Kenneth L. Dickson

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.

Estimating the hazard of chemical substances to aquatic life

The assessment of the hazard associated with the introduction of chemical substances into the environment is receiving considerable attention in current ecological, political, and public forums. The purpose of this paper is to identify and evaluate the basic concepts involved in assessing the hazard of chemical substances to aquatic life. A conceptual framework for conducting a hazard assessment is elaborated. In addition, several proposed procedures for conducting aquatic hazard assessment are compared and contrasted. A discussion of the decision criteria currently utilized in hazard assessment procedures is included. The use of safety factors or ‘uncertainty factors’ as a central concept in a sequential testing approach is presented. An assessment of the ‘state-of-the-art’ in aquatic hazard assessment and recommendations for suceeding stpes in the development of procedures constitute the conclusion of the paper.

Kinetics of chromium transformations in the environment

Kinetics of chromium transformations under typical environmental conditions were systematically investigated using batch, microcosm and column experiments. Oxidation and reduction rates were evaluated in single phase water systems and in two phase water-solid systems. Natural and reference waters, sediments and soils representing a broad range of characteristics were used. Some of the investigated reactions, such as the reduction of Cr(VI) by S2- or Fe2+ ions under anaerobic conditions, were instantaneous and the experimental results exactly followed the stoichiometric and equilibrium calculations. Other reactions, such as the reduction of Cr(VI) by organics in sediments and soils, or the oxidation of Cr(III) by MnO2, were much slower and clearly exhibited kinetic controls. Reduction of Cr(VI) by organics was dependent on both the type and amount of organic material. Dissolved oxygen by itself did not induce measurable oxidation of Cr(III), spiked to the experimental waters, after 128 days. Slow Cr(III) oxidation to Cr(VI) was only noted in one of the natural waters and sediments with half-lives ranging from 2 to 9 years. In all cases the extent of Cr(III) oxidation did not exceed 15% of the initial Cr(III) present. The overall results indicate that the transport and transformation of chromium can be predicted using kinetics data derived from a simplified laboratory experiment, the Eh-pH data and the aquatic system characteristics. Results of the microcosm and laboratory experiments were in good agreement with the predicted concentrations.

Comparison of Heavy Metal Interactions in Acute and Artificial Stream Bioassay Techniques for the Asiatic Clam ( Corbicula fluminea )

Population densities of the Asiatic clam, Corbicula fluminea, in the thermally influenced areas of the New River at the Glen Lyn power plant, Glen Lyn, Va., increased from zero before 1975 to approximately 11 522/m 2 by February 1978. Since their establishment, clams in the thermal effluent have served as a source of propagules for clam invasion into other areas of the New River during the warmer seasons. Copper was more toxic (LC 5 0 = 0.04 ppm) to the clam than zinc (LC 5 0 = 6.04 ppm) or copper-zinc simultaneously (LC 5 0 = 0.05 ppm) in 96-h static bioassays. Ninety-six-h LC 5 0 determinations in artificial stream bioassays were at least one order of magnitude higher when compared with the static test values (the LC 5 0 values for copper and copper-zinc combined were 0.49 and 3.06 ppm, respectively). The LC 5 0 values appeared also to be the effective concentration at which at least 50 percent of the clams demonstrated a gaping response and cessation of filtering activity. Elemental bioaccumulation of copper and zinc was more prevalent in the visceral tissue than in concentrations measured from clam valves or from the water in both laboratory bioassays and field determinations. When copper bioaccumulation in the viscera increased to approximately 275 to 400 ppm, gaping and a lack of filtering activity were evident in 96-h tests. Behavioral mechanisms-cessation of filtering activity and the closure of valves during stress-were considered to be likely factors in producing the higher LC 5 0 values, when compared with other invertebrate responses.

Determining fish avoidance of polluted water

A critical evaluation is given of material and methods to be used for the study of behavioral responses of fish towards polluted water. Experiments with Fathead minnows in a steep gradient of hypochlorite are described and discussed. Methods leading towards standarization of fish avoidance reactions are advocated.

A review and analysis of some methods used to measure functional aspects of periphyton

Historically, assessments of water quality using periphytic communities have centered around indexes of structure such as biomass estimates, diversity indices, cluster analyses, and species abundances and distributions. However, perturbation of a communitys structural attributes may not be concomitant with functional changes, and it follows that protection of community structural integrity would not signify protection of ecosystem function. A series of model streams provided semicontrolled experimental conditions for study of nontaxonomic attributes of periphytic community structure and function (photosynthesis) in response to a variety of perturbants. Over all of the model stream experiments, measured functional values were statistically less variable (P = 0.05) than measured structural values. No significant reduction in variability of structural or functional measurements was found for the treated streams relative to untreated or reference streams. A unified effort incorporating both structural and functional measurements should yield information adequate for accurate evaluation of impacts of perturbants on periphytic communities and aquatic ecosystems.

Estimating Aufwuchs Biomass

Estimates of Aufwuchs biomass derived from gravimetric, phytopigment, and adenosine triphosphate (ATP) analyses are evaluated and compared with respect to each methods specificities and biases. Samples of Aufwuchs from glass slides in artificial streams treated with chlorine, copper, dichromate, sucrose, dextrose, phosphate, or nitrogen were used to compare these nontaxonomic methods as water quality assessment techniques. The correlations and limitations of the methods are discussed. ATP analysis compared very favorably with the other techniques and added another important dimension in water quality assessment. When corrected for extraction efficiency, ATP analyses provide a reliable estimate of Aufwuchs biomass. This estimate can be used in combination with other estimates of biomass to partition the community into autotrophic-heterotrophic components or viable organic carbon and non-viable organic carbon. Ratios of organic carbon estimates such as chlorophyll a organic carbon/ash-free dry weight organic carbon (Trophic Index), chlorophyll a organic carbon/ATP organic carbon (Functional Trophic Index), and ATP organic carbon/-ash-free dry weight organic carbon (Viability Index) were used to further assess the impact of perturbations on the biomass of the Aufwuchs community.

Effects of suspended solids on the bioavailability of chlordane toDaphnia magna

Research was conducted to assess the importance of suspended solids (ss) types and levels and associated organic carbon contents on the bioavailability of chlordane toDaphnia magna. The dose response relationship ofD. magna to chlordane was established in the absence of suspended solids. Test waters with suspended solids levels of approximately 0, 100, 500, and 750 mg/L contained a chlordane concentration which caused ∼80% mortality of the test population in 48-hr. The effects of different types and levels of suspended solids onD. magna mortality were observed. Both montmorillonite clay (0 organic carbon) and pond sediments (1.7% organic carbon) reduced bioavailability of chlordane toD. magna. Suspended solids characteristics were not a determining factor In the reduction of the bioavailability of chlordane toD. magna as long as a threshold level (>200 to 300 mg/L) of suspended solids was present.

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 ...

Fish bioassay monitoring of waste effluents

Spills of toxic materials into bodies of water receiving industrial waste discharges can be prevented only if frequent or continuous assessments of effluent quality can be made. Currently available methods can automatically measure individual physical or chemical waste components but cannot assess toxicity caused by the interaction of components or the presence of an unsuspected material. Aquatic organisms, in contrast, respond to their total environment and in this way integrate the effects of all the various chemical and physical waste parameters.This study evaluates the possibility of using the continuously and automatically recorded responses of fish to monitor the toxicity of industrial waste effluents. A review of previously developed toxicity monitoring systems is followed by a field evaluation of a method that uses the computer-monitored ventilatory patterns of 12 bluegills (Lepomis macrochirus Rafinesque) to monitor the toxicity of an industrial waste effluent as it flows into a river. No known toxic spills occurred in the effluent during the operation of this system, but acetone added to the effluent waste caused responses from the fish at concentrations which peaked near the 96-hr LC50 level. Some responses were also noted when no known toxicant was present; these were related to environmental disturbances and system design problems. Recommendations are made for the design of future biologic monitoring units.