The island of Gran Canaria is located in the eastern Atlantic, to the west of the Saharan Desert, and, as a result of its proximity, is regularly affected by Saharan dust. When this weather condition occurs (haze conditions) the particulate/aerosol accumulation rate was lightly higher than under nonhaze conditions (5.473.8 mg m À2 h À1 versus 4.372.1 mg m À2 h À1). To quantify the contribution of airborne Saharan dust to soil development in northeastern Gran Canaria, aeolian dust was collected weekly at different altitudes and distances from the coast during a year in a series of collection plots. Mean values of dust accumulation rates decreased with increasing altitude (from 79 to 17 g m À2 yr À1 ). The mineralogy of airborne dust, identified by XRD, was quartz, Mg-calcite, calcite, feldspars, dolomite, magnetite, aragonite, halite, and minor amounts of illite, kaolinite-chlorite and palygorskite. Quartz is considered allochthonous because it is not present in the volcanic substrate of the island. However, the difference in quartz concentration from haze to non-haze conditions was only 10% higher. This suggests an external source, but does not preclude a recycled origin. The recognition of well shaped dolomites, observed by SEM-EDX in collected dust samples and in soils samples of the lowest altitude plot, indicate an edaphic origin, but are later recycled as an airborne component. r
The plankton outburst during the so-called late winter bloom in subtropical waters was studied in relation to lunar illumination in the Canary Island waters. Nutrient enrichment by mixing and dust deposition promoted a bloom of phyto-and zooplankton. Mesozooplankton biomass increased as the winter mixing progressed but peaked in every full moon and decreased thereafter because of the effect of predation by interzonal diel vertical migrants (DVMs). The pattern was similar to the one described in lakes due to predation by fishes and confirms that this phenomenon is important in the sea. The estimated consumption and subsequent transport of epipelagic zooplankton biomass by DVMs after every full moon is on the order of the mean gravitational export and is an unaccounted flux of carbon to the mesopelagic zone that may play a pivotal role in the efficiency of the biological pump.Most of the research about the downward flux of carbon in the ocean has centered on the so-called gravitational flux, the transport due to the sedimentation of the particulate organic carbon production from the euphotic layer to the mesopelagic zone. In tropical and subtropical regions this flux is a low number, normally less than 10% of primary production (Karl et al. 1996). Another component of the biological pump is the so-called active flux due to the transport of carbon by vertical migrants. These organisms feed on the shallower layers of the ocean at night and return to their daytime residence at depth where they metabolize carbon or simply are eaten by other organisms. The role of these rather large organisms (mesozooplankton and micronekton) in the ocean carbon sequestration has been almost neglected. Active flux is a rather complex mechanism that involves the gut flux (Angel 1989) (the transport due to the release of feces below the mixed layer), carbon dioxide respiration (Longhurst et al. 1990), dissolved organic carbon excretion (Steinberg et al. 2000), and mortality (Zhang and Dam 1997) at depth. The few values available at present mainly based on respiration at depth indicate that the active downward carbon flux is highly variable, ranging from 4% to 70% of the gravitational flux (Herná ndez-Leó n and Ikeda 2005a). However, diel vertical migrants (DVMs) account for the control of 5-10% of the daily epipelagic zooplankton production (Hopkins et al. 1996), and this ingested food is efficiently transported downward (Pearre 2003). The consumption of epipelagic zooplankton by these organisms and their role in the fate of a bloom are at present poorly known.A way to study the biological pump in subtropical waters is to understand the development of the bloom during winter, when nutrients are present in the euphotic zone. The late winter bloom in subtropical waters is produced by cooling of the shallower layers of the ocean, eroding the thermocline and allowing a small flux of nutrients to the euphotic zone. This process promotes the increase in primary production and the growth of micro-and mesozooplankton. Atmospheric Saharan...
A study was conducted to assess the properties of a tension porous-ceramic cup soil-solution sampler and its usefulness in extncting soil solutions in selected forest soils (haplic Umbrisols) at "Sierra De Gata'' Mountains, CWSpain. The main characteristics of the sampler evaluated were hydraulic c&ductivity, the time requircd to obtain the soil-water sarnple, and the volume of water uptake for optimum calibration prior to analysis of the chemicaI composition of the soil water solution. Hydraulic conductivity values were not substantially modified dunng the sampling (two hydrologic cycles). The time required to obtain the samples was relatively short (mem value 2 h) and the sphere of sarnpling influence was small (radii ranging from 6 to 15 cm), both depending on the size of the sampler. The chemical analyses obtained after calibrating the ceramic cup sarnpler pointed to: a) an effect of light acisorption by the ceramic cup, involving PO, 3-, DOC, major and minor catbns (Na' , K+, caz", M~~+ , ~e~+ ,A? +, ~n~+ , and 2n2+), Relatively low pH values (the pH of these acid forest soils is 5.1-6.2) favor the adsorption of anions and DOC, the latter also increasing the exchange capacity and cation adsorption of the cup. The results point LO a generaljzcd tendency of the ceramic cup to adsorb DOC, cations and anions (with the exception of chlorides), H4Si04, by contrast, being releascd.
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