America’s fresh waters are being challenged as increases in nutrient pollution are causing a significant loss of terrestrial-derived carbon from these ecosystems. Nutrient pollution is widespread in the U.S. and globally, due primarily to agricultural fertilization and urban stormwater runoff
America’s fresh waters are being challenged as increases in nutrient pollution are causing a significant loss of terrestrial-derived carbon from these ecosystems. Nutrient pollution is widespread in the U.S. and globally, due primarily to agricultural fertilization and urban stormwater runoff.
This trickle down effect could be reducing the stream’s ability to support aquatic life.
A team of researchers, including FIU biologist John Kominoski, has found organic carbon from forests, including leaves and twigs, is cut in half when low-to-moderate nutrient pollution, such as an excess nitrogen and phosphorus, is added to stream ecosystems.
“Nutrient pollution’s effects often focus on highly visible, global incidents of harmful algal blooms. But little was known about how nutrients affect terrestrial-derived carbon, a major form of carbon in many inland aquatic ecosystems,” Kominoski said. “We found nutrient pollution is reducing terrestrial organic carbon by 50 percent, and this higher magnitude loss of carbon is less visible than smaller increases in algal-based carbon in forested streams.”
Organisms rely on energy from carbon, and nitrogen and phosphorous are natural parts of aquatic ecosystems. The balance of carbon and nutrients in ecosystems determines the food resources for organisms, like invertebrates and fishes. However, even low-to-moderate increases in these nutrients can cause state changes in the source and quantity of carbon available to dependent organisms.
“Many aquatic ecosystems have low light, so they do not accumulate algae-based carbon. This requires these ecosystems to rely on terrestrial carbon for food. However, organic carbon from terrestrial ecosystems is more than food, it helps remove excess nutrients from the water,” Kominoski said. “Leaves and wood are actively colonized by microbes that remove nutrients from the water, as they consume carbon. By accelerating the loss of these carbon resources with nutrients, we reduce the capacity of aquatic ecosystems to remove excess nutrients. This means that more nutrients are