Nematodes as bioindicators of polluted sediments using metabarcoding and microscopic taxonomy

Area of Science:

• Environmental Science
• Ecology
• Molecular Biology

Background:

• Bioindicator species and ecological indices are crucial for assessing environmental health.
• Nematodes are abundant and diverse metazoa, making them valuable bioindicators.
• The NemaSPEAR[%] index, traditionally based on morphology, assesses pollution sensitivity.

Purpose of the Study:

• To evaluate a molecular-based NemaSPEAR[%] index using DNA metabarcoding.
• To test the efficacy of 28S rDNA, 18S rDNA, and COI gene fragments for this index.
• To compare molecular results with morphology-based assessments for polluted sediments.

Main Methods:

• Nematode community DNA metabarcoding using 28S rDNA, 18S rDNA, and COI genes.
• Calculation of NemaSPEAR[%] index from molecular data.
• Comparison of molecularly derived genus-level and species-level data with morphology-based data.

Main Results:

• Genus-level NemaSPEAR[%] from molecular data strongly correlated with morphology-based data (R²=0.86 for 28S rDNA, R²=0.74 for 18S rDNA).
• Molecular methods detected 68% of dominant genera identified by morphology.
• Species-level concordance was lower, attributed to reference database limitations.

Conclusions:

• A genus-level, molecularly-based NemaSPEAR[%] index is a viable tool for evaluating polluted sediments.
• Further validation and database refinement are needed for broader application.
• Molecular approaches offer potential for more efficient ecological monitoring of benthic environments.