TexHABS

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Texas Harmful Algal Blooms

Detection of the red-tide dinoflagellate Gymnodinium breve

(note: Gymnodinium breve has been renamed Karenia brevis)

James L. Pinckney & Erla B. Ornolfsdottir

Department of Oceanography

Texas A& M University

(Present Address: Marine Science Program and Department of Biological Sciences

University of South Carolina)

Phytoplankton, including Gymnodinium breve and other HAB species, have distinct spectral absorbance characteristics due to accessory photosynthetic pigments located within chloroplasts. Photopigments, including chlorophylls, carotenoids, and phycobilins serve as useful, sensitive, and diagnostic indicators of dominant microalgal functional groups (e.g., diatoms, chlorophytes, dinoflagellates, cyanobacteria, cryptophytes, pelagophytes, etc.). The technology for detection and spectral (absorbance, fluorescence) characterization of photopigments has rapidly evolved and diversified, to the extent that methodologies based on specific pigment detection capabilities can now be routinely employed to identify and estimate phytoplankton standing stock, community structure, and biodiversity. Among the relevant technologies, high performance liquid chromatography (HPLC) is now used worldwide by researchers and water quality agencies to quantify the species composition and relative biomass of taxonomic groups in the phytoplankton community.

The carotenoid gyroxanthin-diester is an uncommon accessory photopigment that provides a relatively unique biomarker for Gymnodinium breve. Gyroxanthin-diester concentrations have been positively-correlated with G. breve standing crop (both cell numbers and total chlorophyll a) during blooms in Florida in 1994-95. Subsequent work with cultures incubated under a range of light and nutrient conditions has shown that gyroxanthin-diester concentrations are consistent, generally comprising 3 - 10% of the total carotenoid pigment pool in G. breve. In addition, the chromatographic and absorption characteristics of gyroxanthin-diester are distinct, providing for easy and definitive recognition in HPLC-derived pigment chromatograms (Fig. 1). The limits of detection for G. breve abundance using this pigment-based approach may be as low as 1.0 x 10⁶ cells.

Another dinoflagellate species that occurs in Texas coastal waters, Gymnodinium mikimotoi, has accessory photopigments similar to G. breve as well as the marker pigment gyroxanthin. In contrast, Gymnodium dorsum has a quite different photopigment profile (Fig. 2). G. dorsum has the primary carotenoid peridinin, but lacks gyroxanthin and 19' hexanoyloxyfucoxanthin. Special thanks to Dr. Dave Millie and Dr. Pat Tester for providing cultures of G. breve and to Mr. Matt Wargo for cultures of G. mikimotoi and G. dorsum. Funding for this project was provided by Texas Parks and Wildlife Department.

Materials and Methods

Reference List

HPLC Chromatograms and Spectra (G. breve only)

HPLC Chromatograms for Gymnodinium species

Molecular Structure of Brevetoxin (neurotoxin from G. breve)

Dinoflagellate Bloom in Galveston Bay (September 2000)

Composite Photographs (pdf file) Location Map (pdf file)

Report for TexHABs Workshop - 4 January 01 (Austin, TX)

Presentation at Am. Soc. Limnol. Oceanogr. - 13 Feb 01 (Albuquerque, NM)

Texas Harmful Algal Blooms

Composite Photographs (pdf file) Location Map (pdf file)