GLERL BIOGEOCHEMISTRY RESEARCH PROGRAM - 1996/1997

Great Lakes and coastal ecosystems are continually exposed to various stressers such as increased or decreased nutrient loads, human-induced changes in the carbon cycle and climate, and the introduction of toxic contaminants. The goal of this program is to help answer questions and address issues about the ecosystem's biogeochemical response to these stressers. This program contains ERL Research Task GLERL 07- NECOP, and GLERL 08 - Biogeochemistry in Lakes and Coastal Ecosystems. (The Task Leader for Tasks 07 and 08 is Brian Eadie, 734-741-2281, brian.eadie@noaa.gov)

Great Lakes and coastal ecosystems are continually subject to a series of stressers that may be transient, but repetitive in nature. These stressers are implicated in, or have the potential to cause, changes in the ecosystem they impact, by altering the processes that help determine and define the ecosystem's structure and function. Thus, the occurrence of such stressers gives rise to a need for scientific information and better understanding of the biogeochemical responses of ecosystems to increased or decreased nutrient loads, to human induced changes in the carbon cycle and climate, and to the introduction of toxic contaminants and their effects. This program focuses on the characteristics and rates of biogeochemical processes in ecosystems, the response to and alteration of these processes by anthropogenic stressers, and the record of biogeochemical alterations that may be contained in sediments.

RETURN to FY96/97 Accomplishments and Plans Cover Page

RETURN to Research Overview page

RETURN to GLERL home page

• Retrospective Analysis of Nutrient Enhanced Coastal Ocean Productivity in Sediments from the Louisiana Continental Shelf
  
  
• The Fate and Effects of Riverine (and shelf-derived) Dissolved Organic Nitrogen on Mississippi River Plume/Gulf Shelf Processes
  
  

• Environmental Radiotracers
  
  
• Carbon Biogeochemistry in Lakes and Coastal Ecosystems
  
  
• Nitrogen Dynamics

ERL Research Task: GLERL 07 - NECOP

The Nutrient Enhanced Coastal Ocean Productivity (NECOP) study was initiated by the Coastal Ocean Program of the National Oceanic and Atmospheric Administration (NOAA) in 1989 to address the effects of nutrient discharge on the coastal waters of the United States. The general NECOP hypothesis is that the addition of anthropogenic nutrients from sewage, agriculture, industrial sources, and suburban runoff have contributed to the development of eutrophication in coastal waters with significant impacts on water quality. The specific hypothesis addressed by this study was that increased nutrient input from the Mississippi River has led to increased productivity, resulting in the seasonal development of a large area of near-bottom hypoxia (low oxygen) and other undesirable consequences for the nearshore region (Mississippi River Plume and Inner Gulf Shelf (MRP/IGS) of the northern Gulf shelf. Work was conducted by a multi-institutional interdisciplinary team of scientists under a number of separate, but inter-related, projects, several of which were managed by GLERL scientists.

The NECOP (MRP/IGS) Study is essentially complete, although some follow-on activities, including additional work on the data, continues. Detailed information on the NECOP Study can be found at the NECOP Home Page (http://www.aoml.noaa.gov/ocd/necop/). Of the four original GLERL projects, all are complete, although one is being held open, but inactive during FY97, pending a determination of whether an overall NECOP synthesis document will be produced.

Retrospective Analysis of Nutrient Enhanced Coastal Ocean Productivity in Sediments from the Louisiana Continental Shelf

Principal Investigator: Brian Eadie (734-741-2281; brian.eadie@noaa.gov)

Collaborating Scientists: John Robbins, Margaret Lansing (GLERL); John Trefry, Simone Metz (Florida Institute of Technology); Pat Blackweller (University of Miami); Brent McKee (Louisiana Universities Marine Consortium); Karen von Damm (Oak Ridge National Labs)

The objectives of this project are to (1) identify areas in the MRP/IGS where sediments with coherent geochronologies of approximately 200 years can be collected, and (2) examine the selected cores for tracers of past water and ecosystem conditions (e.g., carbon, nitrogen, diatom frustules, and stable isotopes).

FY96 Progress and Accomplishments

Data synthesis and final documentation of data and results were completed.

FY97 Plans

This project is complete, but is being held open in FY97 pending determination of the desirability of developing an overall NECOP synthesis document.

Return to Project Index

Principal Investigator: Wayne Gardner (new address: University of Texas at Austin, Marine Science Institute, Port Aransas, Texas)

Collaborating Scientists: Brain Eadie, Margaret Lansing, Joann Cavaletto (GLERL); Ron Benner, Rainer Amon, J. Dean Pakulski (University of Texas).

The amount, composition, and biological lability of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) may be important factors affecting productivity in the MRP/IGS region. Specifically, we hypothesized that riverine DOC and DON supply a significant portion of total heterotrophic and autotrophic nutrients for growth in the MRP/GS system. The importance of dissolved organic matter (DOM) to microbial growth rates in the MRP/IGS is being evaluated by (1) characterizing the chemical and isotopic composition of DOC and DON in the river outflow and offshore stations, and (2) examining the biological reactivity of the DOC and DON. This project is being conducted in collaboration researchers at the University of Texas at Austin.

1996 Progress and Accomplishments

Remaining sample analyses were completed.

Documentation of the spatial nitrogen regeneration rates in the Gulf of Mexico Mississippi River plume and on the effects of light on them was completed and accepted for publication in Limnology and Oceanography. The results demonstrated that potential uptake and regeneration rates of ammonium were highest in mid-plume regions and that regeneration rates as well as potential uptake rates in surface waters were consistently higher under natural-light than under dark conditions in the Mississippi River plume. Explanations for this light/dark difference are (1) enhanced phytoplankton growth with associated grazing by microzooplankton in the light vs. dark, or (2) enhanced labile dissolved organic nitrogen release by phytoplankton in the light that in turn cause increased bacterial uptake and microbial food web activity. These data imply a close coupling between autotrophic and heterotrophic food web organisms and nutrient regeneration in surface waters.

Documentation of the remineralization rates of C,N,P, and Si for the Mississippi plume region in July, 1994 was completed and has been submitted to Continental Shelf Research. The results support all of the programs' previous work; remineralization rates are highest near the edge of the Mississippi River plume. Rates were so high that nitrification was measured in the water column, a rare event in large systems.

FY97 Plans

This project has been completed.

Return to Project Index

ERL Research Task: GLERL 08 - Biogeochemistry in Lakes and Coastal Ecosystems

This research task presently consists of two major projects: Environmental Radiotracers, and Carbon Biogeochemistry in Lakes and Coastal Ecosystems. The Environmental Radiotracers project represents over fifteen years of exploratory and developmental work on the use and application of radioisotopes for sediment geochronology, retrospective geochemistry, and for the study of fundamental lake/watershed transport processes in aquatic systems. It is, at any time, a composite of numerous on-going, terminating, and new-start sub-projects covering diverse ecosystems and an array of environmental problems that lend themselves to diagnosis and evaluation using the radiotracer and geochemical techniques developed under this project.

The Carbon Biogeochemistry project is focused on the carbon cycle in the Great Lakes and coastal ecosystems, and the application of stable isotopes (of carbon and nitrogen) to study natural biogeochemical processes that are important to the transport and flux of material in these systems, including within and up the food chain. It, also, is a composite of numerous, on-going, terminating, and new-start sub-projects covering diverse ecosystems and environmental problems.

These two major project themes (Environmental Radiotracers and Carbon Biogeochemistry) complement each other and one is often a contributor to the sub-projects of the other. Also incorporated into the Carbon Biogeochemistry project is work on the EPA-sponsored Lake Michigan Mass Balance Program (LMMB), which seeks to determine a mass balance of inputs and outputs of select contaminants for Lake Michigan and to predict their concentrations in the upper food web. The LMMB study is designed to answer questions posed in the amended Clean Air Act, and to assist environmental managers in developing and implementing the Lake Michigan Lakewide Management Plan.

Previously, the Biogeochemistry Research Task also included a significant effort related to nitrogen dynamics and supported a project of the same name. However, the Principal Investigator for that project took a job elsewhere, and the Nitrogen Dynamics project has been terminated.

Return to Project Index

Principal Investigator: John Robbins (734-741-2283; john.robbins@noaa.gov)

Collaborating Scientists: B. Eadie, P. Van Hoof, N. Morehead (GLERL ); R. Rood (University of Michigan - CILER); D. Edgington, J. Klump (University of Wisconsin - Milwaukee); M. Bothner, E. Callender, S. Colman, T. Fries, R. Halley, C. Holmes, A. Horowitz, H. Markowich, M. TenBrink, E. Shinn (USGS); P. Cook, (USEPA - Duluth); T. Fontaine, S. Newman, D. Rudnick (South Florida Water Management District); J. Graney, G. Keeler, E. Stoermer (University of Michigan); W. Kerfoot (Michigan Technological University); P. McCall (Case Western Reserve University); A. Mudroch (Canada Center for Inland Waters); K. Orlandini (Argonne National Laboratory); N. Pirrone (Institute for Atmospheric Pollution - Italy); K. Reddy (University of Florida - Gainesville); R. Rossmann (USEPA - Grosse Ile)

This research emphasizes the use of radiotracers to identify and model fundamental lake/watershed transport processes in diverse aquatic systems. Objectives of the project are to (1) identify principal transport mechanisms in aquatic systems and determine transport scales and rates, (2) investigate and quantify sediment depositional and geochemical processes, (3) develop geochronological information from sediment radionuclide profiles for paleolimnological studies, (4) determine and account for relationships between system loadings and sedimentary records of tracers, contaminants, and other constituents, and (5) apply techniques, insights, and models arising from radiotracer studies to specific problems of ecosystem dynamics, environmental contamination, and regional effects of climate change. There are many sub-projects within this project, many of which involve collaboration with investigators from other agencies.

FY96 Progress and Accomplishments

Florida Bay: collaborators at the University of Michigan School of Public Health completed analyses of (non-radioactive) lead in selected cores. Not only were lead and cesium-137 critical for establishing the validity of the primary radiochronological method but each provided important insights into the fate and storage of atmospherically-delivered contaminants to the system. Sediment profiles of these constituents showed that, following decrease or cessation of new inputs to the bay, concentrations of radiocesium and lead decreased on decadal time scales. The finding suggests that biogeochemical changes in the system in response to remediation strategies may be characterized by comparable recovery times.

Lake Baikal: In collaboration with the University of Wisconsin, Center for Great Lakes Studies and the U. S. Geological Survey (Woods Hole), we completed a study this year of the geochemistry of uranium and two of its long-lived decay products in Lake Baikal. This Lake, the deepest and one of the oldest in the world, has about 4000 meters of sediment holding valuable records of climate conditions going back at least 20 million years. Sediments of this lake receive unusually high and variable loadings of uranium from portions of its watershed in Mongolia. Our study showed that sedimentary profiles of uranium in Baikal reflect variations in the amount of water (and uranium) flowing into the lake during glacial and interglacial times, over the 250,000 year period of record. Uranium is evidently a surrogate for climate conditions in eastern Siberia and useful within the entire 20 million year sedimentary deposit. In addition, we showed that uranium provide through its progeny, its own internal chronometers which are useful back to about 1 million years. This work is a significant contribution to efforts to reconstruct the earth's climate history and evaluate impacts of global resource use on world and regional climates.

Lake Michigan Mass Balance Program: we completed an extensive, whole-lake sediment survey visiting over 100 sites and collecting high quality box cores from about 50 locations. In addition to acquiring, logging-in, freeze drying and distributing portions of appropriately prepared materials to collaborating organizations, GLERL has the primary responsibility for fallout cesium-137 analyses and the quantitative modeling of radionuclide profiles. Although most cesium-137 was introduced into the lake during the ten year period between 1956 and 1965, significant amounts remain in surface sediments today, 30 years later, as a result of sediment mixing and horizontal transport processes. Examination of radiocesium profiles in cores collected as part of this study show that the rates of decline of cesium activity in sediments with time vary widely over the lake ranging from less than a decade to more than 100 years. Study of the removal of nuclear fallout into archival sediments on the lake bottom helps to understand the long-term self-cleansing characteristics of the lake for other contaminants.

Florida Everglades: we continued our studies of soil cores from the Everglades to determine if radiocesium profiles measured during FY95 can reliably be used to determine soil accretion rates. Since radiocesium is known to be mobile in highly organic soils and is bound tightly by certain clay minerals, we analyzed selected cores for a large number of elements by neutron activation methods, to look for influence of mineral content of radiocesium profiles. We found that, in some cases, mineral composition can possibly alter profiles and the chronological inferences made from them. Since radiocesium dating has been the method most widely used to determine soil accretion rates and assess the impact of nutrient additions to ecological changes in the Everglades, the finding offers a caution for uncritical use of the method.

FY97 Plans

• Lake Erie Reference Site: Complete research on sedimentary reconstruction of historical conditions of anoxia.

• Legacy of Copper Mining in the Keweenaw Peninsula: Complete study of mine tailing signatures in the Keweenaw Waterway and Lake Superior.

• Lake Ladoga: Complete study of Chernobyl fallout and deposition of organic compounds in sediments of the lake.

• Florida Bay: Complete study of long-term integration of atmospherically loaded contaminants to sediments of the bay.

• Lake Michigan Mass Balance Study: Complete all radiometric analyses and start a systematic modeling effort to infer mass sedimentation rates , mixing scale-lengths and external integration time constants.

• Everglades: Collect additional cores from key research sites, measure radionuclides and stable elements in selected cores and model profiles in terms of diagenetic and other formalisms.

Principal Investigator: Brian Eadie (734-741-2281; brian.eadie@noaa.gov)

Collaborating Scientists: John Robbins, Margaret Lansing (GLERL); Wayne Gardner (formerly GLERL, now at University of Texas at Austin, Marine Science Institute, Port Aransas, Texas); Alena Mudroch, John Coakly, Fernando Rosa (National Water Research Institute - Canada); Christopher Parrish (University of Toronto); J. Val Klump, Jim Waples (University of Wisconsin); Philip Meyers, Gabrielle Tanzer, Eileen Ho, Casey Lohman (University of Michigan); Steven Eisenreich (Rutgers University); Jeff Jerramiason (University of Minnesota); Joel Baker (University of Maryland); Roy Spalding, Kahalail Hassan (University of Nebraska); Nathanial Ostrum, Joel Henry (Michigan State University); James Cotner (Texas A&M University), Ronald Benner, Dean Pakulski (University of Texas); John Trefry (Florida Institute of Technology), Brent McKee (Louisiana Universities Marine Consortium), Ted Callender, Sharon Fitzgerald (USGS)

This project focuses on processes regulating the major biogeochemical cycles and fluxes, with an emphasis on carbon. Carbon is central to many of the perceived issues related to anthropogenic impacts on our environment. For example, in addition to potentially altering global and local climates, increasing atmospheric CO₂ will have a major impact on the carbon geochemistry of the Great Lakes; the reduction and eventual cessation of annual CaCO₃ precipitation with consequent impacts on trace contaminant removal, primary productivity and zooplankton grazing. Our understanding of the parameters controlling this process are primitive and will be the focus for part of this program.

The overall residence time of carbon or the efficiency with which it is used in its passage from its source to the lake to its removal via burial, outflow or gas exchange is unknown at this time for any of the Great Lakes. This is a valuable concept in attempting to understand the perturbations that these systems are experiencing. Objective interpretation of ecosystem changes at the species or even community level brought about by contaminants or climate changes may not be feasible due to the fact that the lakes ecology is continuously being perturbed by invaders as well as nutrient and fishery management. The mean residence time of a carbon (and other biogeochemically critical elements) could be a more meaningful measure (or would at least be valuable supplementary information) of the structure/function of the ecosystem than monitoring of state variables. This requires the development and calibration of a carbon cycling model for each of the lakes (eventually coupled). Such a model was produced in the mid-1970s for Lake Ontario for the International Field Year of the Great Lakes (IFYGL) program, and it showed that even with the large IFYGL data set, poorly estimated values for gas exchange resulted in large uncertainties in interpretation. We now have a means to severely constrain such a model, using measurements of the stable isotopes of carbon and nitrogen. Our ability to use stable isotope tracers (¹²C and ¹³C) in sample matrices allows us to double the amount of information going into the synthesis. Use of ¹⁴C (measured off-site) will provide an independent set of carbon data for verification. Studies are currently underway in several of the Great Lakes, major embayments, and other lakes.

1996 Progress and Accomplishments

An additional set of samples were collected from Green Bay; analyses of the isotopic composition of all of the samples collected in 1995 and the additional set collected in 1996 were completed. Therefore, all samples collected through 1996 under this project have been analyzed. Presentations were made at the American Geophysical Union (AGU) meeting and the American Society for Limnology and Oceanography (ASLO) describing our results in this (Green Bay) project. Over 2000 measurements of pCO₂ have shown a concentration range of over a factor of 10 in the bay and a del C-13 gradient for inorganic carbon of over 7‰ along the major axis of the bay. Major seasonal changes were also observed and interpretation is underway. These changes imply a very active system and are reflected in the isotopic composition of the food web.

Analyses of mass- and carbon-fluxes from all 15 sediment traps collected over the summer of 1995 from Yellowstone Lake were completed. The sequencing traps deployed in September were retrieved in August; one trap worked and the second failed after the first period of collection.

Three sets of Great Lakes sediment trap information that need reorganization have all been reprogrammed into the same format. Before we can concatenate them, we must create labels and renumber all 2000+ samples bottles in our archive.

A detailed description of the organic geochemistry of a Lake Erie core was presented at the Geological Society of America meeting and was also published as a Master's Thesis in Geology at Michigan State University (author: Joel Henry). The samples that he fractionated were analyzed by gas chromatography and isotope-ratio mass spectrometry to examine the use of compound-specific stable isotopic information for reconstructing paleoecology. Stable isotopes of bulk organic matter have proven useful as an indicator of primary production, tracing of sources, etc. The use of specific compounds are similarly useful in retrospective studies. Recent technological advances have combined these two tracer techniques; their power and value are being explored.

Documentation of the results of our analyses of trap materials in Lake Saimma, Finland was completed. The traps were deployed in a transect away from Finland's major wood pulping plant and stable isotopes and organic phenolics were analyzed. Results showed that both were excellent tracers of the plume of organic waste generated by the plant.

1997 Plans

• Weigh subsamples of all LMMB trap samples for the analysis of mercury, one of the LMMB Programs target contaminants.

• Complete LMMB project mass flux, C and N data base; deliver it to EPA and achieve certification for model applications.

• Continue as member of the LMMB Technical Coordinating Committee to advise EPA on overall program progress and synthesis.

• Attempt to retrieve the trap near the mouth of Green Bay; these samples are the best measure that the LMMB program made for estimating PCB transfer from Green Bay into Lake Michigan.

• Document the results and interpretations of our LMMB efforts.

• Complete documentation of the carbon flux measurements made in Green Bay.

• Complete the analyses of trap samples and begin interpretation and documentation of mass and nutrient fluxes in Yellowstone Lake as an input to lake management decisions.

• Complete the reorganization of approximately 2000 sediment trap samples in our archive and the associated data base and publish on the web for community availability.

• Begin documentation of a synthesis of all Great Lakes sediment trap work over the past 15 years.

• Analyze the Lake Michigan Mass Balance (LMMB) surface sediment samples for carbon and nitrogen isotopes in order to assist interpretation of sediment transport modeling.

• Analyze LMMB food web samples collected by the NBS for stable isotopic composition; complimentary to their contaminant analyses and useful in interpretation of bioaccumulation.

Principal Investigator: Wayne Gardner (new address: University of Texas at Austin, Marine Science Institute, Port Aransas, Texas)

Nitrogen occurs in all living organisms and is an important element in aquatic ecosystems. Nitrogen is dynamic in all aquatic ecosystems and occurs in several forms in the sediments, water, and the atmosphere. Nitrogen transformations are often biologically mediated in aquatic ecosystems. The forms, fluxes, and transformation rates of nitrogen compounds therefore reflect organism and ecosystem dynamics in freshwater and marine environments.

Although nitrogen biogeochemistry is a crucial part of aquatic ecosystem dynamics, our understanding of nitrogen cycling in fresh water and marine systems is incomplete, in part because methodology is often inadequate to efficiently determine nitrogen forms and transformation rates. In contrast to carbon and phosphorus, nitrogen does not have radioactive forms (with sufficient half lives) that can be used for tracer studies. Nitrogen transformations are usually similar in fresh and salt water environments, but some important differences have been observed. Understanding the reason(s) for such differences may provide a basis for management practices that would minimize the effects of nitrogen enrichment in marine coastal waters. Comparative studies of nitrogen dynamics in fresh and salt water systems will provide insights on similarities and differences between the two systems and should improve our understanding of nitrogen dynamics in both systems.

1996 Progress and Accomplishments

Florida Bay Research: Data from previous field observations and experiments in Florida Bay were processed to consider the effects of external loading and internal cycling of nutrients on the composition, distribution and quantitative characteristics of the lower food web. Nitrogen cycling rates in the water column were compared to nitrogen fluxes from the sediments at four stations representing different ecological conditions in Florida Bay. On an areal basis, water-column regeneration rates were lower than sediment-water fluxes at most stations, but the reverse was true at one eutrophic station (near Rankin Key) that was characterized by a bloom of the planktonic cyanobacterium, Synechococcus. Microbial food web organism abundances showed similar trends at the different stations; abundances were high in the sediments relative to the water column at most stations but high in the water column relative to the sediments at the station characterized by high levels of Synechococcus. Overall, these results demonstrate that the presence of nutrient-induced Synechococcus blooms, with corresponding reduced abundances of seagrasses, tend to cause a shift of lower food web dynamics from the sediments to the water column.

Nitrogen Cycling Rates in Lake Maracaibo, Venezuela: Nitrogen cycling rates were examined in Lake Maracaibo, a large, warm (30-32^oC), hypereutrophic, oil-polluted, estuarine lake in northern Venezuela, by conducting isotope-dilution experiments with ¹⁵NH4+ using shipboard incubators in September 1995. Nitrogen is an important limiting nutrient in Lake Maracaibo where phosphorus loadings are high. Chlorophyll levels ranged from 2.5 to 22 mg L^-1, with the highest levels observed in near-surface (1-m deep) water affected by sewage discharge. Nitrogen cycling rates were high (often higher than rates previously reported for other regions) especially in regions enriched with sewage outflows. Potential uptake rates were highest (up to 8 mM h^-1) in near-surface waters at the high-chlorophyll station. Uptake rates were strongly inhibited by light both in quartz tubes and in clear-polystyrene bottles shaded with a single layer of window-screen. Ammonium regeneration rates ranged from near-detection to 2 mM h^-1 and were affected less predictably by light differences than were potential-uptake rates. Although it was measurable, N remineralization by sun-light (UV plus visible) oxidation appeared to be low relative to biological turnover rates in these waters. These results constitute the first measurements of nitrogen recycling rates in Lake Maracaibo.

Old Women Creek: Results of previous work in Old Woman Creek on nitrification were written up as part of a manuscript submitted to Aquatic Microbial Ecology.

1997 Plans

This project has been terminated, as the PI has moved to a position with the University of Texas.

Last updated July 10, 2002 mbl

Home | Research | Data | Products & Services | Outreach | About GLERL | News & Events
Privacy Policy | Disclaimer | Accessibility Statement | GLERL only | Contact Us

GLERL 4840 S. State Rd., Ann Arbor, MI 48108-9719     (734) 741-2235
Lake Michigan Field Station, 1431 Beach St., Muskegon, MI 49441-1098     (231) 759-1560