Decline in the quality of Irish estuaries and coastal waters, particularly in the south and southeast
The EPA says it's due to high nutrient levels

There’s been a further drop in the quality of Ireland’s rivers, lakes, estuaries, and coastal waters with stretches in the South East among the hardest hit.
That’s according to a report from the Environmental Protection Agency, which says just half of the nation’s waters are in a satisfactory condition.
Standards have fallen by 16% in estuaries, 10% in coastal waters, 3% in lakes and 1% in rivers.
EPA Programme Manager, Mary Gurrie describes which part of the country has the worst water quality; “Declines are most significant in our estuaries and coastal waters along the South East and Southern seaboards so we have areas such as Cork Harbour, Wexford Harbour and the Slaney shore and Nore estuaries which have lost their good water quality status”.
She adds “The problem we’re seeing with our estuaries in the South and South East is too much nitrate coming from agriculture and that’s getting into our rivers and our groundwaters and flowing into our estuaries where it is causing damage to the ecology and to the wildlife in those estuaries and we’re losing the biodiversity there”.
See the full report here