“I’m not just looking at how the fish may be eating a lot more, but also how their excretion is then recycled. Are they no longer hanging out in the seagrass beds, so now the seagrasses don’t have a source of nutrients?” Wied said. “It’s about picking at different pieces of that overall question of how community structure dictates the quality and quantity of nutrients.”

Fish waste — excreted through the gills, in addition to the most obvious source — has a lot of beneficial and life-sustaining nutrients, including nitrogen and phosphorous. If fish numbers dwindle and the steady supply of urine slows, these ecosystems suffer.