A comparative approach using ecotoxicological methods from single-species bioassays to model ecosystems

Area of Science:

• Ecotoxicology
• Environmental Science
• Marine Biology

Background:

• Soft sediments are critical habitats susceptible to chemical contamination.
• Nematodes, as key meiobenthic fauna, are valuable indicators for sediment ecotoxicological assessments.
• Understanding zinc's impact on natural nematode assemblages is crucial for ecosystem health evaluation.

Purpose of the Study:

• To investigate the direct and indirect effects of zinc on freshwater nematode assemblages in sediment microcosms.
• To compare the sensitivity of natural nematode communities with standardized tests using Caenorhabditis elegans.
• To evaluate the predictive power of microcosm and acute community toxicity tests for field conditions.

Main Methods:

• Conducting acute community toxicity tests to assess direct zinc toxicity.
• Utilizing sediment microcosms to examine both direct and indirect effects of zinc.
• Comparing responses of natural nematode assemblages with standardized tests on Caenorhabditis elegans (ISO 10872).

Main Results:

• Caenorhabditis elegans exhibited median susceptibility (LC50 = 20 mg Zn/L) among 15 tested nematode species in acute tests.
• Zinc affected nematodes in microcosms dose-dependently, altering species composition at 13–19 mg Zn/kg sediment dry weight.
• Microcosm results showed better correlation with field observations compared to acute community toxicity tests.

Conclusions:

• Microcosm studies provide more ecologically relevant data on zinc toxicity to nematode communities than acute tests.
• Natural nematode assemblages in microcosms are sensitive indicators of sediment contamination.
• Standardized tests with C. elegans can serve as a reference but may not fully represent field-relevant sensitivities.