Effects of chronic exposure to coal‐derived oil on freshwater ecosystems: II. Experimental ponds

Abstract

Ten 15‐m3 outdoor ponds were treated daily for 8 weeks with a synthetic coal‐derived crude oil; ecological effects were monitored for an additional 52 weeks. The experimental design included two replicate ponds at each of five oil input rates (from 1 to 16 ml/m3/d) plus two untreated controls. A gradient of responses was observed across the gradient of treatment levels. Cladoceran zooplankton populations and ecosystem metabolism (production/respiration) were affected at the lowest input rate, but the effects disappeared before the end of the oiling period and this exposure level (approximately 3% of the 48‐h LC50 for Daphnia magna) was considered safe for this ecosystem. At the next higher treatment level, effects on zooplankton and ecosystem metabolism were greater and persisted until the oiling ended; reproduction of mosquitofish (Gambusia affmis) was also impaired. Major changes occurred throughout the ecosystem at higher treatment levels. The two highest treatment levels completely disrupted the pond community: The ponds recovered from the next‐to‐highest treatment but the effects of the highest treatment persisted for more than a year. Indirect effects occurred at all treatment levels and included changes in water quality, replacement of sensitive taxa by more tolerant competitors and changes in abundance of some species because of increases or decreases in their predators. The results of this experiment were qualitatively and quantitatively similar to those of a parallel experiment in pond‐derived microcosms, and thus substantiated the ability of the microcosms to simulate larger, more natural ecosystems.

Development of mosquitofish (Gambusia affinis holbrooki) populations in lentic mesocosms. Perspectives for ecotoxicological studies

“…Accordingly, studies on mosquitofish should not preclude studies on other indicating species. In 15-m 3 outdoor mesocosms stocked with 35 immature and 4 adult mosquitofish, GIDDINGS et al (1984) were able to monitor the impact of chronic exposure to coal-derived oil on fish populations as well as on physico-chemical parameters, bacteria, primary producers, zooplankton, and insects for one year. In contrast, some studies pointed out a strong influence of mosquitofish on ecosystems structure and functioning.…”

“…The number of ecotoxicological studies in reconstituted ecosystems (mesocosms), especially lentic, have been increasing during the last decade but a few of them have included fish for investigation at the population level (GIDDINGS et al, 1984 ;JOHNSON, 1976 ;KENNEDY et al, 1994 ;MULVEY et al, 1995). More recently, a particular attention has been devoted to design mesocosms of limited size in order to reduce the cost of the experiments, especially in a regulatory prospect, and to reduce the amount of chemicals to be handled.…”

A comparison of periphyton community structural and functional responses to heavy metals

“…Changes in community structure, e.g., changes in the kinds of species and their relative abundances and distributions, have been shown to be sensitive to pollutants (La Point et al, 1983;Sheehan & Winner, 1984;Giddings et al, 1984). Structural measures are relatively inexpensive to monitor, given the available expertise in benthic taxonomy.…”

Improving mesocosm data analysis through individual-based modelling of control population dynamics: a case study with mosquitofish (Gambusia holbrooki)

“…The mosquitofish population dynamics could be monitored in a mesocosm within a few months (Drèze et al 1998). Accordingly, mosquitofish have been used for evaluating genetic and demographic responses of fish to pollutants in outdoor lentic mesocosms (Giddings et al 1984;Tatara et al 2002).…”