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Marine Ecology Progress Series

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MEPS 483:31-45 (2013)  -  DOI:

Trichodesmium-derived dissolved organic matter is a source of nitrogen capable of supporting the growth of toxic red tide Karenia brevis 

Rachel E. Sipler1,2,*, Deborah A. Bronk2, Sybil P. Seitzinger 1,3, Ronald J. Lauck1, Lora R. McGuinness1, Gary J. Kirkpatrick4, Cynthia A. Heil5, Lee J. Kerkhof1, Oscar M. Schofield

1Rutgers, The State University of New Jersey, Institute of Marine and Coastal Sciences,
71 Dudley Road, New Brunswick, New Jersey 08901, USA
2Virginia Institute of Marine and Coastal Science, College of William and Mary, PO Box 1346, Gloucester Point, Virginia 23062, USA
3International Geosphere Biosphere Program (IGBP), The Royal Swedish Academy of Sciences, Box 50005, 104 05 Stockholm, Sweden
4Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, USA
5Bigelow Laboratory for Ocean Sciences, 180 McKown Point Rd., West Boothbay Harbor, Maine 04575, USA

ABSTRACT: Dissolved organic nitrogen (DON) produced by the nitrogen-fixer Trichodesmium sp. has the potential to serve as a nitrogen source for the red tide dinoflagellate Karenia brevis. Dissolved organic matter (DOM) from laboratory cultures of Trichodesmium sp. was isolated, concentrated and then supplied as a nutrient source to K. brevis cells collected from the Gulf of Mexico. K. brevis abundance increased immediately after Trichodesmium sp. cellular exudate (TCE) addition, allowing the population to double within the first 24 h. There was rapid and complete utilization of the TCE DON as well as ~89% of the TCE dissolved organic phosphorus (DOP). Additionally, terminal restriction fragment length polymorphism (TRFLP) was used to assess the bacterial community response to the addition of TCE . The number of bacterial operational taxonomic units (OTUs) initially increased after the TCE DOM addition, but decreased as K. brevis reached its maximum abundance. Electrospray ionization mass spectrometry (ESI-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to chemically characterize the DOM. Approximately 25% of compounds disappeared within the first 24 h, corresponding to the greatest increase in K. brevis abundance. Using FT-ICR MS, 391 DON and 219 DOP potentially bioavailable compounds were characterized. The bioavailable DON compounds were highly reduced and 44% had molar ratios indicative of lipid or protein-like compounds. The changes in DON concentration and compound composition show that Trichodesmium sp. provides a sufficient source of nitrogen to directly or indirectly support K. brevis blooms.

KEY WORDS: Red tide · Trichodesmium · Karenia brevis · DON · FT-ICR MS · ESI-MS

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Cite this article as: Sipler RE, Bronk DA, Seitzinger SP, Lauck RJ and others (2013) Trichodesmium-derived dissolved organic matter is a source of nitrogen capable of supporting the growth of toxic red tide Karenia brevis . Mar Ecol Prog Ser 483:31-45.

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