Validity and ecological relevance of an active in situ bioassay using gammarus pulex and limnephilus lunatus

Abstract

In situ bioassays using aquatic organisms serve as a link between laboratory and field studies. However, the ecological relevance of in situ studies had not previously been assessed by direct comparison with field data. In this study, an in situ bioassay employing Gammarus pulex L. (Crustacea: Amphipoda) and Limnephilus lunatus Curtis (Insecta: Trichoptera) was used in two agricultural tributaries and the connecting headstream. Simultaneously, the short-term insecticide contamination and the stream population dynamics of both species were monitored. During transient insecticide inputs (duration: about 1 h; peak concentrations: 6.2 mg/L fenvalerate; 0.6 μg/L parathion-ethyl), mortality of both species in the in situ bioassay was significantly higher in the contaminated tributary than in the uncontaminated control tributary (analysis of variance [ANOVA], Fisher's protected least significant difference [PLSD]; p < 0.05). Limnephilus lunatus gave comparable responses in the stream; however, no mortality of G. pulex was observed in the stream. The reason for this difference is presumably that, in contrast to the bioassay, a typical avoidance behavior of G. pulex to pesticides, downstream drift, is possible in the field. During runoff events, G. pulex migrated from the potentially contaminated headstream section into the uncontaminated tributary, which can be regarded as a refuge and source for recolonization. Significantly lower coefficients of variance in the bioassay (≤0.22 compared to ≥0.55 in the field samples) allow for a better detection of adverse effects of pesticide with this method. Hence, although the bioassay is valuable for identifying insecticide input events, supplementary field studies are necessary for an ecological interpretation of the results.

Using a freshwater amphipod in situ bioassay as a sensitive tool to detect pesticide effects in the field

“…However, technical problems, such as clogging of mesh or vandalism to test chambers, restrict the wide application of in situ testing methods. It has also been shown that animals caged in the field are prevented from using avoidance behavior [3], and as a result, these tests may overestimate actual field toxicity.…”

“…Several attempts were made to link survival of in situ exposed freshwater and estuarine organisms to agricultural pollution [4,5], and some studies were able to detect pesticide effects using in situ testing [6][7][8]. However, a link of responses in situ and reactions of populations in the field has rarely been established [3].…”

Avoidance of polycyclic aromatic hydrocarbon–contaminated sediments by the freshwater invertebrates Gammarus pulex and Asellus aquaticus

“…Benthic invertebrates are highly exposed to contaminated sediments through their habitat choice and feeding habits. Previous research has shown that sediment contamination results in lower densities of amphipods (e.g., [15]). A possible explanation for this observation is that amphipods can actively leave contaminated sites by drifting processes [15].…”

Spray Deposition of Two Insecticides into Surface Waters in a South African Orchard Area

“…In addition to the physical properties of the spray A considerable amount of research has been conitself, crop characteristics such as height, the amount of ducted on the development and optimization of open area between trees, diffuse noninterceptance, and air-assisted orchard sprayers during recent decades leaf area index influence the production and extent of (Hislop, 1991). However, drift from orchard sprayers pesticide that may be subject to drift (USEPA, 1999). remains an important environmental problem.…”