Here, we provide a brief description of current or recently expired research projects in which Drs. Kemp and Murray have been engaged along with their graduate students. This research involves the study of ecosystem processes in shallow estuarine habitats (e.g., Day et al. 1989). We also include a selected list of publications representative of the results of this research. Abstracts from these papers are also provided. Finally, to help interested students gain perspective on the kinds of career tracks enjoyed by our graduate students, we provide a list of current positions and addresses for students graduated from this group.

1)  Title: Trophic interactions in estuarine systems (TIES).   PI's: W. Boynton, W. Boicourt, E. Houde, W. M. Kemp, M. Roman. Students (this group): Erik Smith. Jim Hagy, Marilyn Mayer Support: National Science Foundation, (LMER Initiative).  Duration: Sep 1994 - Aug 2000.

This project is the second in a sequence of multi-investigator studies supported by the NSF Land Margin Ecosystem Research initiative to study Chesapeake Bay ecosystem. The duration of the two LMER projects spanned over a decade, from 1990 to 2000. The first of these projects, which was named PROTEUS and coordinated by our group, focused on primary production and nutrient biogeochemistry at the land-sea interface. It generated numerous publications (see below) Kemp et al. 1990; 1992; Kemp and Bartleson 1991; Bartleson and Kemp 1991; Smith and Kemp 1995; Boynton et al. 1995; Mayer et al. 1995). The second of these projects, coordinated by W. Boynton, investigated questions related to how physical structures and variability stimulate primary and secondary production (see below) Kemp et al. 1997; Kemp et al. 1999; Boynton and Kemp 2000; Smith and Kemp 2001; Kemp et al. 2001).
 

2)  Title: MEERC: Multi-scale Experimental Ecosystem Research Center. PI's: V. Kennedy, V. (Director), W. M. Kemp and 17 others.   Students (this group): John Petersen, Chung-Chi Chen, Brian Sturgis. Support: U.S. EPA Center for Excellence in Environmental Research.   Duration: May 1992-Dec 2001.

This is a 10-year research project, which has focused on a range of questions related to the spatial and temporal scales of coastal ecosystems. For example, how does the nature of a coastal ecosystem depend on its size and age? What are the inherent differences between large bays and smaller lagoons? How does the behavior of small experimental ecosystems differ from that in their larger natural counterparts, particularly in terms of responses to perturbations? How can we, therefore, extrapolate results from our experiments to conditions in nature?

This project has involved a range of experiments with experimental ecosystems (mesocosms) of various sizes, shapes and habitats. We have run a series of experiments in our "pelagic-benthic" (PB = water plus sediments) mesocosms examining how variations in depth, width, volume, water residence time, and mixing rate affect ecosystem behavior under various light and nutrient conditions and different degrees of food-web complexity. These studies have contributed to an expanded understanding of how scale effects experimental results and rules for extrapolating to nature (e.g., Costanza et al. 1993; Chen et al. 1997; 2000; Petersen et al. 1997; 1998;1999; Murray et al. 2000; Kemp et al. 2001; Gardner et al. 2001). We have also conducted a range of experiments using shallow mesocosms with submerged and emergent vascular plants (seagrasses and marsh plants). Here we have examined effects of nutrient additions in various forms, flow-routes and frequencies. We have also studies how responses of experimental ecosystems
 

3)  Title: Water quality and living resources in Chesapeake Bay: Modeling potential responses to nutrient loading reductions. PI's: W. M. Kemp and W. R. Boynton.  Students (this group): Maureen Brooks, Jim Hagy. Jude Apple. Support: UMCES Integration and Application Network (IAN). Duration: Aug 2000-Dec 2001.

This research project involves the synthesis of existing data collected to describe water quality, fish and invertebrate population abundances and fisheries harvest in Chesapeake Bay. These data are analyzed and modeled to better understand the relationship between nutrient enrichment and the production and harvest of fish and invertebrate resources. Modeling studies have demonstrated that increasing nutrient loading to coastal ecosystems results in non-linear change in trophic efficiency (ratio of fish production to plant production). At low nutrient levels, increased inputs tend to enhance both primary production and fish growth. At higher loading rates, however, the trophic efficiency declines as an increasingly larger proportion of the primary production goes to support growth of bacteria rather than fish.  We also show that growth of benthic invertebrates and bottom-feeding fish is limited more by habitat availability than by food. Benthic habitat is lost each summer with seasonal depletion of oxygen from bottom waters in the middle of the Bay. Thus, management plans to decrease nutrient loading to the Bay will result in increase growth of benthic animals in this region by increasing the availability of habitat. This project represents "seed" funding to initiate long-term support for these objectives, but one paper from this work is currently in press (Kemp et al. 2001).
 

4)  Title: Seagrass-nutrient interactions: Role of spatial pattern.  PI's: W. M. Kemp and L. Murray. Students (this group): Kris Schulte, John Melton. Support: NOAA, MD Sea Grant. Duration: Feb 2000 - Feb 2002.

This research group has been involved in studies of seagrasses and related submerged aquatic vegetation (SAV) for more than two decades. Scientific investigations have been situated primarily in Chesapeake Bay, but we have also done considerable work along the Mexican coast of the Yucatan Peninsula, in Danish coastal waters and in Florida Bay. Many students have been involved in this work, and it has focused on various aspects of seagrass ecosystems from fish (Lubbers et al. 1990) to plant physiology and eutrophication studies (e.g., Neundorfer and Kemp 1993) to biogeochemistry of plant-sediment interactions (e.g., Caffrey and Kemp 1990; 1991; 1992).

This project represents a bridge from the earlier seagrass studies to our current focus on questions of spatial scale. Here we are investigating how size, density and patchiness of seagrass beds affect the ability of these plants to survive and grow under changing water quality conditions. The study involves a range of field surveys and transplanting experiments, and use of GIS methods for analysis of aerial photographs showing spatial distributions of seagrass beds. We have proposed to extend these studies to include a focus on how spatial distribution of beds affects plant-sediment interactions.  

5)  Title: Nitrogen and phosphorus biogeochemistry of Florida Bay sediments.  PI's: J. C. Cornwell and W. M. Kemp. Students (this group): Jessica Davis. Support: NOAA, Coastal Ocean Program Duration: Aug 2000-Sep 2002.

After spending a 10-month sabbatical in 1998 studying relationships between seagrasses and water quality in South Florida estuaries, we have established a continuing research effort on related topics with two small projects in Florida Bay. The first of these, which is in its second phase (the first year was funded by U.S EPA), focuses on sediment biogeochemistry and seagrass-sediment interactions. We are measuring how seagrasses and benthic microalgae affect cycling of nitrogen and phosphorus. Much of the interest in Florida Bay stems from the well-documented seagrass die-back that began near the beginning of the last decade and persists to the present. Thus, the design of this study uses a comparative approach to contrast stations along gradients of nutrients, salinity and plant health. We are applying a newly developed method to measure denitrification and nitrogen fixation at these sites (Cornwell et al. 1999) and we modified and applied a suite of methods developed earlier in Chesapeake Bay studies (Caffrey and Kemp 1990; 1992).  

6)  Title: Simulation model of seagrass communities in Florida Bay.PI's: C. Madden and W. M. Kemp. Students (this group): Jessica Davis. Support: U. S. Geological Survey. Duration: Jun 2000-Jul 2002.

During our sabbatical we initiated development of a numerical model of Florida Bay seagrass communities in relation to climatological and biogeochemical processes.  The basic structure of this model is derived from an earlier study in Chesapeake Bay (Madden and Kemp 1996), with substantial changes needed to match differences in plant physiology and biogeochemistry in Florida Bay.  This model is being used to integrated the expanding information on seagrasses and environmental conditions in Florida Bay to better understand spatial and temporal patterns of plant distribution and the die-back phenomenon. Initial simulation studies have helped to identify research questions and formulate hypotheses related to seagrass health and nutrient cycling in Florida Bay.

7) Title: Evaluating effects of anthropogenic nutrient loading on microbial community metabolism. PI's: P. del Giorgio and J. Apple. Students (this group): Jude Apple. Support: NOAA/NERR (National Estuarine Research Reserve). Duration:Aug 2000-Aug 2003.

Our research aims to identify the relationship between agricultural land use, ambient nutrient concentrations, and associated responses of adjacent estuarine bacterioplankton communities. This work focuses on factors regulating metabolic processes of the heterotrophic bacterioplankton communities (i.e. production, respiration, and growth efficiency). Our objective is to develop a better understanding of how the eutrophication process alters the role of heterotrophic bacterioplankton communities in organic carbon flow of coastal ecosystems. This research is being conducted at the NERR site in Monie Bay, a sub-estuary of Tangiers Sound and Chesapeake Bay. This system includes an open bay and three tidally-influenced creeks, each with different degrees of agricultural activities in their respective watersheds. As such, Monie Bay provides and ideal setting for exploring ecosystem level effects of agricultural land use on estuarine systems.

Selected Recent Publications of Estuarine Ecosystem Processes Group (Kemp et al):

Research Articles

Kemp, W. M., P. A. Sampou, J. M. Caffrey, M. Mayer, K. Henriksen and W. R. Boynton. 1990. Ammonium recycling versus denitrification in Chesapeake Bay sediments. Limnol. Oceanogr. 35: 1545-1563.

Lubbers, L., W. R, Boynton and W. M. Kemp. 1990. Variations in structure of estuarine fish communities in relation to abundance of submersed vascular plants. Mar. Ecol. Prog. Ser. 65: 1-14.

Caffrey, J. M. and W. M. Kemp. 1990. Nitrogen cycling in sediments with estuarine populations of Potamogeton perfoliatus  L. and Zostera marina. L. Mar. Ecol. Prog. Ser. 66: 147-160.

Caffrey, J. M. and W. M. Kemp. 1991. Seasonal and spatial patterns of oxygen production, respiration and root-rhizome release in Potamogeton perfoliatus  L. and Zostera marina. L. Aquat. Bot. 40: 109-128.

Kemp, W. M. and R. D. Bartleson. 1991. Preliminary ecosystem simulations of estuarine plankton-benthic interactions: The benthic submodel. pp. 253-264, In: J. A. Mihursky and A. Chaney (eds.) New perspectives in the Chesapeake Bay system. Chesapeake Res. Consort. Publ., Solomons, MD.

Bartleson, R. D. and Kemp, W. M. 1991. Preliminary ecosystem simulations of estuarine plankton-benthic interactions: The planktonic submodel. pp. 243-252,  In: J. A. Mihursky and A. Chaney (eds.) New perspectives in the Chesapeake Bay system. Chesapeake Res. Consort. Publ., Solomons, MD.

Kemp, W.M., P.A. Sampou, J. Garber, J. Tuttle, W.R. Boynton.  1992. Seasonal depletion of oxygen from bottom waters of Chesapeake Bay: Relative roles of benthic and planktonic respiration and physical exchange processes. Mar. Ecol. Progr. Ser. 85: 137-152.

Caffrey, J. M. and W. M. Kemp. 1992. Influence of the submersed plant, Potamogeton perfoliatus L., on nitrogen cycling in estuarine sediments: Use of 15N techniques. Limnol. Oceanogr. 37: 1483-1495.

Neundorfer, J. V. and W. M. Kemp. 1993. Nitrogen versus phosphorus enrichment of brackish waters: Response of Potomogeton perfoliatus and its associated algal communities. Mar. Ecol. Prog. Ser. 94: 71-82.

Costanza, R., W. M. Kemp, and W. R. Boynton. 1993. Predictability, scale and biodiversity in coastal and estuarine ecosystems: Implications for management. Ambio. 22: 88-96.

Boynton, W.R., J.H. Garber, R. Summers and W.M. Kemp.  1995.  Input, transformations and transport of nitrogen and phosphorus in Chesapeake Bay and selected tributaries. Estuaries 18: 285-314.

Smith, E. M. and W. M. Kemp. 1995. Seasonal and regional variations in plankton community production and respiration for Chesapeake Bay.  Mar. Ecol. Prog. Ser. 116: 217-231

Mayer, M. S., L. Schaffner, and W. M. Kemp. 1995. Nitrification potentials  of benthic macrofaunal tubes and burrow walls: Effects of sediment NH4+ and animal irrigation behavior. Mar. Ecol. Prog. Ser. 121: 157-169.

Madden, C. J. and W. M. Kemp. 1996. Ecosystem model of an estuarine submersed plant community: Calibration and simulation of eutrophication responses.  Estuaries. 19 (2B): 457-474.

Petersen, J., C.-C. Chen and W. M. Kemp. 1997. Scaling aquatic primary productivity: Experiments under nutrient and light limited conditions. Ecology 78: 2326-2338.

Kemp, W. M., E. M. Smith, M. Marvin-DiPasquale and W. R. Boynton. 1997. Organic carbon-balance and net ecosystem metabolism in Chesapeake Bay. Mar. Ecol. Prog. Ser. 150: 229-248.

Chen, C.-C., J. Petersen and W. M. Kemp. 1997. Spatial and temporal scaling of periphyton growth on walls of estuarine mesocosms. Mar Ecol Prog Ser 155: 1- 15.

Petersen, J. E., L. Sanford and W. M. Kemp. 1998. Coastal plankton responses to turbulent mixing in experimental ecosystems. Mar. Ecol. Prog. Ser. 171: 23-41.

Kemp, W. M., S. Puskaric, A. Faganeli, E. Smith and W. Boynton. 1999. Pelagic- benthic coupling and nutrient cycling, pp. 295-339 In: T. Malone, A. Malej, L. Harding, N. Smodlaka and R. Turner (eds). Ecosystems at the land-sea margin: Drainage basin to coastal sea. Amer. Geophys. Union Publ., Washington, DC.

Petersen, J. E., J. Cornwell and W. M. Kemp. 1999. Implicit scaling in the design of enclosed experimental aquatic ecosystems. Oikos 85: 3-18.

Cornwell, J. C., W. M. Kemp and T. M. Kana. 1999. Denitrification in coastal ecosystems: Environmental controls and aspects of spatial and temporal scaling. Aquat. Ecol. 33: 41-54.

Boynton, W. R. and W. M. Kemp. 2000. Influence of river flow and nutrient loading on selected ecosystem processes and properties in Chesapeake Bay. pp. 269-298, In: J. Hobbie (ed). Estuarine science: A synthetic approach to research and practice. Island Press, Washington, DC.

Murray, L., R. B. Sturgis, R. Bartleson, W. Severn and W. M Kemp. 2000.  Scaling submersed plant community responses to experimental nutrient enrichment, pp. 241-258, In: S. Bortone (ed.)  Seagrasses: Monitoring, ecology, physiology, and management.  CRC Publ., Boca Raton, FL .

Chen, C. C., J. E. Petersen, and W. M. Kemp. 2000. Nutrient uptake in experimental ecosystems: Effects of physical scale on partitioning of rates. Mar. Ecol. Prog. Ser. 200: 103-116.

Smith, E. M. and W. M. Kemp. 2001. Size-structure and the production/respiration balance in a coastal plankton community. Limnol. Oceanogr. 46: 473-485.

Kemp, W. M., M. T. Brooks and R. R. Hood. 2001. Nutrient enrichment, habitat variability and trophic transfer efficiency in simple models of pelagic ecosystems. Mar. Ecol. Prog. Ser. (In press).

Books:

Day, J.W., C.A.S. Hall, W.M. Kemp and A. Yanez-Arancibia. 1989. Estuarine
ecology.  John Wiley and Sons, New York.

Gardner, R., W. M. Kemp, J. Petersen and V. Kennedy (eds.). 2001. Scaling relations
in experimental ecology. Columbia University Press, New York.

Current Positions of Former Graduate Students in Kemp et al. Group

Masters Students

Jeffrey J. Cunningham: MS, 1979, Current position: Research Scientist, Univ. Maryland, Dept. of Agric. and Resource Economics, College Park.

Marlon R. Lewis, MS, 1980, Current position: Professor, Dalhousie Univ., Halifax, NS, Canada.

Mark C. Jenkins, MS: 1981, Current position: Research Scientist, National Institutes for Health, Bethesda, MD.

William J. Goldsborough, MS, 1983, Current position: Fisheries Manager, Chesapeake Bay Foundation, Annapolis, MD.

Kenneth W. Staver, MS, 1984, Current position: Asst. Res. Professor, Univ. of Maryland, Wye Research Institute, Queen Anne, MD.

Janet V. Neundorfer, MS, 1990, Current position: US Army Corps of Engg, Baltimore.

William Kuhn, MS, 1992, Current position: Environmental Consultant, Santa Barbara, CA.

Catherine (Stokes) Wazniak, MS, 1996, Current position: Environmental Biologist, Maryland Department of Natural Resources, Annapolis, MD.

Doctorate Students

Jane M. Caffrey, PhD, 1989, Current position: Associate Research Professor, Univ. California, Santa Barbara, CA.

Marilyn Mayer, PhD, 1992, Current position: Associate Professor, St. Lawrence Univ., Lawrence, New York.

Kenneth Moore, PhD, 1997, Current position: Assoc. Res. Professor, Virginia Institute of Marine Science, College of William and Mary, Gloucester Pt., VA.

John E. Petersen, PhD, 1998, Current position: Assistant Professor, Oberlin University, Oberlin, OH.

Chung-Chi Chen, PhD, 1998, Current position: Research Scientist, Center for Marine Science, Taipei, Taiwan.

Erik M. Smith, PhD, 2000 (MS‹1992), Current position: Postdoctoral Fellow, University of Quebec, Montreal, Canada.