Trajectories Of Zooplankton Recovery In The Little Rock Lake Whole-Lake Acidification Experiment

Trout Lake Station, Center for Limnology, University of Wisconsin, 10810 County Highway N, Boulder Junction, Wisconsin 54512, USA.
Ecological Applications (Impact Factor: 4.09). 03/2006; 16(1):353-67. DOI: 10.1890/04-1800
Source: PubMed


Understanding the factors that affect biological recovery from environmental stressors such as acidification is an important challenge in ecology. Here we report on zooplankton community recovery following the experimental acidification of Little Rock Lake, Wisconsin, USA. One decade following cessation of acid additions to the northern basin of Little Rock Lake (LRL), recovery of the zooplankton community was complete. Approximately 40% of zooplankton species in the lake exhibited a recovery lag in which biological recovery to reference basin levels was delayed by 1-6 yr after pH recovered to the level at which the species originally responded. Delays in recovery such as those we observed in LRL may be attributable to "biological resistance" wherein establishment of viable populations of key acid-sensitive species following water quality improvements is prevented by other components of the community that thrived during acidification. Indeed, we observed that the recovery of species that thrived during acidification tended to precede recovery of species that declined during acidification. In addition, correspondence analysis indicated that the zooplankton community followed different pathways during acidification and recovery, suggesting that there is substantial hysteresis in zooplankton recovery from acidification. By providing an example of a relatively rapid recovery from short-term acidification, zooplankton community recovery from experimental acidification in LRL generally reinforces the positive outlook for recovery reported for other acidified lakes.

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    • "Despite substantial improvements, full recovery did not occur in Clearwater and Lohi Lakes, which had lake water pH > 6 since the mid-1990s. Previous studies have suggested that a decade is adequate for zooplankton recovery from acidification (Keller & Yan 1998; Frost et al. 2006). The prolonged damage reported here may be attributable to the severity and extended duration of stress as the lakes were contaminated over 60 years ago (Yan et al. 2004). "
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    ABSTRACT: Clearly defined restoration targets are necessary to judge the effectiveness of management actions in restoring damaged ecosystems. However, the identification of appropriate targets is difficult in a rapidly changing world. Historical reference conditions commonly provide recovery targets, but they may not be appropriate if present-day environments have shifted in response to regional or global drivers. Such shifts may need to be incorporated into restoration targets to avoid erroneous conclusions about the recovery of ecosystems damaged by localized stressors. No previous study has examined whether the selection of historical vs. present-day reference conditions alters judgments of the recovery of historically damaged ecosystems. We examined 35-year trends in the zooplankton communities of four lakes polluted by smelter emissions in Sudbury, Ontario, Canada. Recovery was assessed by comparing the Sudbury lakes to both historical (1983–1984) and present-day (2004–2006) conditions in a set of minimally impacted reference lakes in south-central Ontario. Sudbury zooplankton communities improved substantially over time when compared with both the historical and present-day recovery targets. However, recovery occurred later, and improvements differed quantitatively when judged against the present-day vs. historical targets. These differences were attributable to regional shifts in zooplankton communities that happened after the historical sampling period but were reflected in the present-day data. Species richness in two Sudbury lakes met recovery targets and communities in all four lakes became more similar to those in the reference lakes. However, the continued absence of many daphniids, cyclopoids and large calanoids indicated that the lakes had not fully recovered and further monitoring is needed. Synthesis and applications. Our results show that the choice of reference condition can alter recovery assessments. This finding emphasizes the importance of establishing clearly defined restoration goals to ensure appropriate choice of reference conditions. Restoration is unlikely to be judged as successful if an historical reference point is used to guide management actions meant to restore an ecosystem to present-day regional conditions.
    Journal of Applied Ecology 02/2013; 50(1):107-118. DOI:10.1111/1365-2664.12007 · 4.56 Impact Factor
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    • "Indirect increases in insensitive taxa have in turn been associated with a delayed recovery of sensitive taxa. From observations in a field study, Frost et al. (2006) concluded that the recovery of sensitive zooplankton taxa from acidification was delayed by inter- specific competition with acid-resistant taxa. Furthermore, a direct quantitative relationship between interspecific competition and long-term effects on abundance was identified recently for the recovery of daphnids from exposure to pyrethroids under laboratory (Foit et al., 2011) and semi-field conditions (Knillmann et al., 2012). "
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    ABSTRACT: Considerable research efforts have been made to predict the influences of climate change on species composition in biological communities. However, little is known about how changing environmental conditions and anthropogenic pollution can affect aquatic communities in combination. We investigated the influence of short warming periods on the response of a zooplankton community to the insecticide esfenvalerate at a range of environmentally realistic concentrations (0.03, 0.3 and 3 μg L(-1) ) in 55 outdoor pond microcosms. Warming periods increased the cumulative water temperature, but did not exceed the maximum temperature measured under ambient conditions. Under warming conditions alone the abundance of some zooplankton taxa increased selectively compared to ambient conditions. This resulted in a shift in the community composition that had not recovered by the end of the experiment, 8 weeks after the last warming period. Regarding the pesticide exposure, short-term effects of esfenvalerate on the community structure and the sensitive taxa Daphnia spp. did not differ between the two temperature regimes. In contrast, long-term effects of esfenvalerate on Daphnia spp., a taxon that did not benefit from elevated temperatures, were observed twice as long under warming than under ambient conditions. This resulted in long-term effects on Daphnia spp. until 4 months after contamination at 3 μg L(-1) esfenvalerate. Under both temperature regimes, we identified strength of interspecific competition as the mechanism determining the time until recovery. However, enhanced interspecific competition under warming conditions was prolonged and explained the delayed recovery of Daphnia spp. from esfenvalerate. These results show that, for realistic prediction of the combined effects of changing environmental factors and toxicants on sensitive taxa, the impacts of stressors on the biotic interactions within the community need to be considered.
    Global Change Biology 01/2013; 19(5). DOI:10.1111/gcb.12151 · 8.04 Impact Factor
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    • "nd Peterson et al . ( 2003 ) . Another example is a study on lake acidification where sensitive zooplankton species did not recover until 1 – 6 years after the pH of the lake had been restored to control conditions . It was assumed that the recovery of species sensitive to acidification was delayed by competi - tion from acid - resistant species ( Frost et al . 2006 ) . However , to our knowledge , no direct connection has been established between increases in the abundance of less sensitive species and the delayed recovery of sensitive populations in a community context under conditions that closely resemble those in the field . The aim of the study described herein was to investigate the effects "
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    ABSTRACT: Xenobiotics alter the balance of competition between species and induce shifts in community composition. However, little is known about how these alterations affect the recovery of sensitive taxa. We exposed zooplankton communities to esfenvalerate (0.03, 0.3, and 3 μg/L) in outdoor microcosms and investigated the long-term effects on populations of Daphnia spp. To cover a broad and realistic range of environmental conditions, we established 96 microcosms with different treatments of shading and periodic harvesting. Populations of Daphnia spp. decreased in abundance for more than 8 weeks after contamination at 0.3 and 3 μg/L esfenvalerate. The period required for recovery at 0.3 and 3 μg/L was more than eight and three times longer, respectively, than the recovery period that was predicted on the basis of the life cycle of Daphnia spp. without considering the environmental context. We found that the recovery of sensitive Daphnia spp. populations depended on the initial pesticide survival and the related increase of less sensitive, competing taxa. We assert that this increase in the abundance of competing species, as well as sub-lethal effects of esfenvalerate, caused the unexpectedly prolonged effects of esfenvalerate on populations of Daphnia spp. We conclude that assessing biotic interactions is essential to understand and hence predict the effects and recovery from toxicant stress in communities.
    Ecotoxicology 02/2012; 21(4):1039-49. DOI:10.1007/s10646-012-0857-8 · 2.71 Impact Factor
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