Grantee Research Project Results
2002 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, 2001 through November 14, 2002
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 are 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 effects of varying nutrient and light regimes on K. brevis growth rates. This research project will provide a physiological basis for assessing the role of nutrient depletion (and changes in irradiance) 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:
In the first year of the project, we obtained stock cultures of one Florida clone of K. brevis (Piney Island) and two Texas clones of K. brevis (SP1 and SP3). These cultures were established at four light levels (~20, 80, 130, and 220 µmol quanta m-2 s-1) and have been acclimated for growth on three forms of nitrogenous nutrients (nitrate, ammonium, and urea) at a concentration of 20 µM of each N form. We completed two major batch culture experiments to examine the growth rates of K. brevis (SP3 clone) grown on the three N forms at 80 and 130 µmol quanta m-2 s-1. Growth rates were calculated based on: (1) time series measurements of cell numbers and chlorophyll a; and (2) photopigment radiolabeling of chlorophyll a and gyroxanthin, and comparisons were made between the batch culture time-series and radiolabeling approaches. We found consistency between time-course derived growth rates and 14C-pigment radiolabeling derived rates. Radiolabeling-based rates were sometimes lower than time-course growth rates. Transfer of cells to new incubation containers for 14C incubation is a possible cause. Growth rates based on 14C-chl were easier to distinguish than rates based on 14C-gyroxanthin. In future experiments, we will increase the gyroxanthin signal by filtering more material (cells contain relatively low concentrations of gyroxanthin, especially compared to chlorophyll a content). Rates from radiolabeling experiments done on day 6 were more consistent than measurements from day 10. This may be an early indication of nitrogen "stress." (Nutrients were depleted near day 10.) It was encouraging that the different N states could be detected by using the radiolabeling method. Cells would grow on all N forms tested, showing that they are physiologically "flexible" enough to utilize the major N forms present in agricultural runoff, atmospheric deposition, and other anthropogenic (point and nonpoint source) inputs.
Future Activities:
We will continue the batch culture experiments to include examination of the Piney Island clone under the same irradiance and nutrient conditions described above, and we will examine growth of SP3 and Piney Island clones under an additional light level (220 µmol quanta m-2 s-1). Because they are technically more challenging than the batch culture work (and because we now know that we can grow this somewhat fastidious dinoflagellate in batch culture), we will start the semicontinuous culture work early in the second year of the project.
Journal Articles:
No journal articles submitted with this report: View all 9 publications for this projectSupplemental Keywords:
marine, estuary, toxin, toxics, biology, ecology, ecology and oceanography of harmful algal blooms, ECOHAB, south central, Gulf of Mexico, Texas, TX, Florida, FL, red tide, algae, 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://oceanography.tamu.edu/~pinckney/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.