Major Long-Term Objectives:

1. Determine nutritional controls on Pfiesteria's growth and toxic activity, toward developing this organism as an indicator of overall estuarine stress (.health.).

2. Examine the role of the amoeboid and flagellated stages in the complex life cycle of P. piscicida on microbial and higher trophic levels of estuarine food webs.

3. Develop molecular probes to facilitate rapid, reliable identification of all stages in Pfiesteria's complex life cycle.

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Major Short-Term Objectives:

1. Examine Pfiesteria's response to crossed gradients of N and P loading.

2. Continue to establish Pfiesteria's role in major estuarine fish kills.

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Accomplishments:

1. Discovered that P. piscicida has a complex life cycle with at least 19 stages, dominated by amoeboid rather than flagellated forms.

2. Established that some life cycle stages are highly stimulated by nutrient over enrichment (P,N).

3. Demonstrated that significantly higher abundance of this organism occurs near sewage outfalls and other sites of water quality degradation (e.g, tidal creeks affected by urban runoff, estuaries affected by animal waste spills, etc.).

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Significance:

This research will enhance our ability to detect Pfiestera across regions of occurrence, and will make it possible to map "hot spots" in North Carolina's estuaries. Development of molecular probes for this organism will greatly facilitate its early detection in estuaries so that we can more readily establish its role as a causative agent of fish kills/disease, and in aquaculture facilities so that major kills of cultured fish can be avoided. Insights from the data will improve strategies for evaluating chronic sublethal effects from shellfish and finfish exposure to this toxic dinoflagellate, and will additionally enable evaluation of its potential utility as a biosensor of estuarine stress to fisheries from cultural eutrophication. Recognition of an array of amoeboid stages -- not previously even recognized as dinoflagellates ~ also will make it possible to more realistically assess the overall role of dinoflagellates in estuarine microbial food webs.

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Future Plans:

1. To determine the overall influence of cultural eutrophication in stimulating Pfiesteria.

2. To assess the importance of its chronic sublethal impacts on fish populations.

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Published by: North Carolina Cooperative Extension Service

Publication Number:

Last Electronic Revision: January 1997 (MSD)

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