Aureococcus anophagefferens causes brown tides that have severely impacted fisheries, seagrass beds, and aquaculture in mid-Atlantic US coastal waters for three decades. The recent sequencing of the Aureococcus genome, combined with comparative genomic studies, in situ ecosystem observations, and experimental studies have collectively evidenced the importance of multiple bottom-up and top-down controls of brown tides. This project seeks to determine the precise environmental factors that drive the initiation, persistence, and demise of brown tides.

Why We Care

Aureococcus anophagefferens is a HAB that causes brown tides that have decimated multiple fisheries and seagrass beds in mid-Atlantic US estuaries for three decades. The recent sequencing of the Aureococcus genome, combined with comparative genomic studies, in situ ecosystem observations, and experimental studies have collectively evidenced the importance of multiple bottom-up and top-down controls of brown tides. While advances have been made in understanding how nitrogen impacts the occurrence of brown tides, the relative importance of other factors that strongly influence the onset of these HABs is unclear.

What We Are Doing

This project will combine field and laboratory studies using eco-transcriptomics (a transcriptome is the set of all RNA molecules in one cell or a population of cells) to address the question: what are the precise environmental factors that drive the initiation, persistence, and demise of brown tides? They will generate transcriptomes (global gene expression* patterns) for Aureococcus cultures exposed to a suite of environmentally conditions relevant to bloom formation including growth on multiple sources of organic matter, exposure to multiple types of zooplankton, selenium limitation, and ideal conditions. These transcriptomes will be used in conjunction with others the PIs have generated during prior projects (low nitrogen, low phosphorus, low light) to define precise transcriptomic signatures elicited by these factors.

(* Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product, such as a protein. Gene expression is often influenced by environmental factors.)

In the field, they will perform metatranscriptomic** profiling of Aureococcus and competing phytoplankton populations in a chronically brown tide-prone embayment during the initiation, persistence, and decline of blooms while concurrently measuring pertinent environmental variables. Assessing environmental conditions in concert with meta-transcriptomes over the course of brown tides will be the crux of our eco-transcriptomic approach: linking of expression of genes by a HAB and competing phytoplankton to specific environmental conditions to define the precise niche of each algal species. This approach will, therefore, provide a comprehensive understanding of the interaction of brown tides and their environment. Since most of the environmental conditions we will explore have been caused by human activities (e.g., high N, high P, high organic matter, high metals, low light), these findings will support managerial actions to ameliorate blooms via the improvement of specific environmental conditions.

(** Metatranscriptomics is the science that studies gene expression of microbes within natural environments.)

Dr. Christopher Gobler of Stony Brook University leads this project. Co-lead is Dr. Sonya Dyhrman (Columbia University). The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Bloom (ECOHAB) Program.