A SIMULATION OF RIVER-BASIN RESPONSE TO MESOSCALE METEOROLOGICAL FORCING: THE SUSQUEHANNA RIVER BASIN EXPERIMENT (SRBEX)1

ABSTRACT: A mesoscale meteorological model, a surface hydrology model, and a ground-water hydrology model are linked to simulate the hydrographic response of a large river basin to a single storm. Synoptic climatology is employed to choose a representative hydro-climatic event. The mesoscale meteorological model uses three nested domains to simulate relatively high-resolution precipitation over a sub-basin of the Susquehanna River Basin. The hydrology models simulate surface runoff and ground-water baseflow using both analyzed and simulated precipitation. The hydrologic abstractions are handled using both Curve Number and Green-Ampt routines. To support the linkage of the numerical models, special attention is given to data resampling and reprojection. The mesoscale meteorological model simulation captures the spatial and temporal structure of the storm event, while the hydrology models represent the timing of the event well. The Curve Number method generates a realistic hydrograph with both analyzed and simulated precipitation. In contrast, the hydrographic response generated by the Green-Ampt routine is inferior. Several interrelated factors contribute to these results, including: the nature of the precipitation event chosen for the experiment; the tendency of the mesoscale meteorological model to underpredict low intensity, widespread precipitation in this case; and the influence of the surface soil-texture characteristics on infiltration rates.     

The chemical and mineralogical behaviour of Pb in shooting range soils from central Sweden

Recently investigations have shown that the annual flux of lead from shotgun pellets to shooting range soils is significant in some countries. This paper presents the data of chemical and mineralogical analyses of soils and Pb-pellet crusts from five shooting ranges in Sweden and, based on these results, evaluates the retention of lead in these shooting range soils. In the soils, Pb-pellets and bullets are readily decomposed and transformed to crust materials composed of Pb-bearing minerals. The transformation products in the crust materials, identified by X-ray diffraction, are predominantly hydrocerussite [Pb(3)(CO(3))(2) (OH)(2)], associated with cerussite (PbCO(3)) and anglesite (PbSO(4)). In a period of 20-25 years, an average of 4.8% metallic lead in the pellets has been transformed to lead carbonate and lead sulphate, where the former is the more stable mineral in the surface environment. However, in soils relatively rich in humus an average of 15.6% metallic lead in the pellets was transformed to secondary lead compounds in the same period. The results of the chemical analyses indicate that Pb is rather immobile in the soil profile. The surficial horizon contains higher concentrations of lead (52-3400 mg kg(-1)), while lower concentrations of lead were found in the E and B horizons where the total Pb concentrations (8-37 mg kg(-1)) are within about one standard deviation of the mean reference sample concentration. An inverse relationship is revealed between the aluminium hydroxide content of the soil fraction and EDTA-extractable Pb, which suggests that these compounds have affected the retention of lead.     

Nutrients of the Cochin Backwater in relation to environmental characteristics

The nutrient distribution of the Cochin Backwater was studied at 6 stations throughout the year. The depth profiles of phosphorus (inorganic and organic), nitrogen (nitrate and nitrite) and silicon, showed a marked seasonal rhythm, induced by the local precipitation and land runoff. Changes in other environmental features such as temperature, salinity, dissolved oxygen, pH and alkalinity were small during the premonsoon period when the system remains marine-dominated, and large during the monsoon period when the estuary becomes freshwater-dominated. Seasonal changes in the hydrographical conditions of the adjoining coastal waters of the Arabian Sea which influence the backwater system have been discussed.     

Cryopreservation of the dinoflagellate symbiont of the octocoral <Emphasis Type="Italic">Pseudopterogorgia elisabethae</Emphasis>

In this paper we describe a cryopreservation protocol followed by the culture of Symbiodinium sp. isolated from the Caribbean gorgonian Pseudopterogorgia elisabethae as a potential renewable source of the dinoflagellate symbiont. Four different freezing protocols were designed: a controlled cooling device designed to cool at 1°C/min, a three-step protocol (−20°C for 2 h, −70°C for 2 h, liquid nitrogen-LN₂), a two-step protocol (−70°C for 2 h, LN₂), and a one-step protocol (LN₂). All cells were stored in LN₂ after cryopreservation. The cryoprotective agents (CPA) used were ethanol (EtOH) and methanol (MeOH) at 10 and 20%, and seawater (FSW) was used as a control. Viability measurements using cell counts showed that all cryopreservation protocols were relatively successful, and no trends were observed regarding freezing protocol or CPA used. After 19 weeks in culture the viability of samples which had high biomass was determined by the fluorescent assay CellTiter Blue™. The most viable cultures were those cryopreserved by a two-step protocol using 20% MeOH or 20% EtOH as a CPA. A genetic examination of the DNA of these samples using Symbiodinium-specific PCR primers confirmed that the composition of the culture had not changed. For the first time, we report that Symbiodinium sp. isolated from a gorgonian can be cryopreserved and subsequently cultured successfully. Lory Z. Santiago-Vázquez and Nealie C. Newberger contributed equally to this publication.     

Possible control mechanism of cell motility in the gorgonian Eunicella cavolinii

In a previous study it was demonstrated that a lectin controls cell-cell interaction in the gorgonian Eunicella cavolinii (Koch) as a negative modulator. Now we describe the procedure to purify this lectin to homogeneity; its molecular weight is 23 400. The homologous proteoglycans were identified as positive modulators of cell-cell (and/or cell substrate) interaction. The purified single proteoglycan aggregates were 1200±700 nm long and the distance between the attachment points of the proteoglycan subunits was about 45 nm. The glycosaminoglycan residues of the gorgonian proteoglycans were identified as hyaluronic acid (35.5%), heparan sulfate (47.9%) and dermatan sulfate (14.1%). Binding studies with immobilized homologous proteoglycan preparations revealed that gorgonian cells attach to this substratum presumably via its glycosaminoglycans. Quantitative determinations of these two modulators of cell-cell recognition in the three regions of individual colonies revealed concentration gradients these concentration differences reflect a lower cell motility in the polyp-bearing branches and a higher motility of the cells in the polyp-free stem and in the basis, is discussed.