Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean

In siliciclastic systems, submarine groundwater discharge (SGD) provides a fraction of freshwater and nutrients delivered to coastal waters, but in many carbonate karst terrains SGD represents the predominant source of terrestrial water and solutes. Water compositions may be modified by reactions in subterranean estuaries, altering chemical fluxes via SGD. In carbonate settings, feedbacks between organic carbon remineralization and calcium carbonate mineral (CaCO3) dissolution and precipitation may alter carbon dioxide (CO2) and phosphorus (P) concentrations and fluxes associated with SGD. To assess these effects, we sampled water from multiple submarine springs along the east coast of the Yucatan peninsula, as well as inland cenotes, and a coastal groundwater well. We measured ammonium (NH4), phosphate (PO4), major element, dissolved inorganic and organic carbon concentrations (DIC and DOC), fluorescent characteristics of colored dissolved organic matter (CDOM) and modeled calcite saturation indices (SIcal) and the partial pressure of dissolved CO2 (PCO2). These data indicate that reactions along a hypothetical flow path to the coast control the composition of terrestrial fresh water entering the subterranean estuary. Non-conservative mixing between brackish groundwater and lagoon water reflect changes to groundwater compositions within the subterranean estuary from CO2 produced during organic matter remineralization and CaCO3 dissolution. Although both organic matter remineralization and carbonate dissolution should liberate P, molar N:P ratios in spring discharge are higher than the Redfield Ratio of 16:1, suggesting sequestration of remineralized P through sorption to carbonate minerals within the STE. This result indicates that SGD, the primary source of water and nutrient to this coastal zone, results in P limitation in coastal water and is a source of CO2 despite buffering by CaCO3 dissolution. This result also emphasizes the importance of biogeochemical reactions within subterranean estuaries for estimates of SGD solute delivery to the oceans and impacts to the coastal carbon cycle.

Pain A. J., Martin J. B., Young C. R., Valle-Levinson A. & Mariño-Tapia I., in press. Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean. Geochimica et Cosmochimica Acta. Article (subscription required).

0 Responses to “Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean”



  1. Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.




Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,326,673 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book