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

Abstract

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.

Recovery of zooplankton diversity in a restored Mediterranean temporary marsh in Doñana National Park (SW Spain)

“…Zooplankton recovery after restoration of acidified lakes can be highly successful, at least for some taxa (Yan et al, 2004, Gray & Arnott, 2009. After an experimental acidification of an 18 ha lake during 6 years, the zooplankton community returned to reference levels after another 6 years (Frost et al, 2006). Factors determining the recovery speed of individual taxa include the length of the degradation period prior to restoration, and the life-history of the zooplankter (Knapp & Sarnelle, 2008).…”

Biological barriers to restoration: testing the biotic resistance hypothesis in an upland stream recovering from acidification

“…Stoneflies occur commonly in upland streams and abundances can increase dramatically under high acidity, reflecting compensatory dynamics arising as resources are released by species deletions (Ledger & Hildrew, 2005;Frost et al, 2006;Tixier et al, 2012). We have shown elsewhere that species within the order feed (Ledger & Hildrew, 2000a) and grow (Ledger & Hildrew, 2001a, b) on the sparse algal layers of impoverished acid streams, and it could be that as acidity declines, recolonists such as baetid mayflies face competition with these highly abundant, herbivorous residents.…”

“…However, where biotic factors intervene, as revealed in recovering lakes (e.g. Keller & Yan, 1998;Holt & Yan, 2003;Vinebrooke et al, 2003;Frost et al, 2006), niches may be filled or modified by residents (Sudling et al, 2004), shifting successional endpoints as acidity declines. Although the research reported here found no evidence for competition as a mechanism limiting biological recovery, we have addressed just one competitive interaction, within the benthic food web, at one point in time.…”

“…Evidence of 'competitive resistance' has been found in acidified lake communities (e.g. Keller & Yan, 1998;Holt & Yan, 2003;Vinebrooke et al, 2003;Frost et al, 2006), where delayed recovery of algal and zooplankton communities following chemical restoration has been attributed to competition with persistent acidtolerant species, but support in streams remains circumstantial.…”

Seasonal dynamics and life histories of pelagic cladocerans (Crustacea; Cladocera) in an acid boreal lake

“…The major stress from the water chemistry is probably low pH, frequently below pH 5.3, and the increased level of RAl (150-250 µg L -1 ). These concentrations are noticeable and indicate that many species of phytoplankton, zooplankton, and fish are sublethally, negatively affected by the lake water (Hörn-ström & Ekström 1983;Hörnström et al 1984;Marmorek & Korman 1993;Hesthagen et al 2001;Frost et al 2006). Nevertheless, perch still produced a considerable biomass in Lake Gjerstadvann.…”