Grantee Research Project Results
Final 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 Amount: $100,387
RFA: Ecology and Oceanography of Harmful Algal Blooms (2001) RFA Text | Recipients Lists
Research Category: Water , Aquatic Ecosystems
Objective:
The overall objectives of this research project were to assess the use of gyroxanthin radiolabeling as a diagnostic tool for determining C-specific growth rates of Gymnodinium breve (recently renamed Karenia brevis) and to examine the affects of varying nutrient and light regimes on K. brevis growth rates. The research provides a physiological basis for assessing the role of nutrient depletion and changes in irradiance in bloom termination, and the possible affects of anthropogenic nutrient enrichments on the initiation and proliferation of blooms of K. brevis in coastal waters of the Gulf of Mexico.
The specific objectives of this research project are to: (1) determine growth rates of K. brevis in batch cultures at ambient concentrations of N (in varying forms) over a range of irradiances using the photopigment radiolabeling technique, time-series measurements of cell numbers, total chl a, and photopigments; (2) determine growth rates of K. brevis in batch cultures at N concentrations and forms representative of those in nutrient-enriched coastal waters over a range of irradiances using the techniques outlined in 1; (3) compare growth rates of K. brevis grown in semicontinuous cultures to those measured by the gyroxanthin radiolabeling method; and (4) measure growth rates of K. brevis from varying depths and at varying times using gyroxanthin radiolabeling during bloom conditions in the field.
We also were granted supplemental funding to support a graduate student on this project. The objective of the supplemental research is to examine the role of grazers and grazer-associated release of dissolved organic matter on the growth rate of Karenia brevis. Because K. brevis isa mixotrophic dinoflagellate, we hypothesized that its growth rate may be stimulated by dissolved organic carbon (DOC) release. Photopigment radiolabeling is an ideal technique to use to measure growth rate in this context, because we measure specific growth rate (i.e., of individual cells) and not population growth rate (the increase in cell numbers), thus the technique can be used in the presence of grazers.
Summary/Accomplishments (Outputs/Outcomes):
We found that gyroxanthin radiolabeling may be used successfully to determine C-specific growth rates of K. brevis during monospecific blooms. The approach, however, may be of limited use in mixed assemblages when there is low Karenia biomass because low concentrations of gyroxanthin per cell and low turnover rates result in poor signal for the gyroxanthin pigment. Growth rates of K. brevis generally ranged between 0.1 and 0.4 day-1. Cells in batch culture equally grew well on inorganic and organic forms of N, thus they may be physiologically capable of using the major N forms present in agricultural runoff, atmospheric deposition, and other anthropogenic inputs. This has implications for the control of K. brevis blooms in nutrient-impacted coastal waters because organic N inputs should be considered (along with inorganic N) in nutrient management strategies.Our highest C-specific growth rates (0.7 day-1) were measured in the presence of microzooplankton grazers, also indicating that the release of dissolved compounds may play a role in stimulating the growth of K. brevis in nature. These results imply that low-level grazing might stimulate growth of K. brevis, prolonging blooms in nature.
Results of this research will be useful to scientists interested in the growth dynamics of harmful algae. Data collected on pigment concentrations will be useful to agencies involved in the development of gyroxanthin-based monitoring programs for K. brevis (Richardson and Pinckney, 2004). We recently conducted a workshop funded by the National Oceanic and Atmospheric Administration-National Sea Grant to introduce Gulf of Mexico state employees to a gyroxanthin-based monitoring approach, and the interest level was high. A pigment-based approach easily could replace cell-count based approaches to monitoring used presently.
Journal Articles on this Report : 2 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 |
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Richardson TL, Pinckney JL, Walker EA, Marshalonis DM. Photopigment radiolabeling as a tool for determining in situ growth rate of the toxic dinoflagellate, Karenia brevis (Dinophyceae). European Journal of Phycology 2006;41(4):415-423. |
R829369 (Final) |
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Supplemental Keywords:
marine, estuary, toxin, toxics, biology, ECOHAB, south central, Gulf of Mexico, Texas, Florida, red tide, bloom,, 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. brevisRelevant Websites:
http://www.biol.sc.edu/~jpinckney/ecohab.htm Exit
Progress 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.