Jake Allgeier studies fish urine. I guess someone has to. He says that there's a lot more of it than you would think, and it's a lot more important for marine environments than people realize. From redandblack.com
"A funny comparison is if you take the biggest ungulate herd — so that would be bison, antelope, deer and elk — in Yellow Stone National Park, per meter squared — so per unit area — the fish on one of the reefs that I look at...they actually pee more than three times more [than that herd]," he said. Fish urine even dwarfs fertilizer-heavy golf course runoff — per meter squared — in nutrient content.