Marin, R, , MBARI, Moss Landing, CA, USA, maro@mbari.org
Doucette, G, , NOAA/NOS, Charleston, SC, USA, greg.doucette@noaa.gov
Powell, C, , NOAA/NOS, Charleston, SC, Canada, christine.powell@noaa.gov
Ryan, J, , MBARI, Moss Landing, CA, USA, ryjo@mbari.org
Kudela, R, , Univ Calif Santa Cruz, Santa Cruz, CA, Canada, kudela@cats.ucsc.edu
Scholin, C, , MBARI, Moss Landing, USA, scholin@mbari.org

A BLOOM OF PSEUDO-NITZSCHIA AUSTRALIS IN MONTEREY BAY, CA, IS ASSOICATED WITH EXTREME VARIATIONS IN LEVELS OF PARTICULATE AND DISSOLVED DOMOIC ACID

Blooms of toxic diatoms of the genus Pseudo-nitzschia along coastal California can cause acute illness and mortality of marine birds and mammals. The causative agent is domoic acid (DA), a neurotoxin. In August 2000 an intense bloom of Pseudo-nitzschia australis, a known DA producer, was observed in a region noted for toxin outbreaks, but impacts on marine wildlife appeared far less severe than seen previously. Amounts of DA per P. australis cell measured in the 2000 bloom exhibited extreme variability on scales of kilometers horizontally and meters vertically, with a maximum range of ~100 fold. Nutrients (nitrate, silicic acid, phosphate) known to affect Psuedo-nitzschia species’ toxin production in culture also appear to influence expression of DA in nature. Like pure cultures, analysis of natural bloom waters suggest that production of DA and its release into the surrounding medium may be modulated by multiple factors, all of which alter the amount and nature and of toxin available for entry into the food web. These observations reveal a complex and highly dynamic relationship between toxin producing cells and prevailing environmental conditions.