ALBERT

Description: Interstitial water samples from Leg 86 were analyzed for Cl-, SO42-, Ca2+, Mg2+, K+ , Li+ , Sr2+, Mn2+, Si, NO3-, NH4+ , and d18O. The principal findings are as follows. (1) The chloride profiles consistently show a about 1.5% downcore increase to about 40 m sub-bottom depth. This increase is consistent with model profiles generated by considering the effects of variations in seawater salinity resulting from Pleistocene glaciation on pore-water composition. d18O profiles support this model. This agreement of model and observation precludes advection of the pore fluids at rates greater than 1 mm/yr. (2) Ca2+ and Mg2+ gradients are small relative to other Deep Sea Drilling Project sites, likely resulting from low diffusive fluxes through underlying chert horizons. (3) Other constituents exhibit profiles consistent with previous observations.

Description: The loss of water in a desiccating atmosphere (c.40% r.h. at 10°C) and uptake of water from a saturated atmosphere (100% r.h. at 10°C) was recorded at intervals over periods of many hours or days in the dominant mosses and macroiichens occurring near the Australian Casey Station. Wilkes Land, continental Antarctica. While major differences exist in the water holding capacity and rates of water loss between mosses and lichens, the minimum levels attained after prolonged exposure to desiccating conditions are remarkably similar. By contrast, the volume of water absorbed from a saturated atmosphere is very similar in both groups of cryptogams. Morphological and anatomical characters are responsible for many of the differences, both between species, and within species exhibiting different growth features. Thus, significantly larger amounts of water are held by colonies of Bryum algens with a dense tomentum of rhizoids than those with sparse rhizoids; similarly, the rhizinate Umbilicaria aprina held a greater volume of water than the erhizinate U. decussata. The filamentous mat form of Alectoria mimiscula permits a much higher water content to be attained than in the coarser fruticose forms of Usnea sphacelata and U. antarctica. The dense shoot arrangement in Schistidium antarcticum accounts for the high water holding capacity in the hydric turf form whereas the less densely packed shoots and thicker cell walls of the xeric cushion form maintain a lower water content. The rate of water loss (as percentage dry weight) was much faster in the turf form of Schistidium and tomenlose form of Bryum, although this trend was reversed when expressed as percentage of the initial water content. Minimal water contents arc achieved by the lichens in desiccating conditions within 6-12 hours, whereas the mosses take several times longer. The water relations characteristics of these cryptogams are considered in the light of their distribution in the field and of their metabolic activity under prevailing Antarctic conditions.