CAMBRIDGE, MD (March 1, 2006) –   A recent review paper published in the scientific journal Biogeochemistry, has found that worldwide increases in the use of urea, a manufactured form of nitrogen, as an agricultural fertilizer is an emerging source of pollution that may be associated with increasing harmful algal blooms in coastal waters.

While the use of nitrogen as a fertilizer began increasing in the 1960’s and 1970’s, the past decade has seen a major shift to use of urea-based products.  Urea now constitutes more than 50% of global nitrogen fertilizer.  Use of urea in the US has also grown, but not as fast as other parts of the world.  Urea is manufactured mainly in Russia, Canada, and Middle Eastern countries.  The US also produces urea in facilities that are mainly along the Gulf of Mexico.

Mixed bloom of Dinophysis acuta and D. norvegica co-occurring
with a bloom of Ceratium furca

Nitrogen is a key nutrient required by all plants and algae and can come in many usable forms.  Algae growth in coastal waters are generally limited by available nitrogen, while the form of nitrogen can have a large effect on the type of algae that grows.  Organic forms of nitrogen, such as urea, have been found to be a particularly important source of nutrients that stimulate the growth of harmful algae blooms.   

Urea had been considered a minor form of nitrogen found in coastal waters.  However, research over the last few years suggests that it can be found in relatively higher concentrations than expected.  But more importantly, it also appears to be a preferred source of nitrogen by algae, especially the species that cause harmful algal blooms.  In fact, in many of the world’s coastal waters more than 50% of all the nitrogen taken up by algae is from urea.

Harmful algal blooms, sometimes referred to as “red tides,” cause fish or shellfish kills either directly through their toxins or by depleting the water of oxygen thus suffocating the animals. Harmful algal blooms can also cause other damage to the ecosystem.  The toxins they produce can also cause human illnesses such as paralytic shellfish poisoning because these toxins can move up the food chain.  Eutrophication, or the nutrient pollution of coastal and ocean waters, is considered to be one of the factors contributing to the global expansion of harmful algal blooms. Harmful algal blooms are now commonly seen in New England, along the mid-Altantic including the Chesapeake Bay, on Florida’s coast, and along the west coast.

Lead author Dr. Pat Glibert of the University of Maryland Center for Environmental Science said, “As urea use is increasing we are seeing more large blooms of algae that can produce toxins.  These toxic blooms are occurring more often in more regions throughout the world’s coastal areas.  There has been a recent escalation in the numbers of these blooms throughout much of the world, but especially throughout Southeast Asia where fertilizer use has been rapidly increasingly.  Not surprisingly, we also find that urea is predominantly used as a nitrogen source for their expanding agricultural production.” 
 Glibert continued, “While we have traditionally thought that urea applied to land did not reach coastal waters, we are finding more and more evidence of enriched concentrations of urea around the world.”

Co-author Cindy Heil commented, “Florida has a history of annually recurring red tides that predate Florida's settlement.  Although we know that multiple nitrogen sources are required to support Florida red tides, urea may be one potential nutrient source for blooms which may be controllable.”

With increasing human populations as well as the even greater production of food, it is projected that the production of urea and its use as a fertilizer will continue to increase.  Since some of the nutrients applied to the land eventually find their way into coastal waters, it is important to minimize the amount of fertilizers and use agricultural best management practices to minimize their movement to coastal waters whenever possible.

From the wetlands of the Chesapeake Bay to the open waters of the world’s oceans, the UMCES Horn Point Laboratory has a national reputation for its groundbreaking research in estuarine, ecosystem, aquaculture and restoration studies.  Founded in 1973 and located on the banks of the Choptank River, the Horn Point Laboratory is one of three laboratories of the University of Maryland Center for Environmental Science.

CONTACT:
Dave Nemazie
410.228.9250 ext. 615
nemazie@ca.umces.edu