PROGRAM TITLE: Ecosytem Dynamics - FY 1996/1997

This research focuses primarily on key components of the Great Lakes lower foodweb and the links between physical, chemical, and biological processes that impact important processes in ecosystem function. Although long-term trends in key components are examined, life history studies and process research are emphasized so that GLERL's expertise can be applied to problems in a variety of ecosystems that are geographically and biologically diverse.

Current Ecosystem Dynamics Program Main Page

This program includes activities under two ERL Research Tasks: GLERL 09 - Ecosystem Dynamics Research and GLERL - 12 Episodic Events (Leader, Tasks 9 and 12: Gary Fahnenstiel, 231-759-7824, gary.fahnenstiel@noaa.gov).

The Great Lakes and nearshore ocean waters are major national resources used for a wide range of activities: industrial and municipal water supplies, shipping, fishing (sport and commercial), municipal and industrial discharge, boating, and other forms of recreation. Water quality and the value of the biological resources in these systems is directly related to the health and abundances of the organisms and their interactions with the physical and chemical aspects of the ecosystem. Therefore, to protect, preserve, and restore these systems, it is essential to understand the community structure and function of organisms at all trophic levels, and their interactions within the ecosystem. GLERL conducts ecosystem research in both the Great Lakes and nearshore ocean environments.

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GLERL 09 - Ecosystem Dynamics Research

• Research Monitoring of the Lake Michigan Ecosystem
• Production of the Great Lakes Amphipod Diporeia spp. in Southeastern Lake Michigan (New Project, FY97)
• Temporal and spatial variation in lipid concentrations of the mayfly Hexagenia (New Project, FY97)
• The Role of Sensory Physiology and Behavior in the Remote Detection of Large Particles by Calanoid Copepods

GLERL - 12 Episodic Events

• High Frequency Events
  
• Event Sampling in the Spring Plume of Southern Lake Michigan

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ERL Research Task: GLERL 09 - Ecosystem Dynamics Research

GLERL has traditionally focused its ecosystem and nutrient dynamics research on the lower trophic levels of the Great Lakes. The combination of GLERL's lower food web studies with the activities and data of the U.S. Fish and Wildlife Service and the USGS/Biological Resources Division/Great Lakes Science Center, which focus on the upper food web (fish), provides essentially complete coverage of the entire Great Lakes pelagic (i.e., water column) fisheries ecosystem. Such studies and the resulting information have important applications and uses for fish stocking decisions and for computer-based model analyses of proposed fishery management actions affecting the valuable sport fisheries on the Great Lakes, which are valued at several billion dollars per year.

Research Monitoring of the Lake Michigan Ecosystem

Principal Investigator: Gary Fahnenstiel (231-759-7824; gary.fahnenstiel@noaa.gov).

Collaborating Scientists: Henry Vanderploeg (GLERL)

Lake Michigan is the only Laurentian Great Lake that lies entirely within US jurisdiction. It has a world class fishery valued at over $300 million per year and serves as the source of drinking water to over 5 million Americans. Lake Michigan is also one of the most highly "managed" ecosystems in the world. In order to be effective, management decisions must be based on sound scientific data, and for this reason, GLERL has maintained a long-term monitoring program for Lake Michigan the past 12 years. In 1994 it was revised and upgraded to improve the scientific information that is collected. The primary objective of this project is to monitor and assess the health of the Lake Michigan ecosystem by examining long-term food web dynamics and indicators of water quality in order to understand and predict natural and anthropogenic causes of variability. Also, this program will use state-of-art research techniques to develop and assess the use of new indicators and monitoring tools.

The data from this project are used for GLERL's research on the condition of and trends in Lake Michigan's ecosystem, and also for a study in collaboration with Lake Michigan's perch fishermen to investigate possible food-web-based causes of a decline in Lake Michigan's perch population. As a result of establishing a scientific presence at GLERL's Lake Michigan Field Station in Muskegon, Michigan, in 1993, a Lakewatch component was added to this project. Lakewatch is a research/monitoring activity that engenders substantial citizen involvement in monitoring, learning about, and participating in decisions affecting local aquatic resources. GLERL provides technical assistance, sampling equipment, and sample processing and analytical support to local citizen volunteers, who implement a local lake monitoring program that includes regular sampling and analyses for specified water quality parameters. Lakewatch activities were initiated in Muskegon Lake and White Lake in 1995.

FY96 Progress and Accomplishments

The historical monitoring program was revised again this year. We added an intensive nearshore monitoring program in order to examine the impacts of non-indigenous species on Lake Michigan. Twenty nearshore stations were sampled on a monthly basis from April through October. These stations were located on transects from Grand Haven north to White Lake. On each transects, five stations were sampled in 10m, 20m, 30,m 40m, and 60 m of water. The parameters sampled included: temperature, Secchi disk transparency, chlorophyll fluorescence, extracted chlorophyll, light transmittance, conductivity, zooplankton abundance and composition including Bythotrephes, phytoplankton abundance and composition, and DCMU-induced fluorescence and productivity. This new nearshore monitoring program was added to the existing Lake Michigan monitoring program in order to thoroughly examine the limnology of central Lake Michigan.

In support of the entire Lake Michigan monitoring program we have collected and processed over 1000 chlorophyll samples, 300 total phosphorus samples, 100 particulate organic carbon, 500 phytoplankton samples, and 200 zooplankton samples.

We have to continued analyzing the results from a 3 year study designed to compare the structure and productivity of the lower food webs across the Great Lakes. Under this study thousands of samples from all five Great Lakes have been collected and analyzed. Microscopic counts were made for phototrophic picoplankton, heterotrophic bacteria, phytoplankton, protozoans, ciliates, rotifers and zooplankton. We have documented unprecedented changes in the lower food web of Lakes Ontario and Erie. Nutrient concentrations in the lower lakes are approaching those in the upper lakes and the biological community appears to be in transition, as present communities are very different from those previously documented. Modeling of the productivity data has begun and large changes in productivity of the lower lakes have been noted. In contrast to the lower lakes, the upper lakes exhibit very small to nonexistent changes when compared to previous reports.

The first year of the Lakewatch programs for Muskegon and White Lakes were completed. During this year we also started a Lakewatch program in Pigeon Lake (Port Sheldon).

FY97 Plans

• Continue standard monitoring program, including he organisms Mysis and Bythotrephes.
• Identify and count plankton samples collected in 1994-1996 and start analyzing data.
• Organize data from the years 1983-1992 (from the old monitoring program) and do plankton counts and measurements necessary to bring results to a publishable form.
• Start combining results from 1983-1992 and 1994-1996 to develop a manuscript describing changes in the plankton and underlying causes during this period.
• Develop, test, and deploy GLERL's plankton survey system--consisting of optical plankton counter, CTD, and fluorometer mounted on a V-fin--for towing behind our large and small research vessels to survey plankton and relevant physical variables along transects from shore to our offshore stations.

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Production of the Great Lakes Amphipod Diporeia spp. in Southeastern Lake Michigan (New Project, FY97)

Principal Investigator: Michael Quigley (734-741-2149; Michael.A.Quigley@noaa.gov).

Collaborating Scientists: Tom Nalepa (GLERL), Brian Eadie (GLERL), Greg Lang (GLERL)

The Great Lakes amphipod Diporeia spp. is a highly prominent benthic invertebrate of the upper Great Lakes that comprises a large portion of resident macrofauna biomass, constitutes an important food base for fish, while representing a significant pathway for transfer of toxic contaminants to higher levels of the foodchain. A six-year sampling effort at a 45-m site in southeastern Lake Michigan from 1984 to 1989 indicated that annual Diporeia production (grams dry-weight biomass produced per m² per yr.) was higher than rates noted elsewhere in the Great Lakes and other North American lakes. Moreover, year-to-year production at the site varied more widely than noted elsewhere. Sampling in 1988 and 1989 at a 100-m site in southeastern Lake Michigan revealed a similar high level of Diporeia production, relative to depth.

The objective of this project is to estimate Diporeia production at three 45-m-deep Lake Michigan sites to determine how much the amphipod's production may vary spatially at a depth where its abundance is generally the highest in southeastern Lake Michigan. Additionally, sequentially-collecting sediment-traps deployed 15 m above the bottom will enable estimation of downward flux of carbon to sediments and provide for comparison of food availability on-site and associated Diporeia production.

FY97 Plans

• Deploy sequentially-collecting sediment-traps, 15 m off bottom, at three 45-m Lake Michigan sites. Retrieve sediment-traps at end of season and estimate carbon flux to traps occurring over course of field season.
• Collect monthly sediment samples at each of three 45-m sites in southeastern Lake Michigan and process samples.
• Calculate Diporeia production and compare among three sites, and with 1984 -1989 data.

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Collaborating Scientists: Joann Cavaletto, David Fanslow (GLERL); Donald Schloesser and Charles Madenjian (USGS/BRD/Great Lakes Science Center)

The burrowing mayfly Hexagenia was once very abundant in many nearshore regions of the Great Lakes including Green Bay, Saginaw Bay, and western Lake Erie. Because of eutrophication, populations of this pollution-sensitive organism declined dramatically in the 1950s and remained at low levels through the 1980s. Recent evidence indicates that populations are now returning in some areas, and in the western basin of Lake Erie, abundances have increased every year since 1991 according to published reports, and individual Hexagenia have also been reported in the lower Fox River in Green Bay. At present, the environmental changes that led to this recolonization are unknown. In the western basin, the return of Hexagenia may be a response to declines in algal blooms and anoxia events resulting from several decades of nutrient abatement programs. However, some scientists have pointed out that these abatement programs are not necessarily the sole reason, since the recolonization process began in earnest only after zebra mussels became widespread and abundant in the basin.

Hexagenia will likely have profound impacts on energy-flow pathways in areas where it becomes re-established. This organism is the preferred prey of many species of fish including perch and walleye. Some of the highest growth rates for perch have been associated with high consumption of Hexagenia. As a prey item, Hexagenia can also be an important means by which contaminants are cycled through the food web.

The objectives of this project are to:

1. Determine seasonal changes in lipid content and lipid class composition in Hexagenia at several different sites with contrasting environmental conditions (western Lake Erie, Lake St. Clair, and the Straits of Mackinac). Lipids have nearly twice the metabolic energy as proteins or carbohydrates, and lipid accumulation is necessary for proper metamorphosis and reproduction in aquatic insects such as Hexagenia.
   
   
2. Document changes in lipid content as individuals develop through the various life stages. Changes in lipid levels throughout an organism's life stages may strongly affect its uptake and elimination of lipophilic organic contaminants. Since lipid content in benthic organisms is generally a function of food availability, comparing lipid values from several different sites offers a means to assess the "health" of a given population relative to variations in environmental conditions.
   
   
3. Assess populations in the vicinity of the Straits of Mackinac. Hexagenia were found at selected sites in the straits region in the mid-1950s, but there is speculation that populations have since declined. In addition to collecting samples for lipid analyses, we will conduct a quantitative survey of Hexagenia populations at the same sites that were sampled in the mid-1950s.

FY97 Plans

• Collect Hexagenia monthly in western Lake Erie at a site to be determined jointly by GLERL and USGS.
• Collect Hexagenia monthly in Lake St. Clair at a site where lipids were measured in 1986.
• Collect Hexagenia in the Straits of Mackinac in May/June and in September at sites to be determined. A quantitative survey will also be conducted on the former date.

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Collaborating Scientists: Marie Bundy (National Research Council and CILER Post-doc); J.R. Strickler (University of Wisconsin - Milwaukee)

In the Great Lakes, copepods are the dominant grazers of phytoplankton and are important predators of ciliates and invertebrate larvae. Recent studies indicate that calanoid copepods are capable of discriminating between food particles that differ in nutritional quality. High-speed microcinematography has revealed that calanoids can detect the presence of particles as small as 5 and use coordinated actions of the mouthparts to capture them. It is not known, however, whether mechanoreception or chemoreception, or both sensory modes are used to detect and discriminate between particles. Because copepods are important mediators of trophic energy movement in the Great Lakes food web, understanding the influences of sensory physiology and behavior on their ability to feed selectively, and defining this selection accurately, is critical to understanding the impact of anthropogenic perturbations to aquatic food webs.

FY96 Progress and Accomplishments

A new computer program was written, the computer was upgraded, and the speed of data acquisition of the Critter Cam was more than doubled. The camera system was structurally improved, and larger, optically correct filming vessels were constructed. Dr. J.R. Strickler at the University of Milwaukee modified the camera optics to produce a higher resolution image. Programs using MatLab numeric computation and visualization software were written to interface the position data from the camera with image analysis data from the Peak Performance motion analysis system. As a result, except for the camera system in Dr. Strickler's lab, there is no other system in existence that can provide high spatial and temporal resolution observations of freely swimming zooplankton, over long periods of time in large volumes of water.

Preliminary behavioral experiments with several copepod species were conducted. The original research plan was modified to explore how different copepod species respond behaviorally to zebra mussel larvae. The results of these experiments were presented at the AGU\ASLO 1996 Ocean Sciences Meeting in February 1996 and at the Sixth International Zebra Mussel and Other Aquatic Nuisance Species Conference in March 1996.

We conducted experiments and collected data that revealed the hydrodynamic and behavioral mechanisms used by Diaptomus sicilis to detect and capture inert particles. These results are being prepared for publication.

FY97 Plans

• Finish behavioral experiments with Diaptomus minutus and D. ashlandi.
• Complete video tape analyses of copepods feeding under various conditions.
• Familiarize GLERL project scientists with the new motion analysis system and data analyses protocol. This will pass on the technology developed by NRC/CILER Post-doc so that it will be available for their future work.

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ERL Research Task: GLERL 12 - Episodic Events

Episodic events, such as storms, spring floods, development and decay of the thermal bar, and other short-lived, but repeatedly occurring physical phenomena, may promote non-linear responses in the ecosystem they affect. Speculation and anecdotal information is that episodic events are very important to nutrient and contaminant cycling and to mass transport processes, and may have a major influence on ecosystem conditions that affect productivity and recruitment. The following projects seek to make time-series measurements, mostly, but not exclusively by instrumented moorings, of key ecological parameters before, during and after the occurrence/passage of an episodic event, such as a storm.


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Principal Investigator: Gary Fahnenstiel (231-759-7824; gary.fahnenstiel@noaa.gov).

There is a critical need for data on the impact of episodic events on biogeochemical processes and constituents. Most biological sampling and modeling represent average conditions measured across random temporal and spatial scales which have often been determined by the availability of vessels, the weather, and budgets. High frequency ecological data (time series) free from aliasing and on similar time and space scales as can be obtained for physical measurements are sorely needed to examine and resolve the role of episodic events in aquatic ecosystem structure and function. Episodic events include storms, coastal and offshore upwelling, transient eddy features, thermal bar phenomena, and large river spring-flood discharges. Small-scale, high-frequency spatial sampling is needed to distinguish between nearshore and offshore effects and frontal and eddy-like features. No such information exists in the Great Lakes or any other freshwater environment. Moreover, a quantitative approach for interpreting and predicting the impact of these events is also needed. This project provides a first step in addressing these issues in the Great Lakes.

The objectives of this project are to characterize biological responses to episodic events in the Lake Michigan, and to develop a mathematical context for interpretation and prediction of the impact of episodic events.

FY96 Progress and Accomplishments

During FY96 all major equipment for the development of an Lagrangian ecological drifter and moored instrument package were procured, and construction of the drifter was begun. However, due to funding limitations, we were unable to complete the development of these instrument packages during FY96.

FY97 Plans

• Complete assembly of the moored instrument package and field test it at the Lake Michigan Field Station.
• Complete assembly of the Lagrangian ecological drifter and field test it as time allows.

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

Collaborating Scientists: Nathan Hawley, Gerald Miller, John Robbins, David Schwab, George Leshkevich (GLERL); Thomas Johengen (CILER); Ruth Beeton (University of Michigan)

In the southeastern basin of Lake Michigan, there have been repeated satellite observations, in the spring, of an extensive plume of some type of material beginning very nearshore at the very southern end of the lake, propagating along the coast for approximately 100 km, and then dissipating offshore near South Haven. The offshore plume coincides with the region of highest sediment accumulation in Lake Michigan. The source, composition nor mass of materials involved are unknown at this time.

The primary objective of this effort is to sample this plume and determine, if possible, the source and eventual sink of the material that defines it. It is conceivable that the spring plume is a major, if not primary, mechanism for delivering sediments to the region of high accumulation near South Haven. The results of this study will be of interest and use to contaminant mass balance modelers, the Lake Michigan Management Plan Committee, and others with an ecosystem involvement with southern Lake Michigan.

FY96 Progress and Accomplishments

Three sediment-trap arrays containing a total of 4 sequencing traps and 3 current meters were deployed in October, 1995 and retrieved in May, 1996 in the region where the plume was observed during the years 1990-93. Three traps worked perfectly and collected 69 five day intervals of the plume event. One current meter failed, the other two recorded currents over the period of deployment. Samples and data are currently being analyzed.

A new remote multi-bottle sequencing water sampler (microprocessor controlled programmable sampling) to collect up to 24 one-liter in situ water samples was designed, and a prototype was constructed and deployed in Saginaw Bay for several months for testing. The prototype sampler appeared to work well, and 24 samples were obtained. It will complement our sequencing sediment-traps, which collect settling particles, by collecting whole water samples containing the entire suite of ambient particles.

We reported (at the summer meeting of the American Society for Limnology and Oceanography, in a NOAA press release, in the American Geophysical Union publication "EOS", as well as to a number of newspapers) satellite imagery and field observations of the initiation and subsequent development of an extensive coastal plume in southern Lake Michigan in March, 1996. The onset appeared to coincide with melting of the last snowpack/shore-ice in late March, and with the occurrence of a major storm. Within a few days, the feature was approximately 10 km wide and over 200 km long, implying that the source of the reflective materials was widely distributed. The feature persisted, with apparent recharging, for over a month and progressed northward along the eastern shore. Preliminary results indicate that the reflective materials in the plume are consistent with silty-clay materials eroding from bluffs along the shore of Lake Michigan. Since fine-grained materials are excellent substrates for sorption, this episodic event will play an important role in the particle scavenging of contaminants from the lake waters. High 'extractable-available P' within the plume, ensures that the timing of the event relative to lake warming will be important in the development of the spring diatom bloom and subsequent production.

FY97 Plans

• Document GLERL's interdisciplinary analyses and interpretation of the March 1996 southern Lake Michigan plume.
• Complete the analyses and documentation of the sediment-trap samples and current meter data collected in the spring of 1996 during the plume event.
• Analyze the performance of the remote water sampler and modify it as necessary to improve performance.
  

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last updated: August 9, 2002 mbl

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