Grantee Research Project Results

2005 Progress Report: Gymnodinium breve in the Gulf of Mexico: Gyroxanthin-based Estimates of Carbon-Specific Growth Rates Under Varying Environmental Conditions

EPA Grant Number: R829369
Title: 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, 2004 through November 14, 2005
Project Amount: $100,387
RFA: Ecology and Oceanography of Harmful Algal Blooms (2001) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water

Objective:

The overall objectives of this research project are to assess the use of gyroxanthin radiolabeling as a diagnostic tool for determining carbon-specific growth rates of Gymnodinium breve (renamed Karenia brevis) and to examine the effects of varying nutrient and light regimes on K. brevis growth rates. This research provides 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:

Experiments related to the original grant objectives have been completed as described in our previous annual report. A manuscript has been prepared, submitted, and currently is in review (Richardson, et al., 2005). Zooplankton/phytoplankton interactions are being studied in coastal ecosystems. The experiments examine the effects of dissolved organic carbon (DOC) that is released during grazing of zooplankton on the growth rate of K. brevis. Because K. brevis is a mixotrophic dinoflagellate, we hypothesized that its growth rate may be stimulated by DOC release. Photopigment radiolabeling is an ideal technique to use to measure growth rate in this context because we measure the specific growth rate (i.e., of individual cells) and not population growth rate (i.e., the increase in cell numbers); thus the technique can be used in the presence of grazers. We found that the growth rate of K. brevis was stimulated by the presence of grazers (collected from North Inlet, SC) but that this stimulation was light-dependent (it occurred only at the higher light intensity investigated). This fits with existing information on the use of organic compounds by some mixotrophic phytoplankton, where an energy source (photosynthesis) is required for uptake and use of organic compounds. The effects of light were manifested, presumably, because more energy was available when cells were grown at the higher light intensity. Some of these results were provided as part of a “Discovery Day” presentation at the University of South Carolina (showcasing undergraduate research).

Future Activities:

We will prepare manuscripts on the results of the growth/grazing experiments and submit them for publication.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views:	All 9 publications	2 publications in selected types	All 2 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	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, ECOHAB, ecology, ecosystem, algal blooms, south central, Gulf of Mexico, Texas, Florida, red tide, bloom,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Geographic Area, Water, algal blooms, Ecological Risk Assessment, State, Ecosystem Protection, Ecology, Biology, Ecosystem/Assessment/Indicators, Oceanography, Environmental Microbiology, Ecological Effects - Environmental Exposure & Risk, Gulf of Mexico, Ecology and Ecosystems, growth cycle, K. brevis, Florida, G. breve red tides, Gymnodinium breve toxins, HAB ecology, brevetoxins, bloom dynamics, ecological exposure, carbon-specific growth rates, microbiology, Karenia brevis

Progress and Final Reports:

Original Abstract

The 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.