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MEPS
Marine Ecology Progress Series

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MEPS 443:19-27 (2011)  -  DOI: https://doi.org/10.3354/meps09360

Saxitoxin δ15N as a species-specific tracer of the source of nitrogen used by the toxin-producing dinoflagellate Alexandrium tamarense

Christa B. Smith1,2,*, Deana L. Erdner1

1University of Texas, Marine Science Institute, 750 Channel View Drive, Port Aransas, Texas 78373, USA
2Present address: University of Georgia, Marine Sciences Bldg 1030, Athens, Georgia 30602, USA

ABSTRACT: Alexandrium tamarense Balech is a harmful, bloom-forming dinoflagellate which can produce saxitoxins (STXs), a suite of powerful neurotoxins that bioaccumulate up the food chain and can have severe economic and health impacts. Being nitrogen-rich, STX is ideal for studying the relationship between its producer and the nitrogen used for growth. In this study, we measured the δ15N of medium nitrate, algal cells and toxin in batch cultures of A. tamarense. In nitrate-replete conditions, cells were 1.5‰ depleted relative to the source, and STX was 1.5‰ depleted relative to the cells. In nitrogen-limiting cultures the isotopic difference between cells and STX changed as nitrate in the growth medium was depleted, indicating uncoupled toxin synthesis and cell growth under changing external nutrient conditions. Our results show that toxin-specific nitrogen stable isotope analysis may provide a tool that can help to identify the nitrogen sources supporting toxic Alexandrium blooms.


KEY WORDS: Alexandrium tamarense · δ15N · Harmful algal blooms · Isotopic analysis · ­Saxitoxin · Stable nitrogen isotopes


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Cite this article as: Smith CB, Erdner DL (2011) Saxitoxin δ15N as a species-specific tracer of the source of nitrogen used by the toxin-producing dinoflagellate Alexandrium tamarense. Mar Ecol Prog Ser 443:19-27. https://doi.org/10.3354/meps09360

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