Increases in Dissolved Organic Carbon Accelerate Loss of Toxic Al in Adirondack Lakes Recovering from Acidification

Abstract

Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

Decoupled trophic responses to long‐term recovery from acidification and associated browning in lakes

“…For example, in the Adirondack Mountains region of New York, USA, long‐term recovery from acidification has stimulated substantial long‐term browning, altered acid/base chemistry, and modified ion cycling between soil and aquatic ecosystems (Driscoll et al, ; Likens, Bormann, & Johnson, ). Recovery from soil acidification has reduced aluminum run‐off to sub‐toxic thresholds, allowing extirpated fish populations to recover at some sites (Josephson, Robinson, Chiotti, Jirka, & Kraft, ; Lawrence, Dukett, Houck, Snyder, & Capone, ; Michelena et al, ) and has caused widespread, long‐term declines in biologically important calcium concentrations (Hessen, Andersen, Tominaga, & Finstad, ; Jeziorski et al, ; Skjelkvåle et al, ). The severity of acidification and extent of soil recovery may also control the export of phosphorus from the landscape into inland waters via non‐linear, pH‐dependent processes (Kopáček, Hejzlar, Kaňa, Norton, & Stuchlík, ), which in turn may control ecosystem productivity.…”

Acidification Impacts and Goals for Gauging Recovery of Brook Trout Populations and Fish Communities in Streams of the Western Adirondack Mountains, New York, USA

“…; Lawrence et al. , ). With few exceptions, however, information on unimpacted (pre‐acidification) fish assemblages, along with past and contemporary impacts of acidification on fish populations and communities, is lacking for streams across acid‐sensitive regions of New York State.…”

“…Numerous studies in the northeastern USA over the past four decades have established strong linkages between acidic deposition, soil and water acidification, and toxicity in headwater streams (Driscoll et al 1980(Driscoll et al , 2007Baker et al 1996;Baldigo et al 2007;Lawrence et al 2008bLawrence et al , 2013. With few exceptions, however, information on unimpacted (pre-acidification) fish assemblages, along with past and contemporary impacts of acidification on fish populations and communities, is lacking for streams across acid-sensitive regions of New York State.…”

Trends in Levels of Allochthonous Dissolved Organic Carbon in Natural Water: A Review of Potential Mechanisms under a Changing Climate

“…All of the 22 UKAWMN sites showed DOC concentration increases, with an average increase of 91% over a 15 year period [9]. In the U.S., general increases in DOC levels have been reported in the waters of the Adirondack and Catskill Mountain regions of New York State [8,75,81,84,85,96]. Monitored sites in Vermont and Maine showed a few areas of small to moderate rises in DOC levels, while Pennsylvania did not show general increases [8,84].…”