The pattern of deposition of air-borne salt of marine origin under a forest canopy

Summary The distribution of air-borne salt within a forest was investigated. Na deposition decreased rapidly for three canopy heights' from the windward edge of the forest. Deposition was constant throughout the remainder of the forest. Levels of deposition experienced near the edge of the forest may be expected to influence tree growth and development and possibly soil formation. Air-borne Mg and Ca show a similar, but much reduced, trend to Na but still have a major r?le in nutrient cycling systems.     

Ion fluxes and diffusion potentials in the Dungeness crab,Cancer magister

Summary Transepithelial potentials (TEP's) were measured in Dungeness crabs exposed to a variety of experimental media. The TEP's can be accounted for as diffusion potentials. In sea water (SW) theP _Na/P _Cl ratio (calculated by substitution in the Goldman equation) was 0.68, but in dilutions of SW the value increased, reaching a maximum of 3.33 in freshwater (FW). When the calcium and magnesium concentrations in the diluted media were maintained at SW levels theP _Na/P _Cl remained close to that in SW.The effluxes of Na and Cl were monitored in crabs exposed to the experimental media and the TEP's were measured simultaneously. After transfer from SW to FW the decrease in Na efflux was considerably less than expected from the change in potential alone, indicating an increased permeability to sodium, while transfer from SW to 500 mM NaCl caused a 3.4-fold increase in Na efflux without any associated change of potential. These results indicate an increase in the permeability of the gill epithelium to Na as the ambient concentrations of Ca and Mg decline. The Cl effluxes are not dependent on the external concentration of divalent ions, but about 30% of the Cl efflux may be due to exchange diffusion.Abbreviations FW freshwater - SW sea water - TEP transepithelial potential This project was in part supported by faculty research grants from Fordham University, Bronx, NY and Towson State University, Towson, MD to GDR     

Parrot conservation and ecotourism in the Windward Islands

The genus Amazona is represented on three islands in the Windward Islands. Since Europeans first visited the region in the fifteenth century, at least three parrot species have become extinct in the Windward Islands, and today all the extant parrots of the region are endangered. Several factors have contributed to the current plight of the parrots. The authorities in each of the islands of the Windward Islands that have endemic parrots have come to the realization that sound environmental management measures can complement rather than hinder national socioeconomic goals and objectives. Consequently, regional governments have begun to explore and foster linkages between conservation and other sectors of the economy. This article examines current parrot conservation efforts in the Windward Islands and the linkages which are being fostered between tourism and other sectors of the economy. Policy and research implications of the region's current parrot conservation efforts and ecotourism programme are also considered.