The PIRLA Project (Paleoecological Investigation of Recent Lake Acidification): Preliminary Results for the Adirondacks, New England, N. Great Lakes States, and N. Florida

The PIRLA project is an interdisciplinary paleoecological study designed to provide reconstructions of the recent acidification histories of a representative set of lakes in four acid-sensitive regions in North America. We are trying to determine if lakes in the study regions have acidified, and if so, to what extent, over what time period and why. Sediment cores from 5 to 15 lakes in each region are being analyzed for several characteristics. Diatoms and chrysophytes are being used to reconstruct lakewater pH. Results for three Adirondack lakes with current pH of 4.8 to 5.0 indicate a decrease in pH beginning in the 1930\u27s-1950\u27s. Increased atmospheric deposition of strong acids appears to be the primary factor responsible for the pH decline. Two lakes (pH 4.4 and 4.7) in New England show clear evidence of acidification probably due to acidic deposition. Preliminary reconstructions for two lakes in Michigan (pH 4.4 and 5.6), one in Wisconsin (pH 5.3), and one in Minnesota (pH 6.8) suggest no recent pH decrease. For, the one Florida lake (pH 4.4) analyzed, inferred pH decreases by about 0.5 unit, beginning in the 1950s; the cause has not been determined

Dry Creek Long Term Watershed Study: Buffer Zone Performance as Viable Amphibian Habitat

As bioindicators, amphibians typically require both terrestrial and aquatic habitats to complete their life cycles. Pre- timber-harvest monitoring (December 2002 through September 2003) of salamander and frog (Hylidae) populations was conducted in four watersheds of Decatur County, GA. Post- timber-harvest monitoring (December 2003 through September 2004) continued in the same watersheds (two reference and two treatment watersheds). Coverboards were used to monitor adult salamanders, larval salamanders were surveyed with dipnet sweeps, and frogs were monitored with vertical PVC pipes. Six salamander species (Desmognathus apalachicolae, Eurycea cirrigera, E. guttolineata, Notophthalmus viridescens, Plethodon grobmani, and Pseudotriton ruber) and five frog species (Hyla chyrsoscelis, H. cinerea, H. femoralis, H. squirella, and Pseudacris crucifer) were recorded. Pre- and post-harvest data were compared to assess changes in amphibian population structure. Larval salamanders were the only amphibian group to decline 1 year after timber-harvest. Further long-term examination of amphibian populations should be continued to assess potential delayed responses to site disturbance

Applicability of Planktonic Biomanipulation for Managing Eutrophication in the Subtropics

Although large-bodied cladocerans such as Daphnia can reduce algal biomass significantly in temperate lakes if freed from fish predation, the applicability of such biomanipulation techniques for eutrophication management in the subtropics and tropics has been examined only recently. Subtropical cladoceran assemblages differ from those of temperate lakes by their low species richness, early summer gameogenesis, and greatly reduced body size. Eutrophic Florida lakes are dominated by pump-filter feeding fish rather than by size selective planktivores as a temperate lakes. Cladocerans in Florida lakes can increase in abundance significantly if freed from fish but fail to have an impact on algal biomass or composition. The greatest potential for using biomanipulation to manage phytoplankton-dominated lakes in the subtropics and tropics lies with phytophagous fish. Future research should concentrate on defining the role of individual fish taxa on phytoplankton composition and community structure, nutrient cycling, and planktonic productivity before embarking on whole lake manipulation projects

Interpretation of Bryozoan Microfossils in Lacustrine Sediment Cores

Bryozoan statoblasts were isolated from the surficial sediments of 30 Florida lakes representing a gradient of trophic conditions. A prerequisite for lake selection was a good data base for water chemistry that was collected within the past 5-10 years. A novel technique of employing 210-Pb as a dilution tracer was used to estimate sedimentation rates for each lake. The net annual accumulation rate for bryozoan statoblasts was calculated for each lake and correlated with twelve physical, chemical, and biological variables. The results suggest that bryozoan distributions are strongly controlled by the extent of the littoral zone and phytoplankton biomass. It appears that bryozoan abundance in excessively weeded lakes may be limited by phytoplankton in spite of the richly developed habitat. Separation of the importance of food requirements from habitat requirements was not possible from this initial survey. © 1986 Dr W. Junk Publishers

Importance of Latitude and Organic Color on Phytoplankton Primary Productivity in Florida Lakes

A characterization of primary productivity patterns in subtropical Florida lakes along increasing gradients of both dissolved organic color and phytoplankton biomass is presented. Volumetric expression of gross primary productivity was more strongly correlated with chlorophyll a and nutrient concentrations than was areal expression. Primary production in clearwater ( \u3c 75 Pt units) lakes was more predictable than colored ( \u3e 75 Pt units) lakes. Areal production in Florida lakes was intermediate to the tropical and temperate regions, although volumetric productivity during the vegetative season (May–September) was not significantly different from temperate zone lakes for the same period. Predictive abilities of empirical equations describing primary productivity in Florida lakes are improved by distinguishing colored and clear lakes