Iris C. Anderson

Research Interests

Current Projects

Selected Publications

Students

Courses

Professional Memberships

Research Interests

During the last several years my research focus has been in the area of nitrogen and carbon cycling, primarily in shallow subtidal and intertidal systems. I am particularly interested in the role that coastal lagoons and small estuaries with long residence times play in removing or retarding the flow of nutrients during transport from the mainland to the coastal ocean. Biogeochemical processes that we investigate include microbial mineralization, nitrification, denitrification, immobilization. Most of the methods used for determinations of process rates involve application of stable nitrogen isotope techniques. We are currently performing studies in Hog Island Bay, located in the Virginia Coast Reserve, a NSF-funded Long Term Ecological Research Site, to determine the fate of dissolved organic matter (DOM) derived from the annual bloom of macroalgae that occurs in spring and early summer. We are interested in understanding how the source of DOM affects the rate at which it is metabolized in the water column. For example, we hypothesize that dissolved organic nitrogen or carbon derived from a forested watershed will be metabolized more slowly than that derived from macroalgae or phytoplankton undergoing decomposition following a bloom event. Thus, we will compare microbial N mineralization in Hog Island Bay where the organic N is primarily produced in situ with that at another LTER site, Plum Island Sound, where the DOM is derived mainly from forested or urbanized watersheds. The rate at which dissolved organic matter is metabolized will affect water quality characteristics, including dissolved oxygen and nitrogen concentrations. Low dissolved oxygen (hypoxia) is a major problem in many estuaries and causes stress to higher trophic levels, including fish. Dissolved oxygen concentrations, both in sediments and the water column, also play a role in determining the fate of dissolved inorganic nitrogen produced by microbial mineralization.

Approximately 30 - 40% of the surface area of east coast estuaries is 2 m or less in depth; thus, shallow aquatic or littoral zone ecosystems are likely to play an important role in determining water quality within these estuaries. The littoral zone is where critical living resources such as seagrasses are located; it is also where important commercial activities such as clam aquaculture take place. There has been some conflict between those interested in increased development of aquaculture areas and those concerned with conserving seagrass habitat. We are currently involved in a project to assess the interactions that occur between seagrass, clam, and macroalgal communities. We will perform studies to evaluate nutrient dynamics in habitats with isolated communities and those in which these communities co-exist.

Intertidal systems of interest include both salt- and freshwater marshes. We are attempting to better understand how or if marshes support the food web in adjacent rivers or estuaries. We have completed carbon and nitrogen mass balance models for both a salt- and freshwater marsh. We are now applying isotopic techniques to determine the sources of carbon and nitrogen both to the marsh itself and to a tidal creek and river adjacent to the freshwater marsh. Sediment inputs, both inorganic and organic, are also crucial to understanding the role of marshes in the estuarine landscape. We have been measuring sediment inputs to a tidal freshwater marsh over various time scales ranging from weekly to decadal.

Whereas nutrients are transported from watersheds to large estuaries primarily by rivers, in small estuaries and lagoons groundwater may be the most important source of dissolved inorganic nitrogen (DIN). Although DIN- nitrate seems to be transported conservatively in sandy sediments, it may undergo denitrification as it is discharged through more organic-rich sediments, either at groundwater - marsh interfaces or in shallow subtidal sediments. We have completed a study of in situ processing of DIN at the groundwater marsh interface and are currently involved in determining the role that groundwater plays in supplying DIN to a small estuary (The Great Wicomico River).

Finally, atmospheric deposition high in nitrogen, sulfur, and acids has saturated forested watersheds in Central Europe with nutrients. As a result forests have died-off and lakes draining the watersheds have undergone acidification and loss of most higher trophic levels of organisms. We are currently studying such a site in the Czech Republic which is showing signs of recovery from the damage incurred over the past half century. Since 1991 nitrogen and sulfur loads in atmospheric deposition have been reduced by almost half; however, recovery in the watersheds and lakes is not keeping pace with improvements in atmospheric quality. We are measuring rates of N cycling both in watershed sediments and in the lake itself to better understand the hysteresis in recovery of lake water quality.

Current Projects

• An integrated approach to understand relationships between shallow water benthic community structure and ecosystem function—funded by Strategic Environmental Research and Development Program (SERDP); DoD, DoE, EPA
• The role of coastal lagoons in removing or retarding nutrients during transport to the coastal ocean--funded by NSF LTER program under subcontract to the University of Virginia.

 
• Synergistic Interactions between Submerged Aquatic Vegetation and Clam Aquaculture--funded by Virginia SeaGrant.

Selected Publications

Anderson, I. C., McGlathery, K. J., and Tyler, A. C. 2003. Microbial mediation of ‘reactive nitrogen’ transformations in a temperate lagoon. Marine Ecology Progress Series. 246: 73-84.

Neubauer, S. C. and Anderson, I. C. 2003. Transport of dissolved inorganic carbon from a tidal freshwater marsh to the York River estuary. Limnology and Oceanography. 48(1): 299-307.

Aranibar, J. A., Anderson, I. C., Ringrose, S., and Macko, S. A. 2003. The importance of cyanobacterial crusts as a source of nitrogen to Southern Aftrican arid ecosystems – indicated by acetylene reduction and stable isotopes. J. Arid Environments. 54:345-358.

Aranibar, J.N., I. C. Anderson, A.L.F. Potgieter, S.A.Macko, H.H. Shugart and R. Sowry. 2003. Nutrient cycling response to fire frequency in the Kruger National Park (South Africa) indicated by stable isotopes. Isotopes in Environmental Health Studies. 39:141-158.

Tyler, A. C., K. J. McGlathery, and I. C. Anderson. 2003. Benthic algae control sediment-water column fluxes of organic and inorganic nitrogen compounds in a temperate lagoon. Limnology and Oceanography, 48:2125-2137.

McGlathery, K. J., K. Sundback, and I. C. Anderson. 2003. The importance of primary producers for benthic N and P cycling. In: The Influence of Primary Producers on Estuarine Nutrient Cycling, Nielsen, S. L., G. M. Banta, and M. F. Pedersen, (Eds.), Kluwer Academic Publishers. In press.

Neubauer, S. C., Anderson, I. C., Constantine, J. A., and Kuehl, S. A. 2001. Sediment deposition and accretion in a mid-Atlantic (U.S.A.) tidal freshwater marsh. Submitted to Estuarine Coastal and Shelf Science (in press).

Kopacek, J., Stuchlik, E., Vesely, J., Schaumburg, J. Anderson, I, Fott, J., Hejzlar, J., and Vrba, J. 2001. Hysteresis in reversal of Central European mountain lakes from atmospheric acidification. Submitted to Water, Air, and Soil Pollution (in press).

Miller, W. D., Neubauer, S. C., and Anderson, I. C.  2001. Effects of sea level induced disturbances on high salt marsh metabolism.  Estuaries.  24(3): 357-367.

Tobias, C. R., Canuel, E. A., and Anderson, I. C. 2001. Biogeochemical controls of nitrate reduction in groundwaters from a shallow coastal aquifer.  Limnol. Oceanogr. (in press).

Tobias, C. R., Harvey, J. W., and Anderson, I.C. 2001. Quantifying groundwater discharge through fringing wetlands to estuaries:  Seasonal variability, methods comparison, and implications for wetland-estuary exchange.  Limnol. Oceanogr. 46(3) 604-615.

Tobias, C. R., Anderson, I. C., Canuel E. A., and Macko, S. A. 2001. Nitrogen cycling through a fringing marsh - aquifer ecotone.  Marine Ecology Progress Series.  210: 25-39.

Tyler, A. C., McGlathery, K. J., and Anderson, I. C. 2001. Macroalgal mediation of dissolved organic nitrogen fluxes in a temperate coastal lagoon. Est. Coastal Shelf Sci. in press.

McGlathery, K. J., Anderson, I. C., and Tyler, A. C. 2001. Magnitude and variability of 
benthic  and pelagic metabolism in a temperate coastal lagoon. Marine Ecology Progress Series. In press. 

Anderson, I. C., Tobias, C. R., Macko, S. A., and Poth, M. A. 2000. Sources and sinks of nitrogen in acidified glacial lakes of the Bohemian Forest, Czech Republic.  Silva Gabreta. 4: 135-146.

 Neubauer, S. C., Miller, W. D., and Anderson, I. C.  2000. Carbon cycling in a tidal  freshwater marsh ecosystem: a gas flux study. Marine Ecology Progress Series.  199: 13-30.

Korontzi, S. K., Macko, S. A., Anderson, I. C. And Poth, M. A. 2000. Carbon and  nitrogen biogeochemical processes in a disturbed southern Californian forest ecosystem.  Global Biogeochemical Cycles.  14: 177-188.

Sin, Y., Wetzel, R. L., Anderson, I. C. 2000.  Seasonal variations of size fractionated phytoplankton along the salinity gradient in the York River Estuary, Virginia.  Journal of Plankton Research.  22: 1945-1960.

Bytnerowicz, A. Godzik, S., Poth, M., Anderson, I, Szdzuj, J, Tobias, C., Macko, S.,  Kubiesa, P.,Staszewski, T., and Fenn, M.  1999.  Chemical composition of air, soil, and  vegetation in forests of the Silesian Beskid mountains, Poland.  Water, Air, and Soil  Pollution.  116: 141-150.

 Sin, Y., Wetzel, R. L., Anderson, I. C. 1999. Spatial and temporal characteristics of phytoplankton and nutrients in the York River estuary: Analysis of long term data. Estuaries. 22:260-275.

Anderson, I. C., Tobias, C. R., Neikirk, B. B., and Wetzel, R. L.  1997.  Development of a process-based nitrogen mass balance model for a Virginia Spartina alterniflora  salt marsh: implications for net DIN flux. Mar. Ecol. Prog. Ser.  159:  13-27.

Anderson, I. C. and Poth, M. A.  1998. Controls on fluxes of trace gases from Brazilian Cerrado soils.  Journal of Environmental Quality, 27: 1117-1124.

Poth, M. A., Anderson, I. C., Miranda, H. S., Miranda, A.C., and Riggan, P. J. 1995. The magnitude and persistence of soil CH4, N2O, NO, and CO2 fluxes from burned tropical savanna in Brazil. Global Biogeochemical Cycles, 9:503-5l3.

Anderson, I. C., Poth, M. A., Homstead, J., and Burdige, D. J. l993. A Comparison of NO and N2O Production by the autotrophic nitrifier Nitrosomonas europaea and the heterotrophic nitrifier Alcaligenes faecalis. Appl. Environ. Microbiol. 59:3525-3533.

Current Students

• Frank Parker, Ph.D. Student
• Amber Kozak, Ph.D. Student (co-advisor Liz Canuel)

Past Students

• Jennifer Wu Stanhope, M.S. awarded 2003 (co-advisor Jim Perry)
• Tami Lunsford, M.S. awarded 2002.
• Scott Neubauer, Ph.D. awarded 2000 (co-advisor Richard Wetzel)
• Craig Tobias, Ph.D. awarded 1999, Nitrogen Dynamics at the Groundwater- Saltmarsh Interface (co-advisor Liz Canuel)
• David Miller, M.A. awarded 1998, The Effects of Increased  Inundation and Wrack Deposition on Photosynthesis and Respiration in a Virginia Salt  Marsh. (College of William and Mary)
• Yongsik Sin, Ph.D. awarded 1998, Phytoplankton Dynamics in the York River Estuary:  Field Studies,  Experimental Investigations, and Simulation Analysis (co-advisor Richard Wetzel)
• Betty Berry Neikirk, M.S. awarded 1996, Sediment-Water Interactions in a Coastal Spartina alterniflora Marsh (co-advisor Richard Wetzel)
• Juli Homstead, M.S. awarded 1991 (Old Dominion University)

• Lisa Kurian, Slippery Rock University, 2003
• Leandra Lockwood, Fairleigh Dickinson University, 2003
• Adriana Veloza, East Stroudsburg University, 2001
• Rachel Eichenlaub, Randolph Macon College, 1999 and 2000 (senior thesis)
• Jose Constantine, College of William and Mary, 1998 and 1999 (W&M senior thesis)
• Benani Sen, University of Virginia, 1997
• Peter Paik, College of William and Mary, 1995
• David Christian, University of Delaware, 1995
• Steven Roberts, East Carolina University, 1995
• Emily Saks, College of William and Mary, 1994

• Jessica Burshell, Summer intern 2003
• Melissa Diskein, Science Fair Project, Fall 2001, Fall 2002
• Neena Saha, First Program, Summer 2000
• Schuyler van Montfrans, York High School, Fall 2000
• Jessica Burton, Grafton HIgh School, Summer 1997 FIRST Program
• Jessica Burton, Governor’s School for Science and Technology (Fall/Winter, 1997)

Courses Taught

• MS 573:  Environmental Microbiology, with Howard Kator
• MS 575:  Aquatic Microbial Ecology, with Howard Kator
• MS 579:  Wetlands Ecology (Lecturer)
• MS 607:  Microbial Ecology (VIMS), with Howard Kator
• MS 698:  Aquatic Microbiology
• MS 698:  Biogeochemical and Physiological Processes in Intertidal and Subtidal Habitats, with Ken Moore
• MS 698:  Biogeochemical Processes in Wetlands
• MS 698:  Seminar in Biogeochemistry, with Liz Canuel, Jim Bauer, and Hugh Ducklow
• MS 698: Isotope Biogeochemistry, with Debbie Bronk

Professional Memberships

• Atlantic Estuarine Research Society