Fresh meteoric versus recirculated saline groundwater nutrient inputs into a subtropical estuary

Sadat-Noori, Mahmood, Santos, Isaac R., Tait, Douglas R., and Maher, Damien T. (2016) Fresh meteoric versus recirculated saline groundwater nutrient inputs into a subtropical estuary. Science of the Total Environment, 566-567. pp. 1440-1453.

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DOI: 10.1016/j.scitotenv.2016.06.008

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Abstract

The role of groundwater in transporting nutrients to coastal aquatic systems has recently received considerable attention. However, the relative importance of fresh versus saline groundwater-derived nutrient inputs to estuaries and how these groundwater pathways may alter surface water N:P ratios remains poorly constrained. We performed detailed time series measurements of nutrients in a tidal estuary (Hat Head, NSW, Australia) and used radium to quantify the contribution of fresh and saline groundwater to total surface water estuarine exports under contrasting hydrological conditions (wet and dry season). Tidally integrated nutrient fluxes showed that the estuary was a source of nutrients to the coastal waters. Dissolved inorganic nitrogen (DIN) export was 7-fold higher than the average global areal flux rate for rivers likely due to the small catchment size, surrounding wetlands and high groundwater inputs. Fresh groundwater discharge was dominant in the wet season accounting for up to 45% of total dissolved nitrogen (TDN) and 48% of total dissolved phosphorus (TDP) estuarine exports. In the dry season, fresh and saline groundwater accounted for 21 and 33% of TDN export, respectively. The combined fresh and saline groundwater fluxes of NO3, PO4, NH4, DON, DOP, TDN and TDP were estimated to account for 66, 58, 55, 31, 21, 53 and 47% of surface water exports, respectively. Groundwater-derived nitrogen inputs to the estuary were responsible for a change in the surface water N:P ratio from typical N-limiting conditions to P-limiting as predicted by previous studies. This shows the importance of both fresh and saline groundwater as a source of nutrients for coastal productivity and nutrient budgets of coastal waters.


Item ID:	78871
Item Type:	Article (Research - C1)
ISSN:	1879-1026
Keywords:	Groundwater–surface water interaction, Phosphorus, Radium isotopes, Submarine groundwater discharge, Subterranean estuary
Copyright Information:	© 2016 Elsevier B.V. All rights reserved.
Funders:	Australian Research Council (ARC)
Projects and Grants:	ARC DE140101733, ARC DE150100581, ARC DP120101645, ARC LE120100156)
Date Deposited:	12 Jun 2023 23:33
FoR Codes:	40 ENGINEERING > 4005 Civil engineering > 400513 Water resources engineering @ 20% 37 EARTH SCIENCES > 3707 Hydrology > 370703 Groundwater hydrology @ 50% 37 EARTH SCIENCES > 3707 Hydrology > 370704 Surface water hydrology @ 30%
SEO Codes:	18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180201 Assessment and management of coastal and estuarine ecosystems @ 33% 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180305 Ground water quantification, allocation and impact of depletion @ 34% 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180308 Surface water quantification, allocation and impact of depletion @ 33%
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