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GLERL Publication Abstracts: FY 2001
Publications List Key |
Capitalized names represent GLERL authors. |
* = Not available from GLERL. |
** = Available in GLERL Library only. |
ASSEL, R. A. Ice records on Grand Traverse Bay. In Grand Traverse
Bay State of the Bay Report 2000, C. Wright and A. Hensen (Eds.),
The Watershed Center, Grand Traverse Bay, Traverse City, MI, pp. 18 (2000).
The dates of formation and loss of ice on lakes and rivers were
of interest in past centuries in Europe, Asia, and North America because
stable ice cover provided a platform for transportation, fishing, and
hunting during the winter months. For these reasons, records of freeze-up
and break-up have been kept for several centuries at some bays, rivers,
and small inland lakes. These records are also of interest to scientists
because the extent and duration of ice cover is a sensitive indicator
of climate and climate change. Ice cover also affects biological activity
in the waters under the ice. Records of freeze-up and break-up dates for
Grand Travers Bay (which start in1851) are among the longest available
for the Great Lakes. Freeze-up is defined to occur when there is solid
ice over West Bay from its southern shoreline to Power Island.
ASSEL, R. A., and D. C. NORTON. Visualizing Laurentian Great Lakes ice
cycles. EOS Transactions 82(7):83 (2001).
In 1994, under the auspices of the National Oceanic and Atmospheric
Administration's (NOM) Earth System and Data Information Management (ESDIM)
Program, a project was initiated to update a 20-winter digital ice concentration
database and ice concentration climatology (see Internet at http://www.glerl.noaa.gov/res/Task_rpts/ccassel11-2.html).
The data reduction phase of that project is now complete. The National
Ice Center (NIC) and the Canadian Ice Service (CIS) contributed the historic
ice charts used in this project. The first analysis product from the updated
data- base is a set of computer animations of the seasonal progression
of ice cover extent and concentration for 23 individual winter seasons.
A daily time series of ice concentration grids was produced by interpolating
between consecutive ice charts for a given winter season. These data were
used to produce color-coded GIF files of daily ice concentration, the
percent of a unit of surface area covered by ice, and subsequently, to
make computer animations for each winter in AutoCAD Flic (FLC) and Audio
Video Interleave (AVI) formats. The animations portray the spatial and
temporal patterns of Great Lakes ice cover for each winter season from
1973 to 1995. The interannual variability of ice cover for a given date
or period in the winter is portrayed by comparing animations for that
date or period to different winters. Interannual and same-season variations
in ice cover are of interest for analysis of other lake-related phenomena
such as the frequency and extent of lake-effect snowfall, fish recruitment,
and the timing of the spring costal processes associated with the loss
of ice cover.
BELETSKY, D., and D. J. SCHWAB. Modeling circulation and thermal structure
in Lake Michigan: Annual cycle and interannual variability. Journal
of Geophysical Research 106(C9):19745-19771 (2001).
A three-dimensional primitive equation numerical model was applied
to Lake Michigan for the periods 1982-1983 and 1994-1995 to study seasonal
and interannual variability of lake-wide circulation and thermal structure
in the lake. The model was able to reproduce all of the basic features
of the thermal structure in Lake Michigan: spring thermal bar, full stratification,
deepening of the thermocline during the fall cooling, and finally, an
overturn in the late fall. Large-scale circulation patterns tend to be
cyclonic (counterclockwise), with cyclonic circulation within each subbasin.
The largest currents and maximum cyclonic vorticity occur in the fall
and winter when temperature gradients are low but wind stresses are strongest.
The smallest currents and minimum cyclonic vorticity occur in spring and
summer when temperature gradients are strong but wind stresses are weakest.
All these facts are in agreement with observations. The main shortcoming
of the model was that it tended to predict a more diffuse thermocline
than was indicated by observations and explained only up to half of the
variance observed in horizontal currents at timescales shorter than a
day.
Breneman, D., C. Richards, and S. LOZANO. Environmental influences on
benthic community structure in a Great Lakes embayment. Journal of
Great Lakes Research26(3):287-304 (2000). http://www.glerl.noaa.gov/pubs/fulltext/2000/20000007.pdf
Biological and chemical measurements of sediment are useful
parameters when establishing long-term assessment and monitoring tools
for designated areas of concern (AOCs) in the Great Lakes. An intensified
Environmental Monitoring and Assessment Program (EMAP) sampling grid in
the St. Louis River estuary of western Lake Superior was used to assess
the relationship between surficial sediment characteristics and benthic
community structure. Ninety sites within two habitat classes (< 5.5
m and >5.5 m depth) were randomly sampled. Sediment for chemical analysis
was collected with a cylindrical drop core while benthic macroinvertebrate
abundance and composition were determined from petite Ponar grab samples.
Taxa richness was variable (1 to 25 taxa) among sites in the St. Louis
River AOC. Oligochaeta were the most abundant taxa while Chironomidae
larvae provided a majority of the taxa richness with 43 genera. Results
from multivariate redundancy analysis (RDA) on 13 environmental parameters
revealed that the majority of variation in benthic community structure
was attributed to water depth and site distance from the headwaters. Although
physical habitat alterations occur over large spatial scales and are more
subtle than those conditions associated with chemically impacted sites,
only a small portion of the variability in benthic community structure
was explained by sediment chemistry variables. Variability in benthic
community structure during this survey was best explained by physical
habitat features and must first be quantified prior to understanding benthic
response to contaminated sediments.
Budd, J. W., T. D. Drummer, T. F. NALEPA, and G. L. FAHNENSTIEL. Remote
sensing of biotic effects: Zebra mussels (Dreissena polymorpha) influence
on water clarity in Saginaw Bay, Lake Huron. Limnology and Oceanography
46(2):213-223 (2001).
http://www.glerl.noaa.gov/pubs/fulltext/2001/20010014.pdf
http://www.aslo.org/lo/toc/vol_46/issue_2/0213.pdf
In this study, Advanced Very High Resolution Radiometer (AVHRR)
remote sensing reflectance (Rrs), imagery from 1987-1993 is used to study
changes in water clarity before and after zebra mussels (Dreissena
polymorpha) were discovered in Saginaw Bay, Lake Huron. Spatial and
temporal trends in the data indicate distinct and persistent increases
in water clarity in the inner bay after the first large recruitment of
zebra mussels in the fall of 1991. The pre-Dreissena imagery show
that turbidity in the inner bay was influenced by the Saginaw River discharge
in spring, biological production (plankton) in summer, and wind-driven
resuspension in fall, with highest turbidity in spring and fall. Spatial
patterns in the post Dreissena images were more similar regardless of
season, with low reflectances in the shallow regions of the inner bay
where zebra mussel densities were highest. A regression model based on
point data from 24 sampling stations over the 7-yr period indicates that
reflectances varied significantly by site and zebra mussel densities,
as well as seasonally. Trends in observed and predicted values of reflectances
followed similar patterns at each station-highest values were found during
1991 and lowest during 1992 at all stations, with slightly higher Rrs
in 1993 compared to 1992. Whereas AVHRR Rrs highlight the value of historical
imagery for reconstructing seasonal and interannual turbidity patterns
in near-shore waters, a new generation of operational ocean color satellites,
such as SeaWIFS (Sea-viewing Wide Field-of-view Sensor) and the newly
launched MODIS (moderate resolution imaging spectroradiometer), now provide
for routine monitoring of important biological and physical processes
from space.
CROLEY, T. E. II. Climate-biased decisions via partial historical sampling.
Proceedings, World Water and Environmental Resources Congress, Bridging
the Gap: Meeting the World's Water and Environmental Resources Challenges,
D. Phelps and G. Sehlke (Eds.), Orlando, FL, May 20-24, 2001. American
Society of Civil Engineers, Washington, DC, pp. 10 (2001). http://www.glerl.noaa.gov/pubs/fulltext/2001/20010001.pdf
A heuristic approach for incorporating probabilistic meteorology
outlook, via operational hydrology, into derivative hydrology probability
forecasts or storm frequency distributions is described. It constructs
a weighted set of future possibilities that agree with selected meteorology
outlooks. Many times, calculated weights are zero-valued and a questions
arised on how to properly consider them in the biased sample. After exploring
the effects of directly using zero-valued weights, an alternative is presented
that omits historical observations from the biased sample corresponding
to zero-valued weights (partial historical sampling). This requires adjustment
of the non-zero weights and redefinition of hydrology forecast statistics
that are based on the biased sample. Examples of simple storm frequency
estimation, using El Nino conditional probabilities, illustrate the problem
with zero-valued weights for some estimators and their negligible effect
with other estimators.
CROLEY, T. E. I. Climate-biased storm-frequency estimation. Journal
of Hydrologic Engineering 6(4):275-283 (2001). http://www.glerl.noaa.gov/pubs/fulltext/2001/20010002.pdf
Storm frequencies for the future are often estimated directly
from past historical records of sufficient length. The estimation requires
no detailed knowledge of the areas meteorology, but presumes it is unchanged
in the future. However, the climate seldom remains static. Numerous climate
forecasts of meteorological probabilities over extended periods are now
available. It is possible to use these meteorological forecasts directly
in the estimation of storm frequencies from the historical record. A heuristic
approach is defined here to estimate storm frequencies that recognize
forecasts of extended weather probabilities. Basically, those groups of
historical meteorological record segments matching forecast meteorological
probabilities are weighted more than others, during the estimation of
storm frequencies. (Affiliated groups of hydrologic record segments may
be similarly weighted for hydrological estimation; e.g., flood frequency
estimation.) An example of frequency estimation is made for maximum annual
daily flow, using currently available agency meteorological forecasts
in the United States and Canada.
EADIE, B. J., G. S. MILLER, M. B. LANSING, and A. G. WINKELMAN. Chapter
2. Settling particle fluxes and current and temperature profiles in Grand
Traverse Bay, Lake Michigan. In Final Report. Trophic Transfer of Atmospheric
and Sedimentary Contaminants into Great Lakes Fish: Controls on Ecosystem-Scale
Response Time, University of Maryland Center for Environmental Science,
Solomons, MD, pp. 25 (2001).
Settling particle fluxes and mass flux profiles are reported
for trap samples collected at five stations in Grand Traverse Bay, Lake
Michigan during 1997-1999. Trap collection precision is estimated, and
10 cm and 20 cm diameter sequencing traps are inter-calibrated using data
from traps deployed in replicate on specially constructed brackets. Temperature
data is reported for two stations (during June-September 1997). Acoustic
Doppler Current Profilers (ADCP) current meter data and contours of backscatter
strength, U and V current components, and water temperature are included
for the 95 m station. All data is available online in ASCII and MS Excel
formats at ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-116.
EADIE, B. J., and D. J. SCHWAB. Episodic Events - Great Lakes Experiment
(EEGLE). In Newsletter of Coastal Ocean Processes, Skidaway Institute
of Oceanography, Savannah, GA, pp. 8-9 (2001). http://www.glerl.noaa.gov/pubs/fulltext/2001/20010005.pdf
EEGLE PIs met at a three day workshop in late September, after
the successful completion of our third and final year of field work, to
discuss preliminary findings and foster interdisciplinary activities.
The EEGLE program was designed to quantify the impacts of major late winter-early
spring storms on sediment-water exchange, nearshore-offshore transport
and subsequent influence on the lakes productivity.
FAHNENSTIEL, G. L., R. A. STONE, M. J. McCORMICK, C. L. Schelske, and
S. E. Lohrenz. Spring isothermal mixing in the Great Lakes: Evidence of
nutrient limitation and nutrient-light interactions in a sub-optimal light
environment. Canadian Journal of Fisheries and Aquatic Science
57(9):1901-1910 (2000). http://www.glerl.noaa.gov/pubs/fulltext/2000/20000003.pdf
During the spring isothermal mixing period (April-May) in 1993-1995,
photosynthesis-irradiance and growth-irradiance experiments were conducted
in Lakes Erie, Huron. Michigan. and Ontario to assess light limitation.
Additionally, nutrient enrichment experiments were conducted in Lake Ontario.
Results from the photosynthesis-irradiance experiments suggested that
phytoplankton communities in all the lakes can be either light limited
or light saturated, as the threshold parameter (Ik) was similar
to mean water column irradiances (1 wc, ratio = 1.0). Growth-irradiance
experiments also suggested the potential for light saturation: mean daily
irradiance exceeded the threshold growth irradiance (I k,g) in 95% of
cases. Growth rates became light saturated at lower irradiances than photosynthetic
rates. Evidence for a nutrient-light interaction in controlling in situ
growth rates was also found in the nutrient enrichment experiments at
incubation irradiances >= Iwc .Our results suggest that an interaction
between nutrients and light is often controlling phytoplankton growth
during spring mixing in the Great Lakes. The role of these nutrient-light
interactions has increased in the past decade due to increased light availability
in the lower lakes caused by phosphorus load reductions and the filtering
activities of nonindigenous mussels.
FANSLOW, D. L., T. F. NALEPA, and T. H. JOHENGEN. Seasonal changes in
the respiratory electron transport system (ETS) and respiration of the
zebra mussel, Dreissena polymorpha in Saginaw Bay, Lake Huron.
Hydrobiologia 448:61-70 (2001).
Electron transport system activity (ETS) and respiration rates
(R) of the zebra mussel, Dreissena polymorpha, were determined
monthly from April to November over 2 years at two sites in Saginaw Bay,
Lake Huron. The sites were located in the inner and outer bay and contrasted
in food quantity and quality. ETS ranged from 2 to 40 ug 02
mg DW-1 h-1 over the study period. Both ETS and
respiration were strongly related to temperature, and maximum values were
found between June and August. ETS also peaked in June/July when assays
were conducted at a constant temperature (25 deg C), indicating other
factors besides temperature affected metabolic activity. R:ETS ratios
decreased with increased temperature at the inner bay site, but trends
were minimal at the outer bay site. In late summer, blooms of the cyanophyte
Microcystis occurred in the inner bay, likely depressing filtration
rates, and leading to lower respiration rates relative to ETS. ETS activity
was consistently higher in the outer bay and was likely a result of higher
food quality. Despite these spatial differences, annual mean R:ETS ratios
varied only from 0.04 to 0.09 at the two sites over the 2-year period.
Based on these values, ETS may be useful as an indicator of long-term
metabolic activity in annual energy budgets of D. polymorpha. However,
food conditions differentially affect respiration relative to ETS, and
variability in this ratio must be considered when interested in shorter
time scales.
GARDNER, W. S., L. Yang, J. B. Cotner, T. H. JOHENGEN, and P. J. Lavrentyev.
Nitrogen dynamics in sandy freshwater sediments (Saginaw Bay, Lake Huron).
Journal of Great Lakes Research 27(1):84-97 (2001). http://www.glerl.noaa.gov/pubs/fulltext/2001/20010006.pdf
Sediment-water nitrogen fluxes and transformations were examined
at two sites in Saginaw Bay, Lake Huron, as a model for sandy freshwater
sediments. Substantial ammonium release rates (74 to 350 umole NH4+/m2/hl)
were observed in flow-through cores and in situ benthic chamber experiments.
Sediment-water ammonium fluxes were similar at the inner and outer bay
stations even though inner bay waters are enriched with nutrients from
the Saginaw River. The high net flux of remineralized ammonium into the
overlying water from these sandy sediments resembles typical data for
marine systems (11 to 470 umole NH4+/m2/h1) but were higher than those
reported for depositional freshwater sediments (0 to 15 umole NH4+/m2/hl;
Seitzinger 1988). Addition of montmorillonite clay (ca. 1 kg dry weight/m2)
to the top of the sandy cores reduced ammonium flux. Mean "steady-state
" ammonium flux following clay addition was 46 +- 2 (SE) % of the initial
rates as compared to 81 +- 8% of the initial rates without clay addition.
Zebra mussel excretion dominated ammonium regeneration in the inner bay
where the bivalve was abundant, but addition of zebra mussel feces/pseudofeces
( 3.0 g dw/m2) to sediments did not increase ammonium or nitrate flux.
Partial nitrification of ammonium at the sediment-water interface was
suggested by removal of added 15 NH4+ from lake water passing over dark
sediment cores. Sediment-water fluxes of nitrogen obtained from flow-through
sediment cores resembled those from in situ benthic chambers. However,
extended static incubations in gas-tight denitrification chambers caused
more of the regenerated nitrogen to be nitrified and denitrified than
occurred with the other two measurement systems.
GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Aquatic Invasive Species
and the Great Lakes: GLERL's Program and Action Plan. NOAA, Great Lakes
Environmental Research Laboratory, Ann Arbor, MI, 2 pp. (2001). http://www.glerl.noaa.gov/pubs/brochures/broch.html
The national awareness of aquatic invasive species and the problems
they cause arose from the costly unintentional introduction of the zebra
mussel in the Great Lakes in the late 1980s and its subsequent spread
throughout the eastern half of the country.
GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Great Lakes Fish Community
Impacted by Diporeia Disappearance? NOAA, Great Lakes Environmental
Research Laboratory, Ann Arbor, MI, 2 pp. (2001). http://www.glerl.noaa.gov/pubs/brochures/broch.html
Sport fishing in the Great Lakes is valued at over $4 Billion
per year, with common catches consisting of lake trout, salmon, walleye,
and yellow perch. With the coincident introduction of the zebra mussel
and the disappearance of the important shrimp-like amphipod Diporeia,
the Great Lakes fisheries are in jeopardy.
GREAT LAKES ENVIRONMENTAL
RESEARCH LABORATORY. Great Lakes Ice Cover. NOAA, Great Lakes Environmental
Research Laboratory, Ann Arbor, MI, 2 pp. (2001). http://www.glerl.noaa.gov/pubs/brochures/broch.html
Ice has a deeper
connection to the Great Lakes than simply a signal of winter. In fact,
the lakes were formed over several thousands of years as mile-thick
layers of glacial ice advanced and retreated, scouring and sculpting
the basin. In addition, the ebb and flow of glacial meltwaters and rebound
of the underlying land from the weight of the massive ice sheets further
changed the basin's shape and drainage patterns.
If you wander down
the shores of Lake Michigan nowadays, it's difficult not to notice that
beaches seem curiously wide. Rocks that were once barely visible now
jut from the waves. Marina docks seem built too high for the boats that
pull up to them. A glance at the pilings tells why: the dark line marking
the lake levels of previous years is three feet about the water. Since
1998, the level of Lakes Michigan and Huron has dropped at the fastest
pace ever recorded. Long-time residents have been reminded of the droughts
of the 1930s and 1960s, when water levels also fell dramatically. Many
more have grown concerned about the impact upon both the shipping industry
and the environment.
During the winter
of 1990-1991 time series measurements of current velocity, temperature,
and attenuation (a measure of water transparency) were made at a site
in 91 m of water near Copper Harbor, MI. The observations show that
bottom resuspension occurred several times during the unstratified period.
The resuspension is the result of the interaction between high bottom
current velocities and surface waves generated by strong winds. Transport
during the storms was almost entirely alongshore, although some offshore
transport of material occurred. Calculations show that suspended material
could have been transported eastward several hundred km during the unstratified
period.
Helfand, J. S., D. P. Podber,
and M. J. McCORMICK. Effect of heat flux on thermocline formation. Proceedings,
ASCE Conference on Estuarine and Coastal Modeling, New Orleans, LA,
November 3-5, 1999. ASCE, pp. 114-129 (2000).
A numerical model based upon Deardorff (1980) was
used to simulate heat transfer between a lake and the atmosphere. The
model includes a lake-atmosphere heat exchange sub model, with penetration
of solar radiation. Heat and momentum are transferred in the vertical
with a one-dimensional model that disregards horizontal processes. Atmospheric
forcing to drive the models was taken from NOAA Marobs buoy 45007 in
the south central region of Lake Michigan, and from the nearby land
based stations at Milwaukee, WI and Muskegon, MI. Three simulations
were run and compared to field data collected by NOAA GLERL in 1996.
The simulations focused on the formation of the thermocline from June
9 to August 1. The first simulation used land-based atmospheric data
as inputs. the second used buoy data supplemented with land data where
needed. The results were compared to the field data and showed that
using terrestrial data can lead1o results that are plausible, but inaccurate.
The third simulation used buoy and land data as before. but adjusted
the incoming solar radiation to produce a better fit to the observed
data. The adjustment apparently compensated for deficiencies in the
land-based data.
HORNE, J. K. Acoustic approaches
to remote species identification. Fisheries Oceanography
9(4):356-371 (2000).
Noninvasive species
identification remains a longterm goal of fishers, researchers; and
resource managers who use sound to locate, map, and count aquatic organisms.
Since the first biological applications of underwater acoustics, four
approaches have been used singly or in combination to survey marine
and freshwater environments: passive sonar; prior knowledge and direct
sampling; echo statistics from high-frequency measures; and matching
models to low-frequency measures. Echo amplitudes or targets measured
using any sonar equipment are variable signals. Variability in reflected
sound is influenced by physical factors associated with the transmission
of sound through a compressible fluid, and by biological factors associated
with the location, reflective properties, and behavior of a target.
The current trend in acoustic target identification is to increase the
amount of information collected through increases in frequency bandwidth
or in the number of acoustic beams. Exclusive use of acoustics to identify
aquatic organisms reliably will require a set of statistical metrics
that discriminate among a wide range of similar body types at any packing
density, and incorporation of these algorithms in routine data processing.
HORNE, J. K., P. D. Walline,
and J. M. JECH. Comparing acoustic model predictions to in situ
backscatter measurements of fish with
dual-chambered swim bladders. Journal of Fish Biology
57:1105-1121 (2000).
Lavnun Mirogrex
terraesanctae have a dual-chambered swim bladder and are the dominant fish
species in Lake Kinneret, Israel. Bi-monthly acoustic assessments are
used to monitor lavnun abundance but the relation between the amount
of reflected sound and organism morphology is not well described. Predictions
from Kirchhoff-ray mode (KRM) backscatter models show a sensitivity
of echo amplitude to fish length and fish aspect. Predicted mean KRM
target strengths matched maximum in situ target strength measurements of eight tethered fish within
2.5 dB at 120 kHz and within 7 dB at 420 kHz. Tilt and roll of lavnun
during tethered measurements increased variance of backscatter measurements.
Accurate abundance and length frequency distribution estimates cannot
be obtained from in situ acoustic measurements without supplementary net samples.
Hwang, H., S. W. Fisher,
and P. F. LANDRUM. Identifying body residues of HCBP associated with
10-d mortality and partial life cycle effects in the midge, Chironimus
riparius. Aquatic Toxicology
52:251-267 (2001).
The relationship
between the body residue of 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP)
and its effects, including 10-d mortality and chronic sublethal effects
on the midge, Chironomus riparius, are examined in a partial life cycle assessment. The alga,
Chlorella vulgari , was loaded with 14C-Iabeled HCBP and fed to midges
as the method for delivery of the toxicant. In a 10-d bioassay, median
lethal body residue (LR50) was 0.57 (95% CI: 0.49-0.66) mmol/kg. In
the partial life cycle test, midges were fed a mixture of 12C- and 14C-HCBP-Iaden
algae and exposed in four separate tests to assess the different developmental
stages representing 2nd to 3rd instar, 2nd to 4th, 2nd to pupa, and
2nd to adult stages. A variety of sublethal endpoints were monitored,
including developmental time within a stadium, body concentration at
the end of each stadium, body weight, and fecundity (the number of ova)
for the female pupae and adults. Overall, midge body concentrations
of HCBP increased with increasing exposure concentration. Body weight
was not significantly affected by HCBP except during the 4th instar.
Body residue also increased with each successive stadium. Developmental
time increased significantly with increasing body concentration in 2nd
to 4th, 2nd to pupa, and 2nd to adult tests, while there was no statistical
significance in developmental time for the 2nd to 3rd instar test. The
number of ova decreased significantly in adults with increasing body
concentration of HCBP, with an average of 345 ova in controls, 289 ova
at 0.028 mmol/kg of HCBP, and 258 ova at 0.250 mmol/kg. These data,
which relate chronic endpoints to body residues, suggest that sublethal
endpoints in invertebrates are useful for defining sublethal hazards
of PCBs. These data also suggest that ecological consequences may result
from relatively low body burdens of PCBs.
JECH, J. M., and J. K.
HORNE. Effects of in situ target spatial distributions on acoustic density
estimates. ICES Journal of Marine Science 58:123-136
(2001).
One goal of acoustic-based
abundance estimates is to accurately preserve spatial distributions
of organism density and size within survey data. We simulated spatially
random and spatially auto-correlated fish density and sbs distributions to quantify variance in density,
abundance, and backscattering cross-sectional area estimates, and to
examine the sensitivity of abundance estimates to organism spatial distributions
and methods of estimating acoustic size. Our results show that it is
difficult to simultaneously estimate fish density and maintain accurate
sb-frequency distributions. Among our acoustic backscatter
estimation methods, a weighted-mean from a local search window provided
optimal estimates of density, abundance and crbs. Other methods tended
to bias either crbs or density estimates. This analysis identifies the
relative importance of variance sources when estimating organism density
using spatially-indexed acoustic data.
Kitchell, J. F., S. P.
Cox, C. J. Harvey, T. B. Johnson, D. M. MASON, K. K. Schoen, K. Aydin,
C. Bronte, M. Ebener, M. Hansen, M. Hoff, S. Schram, D. Schreiner, and
C. J. Walters. Sustainability of the Lake Superior fish community: Interactions
in a food web context. Ecosystems 3:545-560
(2000).
The restoration and
rehabilitation of the native fish communities is a long-term goal for
the Laurentian Great Lakes. In Lake Superior, the ongoing restoration
of the native lake trout populations is now regarded as one of the major
success stories in fisheries management. However, populations of the
deepwater morphotype (siscowet lake trout) have increased much more
substantially than those of the nearshore morphotype (lean lake trout),
and the ecosystem now contains an assemblage of exotic species such
as sea lamprey, rainbow smelt, and Pacific salmon (chinook, coho, and
steelhead). Those species play an important role in defining the constraints
and opportunities for ecosystem management. We combined an equilibrium
mass balance model (Ecopath) with a dynamic food web model (Ecosim)
to evaluate the ecological consequences of future alternative management
strategies and the interaction of two different sets of life history
characteristics for fishes at the top of the food web. Relatively rapid
turnover rates occur among the exotic forage fish, rainbow smelt, and
its primary predators, exotic Pacific salmonids. Slower turnover rates
occur among the native lake trout and burbot and their primary prey-lake
herring, smelt, deepwater cisco, and sculpins. The abundance of forage
fish is a key constraint for all salmonids in Lake Superior. Smelt and
Mysis play a prominent
role in sustaining the current trophic structure. Competition between
the native lake trout and the exotic salmonids is asymmetric. Reductions
in the salmon population yield only a modest benefit for the stocks
of lake trout, whereas increased fishing of lake trout produces substantial
potential increases in the yields of Pacific salmon to recreational
fisheries. The deepwater or siscowet morphotype of lake trout has become
very abundant. Although it plays a major role in the structure of the
food web it offers little potential for the restoration of a valuable
commercial or recreational fishery. Even if a combination of strong
management actions is implemented, the populations of lean (nearshore)
lake trout cannot be restored to pre-fishery and pre-lamprey levels.
Thus, management strategy must accept the ecological constraints due
in part to the presence of exotics and choose alternatives that sustain
public interest in the resources while continuing the gradual progress
toward restoration.
LANDRUM, P. F. A short
summary of the sources and distribution of contaminated sediments in
the Great Lakes. The Toledo Journal of Great Lakes Law, Science,
and Policy 3(1):19-25 (2000).
Sediment-associated contaminants are a legacy of the industrial
development of the United States. Sediments provide repositories of
persistent and highly sorptive contaminants that have found their way
into our lakes, rivers, streams, estuaries, and coastal oceans. These
contaminated sediments have been found to have substantial effects on
the ecosystem ranging from direct effects on benthic communities to
substantial contributions to contaminant loads and effects on upper
trophic levels through food chain contamination for tree swallows, for
Caspian terns, for mink. These effects directly impact human health
in that the number of watersheds with fish consumption advisories is
directly proportional to the extent of sediment contamination.
LANDRUM, P. F., D. C. GOSSIAUX, T. F. NALEPA, and D. L.
FANSLOW. Evaluation of Lake Michigan sediment for causes of the disappearance
of Diporeia spp. in southern Lake Michigan. Journal
of Great Lakes Research 26(4):402-407 (2000). http://www.glerl.noaa.gov/pubs/fulltext/2000/20000009.pdf
The amphipod, Diporeia spp., the dominant benthic macroinvertebrate
in the Great Lakes offshore waters, has exhibited a substantial decline
in recent years. This decline occurred after the invasion and colonization
of the lakes by the zebra mussel, Dreissena polymorpha.
It has been hypothesized that the decline is a direct result of the
competition by the zebra mussel decreasing the amount of food available.
This study examined the potential of other stressors, e.g., the presence
of toxic materials, as the contributing or main cause of the decline.
Bioassays were performed with sediments from stations currently devoid
of Diporeia (St. Joseph, MI) and with those still having
Diporeia populations. In 28-d mortality bioassays, no mortality
was observed with any of the sediments tested. However, in avoidance/preference
tests, sediments from St. Joseph, that are now devoid of Diporeia,
were avoided compared to sediments from Saugatuck, Grand Haven, and
Muskegon, which still have a population. This avoidance was not changed
by the addition of either Spirulina Plus@ or Tetramin@ flakes to the
sediment as a food source but was reversed by a fresh layer of the
diatom, Fragillaria crotonensi, on the sediment. These studies
suggest that despite the high carbon content of the St. Joseph sediment,
the nutritional content of the sediment was limited.
LANDRUM, P. F., E. A. TIGUE, S. KANE-DRISCOLL, D. C. GOSSIAUX,
P. L. VAN HOOF, M. L. GEDEON, and M. ADLER. Bioaccumulation of PCB congeners
by Diporeia spp.: Kinetics and factors affecting bioavailability.
Journal of Great Lakes Research 27(2):117-133 (2001).
http://www.glerl.noaa.gov/pubs/fulltext/2001/20010007.pdf
The toxicokinetics
of four polychlorinated biphenyl (PCB) congeners were determined for
the amphipod Diporeia spp. exposed to selected PCB congeners through both water
and sediment to determine the effect of temperature and organism size
(mass). For compounds with log Kow 6 or greater, the water-only
uptake coefficient (ku) was inversely proportional to the
size of the organism at all temperatures. For monochlorobiphenyl, ku
was directly proportional to organism mass only at 16 deg C. Increasing
temperature resulted in increasing uptake rate coefficients for all
compounds except hexachlorobiphenyl (HCBP) where ku did not
appear to depend on temperature. The hydrophobicity of the contaminants
did not contribute significantly to changes in uptake rate from water.
The elimination rate constant (ke) was inversely proportional
to organism size but was not significantly affected by temperature.
The elimination rate constant declined exponentially with increasing
log Kow As log Kow increased, the effect of organism
mass on ke was greatly reduced. The uptake from sediment
was affected by temperature and the congener log Kow. At
lower temperatures, the uptake coefficient from sediment (ks)
declined with increasing log Kow, while at higher temperatures,
it exhibited a slight upward trend. Smaller animals had much higher
uptake rates from sediment than large or medium size animals. Small
animals exhibited very high biota-sediment accumulation factors (5.4
to 20.8) over 4 to 16 deg C for HCBP (BSAF, concentration in the organism
normalized to the lipid content divided by the concentration in the
sediment normalized to the organic carbon content ). The relationship
between BSAF and log Kow was exponential for both laboratory
and field data.
LEE, J. H., P. F. LANDRUM, L. J. Field, and C.-H. Koh.
Application of S PAH model and a logistic
regression model to sediment toxicity data based on a species-specific,
water-only LC50 toxic unit for Hyalella azteca. Environmental
Toxicology and Chemistry 20(9):2102-2113 (2001).
Two models, a S polycyclic aromatic hydrocarbon
(PAR) model based on equilibrium partitioning theory and a logistic
regression model, were developed and evaluated to predict sediment-associated
PAR toxicity to Hyalella azteca. A SPAR model was applied to
freshwater sediments. This study is the first attempt to use a IPAR
model based on water-only, median lethal concentration (LC50) toxic
unit (TU) values for sediment-associated PAR mixtures and its application
to freshwater sediments. To predict the toxicity (i.e., mortality) from
contaminated sediments to H. azteca, an interstitial water
TU, calculated as the ambient interstitial water concentration divided
by the water-only LC50 in which the interstitial water concentrations
were predicted by equilibrium partitioning theory, was used. Assuming
additive toxicity for PAR, the sum of TUs was calculated to predict
the total toxicity of PAR mixtures in sediments. The SPAR model was developed from 10-
and 14-d H. azteca water-only LC50 values. To obtain estimates
of LC50 values for a wide range of PARs, a quantitative structure-activity
relationship (QSAR) model (log LC50 - log Kow) with a constant slope
was derived using the time-variable LC50 values for four PAR congeners.
The logistic, regression model was derived to assess the concentration-response
relationship for field sediments, which showed that 1.3 (0.63,9) TU
were required for a 50% probability that a sediment was toxic. The logistic-regression
model reflects both the effects of co-occurring contaminants (i .e.,
no measured PAR and unknown pollutants) and the overestimation of exposure
to sediment-associated PAR. An apparent site-specific bioavailability
limitation of sediment-associated PAR was found for a site contaminated
by creosote. At this site, no toxic samples were less than 3.9 TU. Finally
,the predictability of the !PAR model can be affected by species-specific
responses (Hyalella vs Rhepoxynius) chemical
specific (PAH vs DDT in H. azteca) biases, which are not
incorporated in the equilibrium partitioning model, and the uncertainty
from site-specific effects (creosote vs other sources of PAR contamination)
on the bioavailability of sediment-associated PAR mixtures.
LIU, P. C., D. J. SCHWAB,
and R. E. Jensen. Has wind-wave modeling reached its limit? Ocean
Engineering 29:81-98 (2002).
This article uses
a comparison of four different numerical wave prediction models for
hind-cast wave conditions in Lake Michigan during a 10-day episode in
October 1998 to illustrate that typical wave prediction models based
on the concept of a wave energy spectrum may have reached a limit in
the accuracy with which they can simulate realistic wave generation
and growth conditions. In the hindcast study we compared the model results
to observed waveheight and period measurements from two deep water NOAA/NDBC
weather buoys and from a nearshore Waverider buoy. Hourly wind fields
interpolated from a large number of coastal and overlake observations
were used to drive the models. The same numerical grid was used for
all the models. The results show that while the individual model predictions
deviate from the measurements by various amounts, they all tend to reflect
the general trend and patterns of the wave measurements. The differences
between the model results are often similar in magnitude to differences
between model results and observations. Although the four models tested
represent a wide range of sophistication in their treatment of wave
growth dynamics--they are all based on the assumption that the sea state
can be represented by a wave energy spectrum. Because there are more
similarities among the model results than significant differ-ences,
we believe that this assumption may be the limiting factor for substantial
improvements in wave modeling.
LOFGREN, B. M., F. H. QUINN,
A. H. CLITES, R. A. ASSEL, and A. J. Eberhardt. Water resources: Impacts,
challenges, and opportunities. In Preparing for Climate Change: The
Potential Consequences of Climate Variability and Change,
P.J. Sousounis and J.M. Bisanz (Eds.), US EPA, Ann Arbor, MI, pp. 29-37
(2000).
The Great Lakes/St.
Lawrence Seaway is used for transportation, hydropower generation, and
recreation. Hydropower facilities are located on the St. Marys, Niagara,
and St. Lawrence Rivers and at DeCew Falls off the Welland Canal. The
Great Lakes are also one of the prime recreational boating areas in
the country. The three-county area around Detroit has more boating registrations
than any other similar-sized area in the U.S. The Great Lakes system
contains one of the nation's prime sport fisheries as well as a smaller
commercial fishery, representing billions of dollars to the economy.
Because the Great Lakes basin is an internationally shared resource,
there are numerous state, provincial, county, and municipal authorities,
leading to a complex jurisdictional structure.
Accurate estimates
of surface energy exchange components are critical for understanding
many physical processes of large lakes and their atmospheric environment.
In this paper, the seasonal cycle of latent, sensible, and total heat
flux from the surface of the Great Lakes is estimated. Lake surface
temperatures derived from the NOAA AVHRR satellite, along with meteorological
data from surface station observations are incorporated in order to
estimate spatial distributions of fluxes. Several well-known features
are evident. Among these are the very high outgoing fluxes of latent
and sensible heat during the late fall and early winter, which drive
strong cooling of the lake surface and consequent convective mixing
within the lake column. Another is greater seasonal variation of surface
temperature and fluxes in shallower waters than in deeper waters. Due
to strong static stability of the overlying atmospheric boundary layer
during the spring, both the magnitude and the spatial variations of
latent and sensible heat fluxes are small during the spring and, to
a lesser degree, during the summer. The annual cycles of latent and
sensible heat flux over the Great Lakes are roughly opposite in phase
to the same fluxes over land, indicating a large exchange of energy
via atmospheric advection between the lake and land surfaces. A major
weakness of the method used here is that heat fluxes are calculated
on the basis of an ice-free surface, making the derived fluxes for January
through March roughly estimated.
Lotufo, G. R., P. F. LANDRUM,
and M. L. GEDEON. Toxicity and bioaccumulation of DDT in freshwater
amphipods in exposures to spiked sediments. Environmental Toxicology
and Chemistry 20(4):810-825 (2001).
The amphipods Hyalella
azteca and Diporeia spp. were exposed to sediments dosed with dichlorodiphenyltrichloroethane
(DDT), and the toxicity and toxicokinetics were determined. The toxicity
was evaluated with the equilibrium partitioning (EqP) and critical body
residue approaches, The DDT in the sediments degraded during the equilibration
period prior to organism exposure. Thus, the toxicity using EqPpore-water
toxic units (TUs) was evaluated for DDT and its degradation product,
dichlorodiphenyldichloroethane (DDD), as the ratio of the predicted
interstitial water concentration divided by the water-only LC50 values.
The sum of TUs (STU) was assumed to best represent the toxicity of the mixture.
For H. azteca, the 10-d LC50 was 0.98 and 0.33 STU for two experiments. For Diporeia spp.,
no toxicity was found in the first experiment with up to 3 STU predicted in the interstitial water. However, in the
second experiment, the 28-d LC50 was 0.67 STU. These data suggest that the EqP approach approximately
predicts the toxicity for the combination of DDT and DDD in sediment,
provided a toxic unit approach is employed. The critical body residue
approach also used TUs because DDT is biotransformed by H. azteca
and because of the dual exposure to DDT and DDD. Because
biotransformation was only determined in the second experiment, the
critical body residue approach could only be evaluated for that case.
The TUs were calculated as the ratio of the concentration in the live
amphipods divided by the respective LR50 (residue concentration required
to produce 50% mortality) values. The LR50 was 1.1 STU for H. azteca for the 10-d exposure and 0.53 for Diporeia spp.
after a 28-d exposure. Thus, this approach was also quite successful
in predicting the toxicity. The accumulation and loss rates for H.
azteca were much greater than
for Diporeia spp. Thus, 10-d exposures represent steady-state conditions
for H. azteca, while even at 28-d, the Diporeia spp. are
not at steady state.
Surveys of benthic
macroinvertebrates conducted in Lake Ontario during 1994 and 1997 revealed
recent declines in populations of three major taxonomic groups: Oligochaeta,
Sphaeriidae, and Diporeia
spp. (Amphipoda), with the most drastic
reductions occurring in the latter. Results from sediment measurements
were used to classify deepwater sediments into three habitat zones.
Densities of all three taxa declined in the shallowest (12-88 m) of
the sediment zones between 1994 and 1997; the greatest changes in density
were observed for Diporeia, which declined from 3011 to 145 individuals
x m-2, and for total benthic macroinvertebrates, which declined
from 5831 to 1376 individuals x m-2. Mean densities of Dreissena
spp. In 1997 were highest in the shallowest zone, and the areas of greatest
densities corresponded to areas of largest reductions in Diporeia
populations. We believe that dreissenids are competing with Diporeia
by intercepting the supply of fresh algae essential for Diporeia
survival. A decline in macroinvertebrate densities, especially populations
of an important food item such as Diporeia, in Lake Ontario sediments
at depths of 12-88 m may have a detrimental impact on the benthic food
web.
Luo, J., K. J. Hartman,
S. B. BRANDT, C. F. Cerco, and T. H. Rippetoe. A spatially-explicit
approach for estimating carrying capacity: An application for the Atlantic
menhaden (Brevoortia tyrannus) in Chesapeake Bay. Estuaries 24(4):545-556
(2001).
A spatially-explicit
methodology was developed for estimating system carrying capacities
of fish stocks, and used to estimate the seasonal and spatial patterns
of carrying capacity of Chesapeake Bay for Atlantic menhaden (Brevoortia
tyrannus). We used a spatially-explicit
three-dimensional (3-D) model that divided the heterogeneous habitat
of Chesapeake Bay into over 4,000 cubes. Each cube represented a volume
of water that was characterized by a specific set of environmental variables
(phytoplankton biomass, temperature, and dissolved oxygen) driven by
the 3-D water quality model. Foraging and bioenergetics models transformed
the environmental variables into measures of potential growth rates
of menhaden. Potential carrying capacity of menhaden was estimated as
a function of phytoplankton production, menhaden consumption rate, and
potential growth rate, combining phytoplankton production, thermal habitat,
and menhaden physiology into one ecological value that is a measure
of habitat quality from the perspective of the fish. Seasonal analysis
of the Chesapeake Bay carrying capacity for Atlantic menhaden suggested
two bottleneck periods: one in early June and a second during the fall.
The fall bottleneck in carrying capacity was at about 10 billion age-0
fish. Annual recruitment of age-0 menhaden for the entire Atlantic coast
of the U.S. ranged from 1.2-18.6 billion fish between 1955 and 1986.
It appears that carrying capacity of Chesapeake Bay does not limit the
coastwide production of young menhaden. Any conditions such as nutrient
reduction strategies, further eutrophication, or global climatic warming,
that may influence the carrying capacity during the fall or early June
periods, may ultimately alter coastwide abundance of menhaden through
changes in Chesapeake Bay carrying capacity.
Magnuson, J. J., D. M.
Robertson, B. J. Benson, R. H. Wynne, D. M. Livingstone, T. Arai, R.
A. ASSEL, R. G. Barry, V. Card, E. Kuusisto, N. G. Granin, T. D. Prowse,
K. M. Stewart, and V. S. Vuglinski. Historical trends in lake and river
ice cover in the Northern Hemisphere. Science 289:1743-1746 (2000).
Freeze and breakup
dates of ice on lakes and rivers provide consistent evidence of later
freezing and earlier breakup around the Northern Hemisphere from 1846-1995.
Over these 150 years, changes in freeze dates averaged 5.8 days per
100 years later, and changes in breakup dates averaged 6.5 days per
100 years earlier; these translate to increasing air temperatures of
about 1.2 C per 100 years. Interannual variability on both freeze and
breakup dates has increased since 1950. A few longer time series reveal
reduced ice cover (a warming trend) beginning as early as the 16th century,
with increasing rates of change after about 1850.
MASON, D. M., A. Goyke,
S. B. BRANDT, and J. M. Jech. Acoustic fish stock assessment in the
Laurentian Great Lakes. In The Great Lakes of the World (GLOW): Food-web,
health and integrity, M. Munawar and R.E. Hecky (Eds.), Backhuys Publishers, Leiden,
The Netherlands, pp. 317-339 (2001).
Applications of underwater acoustics in the Great Lakes can be traced
back to the1960s. These early studies focused on fish distributions
at power plant thermal plumes (Spigarelli et al., 1973; Stuntz, 1973),
and on estimating zooplankton distribution and biomass (McNaught,
1968). During these early years, data assimilation consisted of a
paper chart recorder and an analog recording of output voltages on
magnetic tape. Even with limited technology, McNaught (1969) was one
of the first researchers, in marine or freshwater environments, to
propose and develop a multi-frequency sonar system for size-class
discrimination of zooplankton. Due to data storage and analysis limitations,
these early studies were completed on a localized scale. With technological
improvements in electronic and computer technology, larger scale surveys
were conducted on Lakes Michigan (Brandt, 1975, 1978, 1980; Brandt
et al., 1980; Janssen and Brandt, 1980), Huron (Argyle, 1982), and
Superior (Heist and Swenson, 1983) and provided the first quantitative
estimates of fish abundance, density, and spatial distribution. Using
a 50 kHz single beam scientific echo sounder and deconvolution techniques
(Peterson et al., 1976), Brandt (1980) studied the diel vertical migration,
thermal ecology, and spatial segregation of various life stages of
alewives in Lake Michigan. He found that alewife migrate to the thermocline
at night and disperse, and that adult and young-of-the year (YOY)
alewives thermally segregate. This information was the foundation
for nighttime assessment of alewives in the Great Lakes. Heist and
Swenson (1983) estimated rainbow smelt abundance in the western basin
of Lake Superior during 1978-1980 to provide prey fish numbers used
in reestablishing the native piscivore community and for assessing
the impact of an expanding commercial fisheries. Their acoustics application
was one of the first in the Great Lakes that focused on direct management
applications.
Long-term changes
in benthic macroinvertebrate populations have long been used to assess
trends in environmental conditions and trophic status in the Great Lakes
(for summary see Cook and Johnson 1974). Until the late 1960s/early
1970s, although some sensitive forms declined, the general trend was
particularly in the bays and nearshore areas. These increases reflected
increasing nutrient loads (phosphorus) and greater system productivity,
allowing greater inputs of organic materials to the benthic region.
This material served as food for the taxa most able to utilize this
resource. To reverse atrophic trends, phosphorus control measures were
implemented in the mid-1970s. By the early 1970s, overall productivity
declined in many areas and water quality improved as indicated by decreased
macroinvertebrate densities and a return of more sensitive taxa.
NALEPA, T. F., D. W. Schloesser,
S. A. POTHOVEN, D. HONDORP, D. L. FANSLOW, M. Tuchman, and G. Fleischer.
First finding of the amphipod Echinogammarus ischnus and
the mussel Dreissena bugensis
in Lake Michigan. Journal of Great Lakes Research 27(3):384-391
(2001).
The first finding
of the amphipod Echinogammarus ischnus and
the mussel Dreissena bugensis in
Lake Michigan is documented. These two species are widespread and abundant
in the lower lakes, but had not yet been reported from Lake Michigan.
E. ischnus is generally considered a warm-water form that is typically
associated with hard substrates and Dreissena clusters in the nearshore
zone. Along the eastern shoreline of Lake Michigan, this species was
present at rocky, breakwall habitats along the entire north-south axis
of the lake. Although not abundant, this species was also found at soft-bottomed
sites as deep as 94 m in the southern basin. The finding of this species
in deep offshore waters apparently extends the known habitat range for
this species in the Great Lakes, but it is found in deep water areas
within its native range (Caspian Sea). D. bugensis was
not abundant, but was present in both the southern and northern portions
of the lake. Individuals of up to 36 mm in length were collected, indicating
that it had probably been present in the lake for 2 or more years. Also
presented are depth-defined densities of D. polymorpha
at 37 sites in the Straits of Mackinac in 1997, and densities
at up to 55 sites in the southern basin in 1992/93 and 1998/99. Mean
densities decreased with increased water depth in both regions. Maximum
mean density in the Straits in 1997 was 13,700/m2 (<=10
m), and maximum density in the southern basin in 1999 was 2,100/m2
(<=30 m). Mean densities at the <=30-m interval in the southern
basin remained relatively unchanged between 1993 and 1999, but increased
from 25/m2 to 1,100/m2 at the 31 to 50 m interval
over the same time period. D. polymorpha was
rare at sites > 50 m. The presence of E. ischnus and the expected population expansion of D. bugensis
will likely contribute to further food-web changes in the lake.
Pichel, W. G., P. Clemente-Colon,
K. Friedman, A. C. Lunsford, G. A. LESHKEVICH, G. Hufford, C. Neigh,
W. Y. Tseng, R. N. Stone, and X. Li. CoastWatch applications of synthetic
aperture radar imagery. Journal of Advances in Marine Science and
Technology Society 4(2):147-154
(2000).
NOAA in partnership
with the National Ice Center has constructed a near real-time data delivery
system for SAR imagery. One of the principal applications of this imagery
is to support the mission of the NOAA CoastWatch program; i.e., to provide
near real-tie satellite data to environmental resource managers, fishery
scientists, and environmental analysts. There are two CoastWatch applications
of SAR imagery that are approaching operational status: (1) remote sensing
of ice on the Great lakes and in Alaska coastal waters, and (2) monitoring
of the spring ice break-u on Alaskan rivers. The status of these applications
will be presented. Also, the development status of other potential applications
of SAR data will be summarized, including (1) high-resolution wind measurements,
(2) mapping of oil spills, and (3) fisheries management.
The abundance and
life history characteristics of Mysis relicta were evaluated at an offshore
(110-m) and a nearshore (40 to 45-m) station during 1995, 1996, and
1998. Data were collected to monitor mysids relative to ongoing ecological
changes in Lake Michigan and as a comparison to studies from the 1970s
and 1980s. Mean densities of M. relicta during May through September
each year were higher offshore (210/m2 to 373/m2)
compared to nearshore (41/m2 to 168/m2). Growth
rates ranged between 0.026 to 0.041 mm/day and did not differ between
stations or with age. Juvenile mysids (< 10 mm) dominated the population,
and accounted for 30 to 90% of the catch. The size distribution of M.
relicta suggested that reproduction occurred year-round with the
most consistent influxes of juveniles in the spring (April through June)
each year; winter (February and March) and summer (July through September)
influxes of juveniles did not occur consistently each year. Mean length
of females with broods differed between nearshore (14 mm) and offshore
(16 mm). Brood size and the proportion of females with broods did not
differ between stations. Abundance estimates were equal or higher and
life history characteristics were similar to reported data from the
1970s and 1980s. However, ongoing declines in the benthic macroinvertebrate
Diporeia may result in higher fish predation pressure on M. relicta
in the near future.
ROBBINS, J. A., C. Holmes,
R. Halley, M. Bothner, E. Shinn, J. Graney, G. Keeler, M. tenBrink,
K. A. Orlandini, and D. Rudnick. Time-averaged fluxes of lead and fallout
radionuclides to sediments in Florida Bay. Journal of Geophysical
Research 105(C12):28805-28821 (2000).
Recent, unmixed sediments
from mud banks of central Florida Bay were dated using 210Pb/226Ra,
and chronologies were verified by comparing sediment lead temporal records
with Pb/Ca ratios in annual layers of coral (Montastrea annulari)
located on the ocean side of the Florida
Keys. Dates of sediment lead peaks (1978 +- 2) accord with prior observations
of a 6 year lag between the occurrence of maximum atmospheric lead in
1972 and peak coral lead in 1978. Smaller lags of 1-2 years occur between
the maximum atmospheric radionuclide fallout and peaks in sediment temporal
records of 137CS and Pu. Such lags are consequences of system
time averaging (STA) in which atmospherically delivered particle-associated
constituents accumulate and mix in a (sedimentary?) reservoir before
transferring to permanent sediments and coral STA model calculations.
using time-dependent atmospheric inputs. produced optimized profiles
in excellent accord with measured sediment 137CS, Pu, lead,
and coral lead distributions. Derived residence times of these particle
tracers (16 +- 1,15.7 +-; 0.7, 19 +- 3, and 16 +- 2 years, respectively)
are comparable despite differences in sampling locations, in accumulating
media, and in element loading histories and geochemical properties For
a 16 year weighted mean residence time, STA generates the observed 6
year lead peak lag. Evidently, significant levels of nondegradable,
particle-associated contaminants can persist in Florida Bay for many
decades following elimination of external inputs. Present results, in
combination with STA model analysis of previously reported radionuclide
profiles, suggest that decade-scale time averaging may occur widely
in recent coastal marine sedimentary environments.
We analyzed the relationship
between an index of Great Lakes winter severity (winters 1950-1998)
and atmospheric circulation characteristics. Classification and Regression
Tree analysis methods allowed us to develop a simple characterization
of warm, normal and cold winters in terms of teleconnection indices
and their combinations. Results are presented in the form of decision
trees. The single most important classifier for warm winters was the
Polar/Eurasian index (POL). A majority of warm winters (12 out of 15)
occurred when this index was substantially positive (POL > 0.23 ).
There were no cold winters when this condition was in place. Warm winters
are associated with a positive phase of the Western Pacific pattern
and El Nino events in the equatorial Pacific. The association between
cold winters and La Nina events was much weaker. Thus, the effect of
the El Nino/Southern Oscillation (ENSO ) on severity of winters in the
Great Lakes basin is not symmetric. The structure of the relationship
between the index of winter severity and teleconnection indices is more
complex for cold winters than for warm winters. It takes two or more
indices to successfully classify cold winters. In general, warm winters
are characterized by a predominantly zonal type of atmospheric circulation
over the Northern Hemisphere (type W1). Within this type of circulation
it is possible to distinguish two sub-types, W2 and W3, Sub-type W2
is characterized by a high-pressure cell over North America, which is
accompanied by enhanced cyclonic activity over the eastern North Pacific.
Due to a broad southerly "anomalous" flow, surface air temperatures
(SATs) are above normal almost everywhere over the continent. During
the W3 sub-type, the polar jet stream over North America, instead of
forming a typical ridge-trough pattern, is almost entirely zonal, thus
effectively blocking an advection of cold Arctic air to the south. Cold
winters tend to occur when the atmospheric circulation is more meridional
(type C1). As with warm winters, there are two sub-types of circulation,
C2 and C3. In the case of C2, the jet stream loops southward over the
western part of North America, but its northern excursion over the eastern
part is suppressed. In this situation, the probability of a cold winter
is higher for Lake Superior than for the lower Great Lakes. Sub-type
C3 is characterized by an amplification of the climatological ridge
over the Rockies and the trough over the East coast. The strongest negative
SAT anomalies are located south of the Great Lakes basin so that the
probability of a cold winter is higher for the lower Great lakes than
for Lake Superior.
RODIONOV, S., and R. A.
ASSEL. A new look at the Pacific/North American index. Journal of
Geophysical Research Letters 28(8):1519-1522 (2001).
This study examines
inconsistencies in the Pacific/North American (PNA) index relative to
atmospheric circulation over North America. Two types of atmospheric
circulation were found to be associated with high PNA values. The first
type is the true PNA pattern characterized by an amplified ridge-trough
system. It appears to be related to the leading mode of sea surface
temperature variability in the North Pacific. The second type is observed
during El Nino events It is characterized by a flattening of the polar
jet stream and southward shift of the subtropical jet stream The recognition
of these two types of the PNA index improves our understanding of the
relative role of to El Nino /Southern Oscillation events and sea surface
temperatures in the North Pacific in affecting winter atmospheric circulation
over North America.
Schloesser, D. W., and
T. F. NALEPA. Changing abundance of Hexagenia mayfly nymphs
in western Lake Erie of the Laurentian Great Lakes: Impediments to assessment
of lake recovery? International Revue Hydrobiologie 86(1):87-103 (2001).
After an absence
of 40 years, mayfly nymphs of the genus Hexagenia were
found in sediments of western Lake Erie of the Laurentian Great Lakes
in 1993 and, by 1997, were abundant enough to meet a mayfly-density
management goal (ca. 350 nymphs m2) based on pollution-abatement
programs. We sampled nymphs in western Lake Erie and Lake St. Clair,
located upstream of western Lake Erie, to determine the importance of
seasonal abundance and life-history characteristics of nymphs (e.g.,
emergence and recruitment) on density estimates relative to the mayfly-density
management goal. Two types of density patterns were observed (1) densities
were relatively high in spring and gradually decreased through late
summer (observed in Lake Erie and Lake St Clair in 1997 and Lake St
Clair in 1999), and (2) densities were relatively high in spring, gradually
decreased to mid summer, abruptly decreased in mid summer, and then
increased between summer and late fall (Lake Erie and Lake St. Clair
in 1998 and Lake Erie in 1999). Length-frequency distributions of nymphs
and observations of adults indicate that the primary cause for the two
density patterns was attributed to failed (first pattern) and successful
(second pattern) reproduction and emergence of nymphs into adults in
mid summer. Gradual declines in densities were attributed to mortality
of nymphs. Our results indicate that caution should be used when evaluating
progress of pollution-abatement programs based on mayfly densities because
recruitment success is variable both between and within years. Additionally,
the interpretation of progress toward management goals, relative to
the restoration of Hexagenia populations
in the Great Lakes and possibly other water bodies throughout the world,
is influenced by the number of years in which consecutive collections
are made.
Detroit River flows
are important to the Great Lakes water resources. Changes in these flows
affect hydropower usage, navigational activities, and shoreline profiles
to name a few. The spread of zebra mussels into the Great Lakes system
led to increased clarity of the water in Lakes St. Clair and Erie and
the Detroit River due to their filter feeding habits. This increased
clarity could amplify aquatic weed growth since light is able to penetrate
deeper into the water column and increase the photosynthetic process.
Increased weed growth acts to increase the hydraulic roughness of the
Detroit River during the growing season, thus changing the river's hydraulic
properties. As Detroit River flows are used in a wide variety of water
resource studies, it is important to quantify both the amount and the
seasonal distribution of the weeds and the increase in roughness due
to the impact of the zebra mussel.
Silliman, J. E., P. A.
Meyers, B. J. EADIE, and J. V. Klump. A hypothesis for the origin of
perylene based on its low abundance in sediments of Green Bay, Wisconsin.
Chemical Geology 177:309-322 (2001).
Perylene, a polycyclic
aromatic hydrocarbon (PAH) that is common in sediments is believed to
originate principally from anaerobic diagenesis of organic matter, but
its precursor material remains enigmatic. We have investigated the formation
of perylene in a dated sediment core from Green Bay, WI. Comparisons
of sedimentary profiles of perylene, anthropogenic PAHs, land-plant-derived
hydrocarbons, and aquatic contributions of organic matter rule out a
specific industrial, terrigenous, or aquatic precursor for perylene.
Instead, perylene seems to be formed from any kind of organic matter
as a consequence of a specific type of microbial activity in sub-bottom
sediments. Despite an abundance of organic matter, the amount of perylene
is low in Green Bay and in other organic-carbon-rich lake sediments.
The abundant availability of organic matter that stimulates microbial
activity in Green Bay sediments would seem to favor perylene formation
in such sediments. We therefore hypothesize that the microorganisms
responsible for perylene formation do not compete successfully with
those that flourish in sediments rich in organic matter. Perylene formation
consequently does not become significant until deeper in sediments after
the more-reactive types of organic matter have been consumed.
Silliman, J. E., P. A.
Meyers, P. H. Ostrom, N. E. Ostrom, and B. J. EADIE. Insights into the
origin of perylene from isotopic analyses of sediments from Saanich
Inlet, British Columbia. Organic Geochemistry 31:1133-1142 (2000).
Perylene is an abundant
and common polycyclic aromatic hydrocarbon in sedimentary settings,
yet its origin remains puzzling. We have investigated the relation of
perylene to the amount and type of organic matter in the sediments of
Saanich Inlet, a coastal marine anoxic basin. Organic matter is predominantly
marine in origin, but the proportions of marine and land-derived components
have varied. Perylene concentrations generally increase with sediment
depth, relative to TOC, which indicates continued formation of this
compound by microbially mediated diagenesis. Perylene dl3C values range between -27.7 and -23.6 0/00, whereas
TOC dl3C values vary narrowly from -21.7 to -21.2 0/00
over the same sediment depth interval. The variation in isotopic difference
suggests that perylene originates from more than one precursor material,
both aquatic and continental organic matter, different microbial processes,
or some combination of these possibilities.
Swihart, R. K., Z. Feng,
N. A. Slade, D. M. MASON, and T. M. Gehring. Effects of habitat destruction
and resource supplementation in a predator-prey metapopulation model.
Journal of Theoretical Biology 210:287-303
(2001).
We developed a mean
field, metapopulation model to study the consequences of habitat destruction
on a predator-prey interaction. The model complements and extends earlier
work published by Bascompte and Sole (1998, J. Theor. Biol. 195,
383-393) in that it also permits use of alternative prey (i.e., resource
supplementation) by predators. The current model is stable whenever
coexistence occurs, whereas the earlier model is not stable over the
entire domain of coexistence. More importantly, the current model permits
an assessment of the effect of a generalist predator on the trophic
interaction. Habitat destruction negatively affects the equilibrium
fraction of patches occupied by predators, but the effect is most pronounced
for specialists. The effect of habitat destruction on prey coexisting
with predators is dependent on the ratio of extinction risk due to predation
and prey colonization rate. When this ratio is less than unity, equihbrial
prey occupancy of patches declines as habitat destruction increases.
When the ratio exceeds one, equihbrial prey occupancy increases even
as habitat destruction increases; i.e., prey "escape" from predation
is facilitated by habitat loss. Resource supplementation reduces the
threshold colonization rate of predators necessary for their regional
persistence, and the benefit derived from resource supplementation increases
in a nonlinear fashion as habitat destruction increases. We also compared
the analytical results to those from a stochastic, spatially explicit
simulation model. The simulation model was a discrete time analog of
our analytical model, with one exception. Colonization was restricted
locally in the simulation, whereas colonization was a global process
in the analytical model. After correcting for differences between nominal
and effective colonization rates, most of the main conclusions of the
two types of models were similar. Some important differences did emerge,
however, and we discuss these in relation to the need to develop fully
spatially explicit analytical models. Finally, we comment on the implications
of our results for community structure and for the conservation of prey
species interacting with generalist predators.
TYLER, J. A., and S. B.
BRANDT. Do spatial models of growth rate potential reflect fish growth
in a heterogeneous environment? A comparison of model results. Ecology
of Freshwater Fish 10:43-56 (2001).
Spatial models of fish growth rate potential have
been used to characterize a variety of environments including estuaries,
the North American Great Lakes, small lakes and rivers. Growth rate
potential models capture a snapshot of the environment but do not include
the effects of habitat selection or competition for food in their measures
of environment quality. Here, we test the ability of spatial models
of fish growth rate potential to describe the quality of an environment
for a fish population in which individual fish may select habitats and
local competition may affect per capita intake. We compare growth rate
potential measurements to simulated fish growth and distributions of
model fish from a spatially explicit individual-based model offish foraging
in the same model environment. We base the model environment on data
from Lake Ontario and base the model fish population on alewife in the
lake. The results from a simulation experiment show that changes in
the model environment that caused changes in the average growth rate
potential correlated extremely highly (r2>=0.97) with changes in
simulated fish growth. Unfortunately, growth rate potential was not
a reliable quantitative predictor of simulated fish growth nor of the
fish spatial distribution. The inability of the growth rate potential
model to quantitatively predict simulated fish growth and fish distributions
results from the fact that growth rate potential does not consider the
effects of habitat selection or of competition on fish growth or distribution,
processes that operate in our individual-based model and presumably
also operate in nature. The results, however, do support the use of
growth rate potential models to describe the relative quality of habitats
and environments for fish populations.
VAN HOOF, P. L., J. V.
Kukkonen, and P. F. LANDRUM. Impact of sediment manipulation on the
bioaccumulation of polycyclic aromatic hydrocarbons from field-contaminated
and laboratory-dosed sediments by an oligochaete. Environmental Toxicology
and Chemistry 20(8):1752-1761
(2001).
The accumulation
kinetics of polycyclic aromatic hydrocarbons (PAHs) by the freshwater
oligochaete Lumbriculus variegatus were
measured for field-contaminated and laboratory-dosed sediment. In addition,
sediment manipulations typically used for homogenization and dosing
in bioaccumulation assays were compared. Rather than an asymptotic approach
to steady state, both resident and dosed PAH accumulation exhibited
a peak during the 14-d assays, with steeper declines being noted for
the lower molecular-weight compounds. Lack of evidence of a peak for
higher-molecular-weight PAHs may be due to slower kinetics and the short
length of the assay. Relative to minimally mixed sediment, slurried
sediment enhanced the accumulation of less-soluble resident PAHs, did
not affect moderately soluble PAHs, and reduced the uptake of the more-soluble
PAHs, fluorene and phenanthrene. Aging sediment after mixing reduced
the availability of highly to moderately soluble resident PAHs but had
no effect on less soluble PAHs. A similar effect was noted for dosed
PAHs, though a larger reduction in bioavailability was observed. Dosed
PAH uptake clearance coefficients (ks) exceeded those of minimally mixed
resident PAHs by factors of 3 to 4 for pyrene and 26 for benzo[a]pyrene.
These results demonstrate that sediment manipulations and contamination
history need to be considered when measuring PAH bioaccumulation.
VANDERPLOEG, H. A., J. R. LIEBIG, W. W. Carmichael, M.
A. AGY, T. H. JOHENGEN, G. L. FAHNENSTIEL, and T. F. NALEPA. Zebra mussel
(Dreissena polymorpha) selective filtration promoted toxic
Microcystis bloom in Saginaw Bay (Lake Huron) and Lake
Erie. Canadian Journal of Fisheries and Aquatic Sciences
58(6):1208-1221 (2001). http://www.glerl.noaa.gov/pubs/fulltext/2001/20010004.pdf
Microcystis aeruginosa, a planktonic colonial cyanobacterium, was not abundant
in the 2-year period before zebra mussel (Dreissena polymorpha) establishment in Saginaw Bay (Lake Huron) but became abundant
in three of five summers subsequent of mussel establishment. Using novel
methods, we determined clearance, capture, and assimilation rates for
zebra mussels feeding on natural and laboratory M. aeruginosa
strains offered alone or in combination with other algae. Results
were consistent with the hypothesis that zebra mussels promoted blooms
of toxic M. aeruginosa in
Saginaw Bay, western Lake Erie, and other lakes through selective rejection
in pseudofeces. Mussels exhibited high feeding rates similar to those
seen for a highly desirable food alga (Cryptomonas)
with both large (>53 um) and small 53 um) colonies of a nontoxic
and a toxic laboratory strain of M. aeruginosa known to cause blockage of feeding in zooplankton.
In experiments with naturally occurring toxic M. aeruginosa
from Saginaw Bay and Lake Erie and a
toxic isolate from Lake Erie, mussels exhibited lowered or normal filtering
rates with rejection of M. aeruginosa in
pseudofeces. Selective rejection depended on "unpalatable" toxic strains
of M. aeruginosa occurring as large colonies that could be rejected efficiently
while small desirable algae were ingested.
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