Watershed Level Examination of Urea Fate and Transport and the Production of the Biotoxin Domoic Acid.

KEYWORDS: Urea, animal manures, surface runoff, domoic acid, Chesapeake Bay

ABSTRACT

The Chesapeake Bay, the largest estuary in the world, is an important source of many fish and shellfish.  The safety of these species as a food source is currently at risk due to nutrient pollution. Urea, a form of organic nitrogen found in manure and fertilizer, is increasing in usage within the Bay watershed and gaining recognition as an important contributor to eutrophication of the Bay and its tributaries. Over the past decade, harmful algae and periodic harmful algal blooms have become an escalating problem for estuarine waters worldwide with negative impacts on fisheries, shellfish and human health. As climate change begins to affect continental shelf and estuarine zones, the problem is anticipated to become more serious, affecting areas previously thought to be relatively safe. While red tides due to the blooms of Alexandrium sp. and Karenia sp. producing saxitoxin (paralytic shellfish poisoning) and brevetoxin (neurotoxic shellfish poisoning), respectively are the most well known, another algae, the diatom Pseudo-nitzschia producing domoic acid (amnesic shellfish poisoning) is becoming of great concern in estuarine waters such as the Chesapeake Bay and other coastal estuaries. Moreover, recent studies suggest the domoic acid producing diatom Pseudo-nitzschia prefer urea as a nutrient source over other forms of nitrogen (i.e. nitrate and ammonium). This project attempts to identify linkages between terrestrial sources of urea and estuarine production of domoic acid. Components of this study include: (1) examining land use patterns in relation to urea concentrations in surface waters; (2) monitoring agricultural activities in relation to urea concentrations in surface waters; (3) characterizing the fate and transport of urea in surface runoff, drainage ditches and streams; and (4) quantifying the distribution and abundance of diatom species and the production of domoic acid in relation to urea concentration and other water quality parameters. The project will be conducted in the Manokin River watershed which drains directly to the Chesapeake Bay. Field studies will be conducted at the University of Maryland Eastern Shore’s research farm in Princess Anne, MD. Results from this project will provide a comprehensive understanding of urea behavior at both the field and watershed scales and urea’s impact on the Chesapeake Bay ecosystem.