GLERL Publications Abstracts: FY 1982

Publications List Key
Capitalized names represent GLERL authors.
* = Not available from GLERL.
** = Available in GLERL Library only.

BENNETT, J.R., and D.J. SCHWAB. Calculation of the rotational normal modes of oceans and lakes with general orthogonal coordinates. Journal of Computational Physics 44(2):359-376 (1981).

A finite-difference method for computing the frequency and structure of the rotational modes of oscillation of enclosed seas is tested against known solutions for: (1) a circular basin with a parabolic depth law, (2) a circular, flat basin with a linear variation of the Coriolis parameter, and (3) an elliptic paraboloid. Several higher modes of the elliptic paraboloid are also calculated. The method uses the non-divergent assumption and solves the barotropic vorticity equation in general orthogonal coordinates generated by a conformal map of the shoreline onto the unit circle. The numerical procedure for calculating the conformal map of an arbitrarily shaped basin is presented.

BOLSENGA, S.J. Mathematical models of slope development--A review. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48 pp. (1982).

No abstract.

BOLSENGA, S.J., and R.D. KISTLER. A dual spectroradiometer system for measuring spectral reflectances. Journal of Applied Meteorology 21:642-647 (1982).

A dual spectroradiometer system for field measurements of spectral reflectances over natural surfaces was developed and tested. Tests show that simultaneous incident and reflected readings are highly desirable to eliminate errors in computing spectral reflectances from both field and laboratory data where changes in incident radiation are likely to occur.

Bowers, J.A., and H.A. VANDERPLOEG. In situ predatory behavior of Mysis relicta in Lake Michigan. Hydrobiologia 93:121-131 (1982).

Selectivity coefficients (W') and predation rates on Lake Michigan zooplankton were determined for Mysis relicta during spring through fall using an in situ method. W' values indicated the following ranked order of prey preference: Cladocera > copepod copepodites and copepod nauplii > adult diaptomids and cyclopoids. With few exceptions, W' values for different prey categories remained fairly constant despite greatly changing relative abundances of prey. Predation rates and prey selectivity were similar in most cases to those determined in laboratory studies. Ingestion rates (percent dry body weight day-1) were correlated to total prey biomass (r = 0.38) and to effective prey biomass (r = 0.85), where the weighting factors were overall mean selectivity coefficients for the different prey categories. This result suggested that seasonally varying composition of prey caused much of the variation in ingestion rates among experiments. Feeding trials performed at the same depth with daytime and nighttime assemblages of zooplankton indicated that Cladocera may escape heavy Mysis predation at night by migrating from the metalimnetic-hypolimnetic interface into the epilimnion.

CHAPRA, S.C. A budget model accounting for the positional availability of phosphorus in lakes. Water Research 16:205-209 (1982).

The mass balance relationships of Piontelli & Tonnolli (Mem. Ist. Ital. Idrobiol. 17, 247-266, 1964) and Vollenweider (Archs Hydrobiol. 66, 1-36, 1969) are combined in a phosphorus budget model. This model accounts for both the rapid settling of allochthonous particles and the slow settling of autochthonous particles that remove phosphorus from the water column. The effect of resuspension of bottom sediments is modeled by making the apparent settling velocity a function of lake depth. The resuspension effect is important for lakes less than 10 m deep.

**CHAPRA, S.C. Long-term models of interactions between solids and contaminants in lakes. Ph.D. dissertation, The University of Michigan, Ann Arbor, MI, 190 pp. (1982).

This dissertation develops a computational framework for predicting toxic substance levels in lakes. A general model of the transport and fate of contaminants in a lake's bottom sediments is derived. The model accounts for the following processes: compaction, bioturbation, burial and diffusion. Reactions are via first order decay and equilibrium, sorption kinetics. The model is used to simulate profiles of a non-sorbing (chloride) and a strongly sorbing (21OPb) contaminant in the sediments of Lakes Ontario and Michigan. Simulations for variable and constant porosity conditions assess the effect of compaction on model computations. The results indicate that for the highly porous sediments common to the deposition zones of many lakes, compaction can be disregarded and a constant porosity model is an adequate approximation. The sediment model is coupled with a budget model of the water column. Because of the importance of organic matter in the transport and fate of certain toxicants, the sediment/water model distinguishes between organic solids produced within the lake an inorganic particulate matter delivered to the lake via runoff and atmospheric pathways. The sediment/water model is then coupled with a food chain model that computes both biomass and contaminant concentration for limnetic and benthic organisms. The total framework is used to compute levels of 239,240Pu, 137CS and PCB for Lake Michigan over the past thirty years. A major conclusion is that for order of magnitude estimates it is possible to uncouple the food chain from the particle/contaminant budget model. Thus, the relatively simpler budget model can be used to simulate the long-term concentration in the lake and a simple proportionality can be used to estimate levels in the food chain. A simplified, steady-state version of the model is derived for management purposes. This version is analogous to the algebraic and graphical procedures developed for lake eutrophication- however, the approach explicitly includes the sediment-water interactions investigated in the dissertation. Thus, although the methodology is easy to implement, it is based on sound and internally consistent physical principles.

CROLEY, T.E.II. Great Lakes Basin runoff modeling. NOAA Technical Memorandum ERL GLERL-39, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB82-254228) 96 pp. (1982).

Large-scale watershed models are required to estimate basin runoff to the Great Lakes for use in routing determinations and operational hydrology studies. Data limitations, large-basin applicability, and economic efficiency preclude the use of existing large-watershed models. An interdependent tank-cascade model is described that uses a mass balance coupled with linear reservoir concepts. It is physically based and uses climatological considerations not possible for small watersheds; analytical solutions are employed to bypass numerical inaccuracies. Snowmelt and net supply computations are separable from the mass balance determinations and are based on a simple heat balance. Partial area concepts are used to determine infiltration and surface runoff. Losses are determined from joint consideration of available energy for actual and potential evapotranspiration and of available moisture in the soil horizons by using climatological concepts. Heuristic calibration procedures are described that give insight into the use of the model. The model is applied, for a 30-d computation interval, to the Genesee River Basin in New York State and compared with past 6-h computation interval applications of the SSARR and NWSH models to the same data set.

CROLEY, T.E.II. Unsteady overland sedimentation. Journal of Hydrology 56:325-346 (1982).

Sediment flux to fluid flow in a rill is represented with physically based models for simultaneous sediment entrainment (detachment), deposition (settlement) and lateral inflow, and is shown to be an improvement over existing concepts for describing low sediment concentrations. Unsteady flow and sedimentation in overland rills are then described by continuity equations and approximations for flow, entrainment and transport capacity. The equations are reduced, for an assumed rill pattern on an overland plot, to one-dimensional equations of motion which do not utilize sheet flow approximations. The method of characteristics' solution to these equations for uniform rainfall excess yields both the hydrograph (rising limb and uniform crest) and a three-part sediment concentration graph, with a predicted time lag between peaks of these graphs. The resulting model allows substitution of reasonable parameter values as opposed to the requirements of conventional sheet flow approximations. Sediment concentration is given by steady-uniform transport capacity equations only when the flow is steady-uniform (no lateral inflow) over infinite channel length (or recirculating flume) or when the steady-uniform transport capacity concentration in the rill is equal to the lateral inflow concentration. It then appears that rill topographies develop to the point where the latter condition is satisfied. Boundary conditions on the first derivative of sediment concentration with time suggest constraints on the form of the equations for fluid flow, entrainment, and transport capacity which agree well with empirical evidence. General observations on the solution are made which outline the expected nature of overland sedimentation.

CROLEY, T.E.II, D.G. Carvey, and J.G. Robb. Watershed evaluation and research system application. In Applied Modeling in Catchment Hydrology, V.P. Singh (ed.). Water Resources Publications, Littleton, CO, 229-258 (1982).

The integration of rainfall-runoff and economic models provides a basis for studying alternatives for adjusting and constraining resource use in accordance with social needs and the capacity of natural resources to support such activities. USDA's Economic Research Service (ERS) and the University of Iowa's Institute for Hydraulic Research (IIHR) have cooperated to develop and apply an integrated Watershed Evaluation and Research System (WATERS). WATERS incorporates rainfall-runoff modeling based on a distributed-parameter watershed model. WATERS analyses resource uses including agricultural alternatives with some soil conservation and water quality management practices. Rainfall events and resource uses are reflected through infiltration, overland runoff, sediment production, and overland transport models. Channel flow and transport are included. Economic effects are described through an agricultural budget generator. A multiple objective programming model uses hydrologic and economic information for simultaneous optimizations of generally noncommensurable objectives and related tradeoff analyses. WATERS is applied to a small Iowa watershed to study hydrologic and economic relationships for several cropping and conservation management alternatives and a selected storm of record. Multiple optimizations were run for four objectives, of which two profit objectives are commensurable: maximize crop profits, maximize rotation profits, minimize soil loss, and minimize runoff. While maximums (minimums) generally aren't attained, analytical results suggest the following: if decision makers desire high crop profit, it will be accompanied by a low rotation profit, moderate runoff, and fairly high soil loss. Attaining a high rotation profit results in a moderate crop profit, high runoff, and high soil loss. If runoff reduction is emphasized, moderate crop and rotation profits result with fairly low soil loss. Emphasizing soil loss reduction, produces low crop and rotation profits with moderate runoff. This type of information can assist decision makers in forming value judgments concerning the relative level of importance of each objective in question thus facilitating the tradeoffs that are necessary to achieve a desired mix of objectives.

Dannelongue, H.H., G.A. Meadows, and R.L. PICKETT. The growth and decay of nearshore circulation. Proceedings, Mechanics of Oil Slicks Conference, Paris, France, September 7-9, 1991. International Association for Hydraulic Research, 107-120 (1981).

The understanding of nearshore zone dynamics is a crucial prerequisite for the prediction of oil slick advection and for the establishment of efficient barriers. More precisely, separating the longshore current into its various driving components allows a better forecast of the nearshore zone behavior when it is oil-covered. Water surface elevation, nearshore current velocities (longshore and onshore-offshore) and wind speed and direction were monitored continuously during the growth and decay of an atmospheric perturbation on the Great Lakes. This study has provided an accurate three-dimensional mapping of the nearshore circulation (onshore-offshore, long-shore and temporal). The response of the surf-zone to atmospheric forcing, including its time-dependent behavior, was analyzed. The resultant surf zone circulation was found to differ greatly in both magnitude and direction from that predicted by a purely wind-driven circulation model developed explicitly for oil slick prediction on the Great Lakes.

DERECKI, J.A. Effect of channel changes in the St. Clair River since 1900. NOAA Technical Memorandum ERL GLERL-40, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB82-258245) 20 pp. (1982).

Periodic man-made changes in the outlet of Lake Huron through the St. Clair River date back to the middle of the last century. These artificial channel changes are well documented during the present century and consist of dredging for commercial gravel removal in the upper river during 1908-25 and uncompensated navigation improvements for the 25-ft and 27-ft projects completed in 1933 and 1962, respectively. The total effect of these changes on the levels of Lakes Michigan and Huron (hydraulically one lake) and on the upper St. Clair River profile was determined with dynamic flow models. The ultimate effect of the above dredging was a permanent lowering of the lake levels 0.27 m, which represents a tremendous loss of fresh water resource (32 km3). This total lowering of lake levels is 0.09 m higher than previous estimates, but present determinations represent a more sophisticated approach. It is unfortunate that appropriate hydraulic data for the previous century are not available for the application of this method. In the late 1880's the levels of Lake Michigan-Huron dropped by 0.8 m. In contrast to the other Great Lakes, the levels of these two lakes remained depressed afterwards, producing controversy about the reasons for this unexplained drop, namely, reduced precipitation and/or dredging. Existing estimates for the lake level drop due to unspecified dredging prior to 1900 vary from under 0.1 m to over 0.4 m, an unacceptably large difference. Reduction of lake levels du to precipitation or dredging implies different lake level behavior in the future, which complicates water resource studies based on the analysis of lake levels and related outflows.

DERECKI, J.A. Effect of the 1981 Fort Gratiot gage modifications on the hydraulic regime of the St. Clair River. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (1982).

No abstract.

DERECKI, J.A. Method used by Great Lakes Environmental Research Laboratory (U.S.). In Lakes Michigan-Huron Outflows, St. Clair and Detroit Rivers 1900-1978, Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data, International Joint Commission, 15-19 (1982).

No abstract.

DERECKI, J.A. Operational estimates of Lake Superior evaporation based on IFYGL findings. Water Resources Research 17(5):1453-1462 (1981).

Monthly evaporation from Lake Superior was determined for individual years of a 34-year period, 1942-1975, by an improved mass transfer method. This method permits timely evaporation estimates from readily available land-based meteorological data and represents the most practical approach for determining operational evaporation estimates for the Great Lakes. Method improvements consist of refinements in the mass transfer coefficient and the land-to-lake data adjustments derived from extensive investigations conducted on Lake Ontario during the International Field Year for the Great Lakes. The mass transfer coefficient and data adjustments are based on atmospheric stability considerations applicable to Lake Superior. Because of extensive ice cover on the lake, the standard overwater mass transfer results were also adjusted for the effects of ice cover during winter. The mass transfer evaporation estimates are verified by the water budget determinations, which for Lake Superior offer firm estimate of evaporation but are impractical for operational applications because of long delays in the availability of data. In contrast to the other Great Lakes, all hydrologic components of the Lake Superior water budget are of the same order of magnitude, with comparable errors, eliminating the possibility of large residual errors in computed evaporation. Evaporation values as determined by the two methods agree reasonably well for both seasonal distribution and the annual total, with the resulting long-term annual value of approximately 500 mm. The ice cover adjustment reduced the average annual mass transfer overwater evaporation by 13% and produced much better agreement with the water budget seasonal distribution and annual values. Generally, the ice cover reduction of evaporation could be estimated by reducing the lake area by appropriate ice cover.

DERECKI, J.A. Stability effects on Great Lakes evaporation. Journal of Great Lakes Research 7(4):357-362 (1981).

The effects of atmospheric stability on Great Lakes evaporation computed by the modified mass transfer method have been evaluated by analysis of stability effects on the variable mass transfer coefficient, land to lake data adjustments, and ice-cover reduction of evaporation during winter. The Great Lakes which produce extreme results, Lakes Superior and Erie, and a much smaller water body within the Great Lakes chain, Lake St. Clair, were studied Comparison of these evaporation estimates with previous studies, which excluded variable stability effects, shows that the previous studies of Lake Superior produced generally similar total annual water loss from the lake, but significantly overestimated both the seasonal high evaporation and the condensation rates. These tended to balance each other. The atmospheric conditions over Lakes Erie and St. Clair do not become as strongly stable and they normally do not exhibit large condensation. Previous evaporation studies for these lakes indicate generally higher evaporation rates, with significant overestimation of the total annual water losses (25%).

EADIE, B.J., W.R. FAUST, and P.F. LANDRUM. Polycyclic aromatic hydrocarbons in the benthic organisms of the Great Lakes. Coastal Ocean Pollution Assessment News 2:4 (1982).

No abstract.

EADIE, B.J., W.R. FAUST, W.S. GARDNER, and T.F. NALEPA. Polycyclic aromatic hydrocarbons in sediments and associated benthos in Lake Erie. Chemosphere 11(2):185-191 (1982).

Polycyclic aromatic hydrocarbons (PAH) were analyzed in surficial sediments and benthic organisms in southwestern Lake Erie near a large coal fired power plant. Sediment concentrations (530-770 ppb PAH) were relatively homogenous throughout most of the 150 km2 area, although river and nearshore concentrations reached nearly 4 ppm. Oligochaete worms and chironomid midges were near equilibrium with local sediments except for enhanced concentrations in nearshore midges.

EADIE, B.J., M.J. McCORMICK, C. Rice, P. LEVON, and M. Simmons. An equilibrium model for the partitioning of synthetic organic compounds incorporating first-order decomposition. NOAA Technical Memorandum ERL GLERL-37, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB82-164427) 33 pp. (1981).

A simple equilibrium model incorporating several first-order decomposition pathways has been calibrated for DDT and PCB mixtures in a 1-m2 ecosystem with the characteristics of Lake Michigan. This exercise has revealed the weakness in currently available process-rate information. This model, as constructed, yields some valuable insights into the environmental pathways of hydrophobic organic contaminants in aquatic ecosystems.

EADIE, B.J., S. NIHART, and J.A. ROBBINS. Study of early diagenesis of compounds in Great Lakes sediments is underway. Coastal Oceanography Climatology News 4:43 (1982).

No abstract.

GARDNER, W.S., P.F. LANDRUM, and D.A. Yates. Fractionation of metal forms in natural waters by size exclusion chromatography with inductively coupled argon plasma detection. Analytical Chemistry 54:1196-1198 (1982).

No abstract.

GARDNER, W.S., and G.A. Paffenhofer. Nitrogen regeneration by the subtropical marine copepod Eucalanus pileatus. Journal of Plankton Research 4(3):725-734 (1982).

Ammonium release rates by individual marine copepods (Eucalanus pileatus) were examined kinetically over successive 10-min intervals after the animals were exposed to three concentrations of the diatom Thalassiosira fluviatilis as food. Food concentrations spanned those expected in the natural environment. "Well-fed" (3mm3 T. fluviatilis 1-1) copepods released ammonium significantly (p<0.05) faster than those fed zero or low concentrations of food, but differences were not dramatic. Mean excretion rates (+/-SE) for animals removed from food for 18-22 h [30 +/- 6 nmol NH4 (mg ash free dry weight)-1h-1] were ~ 60% of those for "well-fed" animals [49 +/- 8 nmol NH4 (mg ash free dry weight)-1h-1]. Continued high release rates after extended periods without good suggest that E. pileatus must feed frequently in nature to maintain an adequate nitrogen balance. Depending on food concentration, animals released ammonium at rates ranging from 40 to >100% of their N ingestion rates over the previous 18-22 h. Long-term (4-6 h) kinetic excretion experiments with "well-fed" animals indicated that, on average, release rates decreased with time after food removal, but patterns varied among individual copepods. In addition to ammonium release, o-phthalaldehyde reactive amino acid nitrogen was occasionally released by E. pileatus in large "spurt events" lasting from 20 to 60 min.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Annual Report for the Great Lakes Environmental Research Laboratory, FY 1981. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 32 pp. (1981).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Detailed technical plan for the Great Lakes Environmental Research Laboratory. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 257 pp. (1982).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Technical plan for the Great Lakes Environmental Research Laboratory. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 68 pp. (1982).

No abstract.

*GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY, and The University of Michigan. Second annual progress report to the Office of Marine Pollution Assessment. In The Cycling of Toxic Organic Substances in the Great Lakes Ecosystem, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 110 pp. (1981).

No abstract.

*GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY, The University of Michigan, and The University of Minnesota. Third semiannual progress report to the Office of Marine Pollution Assessment, NOAA. In The Cycling of Toxic Organic Substances in the Great Lakes Ecosystem, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (1982).

No abstract.

GREENE, G.M. Breakup of ice cover occurs early on St. Lawrence River in 1981. Coastal Oceanography and Climatology News 4:2-3 (1981).

No abstract.

HAWLEY, N. Settling velocity distribution of natural aggregates. Journal of Geophysical Research 87(C12):9489-9498 (1982).

An analysis of previous experimental determinations of aggregate settling rates for particles <100 mm in diameter shows that these particles fall significantly more quickly than Stokes' law predicts, with the deviations being most pronounced for smaller particles. This implies that previous sediment flux calculations which have used a form of Stokes' law to obtain aggregate velocities may have signifcantly underestimated the contribution from the smaller aggregates. The measured fall velocity distributions are described as the sum of normally distributed populations (four for the lacustrine data, two for the marine) whose means, standard deviations, and weights have been determined. Sample calculations of collision frequency show that because of the increased settling velocities and the use of a distribution of velocities for a given particle size, collisions due to differential settling rates are the governing nonbiological process in the formation of natural aggregates.

**Hore, R.C., A.P. PINSAK, and D.J. Vallery. Annex F--Consumptive water use.Report to the International Joint Commission by the International Great Lakes Diversions and Consumptive Uses Study Board. U.S. Department of the Army, Corps of Engineers, Detroit, MI, F-151 pp. (1981).

No abstract.

HUANG, J.C.K., and J.H. SAYLOR. Vorticity waves in a shallow basin. Dynamics of Atmospheres and Oceans 6:177-196 (1982).

Observed oscillatory current patterns in the southern basin of Lake Michigan, with a distinctive peak in the energy spectrum at a period of about 90 h, are simulated using a linear potential vorticity conservation model. Solutions of the forced vorticity equation in a paraboloidal basin show rotational, oscillatory motions tuned to the low-frequency topographic nodes that are very similar to the observed flow patterns. Topography-controlled vorticity waves are excited most effectively by wind episodes with frequency nearly in resonance with the topographic modes. Bottom resistance has no significant effect on the frequency equation; it simply decays the waves slowly in the open lake and more quickly near the coast. Flow patterns of both the gravest free vorticity wave and the corresponding forced wave consist of two opposite circulation cells separated by a null streamline through the center of the basin and rotating cyclonically near the free wave and atmospheric forcing frequencies, respectively. Interactions between the forced and free waves result in an apparent rotational pattern with a frequency the median of the two. A combination of elliptic--paraboloidal basin and shorter period forced modes can approximate the observed Lake Michigan response. Doppler shift, due to the persistence of cyclonic vorticity in the flow field, is also determined to be a factor in shifting the elliptical basin mode to a higher frequency,

HUANG, J.C.K., and P.W. SLOSS. Simulation and verification of Lake Ontario's mean state. Journal of Physical Oceanography 11(11):1548-1566 (1981).

A numerical dynamic model based on primitive equations has been developed for Lake Ontario. Many experimental tests for parameter selections and alternative formulations of physical processes in the model were carried out. Two simulations, both repeated in July and December 1972, one under constant atmospheric forcing and the other under hourly time-dependent, spatially varying atmospheric forcing, are presented here. With constant southwesterly wind parallel to the major axis of the lake, as was the case in both July and December 1972, the steady-state lake circulation forms a typical two-gyre wind-driven pattern with currents flowing with the wind in both coastal regions and return flow in the middle of the take. The monthly mean currents of the hourly time-dependent variable-forcing simulation of December have a pattern similar to that of the constant-forcing case, while the mean currents of the July time-dependent variable-forcing simulation yield a single cyclonic circulation pattern with currents flowing against the mean wind in the north shore, which is totally different from the constant-forcing steady-state result. Both the monthly mean model currents of the time-dependent variable-forcing simulations agree very well with the monthly mean currents observed over Lake Ontario during the International Field Year for the Great Lakes (IFYGL). When the lake density is nearly homogeneous, with negligible thermal effects, as in December, the lake response is mostly barotropic. The induced circulation consists of dominantly wind-driven currents adjusted to the bottom topography with a thin Ekman layer on top of the geostrophically balanced currents in deep layers. Further simplification of the dynamics is a consequence of the linear nature of the model's behavior. The means of the time-dependent variable-forcing simulation merge to form the constant-forcing steady-state circulation. In July, however, the lake is stratified and both the wind-driven and thermal-driven currents are important. It seems that the final circulation pattern in a lake depends mostly on the relative strengths of the thermally affected mechanisms and the wind-driven mechanism. Dominance of the former generally results in a one-gyre circulation pattern, while dominance of the latter results in a two-gyre circulation pattern. In a constant-forcing model, most of the thermally affected mechanisms, such as the rectified effect, the coastal mixing, dome-shaped isotherms, and horizontal and vertical density gradients, are obscured by the fully developed wind-driven steady-state currents. Employing such a model to simulate the stratified lake is definitely inadequate and misleading because only the time-dependent variable-forcing simulation results in a mean, single-gyre circulation pattern that matches the observations, while the constant-forcing still produces an unrealistic two-gyre circulation pattern for July 1972 (during IFYGL).

Hutter, K., and D.J. SCHWAB. Internal report on baroclinic channel models. Report prepared by Versuchsanstalt fur Wasserbau, Hydrologie, und Glaziologie. 21 pp. (1982).

The baroclinic seiches in two-layered basins are studied using the exact linear two-layer equations appropriate for channels and, correspondingly, the one-layer equations, in which the gravity constant is reduced and the depth function is replaced by the equivalent depth, see equation (1). This equivalent depth reduction is correct only for basins with uniform depth. It is shown here how the reduced equations should be used for basins with variable bathymetry.

KELLEY, R.N. Comparison of Great Lakes consumptive use impacts on water levels under Lake Superior regulation plans '1977' and '55' modification of the 1949 rule. GLERL Open File Report, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 3 pp. (1982).

No abstract.

Krezoski, J.R., and J.A. ROBBINS. Radiotracer studies of interactions between sediments and freshwater macrobenthos. Verhandlungen-Internationale Vereinigung Fur Theoretische und Angewandte Limnologie 21:382 (1981).

Gamma-emitting radioisotopes were used to study the effect of five species of benthic macrofauna, common to the North American Great Lakes, on the movement of solutes and particles in sediments. Rectangular plastic cells (5 x 3 x 45 cm) containing natural, sieved (<250 mm), sediment, stored in a temperature-regulated aquarium, were labeled with Cs 137, which binds strongly to sediment particles (Kd ~ 2000), and Na-22, which is weakly coupled to sediments (Kd ~ 0.5). Subsequently, both Na-22 (an indicator of solute movement) and Cs-137 (an indicator of particle transport) moved downward into sediments in response to organism activity in the cells. Vertical distributions of the isotopes were determined simultaneously at daily to weekly intervals for nearly three months using a well-collimated NaI gamma detection system (Robbins et al. 1979). In three replicate cells with the annelid Stylodrilus heringianus (6.7 x 104 m-2), which feeds at 4-6 cm and defecates at the sediment surface, the Cs-137 labeled layer was buried at a rate of 0.12 +/- 0.005 cm day-1 (11.6 +/- 0.2 oC) while the downward movement of Na-22, characterized as simple diffusion (no advection), implied a diffusion coefficient, Db, of 1.33 +/- 0.07 x 10-5cm2 sec-1. In two replicate cells with the amphipod Pontoporeia hoyi (4.7 x 103 m-2) Db was 1.43 +/- 0.25 x 10-5 cm2 sec-1 (10.4 +/- 0.2 oC). The downward smearing of Cs-137 labeled particles by amphipods is well characterized as a non-advective eddy diffusion process with an eddy diffusion coefficient, Kb, of 1.24 +/- 0.17 x 10-7 cm2 sec-1. In control cells with no animals Kb = 0.0 while Db = 0.95 +/- 0.02 x 10-5 cm2 sec-1. In a special control cell with worm tubes but no live worms, there was no enhancement of the rate of solute transport. Thus, the presence of either species markedly enhances the transport of solutes into sediments (~50%) and in the case of oligochaetes the effect is primarily due to their dynamic interactions with the sediments rather than to alterations in the sediment matrix. In other cells with Chironomus tentans (4.0 x 103 m-2), Pisidium sp. (4.0 x 103 m-2) and Sphaerium sp. (2.7 x 103 m-2) no significant movement of labeled particles occurred.

LANG, G.A., and S.C. CHAPRA. Documentation of SED--A sediment/water column contaminant model. NOAA Technical Memorandum ERL GLERL-41, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB83-169946) 49 pp. (1982).

Presented is documentation of a mathematical model developed to simulate the contaminant level in the sediments and overlying water column of a well-mixed lake. The contaminant is segmented into three fractions, organic, inorganic, and dissolved, each with different physical and kinetic properties. The principal application of the model would be prediction of the year-to-year and steady-state response of the water column and sediments to changes in the loading rate of contaminant and/or particulate matter. A simulation of 239Pu in Lake Michigan is presented as an example of the model's use.

Lehman, J.T., and D. SCAVIA. Microscale patchiness of nutrients in plankton communities. Science 216:729-730 (1982).

Autoradiography was used to identify the presence of nutrient patches produced by zooplankton. Algal cells which encounter patches of phosphorus-33 released by swiming animals accumulate more label than cells that do not enter the patches. Differential labeling of algae does not occur when turbulence in the fluid is increased by stirring. Nutrient patchiness at the scale of milimeters or less in nature probably influences the course of competition and coexistence among the phytoplankton.

Lehman, J.T., and D. SCAVIA. Microscale nutrient patches produced by zooplankton. Proceedings of the National Academy of Sciences of the United States of America, 79:5001-5005 (1982).

Both track autoradiography and grain-density autoradiography show that individual zooplankton create miniature patches of dissolved nutrients and that algae exploit those regions to absorb phosphate. The patches are short lived and con be dispersed artificially by small-scale turbulence. Our data support a simple model of encounters between algae and nutrient plumes produced by swimming zooplankton.

Leversee, G.J., J.P. Giesy, P.F. LANDRUM, S. Bartell, S. Gerould, M. Bruno, A. Spacie, J. Bonling, J. Haddock, and T. Fannin. Disposition of benzo(a)pyrene in aquatic system components: Periphyton, chironomids, daphnia, fish. In Chemical Analysis and Biological Fate: Polynuclear Aromatic HydroCarbons, M. Cooke and A.J. Dennis (eds.). Batelle Press, Columbus, OH, 357-366 (1981).

No abstract.

MILLER, G.S., and J.H. SAYLOR. Winter temperature structure in Lake Huron. Journal of Great Lakes Research 7:201-206 (1981).

Water temperatures at depths 15, 25, and 50 m below the surface and 2 m above the bottom were continuously recorded at 17 mooring sites in Lake Huron during the 1974-75 winter. Monthly isotherm patterns show that the shore regions rapidly cooled to near 0 oC by early February, while the deep northern basin reached a minimum of 1.5 oC in mid-April. The initial stages of the fall overturn at depths greater than 100 m exhibited temperature fluctuations due to wind mixing and advection. By mid- to lake December, Lake Huron was isothermal at all recording stations and remained so through April, except in the deep basins where a weak winter thermocline developed in March.

QUIGLEY, M.A. Freshwater macroinvertebrates. Journal of Water Pollution Control Federation 54:868-877 (1982).

No abstract.

QUINN, F.H. Secular changes in annual and seasonal Great Lakes precipitation, 1854-1979, and their implications for Great Lakes water resource studies. Water Resources Research 17(6):1619-1624 (1981).

An analysis of annual precipitation over the Great Lakes Basin from 1854 to 1979 indicates two distinct precipitation regimes. The first, a relatively dry regime, lasted from the mid-1880's until the late 1930's. This was followed by a relatively wet regime, which continues to the present. The analysis also indicates that the annual precipitation regime prior to the mid-1880's was similar to the present regime. The change in precipitation appears to be the result of increased precipitation during spring and summer. A continuation of the present wet regime will present many challenges for water resource managers and planners concerned with lake regulation, water supply forecasting, coastal zone management, and water allocation and uses in the Great Lakes Basin.

QUINN, F.H. Trends and extremes of Lake Erie water supplies. Proceedings, International Symposium on Hydrometeorology, Denver, CO, June 13-17, 1982. American Water Resources Association, Minneapolis, MN, 267-270 (1982).

Lake Erie is the fourth largest of the Great Lakes, with a surface area of 25,700 km2 and a land basin area of 61,100 km2. Its water is derived from the upper Great Lakes and its own net basin supply consisting of precipitation, runoff, and lake evaporation. In this study, a data base consisting of monthly time series of air temperature, precipitation, runoff, and lake evaporation is used to examine trends and extremes in the net basin supply. This averages about 62 cm, with extremes ranging from 0.0 cm in 1934 to 145 cm in 1950. Of particular note is an apparent major change in the supplies occurring during the lake 1930's. The average annual basin supplies for 1940-79 were approximately 50 percent greater than for 1900-39. A monthly climatic water balance model was developed and calibrated to analyze the impact of changes in air temperature and precipitation regimes on the basin runoff. Particularly emphasized in the study are the conditions causing an increase in water supplies during the present regime, the record low Lake Erie water levels of 1964, and the extreme high levels of 1952 and the early 1970's. Future applications of the model are also discussed.

QUINN, F.H., R.A. ASSEL, and D.W. GASKILL. An evaluation of the impact of the Niagara River ice boom on the air temperature regime at Buffalo, New York. Journal of Applied Meteorology 21(3):342-349 (1982).

The objective of this study was to determine if the Niagara river ice boom has prolonged the Lake Erie ice cover at Buffalo, New York, resulting in significant changes in the spring warm-up of Lake Erie and longer, colder winters in the area. Statistical analysis of Buffalo air temperatures compared with those for Lockport, NY does not reveal statistically significant cooling in the climate oat Buffalo related to the operation of the ice boom. However, because of the distance of the airport (where the temperature gage is located from the shore zone, the possibility of a localized effect of small magnitude within the vicinity of the ice boom cannot be ruled out. A comparison of the water temperature at the Buffalo intake as recorded in pre- and post-boom years also indicates that the ice boom has not had an impact on the timing of the spring rise in Lake Erie water temperature at Buffalo. Analysis of winter temperature trends since 1989 shows that the winter severity at Buffalo follows a general pattern characteristic not only of the region around the eastern end of Lake Erie but also of the Great Lakes Region as a whole. Winters have become colder since the installation of the ice boom, but these colder winters are part of a general climatic trend toward more severe winters beginning in 1958. Thus, there is no evidence to suggest that the ice boom has increased winter severity or duration at Buffalo relative to other areas around the Great Lakes.

QUINN, F.H., and T.E. CROLEY. The role of precipitation climatology in hydrologic design and planning on the Laurentian Great Lakes. Proceedings, Fourth Conference on Hydrometeorology, Reno, NV, October 7-9, 1981. American Meteorological Society, Boston, MA, 7-11 (1981).

No abstract.

**ROBBINS, J.A. Sediments of Saginaw Bay, Lake Huron: Elemental composition and accumulation rates. Final report to the U.S. Environmental Protection Agency, Grant No. R8040686, Environmental Research Laboratory-Duluth, Office of Research and Development, U.S. EPA, Duluth, MN, 103 pp. (1982).

During the period from 1975 through 1978, sediment cores and grab samples were obtained from over 100 sites in lower Saginaw Bay. Selected samples were analyzed for grain size, organic and inorganic carbon, over 30 elements and both cesium-137 and lead-210. The study has revealed an extensive mud deposit in the lower bay covering about 400 km2 oriented approximately with bathymetric contours. The clay content of this deposit exceeds 50% toward the center with the mean grain size increasing toward deposit margins. Calcium family elements (Ca, Mg, and inorganic carbon) are preferentially concentrated at the southwestern end of the deposit either because of the distribution of source materials or because of prevailing currents in the system. In contrast, iron and organic carbon exhibit highest concentrations in sediments with highest content of clay-size particles. most other elements, including contaminant metals (Cr, Cu, Ni, Pb, An) have surface concentrations which correlate strongly with concentrations of iron and organic carbon (r>0.9; N = 30). Vertical distributions of radionuclides and contaminant metals reveal a zone of constant activity (or concentration) which extends from the sediment-water interface to depths ranging from 10 to 25 cm. This zone of uniform composition varies systematically within the deposit, tending to be greatest toward the center, and is probably the result of extensive mixing by zoobenthos (predominantly oligochaetes). About 90% of the zoobenthos occur within the zone of mixing determined radiometrically. Benthos densities range from 10,000 to 50,000 per m2 and are sufficient to completely mix sediments annually. Because of extensive mixing, sedimentation rates may not be reliably determined from profile for Cs-137 in this system. However, lead-210 dating appears valid and yields sedimentation rates ranging from about 0.07 to 0.24 g/cm2/yr (0.1-0.6 cm/yr). Highest rates occur toward the southwestern end of the deposit and decrease with increasing distance from the mouth of the Saginaw River. Radiometric mixed depths, in combination with sedimentation rate values, provide estimates of particle residence times in the mixed layer ranging from 11 to 60 years and averaging 30 years. Contaminant metal deposition rates as of 1975 are estimated suing a model of steady-state mixing and exponential loading with a 20-year doubling time in combination with sedimentation rate data. Annual loadings are estimated (in metric tons/year) as: Cr, 54; Cu, 28; Ni, 30: P, 420; Pb, 40, and Zn, 86. Surface concentrations of contaminant metals (and most other elements) are consistently lower in the bay mud deposits than in open lake deposits. Intense local sources do not lead to higher concentrations within the deposit mainly because of extensive downward reworking of surface materials, and to a lesser degree, because of dilution by inert allochthonous materials. When corrected for "dilution" effects, concentration of chromium are considerably higher in the bay muds. Relative to underlying sediments, the contaminant metals are highly enriched in surface materials and mean vertically integrated amounts (exceeding background) levels (mg/cm2) are: Cr, 280; Cu, 160; Ni, 160; Pb, 230; and Zn, 490). These values far exceed the excess element accumulation in deposits of the open lake. Thus, while surface concentrations of contaminant elements, with the exception of chromium, are not particularly distinctive, the vertically integrated amounts are strikingly high and illustrate the effectiveness of vertical reworking processes in diluting contaminants reaching the mud. the total amount of cesium-137 stored in the deposits is about 64 Ci compared with an estimated 158 Ci deposited over the same area from cumulative atmospheric fallout. As tributary contributions may be ignored (but possibly not exchanged from the open lake) the muds are no more than 40% efficient in retention of the radionuclide. Total inventories of metal contaminants in the lower bay (metric tons) are: Cr, 1,000; Cu, 590; Ni, 590; P, 21,000; Pb, 850; and Zn, 1,800. Fluxes of nutrients from cores collected during the period from April through November 1978 were determined from changes in concentrations in water overlying sediments incubated at prevailing in situ temperatures. Mean values for the period were: P, -530 mg/cm2/yr; N(NH3), +200 mg/cm2/yr; N(NO3), -360 mg/cm2/yr; and Si, 3,000 mg/cm2/yr. Releases of Si constitute a major input of Si into the Bay. The flux of silicon from sediments exhibits an annual cycle ranging from about 1,500 mg/cm2/yr in the spring to a maximum of about 6,000 mg/cm2/yr in August. The mean flux may be reliably predicted from thermodynamic expressions and the sediment temperature. During the fall months the flux (at constant temperature) is strongly correlated with the numbers of chironomid larvae present. Correlations between other nutrient fluxes and organism densities are generally insignificant. The mean flux of silicon based on pore water concentration gradients and estimates of the effective molecular diffusion coefficient were only about 660 mg Si/cm2/yr. Significantly higher direct fluxes suggest that Si release from sediments is not diffusion-limited but dependent on the rate at which materials dissolve at the sediment-water interface.

ROBBINS, J.A. Stratigraphic and dynamic effects of sediment reworking by Great Lakes zoobenthos. Hydrobiologia 92:611-622 (1982).

Recent sediments of the North American Great Lakes are inhabited by numerous species of macrobenthos which alter the physical and chemical properties of sediments and modify interface transport characteristics. Distributions of such radionuclides as cesium-137, lead-210, and isotopes of plutonium exhibit a zone of constant activity extending down from the sediment-water interface from 1 to 15 cm. Recent studies have confirmed that radiometrically determined mixed depths are consistent with the vertical distribution of oligochaete worms and the amphipod, Pontoporeia hoyi. Generally, 90% of the benthos are contained within the radiometrically defined mixed zone. Where comparisons are possible, rates of sediment reworking by "conveyor belt" species are comparable to or exceed sedimentation rates. Systematic variations in the mixed depth occur within depositional basins with greatest depths tending to be associated with least consolidated, organically rich materials. A quantitative steady-state mixing model accounts satisfactorily for observed radioactivity and heavy metal profiles. Bioturbation appears to be an important process, limiting the resolution with which historical records of particle-associated contaminants may be reconstructed from sediment cores. As bioturbation serves to maintain contact of contaminated sediments with overlying water, this time may also characterize the long-term lake recovery for contaminants removed by burial. As the time varies with location, a mean for an entire lake is not well known, but is on the order of 20 years for Lake Huron.

SCAVIA, D. Use and interpretation of detailed, mechanistic models of phytoplankton dynamics. In Phytoplankton-Environmental Interactions in Reservoirs, Technical Report E-81-13, Vol. 1, M.W. Lorenzen (ed.). U.S. Army Corps of Engineers, Waterways Experimental Station, Vicksberg, MS, 196-222 (1982).

Aquatic ecosystems comprise complex interactions of many biological, chemical, and physical processes. Effects of our impact on these systems are manifest also in complicated ways and at several levels of detail. For example, symptoms of eutrophication include increases in total algal biomass (a gross symptom) and shifts in algal dominance from diatoms to bluegreens (a detailed symptom). Complicated mechanistic models of the aquatic ecosystem are often suggested as a method of predicting such detailed symptoms because several of these models have been successful in simulating observed conditions in certain lakes. It is my opinion, however, based on experience with such models, that their use for long-term predictions is at best dubious. The main reason for this is that coefficient values (e.g., half-saturation constants, sinking rates, selective feeding constants for zooplankton) necessary to discern functional groups of phytoplankton (e.g., diatoms, greens, bluegreens) are not available; that is, overlap in measured coefficients for the individual functional groups precludes use of significantly different values.

SCAVIA, D., and M.J. McFarland. Phosphorus release patterns and the effects of reproductive stage and ecdysis in Daphnia magna. Canadian Journal of Fisheries and Aquatic Sciences 39(9):1310-1314 (1982).

Rates of continuous phosphorus release by individual Daphnia magna (0.3-0.9 mg dry weight) were measured using high performance liquid chromatography components in conjunction with a specially designed incubation flow cell. Within the temporal resolution of the technique (3 min), phosphorus release often appeared pulsed rather than only steady. We found significant variation in release rates among the different states of an individual's parthenogenetic reproductive cycle. Rates observed for animals carrying more nature embryos were lower than those earlier in the reproductive cycle. Rates of phosphorus release observed at and after ecdysis averaged 6.7 times higher than rates observed at other times.

SCHWAB, D.J. An inverse method for determining wind stress from water-level fluctuations. Dyn. Atmos. Oceans 6:251-278 (1982).

The hydrodynamic equations governing the water-level response of a lake to wind stress are inverted to determine wind stress from water-level fluctuations. In order to obtain a unique solution, the wind-stress field is represented in terms of a finite number of spatially dependent basis functions with time-dependent coefficients. The discretized version of the inverse equation is solved by a least-squares procedure to obtain the coefficients, and thereby the stress. The method is tested for several ideal cases with Lake Erie topography. Real water-level data is then used to determine hourly values of vector wind stress over Lake Erie for the period 5 May-31 October, 1979. Results are compared with measurements of wind speed and direction from buoys deployed in the lake. Calculated stress direction agrees with observed wind direction for wind speeds >7.5 m s-1. Under neutral conditions, calculated drag coefficients increase with wind speed from 1.53 x 10-3 for 7.5-10 m s-1 winds to 2.04 x 10-3 for 15-17.5 m s-1 winds. Drag coefficients are lower for stable conditions and higher for unstable conditions.

SCHWAB, D.J., J.R. BENNETT, and A.T. Jessup. A two-dimensional lake circulation modeling system. NOAA Technical Memorandum ERL GLERL-38, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB82-185372) 79 pp. (1981).

This report documents a series of computer programs for modeling circulation and water level fluctuations in well-mixed lakes . The FORTRAN code for three computer programs in included in an appendix. The programs are 1) a grid generation and modification program, 2) a free surface circulation model, and 3) a rigid lid circulation model. The models are based on the vertically-integrated shallow water equations and include Coriolis effects, but neglect nonlinear acceleration terms and horizontal diffusion of momentum. The user of the programs is required to supply bathymetric data, initial conditions, external forcing function, and a subroutine to generate the desired output parameters. Other than these requirements, the programs are very general and can serve as a basis for developing more complex models. A sample run of each program is included in a second appendix.

SCHWAB, D.J., P.C. LIU, J.R. BENNETT, G.A. Meadows, H.J. Schultz, J.E. CAMPBELL, and H.H. Dannelongue. Coastal boundary layer study records response of Lake Erie to storms. Coastal Oceanography and Climatology News 4(3):30-31 (1982).

No abstract.

SCHWAB, D.J., P.C. LIU, J.R. BENNETT, and G.A. Meadows. Lake Erie coastal boundary layer study measures flux of energy during storms. Coastal Oceanography and Climatology News 4:1 (1981).

No abstract.

SONZOGNI, W.C. Great Lakes: A look to the future. Proceedings, Oceans 82--Conference of the Marine Technology Society and the Institute of Electrical and Electronics Engineers, Washington, DC, September 20-22, 1982. Marine Technology Society and the Institute of Electrical and Electronics Engineers, 1186-1189 (1982).

Trace toxic contaminants will be the major research focus in the years ahead, since our inland seas appear to be especially sensitive to contaminants. During the 1970s, however, attention centered on pollution from municipal sewage treatment plants. By year 2000 controls are predicted to reduce phosphorus inputs to the Great Lakes from municipal sources by more than half current levels. Although this reduction will likely result in an overall improvement in water quality, it may also result in small reductions in fish yields. During the 1980s and 1990s it will be important to evaluate the effects of phosphorus pollution control programs have been cost-effective. Finally, because of water shortages around the world, water quantity will emerge as a major Great Lakes issue.

SONZOGNI, W.C., S.C. CHAPRA, D.E. ARMSTRONG, and T.J. LOGAN. Bioavailability of phosphorus inputs to lakes. Journal of Environmental Quality 11(4):555-563 (1982).

Interpretation of the potential bioavailability of phosphorus forms and fractions indicatessome of the P entering lakes may have a limited effect on lake productivity. Some P sources, such as land runoff, are often high in particulate P, significant portions of which cannot be utilized in the growth of algae and higher plants. Based on existing information (mostly from Great Lakes studies), potentially bioavailable P in tributaries generally does ont exceed 60% of the totalP and is often considerable less. Potentially bioavailable P is shown to correspond to the dissolved reactice P (DRP) plus the fraction of particulate inorganic P obtained by extraction with 0.1/V NaOH. Whether potentially bioavailable particilate P actually becomes available in a receiving water depdns onf actors such as the receiving water DRP concentration and the position (location) of the particle in the water. A mathematical model, combining two classical modeling approaches, is used to illustrate the importance of positional imitation. Considerationo f bioavailability in eutrophication-control strategies should lead to more cost-effective management.

SONZOGNI, W.C., W.S. Richardson, P. Rogers, and T.J. Monteith. Chloride pollution of the Great Lakes. Journal of Water Pollution Control 55(5):513-521 (1983).

Interpretation of the potential bioavailabiltiy of phosphorus forms and fractions indicates some of the P entering lakes may have a limited effect on lake productivity. Some P sources, such as land runoff, are often high in particulate P, significant portions of which cannot be utilized in the growth of algae and higher plants. Based on existing information (mostly from Great Lakes studies), potentially bioavailable P in tributaries generally does not exceed 60% of the total P and is often considerably less. Potentially bioavailable P is shown to correspond to the dissolved reactive P (DRP) plus the fraction of particulate inorganic P obtained by extraction with 0.1N NaOH. Whether potentially bioavailable particulate P actually becomes available in a receiving water depends on factors such as the receiving water depends on factors such as the receiving water DRP concentration and the position (location) of the particle in the water. A mathematical model, combining two classical modeling approaches, is used to illustrate the importance of positional limitation. Consideration of bioavailabiltiy in eutrophication-control strategies should lead to more cost-effective management.

TARAPCHAK, S.J., S.M. BIGELOW, and C. RUBITSCHUN. Overestimation of orthophosphorus concentrations in surface waters of southern Lake Michigan: Effects of acid and ammonium molybdate. Canadian Journal of Fisheries and Aquatic Sciences 39:296-304 (1982).

Measurements of ortho-phosphate (PO4-P) concentrations in natural waters obtained by molybdenum blue methodology are based on the assumption that molybdate (Mo) complexes only the PO4-P (in the absence of arsenate and silicate interference) to form the reductant-sensitive complex 12-molybdophophoric acid (12-MPA). The hypothesis that Mo causes or accelerates PO4-P release from bound sources or forms reductant-sensitive complexes with organic compounds (organic-PO4-MO) was tested by exposing filtered Lake Michigan water to acid, acid plus Mo simultaneously, and Mo, respectively, before measuring PO4-P by the Chamberlain-Shapiro extraction method. Not only does Mo accelerate hydrolysis in the presence of acid, but it also either causes hydrolysis in the presence of acid, but it also either causes hydrolysis or forms organic-PO4-Mo before samples are acidified. Although the relative amounts of 12-MPA and organic-PO4-MO formed in lake water cannot be assessed quantitatively, a major fraction of the blue color formed during routine analysis by this or by similar methods apparently is not the product of acid hydrolysis, but may also be due to reduction of organic-PO4-Mo. Future developments in molybdnum blue methodology aimed at minimizing hydrolysis must consider the sequence of reagent additions and Mo, as well as acid, contact times.

TARAPCHAK, S.J., and C. RUBITSCHUN. Comparisons of soluble reactive phosphorus and orthophosphorus concentrations at an offshore station in southern Lake Michigan. Journal of Great Lakes Research 7(3):290-298 (1981).

Soluble reactive phosphorus (SRP), measured by Harvey's method and the Chamberlain-Shapiro extraction technique from May to October 1976 in the epilimnion at an offshore station in southeastern Lake Michigan, was higher and more variable than previously published measurements, suggesting that phosphorus loaded into the nearshore zone is being transported into offshore water. Pronounced vertical variations in SRP occurred periodically in the water column and near the sediments, but accumulation in the hypolimnion over the period did not occur. Both molydenum blue methods overestimated maximum possible PO4 - P concentrations (MPPC) (as measured by Rigler's radiobioassay method) in water from 4 m by up to two orders of magnitude, but MPPC concentrations averaged 22.5% and 25.6% of the mean value measured by Harvey's method and by the extraction technique, respectively. Comparisons with radioassay estimates from other lakes suggest that MPPC concentrations may be lower in eutrophic than in mesotrophic or oligotrophic lakes.

VANDERPLOEG, H.A., J.A. Bowers, O. Chapelski, and H.K. SOO. Measuring in situ predation by Mysis relicta and observations on under-dispersed microdistributions of zooplankton. Hydrobiologia 93:109-119 (1982).

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.

VANDERPLOEG, H.A., and R.L. Ondricek-Fallscheer. Intersetule distances are a poor predictor of particle-retention efficiency in Diaptomus sicilis. Journal of Plankton Research 4(2):237-244 (1982).

The maximum excretion rate of NH4 (39 nmol mg dry wt-1 h-1) was directly measured for Daphnia pulex by measuring NH4 accumulation in bottles containing D. pulex and dense, satiating suspensions of heat-killed algae. Ammonium release rates in the algal suspensions were compared to those of individual animals removed from the suspension and placed in flow cells. Ammonium release rate, R (nmol mg dry wt-1 h-1), in the flow cell decreased very rapidly with time, t (min), after removal according to the relation R=26+25e-0.16t. Ammonium excretion obtained by the flow cell method after extrapolation to time zero was not significantly different from that obtained in the bottles. The considerable experiment-to-experiment variation in NH4 excretion was in large part correlated (r2 = 0.73) with the feeding rate on the algae.

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