MEPS 526:67-87 (2015)  -  DOI:

Toxigenicity and biogeography of the diatom Pseudo-nitzschia across distinct environmental regimes in the South Atlantic Ocean

M. L. Guannel1,6, D. Haring1, M. J. Twiner2,3, Z. Wang2, A. E. Noble4,7, P. A. Lee5, M. A. Saito4, G. Rocap1,*

1Center for Environmental Genomics, School of Oceanography, University of Washington, Seattle, Washington 98195, USA
2Marine Biotoxins Program, Center for Coastal Environmental Health and Biomolecular Research, NOAA/National Ocean Service/National Centers for Coastal Ocean Science, Charleston, South Carolina 29412, USA
3Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128, USA
4Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, 360 Woods Hole Road, Woods Hole, Massachusetts 02543, USA
5Hollings Marine Lab, College of Charleston, 331 Fort Johnson Rd., Charleston, South Carolina 29412, USA
6Present address: Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawai’i, 1000 Pope Road, Honolulu, Hawaii 96822, USA
7Present address: Gradient, 20 University Road, Cambridge, Massachusetts 02138, USA
*Corresponding author:

ABSTRACT: The community composition and toxigenicity of the diatom Pseudo-nitzschia in the northern Benguela Upwelling Zone and the open South Atlantic Ocean were characterized as part of a transoceanic survey conducted during the austral spring of 2007. Multiple morphological types of Pseudo-nitzschia were detected by light microscopy in coastal waters. Automated ribosomal intergenic spacer analysis (ARISA), a DNA-fingerprinting technique used to assess Pseudo-nitzschia community composition, detected 37 ARISA types distributed among 17 stations in both coastal and open-ocean regions. Through statistical analysis of abiotic factors, we identified 6 distinct environmental regimes across which Pseudo-nitzschia community composition varied. Pseudo-nitzschia were detected in open-ocean waters, where community composition differed between surface and deep chlorophyll maxima. The toxin produced by Pseudo-nitzschia, domoic acid (DA), was present in coastal waters both inside and outside the northern Benguela Upwelling Zone at potentially ecologically harmful levels, up to 184 ng DA l-1 and 4.6 pg DA cell-1. Partial internal transcribed spacer 1 (ITS1) clone libraries putatively identified at least 10 species in the South Atlantic, including P. inflatula, P. subpacifica, P. heimii, and P. galaxiae. Previously, these species were reported to produce DA at levels several orders of magnitude lower than our field measurements. Simple correlations were not able to identify obvious environmental triggers of DA production. Our findings suggest that species commonly believed to be weakly toxigenic could pose harm to humans and marine organisms, including those inhabiting southwestern African coastal regions.

KEY WORDS:  Pseudo-nitzschia · Domoic acid · Benguela Upwelling Zone · Harmful algal blooms

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Cite this article as: Guannel ML, Haring D, Twiner MJ, Wang Z and others (2015) Toxigenicity and biogeography of the diatom Pseudo-nitzschia across distinct environmental regimes in the South Atlantic Ocean. Mar Ecol Prog Ser 526:67-87.

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