Nutrient and Fecal Indicator Bacteria Inputs from Submarine Groundwater Discharge on the North Shore of Kauai

Submarine groundwater discharge (SGD) is a potentially important source of freshwater, nutrients, and pollution to the coastal ocean, yet it has not been well quantified for most locations. This poster investigates the impacts of SGD in Hanalei Bay, Ha'ena, and Princeville, three locations on the north shore of Kaua'i, Hawai'i, during two sampling trips conducted in March 2005 and August 2006. The short-lived isotopes of radium, 223Ra and 224Ra, were used to calculate the flux of groundwater into the coastal ocean in these areas. Nutrient concentrations and levels of total coliform bacteria, E. coli, and Enterococcus were measured in groundwater, the nearshore ocean, rivers, and streams. Fluxes of nutrients and bacteria associated with groundwater discharge were estimated. The results indicate that nutrient subsidies to the nearshore ocean from SGD may be comparable to those from rivers and streams, and that FIB subsidies may also be significant in some areas. More sampling is necessary to assess seasonal variability, which may be significant.