|  |
Program |
 |
| |
 |
General Session 3: Biological oceanography & global change |
| |
|
|
CO2 effects on the marine dinoflagellate Karenia brevis - carbon acquisition and photophysiology
Monday 9th @ 1035-1055
Multi-function Hall
Sven A. Kranz* , Florida State University
Tristyn L. Bercel, Florida State University
Presenter Email: skranz@fsu.edu
|
| Karenia brevis, a bloom forming dinoflagellate, frequently forms so-called red tides in the Gulf of Mexico. Its ability to release potent neurotoxins into the water significantly impacts human health as well as marine mammal, bird, and fish mortality. Despite its ecological and economical importance, surprisingly little is known about how this organism assimilates inorganic carbon, how it copes with the reduced CO2 concentrations during dense blooms or how it might respond to an increase in atmospheric CO2. The response to CO2 is especially interesting since the dinoflagellate Rubisco has one of the lowest half saturating concentration values among eukaryotic phytoplankton. Based on this we hypothesized that this species responds strongly, both in growth as well as in physiology to different CO2 concentrations benefitting from an increase in atmospheric CO2.
K. brevis was grown in dilute batch cultures under low, ambient and high CO2 concentrations (120, 400 and 760ppm CO2). Growth rates, photosynthesis as well as carbon acquisition processes were measured. No significant change in growth rate was detected between ambient and high CO2. A distinct diurnal rhythm in photosynthesis and respiration was observed with small differences between the CO2 treatments. Generally high respiration was present. Both 14C-kinetic as well as O2-kinetic measurements showed moderate affinities to inorganic carbon under all CO2 concentrations tested. HCO3- was determined to be the dominant carbon source, yet CO2 was taken up as well. The HCO3- / CO2 uptake ratio did not change significantly under different CO2 concentrations as measured with the 14C-disequilibrium method. Membrane inlet mass spectrometry measurements revealed only little external CA activity, with no clear difference between treatments. Our data is the first experimental analysis on carbon acquisition in this important dinoflagellate and shows that Karenia employs an efficient CCM to saturate RubisCO to efficiently grow under any of the tested CO2 concentration. We also showed that Karenia brevis might not be affected by enhanced CO2 availability, a pattern which was also measured in several other dinoflagellate species. Yet, further research on toxin production under high and low CO2 has to be conducted to understand a potential change in cellular toxisity.
|
|
|
|
|