New research identifies potential source populations of invasive red alga threatening Hawaii's protected coral reefs
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Colors indicate the proportion of particles located in each pixel throughout the study period, January 1, 2000 to December 30, 2015 using the Connectivity Modeling System. Particles originating at the backward trajectory start point, Manawai (indicated by a gray triangle), generally tracked towards the northwest or southeast until landing in a potential source region. Warmer colors represent regions with a higher concentration of particles, while cooler colors indicate areas with fewer particles during the modeled duration. The high concentration of particles surrounding Manawai reflects the start point of the model run. Currents influencing the dispersal of particles are shown in gray arrows and named. The North Pacific Subtropical Gyre is composed of the Kuroshio Current, North Pacific Current, California Current, and North Equatorial Current, which runs north of the eastward flowing Equatorial Counter Current. The Hawai'i Lee Counter Current (HLCC) and Subtropical Counter Current (STCC) occur within the gyre, moving more weakly from west to east and are represented by thinner arrows. Credit: PeerJ (2025). DOI: 10.7717/peerj.19610
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Colors indicate the proportion of particles located in each pixel throughout the study period, January 1, 2000 to December 30, 2015 using the Connectivity Modeling System. Particles originating at the backward trajectory start point, Manawai (indicated by a gray triangle), generally tracked towards the northwest or southeast until landing in a potential source region. Warmer colors represent regions with a higher concentration of particles, while cooler colors indicate areas with fewer particles during the modeled duration. The high concentration of particles surrounding Manawai reflects the start point of the model run. Currents influencing the dispersal of particles are shown in gray arrows and named. The North Pacific Subtropical Gyre is composed of the Kuroshio Current, North Pacific Current, California Current, and North Equatorial Current, which runs north of the eastward flowing Equatorial Counter Current. The Hawai'i Lee Counter Current (HLCC) and Subtropical Counter Current (STCC) occur within the gyre, moving more weakly from west to east and are represented by thinner arrows. Credit: PeerJ (2025). DOI: 10.7717/peerj.19610
A recent study has established a predictive framework for identifying the source populations of Chondria tumulosa, a cryptogenic red macroalga that has been rapidly overtaking coral reef ecosystems in Hawai'i's Papahānaumokuākea Marine National Monument since its first observation in 2016.
The work is in PeerJ Life & Environment.
The research, titled "A predictive framework for identifying source populations of non-native marine macroalgae: Chondria tumulosa in the Pacific Ocean," addresses one of the most pressing ecological threats facing the protected monument's pristine coral reef systems.
First discovered at Pearl and Hermes Atoll (Manawai) in 2016, C. tumulosa has exhibited alarming invasive characteristics, with satellite imagery revealing a staggering 115-fold increase in area coverage between 2015 and 2021. The alga now forms extensive mats that smother coral reef habitats, expanding at an exponential rate of approximately 44.75 square kilometers per year.
"Understanding the origin of this potentially invasive species is crucial for developing effective management strategies," said the study's lead author. "Our predictive framework combines dispersal modeling with morphological analysis and molecular phylogenetics to help determine which source populations are most likely to have led to the introduction of C. tumulosa."
The research team's approach provides resource managers with essential tools to:
Identify potential source populations of the alga
Track its introduction pathways
Develop targeted prevention strategies
Guide future monitoring efforts
The study comes at a critical time, as surveys have documented C. tumulosa forming thick mats on forereefs and creating dark, meandering accumulations throughout Manawai Atoll's inner lagoon, threatening the ecological integrity of one of the world's most protected marine environments.
More information:
James T. Fumo et al, A predictive framework for identifying source populations of non-native marine macroalgae: Chondria tumulosa in the Pacific Ocean, PeerJ (2025).
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A predictive framework has been developed to identify source populations of the invasive red alga Chondria tumulosa, which has rapidly expanded in Hawai'i's Papahānaumokuākea Marine National Monument since 2016. The alga now covers an estimated 44.75 km2 per year, forming dense mats that threaten coral reefs. This framework integrates dispersal modeling, morphology, and molecular data to inform management and prevention strategies.
This summary was automatically generated using LLM.