Influence of urbanization-driven water quality on reef substrate composition along Suva, Fiji, one of the Pacific Islands most urbanized reefs

Jasha Dehm; Amanda K. Ford; Awnesh Singh; Monal Lal

doi:10.3389/fmars.2025.1659324

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Influence of urbanization-driven water quality on reef substrate composition along Suva, Fiji, one of the Pacific Islands most urbanized reefs

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Influence of urbanization-driven water quality on reef substrate composition along Suva, Fiji, one of the Pacific Islands most urbanized reefs

Jasha Dehm, Amanda K. Ford, Awnesh Singh and Monal Lal

Frontiers in Marine Science, Vol.12, pp.1-14

2025

DOI: https://doi.org/10.3389/fmars.2025.1659324

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Abstract

anthropogenic reefs

Pacific Island Countries and Territories

phase shifts

reef resilience

reef substrate

urban coral reefs

Anthropogenic stressors, including those associated with water quality influence reef benthic communities. This study assesses how changes in water quality influence the benthic composition of an urban reef system in Fiji, by first characterizing reef substrate composition in Suva, assessing substrate composition change across a water quality gradient, and identifying key water quality parameters associated with shifts in benthic composition. Results reveal an urban reef stabilized at coral coverage of ca. 30%, below Fiji’s typical range (45%), but consistent with prior levels (22–33%) from 2006-2007. Predictive modelling identifies temperature as the most consistent predictor of benthic composition (appearing in 77.5% of top models), highlighting its role in structuring communities through physiological and nutrient-cycling effects. Turbidity and nutrients further drive substrate patterns, with turbidity likely promoting sediment accumulation, and elevated nutrients influencing phase shifts towards alternative regimes. Our results demonstrate how urbanization filters benthic communities, creating distinct configurations with varying resilience. Notably, sites with moderate anthropogenic stress levels are characterized by the coexistence of scleractinian coral, seagrass, and soft coral, differing from typical coral-to-algae dominance shifts. While Suva’s reefs currently persist in a degraded-but-stable state, sustained pressures risk further decline. We emphasize targeted strategies (e.g., reef crest protection, watershed management) and long-term monitoring to inform adaptive management. These insights are critical for Fiji and other Pacific Island nations facing similar urban reef stressors, offering a framework for balancing conservation with development.

Details

Title: Influence of urbanization-driven water quality on reef substrate composition along Suva, Fiji, one of the Pacific Islands most urbanized reefs
Authors: Jasha Dehm (Corresponding Author) - University of the South Pacific
Amanda K. Ford - University of the South Pacific
Awnesh Singh - University of the South Pacific
Monal Lal - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
Publication details: Frontiers in Marine Science, Vol.12, pp.1-14
Publisher: Frontiers Research Foundation
Date published: 2025
DOI: 10.3389/fmars.2025.1659324
ISSN: 2296-7745
Copyright note: © 2025 Dehm, Ford, Singh and Lal. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Data Availability: The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
Grant note: J.D. is supported by the "Allocations de recherche pour une thèse au Sud (ARTS-IRD)" fellowship, under the guidance of Christophe Menkes, and receives additional funding through a research student grant from the School of Agriculture, Geography, Environment, Oceans & Natural Sciences at the University of the South Pacific (F3354 FST15-71502-001). Financial support towards the publication fee was received from the Pacific Ocean Climate Crisis Assessment (POCCA) project and the Centre for Sustainable Futures (CSF), funded by the New Zealand Ministry of Foreign Affairs and Trade (MFAT).
Organisation Unit: Australian Centre for Pacific Islands Research; School of Science, Technology and Engineering
Language: English
Record Identifier: 991162455102621
Output Type: Journal article

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