GLERL Publications Abstracts: FY 1992

ASSEL, R.A. A computer tutorial for Great Lakes ice cover climatology. Proceedings, 48th Annual Eastern Snow Conference, Guelph, Ontario, Canada, June 5-7, 1991. 267-272 (1992).

An interactive menu-driven computer tutorial was developed to provide an overview of the annual Great Lakes ice cycle. The tutorial includes an animation to aid in visualizing the normal seasonal progression and the spatial patterns of ice cover for the base period 1960-1979 (Assel and Ratkos 1991). The computer algorithm was developed from data contained in the NOAA Great Lakes Ice Atlas (Assel et al. 1983). Computer diskettes needed to load and run the tutorial are being made available (Assel and Ratkos - in press) to the public at large. This paper abstracts information from that forthcoming publication.

ASSEL, R.A. Great Lakes winter weather 700-hPa PNA teleconnections. Monthly Weather Review 120(9):2156-2163 (1992).

A positive 700-hPa Pacific-North America (PNA) circulation index in December 1989 was replaced by a negative PNA index in January and February 1990. This circulation pattern reversal was associated with an anomaly reversal in air temperatures over the eastern half of the United States and anomaly reversals in the air temperature, snowfall, and ice cover of the Great Lakes. Evidence of PNA teleconnections with these Great Lakes climatic variables for a 20-winter base period is presented through correlations of anomalies in the monthly 700-hPa PNA index and PNA coordinates with anomalies in Great Lakes average monthly air temperature, snowfall, and ice cover.

ASSEL, R.A., and J.M. RATKOS. A computer tutorial and animation of the normal ice cycle of the Laurentian Great Lakes of North America for 1960-1979. NOAA Technical Memorandum ERL GLERL-76, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB92-129949/XAB) 31 pp. (1991).

An interactive, menu-driven computer tutorial was developed to provide an overview of the annual Great Lakes ice cycle. The tutorial includes an animation to aid in visualizing the seasonal progression and the spatial patterns of ice cover for the base period 1960-1979. The computer algorithm was developed from data contained in the NOAA Great Lakes Ice Atlas. This material is presented as a government technical memorandum to make the tutorial available to the public at large for educational purposes. A computer diskette needed to load and run the tutorial (on a Macintosh Plus with at least 2 megabytes of memory) is included as an appendix. Background information on the ice cover data and methods used to create the tutorial is followed by a description of the spatial and seasonal ice cover distribution patterns as related to lake bathymetry.

ASSEL, R.A., and D.M. Robertson. Climatic changes near the Great Lakes inferred from 141 year ice records. Proceedings, 5th International Meeting on Statistical Climatology, Toronto, Ontario, Canada, June 22-26, 1992. Environment Canada, Toronto, 81-85 (1992).

Freeze-up and break-up dates and duration of ice cover for lakes and rivers represent an integration of weather conditions prior to the specified event(s). Changes in mean ice conditions may be used as quantitative indicators of climatic changes if long homogenous ice records are accompanied by sufficiently homogenous air temperature records to calibrate the changes in mean ice cover in terms of climatic variables. Historical ice records dating back to 1855 are available for Lake Mendota, WI (located on the southwestern side of Lake Michigan) and back to 1851 for Grand Traverse Bay, MI (located on the northeastern side of Lake Michigan). Changes in the mean ice cover of these two systems were used to describe changes in fall, winter, and spring air temperatures in the area near the Great Lakes during the past 141 years.

Benner, R., G. Chin-Leo, W.S. GARDNER, B.J. EADIE, and J.B. COTNER. The fates and effects of riverine and shelf-derived DOM on Mississippi River plume/Gulf shelf processes. Proceedings, Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, New Orleans, LA, October 1-4, 1991. NOAA Coastal Ocean Program Office, TAMU-SG-92-109, 84-94 (1992).

A variety of chemical and biological measurements provided complementary information on the dynamics of dissolved organic matter (DOM) during summer and winter cruises in the Mississippi River Plume/Gulf Shelf region. Non-conservative mixing of dissolved organic carbon (DOC) between the River and open Gulf was observed during the summer cruise, indicating a substantial input of DOC at intermediate salinities (15-30%). Stable nitrogen isotope compositions of DOM isolated by ultrafiltration also indicated a source of freshly produced DOM at intermediate salinities during the summer, suggesting that phytoplankton were an important source of DOM in the plume. DOC mixing appeared to be fairly conservative during the winter cruise.
Calculation of areal bacterial demand for carbon indicated that bacteria consumed a substantial portion of the total carbon fixed by primary production in this region. The oxygen demand from growth of bacterioplankton in subsurface waters was sufficient to explain the occurrence of hypoxic conditions during the summer at stations where low oxygen levels were observed in bottom waters. Although more temporal data are needed to define seasonal trends accurately, bacterial activity, community respiration and nutrient regeneration rates were higher during the summer cruise than during the winter cruise. Rates of bacterial production, nitrogen regeneration and community respiration were highest at intermediate salinities in the plume, particularly during the summer. During both cruises, the proportion of total respiration and nutrient regeneration that were not accounted for by bacteria were consistently higher in the plume regions, where zooplankton grazing of particles may be relatively more important for nutrient regeneration than in regions where primary production was low.

BOLSENGA, S.J. Report. A review of Great Lakes ice research. Journal of Great Lakes Research 18(1):169-189 (1992).

A review of over 250 scientific and engineering articles on ice research in the Great Lakes covering the period 1906-91, with emphasis on the period 1960-91, shows a wide diversity of subject material. Studies on ice extent are the most prevalent. The engineering aspects of ice, primarily ice control structures, and ice forecasting have also received significant attention. Brief summaries of the articles are provided. The intention of this review is to provide an overview and a reference source of research conducted on Great Lakes ice.

BOLSENGA, S.J., C.E. Herdendorf, and D.C. NORTON. Spectral transmittance of lake ice from 400-850 nm. Hydrobiologia 218:15-25 (1991).

Spectral transmittance signatures for a variety of freshwater ice types were collected in the 400-850 nm range. Clear ice showed the highest transmittances, snow-covered ice the lowest and other ice types intermediate transmittances. All of the ice spectral transmittance curves showed the same general shape with no mutually-exclusive characteristics exhibited by any ice type. The magnitude of the transmittance values was the primary distinguishing factor. The range of transmittance values directly under the ice was remarkably narrow (excluding snow-covered ice) and markedly different from values lower in the water column.

BOLSENGA, S.J., and D.C. NORTON. Maximum snowfall at long-term stations in U.S./Canadian Great Lakes. Natural Hazards 5:221-232 (1992).

Heavy snowfalls can pose natural hazards in the North American Great Lakes region. Maximum annual snowfalls are presented from an extensive data base at 82 long-period-of-record stations. In the absence of site-specific information, these data should be useful to designers, planners, and resource managers in the region. A relationship exists between maximum snowfalls and latitude because the northern Great Lakes climate is cooler and drier than the climate of the southern Great Lakes. A relationship between longitude and maximum snowfalls appears to be based on the longitudinal variation of precipitable water vapor aloft. No apparent relationship exists between maximum snowfall and elevation when station data are analyzed without regard to data from lake-effect zones. However, when one lake-effect region was analyzed in detail, an orographic effect was clearly evident in both maximum and average annual snowfalls.

BOLSENGA, S.J., and H.A. VANDERPLOEG. Estimating photosynthetically available radiation into open and ice-covered freshwater lakes from surface characteristics; a high transmittance case study. Hydrobiologia 243/244:95-104 (1992).

A simple technique, based on several published studies, is presented to estimate photosynthetically available radiation (PAR: 400-700 nm) at the air/water and ice/water interfaces on freshwater lakes. Grand Traverse Bay of Lake Michigan of the Laurentian Great Lakes before, during, and after ice cover is used as a case study. The technique depends on assigning PAR transmittances to air/water or air/ice surfaces from empirically determined relationships. During ice cover, PAR reaching the water column under the ice exceeded 45% of incoming PAR, on the average, due to the amount of clear ice present on the bay.

BRATKOVICH, A.W., and S.P. Dinnel. Lower Mississippi River historical nitrate flux and Mississippi River outflow buoyancy flux. Proceedings, Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, TAMU-SG-92-109, New Orleans, LA, October 1-4, 1991. NOAA Coastal Ocean Program Office, 37-42 (1992).

Results from an analysis of 35-year time sequences of Lower Mississippi River water discharge, nitrate concentration and nitrate flux are discussed. The potential predictability of these quantities is evaluated. Results indicate a large amplitude, very-low-frequency cycle in the nitrate concentration that is not observed in the water discharge. A decrease in average nitrate concentration from a peak in 1983 to the present confirms that this variability is more cyclic than trend-like. River-water discharge variation is greatest in association with the annual cycle. The annual water discharge and nitrate concentration cycles are similar, high nitrate concentrations usually occur near the spring fresher and low concentrations usually occur along with autumn low flow conditions. Nitrate flux variations exhibit a low amplitude, very-low-frequency modultation of a dominant, annual cycle. A predictor-hindcastor analysis indicates that truly skilled forecasts of all three fields are feasible. Shelf stratification and nutrient field conditions respond to forcing by riverine source functions. Hydrographic data in the Mississippi River outflow region from two NECOP cruises are presented. Spatial distributions of Cruise 1 (summer 1990) and Cruise 2 (winter 1991) hydrographic data are compared seasonally and with historical data. Shelf stratification conditions are examined based on NECOP cruise data, and these conditions are discussed in the context of riverine and other forcing functions.

Burrows, W.R., and R.A. ASSEL. Use of CART for diagnostic and prediction problems in the atmospheric sciences. Proceedings, 12th Conference on Probability and Statistics in the Atmospheric Sciences, Toronto, Ontario, Canada, June 22-26, 1992. American Meteorological Society, Boston, MA, 161-166 (1992).

No abstract.

CLITES, A.H., T.D. FONTAINE, and J.R. WELLS. Distributed costs of environmental contamination. Journal of Ecological Economics 3:215-229 (1991).

Improper disposal of toxic contaminants costs society far more than just cleanup costs. Agency expenses, costs of research and litigation, and resource damages represent additional costs of pollution. These costs are generally borne by the public rather than by the polluter, and are therefore termed 'distributed'. Two cases of PCB contamination in aquatic systems were analyzed from a distributed-costs perspective: New Bedford Harbor, MA, and the Hudson River, NY. For the cases analyzed, the major distributed cost was the loss of past and future fishery revenues. For the cases analyzed, distributed costs made up from about 40% to 99% of total costs.

COTNER, J.B., Jr., and R.G. Wetzel. Uptake of dissolved inorganic and organic phosphorus compounds by phytoplankton and bacterioplankton. Limnology and Oceanography 37(2):232-243 (1992).

Potential sources of dissolved P to phytoplankton and bacterioplankton were examined in a small meso-eutrophic lake. Kinetic analyses of whole lake water on three dates demonstrated that the maximal rate (Vmax) for phosphate uptake was highest (5.2 nM min-1) in spring. On all dates, size fractionation of plankton and kinetic analyses of uptake indicated that most (>50%) uptake of phosphate was by phytoplankton at Vmax and by bacteria at ambient concentrations. Isotope dilution assays, with either unlabeled phosphate or various dissolved organic P (DOP) compounds, demonstrated that phosphate was the preferred substrate for uptake into both algae and bacteria. Phytoplankton had greater capacity for uptake of P from both phosphate and DOP than bacterioplankton. We concluded that phytoplankton use both phosphate and DOP, particularly at high substrate concentrations, and that bacterial utilization of P may be limited by the availability of organic C or other nutrients.

CROLEY, T.E.II. Long-term heat storage in the Great Lakes. Water Resources Research 28(1):69-81 (1992).

Practical estimation of long-term daily Great Lakes evaporation requires one-dimensional (depth) models of heat storage and mixing. Conceptual models are preferable to physical models for small-computer simulations that are multiple, continuous, and long. This paper describes a new conceptual superposition model of heat storage to extend an existing evaporation model along the lake depth. The resulting daily model is recalibrated to remotely sensed surface water temperatures and is used to illustrate anew seasonal heating and cooling cycles, heat-temperature hysteresis, water column turnovers, and mixed-layer developments. It is used as well to compare the vertical distribution of temperatures with independent bathythermograph data. The time occurrence structure of evaporation on the Great Lakes is investigated, and the effects of summertime initial conditions on subsequent wintertime behavior of evaporation are simulated. Impacts of perceived large-lake thermodynamic behavior are analyzed, and suggestions are made for further research.

Dickey, T., J. Marra, T. Granata, C. Langdon, M. Hamilton, J. Wiggert, D. Siegel, and A.W. BRATKOVICH. Concurrent high resolution bio-optical and physical time series observations in the Sargasso Sea during the Spring of 1987. Journal of Geophysical Research 96(C5):8643-8663 (1991).

The evolution of bio-optical and physical properties of the upper layer of the open ocean has been examined at time scales from a few minutes to several months using recently developed multi-variable moored systems (MVMS). Concurrent, collocated time series measurements of horizontal currents, temperature, photosynthetically available radiation, transmission of a beam of collimated light (660 nm), stimulated chlorophyll fluorescence, and dissolved oxygen concentration were made. The systems were located at eight depths in the upper 160 m of the Sargasso Sea (34oN, 70oW) and were deployed three times for a total of 9 months in 1987. The first deployment data presented here show considerably more variability than those of the latter two deployments because of the dynamic springtime shoaling of the mixed layer and the accompanying phytoplankton bloom and more mesoscale variability associated with cold core rings and warm outbreak waters associated with the Gulf Stream. These data are used to demonstrate the utility of the MVMS and indicate the importance of high-frequency, long-term sampling of bio-optical and physical variables of the upper ocean for understanding and modeling dynamical changes in bio-optical properties, primary production, and carbon fluxes of the upper ocean on time scales ranging from minutes to seasons to decades. Some phenomena observed with the systems include (1) diurnal variations in bio-optical properties, (2) springtime stratification and rapid (-2 days and less) episodic changes in the beam attenuation coefficient and in situ chlorophyll fluorescence, and (3) advective episodes associated with warm outbreaks of Gulf Stream waters and cold core Gulf Stream rings in the vicinity of the mooring.

EADIE, B.J., G.L. BELL, and N. HAWLEY. Sediment trap study in the Green Bay mass balance program: Mass and organic carbon fluxes, resuspension, and particle settling velocities. NOAA Technical Memorandum ERL GLERL-75, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (PB92-125293/XAB) 29 pp. (1991).

This research is a part of a large, multidisciplinary program designed to measure and model the mass balance of congener-specific polychlorinated biphenyls (PCB) and dieldrin in Green Bay, western Lake Michigan. In this report, we document the results of our sediment trap study designed to collect representative samples of settling particulate material from five sites within the southern portion of the bay. Measuring the mass collected allowed us to calculate the gross downward flux of particulate matter and particle settling velocities. The mass balance models being applied to Green Bay explicitly require these particle setting velocities and vertical fluxes of mass and particulate organic carbon. Mass and carbon fluxes from sediment traps located 2 m above bottom and distributed throughout southern Green Bay showed that seasonal flux patterns were generally high prior to stratification, declined to minimum values during summer, and then generally reached much higher fluxes during fall overturn. In the epilimnion, seasonal patterns are similar to the near bottom samples although mass flux is approximately 10% of the near bottom flux, and carbon flux is approximately 20%. Settling velocities for epilimnetic samples are approximately 0.5 m/day, similar to open-lake values. Significantly higher settling velocities (4-6 m/day) during the stratified period were calculated for the 2 m above bottom region. These rates imply that a large recharging of the particle pool by either horizontal transport or local sediment resuspension occurs throughout the year. During the unstratified period, settling velocities throughout the water column are approximately 12-18 m/day, more than an order of magnitude higher than during stratification. At this rate, the particle residence time in the water column is only a few days, again implying frequent recharging. Sediment resuspension estimated by a steady state model required to support trap observations is about 10 g/m2/day with scale thicknesses of 5-7 m, and there is little seasonal variation until late September.

EADIE, B.J., N.R. MOREHEAD, J. Val Klump, and P.F. LANDRUM. Distribution of hydrophobic organic compounds between dissolved and particulate organic matter in Green Bay waters. Journal of Great Lakes Research 18(1):91-97 (1992).

Water samples freshly collected from southern Green Bay were inoculated with radiolabelled hydrophobic organic compounds (HOC) and, after equilibration, separated into particle bound, dissolved organic matter (DOM) bound and freely dissolved phases. Ambient suspended matter (2.7-28 ppm) and dissolved organic carbon (5.2-11.5 ppm) were high in concentration relative to the open Great Lakes, but HOC distribution coefficients were not significantly different between Green Bay and previously measured open Great Lakes values. HOC in the particle phase ranged from 3% for 4-MCB to 53% for BaP and DDT. HOC associated with DOM was generally higher than for open lake samples, and ranged from 2% for 2,2',5,5'--TCB to 26.5% for 4-MCB.

EADIE, B.J., J.A. ROBBINS, P. Blackwelder, S. Metz, J.H. Trefry, B. McKee, and T.A. Nelson. A retrospective analysis of nutrient enhanced coastal ocean productivity in sediments from the Louisiana continental shelf. Proceedings, Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, New Orleans, LA, October 1-4, 1991. NOAA Coastal Program Office, 7-14 (1992).

Sediments have been collected and analyzed to obtain evidence in support of the argument that anthropogenic nutrient loading has led to changes in coastal water quality and increased productivity. Cores representing approximately 100 years of input show unmistakable signs of increased accumulation of organic carbon beginning early in the 1900s. Organic tracers show that virtually all of this increase appears to be of marine origin. At two sites within the plume/hypoxia region, preliminary estimates are that 50 to 70 percent more organic carbon is presently accumulating than at the turn of the century. These preliminary interpretations provide strong support for the central themes of the NECOP program. Analysis and interpretation of further supporting information is continuing.

FAHNENSTIEL, G.L., and H.J. CARRICK. Phototrophic picoplankton in Lakes Huron and Michigan: abundance, distribution, composition, contribution to biomass and production. Canadian Journal of Fisheries and Aquatic Sciences 49(2):379-388 (1992).

The phototrophic picoplankton communities of Lakes Huron and Michigan were studied from 1986 through 1988. Abundances in the surface-mixed layer ranged from 10 000 to 220 000 cellsmL-1 with a seasonal maximum during the period of thermal stratification. During thermal stratification, maximum abundances were generally found within the metalimnion/hypolimnion at depths corresponding to the 0.6-6.0% isolumes. The picoplankton community was dominated by single phycoerythrin-containing (PE) Synechococcus (59%) with lesser amounts of chlorophyll fluorescing cells (21%), PE colonial Synechococcus-like cells (11%) other PE colonion Chroococcales (6%), and other cells (3%). Single PE Synechococcus was abundant throughout the year whereas chlorophyll-fluorescing and colonial cyanobacteria were more abundant during the periods of spring isothermal mixing and summer stratification, respectively. Picoplankton accounted for an average of 10% (range 0.5-50%) of phototrophic biomass. Phototrophic organisms that passed 1-, 3-, and 10-mm screens were responsible for an average of 17% (range 6-43%), 40% (21-65%), and 70% (52-90%) of primary production. Maximum contributions of <1, <3, and <10 mm size fractions occurred during the period of thermal stratification. Primary production by phototrophic picoplankton was found to equal production in the <1 mm size fraction.

FAHNENSTIEL, G.L., M.H. MARCOVITZ, and M.J. McCORMICK. High growth and microzooplankton-grazing loss rates for phytoplankton populations from the Mississippi River plume region. Proceedings, Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, New Orleans, LA, October 1-4, 1991. NOAA Coastal Ocean Program Office, NECOP Synthesis TAMU-SG-92-109, 111-116 (1992).

During the July/August 1990 NECOP cruise, taxon-specific growth, and microzooplankton grazing and sedimentation loss rates were measured on dominant phytoplankton populations in the plume/hypoxia region. Taxon-specific growth rates (m) ranged from <0.1 to >3.0 d-1 with highest rates (>2 d-1) in the plume region. Many surface growth rates in the plume were close to or exceeded previously published umax values. For most taxa, including diatoms and non-diatoms, growth rates decreased in the hypoxia region. Significant microzooplankton grazing loss rates were noted only for small phytoplankton (<15 mm); rates for these taxa were high (>1.0 d-1) in the plume region and decreased in the hypoxia region. Sedimentation was an important loss only for a few diatoms. Our data suggest that during the summer in the plume region, phytoplankton production rates are high, and most of this production is recycled within the surface layer.

FONTAINE, T.D., III, and D.J. Stewart. Exploring the effects of multiple management objectives and exotic species on Great Lakes food webs and contaminant dynamics. Environmental Management 16(2):225-229 (1992).

A simulation model was developed to describe linkages among fish web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter (Bythotrephes) on Lake Michigan food web and contaminants dynamics. The model predicts that contaminant concentrations in salmonines will decrease by nearly 20% if Bythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies of dominant organisms) that should be corrected in order to make reliable management decisions.

GOTTLIEB, E.S. Variability of the stratified flow in the passages connecting Green Bay and Lake Michigan. Ph.D. dissertation, University of Michigan, Ann Arbor, MI, 93 pp. (1992).

Green Bay is a large shallow embayment connected to Lake Michigan. Discharges of inadequately treated industrial and municipal wastes have adversely affected water quality in the bay's shallow southern end. Flushing of the bay is primarily influenced by water volume exchange flows between the bay and Lake Michigan occurring through the four main passages comprising the bay mouth, which is located at the bay's northeastern end. In order to help identify the important exchange processes and dynamics, estimate the magnitude of the exchange, and describe the exchange variability, the passages were instrumented in 1977-1987 and again in 1988-1989. The collected current velocity and water temperature data are compiled, presented, analyzed, and used in conjunction with thermistor chain, meteorological, and water surface level data to describe the volume exchange dynamics, magnitude, and variability. Energetic fluctuations in the currents and temperatures occur at semidiurnal and longer periods. While winter currents are almost entirely barotropic (uniform with depth) and of moderate strength, summer currents are affected by the thermal stratification, becoming baroclinic (sheared) and even bi-directional (two-layered) at times. Below the thermocline (in the lower-layer), pressure-driven inflow of cool and dense water from Lake Michigan into Green Bay is observed to intensify during periods when the thermocline is tilted across the bay mouth. The directions of the inflowing currents and the thermocline tilt are consistent with rotation effects, as confirmed by a simple scale analysis. A conceptual model is used to describe the relationship between the thermocline tilt and the lower-layer flow through Rock Island Passage. Also, in Deaths Door Passage, a large-amplitude semidiurnal internal waveform is observed to persist throughout the stratified season. It is shown that despite the large variability exhibited by the bay/lake exchange flows, a volume of Lake Michigan water at least equal to the volume of Green Bay enters the bay once during each stratified season.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Publications by the Staff of the Great Lakes Environmental Research Laboratory. C.M. Darnell (ed.). Great Lakes Environmental Research Laboratory, Ann Arbor, MI, (1992).

No abstract.

GREAT LAKES ENVIRONMENTAL RESEARCH LABORATORY. Annual Report for the Great Lakes Environmental Research Laboratory, FY 1991. Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 54 pp. (1992).

No abstract.

HAWLEY, N. Preliminary observations of sediment erosion from a bottom resting flume. Journal of Great Lakes Research 17(3):361-367 (1991).

A small portable flume was designed and constructed to measure in situ erosion velocities. Preliminary results from deployments in lake Michigan, Lake Superior, and Lake Ontario show that the flume can produce and measure the velocities required to erode fine-grained material from the lake bottom. Shear stresses required for erosion (calculated from the measured velocities) varied from 0.03 to 1.34 dynes/cm2. As the flow velocity increases, erosion appears to occur as discrete episodes rather than continuously. Before flume results can be sued to predict a sediment's resistance to erosion, both extensive measurements of sediment properties and comparisons of flume results to naturally-occurring erosion events are needed.

HERCHE, L.R., and H.C. HARTMANN. Estimation of Great Lakes water level statistics: Conditioning via "The Bootstrap". Journal of Great Lakes Research 18(1):218-228 (1992).

Reliable lake level frequency distributions are a critical component of any comprehensive strategy for coping with Great Lakes water level fluctuations. However, statistical techniques commonly used on riverine systems are inappropriate for large lake systems, due to the level's long-term persistence and dependence on the prevailing climatic regime. To illustrate an alternative methodology, we present a series of resampling analyses modeled after well-known bootstrap techniques applied to 130 years of monthly Lake Erie water level records. The analyses show that lake level exceedance probabilities should be conditioned on 1) length of planning horizon, 2) starting month of planning horizon, 3) initial lake level, and 4) climatic regime. Our methodology can be extended to additionally consider storm and wind effects on levels, to incorporate levels data available for discontinuous periods prior to 1860, and to develop other types of lake level statistics useful to decision makers, such as duration and time-to-exceedance probabilities.

JOHENGEN, T.H., A.M. BEETON, and R.E. Holland. A final water quality monitoring report and evaluation of the Saline Valley rural clean water project. Contract Report, Michigan Department of Agriculture, Washtenaw County Board of Commissioners, Monroe County Board of Commissioners, Washtenaw County Soil Conservation District, and the Monroe County Soil and Water Conservation District, 136 pp. (1991).

No abstract.

JOHENGEN, T.H., and A.M. BEETON. The effects of temporal and spatial variability on monitoring agricultural nonpoint source pollution. EPA/625/R-92/006. EPA Seminar Publication. The National Rural Clean Water Program Symposium, 89-95 pp. (1992).

The Saline Valley Rural Clean Water Program project was one of 21 projects developed to evaluate methods of controlling agricultural nonpoint source pollution. Control programs were designed around voluntary implementation of best management practices, and water quality trends were monitored at eight stream stations from July 1981 to December 1989, using a fixed, weekly sampling design. An additional monitoring program was established within the Macon Creek subbasin (Station 9) in June 1988 to quantify temporal and spatial variability in pollutant loads. Macon Creek was monitored daily for seven days following any storm of more than half an inch of rain. Five stations were added upstream from existing Station 9 to examine spatial variation in loading rates throughout the subbasin. This study describes these storm monitoring results and discusses their implication to the Saline project's monitoring data.

LANDRUM, P.F., B.J. EADIE, and W.R. FAUST. Variation in the bioavailability of polycyclic aromatic hydrocarbons to the amphipod Diporeia (spp.) with sediment aging. Environmental Toxicology and Chemistry 11:1197-1208 (1992).

The accumulation kinetics of the amphipod Diporeia sp. for sediment-sorbed polycyclic aromatic hydrocarbon (PAH) congeners were measured where the contact time between the PAH congeners and the sediments varied between 3 and 150 d. Diporeia were exposed to a reference sediment dosed with two radiolabeled PAHs (phenanthrene and pyrene) and to sediments dosed with the two radiotracers and a mixture of PAHs at 272.3 ± 10.9 nmol g-1 dry sediment, as the sum of the nine nonlabeled PAHs. The sediments were prepared by dosing aliquots of a single collection of sediment with PAHs at different times, producing a series of contact times. The exposures were all performed at the same time from a single collection of organisms. Diporeia were sampled for mortality and toxicokinetics for up to 28 d. Some sediment avoidance was observed during the first 12 d of exposure. The partitioning between sediment particles and interstitial water increased significantly for both phenanthrene and pyrene as contact time increased. The uptake rate coefficient decreased for both phenanthrene and pyrene when the contact with the sediment was increased from 3 to 60 d. When the contaminant-sediment contact was increased from 60 to 150 d, the phenanthrene uptake rate coefficient remained constant whereas that for pyrene increased somewhat. Similar uptake results were observed with the nonradiolabeled compounds.

LANDRUM, P.F., and W.R. FAUST. Effect of variation in sediment composition on the uptake rate coefficient for selected PCB and PAH congeners by the amphipod, Diporeia sp. In Aquatic Toxicology and Risk Assessment: Fourteenth Volume, ASTM STP 1124, M.A. Mayes and M.G. Barron, (eds ). American Society for Testing and Materials, Philadelphia, PA, 263-279 (1991).

The exposure of benthic organisms to sediment-associated toxic organics is influenced by the sediment's organic carbon (OC) content because hydrophobic organic contaminants sorb to the organic and fine grain portions of sediments, and benthos ingest the OC associated with fine material. The effect of varying sediment composition, measured as the percent of combustible solids (CS), percent of OC, and percent of fine-grained material (FM) (the <63 mm fraction of the sediment), was examined by determining the accumulation of sediment-associated polychlorinated biphenyl and polycyclic aromatic hydrocarbon congeners by the Great Lakes amphipod, Diporeia sp. Prepared sediments (3 and 5% CS) and native sediment were dosed with pairs of contaminants: 3H-pyrene and 14C- 2,5,2',5'-tetrachlorobiphenyl, and 3H-benzo(a)pyrene and 14C- 2,4,5,2',4',5'-hexachlorobiphenyl. Additionally, some of the dosed 5% CS sediment was recombined with the coarse material to recreate a 2% CS sediment where the fine material had been dosed preferentially. The accumulation of the radiolabeled compounds was followed for 27 days, and the partitioning between sediment particles and interstitial water was measured at the end of the experiment. When uptake rate coefficients (Ks) and the depuration rate constants (Kd) were estimated, the Kd values were found to be similar to those previously measured in Diporeia. The Ks values from the native and fine labeled sediments (both approximately 2% CS) were similar. Ks values declined with increasing CS, OC, and FM. Correlations indicated that the percent of OC best accounted for the variation resulting from changes in the sediment composition for each compound, both for Ks and for sediment-interstitial water partitioning. As in previous studies, the partition coefficient between sediment and interstitial water did not account for the changes in the bioavailability between different classes of compounds. Higher partitioning and higher uptake rate coefficients were found for the chlorinated hydrocarbons than for the polycyclic aromatic hydrocarbons, even when the hydrophobicity of the contaminants was accounted for. A linear solvation energy quantitative structure activity model was useful for describing the differences in the uptake rate coefficients by accounting for the differences in the molecular characteristics of the two compound classes.

LANDRUM, P.F., W.A. Frez, and M.S. Simmons. Relationship of toxicokinetic parameters to respiration rates in Mysis relicta. Journal of Great Lakes Research 18(2):331-339 (1992).

The uptake of organic xenobiotics from water was compared to the respiration rate of the Great Lakes invertebrate, Mysis relicta. Xenobiotic clearance was compared with oxygen clearance. Uptake clearance is defined as milliliters of water stripped of contaminant or oxygen per mass of organism per hour. M. relicta were exposed to benzo(a)pyrene (BaP) and 2,2'4,4'5,5'-hexachlorobiphenyl (HCBP). The respiration rate for M. relicta declined logarithmically when measured for periods ranging from 3 to 48 h. The respiration rate ranged from 1.4 (1.24-1.48) mg O2 mg-1 wet weight h-1 for a 3 h period to 0.25 ± 0.023 mg O2 x mg-1 wet weightlh-1 for a 48 h period. Neither the presence of the methanol carrier nor the methanol carrier plus xenobiotics produced significant changes in respiration compared to those of the control organisms in lake water only. The clearances of oxygen and the two xenobiotics were each inversely correlated to organism weight. The slopes of the clearance regressions with organisms weight were not significantly different among the different measures of xenobiotic or oxygen clearance. There was a near constant ratio of xenobiotic clearance to oxygen clearance of 1.26 ± 0.02 (mean ± SE, n=29) for BaP and 1.37 ± 0.12 (r=29) for HCBP. These findings suggest that the accumulation of organic xenobiotics may be linked to the accumulation of oxygen for M. relicta.

LANDRUM, P.F., W.A. Frez, and M.S. Simmons. The effect of food consumption on the toxicokinetics of benzo(a)pyrene and 2,2',4,4',5,5'-hexachlorobiphenyl in Mysis relicta. Chemosphere 25(3):397-415 (1992).

The relative importance of water and ingested food as possible avenues of contaminant accumulation was examined. Mysis relicta was exposed to two representative non-polar contaminants: benzy(a)pyrene (BaP) and 2,2',4,4',5,5'-hexachlorobiphenyl (HCB). The accumulation was examined kinetically in the presence and absence of two food types, Daphnia pulex (water flea) and Tabellaria flocculosa (a diatom) The availability of either food enhanced HCB accumulation and reduced BaP accumulation. Feeding did not affect HCB elimination but enhanced BaP elimination. The BaP was eliminated primarily as metabolites. Essentially all of the elimination occurred via the fecal route for both compounds. The fraction of the accumulation via ingestion of contaminated food was greater when mysids fed on Daphnia than Tabellaria and was greater for HCB than BaP.

LEE, D.H. Introduction to the special section on improving Great Lakes water levels statistics. Journal of Great Lakes Research 18(1):199-201 (1992).

The water levels of the Great Lakes achieved record high levels in 1985 and 1986 followed by a significant decline in 1987 and 1988. Neither the rise nor decrease in levels were forecasted, leading to public demand for improved water level information to be used for planning and water resource management. The development of improved water level statistics must address the user's needs and should consider the physical aspect of the water fluctuations being modeled (annual fluctuations, seasonal fluctuations, storm rises, etc.), matching the type of statistic to the type of risk evaluation and the planning horizon. In order to develop new water level statistics, the experts must reach a consensus on the statistical model, incorporate conditionality, and properly adjust recorded data to reflect the existing hydraulic and hydrologic regimes. The effective use of the new statistics will depend upon the development of decision-making techniques for each interest and their communication to the user in non-technical terms.

Lindner, G., I. Greiner, R. Grom, K. Hain, M. Ibler, S. Kaminski, J. Kleiner, W. Pfeiffer, J.A. ROBBINS, O. Seewald, Ch Wilhelm, and M. Wunderer. Removal and accumulation processes of cesium radionuclides in prealpine lakes. Proceedings, Radiation Protection for People and the Environment, Aachen, Germany, September 30-October 3, 1991. (1991).

In prealpine lakes in southwest Germany, differences in the behavior of Cesium radionuclides from the Chernobyl fallout were observed, which are related to their limnological character. In Lake Constance, Cesium radionuclides introduced into the epilimnion were transferred to the sediment to a large extent already in May 1986 due to calcite precipitation and there dominantly deposited in an irreversible state. Therefore, the contamination of water and fish decreased rapidly and redissolution from sediment remains very small. In Vorsee and Schreckensee, on the other hand, a persistent input of Cesium radionuclides occurs from their swampy watersheds and from sediments due to redissolution, which is particularly high at low temperatures. Consequently, the decrease in the contamination of fish is considerably slower than in Lake Constance.

LIU, P.C. Chaotic dynamics and ocean wave statistics. Proceedings, Sixth IAHR International Symposium on Stochastic Hydraulics, Taipei, Taiwan, May 18-20, 1992. 345-352 (1992).

Recent developments in chaotic dynamics have indicated that qualitative information of a dynamical system can be extracted from the observation of a single time series as the time series bears the marks of all other variables relevant in the underlying dynamics. In this paper we review and explore the application of this approach in connection with the study of ocean wave statistics.

LIU, P.C. Extracting dynamics from ocean wave time series data. In Mechanics Computing in 1990's and Beyond, Volume 1, H. Adeli and R.L. Sierakowski (eds.). American Society of Engineers, New York, 348-353 (1992).

Recent developments in chaotic dynamics have indicated that qualitative information of a dynamical system can be extracted from the observation of a single time series as the time series bears the marks of all other variables relevant in the underlying dynamics. In this paper, we review this approach and explore its possible applications to ocean wave dynamics.

Lohrenz, S.E., D.G. Redalje, G.L. FAHNENSTIEL, and G.A. LANG. Regulation and distribution of primary production in the northern Gulf of Mexico. Proceedings, Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, New Orleans, LA, October, 1-4, 1991. NOAA, Coastal Ocean Program Office, 95-104 (1992).

As part of the NOAA Nutrient Enhanced Coastal Ocean Productivity program, we are examining the degree to which elevated levels of nutrients in coastal Gulf of Mexico waters associated with the Mississippi River affect phytoplankton production, growth, and photosynthesis-irradiance (P-I) properties. Here, we present results obtained from three cruises including September 1989 and April and July-August 1990 in which we examined (i) the relationships between phytoplankton community physiology, photosynthetic properties, and environmental conditions, and (ii) the temporal and spatial patterns of primary production in the northern Gulf of Mexico. Horizontal variations in photosynthetic properties (PBmaxa) were relatively small, despite large differences in phytoplankton community growth rates between the nutrient rich plume waters and low nutrient shelf waters. We concluded that variations in photosynthetic properties were constrained by compensatory changes in carbon-to-chlorophyll ratios. Estimates of integral production from a photosynthetic-irradiance model agreed well with in situ and simulated in situ incubations. Areal integral production in the vicinity of the river outflow region was apparently coupled to riverine nutrient fluxes.

McCORMICK, M.J., R.L. Pickett, and G.S. MILLER. A field evaluation of new satellite-tracked buoys: A LORAN-C position recording and a sonobuoy type drifter. MTS Journal 25(2):29-33 (1991).

Two types of satellite-tracked, drifting data buoys were tested in Lake Michigan for twenty days. One type was a sonobuoy-size (0.9 m long, 12 cm diameter) buoy made by Metocean Data Systems and one was a mid-sized (1.8 m long, 20 cm diameter) buoy made by Polar Research Laboratory. The two Metocean buoys came equipped with sensors for barometric pressure, air temperature, and seven levels of water temperature from the surface down to 100 m. The Polar Research buoy was without sensors and was modified to carry a LORAN-C position-recording system. The Metocean buoy sensors compared well with those of the National Oceanic and Atmospheric Administration (NOAA) meteorological buoy in the center of Lake Michigan and with the Conductivity, Temperature, Depth (CTD) data taken at the launch site. Shortly after launch, however, the bottom weight broke off one of the subsurface temperature cables on these buoys. This failure allowed the temperature cable to stream along near the surface so that no buoy, however, provided useful subsurface data for fifteen days until its ballast weight was lost after contact with bottom. The add-on LORAN positioning on the Polar Research buoy provided more frequent and precise positions than were available from satellite tracking alone. The LORAN-C data suggest that infrequent yet large satellite positioning errors may occur and may be difficult for the user to detect.

Merritt, R.W., D.A. Craig, E.D. Walker, H.A. VANDERPLOEG, and R.S. Wotton. Interfacial feeding behavior and particle flow patterns of Anopheles quandrimaculatus larvae (Dipteria: Culicidae). Journal of Insect Behavior 5(6):741-761 (1992).

The interfacial feeding behavior, mouthpart movements, and particle flow patterns of Anopheles quadrimaculatus larvae were investigated, using videotape recordings, high-speed microcinematography, SEM, and laboratory experiments. While positioned at the water surface, larvae demonstrated 12 behaviors associated with movements of the head.  In one of these, a larva rotated its head 180o and directed its mouthparts against the air-water interface. The larva rapidly extended and retracted its lateral palatal brushes (LPBs) at a rate of 5 cycles/s (5 Hz), creating currents and allowing for the collection of particles.  Particles moved toward the head at a velocity of 4.31 mm/s, in discrete stops and starts, as the LPBs beat. Our analyses determined that particle movement toward the mouth was governed by the very low Reynolds numbers (0.002-0.009). This finding indicated that viscous forces predominated in Anopheles feeding and no inertial movement of particles occurred. According to this model, the LPBs cannot intercept particles directly, but function as paddles for particle entrainment.  We did not observe the pharynx to function in particle filtration but, rather, in food bolus formation. We propose that the maxillary pilose area and midpalatal brush function as interception structures.  It appeared that the LPBs do not break the surface film to feed, but collect particles from the surface microlayers. A plume of uningested particles emerged from the sides of the cibarium and descended into the water column.  The plume consisted of alternately clear and dark, lenticular laminae formed beneath the larval head during the collecting-filtering feeding mode. A comparison of particle sizes from surface microlayers and gut contents of fourth instars showed that larvae ingested mainly small particles in the range of 1.5 to 4.5 um in diameter. The potential significance of interfacial feeding by anopheline larvae in their aquatic environment is discussed.

NALEPA, T.F., W.S. GARDNER, and J.M. MALCZYK. Phosphorus cycling by mussels (Unionidae:Bivalvia) in Lake St. Clair. Hydrobiologia 219:239-250 (1991).

The role of mussels in cycling phosphorus in Lake St. Clair during the May-October period was examined by measuring concentrations in the water column and in mussel tissue, and by measuring rates of biodeposition and excretion. Mean rates of biodeposition and excretion for Lampsilis radiata siliquoidea, the most abundant species, were 6.3 mg P (g shell-free dry wt)-1 h-1 and 1.3 mg P (g shell-free dry wt)-1 h-1, respectively; body tissue phosphorus content was 2.7 percent of dry wt. Seasonal changes in excretion rates appeared to be related to the gametogenic cycle of the organism, but seasonal changes in biodeposition rates were not apparent. Phosphorus assimilation efficiency for this species was about 40 percent. Overall, the mussel population in Lake St. Clair filtered about 210 MT of phosphorus, or about 13.5 percent of the total phosphorus load for the May-October study period. Of this amount, about 134 MT was sedimented to the bottom via biodeposition. Mussel biodeposition may be an important source of nutrients to other biotic components in the lake such as macrophytes and invertebrate deposit-feeders.

Parrish, C.C., B.J. EADIE, W.S. GARDNER, and J.F. CAVALETTO. Lipid class and alkane distribution in settling particles of the upper Laurentian Great Lakes. Organic Geochemistry 18(1):33-40 (1992).

Sediment traps were deployed at up to 6 depths at seven stations in Lakes Superior, Michigan, and Huron for 2 months during the summer of 1984. Total organic carbon, total lipid, lipid classes, and alkanes were measured in the collected material to gain information on composition, sources, and fate of particulate organic matter in the Great Lakes. Total aliphatic hydrocarbon was a large component of all samples, accounting for more than 15% of the extractable lipids. Particles collected at 10-m depth in Lake Huron had especially high relative contributions (more than 65% of total lipids) of total aliphatic hydrocarbons at the three stations examined. The high proportion of aliphatic hydrocarbon appears not to have originated from customary pollution sources. The alkane distribution was strongly dominated by even-numbered carbon chains of unknown origin. Algae are a possible source for the unsaturated hydrocarbons that were present at relatively elevated levels in settling particles. Botryococcus braunii, sampled from Lake Michigan had as much as 80% of its lipids in the form of hydrocarbons. Wax and sterol esters constituted less than 10% of the lipids in trap material except in samples from mid-depths in Lake Huron where high levels of these compounds may have resulted from elevated amounts of calanoid copepod debris or swimmers entering the traps.

Privalsky, V. Statistical analysis and predictability of Lake Erie water level variations. Journal of Great Lakes Research 18(1):236-243 (1992).

Statistical predictability and spectra of mean monthly and annual water levels (MMWL and MAWL) of Lake Erie at Cleveland, Ohio, 1860-1988, are studied within the framework of the Kolmogorov-Wiener theory of extrapolation using AR modeling and the theory of non-stationary product random processes in order to assess the attainable quality of least-squares predictions of water levels. MMWL are shown to possess relatively high predictability due to a strong seasonal cycle in water level variations, with predictability limits extending up to 12 months. MAWL reveal a time-dependent structure in the mean value, variance, and spectrum which can be ascribed, among other reasons, to a climatic change. Their predictability is quite low (predictability limit not more than 1 or 2 years) and cannot be improved by applying other techniques of scalar time series extrapolation. The uncertainties in water level predictions should be taken into account quantitatively when making decisions which depend upon hydrological parameters.

Privalsky, V., and T.E. CROLEY. Statistical validation of GCM-simulated climates for U.S. Great Lakes and the C.I.S. Emba and Ural River basins. Stochastic Hydrology Hydraulics 6:69-80 (1992).

Many researchers use outputs from large-scale global circulation models of the atmosphere to assess hydrological and other impacts associated with climate change. However, these models cannot capture all climate variations since the physical processes are imperfectly understood and are poorly represented at smaller regional scales. This paper statistically compares model outputs from the global circulation model of the Geophysical Fluid Dynamics Laboratory to historical data for the Unites States Laurentian Great Lakes and for the Emba and Ural River basins in the Commonwealth of Independent States (C.I.S.). We use maximum entropy spectral analysis to compare model and data time series, allowing us to both assess statistical predictabilities and to describe the time series in both time and frequency domains. This comparison initiates assessments of the model's representation of the real world and suggests areas of model improvement.

QUIGLEY, M.A., and H.A. VANDERPLOEG. Ingestion of live filamentous diatoms by the Great Lakes amphipod, Diporeia sp.: A case study of the limited value of gut contents analysis. Hydrobiologia 223:141-148 (1991).

Individuals of the Great Lakes amphipod, Diporeia sp. (formerly named Pontoporeia hoyi) were collected from a 45-m deep station in southeastern Lake Michigan and isolated in small laboratory feeding vessels at 4 oC, after the animals had voided their guts over a 24-hour period. Over a 20-day period, following introduction of a single ration of live cells of the filamentous diatom,Melosira varians, 9 of 10 animals had ingested this material, and 7 of these 9 individuals had deposited fecal pellets. Subsequent examination of gut contents and fecal pellets showed that although animals had ingested whole algal cells/filaments, little of the material in gut contents or fecal pellets bore any identifiable structural similarity to cells/filaments prior to ingestion. The results suggest that earlier studies of pontoporeiid gut contents may seriously underestimate the importance of algal components in the amphipod's diet and imply that Diporeia sp. growth and production may be more closely linked to primary production than previously thought.

QUINN, F.H. A regional precipitation index for Lake Michigan-Huron water level fluctuations. Preprint, Fifth Conference on Climate Variations, Denver, CO, October 14-18, 1991. American Meteorological Society, Boston, MA, 143-144 (1991).

No abstract.

QUINN, F.H. Effects of climate change on the water resources of the Great Lakes. Proceedings, Climate Change on the Great Lakes basin, Annual Meeting of the American Association for Advancement of Science, Chicago, IL, February 1992. Illinois State Water Survey, Champaign, IL, 10-16 (1992).

The Great Lakes contain about 95 percent of the U.S.'s fresh surface water supply and 20 percent of the world's fresh surface water supply. These water resources serve many uses including hydropower, industrial, navigation, municipal, recreational, and fish and wildlife habitat. Recent studies on possible impacts of climate change, using general circulation model outputs coupled with hydrologic simulation models, indicate a 23-51 percent reduction in Great Lakes net water supplies. Potential lake level changes range from -0.4 meter for Lake Superior to as much as -2.5 meters on Lakes Michigan and Huron. These results have major environmental and socioeconomic implications and will require new paradigms in water resource management for the Great Lakes.

QUINN, F.H. Hydraulic residence times for the Laurentian Great Lakes. Journal of Great Lakes Research 18(1):22-28 (1992).

The Laurentian Great Lakes comprise one of the major water resources of North America. For many water quality studies the hydraulic residence times or replacement times of the Great Lakes serve as measures of how quickly water quality will change in response to changes in contaminant loadings. The residence time for a conservative substance represents the average time a conservative substance which remains dissolved in the water spends in a lake. The hydraulic residence times of conservative substances for the Great Lakes are relatively long ranging, from close to 200 years for Lake Superior to a little over 2 years for Lake Erie. A major reduction of 38 years was found in the residence time for Lake Michigan (62 years as compared with the 100 year value previously reported) due to the consideration of flow exchange between Lakes Michigan and Huron. This indicates that Lake Michigan may respond much faster to reductions in contaminant loadings than previously expected. Because of their low ratio of volume to outflow, only Lakes Erie and Ontario are affected by normal climatic variations of less than 20 years in duration. Extreme lake level conditions over the period of 2 to 8 years can also significantly affect the residence times of Lakes Erie and Ontario. Thus, high levels in the early 1970s may have contributed to the improvement of water quality in Lake Erie. Existing diversions and potential global warming appear to have no significant effect on residence times.

QUINN, F.H. Outlook for future water supplies to the Great Lakes. Proceedings, International Symposium, Water Pipelines and Diversions in the Great Lakes Basin, Waterloo, Ontario, Canada, March 12-13, 1991. Department of Geography Publication Series, Occasional Paper No. 13, University of Waterloo, 63-69 (1991).

No abstract.

Redalje, D.G., S.E. Lohrenz, and G.L. FAHNENSTIEL. The relationship between primary production and the export of POM from the photic zone in the Mississippi River Plume and inner Gulf of Mexico shelf regions. Nutrient Enhanced Coastal Ocean Productivity Workshop, Louisiana Universities Marine Consortium, New Orleans, LA, October 1-4, 1991. 105-110 (1992).

As part of the NOAA Nutrient Enhanced Coastal Ocean Productivity program we examined the relationship between rates of primary production and the vertical export of POM out of the photic zone in the Mississippi River plume and inner Gulf of Mexico shelf regions. The study was conducted during both high (March 1991) and low (July/August 1990) river discharge periods. July/August rates of production were 4-10 gCm-2d-1 in the plume and 2-4 gCm-2d-1 on the shelf. During March, production rates were 0.4-0.7 gCm-2d-1 and 0.1-0.5 gCm-2d-1 for the plume and shelf regions, respectively. During July/August, 3-9 percent of the POC production was exported out of the photic zone in both regions, while during March, 64-266 percent was exported. We attribute the observed export differences to temporal variability in phytoplankton species composition and in the activities of zooplankton grazers.

REID, D.F., and A.M. BEETON. Large Lakes of the World: A global science opportunity. GeoJournal 28.1:67-72 (1992).

Recent commentaries have expressed growing concern about the present state of limnology in the United States. Two basic problems are perceived: (1) there are no separate, dedicated funding programs in the US for basic limnologic research; and (2) limnology has failed to enter the global "big science" era of the 90's. While both the oceans and atmosphere are subjects of large, multinational global-scale scientific programs, similar large studies of lakes have been limited, at best, to regional studies. There are over 250 large lakes worldwide, spanning the globe from 80oN to 60oS and ranging from hypersaline to fresh water. Altogether they contain over 68% of the earth's fresh liquid surface water. However, these large ecosystems are increasingly threatened by global anthropogenic change such as illconceived diversions, uncontrolled consumption, and progressive degradation of water and overall ecosystem quality. Global climate change is but another anthropogenic global-scale problem with potential future effects on large lakes. An organized, multinational framework for the study of large lakes on a global scale is outlined.

ROBBINS, J.A., G. Lindner, W. Pfeiffer, J. Kleiner, H.H. Stabel, and P. Frenzel. Epilimnetic scavenging of Chernobyl radionuclides in Lake Constance. Geochimica et Cosmochimica Acta. Vol. 56:2339-2361 (1992).

Radioactive debris from the Chernobyl reactor accident entered Lake Constance in southwestern Germany mainly through one rainfall episode on April 30, 1986. Nuclides scavenged by particles in a newly established epilimnion accumulated in traps deployed weekly (20 m depth) at a site in the Uberlinger See, a northwestern bight of the lake. Activities of 137Cs and 103Ru (plus 106Ru, 125Sb, 110mAg, and 144Ce) in trapped material collected during the subsequent 21 weeks is here described by a two-stage scavenging model involving (1) nuclide transfer to "reactive particles" with negligible mean settling rate and (2) their entrainment by large, rapidly settling particles dominated by chemically passive calcite formed seasonally in the epilimnion. The model employs first-order kinetics where forward rate coefficients depend on time-dependent concentrations of candidate "reactive phases" such as total suspended matter (TSM), particulate inorganic matter (PIM), particulate organic matter (POM), and particulate aluminum (PAL). First-order, irreversible nuclide transfer to nonexchangeable portions of reactive phases is also included. Vertical transport is described by a time-dependent rate of particle settling through a vertically and horizontally well-mixed epilimnion of increasing depth. Model calculations reproduced observations well with PAL as the "reactive phase" for 137Cs and POM for 103Ru. Calculated reaction rates for all nuclides were sufficiently high that activity changes were dominated by temporal variations in pertinent state variables. Selective chemical extraction of Chernobyl 137Cs from sediments and study of uptake kinetics by addition of radiocesium to fresh sediment suspensions supported model results indicating its negligible affinity for calcite, probable transfer to clay minerals (for which PAL is a surrogate), particle concentration-independent distribution coefficient, and significant transfer to nonexchangeable sites. For 103Ru, model calculations implied no transfer to nonexchangeable sites and a forward rate term proportional to the square root of POM concentration, a result in accord with the Honeyman-Santschi "Brownian pumping: model." The unusual coincidence of a pulsed nuclide loading with conditions of thermal stratification and limited vertical water mass exchange, together with frequent measurement of important state variables, permitted successful evaluation of a reaction-kinetic model under markedly non-steady state conditions.

Ross, P.E., G.A. Burton, E.A. Crecelius, J.C. Filkins, J.P. Giesy, C.G. Ingersoll, P.F. LANDRUM, M.J. Mac, T.J. Murphy, J.E. Rathbun, V.E. Smith, H.E. Tatem, and R.W. Taylor. Assessment of sediment contamination at Great Lakes areas of concern: The ARCS program toxicity-chemistry work group strategy. Journal of Aquatic Ecosystem Health 1:193-200 (1992).

In response to a mandate in Section 118(c)(3) of the Water Quality Act of 1987, a program called Assessment and Remediation of Contaminated Sediments (ARCS) was established. Four technical work groups were formed. This paper details the research strategy of the Toxicity-Chemistry Work Group. The Work Group's general objectives are to develop survey methods and to map the degree of contamination and toxicity in bottom sediments at three study areas, which will serve as guidance for future surveys at other locations. A related objective is to use the data base that will be generated to calculate sediment quality concentrations by several methods. The information needed to achieve these goals will be collected in a series of field surveys at three areas: Saginaw Bay (MI), Grand Calumet River (IN), and Buffalo River (NY). Assessments of the extent of contamination and potential adverse effects of contaminants in sediment at each of these locations will be conducted by collecting samples for physical characterization, toxicity testing, mutagenicity testing, chemical analyses, and fish bioaccumulation assays. Fish populations will be assessed for tumors and external abnormalities, and benthic community structure will be analyzed. A mapping approach will use low-cost indicator parameters at a large number of stations, and will extrapolate by correlation from traditional chemical and biological studies at a smaller number of locations. Sediment toxicity testing includes elutriate, pore water, and whole sediment bioassays in a three-tiered framework. In addition to the regular series of toxicity tests at primary mater stations, some stations are selected for a more extensive suite of tests.

Schulze, P., J.R. Strickler, B.I. Bergstrom, M.S. Berman, P. Donaghay, S. Gallager, J.F. Haney, B.R. Hargreaves, U. Kils, G.-A Paffenhofer, S. Richman, H.A. VANDERPLOEG, W. Welsch, D. Wethey, and J. Yen. Video systems for in situ studies of zooplankton. Arch. Hydrobiol. Beih. Ergebn. Limnol. 36:1-21 (1992).

A variety of survey instruments and systems designed for measuring the behavior of individual zooplankton have been built around video technology. Systems designed for studying behavior are already producing remarkable observations of biological interactions in situ. If the survey tools under development achieve their potential, they will surpass the spatial and temporal resolution of conventional sampling methods, reduce the amount of human effort required for data processing, and also collect taxonomic information that is not available from acoustic devices or the Optical Plankton Counter. This paper (i) describes a variety of video systems for studying zooplankton in situ; (ii) discusses common design considerations and technical challenges, and (iii) compares the present and future capabilities of video devices with other methods of studying zooplankton in situ.

Trefry, J.H., R.P. Trocine, S. Metz, T.A. Nelson, and N. HAWLEY. Suspended particulate matter on the Louisiana Shelf: Concentrations, composition, and transport pathways. Proceedings, Marine Consortium Workshop, TAMU-SG-92-l09, October 1-4, 1991. Texas A&M University, College Station, TX, 126-130 (1992).

The concentrations, composition, and transport pathways of suspended particulate matter and particulate organic carbon (POC) have a direct bearing on the development and persistence of shelf hypoxia as well as on the global cycling of carbon. More than 120 CTD-transmissometer profiles and >400 particle samples were collected from the Mississippi River and adjacent Gulf of Mexico on cruises during July-August 1990 and February 1991. River flow is a dominant factor in controlling particle distributions; however, time-series data show that tides and weather fronts can greatly influence concentrations and movement of suspended matter. Results from chemical analyses show that concentrations of POC range from >80 mmol/L (>1 ml/L) at near-river locations to <0.8 mmol/L (<0.01 mg/L) in some deep offshore waters. The organic fraction of the suspended matter increases from <5 percent of the total mass near the river mouth to >90 percent along the shelf at about 10 km from the river. The C/N molar ratio in suspended particles from throughout the shelf is near uniform at 6. Plumes of particle-rich water at outer shelf depths of about 100 m, along with transport in near-bottom nepheloid layers, carry a POC burden that can be traced tens of kilometers offshore.

VANDERPLOEG, H.A., S.J. BOLSENGA, G.L. FAHNENSTIEL, J.R. LIEBIG, and W.S. GARDNER. Plankton ecology in an ice-covered bay of Lake Michigan: utilization of a winter phytoplankton bloom by reproducing copepods. Hydrobiologia 243/244:175-183 (1992).

Plankton ecology was examined during the 1986 winter in Grand Traverse Bay, a 190-m deep, fjord-like bay on Lake Michigan. Before ice cover, algal concentration was low and uniformly distributed with depth, as it is in open Lake Michigan. During ice cover (February and March), a bloom of a typical winter-spring phytoplankton developed in the upper 40-m, resulting in a 4-7 fold increase in feeding rate of adult Diaptomus spp. High algal concentration and zooplankton feeding persisted after ice melt (April). During and after ice cover, lipid concentrations of Diaptomus dropped rapidly from 34% of dry weight to 17% because of high egg production. High incident photosynthetically active radiation (PAR), high (45-50%) PAR transmittance of the ice due to little snow on the ice,a nd water column stability were probably responsible for the bloom. High ice transparency may be a common feature of large lakes and bays, where strong winds blow snow cover off the ice, or at low latitudes where snow melt due to occasional rains and warm temperatures is common. Winter reproducing calanoid copepods use these blooms to increase their reproductive output.

VANDERPLOEG, H.A., W.S. GARDNER, C.C. Parrish, J.R. LIEBIG, and J.F. CAVALETTO. Lipids and life-cycle strategy of a hypolimnetic copepod in Lake Michigan. Limnology and Oceanography 37(2):413-424 (1992).

Concentration and composition of lipids varied seasonally in adult female Diaptomus sicilis, a hypolimnetic suspension-feeding calanoid copepod, in Lake Michigan. Triacylglycerol (TG) was the predominant storage lipid; its level remained high (33-40% of dry wt) from June through January. During the period of reproduction from February through May, TG dropped steeply to a low of 9%. The abrupt increase in TG concentration from May to June was probably caused by the recruitment of nonreproducing adult females. Throughout summer and fall ovaries remained unripe. Feeding experiments at satiating food concentrations at 6o and 20oC suggest that low temperature and the hypolimnion was a major reason that ovaries did not ripen. Stored TG served as a potential buffer to starvation, although starvation conditions did not occur. By remaining in the hypolimnion rather than in the epilimnion, D. sicilis is assured a relatively stable supply of algae, low metabolic rate, and escape from predation. These advantages may have to be weighed against a reproductive bottleneck of low temperature.

Washburn, L., B.H. Jones, A.W. BRATKOVICH, T.D. Dickey, and M.S. Chen. Mixing, dispersion, and resuspension in vicinity of an ocean wastewater plume. Journal of Hydraulic Engineering 118(1):38-58 (1992).

Buoyant plumes discharged from ocean outfalls are important for dispersing municipal wastewater into the marine environment in many coastal areas, although field studies of operating outfall systems are rare. Here, we report on an extensive field study of the effluent plume from one of the largest wastewater outfalls on the west coast of the United States. This study shows that the dispersion and mixing levels of the plume depend upon the local current speed and ambient density stratification. Under these highly stratified, late-summer conditions, we find that a combination of temperature, salinity, turbidity, and chlorophyll fluorescence measurements are required to unambiguously identify plume waters. Over the course of these observations, the local current speed at plume depth varied from 0.1 m/s to 0.07 m/s, corresponding to a Froude number Fr range of 10-3 to 0.2. A limited number of dilution estimates are made for the lower Fr case, and these fall in the range 110 to 160, which is within the design range for this type of diffuser. The observed maximum height of rise and wastewater field thickness are in reasonable agreement with laboratory results for zero current speed (Fr = 0). At the higher current speed, turbidity layers originating at the sea floor are observed which result from resuspension of bottom sediments.

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