Contrasting pollution sensitivity for temperate reef assemblages revealed by microhabitat-resolved eDNA, algal...

Area of Science:

• Marine Ecology
• Environmental DNA (eDNA) Metabarcoding
• Biomonitoring

Background:

• Shallow reef ecosystems host diverse life but face threats from pollution.
• Monitoring these dynamic environments, especially microhabitats, is challenging.
• Environmental DNA (eDNA) is a promising non-invasive tool for biodiversity assessment.

Purpose of the Study:

• To compare the efficacy of eDNA metabarcoding with traditional methods (underwater visual surveys, epifauna sampling) for assessing pollution impacts on reef assemblages.
• To investigate pollutant-associated variations in microbial, microbial eukaryote, and metazoan assemblages within distinct reef microhabitats.
• To evaluate the sensitivity of different biological assemblages and microhabitats to various environmental stressors.

Main Methods:

• Collected eDNA samples (16S rRNA, 18S rRNA, COI Leray) and conducted underwater visual surveys and epifauna sampling across 18 sites.
• Utilized distance-based linear models to analyze pollutant impacts on reef assemblages.
• Assessed microhabitat-specific variations in assemblages in response to pollutants.

Main Results:

• eDNA demonstrated comparable sensitivity to traditional methods, capturing broader pollutant signals and microhabitat variations.
• Epifaunal sampling uniquely identified effects of total nitrogen and dichloroethane.
• Assemblage shifts were significantly associated with Sea Surface Temperature (SST), metals, Total Organic Carbon (TOC), δ15N, and human pressure. Different taxa showed distinct pollutant sensitivities.

Conclusions:

• eDNA is a valuable complement to traditional biomonitoring techniques for assessing reef health and pollution impacts.
• eDNA facilitates high-resolution, microhabitat-specific assessments of marine biodiversity.
• The findings support the integration of eDNA into long-term reef biomonitoring frameworks.