C. polykrikoides blooms can turn over labile nitrogen species (ammonium, nitrate, and urea) and vitamin B12 in the bloom in 1.5 and 10 days, respectively, outside the bloom, potentially making acquisition of these limiting elements more difficult for other plankton. C. polykrikoides may rely on its ability to vertically migrate and a B12 producing and nitrogen re-mineralizing microbial community to supply its nitrogen and vitamin requirements. In conclusion,