Roger O. Hermanutz

Acidification effects on macroinvertebrates and fathead minnows (Pimephales promelas) in outdoor experimental channels

Abstract Three outdoor experimental channels at the U.S. EPA Monticello (Minnesota) Ecological Research Station were employed to assess in the field acidification effects on macroinvertebrate communities and populations of fathead minnows (Pimephales promelas). One channel served as ambient (pH 8), the second was acidified with sulfuric acid to pH 6 and the third to pH 5 for 17 weeks. Acidification did not markedly increase toxic metal concentrations in the channels; however, there was some evidence of possible mercury mobilization. Benthic macroinvertebrate densities were lower in the acidified channels during most of the study and final diversity indices were 2.1, 1.7 and 1.2 in the ambient, pH 6 and pH 5 channels, respectively. Drift of amphipods and leeches was stimulated in the pH 5 channel early in the study. The number of insect taxa and percentages emerging from the ambient, pH 6 and pH 5 channels, respectively, were 30 and 56%, 28 and 31%, and 18 and 13%. Macroinvertebrate tolerance to the acidification was classified as follows: damselflies, isopods and leeches most tolerant; chironomids, some amphipods (Crangonyx) and flatworms of intermediate tolerance; and other amphipods (Hyalella azteca) and snails (Physa gyrina) most sensitive. Fathead minnow spawning and embryo production were similar in the ambient and pH 6 channels with little spawning and no eyed-embryos found in the pH 5 channel. Newly-hatched larval fish did not survive to the juvenile stage in the pH 6 channel. Continued acidification would likely have further decreased the diversity of the macroinvertebrate community, increased relative abundance of more tolerant species, and caused extinction of the minnow population.

Transfer of toxic concentrations of selenium from parent to progeny in the fathead minnow (Pimephales promelas)

Selenium, an essential trace element, may become concentrated in aquatic ecosystems to levels that are toxic to fish. Finley (1985) and Gillespie and Baumann (1986) have shown that selenium in overflow water from coal burning power plant settling basins contributed to a decline in fish populations. The leaching of selenium from the soil into water systems used for irrigation in highly seleniferous areas of the country poses another serious problem. Studies demonstrated that female bluegill sunfish transfer selenium to their progeny. The objective of the study was to determine whether the selenium levels within fathead minnow embryos in a semi-natural ecosystem resulted from direct uptake by the embryos following spawning, from female-to-progeny transferral, or from some combination of these two occurrences.

Effects of diazinon on macroinvertebrates and insect emergence in outdoor experimental channels

Abstract Effects of diazinon on macroinvertebrates were assessed in three outdoor experimental channels from mid-May to mid-September, 1980. One channel served as a control and two channels as low and high treatments. Three dosing regimes were employed. The low and high treatment channels were continuously dosed for 12 wk to nominal concentrations of 0.3 and 3 μg/l, then increased to 6 and 12 μg/l for 4 wk, then the high treatment was increased to 30 μg/l with the low treatment channel returned to ambient. Diazinon concentrations did not reach the intended levels during the latter two dosing regimes. No consistent interchannel differences were observed in total macroinvertebrate abundance or in species diversity induces. Effects were noted at the lowest concentration for amphipods and insects. As diazinon concentrations were increased interchannel community structure changes became more pronounced. Elevated drift, especially amphipods and snails, occurred in the treated channels 4 wk after dosing began and following the increases in concentrations. Total numbers and species of insects emerging from the three channels were not greatly different but lower numbers of mayflies and damselflies emerged from the treated channels. Tolerance of macroinvertebrates to diazinon were as follows: flatworms, physid snails, isopods and chironomids most tolerant; leeches and the amphipod Crangonyx less tolerant; the amphipod Hyalella, mayflies, caddisflies and damselflies sensitive.

Oocyte atresia and reproductive success in fathead minnows (Pimephales promelas) exposed to acidified hardwater environments

The ovarian histology of fathead minnows (Pimephales promelas) chronically exposed to three levels of environmental pH was examined for evidence of reproductive impairment. Exposures occurred in three experimental runningwater channels receiving Mississippi River water. One of these channels was not acidified and two were dosed with H2SO4. The pH was approximately 8 in untreated river water and 6 and 5 in the two channels receiving H2SO4. Fish for ovarian examination were taken from these channels at four stages of the reproductive season: initiation of spawning (June 19), mid-spawning (July 12), end of spawning (August 14–15), and approximately 1 mo. post-spawning (September 19).The fish exhibited ovarian histological changes and depression of reproductive success which were directly associated with the level of environmental stress experienced. The association between these three factors was most consistent and pronounced if the fish were sampled near the end of the spawning season. When sampled at this time, reproductive impairment in a population was found when the ratio of the volume of atretic (resorbing) oocytes present in the ovary to the total ovarian volume exceeded 20% in all fish sampled. This was the case in the pH 5 channel fish sampled in August. At this same time, not all of the fish in the pH 6 channel exhibited such an accumulation of atretic oocytes, and egg deposition in that population was not reduced. None of the fish from the pH 8 channel were so affected nor was their reproduction.

Effects of pentachlorophenol on invertebrates and fish in outdoor experimental channels

Abstract Pentachlorophenol (PCP) was selected to assess the applicability of a toxicant criterion concentration for protecting aquatic communities in outdoor experimental channels. The criterion concentration was derived from on site laboratory bioassays. In 1982 three channels were continuously dosed with PCP for 12 wk at nominal concentrations of 48 μg/l (low, criterion level), 144 μg/l (medium, 3 × criterion) and 432 μg/l (high, 9 × criterion). In 1983 the low and medium treatments were repeated for 12 wk. Each year an untreated channel served as control. Invertebrate responses measured were changes in density, community composition and drift; fish responses were changes in survival, growth, reproduction and larval drift. Some ecosystem effects were detected at all treatment levels with fish being the most sensitive animals. Microinvertebrate densities were lower in the medium PCP channel than the control. Survival of the snail Physa gyrina was substantially reduced in the high treatment channel; no other macroinvertebrates were adversely affected by the toxicant. All fathead minnows and bluegill sunfish stocked in the high treatment channel died within the first 8 days of dosing. Fish survival was similar in all remaining channels. Fish growth and larval drift were lower in the treated channels than in the control channels and spawning was reduced in the medium dose channels. The numbers of fathead minnows collected both years from the medium dose channels were lower than the criterion and control channels. Highest numbers of bluegills were recovered from the control channels. The study indicated that the criterion concentration derived from laboratory tests did not fully protect the animals in the experimental channels.

Endrin and malathion toxicity to flagfish (Jordanella floridae).

Endrin and malathion effects on survival, growth, and reproduction of flagfish were determined in a flow-through system. Endrin chronic effects on first-generation growth and reproduction occurred only at 0.3μg/L, the highest concentration tested. The mean endrin residues in the first-generation fish at 65 days were about 15,000 times the water concentration in all concentrations tested. Malathion concentrations of 31.5μg/L and 24.7μg/ L, the highest concentrations tested, had detrimental effects on first-generation survival. During the same period malathion concentrations as low as 10.9μg/L significantly affected growth. Neither insecticide, at the concentrations tested, had any detectable effects on the second generation during a 30-day exposure period.Acute toxicities to juvenile fish were also determined in the same flow-through system. The 96-hr LC50s were 0.85μg/L for endrin and 349μg/L for malathion.

Ammonia effects on microinvertebrates and fish in outdoor experimental streams

Laboratory data on ammonia effects, the US EPA national water quality criteria for ammonia, and ammonia site-specific criteria were evaluated in four outdoor experimental streams (one control and three treatment streams) over a 76-week period. Calculated un-ionised ammonia concentrations varied daily and seasonally according to pH and temperature changes. Populations of four major microinvertebrate taxonomic groups (cladocerans, copepods, rotifers and protozoans) were monitored during a 4-week period early in the study, and six fish species (fathead minnows, bluegills, channel catfish, white suckers, walleyes, and rainbow trout) were tested for various time intervals, from 4 to 26 weeks, throughout the 76-week study period. Copepods and rotifers were unaffected in all three treatment streams, based on comparisons with the control stream. Cladoceran and protozoan populations were reduced in at least two treatment streams, but because of large variability, effects were considered to be inconclusive. However, complete mortality of cladocerans did occur in the high and medium treatments when placed in in situ biomonitor chambers. All six fish species were affected in one or more treatments. Generally, the fish effect values agreed with most laboratory effect values. Of 12 fish groups tested, one channel catfish group and one white sucker group were affected below the recommended protection levels of the national and site-specific criteria. The lowest effect concentrations tested for the other ten groups occurred above the criteria levels.

Toxicity of endrin and malathion mixtures to flagfish (Jordanella floridae).

Individual endrin and malathion concentrations and mixtures of the concentrations were tested concurrently with flagfish in both chronic and acute exposures. The joint action of mixtures on mortality in chronic exposures consisted of enhanced effects at the higher concentrations not causing death when the pesticides were tested individually. Chronic effects of mixtures on growth followed a simple additive effects model. Malathion did not alter the endrin effects on egg production, and in a separate test it did not affect the uptake or elimination of endrin. Joint action on mortality in acute exposures occurred at 48 and 72 hr but not at 10 and 24 hr.