Sewage-derived nitrogen polluting Caribbean ecosystems

A study published in the journal Global Change Biology has found that sewage-derived nitrogen is increasingly becoming the top source of such pollution in Caribbean coastal ecosystems.

And one of the study’s authors and chair of environmental science at American University, Kiho Kim, is undertaking an analysis of the problem.

Fertilizer had been the dominant source of nitrogen pollution in Caribbean coastal ecosystems for the past 50 years, but the study found that even though that is on the decline – thanks in part to the introduction of more advanced, environmentally responsible agricultural practices during the last decade, the existing pollution is still a problem.

"We can't simply say our coastal ecosystem is being polluted by nitrogen," Kim said. "The consequences may be the same, but differentiating the source of the pollutants is critical

to crafting sustainable solutions-you can't fix a problem if you don't know what's causing it,” Kim said.

Through a chemical analysis of 300 coral samples from the Smithsonian Institution's National Museum of Natural History's Invertebrate Zoology Collection, Kim and some American University graduate students reconstructed a record of nitrogen inputs into the Caribbean over the last 150 years. Agricultural and sewage pollution create different

signatures in organisms like coral.

"We determined that poor storm water management and wastewater treatment were really to blame over the last decade for nitrogen pollution in the Caribbean," said Kim. "Our next step is to document this process in action."

To do this, the researcher will focus on coral samples from the coastal areas of Guam, a small Pacific island that, during the next four years, will experience a population increase of 20 percent as the U.S. military relocates Marines from Okinawa, Japan to that island.

Guam already has poor waste water infrastructure, and the influx of military personnel will further strain the island's resources. For Kim, the transition presents a unique opportunity to observe and document, in real time, the impact of increased sewage-derived nitrogen on the health of the coral reefs. He has already collected some baseline data in Guam, thanks to a small grant from the National Oceanic and Atmospheric Administration.