2014/07/17 by Kelsey Poulson-Ellestad, Kelsey L. Poulson‐Ellestad, Elizabeth Mcmillan +3
Environmental Science · Earth and Planetary Sciences · #Marine Toxins and Detection Methods #Marine and coastal ecosystems #Microbial Community Ecology and Physiology
paper · doi:10.1093/plankt/fbu064
The bloom-forming dinoflagellate Karenia brevis produces a suite of allelopathic compounds that inhibit the growth of several phytoplankton competitors in laboratory experiments. However, it is less clear how allelopathy affects competition in the field, including whether allelopathic compounds impact K. brevis bloom dynamics. We investigated the extent to which phytoplankton species typically found offshore in the Gulf of Mexico, where K. brevis blooms initiate, are sensitive to K. brevis allelopathy. Natural assemblages of offshore phytoplankton dominated by diatoms were largely resistant to K. brevis allelopathy, even experiencing slight stimulation of growth from exposure to K. brevis exudates. When tested in pair-wise laboratory experiments, four diatom species often found offshore in the Gulf of Mexico exhibited varying degrees of resistance to K. brevis similar to that observed with field assemblages, although some competitors displayed a trend toward growth inhibition. In concurrent pair-wise laboratory experiments, four diatom species whose nearshore habitats frequently experience dense K. brevis blooms also demonstrated a range of responses to K. brevis allelopathy, from strong sensitivity to resistance. Overall, Gulf of Mexico phytoplankton that co-occur with K. brevis blooms in both nearshore and offshore environments respond variably to K. brevis allelopathy.