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Coral Ba/Ca records of sediment input to the fringing reef of the southshore of Moloka’i, Hawai’i over the last several decades |
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| Authors: | Nancy G Prouty Michael E Field Stacy D Jupiter Malcolm McCulloch |
| Institution: | a 400 Natural Bridges Drive, Pacific Science Center, U.S. Geological Survey, Santa Cruz, CA 95060, USA b 345 Middlefield Road, U.S. Geological Survey, Menlo Park, CA 94025, USA c Research School of Earth Sciences, Australian National University, Canberra 02000, Australia d Wildlife Conservation Society, South Pacific Country Program 11 Ma’afu Street Suva, Fiji e School of Earth and Environment, The University of Western Australia, Crawley, Western Australia 6009, Australia |
| Abstract: | The fringing reef of southern Moloka’i is perceived to be in decline because of land-based pollution. In the absence of historical records of sediment pollution, ratios of coral Ba/Ca were used to test the hypothesis that sedimentation has increased over time. Baseline Ba/Ca ratios co-vary with the abundance of red, terrigenous sediment visible in recent imagery. The highest values at One Ali’i are near one of the muddiest parts of the reef. This co-varies with the lowest growth rate of all the sites, perhaps because the upstream Kawela watershed was historically leveed all the way to the nearshore, providing a fast-path for sediment delivery. Sites adjacent to small, steep watersheds have ∼decadal periodicities whereas sites adjacent to mangrove forests have shorter-period fluctuations that correspond to the periodicity of sediment transport in the nearshore, rather than the watershed. All four sites show a statistically significant upward trend in Ba/Ca. |
| Keywords: | Coral reefs Geochemistry Terrestrial sedimentation Landuse change |
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