Recovery from acidification in boreal lakes inferred from macroinvertebrates and subfossil chironomids

Abstract

Acidification of waters and soils caused by emissions and the long-range transport of air pollutants has been a serious worldwide problem during the last decades. The extent of the acidification problem in Finnish acid-sensitive forest lakes was examined in the Acidification Research Project (HAPRO) in the mid-1980s. The recent decline in the emissions of air pollutants has resulted in the chemical recovery of watersheds in many regions, and the present work on the recovery processes in acidified Finnish headwater lakes (REPRO) was launched to examine whether the chemical recovery has already been accompanied by biological recovery. The patterns of recovery were studied by re-sampling littoral macrozoobenthos in a subset of the previously sampled HAPRO lakes. Paleolimnological samples were taken in order to assess the possible dependence of lacustrine chironomid communities on the changing degree of acidification. Acid sensitive and moderately acid sensitive benthic species revealed slight recovery in the formerly most acidic (pH £ 5.5) but recently recovered lakes. The most significant factors affecting the response of benthic communities were increased mean lake pH and decreased labile aluminium concentration. Paleolimnological chironomid analysis revealed a slight response along the pH gradient, but also significant structural similarity between the present and pristine chironomid assemblages. This implies that no major changes in chironomid communities of these acidic lakes have occurred during the past centuries. The alternative future trends and threats to biological recovery in small headwater lakes are discussed.

Recovery of acid damaged zooplankton communities: measurement, extent, and limiting factors

“…Legislation and international treaties developed throughout the 1970s and 1980s mandated emissions reductions that have led to increased pH levels for precipitation and surface water in many regions of North America and Europe (Stoddard et al 1999;Driscoll et al 2001;Vestreng et al 2007). Consequently, the chemistry of some affected lakes has recovered to pre-acidification conditions, and biota reduced or extirpated from acidified systems are starting to recover (Yan et al 2004;Hynynen and Merilainen 2005;Monteith et al 2005;Skjelkvåle et al 2007). Despite promising signs of recovery in some regions, several studies have concluded that biological recovery lags behind chemical recovery, and is not yet complete in many systems (Yan et al , 2004Arnott et al 2006;Nedbalová et al 2006;Masters et al 2007).…”

The Dynamics of Macroinvertebrate Assemblages in Response to Environmental Change in Four Basins of the Etueffont Landfill Leachate (Belfort, France)

“…Benthic macroinvertebrate communities have been shown to be widely acceptable in indicating water quality and might effectively reveal the ecological status of aquatic environments (Hynes 1960;Hawkes 1979;Hellawell 1986;Verneaux and Aleya 1998b;Hart and Lovvorn 2005). While there is now abundant literature on the use of macroinvertebrate communities as ecological integrity indicators of aquatic ecosystems (Verneaux and Aleya 1998b;Kay et al 1999;Kimberling et al 2001;Spanhoff et al 2004;Hynynen and Merilainen 2005;Brooks et al 2005;Gandouin et al 2006), little is known about the seasonal variation of macroinvertebrate assemblages in stabilization ponds constructed to treat landfill leachate generated from the biodegradation of municipal solid wastes. These stabilization ponds, which are generally designed to treat only an average quality of the leachate, are commonly put under extreme pressure due to enhanced overload of organic matter.…”

Natural recovery and restoration of acidified shallow soft-water lakes: Successes and bottlenecks revealed by assessing life-history strategies of chironomid larvae

“…Biological recovery has been shown to be modest or lagging behind chemical improvement for macroinvertebrates in recovering acidified lakes and streams (Lancaster et al 1996;Monteith et al 2005;Ormerod & Durance 2009) and for chironomids in acidified lakes (Hynynen & Meriläinen 2005). Our results demonstrate that modest biological recovery or biological improvement lagging behind chemical improvement can be caused by a habitat condition other than pH.…”