Researchers use MITgcm to explore how oceanographic connectivity shapes marine biodiversity in the Galápagos

Reporting by Helen Hill for MITgcm

The Galápagos Archipelago is renowned for its extraordinary biodiversity, but it is also one of the most oceanographically complex regions of the world’s oceans. Situated at the crossroads of several major current systems, the islands are influenced by equatorial currents, seasonal upwelling, and energetic mesoscale circulation features that create striking environmental gradients over relatively short distances. While marine scientists have long recognized that these physical processes influence ecosystem structure, quantifying exactly how ocean circulation shapes patterns of biodiversity has remained a significant challenge.

In a recent study, researchers combined environmental DNA (eDNA) observations with advanced ocean modelling to investigate how ocean circulation contributes to differences in marine community composition across the Galápagos. The work asked: Beyond factors such as temperature, habitat, and geographic distance, can the pathways taken by ocean waters themselves help explain why marine communities differ from one location to another?

Answering that question required a detailed representation of the regional ocean circulation. Oceanographic modelling analyses conducted by Alexander Forryan and Alberto C. Naveira-Garabato of the University of Southampton employed MITgcm to simulate the highly dynamic waters surrounding the archipelago. MITgcm was particularly well suited to the challenge because of its ability to resolve complex circulation patterns across a wide range of spatial scales, from island-scale flow features to broader regional currents. In a setting where topography, stratification, and variable current systems interact to create intricate transport pathways, a high-resolution MITgcm configuration enabled the team to represent the physical environment with the fidelity required to investigate ecological connectivity.

The researchers used the model to examine how water parcels move between locations sampled for eDNA. Such analyses are increasingly common in marine ecology because they provide a mechanistic link between physical circulation and the dispersal of organisms, larvae, nutrients, and other biological material. However, the study revealed that conventional particle-tracking approaches alone were not sufficient to explain the observed biodiversity patterns.

To address this limitation, the team developed an innovative metric termed oceanographic resistance. Rather than focusing solely on whether locations are connected by currents, the metric captures how difficult transport is between sites based on the cumulative influence of the circulation field. In effect, it provides a measure of the “friction” imposed by ocean dynamics on ecological exchange.

The results were striking. Oceanographic resistance proved to be a powerful predictor of differences in community composition, performing on a par with well-established drivers such as temperature and geographic separation. The findings suggest that fine-scale circulation patterns are not merely background environmental conditions but are fundamental determinants of how marine communities are organized across the archipelago.

Want to find out more? Email Alberto 

About the Researchers

Alberto C. Naveira-Garabato is a Professor of Physical Oceanography in the School of Ocean and Earth Science at the University of Southampton and the National Oceanography Centre, Southampton. His research focuses on ocean circulation, mixing processes, polar oceans, and the ocean’s role in climate. He has led and contributed to numerous international observational and modelling programmes investigating the dynamics of the global ocean and their implications for climate and marine ecosystems. He began using MITgcm in around 2007.

Alexander Forryan is a physical oceanographer at the University of Southampton and the National Oceanography Centre whose research explores ocean circulation, air-sea interaction, and the physical processes that shape marine ecosystems. His work frequently combines observations and high-resolution numerical modelling, including MITgcm, to investigate regional ocean dynamics such as the upwelling systems and circulation patterns of the Galápagos Archipelago.

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