GLERL Publications Abstracts: FY 1988

ASSEL, R.A. Temperature effects on Lake Superior changes in storage: A 1976 case study update. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 8 pp. (1988).

Thermal effects on lake storage for the fall seasons of 1977, 1978, 1979 and the winter seasons of 1973, 1974, and 1975 were calculated from temperature surveys and a thermal structure model for estimating beginning-of-month (BOM) mean temperature profiles. Water density and water volume for 40 discrete layers of Lake Superior define the lake's mass on BOM dates. Thermal changes in lake storage between BOM dates are calculated from joint volumetric and mass balances. Results show that thermal changes in storage are up to 6% of the total monthly change in lake storage during fall and winter months. September 1976 had anomalous thermal change in storage (-12%) due to much below-normal air temperatures. September 1978 and 1979 thermal changes in storage were approximately +3% to +6%, respectively. Thermal change in monthly change in storage during 1976 was outside the maximal and minimal values of a 20-year (1946-65) base period for 5 out of 12 months, which indicates it is not feasible to apply monthly averaged thermal change in storage to water balance studies of Lake Superior.

ASSEL, R.A. The winter of 1986-87. Lakes Letter, Newsletter of International Association of Great Lakes Research 18(2):7 (1987).

No abstract.

BEETON, A.M. The role of research in management of the Laurentian Great Lakes. In Prevention of Toxic Contamination in Large Lakes, Vol. IV, N.W. Schmidtke (ed.). Lewis Publishers, Chelsea, MI, 211-219 (1988).

No abstract.

BOLSENGA, S.J. Nearshore Great Lakes ice cover. Cold Regions Science and Technology 15:99-105 (1988).

Analysis of the growth, dissipation, thickness, and stratigraphy of ice cover in the nearshore zone of the Great Lakes, on a lake-by-lake basis, shows certain features governed by regional weather patterns and by the energy budget factors associated with each lake. However, local factors tend to exert a major influence on the formation and decay of ice in most of the locations and much year-to-year variability was noted. A detailed analysis of the factors influencing the ice cover in any area would provide explanation for anomalies, but such studies can only be justified on a case-by-case basis.

BOLSENGA, S.J. Note on certain diurnal variations in the albedo of snow and ice. In Seasonal Snowcovers: Physics, Chemistry, Hydrology, H.G. Jones and W.J. Orville-Thomas (eds.). D. Reidel Publishing Company, Norwell, MA, 141-150 (1987).

No abstract.

BOLSENGA, S.J., G.M. GREENE, and K.M. HINKEL. Nearshore Great Lakes ice statistics. NOAA TM ERL GLERL-69, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB89-100192/XAB) 42 pp. (1988).

Data collected from an ice thickness and stratigraphy network from 1965-66 through 1978-79 permit definition of nearshore ice thickness conditions. The data are summaries for 29 locations in the Great Lakes.

CARRICK, H.J., and R.L. Lowe. Response of Lake Michigan benthic algae to in situ enrichment with Si, N, and P. Canadian Journal of Fisheries and Aquatic Sciences 45(2):271-279 (1988).

The possibility that benthic algae in the nearshore area of Lake Michigan might be growth limited by Si was tested using nutrient-releasing substrata. Nutrient treatments were Si, N + P, Si + N + P, and controls (CONT) and were sampled after 7, 14, and 31 d of exposure. Addition of Si alone had little stimulatory effect on algal biomass, while enrichment with Si + N + P led to the greatest increase in chlorophyll a, particulate Si, total biovolume, and diatom biovolume after 14 d of incubation (P < 0.0001). By day 31, communities on CONT and Si substrata exhibited little change in biomass and remained dominated by diatoms (98% of total biovolume), while algal biomass on both N + P and Si + N + P substrata increased more than eightfold (P < 0.0001) and consisted mainly of Stigeoclonium tenue (Chlorophyta) and Schizothrix calcicola (Cyanophyta). These results indicate that benthic diatoms in Lake Michigan are not currently limited by Si, but may become Si limited following enrichment with N + P.

Chelton, D.B., A.W. BRATKOVICH, R.L. Bernstein, and P.M. Kosro. Poleward flow off central California during the spring and summer of 1981 and 1984. Journal of Geophysical Research 93(C9):10,604-10,620 (1988).

Currents and winds measured over the continental shelf and upper continental slope during the first half of 1984 are analyzed to determine the character of the flow off central California (Point Conception to San Francisco). The mean flow was poleward from Point Conception to Point Sur, in opposition to the equatorward wind stress. The mean flow was equatorward north of Point Sur. Fluctuations in alongshore currents over the shelf were highly correlated with local winds everywhere except off Point Conception, where currents were not only uncorrelated with wind but also poorly correlated with currents farther north. North of Point Buchon there is evidence for poleward propagation of shelf current variability at 175-200 cm/s. The correlation between currents and local wind forcing dropped considerably beyond the shelf break, only 10-15 km offshore from the shelf moorings. During extended periods of weak equatorward winds, the poleward shelf flow south of Point Sur spreads farther offshore over the continental slope. A three week period of calm winds in July 1984 resulted in a 100-km-wide tongue of poleward flow extending 300 km along the California coast. Similar, but somewhat weaker, poleward surface flow occurred during the same period in 1981; a 2- to 3-week period of calm winds in late June and early July 1981 resulted in a 100-km-wide tongue of poleward flow extending at least 150 km along the California coast. In contrast to the poleward flow on the shelf, which appears to be normal during spring and summer, the poleward surface flow observed over the slope in July 1981 and 1984 is unusual, based on historical hydrographic surveys off the central California coast. Poleward surface flow over the continental slope occurs seasonally in the winter but is not generally observed after February.

CROLEY, T.E., II, and H.C. HARTMANN. Effects of climate changes on the Laurentian Great Lakes levels. EPA DW13932631-01-0. The Potential Effects of Global Climate Change on the United States: Appendix A - Water Resources, U.S. EPA, Office of Policy, Planning, and Evaluation, Washington, DC, 4.1-4.34 pp. (1988).

No abstract.

CROLEY, T.E., II, and H.C. HARTMANN. Near real-time forecasting of large lake supplies. Journal of Water Resources Planning and Management 113(6):810-823 (1987).

The Great Lakes Environmental Research Laboratory (GLERL) has developed conceptual model-based techniques for making outlooks of basin moisture conditions, basin runoff, water supplies, and lake levels several months into the future for large lake basins. The techniques consider the water stored in the basins about the lakes and the uncertainty of future meteorologic conditions. We estimate a large lake basin's current moisture storage with GLERL's tank-cascade runoff model, applied to each of the subbasins about the lake, and with near real-time meteorology. We select historic meteorologic sequences, representing anticipated meteorology, based on the National Weather Service monthly and seasonal forecasts of precipitation and air temperature probabilities, for use with the runoff model to generate our near real-time outlooks. Error analysis for the Lake Superior Basin identifies the outlook error components and their relative magnitudes, indicates the outlook is superior to climatology, and suggests that improvements await better weather forecasting and lake evaporation modeling.

DERECKI, J.A. Method used by the Great Lakes Environmental Research Laboratory (NOAA) for determination of flows (1979-86). In Lakes Michigan-Huron outflows, St. Clair and Detroit Rivers, 1900-86, Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data, International Joint Commission, 17-23 (1988).

No abstract.

DERECKI, J.A., and F.H. QUINN. Comparison of vertical velocity measurements in the Great Lakes Connecting Channels with theoretical profiles. Reprinted from Hydraulic Engineering, Proceedings, 1988 National Conference, Hydraulic Division/American Society of Civil Engineers, Colorado Springs,CO, August 8-12, 1988. 276-281 (1988).

Vertical distribution of velocities was measured with an upward looking acoustic Doppler current profiler in the upper St. Clair River during November 1984 - April 1986 and the Detroit River from November 1986. The current meter stations are located approximately 1 km downstream of the Blue Water Bridge in Port Huron on the St. Clair River and about 2 km downstream of the Ambassador Bridge in Detroit on the Detroit River. The acoustic meter measures Doppler shift to provide continuous measurements of velocities throughout the water column, from about 1 m above the sensor (located near the bottom) to the surface. These averaged velocities are recorded at mid-points of the individual 1 m segments. Surface readings are not used because of large scattering at the air-water interface. With water depth of about 14 m at both meter locations, the profiler provides 11 vertical velocity readings at 1 m increments between about 2.5 m above the bottom and about 0.5 m below the surface. The measured data are recorded at 15 min intervals, from which hourly and daily values are derived. These velocity vectors are later combined to produce vertical velocity profiles of the two rivers. The velocity data for shorter periods indicate somewhat larger scatter, but the vertical velocity profiles for all periods illustrate high consistency and verification of the theoretical, logarithmic vertical distribution of velocities.

EADIE, B.J., T.F. NALEPA, and P.F. LANDRUM. Toxic contaminants and benthic organisms in the Great Lakes: Cycling, fate and effects. In Toxic Contamination in Large Lakes, Volume I. Chronic Effects of Toxic Contaminants in Large Lakes, N.W. Schmidtke (ed.). Lewis Publishers, Chelsea, MI, 161-178 (1988).

Most persistent contaminants in aquatic systems have a strong affinity for particulate matter and eventually become associated with the sediments. This results in elevated concentrations and exposures for the organisms that inhabit the benthic region. There are three consequences of this behavior. First, the organisms, through their stirring and feeding activities (bioturbation), mix the contaminant-laden sediments through a thickness representing several years to decades of sediment accumulation, thereby stretching out the lake's time dependent response to contaminant input. Second, the organisms bioaccumulate contaminants from the sediment-pore water matrix and this material can be passed up the food web. High concentrations of several contaminants (e.g. PCBs, PAHs) have been measured in the benthic invertebrates of the Great Lakes. Their body burden is usually related to local sediment concentrations. Laboratory experiments with the abundant amphipod, Pontoporeia hoyi, indicate the predominant uptake pathway is via water, thus some sediment-water transfer is necessary to explain the field observations. Third, chronic chemical stress from the complex mixture of contaminants may cause shifts in the composition and density of the benthos.

FAHNENSTIEL, G.L., and D. SCAVIA. Dynamics of Lake Michigan phytoplankton: The deep chlorophyll layer. Journal of Great Lakes Research 13(3):285-295 (1987).

The dynamics of the Lake Michigan deep chlorophyll layer (DCL) were studied from the period of late spring isothermal mixing (May) through mid-stratification (July-August) in 1982-1984. After the onset of thermal stratification, the DCL developed in the 15-30 m region and deepened to 25-50 m in July and 40-70 m in August. Chlorophyll and phytoplankton carbon concentrations in the DCL averaged, respectively, 1.80X and 1.34X epilimnetic concentrations during early stratification (June). Those factors increased to 5.70X and 2.60X during mid-stratification. Although phytoplankton carbon concentrations within the DCL changed on average only 31% from May through July-August, phytoplankton species composition exhibited pronounced shifts. Measured phytoplankton growth, sedimentation, and zooplankton grazing rates suggest DCL formation was attributable to in situ growth and to a lesser extent to sedimentation and shade adaptation. By July, sedimentation resulted in a net loss from the DCL. With the deepening of the DCL during mid-stratification, the importance of in situ growth decreased while the importance shade adaptation increased. In situ growth was only important in the upper part of the DCL. Zooplankton grazing increased during mid-stratification and was at least partially responsible for phytoplankton concentrations decreases in the 20-50 m region.

FAHNENSTIEL, G.L., D. SCAVIA, G.A. LANG, J.H. SAYLOR, G.S. MILLER, and D.J. SCHWAB. Impact of inertial period internal waves on fixed-depth primary production estimates. Journal of Plankton Research 10(1):77-87 (1988).

Fixed-depth subthermocline phytoplankton production estimates were compared to variable-depth estimates calculated along the simulated trajectory of an internal wave. The mean of 5000 Monte Carlo simulations, varying wave phase and amplitude, was not significantly different than the fixed-depth estimate for average Lake Michigan internal waves. Differences were significant, however, for wave amplitudes >5 m but only at some depths. Differences between the two estimates were related to differences in irradiance received and the portion of the photosynthesis-irradiance (P-I) curve controlling production. Oscillating communities always receive more irradiance than fixed-depth communities and the magnitude of this increase is related to the extinction coefficient and the amplitude of the internal waves. Production was also estimated along an individual isotherm trajectory (isotherm-derived) and compared to fixed-depth production. Larger differences between these isotherm-derived and fixed-depth estimates were noted in some cases and were related to differences in the mean isotherm depth and the sampled (fixed) depth. If one accounts for the trajectory of the sampled community, fixed-depth estimates are reliable; however, if the trajectory is unknown or unaccounted for, an individual fixed-depth production estimate may not adequately measure in situ production.

GARDNER, W.S., J.F. CHANDLER, G.A. LAIRD, and D. SCAVIA. Microbial response to amino acid additions in Lake Michigan: Grazer control and substrate limitation of bacterial populations. Journal of Great Lakes Research 12(3):161-174 (1986).

Removal of low levels (0.3 - 1.3mM) of primary amines (PA) were examined by direct injection liquid chromatography in offshore Lake Michigan water to provide insight about potential cycling rates of labile organic compounds and to examine the hypothesis that populations of active bacteria are controlled by organic-substrate limitation. Uptake rates of amino acids in untreated lake water ranged from <0.1 to 3.7 nmole PA L-1h-1 (0.01 to 0.34 mg C L-1h-1) as compared to rates of up to 9 nmole PA :-1h-1 (0.61 mg C L-1h-1) in samples fortified with amino acids. Highest PA uptake rates were observed in samples collected in July and August. As expected for Michaelis-Menton Kinetics, PA uptake rates increased with increasing amino acid concentrations (up to a maximum velocity), suggesting that bacterial "growth rates" were substrate limited. However, PA removal rates in given lake water samples usually remained relatively constant over periods of several days. The consistency of population uptake rates over time suggested that bacterial abundances did not change greatly in response to amino acid additions. Thus, although bacterial growth rates in Lake Michigan epilimnetic water are apparently controlled by organic substrate supply, our data are consistent with the hypothesis that bacterial abundances, and therefore total-population heterotrophic uptake activity, may often be controlled by grazers. The chemical approach used in this study yields a conservative estimate of the maximum velocity of microbial use of amino acids in natural waters.

GARDNER, W.S., J.F. CHANDLER, G.A. LAIRD, and H.J. CARRICK. Sources and fate of dissolved free amino acids in epilimnetic Lake Michigan water. Limnology and Oceanography 32(6):1353-1362 (1987).

A seasonal series of light- and dark-bottle experiments was conducted on epilimnetic Lake Michigan water during 1986 to examine the dynamics of dissolved free amino acids (DFAA) in the pelagic microbial food web. When microbial uptake sites were saturated with DFAA, net primary amine removal rates were lower in light than in dark bottles, presumably due to release of DFAA by phytoplankton. Release rates ranged from 0.8 to 3.5 ng-atoms N liter-1 h-1 in bottled lake water held several days at in situ temperatures. Ammonium accumulation rates in the dark ranged from <0.4 to 4 nmol liter-1 h-1. Ammonium regeneration was enhanced (up to 3-8 nmol liter-1 h-1) by the addition of DFAA (0.94 uM) to unfiltered lake water. On average, the increases in ammonium-N accumulation equaled losses of amino acid nitrogen from the same water samples [ratio = 1.01 (SE = 0.08, n = 29)]. This result suggests that Lake Michigan microheterotrophs may dominate DFAA and not maintain the nitrogen in food-web biomass.

GARDNER, W.S., T.F. NALEPA, and J.M. MALCZYK. Nitrogen mineralization and denitrification in Lake Michigan sediments. Limnology and Oceanography 32(6):1226-1238 (1987).

Organic nitrogen mineralization mechanisms, fluxes, and fates in Lake Michigan sediments were examined by measuring accumulation rates of inorganic nitrogen in laboratory microcosms. Neither ammonium nor nitrate increased substantially in flow-cell or slurry microcosms of offshore, silty sediments. In experiments with gastight chambers containing "intact" offshore, silty sediment cores (sampled at 45- and 100-m water depths), the total fluxes of nitrogen (NH4+, NO3- and N2) across the sediment-water interface ranged from 14 to 51 mg-atoms N m-2 h-1. Nitrogen gas accounted for 93-98% of the total inorganic nitrogen flux from the sediment to the water. Inputs of inorganic nitrogen via mineralization processes (mediated by microbial decomposition and invertebrate excretion) appeared to be the major factors controlling the rates of both nitrification and denitrification in these sediments. The overlying water did not serve as a significant net source of nitrate driving the denitrification reaction. These results thus indicate that denitrification is a dominant sink for mineralized nitrogen in these silty Lake Michigan sediments and that this process is closely coupled with the initial mineralization of organic nitrogen in the sediments.

HARTMANN, H.C. Potential variation of Great Lakes water levels: A hydrologic response analysis. NOAA Technical Memorandum ERL GLERL-68, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB88-199203/XAB) 30 pp. (1988).

The potential for water level changes on Lakes Michigan, Huron, St. Clair, and Erie is examined, using the Great Lakes Environmental Research Laboratory's Hydrologic Response Model (HRM) in conjunction with several hydrometeorologic and water management scenarios. Of the scenarios examined, only a drought similar to that of the early 1960's could return the lakes to their normal levels of 1900-1969. If the regional climatology of 1971-1985 persists for several years, the lake level regime will average about 0.5 m higher than that of 1900-1969. The extreme water supply conditions of 1985 must be accompanied by 50% increases in Lake Superior outflows and persist for about 10 years to raise Lake Michigan and Huron levels 1.0 m above their 1986 record levels. The practice of increasing winter flows from Lake Superior to provide water storage in the spring and summer has practically no effect on downstream lake levels. The effect of a barge that accidentally lodged in the Niagara River in August 1986 raised levels on Lakes Michigan-Huron, St. Clair, and Erie by a maximum of 1, 4, and 5 cm, respectively; by June 1987 the effect had entirely dissipated. Elimination of the Long Lac and Ogoki diversions and increases of the Chicago and Welland Canal diversions to 283 m3/s (10,000 ft3/s) for a period of 7 to 8 years could reduce the levels on Lakes Michigan-Huron, St. Clair, and Erie by only 25, 21, and 18 cm, respectively; half of that lowering, however, would occur in 2 to 3 years. These scenarios suggest that Great Lakes interests should not count on lake levels returning to long-term (1900-1969) normal levels within the next several years.

HARTMANN, H.C., and T.E. CROLEY. Great Lakes water management: Modeling hydrologic impacts. Preprints, Eleventh Conference on Weather Modification/Seventh Conference on Hydrometeorology, Edmonton, Alberta, Canada, October 6-8, 1987. American Meteorological Society, Boston, MA, 174-177 (1987).

No abstract.

HARTMANN, H.C., and F.H. QUINN. Climatic extremes and Great Lakes water management. Proceedings: Water for World Development VI, IWRA World Congress on Water Resources, Volume II, Ottawa, Ontairo, Canada, May 29-June 3, 1988. International Water Resources Association, Urbana, IL, 476-485 (1988).

Historical climatic conditions suggest that the typical climate of the North American Great Lakes region is much cooler and wetter than the regime experienced during the mid-twentieth century. However, anthropogenic increases in greenhouse gases may cause a climatic warming in the next 50 years. A model of the hydrologic response of the Great Lakes was used with a range of hydrometeorological scenarios to provide a perspective on the potential for water level variations and possible water management strategies. Climatic shifts, whether cooler or warmer, will require new paradigms of how the Great Lakes will be viewed from social, economic, and ecological perspectives.

HAWLEY, N. Flow in cylindrical sediment traps. Journal of Great Lakes Research 14(1):76-88 (1988).

Flow behavior in cylindrical settling traps was observed in steady flow for trap Reynolds numbers (Re) between 1,600-30,500. The effects due to aspect ratio, wall thickness, a funnel at the bottom of the trap, and the presence of a mooring line were investigated. Although the data are semiquantitative, they show that upwelling frequency and intensity increased as Re increased and as the aspect ratio decreased. The relationships between the thickness of the bottom layer, the frequency of upwelling, and the settling velocity of a particle determines whether deposition occurs through the bottom tranquil layer or the viscous sublayer. Since the thickness of the bottom tranquil layer can be scaled by the trap diameter, the settling behavior of particles cannot be modeled simply by Re and the aspect ratio, as can blow behavior, but also depends on the ratio of flow velocity to settling speed. Flow behavior induced by wave action is similar in many ways to that generated by steady flow at the same Re. Depending upon flow conditions in the trap, either the measured flux or the size distribution of the material collected may differ substantially from that outside the trap. Traps that are designed so that upwelling does not occur during their deployment will give that best estimates of flux and particle distribution. This means that in most cases several small traps are preferable to a single large trap.

Holland, R.E., A.M. BEETON, and T.H. JOHENGEN. Saline Valley rural clean water project interim report on monitoring during 1987. Contract Report, Michigan Department of Agriculture, Washtenaw County Board of Commissioners, the Monroe County Board of Commissions, the Washtenaw County Soil Conservation District, and the Monroe County Soil and Water Conservation District, 117 pp. (1988).

No abstract.

KEILTY, T.J., E.F. Stoermer, and D.S. White. Algal remains in some surface sediments of Lake Erie. Journal of Great Lakes Research 14(2):164-170 (1988).

Algal remains, primarily diatoms, were examined in the 0-1 cm fraction of sediment cores collected at eight stations along a west-to-east transect in Lake Erie to determine species composition, cell density, and flux rates. Sixty-two taxa were identified of which 13 were common to all stations. Highest densities and flux rates occurred in the western and eastern basins. Species composition, cell density, and flux rates in the sediments did not appear to correlate well with previous reports of water-column phytoplankton distribution and abundance. The distribution of diatom remains in the sediments more likely resulted from the effects of near-bottom west-to-east energy zones and transport mechanisms operating within the western and central basins of Lake Erie. The distribution of algal remains demonstrated that caution should be used in applying paleolimnological data to trophic status changes in Lake Erie.

KEILTY, T.J., D.S. White, and P.F. LANDRUM. Short-term lethality and sediment avoidance assays with endrin-contaminated sediment and two oligochaetes from Lake Michigan. Archives of Environmental Contamination and Toxicology 17:95-101 (1988).

Mean 96-hr LC50 values and standard deviations for the oligochaetes S. heringianus and L. hoffmeisteri exposed to endrin-contaminated sediment were 2,588 +/- 1,974 mg/g dry weight sediment for 4 assays and 2,725 +/- 955 mg/g for 2 assays, respectively. Mixed species testing data suggested that the toxicity to L. hoffmeisteri was reduced in the presence of S. heringianus, yet further testing is required. Ninety-six hour EC50 burrowing avoidance values for both species (19 and 15.3 mg/g for S. heringianus and 59 mg/g for L. hoffmeisteri) were approximately 46 and 150 times lower than their respective mean 96-h LC50 values. Both S. heringianus and L. hoffmeisteri initially burrowed n contaminated sediment and then returned to the surface in numbers somewhat proportional to the sediment concentration and the length of exposure. Future use of oligochaete behavioral responses to sublethal sediment contamination for pollutant impact on benthic communities is promising.

Kitchell, J.F., M.S. Evans, D. SCAVIA, and L.B. Crowder. Report--Regulation of water quality in Lake Michigan: Report of the food web workshop. Journal of Great Lakes Research 14(1):109-114 (1988).

During the past 20 years, Lake Michigan has experienced substantial reduction in nutrient inputs, major changes in the biological community, and re-configuration of the pelagic food web. Alewife, the previously dominant zooplanktivore, has decreased to 10-20% of its former abundance, a new assemblage of zooplankton has become dominant, and summer water clarity has increased nearly three-fold in that time. This report summarizes an International Joint Commission (IJC)-sponsored Workshop on Food Web Interactions convened in Ann Arbor during 4-6 December 1985. In general, physical-chemical conditions are the major regulators of water quality during spring and fall periods. Food web effects are most manifest in offshore waters during the period of summer stratification. Discussion during the workshop led to insights regarding the causes of recent changes, their association with nutrient controls and /or food web interactions, and the likely dimensions for future effects.

LAIRD, G.A., D. SCAVIA, G.L. FAHNENSTIEL, L.A. STRONG, and G.A. LANG. Dynamics of Lake Michigan phytoplankton: Relationship to nitrogen and silica fluxes. Canadian Journal of Fisheries and Aquatic Sciences 45(8):1459-1466 (1988).

We describe rates of nitrogen and silica concentration change during May-August 1 983 and 1 984 in southeastern Lake Michigan and compare those rates with measured plankton processes. Epilimnetic dissolved inorganic nitrogen depletion, compared with total phytoplankton demand, suggests that about 44% of the nitrogen demand is recycled. Epilimnetic diatom production, calculated from soluble silica depletion, is a relatively small fraction (<20%) of total primary production, even when diatoms dominate. Sedimentation of epilimnetic diatom silica, compared with total silica depletion, suggests that a large portion (approximately 43%) of epilimnetic particulate silica sedimentation is due to nonliving diatoms.

LAIRD, G.A., D. SCAVIA, G.L. FAHNENSTIEL, L.A. STRONG, J.M. MALCZYK, G.A. LANG, and W.S. GARDNER. Southern Lake Michigan nutrients, temperature, chlorophyll, plankton, and water movement during 1983 and 1984. NOAA Technical Memorandum ERL GLERL-67, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB88-148572/XAB) 27 pp. (1987).

We describe rates of nitrogen and silica concentration change during May-August 1 983 and 1 984 in southeastern Lake Michigan and compare those rates with measured plankton processes. Epilimnetic dissolved inorganic nitrogen depletion, compared with total phytoplankton demand, suggests that about 44% of the nitrogen demand is recycled. Epilimnetic diatom production, calculated from soluble silica depletion, is a relatively small fraction (<20%) of total primary production, even when diatoms dominate. Sedimentation of epilimnetic diatom silica, compared with total silica depletion, suggests that a large portion (approximately 43%) of epilimnetic particulate silica sedimentation is due to nonliving diatoms.

LANDRUM, P.F. Toxicokinetics of organic xenobiotics in the amphipod Pontoporeia hoyi: The role of physiological and environmental variables. Aquatic Toxicology 12:245-271 (1988).

The accumulation and elimination kinetics of selected polycyclic aromatic hydrocarbons and polychlorinated biphenyl congeners were determined for the amphipod, Pontoporeia hoyi, the major benthic invertebrate in the Great Lakes. Rates measured during the course of several field seasons, along with environmental and physiological variables, indicated that for compounds less water soluble than anthracene, the uptake rate constant (Ku) is inversely proportional to the mass of the organisms and directly proportional to experimental temperature. The role of temperature was again limited to the more water insoluble compounds. The depuration rate constant (Kd) was inversely proportional to the octanol-water partition coefficient, the mass of the organism, and the lipid content of the organisms. Kd was directly proportional to temperature, although the effect of temperature was again insignificant for the very water soluble biphenyl. The magnitude of the thermal effect was lower during the summer and early fall when the lipid content of the organisms was high. Both the uptake and elimination kinetics are dependent on a variety of physiological and environmental factors. The kinetic parameters must be normalized for the various factors before comparisons of kinetics of P. hoyi between collections at different times during the year and different sampling sites can be made.

LESHKEVICH, G.A. Goniometric measurements of a spray-painted barium sulfate reference panel. Remote Sensing of Environment 24:287-296 (1988).

Goniometric measurements of a spray-painted barium sulfate reference panel were made to detrmine its Lambertian characteristics in the visible and near-infrared (400-1100 nm) range for zenith angles from 0o to80o. Errors in Lambertian response varied with zenith angle and wavelength and ranged from 0 to 52% in the visible and .03 to 30% in the near-infrared. The non-Lambertian behavior of a reference panel can cause considerable error when its radiance data is used in the calculation of reflectance factors or in the characterization of irradiance conditions. A technique to correct calculated reflectance factors of field targets collected under clear sky conditions for the non-Lambertian response of a spray-painted barium sulfate reference panel is described.

LESHKEVICH, G.A. Non-Lambertian reference panel effect on spectral reflectance measurements of freshwater ice. International Journal of Remote Sensing 9(4):825-832 (1988).

Airborne measurements of the spectral reflectance of freshwater ice types on Saginaw Bay (Lake Huron) were used as ground data for satellite (AVHRR) interpretation of the ice cover. These were corrected for the non-Lambertian character of the spray-painted barium sulphate reference panel whose radiance data, measured on the ground, were used in the calculation of reflectance factors. The reflectance measurements were previously corrected for dark current, transmittance of the radiometer optics, and atmospheric attenuation and path radiance from the measurement altitude of 300m. The correction for the non-Lambertian response of the reference panel at the wavelengths and Sun zenith angle at which the panel radiance was measured, resulted in an average decrease in reflectance of 8 x 3 per cent in the visible band and 3 x 6 per cent in the near-infrared band for the ice types measured.

LIU, P.C. A measurement of equilibrium range in the frequency spectra of wave slopes. Preprints, Seventh Conference on Ocean-Atmosphere Interaction, Anaheim, CA, January 31-February 5, 1988. American Meteorological Society, Boston, 150-153 (1988).

No abstract.

McCORMICK, M.J., and G.A. Meadows. An intercomparison of four mixed layer models in a shallow inland sea. Journal of Geophysical Research 93(C6):6774-6788 (1988).

Four mixed layer (ML) models after Denman [1973] (KLD), Garwood [1977] (RWG), McCormick and Scavia [1981] (K), and Thompson [1976] (RT) were compared against an extensive water temperature data set collected in the central basin of Lake Erie during the summer of 1979. Results suggest that all four models are nearly equal in their ability to satisfactorily simulate surface water temperatures. However, if diurnal physical processes are of interest, then the model ability to simulate both the ML depth and the energy level associated with entrainment dh/dt becomes crucial. While three of the models, KLD, RT, and RWG, were satisfactory in simulating the ML depth, only two of the models RT and RWG, were satisfactory in matching the energy levels seen in the entrainment spectra of dh/dt. This agreement suggests that the shear velocity D V entrainment scaling plays a critical role in the cycling of shallow depth mixed layers.

Mortimer, C.H. Discoveries and testable hypotheses arising from Coastal Zone Color Scanner imagery of southern Lake Michigan. Limnology and Oceanography 33(2):203-226 (1988).

CZCS (Coastal Zone Color Scanner) images, confined mainly to the southern basin of Lake Michigan during the warm-up phases of 1979, 1980, and 1981, have furnished tools for synoptic reconnaissance of the wind-perturbed transition of the thermal regime in large basins from the winter to summer condition (including front formation and upwelling events), the coupling of phytoplankton growth with that transition, the intermittent mobilization and surface transport of sediment resuspended by storms, and the extensive temporary trapping or river-derived dissolved organic matter (gelbstoff) between the shoreline and the offshore-migrating thermal front. Intermittent resuspension of particles and variable inputs of gelbstoff, which occur in many coastal waters, rended inapplicable the CZCS algorithms successfully used in ocean studies for atmospheric correction and for quantification of phytoplankton chlorophyll. That disappointment notwithstanding, there is a favorable match of the coverage and scene-revisit frequency of the CZCS and the space and time scales of significant features of the above-listed processes. The observed pattern changes shed new light on the above processes and generate several testable conjectures. These relate to whole-basin sediment transport, coastal upwelling of near-bottom sediment suspensions, and frontal hydrodynamics and its coupling with phytoplankton distributions.

NALEPA, T.F., and P.F. LANDRUM. Benthic invertebrates and contaminant levels in the Great Lakes: Effects, fates, and role in cycling. In Toxic Contaminants and Ecosystem Health; A Great Lakes Focus, M.S. Evans (ed.). Wiley and Sons, Inc., New York, 77-102 (1988).

Most persistent toxic contaminants have a strong affinity for particulate material and, over time, become associated with the bottom sediments. As a result, benthic organisms play an integral role in the effects, fates, and cycling of contaminants throughout the rest of the aquatic system. In general, studies of interactions between the benthos and toxic contaminants can be divided into two categories. The first category examines the response of benthic organisms to changes in contaminant levels. Benthic response may be examined in the field by assessing changes in benthic communty structure, or in the laboratory by using acute and chronic toxicity tests. The other category concerns the effect of benthic-mediated processes on contaminant cycling and distribution. Examples of such processes are bioaccumulation, biotrubation, and trophic transfer. This review will focus on known interactions between benthic organisms and contaminants in the Great Lakes. Benthic organisms are here defined as those invertebrates retained by a 0.5-0.6 mm screen, or those commonly referred to as the "macrobenthos." Although other benthic groups, such as bacteria and meiobenthos, are also important in contaminant fates and effects, they will not be considered in this review. Since benthic groups occurring in the Great Lakes are not unique to this system, relevant studies from other freshwater environments will also be presented.

NALEPA, T.F., M.A. QUIGLEY, and R.W. ZIEGLER. Sampling efficiency of the Ponar grab in two different benthic environments. Journal of Great Lakes Research 14(1):89-93 (1988).

Numbers of benthic organisms collected with the Ponar grab were compared to numbers in diver-collected cores in a nearshore, sandy habitat in Lake Michigan, and to numbers in box cores taken with a manned submersible in a deep, silty habitat in Lake Superior. The Ponar underestimated benthic abundances at both sampling sites. Ordered from most to least efficiently sampled were sphaeriids, Pontoporeia, oligochaetes, and chironomids; overall mean abundances in core samples were 1.5, 1.7, 3.4, and 11.3 times greater than abundances in Ponar samples for the four groups. The extent by which abundances were underestimated was remarkably similar at the two sampling locations. This would indicated that underestimates are consistent, thus allowing appropriate correction factors to be applied if absolute abundances are required for a particular study. Total biomass in the box core samples was 1.7 times greater than in the Ponar samples.

PARRISH, C.C., X. Zhou, and L.R. HERCHE. Flame ionization and flame thermionic detection of carbon and nitrogen in aquatic lipid and humic-type classes with an Iatroscan Mark IV. Journal of Chromatography 435:350-356 (1988).

The Iatroscan Mark III flame ionization detection (FID) system has been very useful for determining lipid classes separated by thin-layer chromatography (TLC) on Chromarods (see, e.g., refs. 1-8). A novel use of this technique has been to measure humic and other polar organic classes in marine samples. Flame thermionic detection (FTID) has recently been introduced for the determination of nitrogen- an halogen-containing organic compounds in the Iatroscan. The existing FID system in the Mark II or the latest mark IV Iatroscans can be replaced by a FID-FTID system that improves linearity and sensitivity of carbon response to aromatic compounds and permits detection of nonogram levels of nitrogen and halogens in those compounds. Here we evaluate the optimize the performance of the Iatroscan Mark IV fitted with the FID-FTID system in the measurement of aquatic organic classes.

QUIGLEY, M.A. Gut fullness of the deposit-feeding amphipod, Pontoporeia hoyi, in southeastern Lake Michigan. Journal of Great Lakes Research 14(2):178-187 (1988).

Pontoporeia hoyi Smith, a deposit-feeding amphipod and a prominent member of the Great Lakes macrobenthic community, was collected at a45-m depth site in southeast Lake Michigan during October 1983 and March, May, June, August, and September 1984. Substantial numbers of animals with empty or partially-full guts indicated that P. hoyi feeds intermittently, unlike other continuous-feeding amphipods which routinely maintain uniformly full guts among all members of a population. The incidence of animals with empty, partially-full, and full guts also varied significantly with animal size and sampling date and implied that aspects of the amphipod's life history, and seasonality, were primarily responsible for changes in feeding rates. Overall, P. hoyi gut fullness was greatest in spring and , secondarily, in autumn, reflecting an opportunistic feeding strategy that exploited newly-deposited detritus generated from spring and autumn phytoplankton blooms. This strategy, in association with P. hoyi's known capacity to store energy as lipids may largely explain P. hoyi's known capacity to store energy as lipids may largely explain P. hoyi's exclusive and widespread distribution in profundal areas of the upper great Lakes, compared to other amphipods.

QUINN, F.H. Likely effects of climate changes on water levels in the Great Lakes. Proceedings, First North American Conference on Preparing for Climate Change: A Cooperative Approach, Washington, DC, Oct. 27-29, 1987. Climate Institute, Washington, DC, 481-487 (1988).

No abstract.

SAYLOR, J.H., and G.S. MILLER. Observation of Ekman veering at the bottom of Lake Michigan. Journal of Great Lakes Research 14(1):94-100 (1988).

An experiment of 100 m of water off the east coast of Lake Michigan during 1984 provided continuous current velocity recordings at four levels located from 1 m to 9 m above the lake bottom and also at 50 m. Near-inertial-period current oscillations were prominent and superimposed on longer-period velocity variations. Current speed at 1 m elevations varied from less than the threshold speed of the Savonious rotor sensor to 13 cm s-1. Profiles of current speed were close to logarithmic during many episodes of measurable currents over a 4-month-long recording interval. Over 50% of hourly-averaged profiles were in the nearly-logarithmic category (R > 0.987) during the month of September 1984. Veering averaging 11o was observed between low-pass-filtered current velocities measured at elevations of 1 m 9 m. Boundary layer theories developed from ocean studies are surveyed and the Lake Michigan data are examined from that perspective.

SAYLOR, J.H., and G.S. MILLER. Studies of large-scale currents in Lake Erie, 1979-1980. Journal of Great Lakes Research 13(4):487-514 (1987).

Currents and water temperatures were recorded at a large-scale grid of fixed moorings in Lake Erie from May 1979 through June 1980. Currents measured in the lower half of the central basin water column were mostly return flows (beneath the surface wind drift driven by the surface pressure gradient. Often observed was a complex system of Lake Erie circulation gyres as predicted by models. Another common occurrence was for one of the central basin gyres to become dominant and envelop the whole basin in either uniform clockwise or anticlockwise flow. It is not fully certain why one of the circulation cells grows as opposed to the others, but the curl of the wind stress had influence. The currents were more barotropic than predicted by full Ekman layer current models. Tidal-like currents driven by the longitudinal seiches of Lake Erie dominate the island-filled passages between the western and central Lake Erie basins, with currents across the whole island chain very closely in phase. Processes of hypolimnion volume entrainment are suggested from the central basin temperature recordings. Large volume water exchanges between the central and eastern basins occurred after the water mass in the vicinity of the shallow ridge that separates them from the experiment is explored.

SCAVIA, D., and G.L. FAHNENSTIEL. From picoplankton to fish: Complex interactions in the Great Lakes. In Complex Interations in Lake Communities, S.R. Carpenter (ed.). Springer-Verlag, New York, 85-97 (1988).

No abstract.

SCAVIA, D., G.A. LANG, and J.F. Kitchell. Dynamics of Lake Michigan plankton: a model evaluation of nutrient loading, competition, and predation. Canadian Journal of Fisheries and Aquatic Sciences 45(1):165-177 (1988).

Lake Michigan's offshore ecosystem has been altered dramatically during the past decade. Summer zooplankton dominance has changed from calanoid copepods to Daphnia and the substantial contribution of filamentous blue-green algae to summer phytoplankton has been replaced by phytoflagellates. These changes occurred concurrently with reduced P load, P concentration, and abundance of the dominant zoopanktivore, the alewife (Alosa pseudoharengus). In this analysis we pose alternative hypotheses of nutrient loading and species interactions as determinants of zooplankton and phytoplankton species composition in the summer epilimnion. We evaluate these hypotheses with a food web model that was calibrated to measurements of the 1980s Lake Michigan plankton composition and algal production, sedimentation, and growth rates and literature estimates of zooplankton secondary production and nutrient excretion. The model simulates the influence of gradients of both P load and alewife abundance on predation--competition interactions. We conclude that summer plankton composition in Lake Michigan is controlled largely by predation. The model further predicts a return to a plankton community similar to that of the 1970s under a scenario of increasing invertebrate predation by a new zooplankton species for Lake Michigan, Bythotrephes cederstroemi.

Schertzer, W.M., J.H. SAYLOR, F.M. Boyce, D.G. Robertson, and F. Rosa. Seasonal thermal cycle of Lake Erie. Journal of Great Lakes Research 13(4):468-486 (1987).

A summary of the seasonal water temperature characteristics of Lake Erie and the 1979 and 1980 thermal structure in the central basin is described. Ice cover extends over 90% of Lake Erie most winters. Minimum surface temperature usually occurs in February (0.1oC) but fully mixed conditions at 1oC or less occur in January with isothermal conditions at (1oC) occurring from mid-February to mid-March. The thermal bar advance lasts about 5 to 6 weeks from April to mid-May and permanent stratification usually begins in mid-June with maximum heat storage in mid-August and overturn in mid-September. The central basin thermocline position varies significantly from year to year, the variability of the upper and lower mesolimnion boundaries being as large as 10 m. Thermocline position shows some dependence on prevailing meteorological conditions and has implications to the development of central basin anoxia. Temperature increases and decreases depicted on isotherm plots for stations in the central basin show correspondence with peak wind stress events. During fragile stability conditions, even moderate wind stresses of less than 0.5 dynes/cm2 are capable of producing upper layer deepening. Episodes of complete vertical mixing in response to high wind stresses of 3 dynes/cm2 during storm periods are observed. Double thermoclines are evident at several locations within the basin and temperature changes resulting from an influx of hypolimnetic water from the Pennsylvania Ridge is documented . Periods of hypolimnetic entrainment are clearly observed along with thermocline tilting of 1 to 2 meters toward the south.

STEHLY, G.R., and W.L. Hayton. Detection of pentachlorophenol and its glucuronide and sulfate conjugates in fish bile and exposure water. Journal of Environmental Science and Health B23(4):355-366 (1988).

The glucuronide and sulfate conjugates of pentachlorophenol (PCP) that were present in the bile and exposure water of goldfish (Carassius auratus) were used to develop methodology to quantify PCP and its metabolites. Reverse phase HPLC with radioactivity detection separated PCP and its metabolites, and was used to verify a method of quantification that used differential extraction and scintillation counting. Extractions of aqueous phase at pH 2 or 8, with butanol, ethyl acetate, or ether indicated that ether at pH 8 best separated PCP from its metabolites. The sulfate conjugate of PCP was the major metabolite produced when goldfish were exposed to 125 mg 14C-PCP/1. It was present primarily in the exposure water, but also appeared in the bile.

STEHLY, G.R., and W.L. Hayton. Errors in the use of the accelerated bioconcentration test. In Aquatic Toxicology and Environmental Fate: Eleventh Volume, G.W. Suter II, and M. A. Lewis (eds.). American Society for Testing and Materials, Philadelphia, PA, 573-584 (1989).

The accelerated bioconcentration test is commonly used in aquatic toxicology to calculate the bioconcentration factor (BCF) for waterborne xenobiotics. This method assumes that when aquatic organisms accumulate chemicals, they behave as a single compartment with the chemical coming to an equilibrium between the organism compartment and the water. Experiments have shown, however, that for many lipophilic substances the aquatic organism must be modeled as two or more compartments to characterize the accumulation process adequately. We studied the errors associated in the estimation of the BCF when the accelerated test is applied to substances that require two compartments to represent the fish. Body level/time data for xenobiotic uptake and depuration were simulated using the computer simulation program Minidynamo. The aquatic organism was modeled as two compartments; the amount in the organism was a biexponential function of time; that is, for the uptake phase, X=Ae-at+be-bt where X is the amount in the organism, t is time and A, B, a, and b are constants. These data sets were then fitted using NONLIN, an iterative nonlinear least-squares computer program, to the single compartment model of the accelerated bioconcentration test to determine apparent uptake and depuration rate constants, k1 and k2, and to estimate the apparent BCF from their ratio. The larger the ratio of the 0 time intercepts of the two components of the biexponential curve A/B, the larger was the error in estimating BCF. Estimates for the uptake rate constant k1 were generally good but 10-30% smaller than the actual values, while the depuration rate constant (k2) was poorly estimated, even for cases where BCF was accurately estimated. In extreme cases the calculated BCF was less than 5% of the actual BCF. Testing for fit to multicompartmental models and knowledge of multicompartmental characteristics and the infusion input can aid in reducing errors involved in estimates of BCF, k1 and k2 by the accelerated bioconcentration test.

TARAPCHAK, S.J., H.K. SOO, and J.S. Tarapchak. An improved settling chamber and evaluation of procedures for preparing phytoplankton samples for quantitative 14C autoradiography. Archiv fur Hydrobiologie 111(4):547-558 (1988).

Autoradiographic analysis of phytoplankton species-population photosynthetic rates can be biased in two ways when cells are sedimented and rinsed in conventional settling chambers. (1) Population densities can be underestimated because micro-algae leak from unsealed chambers, and 14C uptake rates are reduced by the infusion of grease that forms a coating over cells when chambers are sealed to stop leakage. (2) 14C uptake rates for some species are significantly underestimated because radiolabeled compounds are released from preserved algae during the relatively long time periods required to settle and rinse cells. A modified plexiglass settling chamber, virtually free of the leakage problem, is described . Use of this chamber, coupled with rapid removal of inorganic 14C by bubbling samples with nitrogen prior to sedimentation, eliminates the need for multiple sample rinsing and thereby reduces intracellular 14C loss.

Vallentyne, J.R., and A.M. BEETON. The 'ecosystem' approach to managing human uses and abuses of natural resources in the Great Lakes basin. Environmental Conservation 15(1):58-62 (1988).

No abstract.

VANDERPLOEG, H.A., B.J. EADIE, J.R. LIEBIG, S.J. TARAPCHAK, and R.M. Glover. Contribution of calcite to the particle-size spectrum of Lake Michigan seston and its interactions with the plankton. Canadian Journal of Fisheries and Aquatic Sciences 44(11):1898-1914 (1987).

A linear systems-analysis model which simulates time-dependent dynamics of specific activity and concentration of radiocesium in lake ecosystems was applied to a shallow, eutrophic lake that had received a pulse input of 137Cs. Best estimates of transfer coefficients for abiotic compartments (sediment, interstitial water and lake water) and the macrophyte compartment which controlled the mass balance of cesium in water were determined by "tuning" our initial estimates of the transfer coefficients to observed data on 137Cs concentrations and contents of these compartments. In most cases, the optimized transfer coefficients for the abiotic compartments were not greatly different from our independently derived initial estimates and the simulations for optimized coefficients were close to those based on initial estimates.
The 137Cs concentrations in water as predicted by the optimized transfer coefficients were then used to calculate 137Cs kinetics in biota other than macrophytes. In general, model simulations were close to concentrations observed in the biota. The agreement between 137Cs concentrations and simulations in bottom invertebrates supported our assumption that bottom sediments are not a major source of Cs to the biota. Our specific activity and concentration model was compared to the radionuclide content model, the model used in terrestrial ecosystems. For biotic components of aquatic ecosystems, values of aij, the transfer coefficients of our model, are easily estimated from turnover rates of radiocesium in individual organisms in the laboratory. Values of lij, transfer coefficients of the radionuclide content model, are estimated from aij but require, in addition, estimates of compartment biomasses, information which for most aquatic ecosystems is neither available nor easily obtained.

Venkatesh, S., M. Donelan, H. Graber, P.C. LIU, D.J. SCHWAB, and M. Skafel. Finite depth wind waves--a preliminary analysis of data from a field study on Lake St. Clair. Seventh Conference on Ocean-Atmosphere Interaction, Anaheim, CA, February 1-5, 1988. American Meteorological Society, Boston, MA, 154-156 (1988).

No abstract.

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