Beyond Ireland’s rolling green hills and storied countryside, the nation’s marine territory spans more than 10 times its landmass. Its rocky, rugged coast borders a frigid, slate-hued ocean where kelp forests, seagrass meadows and cold-water coral reefs dwell beneath the water’s surface, providing habitat for an array of sea life. Confronted by diverse pressures, these marine ecosystems are under threat. Microplastics, industrial pollution, destructive fishing practices and rising water...