Sources of land-derived runoff to a coral reef-fringed embayment identified using geochemical tracers in nearshore sediment traps
Takesue, Renee K.
Bothner, Michael H.
Reynolds, Richard L.
MetadataShow full item record
Geochemical tracers, including Ba, Co, Th, 7Be, 137Cs and 210Pb, and magnetic properties were used to characterize terrestrial runoff collected in nearshore time-series sediment traps in Hanalei Bay, Kauai, during flood and dry conditions in summer 2006, and to fingerprint possible runoff sources in the lower watershed. In combination, the tracers indicate that runoff during a flood in August could have come from cultivated taro fields bordering the lower reach of the river. Land-based runoff associated with summer floods may have a greater impact on coral reef communities in Hanalei Bay than in winter because sediment persists for several months. During dry periods, sediment carried by the Hanalei River appears to have been mobilized primarily by undercutting of low 7Be, low 137Cs riverbanks composed of soil weathered from tholeiitic basalt with low Ba and Co concentrations. Following a moderate rainfall event in September, high 7Be sediment carried by the Hanalei River was probably mobilized by overland flow in the upper watershed. Ba-desorption in low-salinity coastal water limited its use to a qualitative runoff tracer in nearshore sediment. 210Pb had limited usefulness as a terrestrial tracer in the nearshore due to a large dissolved oceanic source and scavenging onto resuspended bottom sediment. 210Pb-scavenging does, however, illustrate the role resuspension could play in the accumulation of particle-reactive contaminants in nearshore sediment. Co and 137Cs were not affected by desorption or geochemical scavenging and showed the greatest potential as quantitative sediment provenance indicators in material collected in nearshore sediment traps.
This paper is not subject to U.S. copyright. The definitive version was published in Estuarine, Coastal and Shelf Science 85 (2009): 459-471, doi:10.1016/j.ecss.2009.09.014.
Suggested CitationEstuarine, Coastal and Shelf Science 85 (2009): 459-471
Showing items related by title, author, creator and subject.
Quantity, composition, and source of sediment collected in sediment traps along the fringing coral reef off Molokai, Hawaii Bothner, Michael H.; Reynolds, Richard L.; Casso, Michael A.; Storlazzi, Curt D.; Field, Michael E. (Elsevier B.V., 2006-03-20)Sediment traps were used to evaluate the frequency, cause, and relative intensity of sediment mobility/resuspension along the fringing coral reef off southern Molokai (February 2000–May 2002). Two storms with high rainfall, ...
Wave- and tidally-driven flow and sediment flux across a fringing coral reef : southern Molokai, Hawaii Storlazzi, Curt D.; Ogston, Andrea S.; Bothner, Michael H.; Field, Michael E.; Presto, M. K. (Elsevier B.V., 2004-07-08)The fringing coral reef off the south coast of Molokai, Hawaii is currently being studied as part of a US Geological Survey (USGS) multi-disciplinary project that focuses on geologic and oceanographic processes that affect ...
Munoz, Araceli; Cristobo, J.; Rios, P.; Druet, M.; Polonio, V.; Uchupi, Elazar; Acosta, Juan; Iglesias, S.; Portela, J.; del Rio, J. L.; Parra, S.; Sacau, M.; Vilela, R.; Patrocinio, T.; Almon, B.; Elvira, E.; Jimenez, P.; Fontan, A.; Alcala, C.; Lopez, V. (2012-05)The north flowing Falkland / Malvinas Current has generated sediment drifts at a depth of 1200-1600 m in the Patagonian middle continental slope out of early Holocene hemipelagics, late Pleistocene ice rafted clastics, and ...