Evaluation of acoustical particle counter for the sizing of fog droplets

An acoustical particle counter (or acoustical particle sizing device) was evaluated for counting and sizing of fog droplets. Fog droplets were generated under controlled conditions in the laboratory. Fog droplet sizes were measured by an optical and an electron microscope and compared to results from the acoustical particle counter. Most of the droplets were found to be in the size range of 5–30 µm. The mean diameters estimated from the acoustical particle counter were in agreement with the microscope values of mean droplet diameter. A Rich 100 condensation nuclei monitor was also operated simultaneously during the fog droplet counting to monitor the condensation nuclei counts in the laboratory. The results indicate that condensation nuclei count is inversely correlated with the fog droplet threshold diameter. Aerosols of uniform size (35 µm) were generated by the vibrating orifice monodisperse aerosol generator and counted at three different flow rates by the acoustical particle counter. The counts/liter/minute were similar, indicating the reliability of the acoustical particle counter.     

General effects of climate change on Arctic fishes and fish populations

Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes. This results in a wide range of future possibilities for arctic freshwater and diadromous fishes. Owing to a dearth of basic knowledge regarding fish biology and habitat interactions in the north, complicated by scaling issues and uncertainty in future climate projections, only qualitative scenarios can be developed in most cases. This limits preparedness to meet challenges of climate change in the Arctic with respect to fish and fisheries.