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Harmful algal blooms: mechanisms, monitoring, and prevention in a rapidly changing world
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The effect of increasing temperature and acidification on the growth and competitive success of toxic Alexandrium catenella from the Gulf of Maine
Wednesday 9th @ 1330-1350, Multifunction Hall
Drajad Seto, School of Marine Sciences, University of Maine, Orono, ME 04469 USA
Lee Karp-Boss, School of Marine Sciences, University of Maine, Orono, ME 04469 USA
Mark L. Wells* , School of Marine Sciences, University of Maine, Orono, ME 04469 USA
Presenter Email: mlwells@maine.edu |
| Climate driven increases in ocean temperature and pCO2 are projected to affect the growth and prevalence of Harmful Algal Blooms (HABs), but there has been little systematic study of how these climate drivers affect HAB organisms within the context of their coastal plankton assemblages. We tested the individual and combined effects of increased temperature and acidification on the growth of the dinoflagellate Alexandrium catenella, the organism responsible for paralytic shellfish poisoning in the Gulf of Maine, both in monocultures and mixed cultures containing non-toxic dinoflagellates. Our findings show that Alexandrium catenella, isolated from mid-coastal waters off the Maine coast, had significantly lower growth rates when temperature was increased from 15 degree C, near present day levels, to 20 degree C. In contrast, the mono-culture growth rates of two other dinoflagellates, Scrippsiella sp. and Amphidinium carterae often observed to co-occur with A. catenella in Gulf of Maine waters, increased significantly at the higher temperature. By comparison, increasing ocean acidification (pH 8.1 to pH 7.8) had no measureable influence on the growth rates of these three species under either ambient or elevated temperatures. This pattern of growth responses with changing temperature and pH were unchanged when A. catenella was grown in mixed cultures with either Scrippsiella sp. or Amphidinium carterae, indicating that allelopathic or other interacting effects were not important under the experimental conditions. However, the negative response of A. catenella to increased temperature in our amended natural seawater medium was more muted when seawater collected in late spring was used in media preparation than with seawater collected in late-summer and fall, suggesting that differences in micronutrients or organic constituents might modify the response of A. catenella to these climate drivers. Overall, our findings suggest that A. catenella will become less competitive against other dinoflagellates as coastal seawater temperatures increase, perhaps leading to less intense and frequent toxic HABs in the Gulf of Maine in the coming decades. A. catenella is a globally distributed toxic species that may exhibit significant strain variability. Future studies should address how broadly the findings here are valid for A. catenella strains in other temperate and tropical waters.
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