The EU-funded iCULTURE project announces a scientific article published in “Communications Biology”, revealing how climate conditions from around 20,000 years ago continue to shape the genetic diversity of today’s marine forests. The findings offer new insights into how these ecosystems can be protected and responsibly managed in a changing ocean. 

Titled “Global intraspecific diversity of marine forests of brown macroalgae predicted by past climate conditions”, the study has been authored by several iCULTURE partners from the Centre of Marine Sciences at the University of Algarve, Portugal, and Ghent University, Belgium.

Marine forests, often described as the “rainforests of the sea”, are underwater ecosystems formed by large brown seaweeds, such as kelp. Among the most productive habitats on Earth, they provide food, shelter and nursery grounds for thousands of species, while contributing to carbon storage and coastal protection. Yet these important ecosystems face growing threats from warming seas and human activity.

A key part of their ability to cope with change is genetic diversity: the variation in DNA between individuals and populations of the same species. Not all individuals respond to environmental pressures in the same way. A genetically diverse population is more likely to contain individuals with characteristics that help them survive changing conditions, giving the population a better chance of persisting. Protecting marine forests therefore means safeguarding both the variety of species they contain and the genetic diversity within those species.

Despite its importance, this genetic diversity has been poorly mapped at a global scale. iCULTURE researchers set out to answer a fundamental question: are today’s patterns of seaweed genetic diversity better explained by current environmental conditions or by the climate of the distant past?

Using genetic data from 29 brown seaweed species sampled across hundreds of sites worldwide, together with a machine-learning approach, the team found that environmental conditions during the Last Glacial Maximum, around 20,000 years ago, were more than twice as important as present-day conditions in predicting current genetic diversity. The findings suggest that regions where conditions remained favourable during past ice ages helped seaweed populations persist and preserve their genetic heritage.

Building on this insight, the researchers developed a predictive model that explained approximately 78% of the observed variation in genetic diversity. They then applied it to 280 cold- and temperate-water brown seaweed species, producing the first model-based global atlas of genetic diversity within species for marine forests.

The atlas identifies hotspots in the northeastern Pacific, northeastern Atlantic, Mediterranean Sea, southern Australia, New Zealand and Japan. The study also found a strong positive relationship between genetic diversity and species diversity, suggesting that protecting areas rich in seaweed genetic diversity can also help safeguard broader biodiversity.

These findings provide a practical scientific basis for marine conservation. They can help guide the placement of Marine Protected Areas and inform restoration efforts by identifying genetically diverse populations that may be suitable sources for restoring damaged marine forests. For the seaweed sector, the maps can also inform responsible sourcing and cultivation decisions, alongside assessments of local conditions and population resilience.

This work directly supports iCULTURE’s ambition to develop a sustainable, zero-waste seaweed value chain while protecting ocean biodiversity. Its combination of artificial intelligence and environmental modelling contributes to the project’s work on predictive tools for seaweed resource management. By improving understanding of where genetic diversity is concentrated and why, the study helps provide the scientific foundation for using seaweed resources responsibly while supporting their long-term survival.

Read the full publication!