GLERL Publications Abstracts: FY 1996

ASSEL, R.A.(among 27 others). The Cryosphere: changes and their impacts. In Climate Change 1995: Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses, R. Watson, M. Zinyowera , R. Moss, D. Dokken (eds.). Cambridge University Press, New York, NY, 245-265 (1996).

No abstract.

ASSEL, R.A., J.E. Janowiak, S. Young, and D. Boyce. Winter 1994 weather and ice conditions for the Laurentian Great Lakes. Bulletin of the American Meteorological Society 77(1):71-88 (1996).

The Laurentian Great Lakes developed their most extensive ice cover in over a decade during winter 1994 [December-February 1993/94 (DJF 94)]. Extensive midlake ice formation started the second half of January, about 2 weeks earlier than normal. Seasonal maximal ice extent occurred in early February, again about 2 weeks earlier than normal. Winter 1994 maximum (normal ice coverages on the Great Lakes are Lake Superior 96% (75%), Lake Michigan 78% (45%), Lake Huron 95% (68%), Lake Erie 97% (90%), and Lake Ontario 67% (24%). Relative to the prior 31 winters (I963-93), the extent of seasonal maximal ice cover for winter 1994 for the Great Lakes taken as a unit is exceeded by only one other winter (1979); however, other winters for individual Great Lakes had similar maximal ice covers.

Anomalously strong anticyclonic circulation over the central North Pacific (extending to the North Pole) and an abnormally strong polar vortex centered over northern Hudson Bay combined to produce a circulation pattern that brought frequent air masses of Arctic and polar origin to the eastern third of North America. New records were set for minimum temperatures on 19 January 1994 at many locations in the Great Lakes region. A winter severity index consisting of the average November-February air temperatures averaged over four sites on the perimeter of the Great Lakes (Duluth, Minnesota; Sault Ste. Marie, Michigan; Detroit, Michigan; and Buffalo, New York) indicates that winter 1994 was the 21st coldest since 1779. The unseasonably cold air temperatures produced much-above-normal ice cover over the Great Lakes and created problems for lake shipping. Numerous fatalities and injuries were attributed to the winter weather, which included several ice and snow storms. The much-below-normal air temperatures resulted in enhanced lake-effect snowfall along downwind lake shores, particularly during early to midwinter, prior to extensive ice formation in deeper lake areas. The low air temperatures were also responsible for record 1-day electrical usage and multimillion dollar costs associated with snow removal, U.S. and Canadian Coast Guard operational assistance to ships beset in ice, damage to ships by ice, damage to public and private property by river ice jams and associated flooding, frozen underground water pipes, and damage to fruit trees.

ASSEL, R.A., D.M. Robertson, M.H. Hoff, and J.H. Selgeby. Climatic change implications from long-term (1823-1994) ice records for the Laurentian Great Lakes. Annals of Glaciology 21:383-386 (1995).

Long-term ice records (1823-1994) from six sites in different parts of the Laurentian Great Lakes region were used to show the type and general timing of climatic changes throughout the region. The general timing of both freeze-up and ice loss varies and is driven by local air temperatures, adjacent water bodies and mixing, and site morphometry. Grand Traverse Bay and Buffalo Harbor represent deeper water environments affected by mixing of off-shore waters; Chequamegon Bay, Menominee, Lake Mendota, and Toronto Harbor represent relatively shallow-water, protected environments. Freeze-up dates gradually became later and ice-loss dates gradually earlier from the start of records to the 1890s in both environments, marking the end of the "Little Ice Age." After this, freeze-up dates remained relatively constant, suggesting little change in early-winter air temperatures during the 20th century. Ice-loss dates at Grand Traverse Bay and Buffalo Harbor (but not at the other sites) became earlier during the 1940s and 1970s and became later during the 1960s. The global warming of the 1980s was marked by a trend toward earlier ice-loss dates in both environments.

ASSEL, R.A., C.E. SELLINGER, D.E. MEYER, R.N. KELLEY, and P. Grimm. Great Lakes states monthly average temperature dataBeginning of record to 1990. NOAA Technical Memorandum ERL GLERL-88, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-125604/XAB) 51 pp. (1995).

Monthly average temperature data were digitized from the National Climatic Data Center (NCDC) publication Climatological Data from beginning of record to 1930 for the states bordering the Great Lakes. Monthly temperature data from 1931 to 1947 for all Great Lakes states (except New York) were combined with previously digitized NCDC monthly data (Tape Deck 3220). New York State's monthly temperature data from 1931 to 1947 were not available from NCDC for this period, and so these data were digitized from Climatological Data. The monthly temperature data prior to 1948 for all Great Lakes states were combined with NCDC Tape Deck 3200 temperature data from 1948 to 1990 (monthly average temperatures were calculated for the TD 3200 daily data). A list containing station name, latitude, longitude, elevation, and period of record is given as an appendix. Data reduction, verification, quality control, and analysis methods are summarized. The spatial and temporal distribution patterns of the number of stations is presented. The digital data are available from NCDC.

BEETON, A.M., R.E. Holland, T.H. JOHENGEN, and J.R. Hageman. Chemistry, temperature, and Secchi disc data for Hatchery Bay, Western Lake Erie. NOAA Technical Memorandum ERL GLERL-92, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-203203/XAB) 15 pp. (1996).

This Technical Memorandum presents the sampling and analytical methods, and the resulting data from weekly, year round sampling in Hatchery Bay, western Lake Erie, from 1984 to 1987 and 1990 to 1995. Results are presented in tables. Most of the Secchi disc data are referred to in a paper on diatoms (Holland, 1993). The chemistry data for 1984-87 and 1990-93 are the basis for a paper on nutrient chemistry trends for pre and post zebra mussel invasion (Holland et al., 1995).

BEETON, A.M., and J.H. SAYLOR. Limnology of Lake Huron. In The Lake Huron Ecosystem: Ecology, Fisheries, and Management, M. Munawar, T. Edsall, J. Leach (eds.). SPB Academic Publishing, Amsterdam, The Netherlands, 1-37 (1995).

No abstract.

BRIDGEMAN, T.B., G.L. FAHNENSTIEL, G.A. LANG, and T.F. NALEPA. Zooplankton grazing during the zebra mussel (Dreissena polymorpha) colonization of Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):567-573 (1995).

Weight-specific zooplankton filtering rates were determined at three sites in Saginaw Bay during the period of maximum zooplankton abundance prior to and after the establishment of zebra mussel colonies (June 1991 and June 1992). Biomass-specific filtering rates were similar in both years (inner bay: 0.24-0.33 mL mg dry wt-1 d-1; outer bay: 1.27-1.83 mL mg dry wt.-1 d-1), but large decreases in zooplankton biomass resulted in a decrease, on average, of 58% in community filtering rates between years. As part of a large-scale monitoring program, zooplankton abundance and biomass estimates were also recorded at 13 sites during May-August of both years. Mean biomass in the inner bay was 40% lower in 1992 than in 1991, and in the outer bay, mean biomass was 70% lower in 1992 than in 1991. Zooplankton community composition was the same in both years. We estimated the time required to clear the water volume of the inner bay during the May-June period to be 17 days in 1991 and 37 days in 1992. For these two periods, decreased zooplankton numbers and community filtering rates indicate that grazing by zooplankton was likely not responsible for noted declines in phytoplankton abundance and productivity.

Bronte, C.R., J.H. Selgeby, J.H. SAYLOR, G.S. MILLER, and N.R. Foster. Hatching, dispersal, and bathymetric distribution of Age-0 Wild Lake Trout at the Gull Island Shoal Complex, Lake Superior. Journal of Great Lakes Research 21(Supplement 1):233-245 (1995).

We studied age-0 lake trout (Salvelinus namaycush) associated with spawning and nursery areas of the Gull Island Shoal complex in western Lake Superior. Post-emergent age-0 lake trout were captured on rocky spawning substrate with a 3-m beam trawl and at the nursery area with a bottom trawl from June to September 1990 and June to August 1991. Catch data suggested that age-0 lake trout move distances of 7-11 km to the nursery area over a 3-month period. Water currents, measured at Gull Island Shoal, may be a part of the transport mechanism. Examination of daily-growth increments on the sagittae and back-calculation from the date of capture revealed that most fish hatched between 6 June and 19 July in 1990 and between 30 April and 30 May in 1991. The duration of the hatch was 100 days in 1990 and 120 days in 1991, and the estimated incubation period is about 7 months for lake trout eggs at this site. Similar hatch-date distributions of age-0 captured on different sampling dates suggested that natural mortality was low.

Burton, G.A., C.G. Ingersoll, L.C. Burnett, M. Henry, M.L. Hinman, S.J. Klaine, P.F. LANDRUM, P. Ross, and M. Tuchman. A comparison of sediment toxicity test methods at three Great Lakes areas of concern. Journal of Great Lakes Research 22(30):495-511 (1996).

The significance of sediment contamination is often evaluated using sediment toxicity (bioassay) testing. There are relatively few "standardized" test methods for evaluating sediments. Popular sediment toxicity methods examine the extractable water (elutriate), interstitial water, or whole (bulk) sediment phases using test species spanning the aquatic food chain from bacteria to fish. The current study was designed to evaluate which toxicity tests were most useful in evaluations of sediment contamination at three Great Lakes Areas of Concern. Responses of 24 different organisms including fish, mayflies, amphipods, midges, cladocerans, rotifers, macrophytes, algae, and bacteria were compared using whole sediment or elutriate toxicity assays. Sediments from several sites in the Buffalo River, Calumet River (Indiana Harbor), and Saginaw River were tested as part of the U.S. Environmental Protection Agency's (USEPA) Assessment and Remediation of Contaminated Sediments (ARCS) project. Results indicated several assays to be sensitive to sediment toxicity and able to discriminate between differing levels of toxicity. Many of the assay responses were significantly correlated to other toxicity responses and were similar based on factor analysis. For most applications, a test design consisting of two to three assays would adequately detect sediment toxicity, consisting of various groupings of the following species: Hyalella azeca, Ceriodaphnia dubia, Chironomus riparius, Chironomus tentans, Daphnia magna, Pimephales promelas, Hexagenia bilineata, Diporeia sp., Hydrilla verticillata, or Lamna minor.

CARRICK, H.J., and G.L. FAHNENSTIEL. Common Planktonic Protozoa in the Upper Great Lakes: An Illustrated Guide. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 72 pp. (1995).

No abstract.

Cotner, J.B., W.S. GARDNER, J.R. JOHNSON, R.H. Sada, J.F. CAVALETTO, and R.T. Heath. Effects of zebra mussel (Dreissena polymorpha) on bacterioplankton: Evidence for both size-selective consumption and growth stimulation. Journal of Great Lakes Research 21(4):517-528 (1995).

Zebra mussels had significant direct and possible indirect effects on heterotrophic bacteria in two contrasting sites in Saginaw Bay. At a eutrophic site in the inner portion of Saginaw Bay, mussels fed directly on bacterial-sized particles and had a negative impact on bacterial abundances. Mussels removed large bacteria (> 0.9 mm) more effectively than small bacteria at this site. Individual mussels cleared from 37-89 mL per day. Results using different sizes of fluorescent microspheres suggest that zebra mussels have a lower limit for particle size removal that is less than 0.4 mm. Contradictory to inner bay results, mussels at an outer bay oligotrophic site had a positive impact on heterotrophic bacterial abundance perhaps as a result of indirect effects such as nutrient or organic carbon excretion by the mussels. Differences in the impact of mussels on the bacterial communities of the inner bay and outer bay probably result from differences in trophic state and bacterial community structure. A hypothesized smaller size of bacteria at outer bay sites may enable them to escape heavy predation pressure from mussels and the high rates of mussel nutrient excretion may facilitate their growth in these nutrient depleted conditions.

CROLEY, T.E.II. Using NOAA's new climate outlooks in operational hydrology. Journal of Hydrologic Engineering July 1996:93-102 (1996).

The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center recently began issuing new multiple long-lead outlooks of meteorological probabilities. Operational hydrology approaches for generating probabilistic hydrological outlooks must be compatible with these meteorological outlooks yet preserve spatial and temporal relationships observed in past meteorology. Many approaches, however, either limit the use of historical data to be compatible with meteorological outlooks or limit compatibility with the outlooks to allow fuller use of historical data. An operational hydrology approach that uses all historical data while remaining compatible with many of the new long-lead outlooks, in order of user priority, is described here. The approach builds a hypothetical very large structured set of possible future scenarios, to be treated as a "sample" from which to estimate outlook probabilities and other parameters. The use of this hypothetical, set corresponds to the weighted use of a scenario set based on historical data. The determination of weights becomes an optimization problem for the general case. An example illustrates the concepts and method.

CROLEY, T.E.II, and K.E. Kunkel. Application of the new NWS climate outlook in operational hydrology. Proceedings, 13th Conference on Probability and Statistics in the Atmospheric Sciences, San Francisco, CA, February 21-23, 1996. American Meteorological Society, Boston, MA, 231-238 (1996).

Many forecasters used hydrology models with climatology and the now-discontinued Monthly and Seasonal Weather Outlook to make outlooks of basin water supplies. The new Climate Outlook of the National Weather Service (NWS) estimates temperature and precipitation probabilities for multiple extended lead times and offers an opportunity to improve water supply forecasts. We developed a system to use the new Climate Outlook multiple probabilities to calculate appropriate weighting factors for historical climate scenarios. We describe here the new Climate Outlook and its use with hydrology models to make probabilistic outlooks. We derive statistics that use the weights determined from the Climate Outlook, and we formulate and solve an optimization for finding the weights. We illustrate with an example and discuss the implications.

CROLEY, T.E.II, F.H. QUINN, K.E. Kunkel, and S.A. Changnon. Climate transposition effects on the Great Lakes hydrological cycle. NOAA Technical Memorandum ERL GLERL-89, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB96-146089/XAB) 100 pp. (1996).

Historical climate scenarios, based on 41-yr data periods from the southeastern and southwestern continental United States, were used in hydrological models of the Great Lakes to examine possible changes in variability associated with various hydrological conditions. The Great Lakes Environmental Research Laboratory (GLERL) used their conceptual models for simulating moisture storages in, and runoff from, the 121 watersheds draining into the Laurentian Great Lakes, over-lake precipitation into each lake, and the heat storages in, and evaporation from, each lake. GLERL combined these components as net water supplies for each lake and estimated lake levels and connecting channel flows to consider transposed climate scenarios. We transposed four climate zones, ranging from 6° south and 0° west to 10° south and 11° west of the Great Lakes, to the Great Lakes area. These represent analog climates that could occur over the Great Lakes basin under global warming. This transposition of actual climates was essential since it incorporates natural changes in variability within the existing climate; this is not true for GCM-generated corrections applied to existing historical data in many other hydrological impact assessment studies. Average air temperatures increased between 4 and 11°C, and precipitation ranged from 80% to +170% of the current climate, over various lakes under various scenarios. These resulted in Great Lakes whole-basin water supply changes from the current condition of -1% to -54%. The higher air temperatures under the transposed climate scenarios led to higher over-land evapotranspiration and lower runoff to the lakes with earlier runoff peaks, since snowpack is reduced up to 100%, and the snow season is eliminated in some scenarios. This also resulted in a reduction in available soil moisture. Water temperatures increased and peaked earlier; heat resident in the deep lakes increased throughout the year. Mixing of the water column diminished, as most of the lakes become mostly monomictic, and lake evaporation increased. Water supplies decreased dramatically for the two driest scenarios with Lake Superior becoming a terminal lake. Also, lake level variability increased for all lakes for most of the scenarios. Maximum lake levels exceeded the recorded maximums for several scenarios on the lower lakes.

FAHNENSTIEL, G.L., T.B. BRIDGEMAN, G.A. LANG, M.J. McCORMICK, and T.F. NALEPA. Phytoplankton productivity in Saginaw Bay, Lake Huron: Effects of zebra mussel (Dreissena polymorpha) colonization. Journal of Great Lakes Research 21(4):465-475 (1995).

Phytoplankton photosynthesis-irradiance parameters, chlorophyll concentrations, underwater extinction coefficients (kPAR), and surface irradiance were determined at 8-10 sites on 27 occasions in Saginaw Bay from spring 1990 through fall 1993 corresponding to a period before and after the establishment of large zebra mussel populations (began in summer 1991). Similar measurements, with the exception of the photosynthetic parameter, a, had also been made in 1974/75 at eight sites on nine occasions. In inner Saginaw Bay where zebra mussels were primarily found, chlorophyll and kPAR values decreased, while the photosynthetic parameters, Pmax and a increased after zebra mussel colonization. At sites in the outer bay where no zebra mussels were found, chlorophyll and kPAR values did not change after zebra mussel colonization, whereas photosynthetic parameters increased. Decreases in chlorophyll and KPAR in the inner bay were related to the zebra mussel, but increases in photosynthetic parameters in both the inner and outer bay were not. Areal-integrated and volumetric phytoplankton productivity decreased by 38% and 37%, respectively, in inner Saginaw Bay after the establishment of zebra mussels; phytoplankton productivity at outer bay control sites was similar during the same period. Decreased phytoplankton productivity in the inner bay was attributable to the large decrease in chlorophyll as increases in underwater irradiance (increased kPAR) and photosynthetic parameters could not compensate for the chlorophyll effect. Increase in underwater irradiance produced a significant increase in light to the benthic region and contributed to increased benthic primary productivity; ratio of photic zone to station depth increased in inner Saginaw Bay, from 0.6-0.8 before the zebra mussel colonization (1974-1990) to 1.1-1.3 after colonization (1992-1993). Overall, primary productivity in the inner bay did not exhibit a notable change after zebra mussel colonization as decreases in phytoplankton productivity were accompanied by increases in benthic primary productivity. Thus, zebra mussels altered inner Saginaw Bay from a pelagic-dominated system to a benthic/pelagic system which will have long-term effects on food web structure and productivity at higher trophic levels.

FAHNENSTIEL, G.L., G.A. LANG, T.F. NALEPA, and T.H. JOHENGEN. Effects of zebra mussel (Dreissena polymorpha) colonization on water quality parameters in Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):435-448 (1995).

A large-scale study of Saginaw Bay was initiated in 1990 and continued through 1993 to examine the effects of the zebra mussel colonization which began in summer/fall 1991. Saginaw Bay responded quickly to the zebra mussel colonization, as fall 1991 values of chlorophyll were similar to 1992 and 1993 vallues. In inner Saginaw Bay, where most zebra mussels were found, chlorophyll, kPAR, and total phosphorus values decreased, and Secchi disk depth increased during the study period, regardless of the presence or absence of zebra mussels at a specific station. At outer bay control stations no significant differences were found for chlorophyll, kPAR, and Secchi disk values. In order to examine longer-term trends, water quality data from 1979-1980 (STORET) were combined with our 1990 data (pre-zebra mussel period) and compared to values from the post zebra mussel period (fall 1991, all 1992 and 1993). At stations with high densities of zebra mussels, chlorophyll and total P decreased by 66% and 48%, respectively, and Secchi disk values increased 88%. At outer bay control stations no significant differences were found for chlorophyll or Secchi disk when parameters were averaged throughout inner Saginaw Bay, zebra mussels caused a 59% and 43% decrease in chlorophyll and in total phosphorus and a 60% increase in Secchi disk transparency. Although zebra mussels significantly altered water quality parameters in the pelagic region of Saginaw Bay, they did not necessarily change system trophic state; rather they altered the spatial partitioning of resources.

FANSLOW, D.L., T.F. NALEPA, and G.A. LANG. Filtration rates of the zebra mussel (Dreissena polymorpha) on natural seston from Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):489-500 (1995).

Filtration rates of the zebra mussel (Dreissena polymorpha) oil natural seston from two different regions in Saginaw Bay were determined on a monthly basis from April to October in 1992 and 1993. The two regions represent contrasting trophic conditions, with the inner bay more eutrophic than the outer bay. Mean filtration rate was 16.2 mL/mg/h (range 4.0 to 40.7 mL/mg/h) over the entire 2-year period. Filtration rates on seston from the inner bay were significantly lower than rates on seston from the outer bay in 1992, but no differences were apparent in 1993. Lower rates were attributed to higher concentrations of seston (chlorophyll, particulate organic carbon, and total suspended solids) found in the inner bay in 1992. In 1992, overall filtration rates were related to seston concentrations as described by a negative exponential function. In 1993, seston concentrations were uniformly low, and a relationship between filtration rates and concentrations was not observed. Further, filtration rates were not related to seston composition, as determined by the ratio of POC:TSS and chl:TSS. Maximum filtration rates were apparently related to temperature, with highest maximum rates occurring at 10-20oC. Based on measured filtration rates and overall standing stocks, the Dreissena population in the inner bay was capable of filtering the volume of the inner bay 1.3 times per day in 1992 and 0.2 times per day in 1993.

GARDNER, W.S., R. Benner, R.M.W. Amon, J.B. Cotner, J.F. CAVALETTO, and J.R. JOHNSON. Effects of high molecular-weight dissolved organic matter on nitrogen dynamics in the Mississippi River plume. Marine Ecology Progress Series 133:287-297 (1996).

The dynamics of N and its interactions with labile dissolved organic C (DOC), bacteria, and phytoplankton were studied to determine potential effects of dissolved organic matter (DOM) and light on N dynamics in surface waters of the Mississippi River (USA) plume in the Gulf of Mexico. Bacterial uptake of added labeled N compounds (15NH4+ or 15N-labeled dissolved free amino acids, DFAA) was stimulated more by high-molecular-weight (HMW, >1 kDa) DOM than by low-molecular-weight (LMW, <1 kDa) DOM. An index that inversely indicated the presence of labile DOC was defined as the fraction of assimilated Amino acid-15N that was recovered as 15N-Ammonium (ANRA), following the additions of high-levels (4 mM) of 15N-DFAA. ANRA ratios were high in the absence of other available carbon sources because heterotrophic bacteria were forced to use the added amino acids as a carbon source for respiration rather than as a nutrient source for biomass formation. In dynamic light/dark experiments, conducted with in situ populations of organisms, uptake rates of added 15NH4+ were significantly enhanced both by the presence of light and by the addition of HMW DOM. Uptake rates of added 15N-labeled DFAA were increased by the addition of HMW DOM but not by light. ANRA ratios were consistently lower in the presence of added HMW DOM than in controls. Added HMW DOM thus appeared to stimulate the incorporation of assimilated DFAA into bacterial biomass. Bacterial growth rates were relatively high in both light and dark bottles with DFAA additions and in light bottles with HMW DOM plus NH4+ additions, but they remained comparatively low in dark bottles with added NH4+ These results are consistent with the idea that bacterial N dynamics in these euphotic waters may be tightly coupled to photosynthetic activities over short time scales.

GARDNER, W.S., J.F. CAVALETTO, T.H. JOHENGEN, J.R. JOHNSON, R.T. Heath, and J.B. Cotner. Effects of the zebra mussel, Dreissena polymorpha, on community nitrogen dynamics in Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):529-544 (1995).

The effects of the zebra mussel, Dreissena polymorpha, on chlorophyll and nutrient concentration changes and community ammonium uptake and regeneration rates were determined in bottle experiments on waters collected from a eutrophic site and an oligotrophic site in Saginaw Bay, Lake Huron in 1992. Our objectives were to estimate nitrogen cycling rates and to determine the direct (excretion) and indirect (foodweb) effects of the zebra mussel on these rates. Isotope labeling experiments with added 15NH4 were conducted on waters collected on five sampling dates between April and October. Direct effects of zebra mussels on ammonium regeneration and potential uptake were examined by comparing results from bottles incubated with (15 individuals in 4 L lake water) and without added zebra mussels. Indirect foodweb effects were examined by measuring regeneration and potential uptake rates in subsamples of water that had previously been incubated in the presence or absence of zebra mussels. Zebra mussels removed a large fraction of chlorophyll from the oligotrophic site on all sampling dates and from the eutrophic site in October, but had a negligible effect on chlorophyll levels in waters from the eutrophic site in June, July, August, and September when cyanophytes were abundant. Community ammonium regeneration rates and uptake rates both followed seasonal patterns resembling those for chlorophyll concentrations in control treatments at the eutrophic site. Rates for water from the oligotrophic site were low (usually not significantly different from zero) and are not reported here. Community ammonium regeneration rates were consistently enhanced in the presence of zebra mussels, indicating that zebra mussel excretion could have a dominant effect on nitrogen regeneration in regions where it is abundant. Zebra mussels appeared to decrease community uptake rates of ammonium in August and September but did not predictably affect nitrogen remineralization rates by other lower foodweb organisms (e.g. bacteria, protozoans, zooplankton).

GARDNER, W.S., P.A. St. John, C. Evans, and J.F. CAVALETTO. HPLC retention-time-shift determination of nitrogen isotope ratios in enriched water. American Laboratory June 1996:17C-17H (1996).

No abstract.

GOSSIAUX, D.C., P.F. LANDRUM, and S.W. Fisher. Effect of temperature on the accumulation kinetics of PAHs and PCBs in the zebra mussel, Dreissena polymorpha. Journal of Great Lakes Research 22(2):379-388 (1996).

The role of temperature on the accumulation and elimination kinetics of selected polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl (PCB) congeners was examined for the zebra mussel, Dreissena polymorpha. Uptake and elimination rates were measured at intervals over a three year period in laboratory toxicokinetics studies in which zebra mussels were maintained at ambient field temperatures or acclimated to higher or lower temperatures. The uptake rate coefficients (ku) for benzo(a)pyrene (BaP) and 2.2'4.4',5.5'-hexachlorobiphenyl (HCBP) increased in proportion to temperature over a range from 4 to 20o C when measured at the field-collected temperature. Both ku and the elimination coefficient (kd) also decreased with increasing organisms size. However, no relationship with temperature was found for the ku of BaP in the following year nor was there a relationship between ku and temperature for pyrene and pentachlorophenol (PCP) when the kinetics were measured at field-collected temperatures. In laboratory acclimation studies, Ku for three compounds (BaP, HCBP, and PCP) showed a significant positive relationship with temperature over the 4-200C range. Pyrene accumulation kinetics, however, still exhibited no relationship with temperature. These results contradict the concept that uptake of contaminants changes over a season with temperature thereby influencing contaminant toxicokinetics. Furthermore, the kd values observed for these compounds indicate that elimination was slow, and no relationship of kd was exhibited with water temperature, season, or year.

Graney, J.R., A.N. Halliday, G.J. Keeler, J.O. Nriagu, J.A. ROBBINS, and S.A. Norton. Isotopic record of lead pollution in lake sediments from the northeastern United States. Geochimica et Cosmochimica Acta 59(9):1715-1728 (1995).

Although it is common knowledge that Pb concentrations have increased in lake sediments in the northeastern United States over the last 150 years, the processes responsible have been the subject of debate. In this study, differences in lead isotopic compositions and concentrations in sediment from large takes (Lake Erie, Ontario, and Michigan) and small ones (Deep Lake and Lake Andrus) are used to infer temporal changes in the source(s) of anthropogenic Ph in the Great Lakes region. A natural (background) component of Ph is present in sediment deposited prior to 1860 in Lake Erie and the other lakes as indicated from low Ph concentrations and uniform lead isotopic compositions. Changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic Ph superimposed on the natural component such as regional deforestation from 1860-1890 followed by coal combustion and ore smelting through 1930. Combustion of leaded gasoline was the dominant anthropogenic Ph source to the atmosphere (and by inference to lake sediment) from 1930-1980. Temporal changes in lead isotopic compositions in lake sediment suggest that the source of the Ph used in gasoline additives gradually changed from 1930 to present. The best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased Ph production from the Viburnum Trend deposits in Missouri (present in all lakes except Ontario). However, the changes in lead isotopic compositions are much less variable than, and do not parallel those calculated on the basis of annual United States mine production and imports. Rather, anthropogenic recycling of Pb as well as natural mixing processes during emission, transport, and deposition of Pb in lake sediment control most of the variation in lead isotope ratios. Differences in lead isotopic ratios in Lake Michigan, Erie, and Deep Lake sediment preserve regional differences in lead isotopic ratios from U.S. and Canadian sources first noted in aerosols by Sturges and Barrie (1987). More localized sources of Pb (such as point discharges) are needed to explain the results from Lake Ontario and Andrus.

HAWLEY, N., and C.R. Murthy. The response of the benthic nepheloid layer to a downwelling event. Journal of Great Lakes Research 21(4):641-651 (1995).

Time series observations of water temperature, current velocity, and water transparency were made at three elevations at a mooring in southwestern Lake Ontario over a 14-day period. Although a strong downwelling event occurred during the deployment, there was no indication of either local sediment resuspension or of downslope transport of suspended material. Our observations, when combined with those of Hawley and Lesht (1995), indicate that material is not supplied to the benthic nepheloid layer by either local resuspension or offshore transport during the stratified period. Although several authors have suggested that the maintenance of the benthic nepheloid layer during the stratified period requires the periodic supply of additional material after it is formed, the sources of this material are not well known. Some material is most likely supplied by the settling of material from the epilimnion, but an additional-as yet unidentified-source seems to be needed to explain the observed changes in both the thickness and the concentration of material suspended in the benthic nepheloid layer.

Heath, R.T., G.L. FAHNENSTIEL, W.S. GARDNER, J.F. CAVALETTO, and S.-J Hwang. Ecosystem-level effects of zebra mussels (Dreissena polymorpha): An enclosure experiment in Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):501-516 (1995).

We examined the short-term effects of zebra mussels (Dreissena polymorpha) on ecosystem processes in late August 1991 in Saginaw Bay, Lake Huron. Four 1,600 L enclosures, made of Fabreen with a diameters of 1 m, a depth of 2 m, and closed at the bottom, were used to enclose natural plankton communities. These communities were dominated by diatoms with some chlorophytes, chrysophytes, and cyanophytes. Phytoplankton growth was limited by P-availability. Two enclosures were held as controls, and zebra mussels encrusting unionid shells were suspended in two of the enclosures: one enclosure (HZ) contained approximately four-fold greater numbers of mussels than the other (LZ). The concentration of suspended particles, chlorophyll, and algal biomass in HZ and LZ declined over a 6-day interval. Diatom numbers declined more than other taxa. Phytoplankton growth rates in HZ and LZ increased to near mmax; there was no apparent change in photosynthetic parameters a of Pmax scaled for chlorophyll. Soluble reactive P (SRP) increased significantly (p < 0.05) in HZ but not LZ. Dissolved organic P (DOP) and ammonium ion were elevated; dissolved organic carbon (DOC) was unchanged in HZ and LZ. The rate of phosphate uptake by bacteria and algae declined to less than 2% of controls; this rate decrease could not be explained simply by grazing losses or isotope dilution. The rate of ammoniun regeneration by the plankton and the potential rate of ammonium uptake by the plankton did not differ significantly in HZ or LZ from the control enclosures. Our findings indicate that the zebra mussel can have significant short-term effects on phytoplankton abundance water transparency, water chemistry and phosphorus dynamics. We propose a model of zebra mussel effects that suggests high densities of zebra mussels may indirectly alter and control those processes that are rate-limited or concentration-limited by nutrient availability.

Holland, R.E., T.H. JOHENGEN, and A.M. BEETON. Trends in nutrient concentrations in Hatchery Bay, western Lake Erie before and after Dreissena polymorpha. Canadian Journal of Fisheries and Aquatic Sciences 52:1202-1209 (1995).

Concentrations of soluble reactive phosphorus, ammonium-nitrogen, nitrate-nitrogen, silica, and chloride have all increased since the establishment of the zebra mussel (Dreissena polymorpha) in Hatchery Bay, western Lake Erie, in 1988. Total phosphorus concentrations have changed little. These results are from 188 samples collected weekly and year round before the establishment of Dreissena (1984-1987) and 192 samples post-Dreissena (1990-1993). The mean annual total phosphorus concentration for the three complete post-Dreissena years was 35 mgL-1, strikingly similar to the concentration of 36 mgL-1, which in 1959 helped to define the waters of Lake Erie as eutrophic. The relative steadiness in total phosphorus may reflect sediment reflux, because Hatchery Bay is a polymictic system. The slight increase in the biologically conservative ion, chloride, in the 1990s, is probably due to the increased precipitation and runoff in the western Lake Erie watershed. Decreased phytoplankton and associated increased water clarity caused by efficient filtering by D. polymorpha, have lessened symptoms of eutrophication and produced a situation where nutrients are not fully utilized, i.e., biological oligotrophy.

Horowitz, A.J., J.A. ROBBINS, K.A. Elrick, and R.B. Cook. Bed sediment-trace element geochemistry of Terrace Reservoir, Near Summitville, Southwestern, Colorado. Open File Report 96-344. U.S. Geological Survey, Atlanta, GA, 41 pp. (1996).

In 1994, the U.S. Geological Survey conducted an extensive bed sediment geochemical survey in Terrace Reservoir, near Summitville, southwestern, Colorado. Both the surface (grab) and near-surface (core) sediments are substantially enriched in Cu, Pb, Zn, Cd, As, Sb, Hg, Fe, and Al relative to unaffected fine-grained sediments collected in a variety of environments throughout the United States. The majority of the enriched trace elements appear to be associated with operationally defined residual phases which are not likely to be environmentally available. The exceptions are Cu and Zn, which appear to be associated with operationally defined labile phases. Sediment-associated Cu, Pb, Zn, As, and Sb apparently are being exported downstream from the reservoir, into the San Luis Valley, by the Alamosa River. Attempts to develop a sediment-geochemical history of the reservoir using 137Cs and 210Pb indicate that the onset of trace element enrichment substantially predates the onset of heap-leach mining operations at Summitville. There are some indications, based on median and maximum sediment-associated trace element levels, that the onset of heap-leach mining may have marginally increased the concentrations and fluxes of some of the already enriched trace elements in the reservoir bed sediments.

Ingersoll, C.G., G.T. Ankley, D.A. Benoit, E.L. Brunson, G.A. Burton, F.J. Dwyer, R.A. Hoke, P.F. LANDRUM, T.J. Norberg-King, and P.V. Winger. Toxicity and bioaccumulation of sediment-associated contaminants using freshwater invertebrates: A review of methods and applications. Environmental Toxicology and Chemistry 14(11):1885-1894 (1995).

This paper reviews recent developments in methods for evaluating the toxicity and bioaccumulation of contaminants associated with freshwater sediments and summarizes example case studies demonstrating the application of these methods. Over the past decade, research has emphasized development of more specific testing procedures for conducting 10-d toxicity tests with the amphipod Hyalella azteca and the midge Chironomus tentans. Toxicity endpoints measured in these tests are survival for H. azteca and survival and growth for C. tentans. Guidance has also been developed for conducting 28-d bioaccumulation tests with the oligochaete Lumbricus variegatus, including determination of bioaccumulation kinetics for different compound classes. These methods have been applied to a variety of sediments to address issues ranging from site assessments to bioavailability of organic and inorganic contaminants using field-collected and laboratory-spiked samples. Survival and growth of controls routinely meet or exceed test acceptability criteria. Results of laboratory bioaccumulation studies with L. variegatus have been confirmed with comparisons to residues (PCBs, PAHs, DDT) present from synoptically collected field populations of oligochaetes. Additional method development is currently underway to develop chronic toxicity tests and to provide additional data confirming responses observed in laboratory sediment tests with natural benthic populations.

JOHENGEN, T.H., O.E. Johannsson, G.L. PERNIE, and E.S. Millard. Temporal and seasonal trends in nutrient dynamics and biomass measures in Lakes Michigan and Ontario in response to phosphorus control. Canadian Journal of Fisheries and Aquatic Science 51:2570-2578 (1994).

Results from long-term ecological monitoring studies on Lake Michigan (1983-92) and Lake Ontario (1981-92) were compared with regard to changes in phosphorus loads. In Lake Ontario, total phosphorus (TP) loads decreased from 14 000 tyr-1 in 1970 to 7500 tyr-1 in 1981, and correspondingly, midlake TP concentration decreased from 25 to 16 mgL-1. From 1981 to 1991, TP loads remained around 7500 tyr-1; however, TP concentration continued to decline from 16 to 10 mgL-1. Similarly, mean summer particulate organic carbon (POC), chlorophyll a (CHLa), and nitrate utilization rate decreased by approximately 40, 20, and 50%, respectively. Conversely, silica utilization rates increased markedly after 1983. In Lake Michigan, TP loads also decreased by around 50% from 1974 to 1990 (2000 tyr-1); however, TP concentrations at our 100-m station in the southern basin increased during the study period from around 4 to 8 mgL-1. There were no distinct trends in CHLa or nutrient utilization patterns; however, POC levels decreased sharply after 1987. Overall, silica utilization rates in Lake Michigan were 50% higher than in Lake Ontario (14.7 vs. 9.6 mgL-1d-1), whereas nitrate utilization rates were only half (1.4 vs. 4.1 mgL-1d-1).

JOHENGEN, T.H., T.F. NALEPA, G.L. FAHNENSTIEL, and G. Goudy. Nutrient changes in Saginaw Bay, Lake Huron after the establishment of the zebra mussel Dreissena polymorpha. Journal of Great Lakes Research 21(4):449-464 (1995).

Concentrations of particulate and dissolved nutrients in Saginaw Bay, Lake Huron, were examined relative to zebra mussel colonization which occurred summer 1991. The magnitude and spatial pattern of changes indicate that mussels had a significant impact on nutrients in Saginaw Bay. Annual means for total suspended solids, particulate organic carbon, particulate phosphorus, and particulate silica in the inner bay were significantly lower in 1992 and 1993 (post-zebra mussel) than in 1991 (pre-zebra mussel). Annual means decreased from 11.5 mg L-1, 1.45 mg C L-1 (121 mM), 20.4 mg P L-1 (0.66 mM), and 1.52 mg SiO2 L-1 (24 mM) respectively in 1991 to 4.4 mg L-1, 0.79 mg C L-1 (66 uM, 11.2 mg P L-1 (0.36 mM), and 0.77 mg SiO2 L-1 (12 mM) in 1993. In contrast, there were no significant differences among years for these parameters at control stations, which were located in the outer bay and had no known populations of mussels. Annual means for nitrate, ammonium, and silica were significantly higher in the inner bay in 1992 than in 1991, but not significantly different in 1993. Means increased from 0.39 mg N L-1, 21.0 mg N L-1, and 1.11 mg Si02 L-1 respectively in 1991 to 0.47 mg N L-1, 30.9 mg N L-1, and 1.71 mg SiO2 L-1 in 1992. No significant differences were observed for these parameters in the control group. Differences between 1992 and 1993 may reflect differences in the amount of runoff and circulation between Saginaw Bay and Lake Huron. A phosphorus budget indicated that zebra mussels were a significant sink for phosphorus. Mussels from the inner bay accumulated 108, 682, and 52 t respectively in 1991, 1992, and 1993. Comparatively, the annual pool of phosphorus in the water column of the inner bay decreased from a pre-zebra mussel (1979-1980) average of 712 t to 421 and 382 t in 1992 and 1993 respectively.

Kelley, J.G.W., D.J.S. Welsh, K.W. Bedford, D.J. SCHWAB, J.S. Hobgood, and B. Hoch. High-resolution, short-term lake forecasts for Lake Erie. Proceedings, Fourth International Conference of Estuarine and Coastal Modeling, M.L. Spaulding and R.T. Cheng (eds.), San Diego, CA, October 26-28, 1995. American Society of Civil Engineers, New York, NY, 367-378 (1996).

Short-term lake forecasts for Lake Erie are generated daily by the one-way coupling of the operational mesoscale Eta atmospheric model with the Great Lakes Forecasting System (GLFS). GLFS, a collaborative project between The Ohio State University (OSU) and NOAA's Great Lakes Environmental Research Laboratory (GLERL), consists of a modified version of the Princeton coastal ocean model and the GLERL-Donelan wave model. The Eta model is a mesoscale weather-prediction model operated by the U.S. National Centers for Environmental Prediction (NCEP). The Eta model forecasts of surface wind and heat flux are used as boundary conditions by GLFS to produce 30-hour forecasts for Lake Erie's physical conditions. Lake forecast products are available from an OSU World Wide Web server or through GLFSview, a Windows based viewing application. After two months of operation, a preliminary evaluation shows that significant errors typically exist in the GLFS forecasts. Inaccurate Eta model forecasts and initial lake temperature fields have been identified as major sources of error which must be addressed.

**Klump, J.V., K.W. Bedford, M.A. Donelan, B.J. EADIE, G.L. FAHNENSTIEL, and M.R. Roman. Coastal Ocean Processes (CoOP): Cross-Margin Transport in the Great Lakes. Great Lakes Coastal Ocean Workshop, Milwaukee, WI, October 6-8 1994. University of Maryland, 133 pp. (1995).

No abstract.

Kukkonen, J., and P.F. LANDRUM. Distribution of organic carbon and organic xenobiotics among different particle-size fractions in sediments. Chemosphere 32(6):1063-1076 (1996).

The distributions of benzo[a]pyrene, hexachlorobiphenyl, and total organic carbon in a Lake Michigan sediment and a Florissant soil sample were determined and related to the known bioavailability of the compounds. The distribution of organic compounds among small particles (<63 mm diameter) was different from the distribution of the total organic carbon. However, the organic matter remained the major sorbent for these compounds. Changing the fractionation conditions, by performing the fractionation in distilled water instead of natural lake water, altered the distributions for both organic carbon and xenobiotics among the particles. Further, the contaminant distribution relative to organic carbon content differed between particle-size fractions and between contaminants of different compound classes, e.g., PAHs and PCBs. The differential distribution of the contaminants in the particle-size fractions likely contributed to the observed differences in bioavailability of organic contaminants for benthic organisms and may be exacerbated by selective feeding.

LANDRUM, P.F., G.A. HARKEY, and J. Kukkonen. Evaluation of organic contaminant exposure in aquatic organisms: the significance of bioconcentration and bioaccumulation. In Ecotoxicology: A Hierarchial Treatment, M.C. Newman and C. H. Jogoe (eds.). CRC Press, Lewis Publishers, Boca Raton, FL, 85-131 (1996).

No abstract.

LANG, G.A., and G.L. FAHNENSTIEL. Great Lakes primary production modelmethodology and use. NOAA Technical Memorandum ERL GLERL-90, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-157664/XAB) 15 pp. (1996).

The Great Lakes Production Model (GLPM) estimates in situ integral daily production, accounting for diel variations in surface irradiance and depth variations in photosynthesis-irradiance parameters, algal biomass, and light extinction. A comparison of integral production estimates in the northern Gulf of Mexico and Lake Michigan obtained using the GLPM with those obtained by in situ and simulated in situ techniques indicated good agreement. In an effort to obtain estimates of primary production at sites where P-I parameters are not available, a version of the GLPM was designed to run in a monte carlo mode. A model sensitivity analysis indicates that the model is most sensitive to changes in two input parameters: the light extinction coefficient and algal biomass. Model framework and background are presented, input terms are defined, and example output is displayed.

LAVRENTYEV, P.J., W.S. GARDNER, J.F. CAVALETTO, and J.R. Beaver. Effects of the zebra mussels (Dreissena polymorpha Pallas) on protozoa and phytoplankton from Saginaw Bay, Lake Huron. Journal of Great Lakes Research 21(4):545-557 (1995).

Direct effects of the grazing activities of the zebra mussel, Dreissena polymorpha, on the natural assemblage of planktonic protozoa and algae from Saginaw Bay, Lake Huron, were studied in September and October 1994. Water and mussels collected from two eutrophic sites were incubated in an outdoor "natural light" incubator at ambient temperature for 24 hours. Experiments were conducted in 4-L bottles with screened (40 or 53-mm net) or unscreened water and with and without mussels. Despite relatively high growth rates of protozoa on both dates, mussels lowered protozoan numbers by 70-80% and reduced the species richness of the protozoan community by 30-50%. Large heterotrophic flagellates were reduced up to 100% while peritrichous ciliates attached to the colonies of blue-greens were reduced only by 50%. Dreissena selectively removed nanoplanktonic Cryptomonas and Cyclotella, but had no significant effect on the predominant phytoplankton species, Microcystis. Overall, Dreissena clearance rates were low in the presence of this cyanophyte species. We conclude that zebra mussels, in regions where they are abundant, can cause significant changes in composition of both the protozoan and phytoplanktonic communities.

LEE, D.H., R. Moulton, and B.A. HIBNER. Climate Change Impacts on Western Lake Erie, Detroit River, and Lake St. Clair Water Levels. Great Lakes-St. Lawrence Basin Project Report, Ann Arbor, MI, 51 pp. (1996). (24 MB)

The means and frequencies of Lake St. Clair, Detroit River, and western Lake Erie water levels are computed for a changed climate resulting from a doubling of atmospheric carbon dioxide, and compared to those of the present climate. Lake level frequencies for specific sites in the study areas, and potential movement of the shorelines due to decreases in mean lake levels, are illustrated by a series of maps. General surveys of impacts on wetlands, recreational boating, commercial navigation, and public water supply intakes are given. The intent of this work is to provide basic data to other researchers performing broader and more detailed impact studies as part of the Great Lakes-St. Lawrence Basin Project. With the changed climate scenario, the surface area and volume of Lake St. Clair decreases by 15% and 37%, respectively, relative to that of the present climate. Likewise, the surface area and volume of the western Lake Erie basin decreases by 4% and 20%. The surface area of the lower Detroit River decreases by 19%. The shoreline moves from less than 1 km to 6 km offshore from that of the present climate, with significant loss of freshwater estuaries and embayments.

LESHKEVICH, G.A. Satellite mapping of Great Lakes ice cover. Proceedings, First Moderate Resolution Imaging Spectroradiometer (MODIS) Snow and Ice Workshop, D.K. Hall (ed.), Greenbelt, MD, September 13-14, 1995. NASA Goddard Space Flight Center, Greenbelt, MD, 87-91 (1995).

Much of the satellite ice interpretation algorithm development in the Great Lakes region began during the Extension to the Navigation Season Demonstration Study conducted during the 1970s. However, many of the early studies were done by visual interpretation of satellite and other remotely sensed data. Starting in the mid-1970's, a series of studies including field studies and computer digital image processing, explored techniques and algorithms to classify and map freshwater ice cover using Landsat, NOAA/AVHRR, and ERS-1 SAR data. The goal of much of this work is to develop an automated or semi-automated method to classify and map Great Lakes ice cover using satellite digital imagery.

LESHKEVICH, G.A., W. Pichel, P. Clemente-Colon, R. Carey, and G. Hufford. Analysis of coastal ice cover using ERS-1 SAR data. International Journal of Remote Sensing 16(17):3459-3479 (1995).

An applications demonstration of the use of Synthetic Aperture Radar (SAR) data in an operational setting is being conducted by the National Oceanic and Atmospheric Administration (NOAA) CoastWatch Program. In the development phase of this demonstration, case studies were conducted to assess the utility of SAR data for monitoring coastal ice in the Bering Sea, icebergs from calving glaciers in Prince William Sound, and lake ice in the Great Lakes. ERS-1 SAR data was used in these studies. Results showed that depending on size and sea state icebergs could be detected from background and computer enhanced in the imagery, that SAR data can supplement and enhance the utility of satellite visible and infrared data sources for coastal ice monitoring, and that Great Lakes ice cover can be classified by ice type and mapped in the SAR data using image processing techniques. Cloud cover was a common problem. Based on the further development of automated analysis algorithms and the increase in frequency of SAR coverage, the all-weather, day/night viewing capabilities of SAR make it a unique and valuable tool for operational ice detection and monitoring.

LESHKEVICH, G.A., D.J. SCHWAB, and G.C. MUHR. Satellite environmental monitoring of the Great Lakes: Great Lakes CoastWatch Program Update. Third Thematic Conference on Remote Sensing for Marine and Coastal Environments, Seattle, WA, September 18-20, 1995. I-116 to I-128 (1995).

As the CoastWatch regional node for the Great Lakes, the Great Lakes Environmental Research Laboratory (GLERL) obtains, processes, and delivers environmental data and products for the user community. GLERL provides access to near real-time satellite observations and in situ data for the Great Lakes to 41 Federal, state, and local agencies and academic institutions. The goals and objectives of the CoastWatch Program directly support NOAA statutory responsibilities in estuarine and marine science, living marine resource protection, and ecosystem monitoring and management. A digital image product suite of 26 images from the NOAA 12, NOAA 14, and GOES 8 satellites is currently being received. Over 32,000 image products have been received and archived since 1990. In addition, in situ and modeled data including marine and meteorological observations, and water level gauge measurements, are also routinely received and made available via dial-in modem or INTERNET. A new product developed at GLERL, the Great Lakes Surface Environmental Analysis (GLSEA), is a cloud-free, composited surface temperature chart that will include an ice cover analysis overlay during winter months. It is available to CoastWatch data users and also on the World Wide Web.

LIEBIG, J.R., and H.A. VANDERPLOEG. Vulnerability of Dreissena polymorpha larvae to predation by Great Lakes calanoid copepods: the importance of the bivalve shell. Journal of Great Lakes Research 21(3):353-358 (1995).

Dreissena polymorpha larvae were vulnerable to predation by three different species of calanoid copepods, Diaptomus sicilis, Limnocalanus macrurus, and Epischura lacustris, when presented to these copepods in bottle experiments. The degree of vulnerability was dependent upon the stage of the larva and the type of predator: trochophore larvae (without shells) were much more vulnerable than D-stage larvae (with shells). D. sicilis and L. macrurus were offered algae as alternate food, and each cleared trochophore larvae at a higher rate than algae. However, the clearance rate for D. sicilis feeding on D-stage larvae was not significantly different from zero, suggesting that this suspension-feeding omnivore-herbivore was not able to ingest D-stage larvae. Of the three species, the large cruising predator, L. macrurus, had the highest clearance rate for trochophore larvae (55.8 mLanimal-ld-l), but had a significantly lower clearance rate for D-stage larvae, only one eighth of that for trochophores. The smaller predator, E. Iacustris, was more adept than L. macrurus or D. sicilis at preying on D-stage larvae: its clearance rate for D-stage larvae (17.9 mLanimal-ld-l) was about one half of its clearance rate for trochophore larvae. Since bivalve larvae, including Dreissena, and copepods co-occur in many aquatic environments, our results suggest that copepod predation may have been a selective force for production of a protective shell early in the larval development of bivalves.

LOFGREN, B.M. Sensitivity of land-ocean circulations, precipitation, and soil moisture to perturbed land surface albedo. Journal of Climate 8(10):2521-2542 (1995).

Using general circulation model experiments, it was found that thermally induced overturning circulations that flow between oceans and land at low latitudes can be affected by perturbations to the land surface albedo. When surface albedo is reduced over land at low latitudes, radiative heating of the surface is increased and additional heat is transferred from the surface to the atmosphere, which is largely offset by adiabatic cooling associated with upward motion. This enhanced upward motion is associated with greater low-level convergence of air over the continents, compensated by divergence over the oceans. The enhanced flux of water vapor onto the continents due to this pattern further enhances the thermal forcing through the release of latent heat. In these low-latitude regions with reduced surface albedo, precipitation and soil moisture are increased. Qualitatively opposite effects are obtained by increasing surface albedo. In midlatitude regions, circulation and precipitation are not significantly affected by land surface albedo. However, decreased surface albedo does increase the amount of heat available at the surface for evaporation. This greater heat availability depletes soil moisture earlier in the season. Again, qualitatively opposite effects are obtained by increasing surface albedo. Similar perturbations in land surface albedo are used as an analog to the effects of low-level atmospheric aerosols, which have been proposed as a mechanism that may presently be offsetting C02-greenhouse warming. The resulting temperature changes are compared with those occurring in an increased CO2 simulation.

LOFGREN, B.M. Surface albedo-climate feedback simulated using two-way coupling. Journal of Climate 8(10):2543-2562 (1995).

To simulate the effects of feedback between climate and surface albedo via vegetation, a scheme was developed, based on a generalized life zone scheme, for estimating the land surface albedo as a function of annual mean precipitation and surface temperature. This scheme was applied to the climate of a GCM and made interactive with the GCM. The climate of this run was compared with one in which the land surface albedo was prescribed to a spatially uniform value. Allowing such feedback within the modeling system enhances the atmospheric ascent and heavy precipitation of tropical rainbelts, in comparison with a case with spatially homogeneous surface albedo prescribed. It also intensifies the atmospheric descent and low precipitation rates over subtropical latitudes. That is, a positive feedback occurs at low latitudes. At midlatitudes, thermal forcing due to the spatial distribution of surface albedo has little effect on vertical motion or precipitation. However, in the Central Asian and Gobi Deserts, the high surface albedo cools the surface, reduces evaporative demand, and allows the soil and vegetation to retain more moisture, indicating negative feedback. Because the northern edge of the Sahara has negative feedback similar to that in midlatitudes, while the southern part has positive feedback, the Sahara as a whole is shifted southward when surface albedo feedback is included.

McCORMICK, M.J. Lake Erie Water Temperature Data: Sandusky Bay, Ohio 1961-1993. NOAA Technical Memorandum ERL GLERL-98, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202445/XAB) 19 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Erie Water Temperature Data: Put-In-Bay, Ohio 1918-1992. NOAA Technical Memorandum ERL GLERL-97, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202452/XAB) 41 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Erie Water Temperature Data: Erie, PA 1916-1992. NOAA Technical Memorandum ERL GLERL-94, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-197991/XAB) 42 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Huron Water Temperature Data: Bay City, MI 1946-1993. NOAA Technical Memorandum ERL GLERL-93, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202437/XAB) 21 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Michigan Water Temperature Data: St. Joseph, MI 1936-1992. NOAA Technical Memorandum ERL GLERL-96, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202411/XAB) 25 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Michigan Water Temperature Data: Green Bay, WI 1947-1990. NOAA Technical Memorandum ERL GLERL-95, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202783/XAB) 26 pp. (1996).

No abstract.

McCORMICK, M.J. Lake Superior water temperature data: Sault Ste. Marie, MI 1906-1992. NOAA Technical Memorandum ERL GLERL-99, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-202429/XAB) 48 pp. (1996).

No abstract.

McCORMICK, M.J., G.L. FAHNENSTIEL, S.E. Lohrenz, and D.G. Redalje. Calculation of cell-specific growth rates: a clarification. Limnology and Oceanography 41(1):182-189 (1996).

Cell-specific growth and cell-specific production estimates of phytoplankton have been calculated in the past by a simple exponential model (constant uptake division) that describes the time rate of change of carbon, C*, and assumes both continuous division and continuous carbon uptake. We propose three new models (variable uptake-division, variable uptake-constant division, and diurnal) for making more accurate estimates of the algal growth rate, m. The variable uptake-division model is the most complex and requires species-specific information on the division pattern. The diurnal model can provide accurate m estimates while requiring only two measurements of C* and no other parameters, but it requires 48-h incubation times. The variable uptake-constant division model can also provide accurate m estimates and can be applied to data with <24-h incubation times. The variable uptake division and variable uptake-constant division models require additional work compared to the constant uptake division model, but the effort is warranted because they also provide a direct approach for quantifying the dependence of m on the photoperiod and thus enable greater confidence in applying m to ecological studies, in which the light climate may differ from that of the experiment.

NALEPA, T.F. Exotics species and ecosystem management. In State of the Great Lakes, 1995 Annual Report, M. Waszak (ed.). Michigan Dept. of Environmental Quality, Lansing, MI, 21-22 (1996).

No abstract.

NALEPA, T.F., and G.L. FAHNENSTIEL. Special Section on Zebra Mussels in the Saginaw Bay, Lake Huron, Ecosystem. T.F. Nalepa, and G. L. Fahnenstiel (eds.). International Association for Great Lakes Research, NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 132 pp. (1995).

No abstract.

NALEPA, T.F., and G.L. FAHNENSTIEL. Dreissena polymorpha in the Saginaw Bay, Lake Huron ecosystem: overview and perspective. Journal of Great Lakes Research 21(4):411-416 (1995).

After the zebra mussel, Dreissena polymorpha, was first discovered in Lake St. Clair in 1988 and rapidly spread throughout the Great Lakes, broad ecological changes became apparent in regions where this species was most abundant. Previous investigations documented dramatic increases in water clarity (Hebert et al. 1991, Marsden et at. 1993, Leach 1993), declines in chlorophyll and phytoplankton abundances (Leach 1993, Nicholls and Hopkins 1993, Holland 1993), and changes in benthic invertebrate communities (Griffiths 1993, Dermott et al. 1993, Stewart and Haynes 1994). These studies were conducted in various regions and defined impacts on a specific ecosystem component. Taken together, results indicate a major shift in energy flow patterns from the pelagic to the benthic region. Such a shift is so fundamental that every component of the food web from bacteria to fish would likely be affected either directly or indirectly. Thus, to truly understand the significance of shifts in energy flow patterns, impact assessments should be as holistic as possible within a given ecosystem. Despite the magnitude of observed impacts, however, establishing cause-effect relationships at the ecosystem-level is not an easy task. Not all changes occur at the same rate, and natural variation, along with man-induced influences such as nutrient abatement programs, confound interpretations of any mussel-induced impacts.

NALEPA, T.F., G.L. FAHNENSTIEL, M.J. McCORMICK, T.H. JOHENGEN, G.A. LANG, J.F. CAVALETTO, and G. Goudy. Physical and chemical variables of Saginaw Bay, Lake Huron in 1991-93. NOAA Technical Memorandum ERL GLERL-91, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (NTIS# PB96-182357/XAB) 78 pp. (1996).

Physical and chemical data were collected in Saginaw Bay, Lake Huron over the period 1991-1993 to determine impacts of the zebra mussel, Dreissena polymorpha, on the Saginaw Bay ecosystem. This report gives values of data collected during that time period along with a detailed account of all sampling methods and analytical procedures.

NALEPA, T.F., D.J. HARTSON, G.W. GOSTENIK, D.L. FANSLOW, and G.A. LANG. Changes in the freshwater mussel community of Lake St. Clair: from Unionidae to Dreissena polymorpha in eight years. Journal of Great Lakes Research 22(2):354-369 (1996).

To determine density changes in both the zebra mussel, Dreissena polymorpha, and native mussels, Unionidae, in Lake St. Clair, surveys were conducted in 1990, 1992, and 1994 and compared to a similar survey, in 1986 when no D. polymorpha was found. Collection methods were the same each year; divers used the quadrat method to collect 10 replicate samples at 29 sites located throughout the lake. The total number of unionids collected declined from 281 in 1986, to 248 in 1990, 99 in 1992, and 6 in 1994, while the number of species collected in each of the four respective years was 18, 17, 12, and 5. The decline in the unionid community occurred gradually, over this time period in the D. polymorpha population expanded from the southeast region of the lake to the northwest region. Mean density, and biomass of D. polymorpha throughout the lake was 1,700 m-2 and 4.7 gDW m-2 in 1990, 1,500 m-2 and 3.5 gDW m-2 in 1992, and 3,200 m-2 and 3.1 gDW m-2 in 1994. The density increase can be attributed to the expansion of the population into the northwest region, while the decrease in biomass was mostly a result of a decline in the weight per unit length. Mean biomass of the D. polymorpha population in 1994 was actually lower than the mean biomass of unionids in 1986; however, based on literature-derived filtering rates, the filtering capacity of the D. polymorpha population in 1994 is 12 times greater than the filtering capacity of the unionid community, in I986. This increase has likely led to reported changes in the Lake St. Clair ecosystem (increased water clarity, increased plant growth, and shifts in fish communities.

NALEPA, T.F., J.A. WOJCIK, D.L. FANSLOW, and G.A. LANG. Initial colonization of the zebra mussel (Dreissena polymorpha) in Saginaw Bay: Population recruitment, density, and size structure. Journal of Great Lakes Research 21(4):417-434 (1995).

The various life stages of the zebra mussel (Dreissena polymorpha) were examined during the initial years (1991-93) of the mussel's invasion into Saginaw Bay, Lake Huron. Yearly trends in densities of larvae, newly-settled juveniles, and adults were poorly related. Larval densities were lowest in 1991 and increased each year, but the number of settled juveniles was highest in 1991. Adults increased between 1991 and 1992 and then declined in 1991 Mean adult densities at sites with hard substrates were 11,700, 33,200, and 4,100/m2 in each of the 3 years, respectively. Year-to-year variation at individual sites was high and likely a result of recruitment dynamics and spatial patchiness of available substrate. By 1993, densities on hard substrates were generally similar throughout the bay, but length-frequency distributions in the inner and outer bay were quite different. The 1991-cohort was not distinguishable in the inner bay in 1993 either because of poor growth or a limited life span, but this cohort was readily distinguishable in the outer bay. In addition, ash-free dry weight of a standard 15-mm mussel in the inner bay declined 65% between 1991 and 1993. Although food concentrations (chlorophyll and particulate organic carbon) declined to low levels in 1993 and both densities and soft-tissue weight of Dreissena declined, it is not clear whether populations in the bay have peaked and are now at equilibrium with the surrounding environment.

Ristola, T., J. Pellinen, P.L. VAN HOOF, M. Leppanen, and J. Kukkonen. Characterization of Lake Ladoga sediments. II. Toxic Chemicals. Chemosphere 32(6):1179-1192 (1996).

Chemical contamination of Lake Ladoga was studied by analyzing 12 sediment samples collected at various parts of the lake for polyaromatic hydrocarbons, chlorobenzenes, organochloropesticides, and heavy metals. The results were also used to explain the negative effects of these sediments observed earlier in bioassays with a midge Chironomus riparius (Ristola et al. 1995). Concentrations of analyzed chemicals were mostly typical to lakes which are considered as unpolluted. Only the concentrations of PAH were somewhat elevated in the sediment collected near River Volkhov inlet in the southern part of the lake. Adverse effects on midges could, however, not be explained by chemical contamination.

Schloesser, D.W., T.F. NALEPA, and G.L. Mackie. Zebra mussel infestation of unionid bivalves (Unionidae) in North America. American Zoology 36:300-310 (1996).

In 1989, zebra mussels received national attention in North America when they reached densities exceeding 750,000/m2 in a water withdrawal facility along the shore of western Lake Erie of the Laurentian Great Lakes. Although water withdrawal problems caused by zebra mussels have been of immediate concern, ecological impacts attributed to mussels are likely to be the more important long-term issue for surface waters in North America. To date, the epizoic colonization (i.e., infestation) of unionid bivalve mollusks by zebra mussels has caused the most direct and severe ecological impact infestation of and resulting impacts caused by zebra mussels on unionids in the Great Lakes began in 1988. By 1990, mortality of unionids was occurring at some locations; by 1991, extant populations of unionids in western Lake Erie were nearly extirpated; by 1992, unionid populations in the southern half of Lake St. Clair were extirpated; by 1993, unionids in widely separated geographic areas of the Great Lakes and the Mississippi River showed high mortality due to mussel infestation. All infested unionid species in the Great Lakes (23) have become infested and exhibited mortality within two to four years after heavy infestation began. Data indicate that mean zebra mussel densities >5,000-6,000/m2 and infestation intensities >100-200/unionid in the presence of heavy zebra mussel recruitment results in near total mortality of unionids. At present, all unionid species in rivers, streams, and lakes that sympatrically occur with zebra mussels have been infested and, in many locations, negatively impacted by zebra mussels. We do not know the potential consequences of infestation on the 297 unionid species found in North America, but believe zebra mussels pose an immediate threat to the abundance and diversity of unionids.

SCHWAB, D.J., and K.W. Bedford. GLCFSA coastal forecasting system for the Great Lakes. Conference on Coastal Oceanic and Atmospheric Prediction, Atlanta, GA, January 28-February 2, 1996. American Meteorological Society, Boston, MA, 9-14 (1996).

No abstract.

SCHWAB, D.J., and K.W. Bedford. Operational three-dimensional circulation modeling in the Great Lakes. In Computer Modelling of Seas and Coastal Regions II, C.A. Brebbia, L. Traversoni , and L.C. Wrobel (eds.). Computational Mechanics Publications, Ashurst Lodge, Ashurst Southampton, 387-395 (1995).

No abstract.

SCHWAB, D.J., D. BELETSKY, W.P. O'CONNOR, and D.E. Dietrich. Numerical simulation of internal Kelvin waves with Z-level and Sigma level models. Proceedings, Fourth International Conference of Estuarine and Coastal Modeling, M.L. Spaulding and R.T. Cheng (eds.), San Diego, CA, October 26-28, 1995. American Society of Civil Engineers, New York, NY, 298-307 (1995).

Two three-dimensional primitive equation numerical ocean models are applied to the problem of internal Kelvin waves in the Great Lakes. One is the Princeton ocean model, with a terrain following (sigma) vertical coordinate, and the other is the DIECAST model with constant z-level coordinates. The models are first tested with an idealized circular stratified lake 100 km in diameter and 100 m deep. Two bathymetries are considered: a flat bottom and a parabolic depth profile. Three rectilinear horizontal grids are used: 5, 2.5, and 1.25 km. The Princeton model used 13 vertical levels while the DIECAST model was tested with both 13 and 29 vertical levels. The models are driven with an impulsive wind stress imitating the passage of a weather system. In the cast of the flat bottom basin, the dynamical response to light wind forcing is a small amplitude internal Kelvin wave. This response compares favorably with the analytic solution. In the case of strong wind forcing, the thermocline breaks the surface, and a strong thermal front appears. After the wind ceases, the edges of this thermal front propagate cyclonicaly around the lake, quite similar to an internal Kelvin wave. In the case of parabolic bathymetry and strong wind forcing, Kelvin wave propagation is modified by the stronger bottom friction in the coastal areas, and the interaction of the Kelvin wave with a topographic wave. The models are also applied to Lake Michigan with 5 km and 2 km grids. The results are more complex than the circular basin, but clearly show the characteristics of an internal Kelvin wave response. The results compare favorably with observations of temperature fluctuations at water intakes in Lake Michigan after a storm.

VANDERPLOEG, H.A., J.R. LIEBIG, and A.A. GLUCK. Evaluation of different phytoplankton for supporting development of zebra mussel larvae (Dreissena polymorpha): The importance of size and polyunsaturated fatty acid content. Journal of Great Lakes Research 22(1):36-45 (1996).

A marine alga and variety of freshwater algae of known polyunsaturated fatty acid (PUFA) composition were evaluated in the laboratory for their ability to promote development of Dreissena polymorpha from egg through settling and metamorphosis. The three species of algae which promoted developmentthe marine and the freshwater strain of Chlorella minutissima and the cryptophyte Rhodomonas minutawere all rich in long-chain (18oC) n-3 PUFAS, including some 20:5 or 22:6 PUFAS. Dreissena's need for long-chain n-3 PUFAs is consistent with the needs of marine bivalves and freshwater zooplankton. Larval growth rate on the freshwater strain of C. minutissima was about the same as that for R. minuta, but much faster than that for the marine strain of C. minutissima. Mean ages at settling for larvae fed the freshwater C. minutissima were 15 d at 26oC, 17 d at 24oC, and 22 d at 22oC. Low survival rates reported for the larvae in nature may be related to low concentrations of long-chain n-3 PUFAs in blue-green and some green algae that dominate eutrophic lakes in summer.

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