SPATIOTEMPORAL DYNAMICS OF CARBONATE CHEMISTRY IN RIVER AND GROUNDWATER INPUTS TO THE NORTHEASTERN MEDITERRANEAN COAST

Date

2025-11-12

Author

Ayar, Yeşim

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Freshwater inputs onto coastal regions play a critical role in shaping marine carbonate chemistry, nevertheless their influence remains undefined in many semi-enclosed seas. This study presents the first comprehensive assessment of spatiotemporal carbonate dynamics in both riverine and groundwater discharges along the Northeastern Mediterranean coast, with a particular focus on the Cilician Basin. A total of 301 samples were collected from nine rivers and ten groundwater wells, including a one-year high-frequency monitoring program at METU-IMS coastal wells (5m, 10m, 20m, 50m) and the Lamas River, as well as seasonal spatial surveys in the entire Basin during wet (April) and dry (September) periods. Total alkalinity (TA) and pH were directly measured, while dissolved inorganic carbon (DIC) and pCO₂ were calculated using CO2SYS program. The results revealed consistently higher and more stable TA and DIC values in groundwater, often exceeding 6000 µmol/kg, driven by prolonged water–rock interaction in carbonate-rich rocks. In contrast, rivers exhibited greater seasonal variability and lower carbonate concentrations, especially during the wet season due to dilution. Statistically significant seasonal increases in TA were observed in river systems during the dry season (p = 0.007), while groundwater pH showed a significant seasonal decline (p = 0.023). Meteorological variables further influenced carbonate variability: wind speed showed a significant correlation on riverine TA (β = –246.01, p = 0.029), and precipitation effects were delayed by up to 9 weeks in both systems. Annual TA and DIC fluxes from rivers were quantified for the first time in this region, with the Ceyhan and Asi Rivers contributing disproportionately larger amounts to the coastal carbonate budget (>24 Gmol/year each). While riverine carbon inputs accounted for only ~0.04% of the total coastal inventory, their localized and seasonal impacts may be considerable, especially under restricted exchange or stratification. This thesis emphasizes the complementary roles of rivers and groundwater in regulating coastal carbonate chemistry and buffering capacity. The findings underscore the importance of integrating both surface and subsurface freshwater sources into regional acidification assessments and marine carbon budgets, particularly in data-scarce regions such as the Eastern Mediterranean basin.

Subject Keywords

Carbonate Chemistry, River Discharge, Groundwater Discharge, Northeast Mediterranean Basin

URI

https://hdl.handle.net/11511/117409

Collections

Graduate School of Marine Sciences, Thesis