Robert W. Howarth

David R. Atkinson Professor of Ecology & Environmental Biology

Department of Ecology and Evolutionary Biology
Cornell University
E311 Corson Hall
Ithaca NY 14853
Office: (607) 255-6175
Fax: (607) 255-8088
E-mail:rwh2@cornell.edu

CV Link

 

 

Graduate Students

Bettez Neil Bettez
Graduate Student
Ecology and Evol. Bio.
Woods Hole, MA. 02543
ndb23@cornell.edu

 

Turner Caroline Turner
Graduate Student
Ecology and Evol. Bio.
Corson Hall
cbt5@cornell.edu

 

MahlUrsula Mahl
Graduate Student
Natural Resources
Little Rice
uhm2@cornell.edu

Research

Research in the Howarth lab has several foci centering around the role of biogeochemical cycles and physical processes in structuring coastal marine ecosystems and on human perturbations of biogeochemical cycles at the ecosystem, regional, and global scales. One focus is the apparent paradox that primary production is often limited by phosphorus (P) in temperate-zone lakes and by nitrogen (N) in many temperate-zone estuaries. A variety of mechanisms lead to this difference, but differences in N fixation are of fundamental importance. In lakes, planktonic N fixation usually makes up any temporary deficits in N compared to P, keeping these systems P-limited. N fixation by planktonic organisms does not occur in most estuaries and coastal marine ecosystems, even when these systems are extremely N limited. We have tested many hypotheses for the relative paucity of nitrogen fixation in estuarine waters: our current thought is that the availability of trace metals required for N fixation (Fe and Mo) is low in seawater, resulting in low potential growth rates of N-fixing organisms; this makes them vulnerable to grazing by zooplankton and benthic filter feeders. We have tested this hypothesis with mesocosm experiments, microcosm experiments, and simulation modeling.

Another major interest is how humans alter the nitrogen cycle, how this varies among regions, and what the consequences are for coastal marine ecosystems. We have demonstrated that for large watersheds and regions in the temperate zone, the delivery of nitrogen in rivers is a linear function of the net anthropogenic nitrogen inputs (NANI) to that region. The major inputs for most of the regions and watersheds in our analysis are agricultural and deposition from the atmosphere of nitrogen from fossil fuel combustion. We currently are exploring how changes in hydrology affect these riverine fluxes, and how this paradigm might be applied in the tropics. We are also developing models for managers to use to predict sources of nitrogen inputs to coastal ecosystems, and to explore the ramifications of various management options for reducing nitrogen fluxes. We are also interested in characterizing the sensitivity of coastal systems to nutrient over-enrichment.

Other interests concern the metabolism of the Hudson River estuary and its relation to climate and to land use in the watershed, the processes responsible for P adsorption by carbonate sediments in nearshore tropical marine ecosystems (and the mechanism whereby this adsorption slows in more eutrophic systems, providing a positive feedback in P availability and eutrophication), and how nitrogen and phosphorus biogeochemical processes vary along salinity gradients in estuaries (and how these compare to the processes in lakes).

Much of the work in the Howarth lab attempts both to address fundamental ecological questions and to contribute to practical issues of environmental management. For instance, our work not only describes fundamental differences on controls on N and P cycles in estuaries and freshwaters but contributes to managing eutrophication of coastal marine ecosystems.

Staff

Marino

Roxanne Marino
Senior Research Assoc.
& Laboratory Manager
Ecology and Evol. Bio.
E311 Corson Hall
rmm3@cornell.edu
(607) 255-4285

 

 

Swaney Dennis Swaney
Coordinator of Modeling
Ecology and Evol. Bio.
E311 Corson Hall
dps1@cornell.edu
(607) 255-3572

 

Peter Woodbury
Research Associate
Crop and Soil Sciences
1017 Bradfield Hall
pbw1@cornell.edu
(607) 255-1448

Butler Tom Butler
Institute of Ecosystem Studies
211 Rice Hall
tjb2@cornell.edu
607/255-3580

 

Hong Bongghi Hong
103 Little Rice
bh43@cornell.edu

 

 

Hahn Melanie Hayn
Staff/ Graduate Student
Ecosystems Center
7 MBL Street
Woods Hole, MA 02543
mkh23@cornell.edu

molovMarina Molodovskaya
Stud. Lab Tech
mm433@cornell.edu

 

 

Horowitz Michael Horowitz
Research Technician
E301 Corson Hall
meh55@cornell.edu
(607) 255-2013

 

Renee Santoro
Research Technician
E301 Corson Hall
rls75@cornell.edu
(607) 255-2013