In situ bioassays with Chironomus riparius: Laboratory-field comparisons of sediment toxicity and effects during wintering

Abstract

A field bioassay was developed to study the in situ effects of sediment contamination on Chironomus riparius larvae. The survival, development rate and increase in Chironomus larvae biomass was compared between laboratory bioassays with the field cages. The incidence of mentum deformities was compared not only between laboratory and field bioassays but also with observations on field populations of Chironomus larvae. Survival in the field bioassays was slightly higher than the laboratory, except at locations with known contamination of the surface water. The influence of surface water quality in field bioassays was demonstrated in translocation experiments, in which clean sediment was placed in a polluted site, and vice versa. In a field bioassay carried out in the autumn, an inverse relationship between the rate of development and the initial larval density in the field cages was apparent. In addition, in the field bioassays with C. riparius considerable seasonal variation in the survival and incidence of mentum deformities was found. Field bioassays performed during the winter season indicate that low temperatures can interact with or add to the effects of sediment contamination on chironomid populations.

In situ‐based effects measures: Considerations for improving methods and approaches

“…Handling and density of test organisms —General handling, transfer, and transport of test organisms and the number of test organisms per cage or experimental unit (density) are important considerations (Chappie and Burton 1997, 2000). Clearly, the density of test organisms within a chamber should not be so great that it affects the endpoints measured (Ringwood and Keppler 2002; Den Besten et al 2003; Bervoets et al 2004). Food and habitat (space) limitation, as well as intraspecies predation (cannibalism), can create further problems.…”

A meta‐analysis comparing the toxicity of sediments in the laboratory and in situ

“…The treatment of sediments in the laboratory can alter toxicity and may explain differences between laboratory and in situ responses. For example, homogenizing sediments can increase their toxicity by changing the acid‐volatile sulfide content and redox potential of the sediment and increasing the bioavailability of toxicants [25,26]. Consequently, we might expect homogenized sediments used in laboratory tests to be more toxic than undisturbed sediments used in situ, but this was not apparent from the results of the present study.…”

“…Not surprisingly, differences between field and laboratory toxicity decreased with increasing sediment toxicity. Similarly, Den Besten et al [26] noted that the mortality of Chironomus riparius in field bioassays was greater than in the laboratory at locations with known surface‐water contamination, but otherwise, laboratory toxicity was greater. However, Kater et al [22] showed that laboratory toxicity was not significantly different when overlying water was continually renewed (flow‐through), or never renewed, during a study, leading them to conclude that overlying water did not contribute to differences in laboratory and in situ toxicities.…”

A Meta-Analysis Evaluating the Relationship between Aquatic Contaminants and Chironomid Larval Deformities in Laboratory Studies

“…These are issues requiring further research, potentially outside the context of ecotoxicology. There is currently a bias toward chemical analyses, with inbreeding depression and temperature to our knowledge being the only nonchemical factors considered in the laboratory. There may be value in investigating other stressors at sublethal levels, for example, disease, starvation, and density effects.…”