CURRENT PROJECTS

Distribution and ecology of eukaryotic microbes of the deep sea

In this project we examine the basin-scale distribution of eukaryotic microbes in the Atlantic from 100 m to 7000 m.  We use epifluorescence microscopy in combination with a technique that visualizes genetic information, a method called tyramide signal amplification fluorescence in situ hybridization (TSA FISH, also know as catalyzed reporter deposition fluorescence in situ hybridization, or CARD FISH). It allows us to distinguish eukaryotic microbes from the other two domains (Archaea and Bacteria) with high reliability. It is also a useful tool in separating taxonomic subgroups of eukaryotic microbes. An important component of this project is the interaction of deep-sea eukaryotes with sinking particles. These particles (marine snow, carcasses and fecal pellets of plankton and micronekton) have a significant contribution to overall carbon flux from the surface to the deep sea. We hypothesize that there are deep-sea eukaryotes that can take advantage of, and live on these particles, and contribute to their decay. The abundance and the species composition of eukaryotic microbes, may in turn may be a reflection of the abundance and composition of these particles making these microbes useful bio-indicators. Deep-sea organisms are a fascinating subject from an eco-physiological point of view because they have to deal with enormous pressures, cold temperatures and an environment that is highly limited in organic nutrient sources. This

project is a collaborative effort with Dr. Gerhard Herndl at  the Netherlands Institute of Sea Research (NIOZ). Graduate student Dani Morgan-Smith is currently enumerating microbes using TSA FISH and an automated epifluorescence microscope customized specifically for this purpose. Funding for this project was provided by the National Science Foundation and by Old Dominion University. It was endorsed by the Integrated Marine Biochemistry and Ecosystem Research (IMBER) project. Read more about our project in their newsletter:  http://www.imber.info/newsletters.html (Issue 7, 2007).

Zooplankton interactions with thin layers

Thin layers are dense horizontal plankton patches which occur in many marine and estuarine environments. We define thin layers as features ranging from a few centimeters to 5 m in thickness, for which the signal (in cell counts, fluorescence, absorbance, acoustic backscatter etc.) exceeds background values by more than 3-fold. Thin layers also have the important property that they are spatially and temporally coherent, sometimes exceeding kilometers and persisting for weeks. In this collaborative project with Drs. Steve Bollens and Gretchen Rollwagen-Bollens, we simulate thin layers in a special plankton research facility at Washington State University Vancouver using 2m tall experimental tanks. We are interested in how organisms interact with each other and with their physical and chemical environment (salinity, nutrients etc.) and contribute to the formation and destruction of thin layers. A main focus of our recent work is on how zooplankton change the flux of organic and inorganic nutrients through various compartments of our experimental system.  In these highly controlled experimental settings, we are able to separate biotic from abiotic factors and find causal relationships for the observed processes.  This project is funded by the Office of Naval Research of the U.S. Navy.

This is a very broadly defined group of research projects in which we examine the effects of food quantity and quality on the feeding response of zooplankton. The response variables vary widely from clearance and ingestion rates to assimilation of nutrients into specific biochemical compartments of the body tissue. Graduate student Danna Palladino studies the incorporation of carbon and phosphorus into major biochemical fractions such as proteins, polysaccharides, low molecular weight compounds, lipids and RNA in the copepod Acartia tonsa. Using the radioactive isotopes C-14 and P-33 as sensitive tracers, we are able to determine the time kinetics of uptake and elimination in biochemical fractions in relation to food quality and quantity.