Assessing patterns of metazoans in the global ocean using environmental DNA

Area of Science:

• Marine Biology
• Ecology
• Genomics

Background:

• Marine ecosystems face unprecedented changes, necessitating documentation of large-scale animal patterns and their drivers for conservation.
• Environmental DNA (eDNA) analysis offers a powerful tool to study marine biodiversity, especially in challenging environments like the deep ocean.

Purpose of the Study:

• To assess metazoan diversity and distribution patterns using eDNA from two global ocean expeditions.
• To identify environmental drivers influencing marine metazoan taxonomic richness and abundance.

Main Methods:

• Utilized existing datasets from the Tara Oceans and Malaspina expeditions, sampling seawater down to 4000 m.
• Employed metabarcoding and metagenome sequencing of eDNA to analyze metazoan taxonomic richness and infer phyla abundance.
• Correlated biodiversity patterns with environmental variables such as sea surface temperature and primary productivity.

Main Results:

• Arthropods exhibited the highest taxonomic richness at the ocean surface, while cnidarians dominated pelagic zones.
• Arthropods comprised half of the marine metazoan eDNA from metagenome datasets, followed by cnidarians and nematodes.
• Mean sea surface temperature and primary productivity were positively correlated with metazoan taxonomic richness at the surface, with weaker correlations in the deep ocean.

Conclusions:

• Environmental DNA sequencing significantly enhances the understanding of marine animal distributions, particularly in the under-sampled deep ocean.
• Temperature and primary productivity are key drivers of surface marine biodiversity, but their influence diminishes in deeper waters.