A Short-Term Sublethal In Situ Sediment Assay with Chironomus riparius Based on Postexposure Feeding

Abstract

A short-term, sublethal, and cost-effective in situ sediment toxicity assay for routine assessments with the midge Chironomus riparius Meigen, based on postexposure feeding, was developed and evaluated. An inexpensive and easy-to-use assay chamber was designed. A sediment toxicity assay was successfully performed at a lentic system impacted by acid mine drainage, at sites with different types of sediment. It consisted of a 48-h exposure period followed by a 1-h postexposure feeding during which the larvae were fed on Artemia franciscana nauplii. Methodologies for feeding quantification of fourth-instar larvae (10-d old) were first developed and optimized under laboratory conditions. A. franciscana nauplii were shown to be more suited than fish flake food for postexposure feeding quantification, allowing higher precision and cost-effectiveness. It also required a shorter postexposure feeding period, thus minimizing the chances for an eventual organism physiological recovery from toxicant exposure. The influence of several environmental conditions during exposure on postexposure feeding was also evaluated: temperature, dissolved oxygen, pH, salinity, hardness, substrate, humic acids, light, and food availability. Only temperature was found to significantly influence postexposure feeding rates; exposure at 5 degrees C led to reduced feeding activity compared to 30 degrees C. Recovery rates of 87% were obtained after the 48-h field exposure at all sites (except site R2). A statistically significant postexposure feeding depression was observed at the three sites impacted by acid mine drainage. Therefore, the proposed short-term in situ assay is a potentially useful tool to assess sediment sublethal toxicity on a routine basis.

The quality and availability of fine particulate organic matter for collector species in headwater streams

“…The larvae were obtained from at least ten egg masses of laboratory cultures (procedures described in Soares et al [22]). The experiments were conducted at 20 AE 2°C with a light/dark regime of 14:10 h under incandescent light.…”

Endobenthic Invertebrates as Reference Species

“…Biomarkers of oxidative and genotoxic stress and larval growth were used to assess the effects of nanomaterials (Oberholster et al, 2011). However, in situ assays remain limited (e.g., Maycock et al, 2003;Soares et al, 2005). However, in situ assays remain limited (e.g., Maycock et al, 2003;Soares et al, 2005).…”

European bee-eater (Merops apiaster) populations under arsenic and metal stress: evaluation of exposure at a mining site

“…Although the Mina de São Domingos area is highly contaminated with metals (Lopes et al 1999;Pereira et al 2004;Soares et al 2005;Pereira et al 2006a, b), it is partially included in a natural reserve (MARN 1995) and holds a high vertebrate richness with at least 128 species (Ribeiro et al 1995). In spite of the several research projects carried out in the region on the effects of metals on aquatic (Lopes et al 1999(Lopes et al , 2004MoreiraSantos et al 2004) and terrestrial (Soares et al 2005;Pereira et al 2006a, b) biota, only a few focused on wild vertebrates: fish (Castro et al 2004) and mice (Pereira et al 2006a). In the current study, elemental concentrations in feathers and regurgitated pellets were used as indicators of the potential exposure of the European bee-eater to arsenic and metals.…”