William T. Waller

The Relationship of Fresh-Water Protozoan Communities to the MacArthur-Wilson Equilibrium Model

Two series of 10 artificial substrates each were placed in Douglas Lake, Michigan, and their colonization by species of fresh-water protozoans studied. Identifications were made to species whenever possible at intervals of approximately one week, and rough estimates of density were made as well. Although the aggregations of species colonizing each of the substrates were not identical, the colonization process itself was remarkably similar for the entire series. When the number of species was plotted against time in days, a simple exponential curve adequately described the relationship. Colonization rates and extinction rates were compared with the equilibrium model for island faunas proposed by MacArthur and Wilson. These results suggest that the formation and composition of protozoan communities on artificial substrates are the result of interactions comparable to those proposed by MacArthur and Wilson.

Triclosan in a north Texas wastewater treatment plant and the influent and effluent of an experimental constructed wetland.

The antimicrobial triclosan was analyzed in unfiltered samples from influent, effluent, and receiving stream and before and after a pilot-scale constructed wetland at a North Texas municipal wastewater treatment plant. Triclosan concentrations were reduced by 97 to 99% by the activated sludge treatment plant. Effluent concentrations were further reduced by passage through the constructed wetland, but receiving stream concentrations were not statistically significantly different from effluent concentrations. Effluent concentrations of triclosan were seasonal with highest concentrations occurring during the summer months. The effluent-dominated receiving stream maximum concentrations during summer months were below reported algal no-observed-effect concentrations based on biomass and growth rate but exceeded concentrations reported to cause shifts in algal community structure.

Temporal and spatial variability in the estrogenicity of a municipal wastewater effluent.

The estrogenicity of a municipal wastewater effluent was monitored using the vitellogenin biomarker in adult male fathead minnows (Pimephales promelas). The variability in the expression of vitellogenin was evident among the monitoring periods. Significant (alpha< or =0.05) increases in plasma vitellogenin concentrations were detected in March and December, but not in August or June. Additionally, the magnitude of expression was variable. Variability in the spatial scale was also evident during the March and June exposure months. Concurrent exposures in both the creek receiving the effluent from a wastewater treatment plant and an experimental wetland showed estrogenicity to be different with distance from the respective effluent inflow sites. March exposures showed estrogenicity to be somewhat persistent in the receiving creek (>600 m), but to decrease rapidly within the experimental wetland (<40 m). Results are discussed relative to the monitoring season, to the spatial distribution of the response in both receiving systems, and to possible causative factors contributing to the effluent estrogenicity.

The use of fish movement patterns to monitor zinc in water

Abstract The feasibility of using fish movement patterns measured by light beam interruption as a technique for continuous monitoring of the response of fish to zinc was investigated. The apparatus does not in any way interfere with fish movement within the test chamber and allows for the maintenance of fish for long time periods. Under the conditions described the system detects premortal aberrations in fish movement caused by zinc. The detection of stress occurs in sufficient time to permit survival of the test fish if stress conditions are reversed at the time of detection. The lowest concentration of zinc detected by the system during a 96-h exposure was between 3.64 and 2.94 mg 1 −1 Zn 2+ . The systems range of effective measurement as related to turbidity is discussed. This methodology should detect other toxicity equally well.

The use of fish as sensors in industrial waste lines to prevent fish kills

The report of the Council on Environmental Quality (1970) repeatedly stresses the need for the development of predictive, simulative, and managerial capabilities to combat air and water pollution. The last capability depends on the first two . For example, the effects of every waste put into a river will have to be predicted if the river is to be managed as a system wherein industrial use of the water does not preclude other uses such as recreation and municipal water supply . In addition, the effects of alternative river management schemes should be simulated first, and then carefully monitored when the schemes are put into practice . In short, the capability of successfully managing a river for many uses depends on the capability to predict effects . The capability of predicting biological effects is particularly important, because desirable functions of aquatic ecosystems, such as waste assimilation and game fish production, depend on living organisms . The standard fish bioassay, which uses death as a response, enables one to predict the toxicity of a particular waste to fish . One limitation of the standard bioassay is that it uses a grab sample which represents the quality of the waste at one point in time . The water used to make the dilutions is also taken at one point in time . At the actual industrial site, the quality of the waste and the river water vary through time. A composite waste sample partially overcomes this limitation, but may mask variations that are biologically important . For example, the toxicity of zinc to fish is affected by the calcium concentration and temperature of the water

A Minimally Invasive Technique to Monitor Valve-Movement Behavior in Bivalves

A real time, minimally invasive method to observe valve movement of bivalves using proximity sensors and a personal computer has been developed. The method is being evaluated as a tool to assess both episodic toxicity events and ambient toxicity. The method described minimizes contact with the animal to the anchoring of one valve and the placement of a small aluminum foil disk on the other valve, and allows the measurement of the distance that a clams valves are open. Using proximity sensors and an aluminum foil target, valve movements of the Asiatic clam, Corbicula fluminea were measured and digitally recorded using a data acquisition board and a personal computer. One advantage of this method is its use of readily available stock electronics. In its final form, we envision an in situ biological monitoring system using C. fluminea deployed in aquatic systems in association with automated physical/chemical monitoring systems like those found at USGS gauging stations. A tool such as this could be used as ...

The Effects of pH, Solubility and Temperature Upon the Acute Toxicity of Zinc to the Bluegill Sunfish (Lepomis macrochirus Raf.)

BIuegill sunSsh (Lepomis macrochirvs RaISnesque) were exposed for 96 hours under static test conditions to water soluble ZnSO4*7H2O and water insoluble Zn3(PO4)2*4H20 at two temperature ranges (21-24°C; 7-9°C) and two pH ranges ( 5.7-7.0; 7.3-8.8) . Control Esh were maintained in water containing no zinc. No bluegills died in water containing insoluble zinc in amounts comparabIe to the amounts of soluble zinc (13.50, 18.00, 24.00, and 32.00 mg Zn++/l) which produced mortalities of 90 to l°°o- Bluegill mortalities in concentrations of soluble zinc ranging from 10 to 32 mg Zn++/l were 0 to 10°zn at the high pH, while at the low pH mortalities were lOOSo. Bluegills at the low temperatures died at a much slower rate, and the time-to-death of the first Esh was considerably delayed, in comparison to bluegills at the warmer temperature. Continuous flow bioassay tests in which two types of test containers were used showed differences in 96-hour TLm values. The particle replacement time in 19-liter bioassay jars was considerably longer ffian in 1.4-liter plexiglass containers, hence bluegills sunived longer in the jars. Ninety-six-hour TLm concentrations for Esh exposed to a continuous flow of Zn++ in tnvo types of test containers were estimated in four ways: using statistically pooled measured and calculated concentrations, and by pooling calculated and measured concentrations on the basis of the nominal concentrations alone. There were small differences in the resulting TLm values, a result which should be of interest to other workers using

Monitoring Watersheds: Biomonitors and Other Measures

(2002). Monitoring Watersheds: Biomonitors and Other Measures. Journal of Urban Technology: Vol. 9, No. 2, pp. 1-19.

Modelling and control of a simple trophic aquatic system

Abstract Artificially assembled and maintained trophic systems require real-time measurement and control of environmental and biological variables, either because these are part of the system’s purpose, as it occurs in biosensing, or because they are needed for performance and stability, as in closed ecological life support systems (CELSS). The design of control strategies needed in these two cases benefit from a model of the system dynamics. As an example, we modelled closed-loop controllers of a two-level artificial aquatic trophic system consisting of a cladoceran population feeding on algae supplied from a culture. The control of the cladoceran is based on a stage-structured model of its population dynamics and the food density, obtained as a balance of the rates of supply from the algae culture and of consumption by the cladoceran. The animal model assumes that females switch from asexual to sexual reproduction at low food density. The control strategy maintains the animal population in the asexual cycle and is based on two controllers. One to limit animal population growth by harvesting in accordance to food supply availability and another to adjust food supply in order to maintain the food density at a constant reference level above the threshold for sexual reproduction. Both controllers require real-time estimates of food density and total animal density; however, measurements of animal density by stage (adults and neonates) are assumed to be unavailable. The second controller, a proportional-derivative linear law, maintains the cladoceran in the asexual cycle by avoiding changes in reproductive behavior due to lack of adequate food density. The first controller calculates a harvest rate based on departures of the food consumption from a reference value, which was selected conservatively as only a fraction of food supply availability. Two alternative designs, linear and nonlinear, for the harvest controller were simulated and compared. Simulations of the model system (controllers, animal and food) are employed to investigate the effect of the controllers on short-term stability and transient behavior. All simulations started from zero animal density and a pulse inoculation of resting eggs ready to hatch. After post-inoculation transients, sudden changes in the consumption reference were also implemented to evaluate tracking response to these changes. As expected, the nonlinear control yielded better consumption rate transient behavior for both post-inoculation and tracking. Animal density fluctuations during the post inoculation period were not dampened due to the conservative assumptions of unavailability of real-time measurements of density by stage. We conclude that this control strategy is feasible but that further work is needed for implementation. In future work, we plan to address issues that limit current applicability of the model: generate real data for calibration and validation, extend controls to long-term behavior, and include other limiting factors and processes.

Estimating pesticide exposure in tidal streams of Leadenwah Creek, South Carolina

This article estimates the potential exposure of estuarine organisms to two pesticides (azinphosmethyl and fenvalerate) in a tidal stream of Leadenwah Creek near the Edisto River, South Carolina, during four runoff episodes. Exposure is calculated from simulation runs of the one-dimensional transport equation solved by an implicit finite difference method. Calibration was done for each episode by adjusting three conditions (runoff starting time, duration, and flow) and a correction to the dispersion coefficient in order to match the continuously measured salinity transients. First-order rate constants used by the fate component were calculated from half-life values reported in the literature. Baseline scenarios for each episode and each pesticide were derived by using the same conditions obtained in the salinity runs and adjusting the pesticide loading in order to mimic the few data points of measured pesticide concentrations. In all baseline scenarios, pesticide concentration rises following the initial burst of runoff (also noticeable as an abrupt drop in salinity) and then oscillates, forced by the tidal cycle. These oscillations are dominated by transport, while fate imposes a secular decaying trend. Ten additional scenarios for each episode were obtained from the baseline scenario by randomly varying three pesticide load parameters (starting time and duration of runoff, and pesticide discharge) using a Latin hypercubes design. Two exposure metrics were calculated from the simulated and the measured pesticide concentration: maximum and time average, which was obtained by integrating the curve and dividing by the time period. The metrics calculated from the baseline runs are relatively close to the data-derived metrics, because the baseline runs attempted to mimic the data. For each one of the two metrics and all pesticide-episode combinations, several statistics of the set of 11 scenarios were also calculated: minimum and maximum, mid-range, mean, standard deviation, and median. The mean +/- standard deviation interval of the simulation-derived value consistently brackets the data-derived value for the maximum metric, but not for the time-average metric. This may indicate that even if the maximum value is correctly captured in the field sample, the time-average exposure could be in error when calculated directly from the field data due to undersampling of the pesticide time series. The methodology developed here attempts to reconstruct the possible exposure from the sparse sampling of the pesticide concentration during the runoff episodes; only when the number of field samples is high and regularly spaced is it possible to have confidence in the reconstruction of the curve. The shape of the curve cannot be inferred from the field measurements alone; as expected, tidal movement makes the pesticide concentration swing up and down. This result has important implications because the biological community would be subject to repetitive pulses of exposure to the chemicals. The baseline simulations can be used to derive a pulse-exposure metric by calculating the sum of ratios of the time average of the threshold-exceeding concentrations to the time average of the toxic threshold during intervals of above-threshold concentration. This metric is species specific and extrapolates laboratory toxicity data in order to compare pulse exposure to mortality rates measured in the field.