PATTERNS OF Pseudo-nitzschia AND DOMOIC ACID RELATED TO PHYTOPLANKTON
COMMUNITY STRUCTURE IN THE BENGUELA CURRENT
Diana Haring1, Michele Guannel1, Michael J. Twiner2, Peter A. Lee3, Giacomo R. DiTullio3, Zhihong
Wang2, and Gabrielle Rocap1
1
School of Oceanography, University of Washington, Seattle, WA 98195
2
Marine Biotoxins Program, Center for Coastal Environmental Health and Biomolecular Research,
NOAA/National Ocean Service, Charleston, SC 29412
3
Hollings Marine Lab, College of Charleston, Charleston, SC 29412
Members of the cosmopolitan diatom genus Pseudo-nitzschia produce a toxin called domoic acid (DA),
which is responsible for Amnesic Shellfish Poisoning in humans and negative impacts on marine
ecosystems. Phytoplankton community structure and DA levels were analyzed from samples collected
from the Benguela Current, along the southwestern coast of Africa, in December 2007. Pseudo-nitzschia
cells were measured for identification through the use of light microscopy and assigned to one of three
morphological groups. Other organisms present were defined to the genus level. Phytoplankton
community structure was dominated by either diatoms or dinoflagellates at each of the thirteen stations
sampled. Pseudo-nitzschia was present at seven stations; at most of these stations, all three
morphological groups were represented. Particulate DA was detected at five stations and ranged between
2.7 and 184 ng/L (averaging 3.0 pg/cell). The P. australis/fraudulenta group was the dominant type of
phytoplankton detected at the station with the highest DA level. To help identify Pseudo-nitzschia
species and more fully characterize Pseudo-nitzschia diversity, a genetic fingerprinting technique called
Automated Ribosomal Intergenic Spacer Analysis (ARISA) will be performed. These community
composition data, in conjunction with environmental parameters, could help elucidate Pseudo-nitzschia
species and conditions correlated with DA production in this region.