Influence of fresh water, nutrients and DOC in two submarine-groundwater-fed estuaries on the west of Ireland

► Adjacent bays along a karst coastline show very different influences of SGD. ► SGD is a source of nitrate and DOC but not DIP to both bays, which may act as phosphate sinks. ► Nitrate supply to Kinvara is dominated by groundwater input, while adjacent Aughinish Bay is dominated by marine inputs. ► Major rainfall events may reduce salinity in Kinvara Bay below guideline limits set in Shellfish Water Quality Regulations. ► Kinvara Bay is vulnerable to eutrophication if phosphate inputs increase.