Mo’orea eDNA Project / Projet eDNA

Introduction

In February 2025, the Island Sustainability Program cohort sampled eDNA (environmental DNA) from different locations around Mo’orea, French Polynesia. eDNA is DNA collected in aggregate from the environment rather than from an individual organism. It allows for rapid monitoring and measurement of species presence without collecting a living sample. eDNA serves as a proxy for biodiversity, as the eDNA sample can be sequenced to detect the number and types of species that have shed their genetic material in the water. The sample is parsed apart by metagenomics and metabarcoding, in which the sequence is compared against existing DNA libraries. Sampling biodiversity from different sites across Mo’orea allows us to assess how the species composition and richness of ecological communities varies across an island ecosystem. This also allows us to examine how different factors such as salinity, distance from the ocean, pristine versus impacted reef, proximity to population centers, and anthropogenic inputs impact biodiversity.

Project Goals

The primary objective of this project is to analyze the biodiversity of different aquatic locations, from water samples taken from numerous sites across Mo’orea, French Polynesia, through filtering eDNA from each sample. Specifically, we aim to characterize:

• How marine location (taking relative turbidity, water currents, runoff, etc into account) affects the biodiversity of each sampled location

• How certain activities (ie tourism, agriculture, harbour) affect the biodiversity of locations

• Differences in biodiversity along a river profile, especially above versus below a dam wall, and mouth of a river

Methods

Samples were collected over a two-week long period, from the 5th to 20th of February 2025.

We collected 1.00 L of water samples from various locations on and around the island of Moorea including freshwater lakes, and streams. We used WilderLabs eDNA kit to collect and process the samples. All samples were collected following proper safety procedures and all researchers handling the samples wore latex gloves during processing.

1.00 L samples were pumped in increments of 50 ml in a syringe through a 1.2 µm filter. The water was discarded after filtering, and a preservative was injected into the filter containing the collected eDNA. The filter was then reinserted and sealed in the test kit bag which was labeled and sent for processing at Wilder Lab in New Zealand.

See a more detailed protocol here: DOI: dx.doi.org/10.17504/protocols.io.j8nlkdb81g5r/v1

Site Selection

We choose public sites from a wide geographic range of the island with easy water access (either fresh or saltwater) to maximize our understanding of the variety of ecosystems. This wide range allows us to yield different DNA signals, i.e. freshwater stream, coral reef near the crest, coral reef near shore, deep water off a dock, beach near hotel, etc.

Significance & Further Research

eDNA is an emerging tool with positive implications for conservation biology. It is more efficient and less invasive compared to other sampling methods, as there is no need to collect live samples from individual organisms. This novel technology allowed us to collect up-to-date data on biodiversity around Mo’orea, French Polynesia and to infer how anthropogenic impacts may influence it. This recent, localized information on biodiversity can help inform conservation management actions. Further research could include repeat sampling from the same locations to track biodiversity shifts over time, sampling more locations on or beyond Mo’orea, or comparing this data with other biodiversity studies from this island

Community Engagement

Guillaume and Tony, the boat drivers, assisted with eDNA sample collection.

Project Expected Results

• Touristic areas have more biodiversity because of feeding, but areas with high input of boat activity and habitat destruction due to construction will have lower biodiversity

• Areas with high anthropogenic impact, i.e. high amounts of boat activity, and agricultural areas, will have lower biodiversity due to pollution.

• Freshwater areas have different biodiversity than saltwater areas

• Within freshwater areas, sections differ in biodiversity based on stream section (eels, no eels). above vs below dam.

• Runoff areas have less biodiversity

• Towing samples will have different biodiversity than non-towed samples.