Response of zooplankton communities to liquid creosote in freshwater microcosms

Abstract

In this study, the response of zooplankton communities to single applications of liquid creosote in model aquatic ecosystems (microcosms) was evaluated. Liquid creosote was applied to 14 microcosms at concentrations ranging from 0.06 to 109 mg/L. Two microcosms served as controls. Zooplankton samples were collected from each microcosm on days 7 and 1 before treatment and on days 2, 5, 7, 14, 21, 28, 43, 55, and 83 following treatment. Temporal changes (response-recovery) in composition of the zooplankton community were assessed using principal response curves (PRC). Creosote induced a rapid, concentration-dependent reduction in zooplankton abundance and number of taxa, with maximum response (50-100% reduction in population densities) occurring between 5 and 7 d after treatment. Taxa that dominated at the time of treatment experienced the greatest impact, as indicated by large, positive species weight values (> 1) from the PRC analysis. Many of these taxa recovered to pretreatment or control levels during the posttreatment period, with the degree and duration of recovery being strongly dependent on concentration. Creosote had little effect on species composition at less than 1.1 mg/L, because changes in the types and relative proportion of species contributed from Cladocera, Rotifera, and Copepoda were comparable to those observed in control microcosms. However, a significant shift in species composition was observed at concentrations greater than 1.1 mg/L; these microcosms were generally dominated by low numbers of rotifers, some of which had not been collected before treatment. Community-level effect concentrations (EC50s) were 44.6 and 46.6 micrograms/L at 5 and 7 d, respectively, based on nominal creosote. Corresponding no-effect concentrations were 13.9 and 5.6 micrograms/L. The results of this field study indicate that creosote may pose a significant risk to zooplankton communities at environmental concentrations potentially encountered during spills and/or leaching events.

Response of breeding bird communities to forest harvest around seasonal ponds in northern forests, USA

“…PRC is a recent extension of redundancy analysis that distills the complexity of timedependent, community-level responses into a graphic form that is easier to interpret (Van den Brink and ter Braak, 1999). This method has been used as an effective graphical and analytical tool in other ecological experiments having a similar number of experimental units ( Van den Brink and ter Braak, 1999;Sibley et al, 2001;see Hanowski et al, 2003see Hanowski et al, , 2005 for more details and examples).…”

Response of the zooplankton community and environmental fate of perfluorooctane sulfonic acid in aquatic microcosms

“…The focus of this research was to investigate the ecotoxicological responses associated with single spill events causing relatively high concentrations of PFOS across levels of biological organization in model pond ecosystems (microcosms). Such an event was documented by Moody et al [6] where the maximum PFOS concentration in surface waters was 2.2 μg/ L. The microcosms in this study have been used to evaluate fate and effects on freshwater organisms following application of anthropogenic compounds [13–15]. Large microcosm studies are ecologically more relevant than single‐species laboratory tests.…”

Response of phytoplankton communities to liquid creosote in freshwater microcosms

“…Although the creosote dissipated rapidly from treated microcosms, we have retained the use of nominal concentrations to represent the dose to which the phytoplankton were exposed. This is because the response of the phytoplankton community was largely dictated by impacts on zooplankton populations (see below), which occurred predominantly during early stages (<5 d) of the exposure period [12] when creosote concentrations were at, or close to, the nominal concentration. For comparative purposes, we have provided the time‐weighted average total PAH concentration for the 21‐d study in Table 1.…”

“…The most plausible explanation for the parabolic relationship in phytoplankton population abundance is a reduction in grazing pressure on phytoplankton populations caused by a significant decline in zooplankton. In a concurrent assessment by Sibley et al [12], zooplankton populations declined rapidly after application of creosote, with maximum impact (50–100% reduction) occurring between 2 and 7 d after treatment, depending on concentration. Strong effects on zooplankton were still evident up to 21 d after treatment [12].…”

“…In a concurrent assessment by Sibley et al [12], zooplankton populations declined rapidly after application of creosote, with maximum impact (50–100% reduction) occurring between 2 and 7 d after treatment, depending on concentration. Strong effects on zooplankton were still evident up to 21 d after treatment [12]. Thus, at low concentrations, proliferation of phytoplankton relative to the controls was diminished because zooplankton, although reduced in abundance, were present at densities capable of exerting some grazing pressure.…”