Pacific Coastal & Marine Science Center
USGS Pacific Coral Reefs Website
Plots of numerical model results showing how predicted future sea-level rise will likely reduce sediment residence time (how long it stays in place, top) and increase sediment flux (how much sediment moves how quickly, bottom) on the fringing coral reef flat off south-central Molokaʻi.
There is a growing body of evidence indicating that the rate of sea-level rise has increased relative to the past century and will continue to increase in the 21st century; that evidence has recently been summarized by the Intergovernmental Panel on Climate Change (IPCC). If all aspects of reef morphology—colony size and shape, cross-reef relief, surface rugosity, and so on—keep pace with the rising sea levels, then it is likely that changes in depth-controlled physical processes will be minimal to non-detectible. However, based on rates of vertical reef accretion in Hawaiʻi and throughout the Pacific (which are an order of magnitude smaller than predicted rates of sea-level rise), it is unlikely that reefs there and other locations will keep pace, and their inability to do so will lead to subtle but important changes in selected physical processes on some coral reefs.
Photograph of the shallow fringing coral reef flat and adjacent land at Kaulana, Kahoʻolawe.
In addition, recent studies indicate the flux of submarine groundwater discharge from land to coral reefs in Hawaiʻi and other high islands is substantial, and often significantly colder and enriched in terrestrial-derived nutrients than surrounding seawater. Ecosystem functions of submarine groundwater discharge to coral reef ecosystems are not quantified but can be hypothesized to (1) buffer thermal stress (bleaching) in corals experiencing warming, and (2) supply nutrients to otherwise oligotrophic coastal waters. While an excess of the latter has been observed to cause complete phase shifts in the form of wholesale loss of coral and replacement by macroalgae, the role of the former has not been tested. Both may be significantly altered by impending climate change and proposed land use that alter groundwater quantity, quality, flux, composition, and fate, especially in rapidly developing areas. This effort is focused on submarine groundwater discharge, its role in shaping coral reef ecosystem structure, and the ecosystem services it provides.
The overall objective of this research effort is to better understand how climate change may impact coral reefs. Achievement of this objective requires an understanding of the physical parameters driving change in coral reefs and the resulting ecosystem processes. The goals of this effort are to:
The approach to these interdisciplinary studies will rely on a combination of field measurements and physics-based numerical monitoring. We use a wide range of tools to try to answer these questions, including: oceanographic instruments (for example, acoustic Doppler current profilers, wave/tide gauges, temperature sensors, salinity sensors, chemical sensors) mounted on the seabed or on moorings, water-column profilers with similar suites of sensors, coral cores, geophysical water-column and sub-bottom surveys, and physics-based numerical models.
Maps of suspended-sediment concentrations under low tide conditions and high tide conditions off south-central Molokaʻi. Such comparisons over a range of water levels are useful to provide insight on how processes on reefs may respond to predicted future sea-level rise. [larger version]
Field, M.E, Ogston, A.S., and Storlazzi, C.D., 2011, Rising sea level may cause decline of fringing coral reefs: Eos Transactions AGU, v. 92, no. 33, p. 273-280, doi:10.1029/2011EO330001.
Prouty, N.G., Roark, E.B., Buster, N., and Ross, S., 2011, Growth rate and age distribution of deep-sea black corals in the Gulf of Mexico: Marine Ecology Progress Series, v. 423, p. 101-115, doi:10.3354/meps08953.
Storlazzi, C.D., Elias, E., Field, M.E, and Presto, M.K., 2011, Numerical modeling of the impact of sea-level rise on fringing coral reef hydrodynamics and sediment transport: Coral Reefs, v. 30, Supplement 1, p. 83-96, doi:10.1007/s00338-011-0723-9.
Knee, K.L., Street, J.H., Grossman, E.E., Boehm, A.B., and Paytan, A., 2010, Nutrient inputs to the coastal ocean from submarine groundwater discharge in a groundwater-dominated system; relation to land use (Kona coast, Hawaii, U.S.A.): Limnology and Oceanography, v. 55, no. 3, p. 1105-1122, doi:10.4319/lo.2010.55.3.1105.
Ogston, A.S., and Field, M.E., 2010, Predictions of turbidity due to enhanced sediment resuspension resulting from sea-level rise on a fringing coral reef; evidence from Molokai, Hawaii: Journal of Coastal Research, v. 26, i. 6, p. 1027-1037, doi:10.2112/JCOASTRES-D-09-00064.1.
Piniak, G.A., and Brown, E.K., 2009, Temporal variability in chlorophyll fluorescence of back-reef corals in Ofu, American Samoa: Biological Bulletin, v. 216, p. 55-67, http://www.biolbull.org/content/216/1/55.full.
Prouty, N.G., Field, M.E., Jupiter, S.D., and McCulloch, M.T., 2009, Coral proxy record for decadal scale reduction in base flow from Moloka'i, Hawaii: Geochemistry, Geophysics, Geosystems, v. 10, Q12018, doi:10.1029/2009GC002714.
Street, J.H., Knee, K.L., Grossman, E.E., and Paytan, A., 2008, Submarine groundwater discharge and nutrient addition to the coastal zone and coral reefs of leeward Hawaiʻi: Marine Chemistry, v. 109, p. 355-376, doi:10.1016/j.marchem.2007.08.009.
Yates, K. K. and Halley, R. B.: CO32− concentration and pCO2 thresholds for calcification and dissolution on the Molokai reef flat, Hawaii, Biogeosciences, 3, 357-369, doi:10.5194/bg-3-357-2006.
Jokiel, P.L., 2004, Temperature stress and coral bleaching. In Rosenberg, E., and Loya, Y., eds., Coral Health and Disease, Springer-Verlag, Heidelberg, p. 401-425.
Jokiel, P.L., and Brown, E.K., 2004, Global warming, regional trends and inshore environmental conditions influence coral bleaching in Hawaii: Global Change Biology, v. 10, no. 10, p. 1627-1641, doi:10.1111/j.1365-2486.2004.00836.x.
Grossman, E.E., Logan, J.B., Presto, M.K., and Storlazzi, C.D., 2010, Submarine groundwater discharge and fate along the coast of Kaloko-Honokohau National Historical Park, Island of Hawaiʻi; Part III, spatial and temporal patterns in nearshore waters and coastal groundwater plumes, December 2003-April 2006: U.S. Geological Survey Scientific Investigations Report 2010-5081, 76 p.
U.S. Geological Survey, 2009, Science-based strategies for sustaining coral ecosystems: U.S. Geological Survey Fact Sheet 2009-3089, 4 p.
Field, M.E., Cochran, S.A., Logan, J.B., and Storlazzi, C.D., eds., 2008, The coral reef of south Molokaʻi, Hawaiʻi; Portrait of a sediment-threatened reef, U.S. Geological Survey Scientific Investigations Report, 2007-5101, 180 p.
Grossman, E.E., 2008, Sea-level and its affects on reefs in Hawaiʻi, in Field, M.E., Cochran, S.A., Logan, J.B., and Storlazzi, C.D., eds., The coral reef of south Molokaʻi, Hawaiʻi; Portrait of a sediment-threatened fringing reef, U.S. Geological Survey Scientific Investigations Report, 2007-5101, p. 101-104.
Grossman, E.E., Logan, J.B., Street, J., Paytan, A., and Chavez, P.S., 2008, Ground water and its influence on reef evolution, in Field, M.E., Cochran, S.A., Logan, J.B., and Storlazzi, C.D., eds., The coral reef of south Molokaʻi, Hawaiʻi; Portrait of a sediment-threatened fringing reef, U.S. Geological Survey Scientific Investigations Report, 2007-5101, p. 111-116.
Knee, K., Street, J., Grossman, E.E., and Paytan, A., 2008, Submarine ground water discharge and fate along the coast of Kaloko-Honokohau National Historical Park, Hawaiʻi; Part II, Spatial and temporal variations in salinity, radium-isotope activity, and nutrient concentrations in coastal waters, December 2003-April 2006: U.S. Geological Survey Scientific Investigations Report 2008-5128, 31 p.
Field, M.E., Berg, C.J., and Cochran, S.A., 2007, Science and management in the Hanalei watershed; a trans-disciplinary approach: U.S. Geological Survey Open-File Report 2007-1219, 87 p.
Presto, M.K., Storlazzi, C.D., Logan, J.B., and Grossman, E.E., 2007, Submarine groundwater discharge and fate along the coast of Kaloko-Honokōhau National Historical Park, Hawaiʻi; Part I, time-series measurements of currents, waves and water properties; November, 2005-July, 2006: U.S. Geological Survey Open-File Report 2007-1310, 39 p.