Analysis of photosynthetic picoeukaryote community structure along an extended Ellett Line transect in the northern North Atlantic reveals a dominance of novel prymnesiophyte and prasinophyte phylotypes

Photosynthetic picoeukaryotes (PPEs) of a size <3 ??m can contribute significantly to primary production. Here, PPE community structure was analysed along an extended Ellett Line transect, an area in the North Atlantic well studied by physical oceanographers but largely neglected in the field of microalgal ecology. Distribution patterns of specific PPE classes were determined using dot-blot hybridization analysis, while the taxonomic composition of specific PPE classes was revealed by phylogenetic analysis of plastid 16S rRNA gene sequences. In addition, we performed fluorescent in situ hybridization (FISH) analysis of seawater samples collected along the transect to provide a PCR-independent survey of class level PPE distribution patterns. We found the PPE community was dominated by members of the Prymnesiophyceae, Prasinophyceae and Mamiellophyceae. Interestingly, phylogenetic analysis revealed several novel Prymnesiophyceae and Prasinophyceae phylotypes (with only 85-96% identity to neighbouring sequences) within lineages for which cultured counterparts are unknown.     

Nonlinear effects in the process of propagation of internal waves in the presence of turbulence

In the Boussinesq approximation, we study the nonlinear effects observed in the process of propagation of internal waves in the presence of turbulence. The space damping factor of the waves is evaluated. The Stokes drift velocity and the Euler velocity of the mean current induced by waves due to the presence of nonlinearity are determined. It is shown that the principal contribution to the wave transfer is made by the horizontal velocity of the induced current. The Stokes drift is significant only near the bottom. The vertical component of the Stokes drift velocity obtained with regard for the turbulent viscosity is nonzero.     

Estimations of the parameters of the flux of sediments near the west coast of the Bakal’skaya Spit under the conditions of heavy storms in 2007

On the basis of the wind-energy method, we estimate the distributions of the parameters of a longshore flux of sediments formed near the west coast of the Bakal’skaya Spit (in the northwest part of the Crimea) under the conditions of heavy storms whose action caused a significant erosion of the west coast of the spit and retreat of the coastline in January and November 2007. The calculations are carried out by using the actual directions and velocities of the winds recorded in the investigated region. We analyze the trends of changes in the formation of the coastal zone caused by the nonuniform distribution of the intensity of longshore transportation of sediments. In analyzing the causes of formation of gullies in the barrier of the Bakal’skoe Lake and in the narrow distal part of the body of the spit, we make an attempt of interpretation of the quantities characterizing the force of the frontal action of waves. The obtained numerical results are confirmed by the data of field observations.     

Composition and secondary alterations of microfossils in sediments of the Ashadze-1 hydrothermal field (tropical Mid-Atlantic Ridge)

The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 hydrothermal field in the Mid-Atlantic Ridge sampled during cruise 26 of the R/V Professor Logachev in 2005 revealed the substantial influence of hydrothermal processes on the preservation of planktonic calcareous organisms, as well as on the preservation and composition of the benthic foraminifers. From the lateral and vertical distribution patterns and the secondary alterations of the microfossils, it is inferred that the main phase of the hydrothermal mineralization occurred in the Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts. The distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to the hydrothermal activity. There are three mineral-geochemical zones defined: the sulfide zone, the zone with an elevated Mg content, and zone of Fe-Mn crusts.     

Origin and composition of fluid responsible for metasomatic processes in shear zones of the Bolshie Keivy tectonic nappe,baltic shield: Carbon isotope composition of graphite

Doklady Earth Sciences -     

Subduction-related mafic to felsic magmatism in the Malayer–Boroujerd plutonic complex,western Iran

The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (f_mel) ~ 15%] and exhibit negative Nd and positive to slightly negative ε_Hf(T) (+ 3.0 to ? 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (f_mel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (f_mel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (f_mix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (f_mix: 0.2). However, enriched and moderately variable ε_Nd(T) (? 3.21 to ? 4.33) and high (⁸⁷Sr/⁸⁶Sr)_i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere.     

Species, tissue and gender-related organochlorine bioaccumulation in white-sided dolphins, pilot whales and their common prey in the northwest Atlantic

Organochlorine concentrations were measured in white-sided dolphins, pilot whales, and their prey from the Gulf of Maine and used to identify species, tissue, and gender differences, and trophic transfer trends, in bioaccumulation. Polychlorinated biphenyl concentrations ([PCB]) in dolphin blubber (13 +/- 7.1 micrograms/g fresh wt.) were twice those in pilot whales, but pesticide concentrations (20 +/- 13 micrograms/g fresh) were similar between species. 4,4'-DDE, trans-non-achlor, Cl6(153) and Cl6(138) concentrations were highest. Skin tissues had more recalcitrant organochlorines than the internal organs. Male dolphins bioaccumulated higher concentrations of nonmetabolizable PCBs and hexachlorocyclohexane (HCH) isomers, whereas pilot whales had no gender-related differences in bioaccumulation. Pilot whales, mackerel, and herring had proportionately higher concentrations of DDTs, whereas [PCB] were higher in dolphins and squid. Although these odontocetes feed at the same trophic level and store a similar suite of contaminants, dolphins bioaccumulated higher and potentially hazardous 4,4'-DDE and PCB concentrations from food in their more geographically restricted range.