%0 Journal Article
%T Impact of nitrogen chemical form on the isotope signature and toxicity of a marine dinoflagellate
%A C. Taylor Armstrong
%A Christopher J. Gobler
%A Deana L. Erdner
%A Donald M. Anderson
%A James W. McClelland
%A Juliette L. Smith
%A Marta P. Sanderson
%J Marine Ecology Progress Series (MEPS)
%@ 1616-1599
%D 2018
%R 10.3354/meps12619
%X ABSTRACT: Stable isotopes are used to identify and track nitrogen (N) sources to water bodies and thus can be used to ascertain the N source(s) used by the phytoplankton in those systems. To focus this tool for a particular harmful algal species, however, the fundamental patterns of N isotope fractionation by that organism must first be understood. While literature is available describing N isotope fractionation by diatoms and coccolithophores, data are lacking regarding dinoflagellates. Here we investigated the effects of N chemical form on isotope fractionation (¦¤) and toxin content using isolates of the dinoflagellate Alexandrium catenella in single-N and mixed-N experiments. Growth of A. catenella exclusively on nitrate (NO3-), ammonium (NH4+), or urea resulted in ¦¤ of 2.7 ¡À 1.4, 29 ¡À 9.3, or 0.3 ¡À 0.1¡ë, respectively, with the lowest cellular toxicity reported during urea utilization. Cells initially utilized NH4+ and urea when exposed to mixed-N medium and only utilized NO3- after NH4+ decreased below 2 to 4 ¦ÌM. This pattern of N preference was similar across all N treatments, suggesting that there is no effect of preconditioning on N chemical preference by A. catenella. In NO3-- and urea-rich environments, the ¦Ä15N of A. catenella would resemble the source(s) of N utilized, supporting this tool¡¯s utility as a tracer of N source(s) facilitating bloom formation, but caution is advisable in NH4+-rich environments, where the large ¦¤ value could lead to misinterpretation of the signal.
%U https://www.int-res.com/abstracts/meps/v602/p63-76/