Sewage-derived nitrogen polluting Caribbean ecosystems

WASHINGTON, D.C.: 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.

Kiho Kim, one of the study’s authors and chair of environmental science at American University, 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,” said Kim. “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.”

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 per cent 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.

The transition presents a unique opportunity for Kim to observe and document the impact of increased sewage-derived nitrogen on the health of the coral reefs in real time. He has already collected some baseline data in Guam, thanks to a small grant from the National Oceanic and Atmospheric Administration.

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