A tropical sediment toxicity test using the dipteran Chironomus crassiforceps to test metal bio availability with sediment pH change in tropical acid-sulfate sediments

Peck, Mika R, Klessa, David A and Baird, Donad J (2002) A tropical sediment toxicity test using the dipteran Chironomus crassiforceps to test metal bio availability with sediment pH change in tropical acid-sulfate sediments. Environmental Toxicology and Chemistry, 21 (4). pp. 720-728. ISSN 0730-7268

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Abstract

The wetlands of the Magela floodplain of northern Australia, which is the major sink for dissolved metals transported in the Magela Creek system, contain acid-sulfate sediments. The rewetting of oxidized acid-sulfate soil each wet season produces acidic pulses that have the potential to alter the bioavailability of sediment-associated metal contaminants. Acute toxicity tests (72-h mean lethal concentration [LC50]) using the tropical chironomid Chironomus crassiforceps Kieffer showed that copper toxicity decreased from 0.64 mg/L at pH 6 to 2.30 mg/L at pH 4. Uranium toxicity showed a similar trend (36 mg/L at pH 6 and 58 mg/L at pH 4). Sediment toxicity tests developed using C. crassiforceps also showed that both metals were less toxic at the lower sediment pH with pore-water copper toxicity having a lowest-observed-effect concentration of 4.73 mg/L at pH 4 compared to 1.72 mg/L at pH 6. However, a lower pH increased pore-water metal concentrations and overlying water concentrations in bioassays. Hydrogen ion competition on metal receptor sites in C. crassiforceps was proposed to explain the decrease in toxicity in response to increased H+ activity. This study highlights the need to consider site-specific physicochemical conditions before applying generic risk assessment methods.

Item Type: Article
Additional Information: First to show that natural fluctuations in sediment acidity have ecotoxicological implications to both sediment fauna and overlying aquatic fauna and calls for a major revision of risk assessments in tropical environments. Project design by MP during PhD, field and lab work by MP. Supervised by DB and DK
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Depositing User: Mika Peck
Date Deposited: 06 Feb 2012 20:25
Last Modified: 14 Jun 2012 11:48
URI: http://sro.sussex.ac.uk/id/eprint/25823
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