Stieglitz, T.C., Clark, J., and Hancock, G. (2011) Rapid seawater circulation through animal burrows in mangrove forests: a significant source of saline groundwater to the tropical coastal ocean. In: Goldschmidt Conference Abstracts. p. 1944. From: Goldschmidt 2011 Earth, Life and Fire, 14-19 August 2011, Prague, Czech Republic.

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Abstract

A common approach for quantifying rates of submarine groundwater discharge (SGD) to the coastal ocean is to use geochemical tracers such as 222Rn and short lived radium isotopes, which are naturally enriched in groundwater relative to seawater and have well understood chemistries within the marine environment. They occur in both fresh (continental) and saline (marine) groundwaters and thus the water source is often ambiguous. Here, we present a detailed investigation into the tidal circulation of seawater through animal burrows using 222Rn and isotopes of radium in the Coral Creek mangrove forest, Hinchinbrook Island, Queensland, Australia. The study was conducted at the end of the dry season in a creek with no freshwater inputs. Significant export of radionuclides and salt from the forest into the creek indicates continuous tidally driven circulation through the burrows. Results demonstrate that the forest sediment is efficiently flushed, with a water flux of about 30 L/m2/ day of forest floor, which is equivalent to flushing about 10% of the total burrow volume per tidal cycle. Importantly, annual average circulation flux through mangrove forest floors are of the same order as annual river discharge in the central GBR. However, unlike the river discharge, the tidal circulation should be relatively stable throughout the year. This work documents the importance of animal burrows in maintaining productive sediments in these systems, and illustrates the physical process that supports large exports of organic and inorganic matter from mangrove forests to the coastal zone. It also illustrates the importance of considering saline groundwater sources when interpreting SGD radionuclide tracers in the coastal ocean.

Item ID:	21458
Item Type:	Conference Item (Abstract / Summary)
Related URLs:	Organisation
Additional Information:	This paper was also presented at 21st Biennial Conference of the Coastal and Estuarine Research Federation, 6 - 10 November 2011, Daytona Beach, Florida, USA.
Date Deposited:	02 Apr 2012 06:26
FoR Codes:	05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050102 Ecosystem Function @ 50% 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 50%
SEO Codes:	96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments @ 50% 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 50%
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