Capturing open ocean biodiversity: Comparing environmental DNA metabarcoding to the continuous plankton recorder

Area of Science:

• Marine Ecology
• Biodiversity Monitoring
• Molecular Ecology

Background:

• Open ocean zooplankton biodiversity is crucial for ecosystem health.
• Current monitoring relies on Continuous Plankton Recorder (CPR) surveys using morphological identification.
• Environmental DNA (eDNA) metabarcoding offers a potential alternative for biodiversity assessment.

Purpose of the Study:

• To compare the effectiveness of eDNA metabarcoding with conventional CPR sampling for Southern Ocean zooplankton biodiversity.
• To assess eDNA metabarcoding's ability to capture species-level diversity and community structure compared to bulk DNA metabarcoding and morphological analysis.

Main Methods:

• Collected seawater (2 L) for eDNA metabarcoding and bulk plankton samples (~1,500 L) from CPRs.
• Utilized a metazoan-targeted cytochrome c oxidase I (COI) marker for species identification.
• Compared eDNA metabarcoding results with morphological identification and bulk DNA metabarcoding of CPR samples.

Main Results:

• eDNA metabarcoding detected more zooplankton species (up to 1.6x) than morphological analysis, despite amplifying non-metazoan DNA.
• Bulk DNA metabarcoding of CPR samples yielded higher zooplankton diversity than eDNA metabarcoding.
• eDNA metabarcoding identified key taxa differentiating communities and revealed diurnal patterns in copepod eDNA, suggesting a short temporal signal.

Conclusions:

• eDNA metabarcoding is a viable tool for detecting Southern Ocean zooplankton biodiversity, capturing significant species and community patterns.
• Methodological refinements are needed for eDNA metabarcoding to match the diversity recovery of bulk DNA metabarcoding.
• eDNA metabarcoding shows potential for efficient, large-scale open ocean biodiversity monitoring.