Aquatic Sciences Meeting, Albuquerque 2001

CS15 Harmful Algal Blooms

Date: Tuesday, February 13, 2001, Time: 4:30:00 PM

Location: Cochiti/Taos

Dyhrman, S, T, Woods Hole Oceanographic Institution, Woods Hole, USA, sdyhrman@whoi.edu

Lomas, M, , University of Maryland Center for Environmental Science, Horn Point Laboratory, Cambridge, USA, lomas@hpl.umces.edu

Anderson, D, M, Woods Hole Oceanographic Institution, Woods Hole, USA, danderson@whoi.edu

A POTENTIAL DIAGNOSTIC FOR NITROGEN STRESS: UREASE ACTIVITY IN A MODEL DINOFLAGELLATE

Nitrogen availability is an important factor controlling phytoplankton abundance and species composition in marine waters. In addition to inorganic nitrogen, some phytoplankton species can use dissolved organic nitrogen (DON) sources such as amino acids and urea for growth. Urea can be a major component of the DON pool in marine waters and may play a critical role in the development of phytoplankton blooms. Urease, the enzyme used to hydrolyze urea into ammonia and carbonic acid, was characterized in laboratory cultures of the toxic dinoflagellate, Alexandrium fundyense. Urease activity appears to be nitrogen regulated. Enzyme activity is detectable in nitrate-stressed and urea grown cells, but activity is depressed in ammonia grown cells, and absent in nutrient-replete and phosphate-stressed cells. The enzyme also appears to have an absolute nickel requirement as cells will not grow on urea without added nickel. Ongoing semicontinuous culture experiments are investigating how urease activity varies with nitrogen-limited growth rate. We are exploring the potential for using urease activity or the presence of the A. fundyense urease enzyme as a diagnostic indicator of nitrogen physiology in field populations.

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Aquatic Sciences Meeting, Albuquerque 2001

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