Nano microplankton : 



Strengths. Grazing by nano- and microzooplankton is now recognized as usually the dominant 

 biological loss term for primary production in most aquatic ecosystems. Combined measurements 

 of grazing rate and composition/biomass has proven to be a powerful tool elsewhere (e.g. JGOFS) 

 in assessing not only the production, cycling, and fate of plankton POC, but also as a tool to 

 interpret data from more "black-box" approaches ( 14 C, thorium budgets, sediment traps). The use 

 of color image analysis provides increased accuracy, precision, and sample processing speed (i.e., 

 greater spatial and temporal resolution). The immunochemical approach will, if successful, 

 provide the first estimates of transfer of microzooplankton carbon to larger predators. 



Limitations. The major problem in evaluating the roles of nano- and microplankton is their small 

 size. Technology is not yet available to quantify their composition, abundance, size distribution, 

 (carbon) biomass, grazing, or growth rates in situ. Until that time, detailed spatial and temporal 

 mapping of plankton will be manpower-dependent. 



STATUS OF RESEARCH 



Our studies on pelagic tunicates resulted in several original data: we were successful in 

 obtaining two complete life cycles of the doliolid Dolioletta gegenbauri under experimental 

 conditions, simulating in situ. One complete life cycle lasted 28 days at ~45ugC/l of 

 phytoplankton. Feeding rates at these food levels surpassed previously obtained values by factors 

 2 to 3 which is attributed to providing near optimal conditions for these doliolids. During the 

 following months we intend to obtain rates on sexual and asexual reproduction as well as on 

 growth at various natural food levels to calculate carbon consumption and production by a 

 doliolid assemblage. 



Improvements to our imaging system are either in place or will be completed by the end 

 of the current funding period. We have upgraded our software, added an x-y-z-axis controller 

 and a motorized microscopic stage. A state-of-the-art cooled integrating Optronics color CCD 

 will replace the existing (excellent but aging) Hitachi CCD. Antibodies to several ciliate antigens 

 (cell surface and whole cell) have been prepared and are presently being tested for specificity and 

 cross-reaction with other plankton. We have developed an incubation method to measure 

 ingestion of both autotrophic and heterotrophic plankton by metazooplankton. 



We participated in the May 1993 and March 1994 "biology" cruises, and we will be 

 aboard the June 1994 cruise to Cape Hatteras. Data analysis from the first cruise is complete. 

 Results were presented at the September 1993 OMP PI meeting. A poster will be presented at 

 the ICES Symposium on Zooplankton Production in Plymouth (August 1994) and a joint 

 manuscript with BNL scientists (Verity et al.) has been recently written. Another manuscript 

 comparing March, May and June-July data is anticipated in early 1995. 



Keywords: microzooplankton, metazooplankton, grazing, phytoplankton, biomass, composition 



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