William E. Sharpe

Three-component tracer model for stormflow on a small appalachian forested catchment

Abstract A three-component 18 O tracer model recognizing contributions of groundwater, soil water and channel precipitation was used to represent stormflow in Fish Run, a small Appalachian Plateau forest stream. The traditional two-component model recognizing “old” and “new” water stormflow sources failed to explain runoff events in Fish Run, often giving “old” water percentages of stormflow exceeding 100%. With the three-component model, channel precipitation contributions were computed from measured throughfall intensity and channel area. Example computations for a low-intensity frontal rainfall event using the three-component model gave stormflow contributions of 0.9% for channel precipitation, 24.1% for soil water and 75% for groundwater. Contributions of soil water to stormflows may explain levels of dissolved aluminum toxic to fish found in several Appalachian Plateau streams.

Macroinvertebrate community structure and detritus processing rates in two southwestern Pennsylvania streams acidified by atmospheric deposition

A one-year study of benthic macroinvertebrate communities and leaf litter decomposition rates was conducted on Wildcat and McGinnis Runs, two headwater tributaries of Rolling Rock Creek in southwestern Pennsylvania. Previous studies have shown these two streams to be affected by acidic runoff following periods of precipitation and snow-melt. The more highly buffered waters of Wildcat Run support wild fish populations while McGinnis Run lacks native fish fauna. Five benthic macroinvertebrate samples were taken from riffle areas in each stream using a Surber sampler during the spring, summer, fall, and winter seasons. Thirty 10-g packs of white ash (Fraxinus americana) leaves were placed in each stream on October 7, 1982, and sampled over a 5-month period to determine per cent weight loss. The benthic macroinvertebrate community of McGinnis Run was found to be depressed compared to that of Wildcat Run in terms of density, diversity, and total taxa. The overall rate of leaf-litter decomposition was also slower in McGinnis Run.

The effect of soil nutrition, soil acidity and drought on northern red oak (Quercus rubra L.) growth and nutrition on Pennsylvania sites with high and low red oak mortality

Unexplained mortality of northern red oak (Quercus rubra L.) has occurred on the Laurel Hill in southwestern Pennsylvania. We attempted to characterize this mortality and determine its relationship to soil acidity, soil nutrient status and droughts. Three blocks with high and low mortality of northern red oak were selected. Basal area increment, terminal elongation and leaf mass were measured along with soil chemistry. Basal area growth patterns were compared to historic drought records. Both living and standing dead trees on high mortality plots had been responsive to most of these droughts. After 2 years of droughts in the 1960s, basal area growth rate of trees on high mortality plots did not recover. In addition, the standing dead trees on high mortality plots were historically a less vigorous subset. After this mortality, the living trees did not respond with increased growth due to thinning of competitors. Basal area growth on low mortality plots did recover after these same droughts and mortality was limited. In addition, the trees on the high mortality plots showed foliar deficiency of K and low levels of Ca while trees on the low mortality plots did not. Furthermore, the A- and B- horizons of the soils on the high mortality plots had lower levels of soil bases, higher levels of available Al and lower Ca/Al ratios. The results of this study suggest that nutrient deficiency and associated Al toxicity may be causing stress for northern red oaks and is related to the mortality and reduced growth of northern red oak in this region.

LONG-TERM CHANGES IN FOREST SOIL ACIDITY IN PENNSYLVANIA, U.S.A.

Forest soil acidification has been reported to cause reduced forest productivity and decline of some tree species. Soil acidification may cause increased bioavailability of Al and Mn, which are potentially phytotoxic. In an attempt to measure whether or not Pennsylvania forest soils have become more acidic, soil samples were collected at 11 undisturbed forested sites in Pennsylvania in 1993. Limited soil chemistry data obtained through 4 previous studies conducted between 1957 and 1979 were available for each site. Soil pH and concentrations of exchangeable Ca and Mg were measured; results were compared to those obtained in earlier studies. Soil exchangeable Al concentrations were determined for 6 sites for which previous data were available. Chemical analysis methods were evaluated to ensure that methods used in 1993 were comparable to those of the original investigators. Mean pH and exchangeable Mg declined most consistently over the study period in the O horizon and the uppermost A horizon. Mean exchangeable AI decreased in the O horizon and increased in the A horizon. Given the high sulfate and nitrate deposition loads in Pennsylvania, it seems likely that the observed changes are at least in part a consequence of acidic deposition.

Mortality of brook trout, mottled sculpins, and slimy sculpins during acidic episodes

Abstract Brook trout Salvelinus fontinalis, mottled sculpins Cottus bairdi, and slimy sculpins Cottus cognatus occur in many Pennsylvania streams that have depressed pH and elevated aluminum concentrations during episodes of high stream discharge (acidic episodes). We performed 20-d in situ cage exposures with these species to determine their relative sensitivities to field conditions. We also exposed fish in the laboratory to synthetic soft water, without added Al, to elevate possible effects of Al on sodium flux rates and pH toxicity. Exposures were in five streams: Two with high pH (>5.60) and low Al concentrations (<80 μg/L) and three with low pH (usually between 5.0 and 5.5) and high Al levels (124–294 μg/L). Exposures were during two low-discharge fall periods, when pH tends to be seasonally higher and Al concentrations lower, and two relatively high-discharge spring seasons, when lower pH and higher Al concentrations are typical. Few fish died (generally < 10%) in the two streams that had higher pH...

Water chemistry and fish community responses to episodic stream acidification in Pennsylvania, USA.

Five streams were studied on the Northern Appalachian Plateau of Pennsylvania from October 1988 through June 1989 to determine chemical changes that occur during episodic storm run-off and the responses of fish to these events. These second-order streams flowed through undisturbed, wooded, sandstone bedrock catchments with surface areas ranging from 500 to 1000 hectares. Median pH of precipitations was about 4.2, and among streams it ranged from 5.0 to 6.2. During storm events, pH declined by as much as 1.2 units and peak concentrations of total monomeric Al ranged from < 0.01 to 0.75 mg litre(-1). Organically bound A1 was generally a minor component of total monomeric A1. Wild brook trout (Salvelinus fontinalis) were found in all streams, although only a remnant population existed in the most acidic stream. Sculpins (Cottus bairdi or C. cognatus) were collected only in the two streams with the least severe episodes. Mortality of brook trout and sculpins in in situ bioassays ranged from 0 to about 80% among streams during acidic episodes and was positively related to concentrations of total dissolved Al. Radio-tagged brook trout moved downstream during episodes when Al reached toxic concentrations. Some displaced trout were found near groundwater seeps, where pH was higher and dissolved Al was lower than in the main channel.

Comparison of soil water chemistry and sample size requirements for pan vs tension lysimeters

A study was conducted to compare soil leachate chemistry and determine sample size requirements for tension vs pan (zero-tension) lysimeters. Analyses were performed on an annual and seasonal basis for one year of data collected at Pea Vine Hill, a forested site in southwestern Pennsylvania. On an annual basis, SO4−2, Ca+2, Mg+2, Mn+2, K+ and specific conductance were significantly higher in tension lysimeter samples but no chemical species were significantly higher in pan lysimeters. Seasonal comparisons indicated chemical differences between lysimeter types were variable with more significant deviations present during wet periods. Nearly all significant seasonal differences were comprised of higher concentrations in tension compared to pan lysimeters. Disparities in leachate chemistry between lysimeter types were ascribed to different sources of water collected by the instruments especially during wet periods. Sample size requirements were calculated for two biweekly periods for each lysimeter type at three confidence levels. Based upon calculated sample demands, pan lysimeter soil leachate chemistry could be characterized with fewer samples than tension lysimeters. Less than .30 samples were generally necessary for pan B-horizon lysimeters at the 70% confidence level. Sample requirements were usually unreasonable at higher confidence levels.

Net sodium loss and mortality of three salmonid species exposed to a stream acidified by atmospheric deposition.

Death of freshwater fish exposed to low pH is primarily due to failure of sodium regulation. Low pH reduces sodium influx and greatly increases efflux resulting in a net loss of sodium. Ionoregulatory failure may trigger circulatory collapse which finally causes death. A fish experiencing net loss of blood salts may be able to mobilize salts from elsewhere in the body; therefore, a study of concentrations of ions in the blood provides less information than one of net ion balance with respect to pH and/or aluminum toxicity. The present study was initiated to determine whether or not aluminum accelerates net sodium loss in fish exposed to pH 5.0 soft water (calcium <5 mg/L) and if so, to discover whether or not the magnitude of loss might account for mortality of fish in waters acidified by atmospheric deposition.

An Examination of Environmental Factors Associated with Myxobolus cerebralis Infection of Wild Trout in Pennsylvania

Abstract Salmonid whirling disease, caused by the myxosporean parasite Myxobolus cerebralis, was first observed in the United States in 1956 in central Pennsylvania. The parasite was subsequently discovered at several culture facilities throughout the state, and widespread distribution of this parasite via the stocking of subclinically infected brook trout Salvelinus fontinalis, rainbow trout Oncorhynchus mykiss, and brown trout Salmo trutta has been assumed. Although no monitoring of wild populations occurred until the late 1970s, it is a common belief that epizootics of whirling disease, now realized in the Intermountain West, are unlikely to have occurred in Pennsylvania. We conducted a review of historical information and a synoptic survey aimed at identifying factors that may prevent whirling disease outbreak in this region, reasoning that such information might be useful in identifying management strategies for populations affected by this parasite. Here we present data on parasite prevalence, fish ...

The Influence of Acidic Runoff Episodes on Slimy Sculpin Reproduction in Stone Run

Abstract Much research has been devoted to the effects of acidic runoff episodes on populations of brook trout Salvelinus fontinalis. Less is known about slimy sculpin Cottus cognatus and why their numbers have declined in acidified streams. Adult tolerance of low pH and aluminum (Al) toxicity is similar in these two species. Slimy sculpin spawn in the spring, when high stream flows elevate concentrations of toxic Al and decrease stream pH in acid-sensitive watersheds. We hypothesized that acidic episodes in spring were a source of stress for slimy sculpin and hindered their reproduction. We tested this hypothesis by examining the mortality, behavior, whole-body sodium concentrations, and spawning among slimy sculpin exposed to ambient conditions during the spring spawning period in two Pennsylvania streams, Stone Run (an episodically acidified stream that formerly contained slimy sculpin) and Benner Run (a stream with slimy sculpin that does not experience severe acidic episodes). Our hypothesis was supp...