The ocean provides a fluid environment with complex patterns of flow and dispersal for the organisms that live within it. How these flows transport organisms is relevant for biodiversity with potentially important implications for ecosystem health and climate. An international team of scientists with participation of researchers from IFISC (UIB-CSIC), has published a study in Nature Communications in which they report on a new metric they have developed that can be used to characterize the dispersive nature of fluid flows, including ocean circulations, important for these diversity patterns.
The method relies on the betweenness centrality, a concept that emerges from network theory, which has been used to identify and highlight bottlenecks in systems from air-transportation networks to the human brain. This has been demonstrated to be a very effective measure with which to identify nodes that act as foci for congestion, or bottlenecks, in the network. However, until now there hasn’t been a way to define betweenness outside the network framework.
In their new study, the researchers link dynamical systems and network theory concepts, and extend the concept of betweenness centrality applying it to the complex fluid patterns of oceanic circulations. High betweenness indicates a region where flows converge and diverge again, the above mentioned bottlenecks but now in the ocean flow. Such oceanic confluences are very relevant since they facilitate heightened mingling and dispersal of marine microbial populations.
Using modeled and observational velocity fields from the Adriatic Sea and Antarctic Circumpolar Current, two regions exhibiting very different circulation regimes, the team showed that such bottlenecks are both present and surprisingly persistent across different spatio-temporal scales illustrating the role of these areas in driving fluid transport over vast oceanic regions.
The researchers anticipate that this new metric will be a useful tool in mapping and interpreting global-scale patterns of biodiversity in the ocean, suggesting promise for ecological applications.
Ser-Giacomi, E.; Baudena, A.; Rossi, V.; Follows, M.; Clayton, S.; Vasile, R.; Lopez, C.; Hernandez-Garcia, E. Nature Communications 12, 4935 (1-14) (2021). DOI: 10.1038/s41467-021-25155-9