An investigation of the effects of submarine groundwater discharge on the coastal carbon and nutrient cycles of a karstic aquifer, Kinvara Bay, Co Galway, Ireland

• Main Author: KELLY, TARA
• Other Authors: Evans, Rachel, IRCSET (OK)
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Trinity College Dublin. School of Natural Sciences. Discipline of Geography 2018
• Subjects: SGD; Submarine Groundwater Discharge; EEMF-PARAFAC; Chromophoric Dissolved Organic Matter (CDOM); Nitrogen metabolism; Carbon metabolism; Kinvara Bay; FT-ICR-MS; DOM; Ocean acidification
• Online Access: http://hdl.handle.net/2262/85302; http://people.tcd.ie/kellyt7

APPROVED Summary Submarine Groundwater Discharge (SGD) is an important pathway of terrestrial nutrients to the coastal ocean. The influence of SGD on the carbon cycle in coastal zones and the relationship between SGD-borne carbon and other macronutrients remains uncertain. I used a combination of in-situ sampling techniques, experiments with defined conditions and modelling to identify, quantify and characterise SGD-derived carbon and nutrients and assess their biogeochemical importance within coastal zones, using Kinvara Bay, Western Ireland as a case study. Firstly, I used the LOICZ water/salt budget models, and radon analysis where possible, to determine the seasonal SGD rates into the bay. Quantitative nutrient (nitrogen, phosphorus and silica) and carbon budgets were then closed in Kinvara Bay for four sampling campaigns (July 2013, January 2015, June 2015 and January 2016). Across all campaigns, of the three allochthonous carbon and nutrient sources (SGD, raw sewage and wet deposition), SGD was the largest source of carbon and oxidised nitrogen but the lowest source of ammonium and phosphorus into Kinvara bay. Dissolved organic nitrogen (DON) fluctuated significantly from season to season but was highest during the wettest campaign (January 2015). A portion of DON is bioavailable and the DON delivered via SGD contributed to productivity within Kinvara Bay. In terms of whole system N metabolism, the bay was net autotrophic during July 2013, June 2015 and January 2016 but net heterotrophic during January 2015 (the wettest campaign). SGD was the major allochthonous contributor of C to Kinvara Bay. Freshwater SGD delivered elevated concentrations of DIC and comparable concentrations of DOC in comparison to seawater. Whole core sediment incubation experiments confirmed sediment acted as a sink of DOC and as a source of DIC to the bay during June 2015. Closure of the nutrient and carbon budgets confirmed higher primary productivity during July 2013, June 2015 and January 2016 regarding N and C metabolism. ...