Transcriptional Markers of Harmful Algal Bloom TerminationEPA Grant Number: F07E20938
Title: Transcriptional Markers of Harmful Algal Bloom Termination
Investigators: Brosnahan, Michael L.
Institution: MIT/WHOI Joint Program
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2007 through January 1, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text | Recipients Lists
Research Category: Aquatic Ecology and Ecosystems , Academic Fellowships , Fellowship - Oceanography and Coastal Processes
I am developing assays of harmful algal blooms’ physiological status. With such assays, future research can characterize stresses encountered by blooms and describe the impact these stresses have on bloom persistence. Bloom declines caused by nutrient stress are associated with formation of resting cysts – the “seed” stage of many phytoplankton species. Patterns in the deposition of these cysts may be a major determinant of a bloom’s range and intensity across seasonal time scales. Further, because deposition patterns are known to reflect nutrient distributions, deposition patterns may also be affected by coastal nutrient pollution. An understanding of the relationships between nutrient stresses and the formation of resting cysts is likely to offer insight into the process of present-time bloom decline, future bloom intensity, and the impacts of changes in coastal nutrient loading.
The onset of nutrient stress in blooms of the toxic dinoflagellate, Alexandrium fundyense, is associated with a switch in the behavior of these cells from mitotic division to sexual fusion. While vegetative and gamete cells are morphologically similar, the difference in their respective behaviors is profound and reflects a change in the suite of molecules expressed by these cell types. A method for assessing both the diversity of cellular RNA molecules and their relative abundance is serial analysis of gene expression (SAGE). SAGE libraries are currently being constructed from a variety of cells samples under different physiological stresses. These libraries will be sequenced and then compared to generate sets of molecular marker candidates. Candidate markers will then be screened under a variety of laboratory and field conditions using macroarray and quantitative PCR assays to verify that they are true markers of either nutrient stress or sexual status.
Identification of genes that are highly and specifically regulated during sexual induction and nutrient stress can lead to the development of transcriptional marker assays for these conditions. The development of such transcriptional marker assays will enable research into the relationships between coastal nutrient pollution and harmful algal blooms. Such assays will also provide tools to inform coastal resource managers of the present status of a chronic harmful algal bloom in New England waters.