Journal
MARINE CHEMISTRY
Volume 109, Issue 3-4, Pages 355-376Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.marchem.2007.08.009
Keywords
submarine groundwater discharge; coastal zone; nutrients; tracers; radium isotopes; Hawai'i
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Multiple tracers of groundwater input (salinity, Si, Ra-223, Ra-224, and Ra-226) were used together to determine the magnitude, character (meteoric versus seawater), and nutrient contribution associated with submarine groundwater discharge across the leeward shores of the Hawai'ian Islands Maui, Moloka'i, and Hawai'i. Tracer abundances were elevated in the unconfined coastal aquifer and the nearshore zone, decreasing to low levels offshore, indicative of groundwater discharge (near-fresh, brackish, or saline) at all locations. At several sites, we detected evidence of fresh and saline SGD occurring simultaneously. Conservative estimates of SGD fluxes ranged widely, from 0.02-0.65 m(3) m(-2) d(-1) at the various sites. Groundwater nutrient fluxes of 0.04-40 mmol N m(-2) d(-1) and 0.01-1.6 mmol P m(-2) d(-1) represent a major source of new nutrients to coastal ecosystems along these coasts. Nutrient additions were typically greatest at locations with a substantial meteoric component in groundwater, but the recirculation of seawater through the aquifer may provide a means of transferring terrestrially-derived nutrients to the coastal zone at several sites. (c) 2007 Elsevier B.V. All rights reserved.
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