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.

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.

Boron isotope composition and seawater characteristics of cold water scleratinian corals

The boron isotope systematics has been determined for azooxanthellate scleractinian corals from a wide range of both deep-sea and shallow-water environments. The aragonitic coral species, Caryophyllia smithii, Desmophyllum dianthus, Enallopsammia rostrata, Lophelia pertusa, and Madrepora oculata, are all found to have relatively high d11B compositions ranging from 23.2 per mil to 28.7 per mil. These values lie substantially above the pH-dependent inorganic seawater borate equilibrium curve, indicative of strong up-regulation of pH of the internal calcifying fluid (pH(cf)), being elevated by ~0.6-0.8 units (Delta pH) relative to ambient seawater. In contrast, the deep-sea calcitic coral Corallium sp. has a significantly lower d11B composition of 15.5 per mil, with a corresponding lower Delta pH value of ~0.3 units, reflecting the importance of mineralogical control on biological pH up-regulation. The solitary coral D. dianthus was sampled over a wide range of seawater pH(T) and shows an approximate linear correlation with Delta pH(Desmo) = 6.43 - 0.71 pH(T) (r**2 = 0.79). An improved correlation is however found with the closely related parameter of seawater aragonite saturation state, where Delta pH(Desmo) = 1.09 - 0.14 Omega(arag) (r**2 = 0.95), indicating the important control that carbonate saturation state has on calcification. The ability to up-regulate internal pH(cf), and consequently Omega(cf), of the calcifying fluid is therefore a process present in both azooxanthellate and zooxanthellate aragonitic corals, and is attributed to the action of Ca2+ -ATPase in modulating the proton gradient between seawater and the site of calcification. These findings also show that the boron isotopic compositions (d11Bcarb) of aragonitic corals are highly systematic and consistent with direct uptake of the borate species within the biologically controlled extracellular calcifying medium.

Dieta del “curil” Anadara tuberculosa (Sowerby, 1833) a partir del análisis de contenido estomacal e intestinal, en Bahía de Jiquilisco, Departamento de Usulután, El Salvador

En la costa de El Salvador, el “curil” (Anadara tuberculosa), constituyen una fuente importante de alimento, empleo y beneficios económicos para las personas que habitan en las cercanías de zonas costeras y estuarinas del país. Aunque ésta especie es reproducida artificialmente en el laboratorio de la Estación Acuícola de Producción de Moluscos de Puerto el Triunfo, Usulután, no existe información específica acerca de sus hábitos alimenticios en su hábitat natural para la región centroamericana. Por lo cual, el presente trabajo tuvo como objetivo determinar la composición específica de su dieta, a través del contenido estomacal e intestinal durante los meses de septiembre 2013 a enero 2014 en cuatro sitios de la Bahía de Jiquilisco, El Chile (EC), EL Jobal (EJ), Boca Los Lagartos (BL) e Isla Magueyal (IM). Se analizaron un total de 540 tractos digestivos de Anadara tuberculosa, obteniendo un total de 30,328 ítems alimenticios, en su mayoría correspondientes a 37 especies de diatomeas (95,91%), principalmente por los géneros Thalassiosira plicata (12,78%), Diploneis smithii (9,21%), Diploneis gruendleri (7,59%), Thalassiosira sp. (5,0%), Thalassionema nitzchioides (4,91%). Además, se aplicaron los índices de Levins (Bi=0,42) y Shannon-Wiener (H’=3,24), para amplitud y diversidad de dieta, respectivamente, indicando que esta especie se tipifica como especialista, debido a que presenta un espectro trófico diverso, dominado por pocas especies. Así mismo, se realizó un traslape de dieta de Morisita-Horn, en cuanto a rangos de tallas establecidos (menores de 4 cm, 4-5 cm y mayores de 5 cm), encontrando valores de Cλ=0,50 a 0,90, evidenciando que existe un traslape medio-alto en las especies filtradas por las diferentes tallas; así como también, para los sitios de muestreo se estimaron los índices de similitudes de Jaccard (Ij= 0,63-0,82) y Sorensen (Is= 0,72-0,90) indicando que no existen diferencias significativas en cuanto a los ítems alimenticios encontrados en los tractos digestivos de A. tuberculosa para la Bahía de Jiquilisco.