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Measuring nutrient pollution in pristine waters: Puerto Rico’s Vieques Island

Vieques Island. Photo by: USFWS.
Vieques Island. Photo by: USFWS.

Life in the ocean require nutrient, but too much of a good thing can be hugely detrimental. Nutrient pollution from agricultural and industrial runoff causes serious ecological harm in the world’s marine waters, at times producing massive “dead zones” where much of the dissolved oxygen has been stripped making it difficult for most marine animals to live there. A new study by scientists with the U.S. National Oceanic and Atmospheric Administration (NOAA) attempts to establish a baseline of nutrient levels in the largely pristine waters around the island of Vieques off of Puerto Rico. Used by the U.S. Navy until 2003, when a series of protests prompted their withdrawal, the island is now a National Wildlife Refuge and is expected to see a new influx of tourism.

“There is no significant agricultural activity and no industrial sources of nitrogen or phosphorous on the island,” the scientists write in their study published in’s open access journal Tropical Conversation Science. “Populations of free roaming horses and wild dogs may be adding to the nutrient budget, and human waste, from the wastewater treatment plant, septic systems and possibly untreated waste, is almost certainly an important source,”

Taking 193 samples over 40 sites for nutrients—including nitrogen, phosphorous and silica—the scientists found that the waters around Vieques have similar nutrient concentrations as nearby Puerto Rico, and currently do not pose a major problem. The researchers did find, however, significantly higher levels of nutrients in lagoons around Vieques but they theorize that this is naturally occurring, likely due to lagoon depth and connectivity to the wider ocean.

“The lagoon ecosystems of Vieques are of great ecological significance, ranging from bird, fish and crab habitats to the unique dinoflagellate populations of the bioluminescent bay,” the researchers note.

The researchers view their work as establishing an important baseline as Vieques Island shifts from a military base to a tourism economy.

“Following the departure of the Navy in 2003, the economy of Vieques has slowly shifted towards tourism. With this shift, significant development is occurring and is expected to continue,” they write. “This development may lead to increased nutrient loads from increased human waste (as both permanent and tourist populations increase) and increased fertilizer inputs (from heavily landscaped areas such as golf courses, hotel grounds and lawns).”

CITATION: Whitall, D., Mason, A. and Pait, A. 2012. Nutrient Dynamics in Coastal Lagoons and Marine Waters of Vieques, Puerto Rico. Tropical Conservation Science Vol. 5(4):495-509.

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