Michael L. Knuth

Water Quality in Great Lakes Coastal Wetlands: Basin-wide Patterns and Responses to an Anthropogenic Disturbance Gradient

ABSTRACT We present water quality data from 58 coastal wetlands, sampled as part of a larger effort investigating effects of nutrient enrichment and habitat disruption in the Laurentian Great Lakes. Our sampling design selected sites from across a gradient of agricultural intensity within combinations of biogeographic ecoprovince and wetland hydromorphic type and captured a large range in water quality. Levels of total nutrients (N and P), and various measures of particulate concentration, water clarity, and ionic strength were strongly associated with agricultural intensity in the watershed, and could be effectively aggregated into an overall principal component-based water quality descriptor. Lake Erie wetlands had the highest nutrient levels and lowest water clarity, while wetlands in Lakes Superior and Huron had the lowest nutrient levels and clearest water. Lake Ontario wetlands had clearer water than would be expected from their nutrient levels and position on the agricultural intensity gradient. Dissolved oxygen, silica, pH, and dissolved organic carbon (DOC) were independent of agricultural intensity but DOC was responsible for low water clarity in some Lake Superior wetlands. Simple classification by hydromorphic type (riverine or protected) did not explain water quality differences among wetlands exposed to similar agricultural intensity levels, so finer hydrologic classification may be desirable. Results are used as a basis for discussing research and information needs underlying development of water quality criteria and monitoring programs for coastal wetlands of the Great Lakes.

The acute toxicity of selected substituted phenols, benzenes and benzoic acid esters to fathead minnows Pimephales promelas

Abstract Flow-through acute toxicity tests were conducted with 24 organic compounds using fathead minnows Pimephales promelas as test organisms. The tested toxicants consisted of 11 substituted phenols, four substituted benzenes and nine esters. The 96-h LC 50 values determined for these compounds when tested against fathead minnows ranged from 0·135 mg litre −1 for nonylphenol to 117 mg litre −1 for nitrobenzene. Adverse sublethal effects were observed in fathead minnows at exposure concentrations below the 96-h LC 50 value with 14 of the 24 compounds tested. Acute toxicity tests were also conducted with 2,3,4,5-tetrachlorophenol using rainbow trout Salmo gairdneri ; with 1,4-dinitrobenzene, 2-ethoxyethylacetate, ethyl salicylate and phenyl salicylate using both channel catfish Ictalurus punctatus and snails Aplexa hypnorum ; and with 4-nitrophenol using channel catfish. The 96-h LC 50 for rainbow trout when tested against 2,3,4,5-tetrachlorophenol was 0·205 mg litre −1 , while 96-h LC 50 values for channel catfish ranged from 0·673 to 44·8 mg litre −1 with 1,4-dinitrobenzene and 2-ethoxyethylacetate, respectively. Snail 96-h LC 50 values ranged from 4·24 mg litre −1 for 1,4-dinitrobenzene to 65·2 mg litre −1 for 2-ethoxyethylacetate.

Acute and chronic toxicity of triphenyltin hydroxide to fathead minnows (Pimephales promelas) following brief or continuous exposure.

Fathead minnow larvae (Pimephales promelas) were exposed to triphenyltin hydroxide (TPTH) during brief (single pulse) or continuous exposure in 96-h and 30-day toxicity tests. The continuous exposure 96-h LC(50) value was 7.1 microg litre(-1). Brief exposures for 12 to 72-h gave 96-h LC(50) values that ranged from 61.8 to 6.0 microg litre(-1), respectively. The continuous exposure 30-day chronic effect concentration, based upon reduced growth, was 0.23 microg litre. Survival was significantly reduced at 2.0 microg litre(-1). Brief exposures for 24, 48, and 72-h in 30-day tests significantly reduced survival and growth at 13.0, 13.0 and 60.0 microg litre(-1) respectively. It is suggested that both toxicant concentration and exposure duration are important factors to consider in the risk assessment of potential pesticide hazards in the environment.

Bromacil and diuron herbicides: toxicity, uptake, and elimination in freshwater fish.

Fathead minnows, 30 days old, were exposed to technical grade bromacil and diuron in flow-through tests to determine acute toxicity. LC50 values for bromacil were 185, 183, 182 and 167 mg/L at 24, 48, 96, and 168 hr, respectively; and for diuron, 23.3, 19.9, 14.2, and 7.7 mg/L at 24, 48, 96, and 192 hr, respectively. Eggs, newly hatched fry, and juvenile fish were continuously exposed to lower concentrations of the herbicides for 64 days. Growth was significantly reduced (p ⩽ 0.01) at the lowest bromacil exposure of 1.0 mg/L. Therefore, it was not possible to determine a “no effect” concentration. The “no effect” concentration for diuron was 33.4 μg/L, while the lowest concentration which resulted in adverse effects was 78.0 μg/L. Adverse effects at 78.0 μg/L were an increased incidence of abnormal or dead fry immediately after hatch (p ⩽ 0.01) and decreased survival throughout the exposure period (p ⩽ 0.05). Neither herbicide accumulated significantly in fish tissue, as bioconcentration factors were <3.2 and 2.0 for bromacil and diuron, respectively. Rainbow trout (Salmo gairdneri) injected with radiolabeled bromacil or diuron eliminated over 90% of the radioactivity within 24 hr. Parent compound and metabolites were detected in the aquarium water in both cases. Metabolites of diuron recovered from the water included 3,4-dichloroaniline and several demethylated products.

Effects of esfenvalerate on the reproductive success of the bluegill sunfish, Lepomis macrochirus in littoral enclosures

Adult bluegills were exposed to the synthetic pyrethroid esfenvalerate, during a reproduction study conducted in six littoral enclosures located in a 2-ha pond near Duluth, Minnesota. Bluegill reproductive success was determined after two applications of esfenvalerate at nominal concentrations of 0.0, 0.01, 0.08, 0.20, 1.0, and 5.0 μg/L. Responses measured were adult behavior and spawning, embryo hatchability, larval survival until swim-up, young-of-the-year (Y-O-Y) growth, and total biomass. All adult bluegills died within one day following the first application at 5.0 μg/L. Successful spawning and resulting hatching of offspring were observed at all esfenvalerate concentrations except 5.0 μg/L. Following exposure at 1.0 μg/L, spawning was delayed for 15 days and few or no larvae survived. Bluegill Y-O-Y growth was reduced by 62, 57, and 86% in the 0.08, 0.20, and 1.0 μg/L esfenvalerate treated enclosures. Delayed adult spawning and reduced Y-O-Y growth may result in poor Y-O-Y overwinter survival which would result in a diminished or extirpated year class.

Toxicity of 3,4-dichloroaniline to fathead minnows, Pimephales promelas, in acute and early life-stage exposures.

1Center for Lake Superior Environmental Studies, University of Wisconsin-Superior, Superior, Wisconsin 54880 and 2Environmental Research Laboratory-Duluth, U.S. Environmental Protection Agency, Duluth, Minnesota 55804 3,4-Dichloroaniline (3,4-DCA) is a chemical which may enter surface waters as a contaminant in applications of agricultural herbicides, as a metabolite of several herbicides, or in industrial effluents from dye manufacturing plants. 3,4-DCA is an intermediate in the synthesis of certain urea and acylanilide herbicides, such as diuron, linuron, neburon, and propanil (DiMuccio et al. 1984). These herbicides are degraded to 3,4-DCA by microorganisms in the soil or water (Bartha and Pramer 1967; Deuel et al. 1977; Ei-Dib and Aly 1976).

Temporal Dynamics of Nutrients (N and P) and Hydrology in a Lake Superior Coastal Wetland

Abstract Coastal wetlands on Lake Superior are hydrologically complex ecosystems situated at the interface of upland catchments and the oligotrophic lake. Little is known about nutrient dynamics within coastal wetlands or their role in modifying or contributing to nutrient fluxes from watersheds to Lake Superior. We conducted an intensive study of Lost Creek Wetland (LCW) near Cornucopia, WI, with the objective of determining influences of temporal variability in hydrology on dynamics and retention of N and P. We measured hydrologic inputs and distributions of inorganic and organic forms of nitrogen and phosphorus within LCW under hydrologic conditions ranging from summer base flow to spring snow melt. Our study confirms that the interrelationship between hydrologic connections to lake and tributary and seasonal variations in hydrology can regulate internal nutrient dynamics of coastal wetlands. The strength of hydrologic linkage of LCW to Lake Superior and tributary varied greatly among seasons, resulting in shifts in the relative importance of these nutrient sources and influencing spatial distribution of nutrients within the wetland. Ratios of inorganic nitrogen and phosphorus in the wetland were consistently low (

Toxicity, bioconcentration, and metabolism of the herbicide propanil (3′,4′-dichloropropionanilide) in freshwater fish

Fathead minnows (Pimephales promelas) were exposed to technical grade propanil (3′,4′-dichloropropionanilide) in a flow-through diluter system to determine acute lethality. LC50 values were 11.5, 10.2, 8.6, and 3.4 mg·L−1 at 24, 48, 96, and 192 hr, respectively. Eggs, newly hatched fry, and juvenile fish of this species were similarly exposed but at lower concentrations and for a period of 58 days. The 58-day “no effect” concentration was between 0.4 and 0.6Μg·L−1, based upon the physiological parameters of length and dry weight of juvenile fish.14C-Propanil did not bioconcentrate significantly in fathead minnows (1.6× for parent propanil in whole body). Rainbow trout (Salmo gairdneri) readily metabolized propanil, forming at least ten products. One metabolite recovered from trout bile was identified as either 3′,4′-dichloro-2-hydroxypropionanilide or 3′,4′-dichloro-3-hydroxy-propionanilide. The technical grade propanil also contained 0.67 mg·g−1 of 3,3′,4,4′-tetrachloroazobenzene as a contaminant.

Comparative toxicity of methanol and N,N-dimethylformamide to freshwater fish and invertebrates.

The organic solvents methanol and N,N-dimethylformamide (DMF) are used widely as industrial solvents. Although some toxicity data appear in the literature for methanol and DMF, there have been few studies which have been flow-through tests for a standard 48- or 96-h exposure period with measured toxicant concentrations. In this study, 96-h flow-through acute toxicity tests with methanol and DMF were conducted with three species of freshwater fish - rainbow trout (Salmo gairdneri), bluegill (Lepomis macrochirus) and fathead minnow (Pimephales promelas). Static acute toxicity tests (48 h) were conducted with DMF and two species of freshwater invertebrates - a midge (Paratanytarsus parthenogeneticus) and a daphnid (Daphnia magna). Median lethal (LC50) and median effect (EC50) concentrations for 96-h exposures were determined for fish and 48-h EC50s were determined for invertebrates.

Acute toxicity of triphenyltin hydroxide to three cladoceran species.

The toxicity of an organotin pesticide, triphenyltin hydroxide, was assessed with several freshwater cladoceran species. Daphnia pulex, Daphnia magna, and Ceriodaphnia dubia were exposed for 48 h to triphenyltin hydroxide in static acute toxicity tests. Values of the 48-h trimmed Spearman-Karber EC(50)s for the three species were found to be 14.5, 16.5, and 11.3 microg litre(-1), respectively. Analysis of variance performed on EC(50) values of replicates revealed no significant differences between the three species. Methods were employed which decrease animal handling stress and increase the accuracy and precision of the concentrations.