Spatiotemporal patterns of genetic diversity in the world’s coral reefs

Signing the 2022 Global Biodiversity Framework (GBF), most countries on Earth committed to protect the genetic diversity of wild species and safeguard their adaptive potential. Since effective protection requires efficient monitoring, there is an urgent need for tools that can establish a geographic baseline of genetic diversity and track its changes over time. This monitoring task is particularly challenging in ocean ecosystems, where field-based DNA sampling is logistically complex. Coral reefs exemplify this challenge: they are the most biodiverse ecosystems in our oceans and are undergoing rapid decline due to global change, yet the status and trends of their genetic diversity remain largely unknown.

We compiled genome-wide DNA data for 2,520 individuals from 18 reef taxa—including corals, fish, sharks, oysters, shrimp, anemones, and manta rays––and  assessed spatiotemporal patterns of genetic diversity across 173 reefs worldwide between 1998-2018. While we did not observe an overall temporal decline in genetic diversity, within-reef diversity showed negative trends, potentially reflecting population-level loss. In addition, we identified regions in the Indian Ocean and the Caribbean where genetic diversity appeared systematically lower than the global average.

We finally used hundreds of seascape variables to interpret these geographic patterns of genetic diversity across reefs globally. Key predictors included declining oxygen levels, increasing nitrate concentrations, and rising water temperatures—variables that can be tracked in real time via Earth Observation (EO), enabling early warning for coral reef genetic diversity loss.

Integrating DNA and EO data can provide detailed information on the status of genetic diversity in our oceans, and future work should focus on how to integrate these data within the GBF.