the Subarctic Front, while the abundance of Chaetoceros resting spores may indicate iron input from nearby continents and shelves and induced productivity events in the study area.

Biogenic opal and diatoms in surface sediments of the South Western Atlantic

Based on 66 surface sediment samples collected in the SW Atlantic Ocean between 27 and 50°S, this study presents an overview of the spatial distribution of biogenic opal and diatom concentrations, and diatom assemblages. Biogenic opal has highest values in the deepest, pelagic stations and decreases toward the slope. Diatoms closely follow the spatial trend of opal. Diatom assemblages reflect the present-day dominant hydrographical features. Antarctic diatoms are the main contributors to the preserved diatom community in core top sediments, with coastal planktonic and tropical/subtropical diatoms as secondary components. Dominance of Antarctic diatoms between 35 and 50°S in the pelagic realm mirrors the northward displacement of Antarctic-source water masses, characterized by high nutrient content and low salinity. Northward of ca. 35°S, the highest contribution of tropical/subtropical, pelagic diatoms, typical for nutrient-poor and high salinity waters, matches the main southward path of the Brazil Current. Mixing of Antarctic and tropical waters down up to 45°S is clearly illustrated by the diatom assemblage. Concentrations of biogenic opal and diatoms rather reflect the path of predominant water masses, but are less correlated with surface water productivity in the SW Atlantic.

Distribution of diatom species as abundance estimates from vertical multinet hauls from 150 m water depth in the Indian Ocean

During the Indian Ocean Expedition of R/V METEOR phytoplankton samples were taken with a multiple closing net (Multinet) at 103 stations. In this material the diatoms were investigated. In all 247 taxa could be identified which belong to 242 species and 5 varieties of formae of 80 genera. Of these 1 variety, 15 pecies, and 3 genera are newly described. New combinations were made for 18 species, and a number of old combinations was reinstated.

Late Holocene diatom abundaces in sediment core HC-11

The study of diatoms in core HC11 collected from the southwestern part of Chukchi Sea, allowed to distinguish 3 diatoms ecological zones, reflecting paleoenvironmental changes during the last 2300 years. The sediment age was based on the sedimentation rates, determined by 210Pb and radiocarbon dating of mollusk shells. The environmental changes of Chukchi Sea revealed by examination of diatoms correlates with global climate changes - the warming of the early and middle Subatlantic and cooling of the late Subatlantic (Little Ice Age). Warming early and middle Subatlantic in the Chukchi Sea was probably stronger than the warming of the late 20th century and was not accompanied by significant changes in sea level.

Diseño de un circuito Agroecoturistico con base en los potenciales naturales y productivos del Centro Experimental ICIDRI Masatepe de la Universidad Politécnica

El presente estudio se llevó a cabo en el Centro Experimental ICIDRI Masatepe para realizar un Diseño de un circuito Agroecoturístico con base en los potenciales naturales y productivos del Centro Experimental ICIDRI Masatepe en un área de 10.2 manzanas. Se contemplaron 3 etapas: (I) La de planeación y organización que facilitó a través de una visita previa, los tiempos y formas de recabar la información requerida; (II) Trabajo de campo en la cual se levantó la información en dos visitas al sitio para la delimitación del área, realizar un inventario florístico y de fauna, y de la propuesta de estaciones interpretativas; y en la Etapa III, se logró el análisis e interpretación de toda la información recabada y en conjunto con el equipo de docentes UNA y de ICIDRI de la UPOLI, reviso la propuesta y fue aceptada. El Centro, cuenta con un potencial natural que incluye diversidad de especies arbóreas y fauna, que dan lugar al disfrute de variados paisajes y de clima; con potenciales productivos que brindan la oportunidad a productores la adopción de nuevas prácticas. A partir de estos escenarios, se propuso un circuito Agroecoturístico cerrado con 11 estaciones interpretativas en un tiempo no mayor de 3 horas. Del inventario florístico resultaron 1,284 especies, siendo las más representativas Aguacate (Persea americana Mill.), Cedro Real (Cedrela odorata L.), Laurel (Cordia alliodora (Ruiz & Pav.) Oken.) y Aceituno (Simarouba amara Aubl.). Entre la fauna silvestre se encontró Ardilla (Sciurus variegatoides), Ameiva undulata, (Holcosus undulatus) traga venado (Boa Constrictor), Guarda Barranco (Eumomota superciliosa) y Salta piñuela (Anthracothorax prevostii). Las condiciones de cercanía, topografía, capacidades locales, distancia de recorrido, escenarios, temáticas abordadas en las estaciones e infraestructura básica, hacen del centro una oportunidad para la implementación del circuito. Sin embargo, se debe divulgar su quehacer, rotular los caminos, ubicación de cestos de basura y brindar capacitación al personal para guiar a los diferentes usuarios que lo visiten.