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

Abstract

Anthropogenic acidification has affected biota in thousands of lakes in eastern North America and Europe. To measure the degree and extent of biological recovery following pH recovery in acidified lakes, many studies have assessed changes occurring in acid-damaged zooplankton communities. In this review we synthesize studies of zooplankton recovery from regions severely affected by acidification. In doing so, we provide a critical overview of: (1) the design of studies used to detect recovery; (2) the status of communities in acidified regions; and (3) our current understanding of the factors that limit recovery. The design of most studies assessing zooplankton recovery fall into three categories based on their selection of data to be used for recovery benchmarks: (1) historical; (2) reference-lakes; and (3) temporal. Within these study designs, the most commonly used metrics include species richness, indicator species, and relative species abundances. Many studies have used species richness as the sole indicator of recovery; however, we argue that additional metrics should be considered in analyses to make conclusions more robust. Studies conducted in eastern North America and Northern Europe have demonstrated significant, though often incomplete, recovery of zooplankton communities in lakes that reach a pH > 6.0. Data collected in central Europe indicate little recovery in the heavily affected Bohemian Forest lakes, but complete recovery of species richness in the moderately acidified Tatra Mountain lakes. Factors limiting biological recovery, including slow chemical recovery, dispersal limitation, and community resistance, vary in importance among and within regions, suggesting that region- and lake-specific management approaches may be required.

Forest Die-Back Modified Plankton Recovery from Acidic Stress

“…Despite the indisputable amelioration of chemical conditions, the lake still maintains its acidic status. Our study has confirmed the regional tendency of some littoral species, namely C. quadrangula and M. clavus , to fill empty niches (Keller and Yan 1998;Gray and Arnott 2009).…”

“…This species has likely been spread by a bird vector (e.g., by common ducks, which frequently occur at most water bodies in the region, including Rachelsee). Though we can document several more or less remarkable changes in the plankton of Rachelsee during this study, when assessed by a historical benchmark (Gray and Arnott 2009), there has been hardly any zooplankton recovery observed as no indigenous or circum-neutral species have appeared so far. Despite the indisputable amelioration of chemical conditions, the lake still maintains its acidic status.…”

“…While deposition of acidifying pollutants has substantially declined in Europe and North America, particularly due to sulfur emission controls since 1980s, leading to partial recovery of surface waters from acid stress (Stoddard et al 1999), biological recovery of these areas remains remarkably delayed or uncertain (Jeffries et al 2003;Skjelkvåle et al 2003;Yan et al 2003;Wright et al 2005;Nedbalová et al 2006). Two recent reviews on plankton recovery (Graham et al 2007;Gray and Arnott 2009) discussed this lag and its possible reasons and pointed out certain gaps in our knowledge due to a lack of data and/or methodological constraints.…”

Impacts and prognosis of natural resource development on water and wetlands in Canada’s boreal zone

“…Controls on sulphur dioxide emissions in North America resulted in large reductions in sulphate concentrations and increases in pH in many eastern boreal lakes by the mid-1990s (Keller 2009). Numerous studies are tracking the chemical and biological recovery of water bodies from acidification (Keller et al 1992;Gunn 1995;Carbone et al 1998;Doka et al 2003;Jeffries et al 2003aJeffries et al , 2003bSnucins and Gunn 2003;Clair et al 2007;Keller et al 2007;Gray and Arnott 2009). Overall, these show that the pH of surface waters in most areas near historic industrial operations is improving, but that metal concentrations often remain ele-vated above reference or target levels and that biological recovery usually lags behind chemical recovery.…”

Calcium and sodium as regulators of the recovery of four Daphnia species along a gradient of metal and base cations in metal contaminated lakes in Sudbury, Ontario, Canada

“…From a functional perspective, the presence of a pelagic herbivore community in the study lakes represented by copepods and cladocerans other than Daphnia species could be interpreted as recovery. However, Gray and Arnott (2009) suggest that species richness is not the best indication of recovery; therefore, metrics other than that should be included in the evaluation of recovery trends in the Sudbury lakes. Damaged ecosystems may not always be able to return to a pre-disturbance state, even when the chemical and other biological stressors are removed (Cairns, 1990;Keller, 2009): however, when the species failing to re-establish are one of the most sensitive groups of invertebrates to water quality contaminants such as daphniids, one can conclude that the habitat is still stressful assuming that recovery has not been limited by colonist supply.…”