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Presenters Notified: November 2012

Program Schedule Posted:November 2012

Abstracts Available: January 2013

Meeting:
17-22 February 2013

Berges, J. A., U. Wisconsin-Milwaukee, USA, berges@uwm.edu
Sandgren, C. D., U. Wisconsin-Milwaukee, USA, sandgren@uwm.edu
Kozik, C. R., U. Wisconsin-Milwaukee, USA, crkozik@uwm.edu
Hellweger, F., Northeastern University, USA, ferdi@coe.neu.edu

DIVERSE CAUSES OF CELL DEATH IN PHYTOPLANKTON IN SMALL FRESHWATER ECOSYSTEMS

Various forms of phytoplankton cell death (i.e. the appearance of intact, non-functional cells in the water column) have gained acceptance in the literature in the past decade, but the causes of such mortality remain poorly understood. We examined seasonal patterns of mortality in pond ecosystems that allow frequent and comprehensive sampling using cell staining techniques coupled with epifluorescence microscopy and flow cytometry. For some species (e.g. the chlorophyte Pediastrum sp.), ‘bottom-up’ factors (e.g. changing irradiance, temperature and nutrients) are sufficient to account for mortality, but for many other species (e.g. cyanobacteria, Anabena sp., dinoflagellates, Peridinium sp.) more complex mechanisms including pathogenic and allelopathic interactions are indicated. Coupling short-term large-volume incubation experiments and tightly-controlled culture experiments to in situ monitoring allows us to examine such interactions. Availability of cell-specific flow cytometric measurements also allows application of individual-based models. Such models can be effectively presented in web-based formats that engage K-12 audiences. Moreover, use of time-lapse photography of macroscopic seasonal changes in ponds helps the public relate changes they can observe to research going on at the microscopic scale.

Oral presentation

Session #:SS79
Date: 2/21/2013
Time: 16:00