Groundwater and Porewater as Major Sources of Alkalinity to a Fringing Coral Reef Lagoon (Muri Lagoon, Cook Islands)

Authors

Tyler Cyronak, Southern Cross University - Lismore, AustraliaFollow
Isaac R. Santos, Southern Cross University - Lismore, Australia
Dirk V. Erler, Southern Cross University - Lismore, Australia
Bradley D. Eyre, Southern Cross University - Lismore, Australia

ORCID

0000-0003-3556-7616

Document Type

Article

Publication Title

Biogeosciences

ISSN

1726-4170

Publication Date

4-15-2013

Abstract

To better predict how ocean acidification will affect coral reefs, it is important to understand how biogeochemical cycles on reefs alter carbonate chemistry over various temporal and spatial scales. This study quantifies the contribution of shallow porewater exchange (as quantified from advective chamber incubations) and fresh groundwater discharge (as traced by ²²²Rn) to total alkalinity (TA) dynamics on a fringing coral reef lagoon along the southern Pacific island of Rarotonga over a tidal and diel cycle. Benthic alkalinity fluxes were affected by the advective circulation of water through permeable sediments, with net daily flux rates of carbonate alkalinity ranging from −1.55 to 7.76 mmol m⁻² d⁻¹, depending on the advection rate. Submarine groundwater discharge (SGD) was a source of TA to the lagoon, with the highest flux rates measured at low tide, and an average daily TA flux of 1080 mmol m⁻² d⁻¹ at the sampling site. Both sources of TA were important on a reef-wide basis, although SGD acted solely as a delivery mechanism of TA to the lagoon, while porewater advection was either a sink or source of TA dependent on the time of day. This study describes overlooked sources of TA to coral reef ecosystems that can potentially alter water column carbonate chemistry. We suggest that porewater and groundwater fluxes of TA should be taken into account in ocean acidification models in order to properly address changing carbonate chemistry within coral reef ecosystems.

DOI

10.5194/bg-10-2467-2013

Volume

10

Issue

4

First Page

2467

Last Page

2480

Comments

©Author(s) 2013. CC Attribution 3.0 License.

Additional Comments

ARC grant #s: LP100200732, DP110103638

NSUWorks Citation

Tyler Cyronak, Isaac R. Santos, Dirk V. Erler, and Bradley D. Eyre. 2013. Groundwater and Porewater as Major Sources of Alkalinity to a Fringing Coral Reef Lagoon (Muri Lagoon, Cook Islands) .Biogeosciences , (4) : 2467 -2480. https://nsuworks.nova.edu/occ_facarticles/1034.