Grantee Research Project Results
2003 Progress Report: Gymnodinium breve in the Gulf of Mexico: Gyroxanthin-based Estimates of Carbon-Specific Growth Rates Under Varying Environmental Conditions
EPA Grant Number: R829369Title: Gymnodinium breve in the Gulf of Mexico: Gyroxanthin-based Estimates of Carbon-Specific Growth Rates Under Varying Environmental Conditions
Investigators: Richardson, Tammi L. , Pinckney, James L.
Institution: Texas A & M University
EPA Project Officer: Packard, Benjamin H
Project Period: November 15, 2001 through November 14, 2004 (Extended to March 1, 2006)
Project Period Covered by this Report: November 15, 2002 through November 14, 2003
Project Amount: $100,387
RFA: Ecology and Oceanography of Harmful Algal Blooms (2001) RFA Text | Recipients Lists
Research Category: Water , Aquatic Ecosystems
Objective:
The objectives of this research project are to: (1) assess the use of gyroxanthin radiolabeling as a diagnostic tool for determining C-specific growth rates of Gymnodinium breve (recently renamed Karenia brevis); and (2) examine the effects of varying nutrient and light regimes on K. brevis growth rates. This research will provide a physiological basis for assessing the role of nutrient depletion (and changes in light intensity) in bloom termination, and the possible effects of anthropogenic nutrient enrichments on the initiation and proliferation of blooms of K. brevis in coastal waters of the Gulf of Mexico.
Progress Summary:
During Year 2 of the project, we continued our work with batch cultures of K. brevis, focusing specifically on measuring growth rates using gyroxanthin radiolabeling. In Year 1, we were able to get an accurate analytical signal for growth rates of K. brevis based on radiolabeling of chl a (the most abundant photosynthetic pigment in phytoplankton). However, we found that low concentrations of gyroxanthin per cell and relatively low inherent growth rates of this organism made it difficult to get reliable rates based on gyroxanthin. Further research conducted in Year 2 of the project, determined that a gyroxanthin signal could be obtained by filtration of larger sample volumes. When the concentration of K. brevis is relatively high, growth rates determined by photopigment radiolabeling (of chl a and gyroxanthin) were not significantly different from rates determined by time-course measurements of chl a when the calculation method of Goericke and Welschmeyer (1992) was used. We concluded that the utility of the gyroxanthin approach for measuring Karenia-specific growth rates may be limited to situations where: (1) there are relatively high cell concentrations (e.g., monospecific blooms); (2) cells have relatively high gyroxanthin concentrations; and (3) cells are dividing at near maximal rates. The approach may not be as useful for examining pre- and post-bloom scenarios where K. brevis does not dominate the phytoplankton assemblage. Growth rate measurements to date, however, have been made on cultured populations of K. brevis and not on natural populations. If natural populations are growing more quickly, or if the concentration of gyroxanthin per cell is higher than in the cultured cells, this approach may be more widely applied. Research has shown that gyroxanthin concentration per cell varies widely in natural blooms. Further assessments of the utility (and limitations) of the 14C radiolabeling approach have started with semicontinuous cultures of K. brevis (SP3 clone) growing on nitrate, ammonium, and urea. These cultures have been established for approximately 1 month. We will continue to dilute them on the current schedule until cell counts indicate that near steady state growth has been achieved.
Also in Year 2 of the project, we have done extensive work towards the characterization of basic physiological processes in this dinoflagellate. This work was stimulated by questions that arose during the batch culture growth rate experiments. Will cells grow more quickly at higher light intensities, and therefore, provide a stronger gyroxanthin radiolabeling signal, or are they acclimated to growth at the relatively low irradiance conditions that we have provided in the laboratory? Growth rate versus irradiance, and photosynthesis versus irradiance experiments indicated that this organism adapted to higher light. We now are acclimating cells in the laboratory to relatively high light (approximately 400 µmol quanta m-2 s-1) and will repeat radiolabeling experiments at this irradiance.
Future Activities:
We will complete batch culture experiments with K. brevis by December 2003, after which a manuscript will be prepared for submission to the Journal of Phycology. Work in Year 3 of the project will focus on the establishment and analyses of growth rates in semicontinuous culture.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 9 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Richardson TL, Pinckney JL. Monitoring of the toxic dinoflagellate Karenia brevis using gyroxanthin-based detection methods. Journal of Applied Phycology 2004;16(4):315-328 |
R829369 (2003) R829369 (2005) R829369 (Final) |
not available |
Supplemental Keywords:
marine, estuary, toxin, toxics, biology, ecology, ECOHAB, south central, Gulf of Mexico, Texas, TX, Florida, FL, algae, bloom, algal bloom, red tide., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, Oceanography, State, Ecological Effects - Environmental Exposure & Risk, Environmental Microbiology, algal blooms, Ecological Risk Assessment, Ecology and Ecosystems, Biology, Gulf of Mexico, ecological exposure, microbiology, bloom dynamics, brevetoxins, growth cycle, HAB ecology, Gymnodinium breve toxins, Texas (TX), carbon-specific growth rates, Florida, Karenia brevis, K. brevisProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.