Edward N. Leonard

Toxic effects of cadmium on three generations of brook trout (Salvelinus fontinalis)

Abstract Three generations of brook trout (Salvelinus fontinalis) were exposed to several concentrations of total cadmium (0.06–6.4 μg Cd/liter). Significant numbers of first- and second-generation adult males died during spawning at 3.4 μg Cd/liter. This concentration also significantly retarded growth of juvenile second- and third-generation offspring. The maximum acceptable toxicant concentration (MATC) for brook trout exposed to cadmium in Lake Superior water (hardness 44 mg/liter as CaCO 3, pH 7–8) lies between 1.7 and 3.4 μg Cd/liter. Cadmium-residue analyses of kidney, liver, gill, gonad, spleen, muscle, and red blood cells frown first- and second- generation trout indicated that kidney, liver, and gill tissue accumulated the greatest amounts of cadmium at each water exposure concentration. No significant increases in cadmium were measured in edible muscle at any of the cadmium water concentrations tested. Cadmium residues in kidney, liver, and gill tissue of fish frown all exposure concentrations ...

Development and evaluation of test methods for benthic invertebrates and sediments: Effects of flow rate and feeding on water quality and exposure conditions

In order to ensure among-laboratory comparability in the results of sediment toxicity tests, it is necessary to characterize the influence of variations in test regimes on organism responses and exposure conditions. The objective of these studies was to develop and document an optimized combination of overlying water renewal (flow) and feeding rates for sediment tests with three commonly used benthic species (midges, Chironomus tentans; amphipods, Hyalella azteca; oligochaetes, Lumbriculus variegatus). Optimal conditions were defined by a number of chemical and biological considerations including: (1) flow rate through the system, (2) amount of food added, (3) acceptable responses (survival, growth, reproduction) of the organisms over the course of a 10-day test, and (4) maintenance of an adequate concentration of dissolved oxygen in overlying water. The goal was to minimize factors (1) and (2), while maximizing criteria (3) and (4). The major reason for minimizing (1) and (2) was the concern that excessive water flow or addition of food could reduce exposure of the test organisms to sediment-associated contaminants. To evaluate this, interstitial (pore) water concentrations of contaminants (ammonia, zinc, copper, dieldrin) were measured over the course of 10 day tests conducted with a number of different sediments under various flow and feeding regimes. The different combinations of flow/feeding had variable effects upon pore water concentrations of contaminants; for example under our optimized regime, in some instances slight decreases in interstitial water contaminant concentrations were observed, whereas in other cases contaminant concentrations remained constant or even increased. Overall, the use of minimal water renewal and feeding rates should result only in small changes in exposure of benthic organisms to contaminants in pore water over the course of 10-day tests.

Seasonal variation of acid volatile sulfide concentration in sediment cores from three northeastern Minnesota lakes

Acid volatile sulfide (AVS) is a natural agent in sediments which complexes some cationic metals and thereby influences the toxicity of these metals to benthic organisms. Because of its influence on metal bioavailability, AVS has been proposed as a key normalization phase for the development of sediment quality criteria for metals. However, studies conducted primarily in marine and estuarine systems have shown that AVS concentrations can vary markedly both temporally and with (sediment) depth. In this study, AVS concentrations were measured monthly for 16 mo in several segments of sediment cores from three freshwater lakes: Caribou Lake, Fish Lake and Pike Lake in northeastern Minnesota, USA. The concentrations of AVS in cores from the three lakes varied inversely with sediment depth. AVS concentrations also varied seasonally by as much as two orders of magnitude and were directly correlated with changes in water temperature. The correlation between AVS and temperature likely was related both to changes in primary productivity and sediment microbial activity.

Long-Term Effects of Zinc Exposures on Brook Trout (Salvelinus fontinalis)

Abstract Exposure of three generations of brook trout (Salvelinus fontinalis) to zinc concentrations ranging from 2.6 to 534 μg/liter produced no significant harmful effects. During a separate exposure of embryos and larvae, 1,368 μg Zn/liter significantly reduced (P = 0.05) both embryo and 12-week larval survival. An additional partial chronic exposure also resulted in significantly reduced (P = 0.05) egg chorion strength and embryo survival at 1,360 μg Zn/liter. The maximum acceptable toxicant concentration (MATC) for brook trout exposed to zinc in Lake Superior water (hardness = 45.4 mg/liter as CaCO3; pH = 7.0–7.7) lies between 534 and 1,360 μg Zn/liter. The 96-hour LC50 (median lethal) concentration for brook trout was 2,000 μg Zn/liter; thus the application factor (MATC/96-hour LC50) lies between 0.267 and 0.680. Brook trout gill, liver, kidney, and opercular bone tissues accumulated the greatest amounts of zinc. Edible muscle tissue did not accumulate zinc. Zinc loss from gill and liver from first-...

Chronic Effects of Cadmium and Zinc Mixtures on Flagfish (Jordanella floridae)

Abstract Flagfish were exposed to cadmium and zinc as individual metals and as mixtures (4.3-8.5 μg Cd/liter and 73.4-139 μg Zn/liter) through one complete life cycle in Lake Superior water (45 mg/liter total hardness). Cadmium and zinc did not act additively at sublethal concentrations when combined as mixtures; however, a joint action of the toxicants was indicated. Effects on survival showed that the toxicity of cadmium and zinc mixtures was little if any greater than the toxicity of zinc alone. Mechanisms of zinc toxicity in this test were similar to those in previous chronic tests of individual metals, indicating that the presence of cadmium did not influence the mode of action of zinc. Comparisons between metal residues in fish exposed to each individual metal or to the metal mixtures showed that the uptake of one metal was not influenced by the presence of the other.

Prediction of bioaccumulation of metals from contaminated sediments by the oligochaete, lumbriculus variegatus

Abstract Short-term tests with benthic species have shown that certain cationic metals (cadmium, nickel, lead, zinc, copper) in sediments are not bioavailable when acid volatile sulfide (AVS) concentrations are sufficient to bind the metals, and/or when concentrations of metals in the sediment pore water are small. It was uncertain, however, whether a similar lack of bioavailability could be predicted when evaluating metal bioaccumulation in long-term exposures. In this study, we exposed the oligochaete Lumbriculus variegatus to sediments from the lower Fox River, Wisconsin, which contained elevated concentrations of metals. Based on solid-phase metal and AVS measurements, or pore water metal concentrations, metals in the sediments were predicted to be of minimal biological availability. After a 30 day exposure to the test sediments, L. variegatus contained concentrations of metals not significantly greater than those in control oligochaetes exposed only to Lake Superior water. This indicates that metal bioavailability models based on sediment AVS content and/or pore water concentrations may be valid for long-term as well as short-term exposures of benthic species.

Comparison of the relative sensitivity of three benthic invertebrates to copper-contaminated sediments from the Keweenaw Waterway

The Keweenaw Peninsula in northern Michigan was once a major copper mining area and these mining activities were responsible for depositing tons of tailings in and around the Keweenaw Waterway. In recent years there has been concern about possible toxic effects of the contaminated sediments on aquatic communities in the system. In the fall of 1990, sediments were collected from various locations along the Waterway. Ten-day tests were conducted with the samples using three species of benthic invertebrates that have been proposed as suitable for evaluating the toxicity of freshwater sediments: Hyalella azteca (amphipods), Chironomus tentans (chironomids) and Lumbriculus variegatus(oligochaetes). A number of sediments were toxic to one or more of the three species and, in general, there was good agreement among the tests with regard to identifying toxic samples. Unexpectedly, the relative sensitivity of the three species to the test sediments was not accurately predicted from water-only copper exposures. This indicates that factors modifying exposure, such as different lifestyles and/or varying sensitivity to physico-chemical characteristics of sediments can influence results of sediment toxicity tests.

Acute and long-term effects of nine chemicals on the Japanese medaka (Oryzias latipes)

Ninety-six-hour acute and 28-day larval survival and growth tests were conducted with nine organic chemicals, using the Japanese medaka (Oryzias latipes) as the test organism. The nine tested chemicals were allyl isothiocyanate, aniline, benzyl acetate, 4-chloroaniline, 2-chloroethanol, 2,4-diaminotoluene, 1,2-dibromoethane, 2,4-dichlorophenoxyacetic acid (2,4-D), and phenol. The derived 96-h LC50 values for medaka for all chemicals ranged from 0.077 mg/L for allyl isothiocyanate to 2,780 mg/L for 2,4-D. The chronic values for six of the nine chemicals tested ranged from 0.013 mg/L for allyl isothiocyanate to 42.5 mg/L for 2,4-D. Acute-to-chronic ratios for these six chemicals ranged from 1.4 for 2-chloroethanol to 70.9 for 2,4-D. Growth of medaka was significantly reduced in the lowest exposure concentration during 28-day larval tests with aniline, 4-chloroaniline, and 2,4-diaminotoluene. The estimated maximum acceptable toxicant concentration was reported as less than the lowest exposure concentration of 4.6, 2.2 and 40.3 mg/L for tests with aniline, 4-chloroaniline and 2,4-diaminotoluene, respectively. Chronic values for 2-chloroethanol and medaka were 12.6 mg/L during an embryo-larval test and 22.1 mg/L during the 28-day larval test.

Polychlorinated chemical residues in fish from major watersheds near the Great Lakes, 1979

Abstract Over 50 non-PCB polyhalogenated organic chemicals have been identified by GC/MS in fish from the Great Lakes and other major watersheds near the Great Lakes. p,p′-DDE, hexachlorobenzene, and components of tech-chlordane were the most frequently found chemicals. Also described are advances in sample preparation methodology which allow the identification of many frequently occuring unusual chemicals. Several chemicals not previously reported in environmental samples are identified.

Horizon-specific oxidation of acid volatile sulfide in relation to the toxicity of cadmium spiked into a freshwater sediment

The effects of oxidative processes on acid volatile sulfide (AVS) concentrations in various horizons of whole sediment cores were evaluated in relation to the toxicity of a metal (cadmium). An artificial system was used to “age” cadmium-spiked sediment samples under a constant flow of fresh Lake Superior water. Sediments from Pequaywan Lake, Minnesota (12 μmol AVS/g) were spiked to achieve (nominal) cadmium: AVS molar ratios of 0.02 (control), 0.2, 0.8, 1.2, and 3.0. At 0, 24, and 48 days post-spiking, sediment cores were removed from the aging system and tested for toxicity to the amphipod Hyalella azteca. At the same time, horizons from replicate sediment cores were prepared for analysis by freezing, and then cutting them into 10–20 mm increments. The sediment horizons were analyzed for AVS and simultaneously extracted cadmium concentrations, and pore water concentrations of cadmium. Relatively little oxidation of surficial AVS concentrations was observed, even at aging times up to 48 d. By 48 d, pore water concentrations of cadmium were slightly elevated at all spiking concentrations, but were increased greatly at cadmium:AVS ratios greater than one. Hyalella azteca mortality was generally predictable based on surficial cadmium:AVS ratios or pore water cadmium concentrations.