2000 Ocean Sciences Program, ASLO-AGU
EEGLE Abstracts
January 24-28, 2000
San Antanio, TX
Episodic Events and Trophic Pulses: Estimating Surface Chlorophyll Concentrations and
Transport Using SeaWiFS Imagery
Budd, J W. Michigan Technological University
Warrington, D S. Michigan Technological University
Ransibrahmanakul, V. NOAA/NOS Center for Coastal Monitoring and Assessment
Chye, J D. Michigan Technological University
Understanding the frequency and time scale of episodic events is a first step toward understanding their
importance in lake trophic dynamics. Vertical and horizontal patterns can form, evolve, and decay during a
single season. However, little is known about the mechanisms of transport across these interfaces in large
lakes, the temporal progression of events, and the time course of water mass and trophic stimulation. The
focus of this remote sensing effort is on one of the most crucial linkages to biotic systems, at the base of
foodwebs, where limiting nutrients promote phytoplankton growth. Our general thesis is that remote sensing
technology will facilitate timely and cost effective analyses of changes in particle and chlorophyll abundances
seasonally and interannually. The time series imagery revealed significant productivity pulses (elevated Chl a)
associated with resuspended sediments in Lake Michigan during fall, winter, and spring months and the
development of a productive southern shore coastal corridor during spring in Lake Superior. Analysis of
simultaneously collected lake surface temperature imagery from the AVHRR revealed distinct horizontal
temperature gradients from nearshore to offshore in late March and April in Lake Michigan and during April
through July in Lake Superior. In both systems, the thermal bar (4 degree C water of highest density) which
was identified in AVHRR lake surface temperature imagery, separated nearshore from offshore waters. In
southern Lake Michigan, the result is two distinct chlorophyll populations separated by the thermal bar. In Lake
Superior, the thermal bar defines the nearshore coastal corridor where elevated chlorophyll and suspended
sediments are found. These events were previously
Basin-Scale Particle Flux Responses to Episodic Events
Eadie, B J. NOAA-GLERL
Lansing, M B. NOAA-GLERL
Winkelman, A G. CILER, The University of Michigan
Riley, C A. CILER, The University of Michigan
Giroux, B. CILER, The University of Michigan
In Lake Michigan, winter and early spring storms massively resuspend materials with characteristics of
sediment depositional regions and these materials are transported offshore into the center of the lake. We have
calculated that these events can resuspend over one million MT of particulate matter and sediment traps record
the offshore passage of these materials. Several years of trap collection at offshore sites show a range in
mass and nutrient fluxes that span a factor of ten. The implication is that large events are crucial in the
movement of particulate matter and associated chemical constituents.
Absorption Characteristics of Three Phytoplankton Groups Associated with a Recurrent Coastal
Plume in Southeastern Lake Michigan
Kelly, K A. University of Southern Mississippi
Lohrenz, S E. University of Southern Mississippi
Fahnenstiel, G L. NOAA, Great Lakes Environmental Research Laboratory
Light absorption by photosynthetic pigments is an important process for phytoplankton growth and primary
production. Typically, phytoplankton absorption has been determined at the community level using bulk
measurements. Use of microphotometric techniques enables the direct measurement of the in vivo
absorption efficiency factor (lambda) of individual cells. This technique combines microscopic
and spectrophotometric methods to provide a measure of spectral transmittance of individual particles, from
which lambda can then be calculated. Applications of this method were used to study
phytoplankton populations in southeastern Lake Michigan. Light is an important variable controlling the
development of the spring diatom community in Lake Michigan. This study examined the impact of a recurrent
coastal plume on variations in light availability and the associated absorption characteristics of three
phytoplankton groups in the vicinity of the plume. lambda for a given group did not significantly
vary with depth. However, temporal variations in the magnitude of lambda did occur within
groups as reflected in changes in the blue:red ratios with time. The three groups that were studied -
Aulacoseira islandica, Aulacoseira subarctica, and centric diatoms of 8-12 um diameter - differed in
spectral shape of lambda in the blue portion of the spectrum. For a given time and species,
comparisons of lambda across plume gradients showed no apparent differences in magnitude
or spectral shape. These results will be used in conjunction with other single-cell measurements to examine
spatial and temporal patterns in taxon-specific
Resurrection Ecology: Do Resting Egg "Seed Banks" Maintain Long-Term Genetic Diversity and
Species Composition in Lake Communities
Kerfoot, W C. Michigan Technological University
Lorence, C L. Michigan Technological University
Weider, L J. Oklahoma University
The development of a "seed bank" of resting eggs depends upon yearly production, hatching schedules, survival
during burial, and long-term viability. We show that cladoceran egg banks vary in genotype frequencies through
time, showing that populations evolve relatively rapidly at specific sites. However, in large lakes, storm events can
purge a portion of the buried eggs from the "seed bank", resurrecting both ancient genotypes (intraspecific
component) and species (interspecific component). On the scale of decades to centuries, the frequency of
episodic events could be important for maintaining genetic and community diversity. Examples from freshwater
estuaries (Portage Lake) and large (Lake Michigan, Lake Superior) lakes are used to clarify aspects of the
investigation methods.
Trophic Interactions Between Microzooplankton and Planktonic Copepods in Lake Michigan
During the Winter-spring Transition Period
Lavrentyev, P J. The University of Akron
Bundy, M H. Academy of Natural Sciences Estuarine Research Center (ANSERC)
Vanderploeg, H A. NOAA, Great Lakes Environmental Research Laboratory
Kovalcik, P A. The University of Akron
A set of laboratory and shipboard experiments was conducted in southern Lake Michigan in 1998 and 1999 to
examine the growth and grazing loss rates of microzooplankton during the winter-spring transition period. The
study was a part of the Episodic Event Great Lakes Experiment (EEGLE). Despite low ambient temperatures (2
to 4 deg C, the average specific growth rate of microzooplankton (predominantly ciliates) was close to 0.4
d-1 and in certain ciliate taxa it exceeded 1 d-1. The predominant calanoid copepods,
Diaptomus
sicilis and Limnocalanus macrurus, selectively grazed the hymenostomatid ciliate Lembadion lucens
and oligotrichs. Nauplii of Diaptomus also actively grazed ciliates. These preliminary results suggest that
microzooplankton can be an important part of the diet of over-wintering planktonic copepods and their nauplii.
In Situ Observations of Sediment Resuspension and Horizontal Sediment Flux in a
Non-Depositional Region of Southern Lake Michigan
Lesht, B M. Argonne National Laboratory
Previous observations of near-bottom conditions and sediment resuspension in Lake Michigan have
concentrated on the areas of high sediment deposition in the southeastern part of the lake and on Indiana
Shoals in the southwestern part. No previous observations have been made in the western areas of the lake
adjacent to the Wisconsin bluffs, primarily because these waters were considered to be non-depositional and
thus limited in the amount of resuspendable sediment available for transport. During 1998, the first EEGLE field
year, we used an instrumented tripod to make measurements intended to test the hypothesis that the
apparently recurrent winter-spring resuspension event (misnamed "plume") includes new material eroded from
the Wisconsin near-shore. Almost 2300 hours of simultaneous near-bottom temperature, transparency and
current velocity, along with surface wave height data were collected in three deployments done in April,
August, and November. The results show that the local sediment, a sandy cohesive clay, is indeed
resuspended in response to the combined action of currents and surface waves. Net horizontal sediment flux
in April was almost directly parallel to the shore and towards the south. In November, however, the net
horizontal sediment flux was onshore, perhaps representing the temporary storage of a more easily
resuspendable pool of sediment.
Distributions of Inherent Optical Properties in a Recurrent Coastal Turbidity Plume in
Southeasten Lake Michigan
Lohrenz, S E. University of Southern Mississippi
Fahnenstiel, G L. NOAA, Great Lakes Environmental Research Laboratory
Schofield, O M. Rutgers University
Millie, D F. USDA-ARS
A recurrent coastal turbidity plume (RCP) is a consistent feature observed in southern Lake Michigan during the
spring isothermal period. The plume feature occurs at roughly the same time as the spring diatom bloom and its
impact on phytoplankton growth is unclear. A goal of the Coastal Ocean Processes-Episodic Events in the
Great Lakes Experiment (CoOP-EEGLE) is to determine the impact of transport of materials along the coastal
margin on biological processes. Current hypotheses differ as to the primary mechanism by which the plume
may affect phytoplankton growth. Although light availability is believed to be important in regulating growth, the
RCP may also influence the availability of limiting nutrients, principally phosphorus. A prerequisite to resolving
questions about the impact of the RCP on phytoplankton growth is a precise description of the optical
conditions within the plume and the light utilization efficiencies of phytoplankton. Inherent optical properties of
the RCP and adjacent waters were characterized during March 1999 in southeastern Lake Michigan using a
combination of in situ instrumentation and in vitro spectrophotometric methods. Good agreement was
found between spectrophotometric and in situ measurements. Spatial variability in light attenuation was
primarily attributable to scattering, and, to a lesser degree, by absorption due to particles. Light absorption by
phytoplankton pigments was a relatively small proportion of total absorption in the blue region of the spectrum
due to a strong detrital signature. Optical properties were useful predictors of constituent concentrations.
Scattering at 650 nm was significantly correlated with total suspended matter concentrations. Absorption at
676 nm was significantly correlated with chlorophyll a concentrations. Phytoplankton pigment spectral
absorption showed a consistent shape across a wide range of optical conditions, an indication that pigment
composition changes related to photoacclimation were minor across plume gradients. These findings will be
used to support complementary efforts to characterize the irradiance
Observations on the Coastal Flow in Southern Lake Michigan
McCormick, M J. NOAA/GLERL
Miller, G S. NOAA/GLERL
Murthy, R C. National Water Research Inst.
Saylor, J H. NOAA/GLERL
A three year long field program investigating cross-margin transport processes and their effect on lake
ecology was initiated in southern Lake Michigan in late 1997. An observation strategy involving both Eulerian
and Lagrangian techniques is being used to describe the coastal flow. Ten current meter moorings were
deployed in October 1997 and were concentrated along the southeast coast of the lake in an attempt to better
resolve convergence zones and offshore/onshore transport. Six moorings were configured with a mid-level
and near-bottom mounted vector averaging current meter and the four remaining moorings consisted of a
bottom mounted acoustic Doppler current profiler. The longshore and crosshore barotropic current response
over winter '97 - '98 revealed a dominant longshore flow with mean currents nearly an order of magnitude
stronger than the crosshore component. Time series data show numerous current reversals with data from
the shallow 20 m moorings showing a strong coupling with changes in the surface wind stress. Data from the
60 m moorings were more strongly influenced by the large scale circulation. A topographic wave with an
approximate four day period, first identified by Saylor et al. (1980), also appears in the coastal data. The
effects of the March '98 storm show pronounced offshore transport at all sites. The averaged currents show
a net northerly longshore and a very weak westerly offshore flow. Surface flow characteristics were also
observed using satellite reporting drifting buoys during April '98 and '99.
Coastal Transport and Flux in Episodic Events in Lakes Michigan and Superior
Niebauer, H J. Univ. Wisconsin-Madison
Stephens, M Y. Univ. Wisconsin-Madison
A major goal of the NSF-OCE and NOAA-COP on Coastal Studies in the Great Lakes is to improve the
understanding of transport processes across the coastal margins of the Great Lakes. Major features of the
coastal margin of the Great Lakes that affect transport include coastal upwelling and downwelling, baroclinic
geostrophic coastal jets with speeds at times exceeding 50 cm/sec, thermal bars with strong vertical
convection, etc. This poster describes preliminary results of numerical simulations comparing Lakes Michigan
and Superior in terms of along shore and cross shore transport and flux of mass and carbon as a result of
episodic events listed above. Also presented are analyses illustrating the necessity of including episodic
events to balance the primary production budgets of both Lakes. The model data are compared with field data
whenever possible for comparison and verification.
Modeling the 1998 Coastal Turbidity Plume Event in Lake Michigan
Schwab, D J. NOAA Great Lakes Environmental Research Laboratory
Beletsky, D. Dept. of Naval Architecture and Marine Eng., Univ. of Michigan
Lou, J. NOAA Great Lakes Environmental Research Laboratory
McCormick, M J. NOAA Great Lakes Environmental Research Laboratory
Miller, G S. NOAA Great Lakes Environmental Research Laboratory
Roebber, P J. Dept. of Geosciences, Univ. of Wisconsin-Milwaukee
Numerical models of coastal circulation, wind-waves, and sediment transport are used to investigate the role
of wind-induced circulation in the offshore transport of sedimentary material in Lake Michigan during the
massive March, 1998 turbidity plume event. Model results showed that circulation in Lake Michigan is highly
episodic since it is almost entirely wind-driven in early spring. The characteristic wind-driven circulation pattern
in the lake consists of two counter-rotating gyres, a counterclockwise-rotating gyre to the right of the wind
and a clockwise-rotating gyre to the left. The gyres are separated by a convergence zone along the
downwind shore with resulting offshore flow and a divergence zone along the upwind shore with onshore
flow. This two-gyre circulation pattern with offshore flow was especially clearly seen during a northerly wind
event (with winds up to 17 m/s) in March in southern Lake Michigan. The strongest sediment resuspension
occurred in the southern lake and the shallow waters along the coastline. This is because of the larger waves
in southern Lake Michigan due to the dominant northerly wind in this early spring period. The circulation and
wave models are driven with surface momentum flux derived from observed meteorological conditions at 12
land stations in March 1998 and also with surface winds calculated using the mesoscale meteorological model
MM5 (Dudhia, 1993) in four dimensional data assimilation mode on a 6 km grid in order to determine the
sensitivity of onshore-offshore transport in southern Lake Michigan to various types of wind data. Current
observations from 11 subsurface moorings are compared to simulated current in order to estimate the quality
of the meteorological data sets.
Particle Residence Times and Transport in Nearshore Lake Michigan: Sediment Inventories of
Excess Th-234
Klump, J V. University of Wisconsin-Milwaukee
Waples, J T. University of Wisconsin-Milwaukee
Orlandini, K A. Argonne National Laboratory
Edgington, D N. University of Wisconsin-Milwaukee
MacKenzie, R A. University of Wisconsin-Milwaukee
Szmania, D C. University of Wisconsin-Milwaukee
Robbins, J A. NOAA, Great Lakes Environmental Research Laboratory
Eadie, B J. NOAA, Great Lakes Environmental Research Laboratory
Particle concentrations within the coastal margin of Lake Michigan vary dramatically in response to episodic
sediment resuspension events. This nearshore zone is characterized by non-depositional sand, hard clay and
cobble bottoms wherein particles reside only temporarily. Changing inventories of naturally occurring
short-lived radionuclides can provide information on the frequency and duration of resuspension, on the
residence time of particles in the nearshore benthic system, and on the cross margin transport of particulate
materials to the major zones of permanent deposition and burial on the eastern margin of the southern basin.
Samples of the resuspendible sediment pool have been collected using an ROV deployed sampling system
throughout the southern basin of the lake in depths from 10 to 40 meters. Inventories of the mass of
resuspendible material on the bottom range from 10 to 300 mg cm-2 and inventories of excess Th-234 (half life =
24 d) range from approximately 10 to 1000 fCi cm-2. Residence times for particles in the overlying water based
upon the flux of excess Th-234 to the sediment are on the order of days to weeks. In combination with water
column inventories, these sediment inventories provide measurements of time dependent fluctuations in particle
deposition, resuspension, particle settling rates, and alongshore transport.
Particle Residence Times and Transport in Nearshore Lake Michigan: Water Column Inventories
of Th-234 and Th-228
Waples, J T. University of Wisconsin-Milwaukee
Klump, J V. University of Wisconsin-Milwaukee
Orlandini, K. Argonne National Laboratory
Edgington, D N.University of Wisconsin-Milwaukee
MacKenzie, R. University of Wisconsin-Milwaukee
Szmania, D. University of Wisconsin-Milwaukee
Robbins, J A. NOAA, Great Lakes Environmental Research Laboratory
Eadie, B J. NOAA, Great Lakes Environmental Research Laboratory
Estimating the residence time of new and resuspended particles in the nearshore water column of southern
Lake Michigan is a crucial objective of the EEGLE (Episodic Events - Great Lakes Experiment) program.
Suspended particle residence times combined with measured and modeled vectors of advection and diffusion
can be used to estimate the cross-margin (near shore - off shore) flux of nutrients and contaminants. To
estimate the residence time of suspended particles, we measured 1) surface water, 2) integrated water
column and 3) surface sediment activities of the particle reactive tracers Th-234 and Th-228 - giving us
essentially three semi-independent residence time estimates. Based on samples collected on 10 cruises over a
two year period at 14 stations ranging in depth from 10 to 150 meters, particle residence times range from less
than one week to over six months. We intend to show how these residence times correlate with water column
depth, external energy inputs (i.e. wind and storm activity) and biological productivity. We will also discuss the
concordance of residence time estimates based on isotopic disequilibrium methods and how well these
estimates agree to residence times calculated from sediment trap data.