'Protected' seagrass meadows aren't necessarily healthy, because pollution doesn't stop at the shoreline

I spent last summer wading through seagrass meadows across Northern Ireland, from the sheltered waters of Strangford Lough to the exposed coast at Waterfoot Bay. I was collecting seagrass leaves and testing them for nitrogen pollution. Every meadow I visited sits inside a marine protected area—a stretch of sea that's been given legal protection to safeguard the wildlife living there. And every single one was polluted beyond the limit for healthy seagrass.