Comparative ecotoxicity of suspended sediment in the lower Rhone River using algal fractionation, Microtox® and Daphnia magna bioassays

Abstract

The toxicity associated with suspended sediments from the Rhone River (Switzerland-France) was determined with three acute bioassays. Large volume water samples were centrifuged for recovery of suspended solids in November 1989; one sample was taken as a control upstream from Lake Geneva and the 9 remainder downstream from Geneva to the Mediterranean Sea, with a single sample of the major tributary the Saone at Lyon. Heavy metals (Hg, Cd, Cr, Cu, Ni, Pb, Zn) and organic contaminants (OCs, PCBs, PAHs) bound to sediment were analysed and extracted by elutriation with filtered lake water and by organic solvent ( dichloromethane ). Sediment water elutriates were tested with algal fractionation bioassays (AFB) using Lake Geneva ambient phytoplankton, with Daphnia magna and Microtox® acute toxicity tests, whereas organic extracts were utilized in the latter two bioassays to evaluate the potential sediment toxicity. The bulk analyses of the sediment together with elutriate metal concentrations indicated the highest contamination of sediment downstream of Lyon. Medium contamination appeared for the stations downstream of Geneva, in the Saone River and at the Rhone River mouth. The station upstream of Lyon had low concentrations, comparable to the values in the Upper Rhone. Organic contaminants are mainly observed downstream of Lyon and their concentrations decline onwards to the sea. The bioassays Microtox ® on organic extracts and AFB on the elutriates show a similar toxicity trend, but differ in that Microtox was more sensitive to organics whereas the algal test responded predominantly to metals. This difference is believed to be due to the different extraction procedures used, rather than to the tests themselves. Daphnia magna was the least sensitive and appeared to give a broader band response to the observed contaminants in the sediment. The bioassay results when integrated confirm that the biotoxicity trends relate well to the composition of the sediment, a factor which emphasizes the need for battery testing in ecotoxicological assessment

Ecotoxicological Assessment of Sediment Leachates of Small Watercourses in the Brno City Suburban Area (South Moravia, Czech Republic)

“…Water fleas belong to organisms highly susceptible to most pollutants (Enserink et al 1993) such as pesticides containing organophosphates and carbamates (Barata et al 2007;Svobodova and Faina 1994;Brown et al 2007 by Santiago et al (1993) were in agreement with our results, when Daphnia magna was found to be the least susceptible. High immobilization of daphnia specimens observed in sample L2 from the spring collection was probably due to the presence of suspended substances in the filtered leachate of the sediment forming flocculation during the test, which disabled their movement when sticking onto their antennae.…”

Chronic toxicity of Great Lakes sediments to Daphnia magna: elutriate effects on survival, reproduction and population growth

“…Most studies that have used cladocerans, commonly D. magna, to evaluate sediment toxicity have measured only short-term, acute toxicity to bedded sediments (Malueg et al 1983Stemmer et al 1990a,b), unfiltered elutriates Hall et al 1986;Wiederholm and Dave 1989), filtered elutriates (Santiago et al 1993) or sediment pore water (Giesy et al 1988(Giesy et al , 1990. Efforts have been made to use cladocerans, including D. magna, to evaluate long-term, chronic toxicity of water and sediments (LeBlanc and Surprenant 1985;Knowles et al 1987;Bridgham 1988;Nebeker et al 1988;Chandini 1989;Burton 1991;Enserink et al 1993).…”

Stranded cetaceans as indicators of mercury pollution in the Mediterranean Sea

“…Data published by Pirrone et al (2001) on total anthropogenic mercury emissions in the Mediterranean region show that France is the leading Hg emitter with 21.4%. High discharges of toxic metals from the nearby Rhone estuary were documented by Renzoni et al (1986), Cossa & Martin (1991) and Santiago et al (1993). Moreover Rajar et al (2007) reported the contribution of total mercury (HgT) from different rivers to the Mediterranean Sea and in particular that the Po and Rhone are the most polluted rivers with a HgT delivery to the sea of 30 kmol/year and 16 kmol/year, respectively.…”