ECOHAB 2010: Project Summaries

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Title: The Ecophysiology and Toxicity of Heterosigma akashiwo in Puget Sound: A Living Laboratory Ecosystem Approach

Institutions: NOAA Northwest Fisheries Science Center, San Francisco State University, The University of Western Ontario, University of Maine, Norwegian National Veterinary Institute, Rensel Associates Aquatic Sciences; America Gold Seafood

Investigators: Vera L. Trainer, William P. Cochlan, Charles G. Trick, Mark L. Wells, Chris O. Miles, Jack Rensel, Kevin Bright

Over one half of the world’s fish production for human consumption currently comes from aquaculture while wild fisheries’ yields are either stable or declining. Recurring threats from the raphidophyte, Heterosigma akashiwo Hada (Sournia) have caused extensive damage ($2-6 million per episode) to wild and net-penned fish of Puget Sound, Washington, and are believed to be increasing in scope and magnitude in this region, and elsewhere in the world over the past two decades. The mechanism of H. akashiwo toxicity is not well understood. The toxic activity of H. akashiwo has been attributed to the production of reactive oxygen species, brevetoxin-like compound(s), excessive mucus, or hemolytic activity; however these mechanisms are not confirmed consistently in all fish-killing events or cultured strains. The difficulty of conducting research with active, toxin-producing field populations of H. akashiwo have resulted in conflicting findings from those obtained in lab culture studies, thereby limiting the ability of managers and fish farmers to respond to these episodic blooms. The overall goal of this project is to identify the primary toxic element and the specific environmental factors that stimulate fishkilling H. akashiwo blooms, and thereby provide managers with the fundamental tools needed to help reduce the frequency and toxic magnitude of these harmful algal events. Studies to date have provided incomplete and conflicting observations on the mode of toxicity and the environmental stimulation of toxification. A three-pronged approach is proposed to study the environmental controls of H. akashiwo growth and toxin production; laboratory culture experiments, field observations, and bottle and mesocosm manipulation experiments.

Objectives

1. Identify the element(s) of toxic activity (inorganic, organic, or synergistic) associated with blooms of H. akashiwo and its various cellular morphologies.

2. Determine the environmental parameters that stimulate the growth success and expression of cell toxicity in the H. akashiwo populations of Puget Sound.

Approach:  Because previous studies have used H.akashiwo cultures with little or no toxic activity, this approach uses a “living laboratory” to study H. akashiwo bloom ecology and toxicity using natural assemblages. A mobile lab at field sites where H. akashiwo cells are regularly found will enable full characterization of the toxic element(s) responsible for fish mortality, and the environmental factors influencing toxicity. Findings from annual field studies in late June and two rapid response deployments during major bloom events will be confirmed using laboratory studies with fresh (< 6 mo. old) isolates

Expected results:

1. Determination of the key elements of toxicity of H. akashiwo

2. Characterization of the environmental variables that influence either the induction or depression of elements of toxic activity in H. akashiwo

3. Strategy for realistic mitigation of H. akashiwo activities in Puget Sound, Washington.




Title: Modeling favorable habitat areas for Alexandrium catenella in Puget Sound and evaluating the effects of climate change

Institutions: NOAA Northwest Fisheries Science Center, Seattle WA, Woods Hole Oceanographic Institution, University of Washington

Investigators: J.E. Stein, S.K. Moore, D.M. Anderson, E.P. Salathé, Jr., N.J. Mantua, N.S.Banas, C.L. Greengrove, B.D. Bill, V.L. Trainer

The dinoflagellate Alexandrium catenella produces a suite of potent neurotoxins that accumulate in shellfish and cause severe illness or death if contaminated shellfish are consumed by humans. Alexandrium catenella form dormant cysts that overwinter on the seafloor and provide the inoculum for toxic blooms the following summer when conditions become favorable again for growth of the motile cell. A 2005 survey of A. catenella cyst distribution in Puget Sound, Washington State, identified “seedbeds” with high cyst abundances that correspond to areas where shellfish frequently attain high levels of toxin. However, even at these sites, interannual variability in the magnitude of toxic events is high. In order to provide advanced warning of A. catenella blooms, managers need to know how much “seed” is available to initiate blooms, where this seed is located, and when/where this seed could germinate and grow. Evaluating how favorable habitat areas for cyst germination and vegetative growth will be altered by climate change would allow for risk assessments of A. catenella blooms through until the late 21st century.

Objectives:

  1. Determine interannual variations in A. catenellacyst distribution in Puget Sound.
  2. Quantify rates of cyst germination and vegetative growth for a range of temperature, salinity, and light conditions.
  3. Determine the presence/absence of an endogenous clock that regulates cyst germination.
  4. Model favorable habitat areas for cyst germination and vegetative growth.
  5. Evaluate climate change impacts on favorable habitat areas.
  6. Establish a time series with sufficient depth to provide seasonal forecasts of toxic blooms.

Approach: To achieve these goals, they will conduct annual cyst surveys at ~80 stations throughout Puget Sound and in the Strait of Juan de Fuca. Laboratory experiments will be performed to determine the optimal ranges of environmental parameters that maximize rates A. catenella cyst germination and vegetative growth. This information will be combined with output from an existing numerical ROMS-based model of Puget Sound circulation to model favorable habitat areas for A. catenella at ~200 m resolution.  Downscaled regional climate change projections for Washington State will be used to construct new forecast scenarios the ROMS model and evaluate changes to favorable habitat areas for A. catenella through the late 21st century. Finally, once a time series with sufficient depth is established, the ability to provide seasonal bloom forecasts will be determined by relating cyst abundances with the magnitude of toxic events the following summer/fall.

Expected results:  The expected outcomes of this project include the production of seamless maps indicating favorable habitat areas for A. catenella in Puget Sound now and in a future warmer climate. These maps will be used by shellfish farmers and managers to guide harvesting and monitoring practices in space and time.


 


 

 

Title: Establishing the sources of phosphorus promoting toxic cyanobacteria blooms

in the US Great Lakes using gene expression assays

Institutions: Stony Brook University, New York Sea Grant Extension, Cornell Univ. Cooperative Extension

Investigators: Christopher J. Gobler, James W. Ammerman, Charles O’Neil

Toxic cyanobacteria blooms represent a serious threat to human health, natural resources, and economies dependent on the US Great Lakes. Cyanobacteria blooms are common within eutrophic systems with elevated phosphorus levels and recent studies have found that P enrichment can specifically promote toxic strains of the harmful cyanobacteria, Microcystis.  Management plans focused on improving the quality of freshwater systems typically strive to reduce concentrations of total phosphorus (TP), despite the variable distribution and lability of different components of TP, including particulate, dissolved, organic, and inorganic. While dissolved inorganic P is the most bioavailable, some information suggests that dissolved organic P (DOP) may be important for promoting blooms of Microcystis. However, the extent to which Microcystis blooms utilize DOP during blooms has not been established as the methods for measuring alkaline phosphatase activity are not species-specific and/or include the activity of heterotrophic bacteria. Recently, the genomes of two clones of Microcystis have been sequenced. Our exploration of these genomes and our own clones of Microcystis have revealed that Microcystis possesses an alkaline phosphatase gene, although it is not the gene present in model bacteria (phoA) but rather it possesses phoX. Furthermore, these Microcystis clones also contain a high affinity phosphate transporter, pstS, sphX, and other P transporters. Prior research has shown that alkaline phosphatase genes and phosphate transporters are tightly regulated in response to changes in ambient P conditions.

Objectives:  Therefore, the objectives of this proposal are to develop quantitative gene expression assays for Microcystis alkaline phosphatase and phosphate transporters and to quantify how the expression of these genes is regulated by changes in exogenous P concentration and sources. Within regions of the Great Lakes prone to Microcystis blooms, we will establish gene expression patterns in parallel with the dynamics of nutrients, phophatase enzyme activity, microcystin, and densities of toxic and non-toxic Microcystis cells. Finally, we will examine expression patterns of P transport and metabolism genes during fieldbased, nutrient amendment experiments within regions of the Great Lakes prone to Microcystis blooms using differing sources of organic and inorganic P. These combined approaches will provide an indication of the role of organic and inorganic P in the occurrence Microcystis in the Great Lakes. Our final objective is an outreach campaign based on our findings. Co-PI O’Neill will work with Gobler and Ammerman to develop a factsheet and to host workshops focused on the role of P in the dynamics of Microcystis blooms. End users of the fact sheet and participants in the workshops will include state, local, and federal water treatment facilities, health departments, resource management agencies, stakeholders who constitute sources of phosphorus to the Great Lakes, educators promoting public outreach and education and the news media.



Last updated: May 15, 2013