First record of the pacific fanfishpteraclis aesticola (jordan and snyder, 1901) in the tropical eastern pacific

One specimen ofPteraclis aesticola was collected off San José del Cabo, Baja California Sur, México (22°54′N, 109°45′W), in March 2007. Present record is the first reported occurrence of the species in the Tropical Eastern Pacific biogeographic region (Gulf of California to southern Ecuadorian waters). Its large fan-like anal and dorsal fins and its counts of fin rays and vertebrae can distinguish the Pacific fanfish from the other species in the genus. This fish may have not yet been recorded in the region because its presence has been overlooked in the past because of rarity and lack of commercial value.     

Pockforms: an evaluation of pockmark-like seabed features on the Landes Plateau, Bay of Biscay

Pockmark-like seabed features located on the Landes Plateau, Bay of Biscay, are depressions up to 1 km across and 50 m deep according to multibeam echo sounder data. Seismic (airgun and TOPAS) profiles show that each feature comprises a stack of identical features which extend down to 300 ms (twt). Three types of depressions, elongate, irregular and circular, appear as non-truncating V-shaped features in the Plio-Quaternary sediments. These features are located above the Parentis Basin where deep faults, basement ridges and diapiric bodies extend upwards across the sedimentary cover, providing ideal migration pathways for any buoyant fluids. Initial inspection suggests that these are classic pockmarks; however, the absence of reflection truncation and the absence of indications of shallow gas beneath the features indicate that they were not formed by the removal of sediment. These are “pockforms” but not “pockmarks”. This paper presents an explanation for the formation of these features, involving collapse and subsidence, sedimentary erosion, and only in some cases the erosion of seabed sediments by probable escaping fluids. These origins are mainly conducted through tectonic fluid dynamics which acted in the area up to the Late Miocene. It might be expected that these features would have been infilled by subsequent sedimentation, but their shape has been preserved because sedimentation in the area mainly comprised muds deposited from low-energy transportation (diluted gravity flows) and settling from hemipelagic suspension.     

Spatial patterns of primary production on the shelf, slope and basin of the Western Arctic in 2002

In the spring and summer of 2002 primary production in the Chukchi Sea was measured, using ¹⁴C uptake experiments. Our cruise track encompassed the shelf and continental slope area of the Chukchi and Beaufort Seas progressing into deep water over the Canada Basin. The study area experienced upwards of 90% ice cover during the spring, with ice retreating into the basin during the summer. Production in the spring was light-limited due to ice cover, with average euphotic zone production rates of <0.3 g C m⁻² d⁻¹. Values of 8 g C m⁻² d⁻¹ were observed in association with surface bloom conditions during the initial ice breakup. Considerable nutrient reduction in the surface waters took place between the spring and summer cruise, and although not observed, this was attributed to a spring bloom. Decreased ice cover and increased clarity of surface waters in the summer allowed greater light penetration. The highest rates of production during the second cruise were found at 25–30 m, coincident with the top of the nutricline. Daily euphotic zone productivity in the summer averaged 0.78 g C m⁻² d⁻¹ on the shelf and 0.32 g C m⁻² d⁻¹ on the edge of the Canada basin. These data provide an estimated annual production of 90 g C m⁻² yr⁻¹ in the study area.     

Quaternary evolution of the Ría de Vigo, Spain

The seismic analysis of the sedimentary infill of the Ría de Vigo reveals that the infill comprises of a fifth order sequence (18 ky) bounded by a major discontinuity surface. Within the Holocene sequence, several seismic units have been identified; the oldest one originated after the Würm glaciation and the origin of its top discontinuity was eroded during the regression (sea level at − 120 m) of this last glacial episode (isotopic stages 2 to 4), 18 ky B.P.

In some places below this ría infill, another sequence can be identified. This older sequence is associated with the pre-existing faults and troughs in the deepest parts of the ría, and it was deposited during the Würm glaciation (Miocene–Pleistocene). Eroded sediments were moved from the rías area to deeper zones, where they accumulated in the lowstand system tract. The next sea level rise occured in two steps, producing two transgressive units separated by an hiatus surface. This cycle was interrupted by the next sea level fall (to − 55 m) marked on the seismic records by another recognizable boundary. The next sea level rise took place in several steps (back-stepping) with some stillstands, generating another transgressive system tract in the ría. From that time on, the relative sea level continued rising, depositing the most recent unit which represents the highstand system tract. Separating the highstand system tract and the transgresive unit below there is a consensed section.

The analysis of 29 cores provides groundtruthing for our hypothesis. The identified main lithologic units show a transgressive sequence: a granitic rock base, an overlying second unit-locally wedge shaped- and most recently, a marine muddy unit covering the present ría seafloor.     

High-resolution mapping of shallow gas accumulations and gas seeps in San Simón Bay (Ría de Vigo, NW Spain). Some quantitative data

San Simón Bay in the innermost part of the Ría de Vigo is characterized by an abundance of very shallow gas accumulations and methane seeps. During the expeditions of April–June–September 2004 within the Spanish-funded Gs2G project, detailed very high-resolution seismic and field investigations were carried out to study the shallow gas and the seeps. Direct gas fluxes also were measured from bubble streams. For the first time, the surface area and gas front depth of a shallow gas field has been mapped and quantified in the inner bay of Ría de Vigo. This field overlaps spatially with the distribution of Holocene mud within the bay. Seismic data show 3.6 km² affected by acoustic turbidity but this surface can be extended up to 9.5 km² of San Simón’s muddy subtidal area. Mounded turbidity superimposed on the main gas field has been mapped and characterized as anthropogenically (mussel rafts) mediated gas accumulations. Different acoustic anomalies have been identified and interpreted as being due to gas escapes from the present seabed sediment. The very high resolution of the seismic data makes it possible to identify a new type of seep, here named ‘acoustic smoke.’ A direct relationship can be observed between the gas front of accumulations and escape features, both acoustic seeps and pockmarks. The methane flux has been estimated from the subtidal environment in San Simón based on detected acoustic targets and direct measurements of current bubble flow. The total estimated methane flux from the seabed into the water column ranges from 10.1 to 48.8 t/year, and into the atmosphere from 7.0 to 34.2 t/year. The intertidal San Simón environment is also actively venting methane, as indicated by the presence of bubbling during high tide and white patches of Beggiatoa sp.     

Silicon Deficiency Induces Alkaline Phosphatase Enzyme Activity in Cultures of Four Marine Diatoms

Alkaline phosphatase (AP) was detected using ELF-97® in silicon-starved Pseudo-nitzschia multiseries cells; thus, we tested two, alternative hypotheses: Pseudo-nitzschia multiseries has a high phosphate demand, showing signs of phosphate deficiency even when concentrations of orthophosphate are high, or silicate deficiency can stimulate the AP enzyme in this species. We also studied the effect of silicon deficiency on AP in three other common marine diatoms: Thalassiosira pseudonana, Nitzschia pusilla, and Nitschia closterium. Each of the species tested showed a different pattern of AP regulation. AP levels, however, increased in the four diatoms as a result of silicon deficiency, suggesting that AP may be involved in a variety of intracellular processes related to silicon deficiency. Additionally, the results of this study indicate that AP could be stimulated by stressors other than phosphate deficiency, such as silicon deficiency; therefore, it should be used cautiously as an indicator of phosphate limitation.