Cryoconite holes are water-filled depressions on the surface of glaciers. They contain microbial communities and may contribute to glacial wastage and biological colonization of ice-free areas.

In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong föhn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter föhns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

The movement of water across sedimenthater interfaces is very important to the ecology of aquatic habitats. Submarine groundwater discharge (SGWD) occurs primarily by advectlve flow and may be due to a variety of factors. In nearshore marine environments, the major factor 1s probably groundwater flow from upland regions. In oceanic environments, SGWD is probably influenced more by tides and surge action. SGWD, thercfore, represents various mixtures ot fresh g r o u n d w t e r and seawater This paper summarizes the first regional study of SGM'D and its attendant solutes in shallow estuarine, continental shelf and coral reef habitats, and calls attention to the magnitude of watrr volumes which appear to be circulating through manne sedimcnts. Data on SGWD from sltes in the Florida Keys and on the southeastern continental shelf of the U. and a mean influx of seawater to the sediments (ca 10.8 1 m-' d ' ) . Even though geohydrolocjical n~oclcls would predict coupling of SGWD with landbased hydraulic heads, definitive lower salinity SG\VD could not be detected. The dnving force seems to be subtidal pumping and much of the discharge measured was probably recycled seawater. This research also demonstrated that SGUID serves to move dissolved solutes into the \vater column, and could be a n important link in benthic-pelagic coupllng in continental shelf ecosystcrns.

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Surface water, groundwater, and groundwater discharge quality surveys were conducted in Cherrystone Inlet, on Virginia's Eastern Shore. Shallow groundwater below agricultural lields had nitrate concentrations significantly higher than inlet surface waters and shallow groundwater underlying forested land. This elevated nitrate groundwater discharged to adjacent surface waters. Nearshore discharge rates of water across the sedimentwater interface ranged from 0.02 to 3.69 litersm2•hr-1 during the surveys. The discharge was greatest nearshore at low tide periods, and decreased markedly with increasing distance offshore. Vertical hydraulic heads, Eh, and inorganic nitrogen flux in the sediments followed similar patterns. Nitrate was the predominant nitrogen species discharged nearshore adjacent to agricultural land use, changing to ammonium farther offshore. Sediment nitrogen fluxes were sufficient to cause observable impacts on surface water quality; nitrate concentrations were up to 20 times greater in areas of groundwater discharge than in the main stem inlet water. Based on DIN:DIP ratios, nitrogen contributions from direct groundwater discharge and tidal creek inputs appear to be of significant ecological importance. This groundwater discharge links land use activity and the quality of surface water, and therefore must be considered in selection of best management practices and water quality management strategies.