Carl L. Schofield

Aluminum Toxicity to Fish in Acidic Waters

An important consequence of acidification is the mobilization of Al from the edaphic to the aquatic environment. Elevated Al levels in acidic waters may be toxic to fish. Eggs, larvae, and postlarvae of white suckers (Catostomus commersoni) and brook trout (Salvelinus fontinalis) were exposed in laboratory bioassays to pH levels 4.2 to 5.6 and inorganic Al concentrations of 0 to 0.5 mg l−1. Aluminum toxicity varied with both pH and life history stage. At low pH levels (4.2 to 4.8), the presence of Al (up 0.2 mg l−1 for white suckers; 0.5 mg l−1 for brook trout) was beneficial to egg survival through the eyed stage. In contrast, Al concentrations of 0.1 mg l−1 (for white suckers) or 0.2 mg l−1 (for brook trout) and greater resulted in measurable reductions in survival and growth of larvae and postlarvae at all pH levels (4.2 to 5.6). Aluminum was most toxic in over-saturated solutions at pH levels 5.2 to 5.4. The simultaneous increase in Al concentration with elevated acidity must be considered to accurately assess the potential effect of acidification of surface waters on survival of fish populations.

Aluminum leaching response to Acid precipitation: effects on high-elevation watersheds in the northeast.

Atmospheric inputs of sulfuric acid and nitric acid to noncalcareous higher-elevation watersheds in the White Mountain and Adirondack regions lead to comparatively high concentrations of dissolved aluminum in surface and ground waters. This phenomenon appears to result from modern increases in soil aluminum leaching. Transport of this aluminum to acidified lakes can lead to fish mortality. Combined results from areas of silicate bedrock in the United States and Europe suggest that aluminum represents an important biogeochemical linkage between terrestrial and aquatic environments exposed to acid precipitation.

The role of dissolved organic carbon in the chemistry and bioavailability of mercury in remote Adirondack lakes

A number of recent studies have documented elevated concentrations of mercury (Hg) in fish caught in remote lakes and a pattern of increased concentrations of Hg in fish tissue with decreasing water column pH. Because of the potential linkage between fish Hg and surface water acidification, factors regulating water column concentrations and bioavailability of Hg were investigated in Adirondack lakes through a field study and application of the Mercury Cycling Model (MCM). Concentrations of total Hg and total MeHg were highly variable, with concentrations of total MeHg about 10% of total Hg in lakes which did not show anoxic conditions. In lakes exhibiting anoxic conditions in the hypolimnion during summer stratification, concentrations of total MeHg were elevated. Concentrations of total Hg and total MeHg increased with decreasing pH in remote Adirondack lakes. However, more importantly, concentrations of total Hg and total MeHg increased with increasing concentrations of dissolved organic carbon (DOC) and percent near-shore wetlands in the drainage basin. Mercury concentrations in muscle tissue of yellow perch from Adirondack lakes were elevated above the U.S. FDA action level (1 μg/g Hg) in 7% of the fish sampled or in one or more individual fish from 9 of the 16 lakes sampled. Fish Hg concentrations generally increased with increasing fish length, weight and age. Patterns of increasing Hg concentration with age likely reflect shifts in prey of yellow perch and the bioconcentration of Hg along the food chain. For age 3 to 5 perch, concentrations of Hg increased with increasing concentrations of DOC and percent near-shore wetlands in the drainage basin. However, for a lake with very high DOC concentrations, fish concentrations of Hg declined. Calculations with the MCM also show that concentrations of Hg species increase with increasing DOC due to complexation reactions. Increases in DOC result in increasing concentrations of Hg in biota but decreases in the bioconcentration factor of Hg in fish tissue. This research suggests that DOC is important in the transport of Hg to lake systems. High concentrations of DOC may complex MeHg, diminishing its bioavailability. At high concentrations of monomeric Al, the complexation of MeHg with DOC apparently decreases, enhancing the bioavailability of MeHg.

The chemistry and transport of mercury in a small wetland in the Adirondack region of New York, USA

The biogeochemistry of Hg was evaluated in a small wetland in the Adirondack region of New York. Concentrations of total Hg (HgT) in streamwater draining the wetland showed little temporal variation. The annual areal watershed flux of HgT (2.2 µg/m2-yr) was considerably smaller than regional inputs of atmospheric deposition of HgT, indicating that the terrestrial environment is a net sink for atmospheric deposition of HgT. Drainage inputs of HgT were conservatively transported through the beaver impoundment. The annual flux of total methyl mercury (CH3Hg+T was greater than literature values of atmospheric deposition suggesting that the watershed is a net source of CH3Hg+T . Stream concentrations of CH3Hg+T increased during low-flow summer conditions in a riparian wetland, and particularly at the outlet of the beaver impoundment. Net production of CH3Hg+T occurred in the beaver impoundment (0.45 µg/m2-yr). Rates of net methylation for the beaver impoundment were comparable to values reported in the literature for wetlands.

Aluminum Toxicity to Brook Trout (Salvelinus Fontinalis) in Acidified Waters

Aluminum was identified as a primary toxicant present in acidic, snow-melt runoff and lakes in the Adirondack Mountain region of New York. Covariance analysis of water quality data from fifty three Adirondack lakes suggested that stocked brook trout survival was determined primarily by aluminum concentrations, rather than pH or calcium levels. Lakes not supporting brook trout had a mean aluminum concentration of 0.29 mg/liter, as compared to 0.11 mg/liter of aluminum in lakes where stocked brook trout survived. Comparisons of mortality and gill pathology of brook trout exposed to acidic synthetic solutions and natural Adirondack waters with aluminum levels above 0.2 mg/liter, indicated a specific toxic response to aluminum at pH levels down to 4.4. An apparent increase in toxicity of fixed total aluminum levels with increasing pH suggested that changes in speciation involving hydroxy complexing enhances the toxicity of the aluminum cation.

Aluminum toxicity in forests exposed to acidic deposition: The ALBIOS results

The ALBIOS project was conducted to examine the influence of acidic deposition on aluminum transport and toxicity in forested ecosystems of eastern North America and northern Europe. Patterns of aluminum chemistry were evaluated in 14 representative watersheds exposed to different levels of sulfur deposition. Controlled studies with solution and soil culture methods were used to test interspecific differences in aluminum sensitivity for one indicator species (honeylocust - Gleditsia triacanthos L. ) and six commercial tree species (red spruce - Picea rubens Sarg., red oak - Quercus rubra L., sugar maple - Acer saccharum Marsh., American beech - Fagus grandifolia Ehrh., European beech - Fagus sylvatica, and loblolly pine - Pinus Taeda L. ). Overall, red spruce was the tree species whose growth was most sensitive to soluble aluminum, with significant biomass reductions occurring at Al concentrations of approximately 200–250 umol/L. Analyses of soil solutions from the field sites indicated that the conditions for aluminum toxicity for some species exist at some of the study areas. At these watersheds, aluminum toxicity could act as a contributing stress factor affecting forest growth.

Fish species distribution in relation to water quality gradients in the North Branch of the Moose River Basin

The distribution of fish species in the North Branch of the Moose River (Lake Rondaxe to headwaters of Big Moose Lake) was determined by intensive netting and electrofishing surveys of lakes and streams in the watershed during 1982–83. A chronology of changes in fish species occurrence in the drainage system was reconstructed from earlier published surveys conducted in 1882 and 1931 and unpublished survey data obtained by the NYSDEC during the period 1948–1975. Native species present in 1882 were also collected in 1931. Smallmouth bass (Micropterus dolomieu) were introduced in the early 1900s and were present in collections made in 1931. Major changes in the fish community have taken place since 1931. The smallmouth bass and many of the native species found in the earlier surveys were either absent or restricted in occurrence to downstream sites (eg. L. Rondaxe and Moss L. sub-drainage) in 1982. Non-native species introduced after 1931 (yellow perch,Perca flavescens; central mudminnow,Umbra limi; banded killifish,Fundulus diaphanus) are currently widely distributed throughout the drainage system. In particular, the yellow perch is now a dominant species in the larger lakes of the basin. Comparisons of survival rates for caged fish transferred from high to low pH sites in the Big Moose drainage system demonstrated relatively greater acid tolerane of non-native species (yellow perch, mudminnow, killifish) than native cyprinids. Watershed acidity gradients (pH and aluminum concentrations) and relative physiological acid tolerance are major determinants of currently observed fish species distribution patterns in the North Branch of the Moose River. Differences in age and size structure of fish populations inhabiting acidic and non-acidic lakes of the drainage system were apparent, but difficult to interpret without additional information onpopulation size and potential density dependent parameters such as age specific growth and survival rates. Differential hatching success was observed for yellow perch eggs reciprocally transferred between acid (Big Moose) and neutral (Moss L.) lakes. Eggs transferred from Moss L. to Big Moose L. exhibited poor hatching success as a result of alterations in egg membrane structure that inhibited normal egg expansion and the hatching process. This effect was not evident in eggs from the same parents reared in Moss Lake nor in eggs from the Big Moose parents reared in both lakes. These experimental observations suggested possible genetic adaptation to acid stress by the yellow perch population inhabiting Big Moose Lake.

Effects of acid precipitation

Acid precipitation, including dry deposition, is recognized as coming from pollution-caused strong acid precursors that result from the burning of fossil fuels. Recent studies suggest that ecosystems susceptible to acidification occur over the entire length of the Appalachian Mountains and certain other regions of the eastern U.S. This paper reviews a short-term assessment by the EPA to survey the extent of the effects of acid precipitation on the environment, and focuses on New York state. Data from Pennsylvania and Virginia show effects of streams. Studies of the impacts of acid rain on crop yields and model forest ecosystems are generic and apply to no particular state or region.(KRM)

The Experimental Watershed Liming Study: Comparison of lake and watershed neutralization strategies

The Experimental Watershed Liming Study (EWLS) was initiated to evaluate the application of CaCO3 to a forested watershed in an effort to mitigate the acidification of surface water. The objective of the EWLS was to assess the response of the Woods Lake watershed to an experimental addition of CaCO3. During October 1989,6.89 Mg CaCO3/ha was applied by helicopter to two subcatchments comprising about 50% (102.5 ha) of the watershed area. The EWLS involved individual investigations of the response of soil and soil water chemistry, forest and wetland vegetation, soil microbial processes, wetland, stream and lake chemistry, and phytoplankton and fish to the CaCO3 treatment. In addition, the Integrated Lake/Watershed Acidification (ILWAS) model was applied to the site to evaluate model performance and duration of the treatment. The results of these studies are detailed in this volume. The purposes of this introduction and synthesis paper are to: 1) present the overall design of the EWLS, 2) discuss the linkages between the individual studies that comprise the EWLS, and 3) summarize the response of the lakewater chemistry to watershed addition of CaCO3 and compare these results to previous studies of direct lake addition. An analysis of lake chemistry revealed the watershed treatment resulted in a gradual change in pH, acid neutralizing capacity (ANC) and Ca2+ in the water column. This pattern was in contrast to direct lake additions of CaCO3 , which were characterized by abrupt changes following base addition and subsequent rapid reacidification. Over the three-year study period, the supply of ANC to drainage waters was largely derived from dissolution of CaCO3 in wetlands. Relatively little dissolution of CaCO3 occurred in freely draining upland soils. The watershed treatment had only minor effects on forest vegetation. The watershed treatment eliminated the episodic acidification of streamwater and the near-shore region of the lake during snowmelt, a phenomenon that occurred during direct lake treatments. Positive ANC water in the near-shore area may improve chemical conditions for fish reproduction, and allow for the development of a viable fish population. The watershed CaCO3 treatment also decreased the transport of A1 from the watershed to the lake, and increased the concentrations of dissolved organic carbon (DOC) and dissolved silica (H4SiO4) in stream and lakewater. The watershed treatment appeared to enhance soil nitrification, increasing concentrations of NO3 - in soilwater and surface waters. However, the acidity associated with this NO3 - release was small compared to the increase in ANC due to CaCO3 addition and did not alter the acid-base status of Woods Lake. Acid neutralizing capacity (ANC) budgets for 12-month periods before and after the watershed treatment showed that the lake shifted from a large source of ANC to a minor source due to retention of SO4 2-, NO3 -, Al and the elevated inputs of Ca2+ associated with the watershed CaCO3 application. In contrast to the direct lake treatments, Ca2+ inputs from the watershed application were largely transported from the lake.

Geological and hydrochemical sensitivity of the eastern United States to acid precipitation

A new analysis of bedrock geology maps of the eastern US constitutes a simple model for predicting areas which might be impacted by acid precipitation and it allows much greater resolution for detecting sensitivity than has previously been available for the region. Map accuracy has been verified by examining current alkalinities and pHs of waters in several test states, including Maine, New Hampshire, New York, Virginia and North Carolina. In regions predicted to be highly sensitive, alkalinities in upstream sites were generally low. Many areas of the eastern US are pinpointed in which some of the surface waters, especially upstream reaches, may be sensitive to acidification. Pre-1970 data were compared to post-1975 data, revealing marked declines in both alkalinity and pH of sensitive waters of two states tested, North Carolina, where pH and alkalinity have decreased in 80% of 38 streams and New Hampshire, where pH in 90% of 49 streams and lakes has decreased since 1949. These sites are predicted to be sensitive by the geological map on the basis of their earlier alkalinity values. The map is to be improved by the addition of a soils component.