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A sonic well log of the basement complex of the Walvis Ridge

A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ～-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval.     

Unusual large-scale phytoplankton blooms in the equatorial Pacific

Unusual large-scale accumulations of phytoplankton occurred across 10,000 km of the equatorial Pacific during the 1998 transition from El Niño to La Niña. The forcing and dynamics of these phytoplankton blooms were studied using satellite-based observations of sea surface height, temperature and chlorophyll, and mooring-based observations of winds, hydrography and ocean currents. During the bloom period, the thermocline (nutricline) was anomalously shallow across the equatorial Pacific. The relative importance of processes that enhanced nutrient flux into the euphotic zone differed between the western and eastern regions of the blooms. In the western bloom region, the important vertical processes were turbulent vertical mixing and wind-driven upwelling. In contrast, the important processes in the eastern bloom region were wave-forced shoaling of nutrient source waters directly into the euphotic zone, along-isopycnal upwelling, and wind-driven upwelling. Advection by the Equatorial Undercurrent spread the largest bloom 4500 km east of where it began, and advection by meridional currents of tropical instability waves transported the bloom hundreds of kilometers north and south of the equator. Many processes influenced the intricate development of these massive biological events. Diverse observations and novel analysis methods of this work advance the conceptual framework for understanding the complex dynamics and ecology of the equatorial Pacific.     

Fracture activity: A possible triggering mechanism for slope instabilities in the Eastern Atlantic?

The largest known submarine slope instabilities occur on gently inclined slopes or in the deep sea. The sedimentation rates are mostly too low to induce an excess pore-water pressure sufficient to create failure. A possible triggering mechanism for these instabilities is additional horizontal ground acceleration caused by earthquakes. Old zones of weakness, represented by fracture zones, can be reactivated by isostatic movements and induce seismic activity. The distribution of some major slope instabilities and the trend of fracture zones in the Eastern Atlantic are compared and Fracture activity is suggested as the main triggering mechanism for these slope instabilities.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.     

An optimized method for automated analysis of algal pigments by HPLC

A recent development in algal pigment analysis by high-performance liquid chromatography (HPLC) is the application of automation. An optimization of a complete sampling and analysis protocol applied specifically in automation has not yet been performed. In this paper we show that automation can only be successful if the various methodological aspects of the sampling and analysis protocol are considered in coherence. We introduce an optimized protocol that involves freeze-drying of the sample, subsequent extraction in 90% acetone and the application of water-packing during analysis. The method was evaluated on both natural plankton populations and a broad spectrum of microalgal cultures: Thalassiosira weisflogii (Bacillariophyceae), Emiliania huxleyi (Prymnesiophyceae), Phaeocystis globosa and Phaeocystis antarctica (Prymnesiophyceae) and Pyramimonas sp. (Prasinophyceae). Whereas pigment extracts were unstable in methanol, with recorded chlorophyll a losses from 10% to 60% per day, pigment degradation rates in acetone were generally less than 1% over 18 h storage in the autosampler (4 °C). In addition, it was found that the extraction efficiency of acetone significantly increased upon freeze-drying prior to extraction. Increases as high as 50–60% were measured in P. antarctica. The application of water-packing of the sample during injection resulted in improved peak shape and peak separation, without diluting the pigment concentrations. Automation is especially beneficial for application in the field, when mixed algal assemblages and low biomass put a high demand on the sensitivity as well as reproducibility of the method.