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Current Research |
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Identifying Regulatory Mechanisms for Heterosigma akashiwo Bloom Formation: Predation Interactions with Algal Behavior and Resource Use (Start Date: September 2006) |
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This ECOlogy of Harmful Algal Blooms (ECOHAB) project is a collaborative effort with Susanne Menden-Deuer (WWU, URI). H. akashiwo, a raphidophyte, causes fish kills yearly in coastal waters around the Pacific Rim. Our project goal is to combine traditionally separate “bottom up” and “top down” approaches to learn how H. akashiwo nutrient use and behavior affect its susceptibility to predation by protists. Work with H. akashiwo isolates and heterotrophic protists in the laboratory will determine the relative importance of toxicity versus feeding deterrence in reducing H. akashiwo mortality from protist predators. We will also investigate use of organic N sources for H. akashiwo growth. This raphidophyte often forms layers in coastal water columns. We will study layer formation using novel spatially structured laboratory environments, coupled with video and motion analysis techniques to quantify individual- and population-level behaviors of H. akashiwo and protist grazers.
In early July 2006, a massive H. akashiwo bloom formed in and moved through waters of northern Puget Sound and the Strait of Juan de Fuca (Seattle Times Article). High densities of H. akashiwo in the waters around the San Juan Islands resulted in the death of thousands of penned Atlantic salmon. We are in the process of isolating and culturing both H. akashiwo and heterotrophic protists associated with this bloom; two H. akashiwo strains isolated from the bloom can be found at the Provasoli-Guillard Center for Culture of Marine Phytoplankton (CCMP). Strain numbers for the two isolates are CCMP 2808 and CCMP 2809.
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June 2006 Heterosigma akashiwo bloom off Shannon Point Beach. (photo by K. Fredrickson) |
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Diatom Chemical and Mechanical Defenses (Start Date: February 2006)
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In geologically recent times, diatoms have evolved to become one of the most successful phytoplankton taxa in the sea, responsible for an estimated 40% of marine primary production. The sustained blooms that diatoms often experience are one attribute leading to their high primary production. What allows so many diatom cells to escape the zooplankton grazing pressure that removes most other phytoplankton from the sea on a daily basis? Recently, both chemical and mechanical defenses have been hypothesized to deter grazers that might otherwise consume diatoms. Reactive polyunsaturated aldehydes (PUAs) derived from C20 fatty acids upon diatom wounding have been shown to inhibit cellular processes in numerous marine organisms. The silica frustules of diatoms have also been hypothesized to constitute a mechanical defense against zooplankton. In this new research project, we will test the effectiveness of these chemical and mechanical defenses against protist grazers. Protist feeding, growth, and the cellular basis for chemical damage will be evaluated in experiments with diatoms that express a range of defense levels. Fred Prahl is working with us to measure levels of reactive aldehydes in diatoms grown under a range of conditions. Our overall goal is to test the effectiveness of these putative chemical and mechanical defenses against protist grazers.
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Drawings of observed protist grazing on diatoms. |
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A post-genomic approach to Synechococcus – grazer interactions (Start Date: March 2007)
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This project uses the abundant marine cyanobacterial genus Synechococcus as a model organism for exploring morphological, behavioral, and chemical resistance strategies of microbial prey against protozoan grazers. In collaboration with Brian Palenik and Bianca Brahamsha we plan to use different Synechococcus isolates, including genetically characterized mutants, to investigate the role of cell surface structures in modifying predation. The project will use the recent availability of complete genomes and molecular genetics tools to determine the key cell structures under selection by diverse protist grazers. |
Oxyrrhis with ingested Synechococcus cells. (photo by K. Bright) |
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GLOBEC Northeast Pacific Synthesis Study: Links Between Climate and Planktonic Food Webs (Start Date: October 2006) |
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With colleagues from
LUMCON (Mike
Dagg) Project goals: • Describe the planktonic food web in the CGoA study region. • Provide an integrated view of conditions in the CGoA during each of the field years (1998-2004), and place these conditions in a multi-decadal climate context using longer-term environmental data sets. • Combine each year's environmental description with food web structural/ and functional relationships to: (a) describe interannual variations in primary and secondary production; (b) investigate probable mechanisms driving these variations; and (c) determine their consequences for target organisms: Neocalanus spp., euphausiids and juvenile pink salmon. We propose to use box, statistical and 1-D ecosystem models to address a range of questions about climate-food web linkages.
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