No abstract

Fathead minnows (Pimephales promelas) and oligochaetes (Lumbriculus variegatus) were exposed in the laboratory to sediment samples from the lower Fox River/Green Bay, and their bioaccumulation of PCBs was compared with PCB concentrations in synoptic collections of fish (black bullhead, Ameiurus melas) and oligochaetes (primarily Limnodrilus sp.) from the field. Total PCBs and PCB homologues (expressed as lipid-normalized tissue concentrations/organic carbon-normalized sediment concentrations) were qualitatively and quantitatively similar in the laboratory-exposed and field-collected oligochaetes. PCB concentrations in A. melas generally were greater than in any of the other test species, due possibly to differences in exposure (e.g. biomagnification) compared with the other organisms. PCB concentrations in P. promelas were consistently smaller than in any of the other species investigated. These results indicate that, under the exposure regime used in this study, laboratory tests with L. variegatus can provide a reasonable quantitative estimate of the bioaccumulation of PCBs in field populations of oligochaetes. However, the use of P. promelas in laboratory sediment tests may result in significant underprediction of the exposure of indigenous benthic invertebrates and fishes to bioaccumulable contaminants.

Abstract-This study determined the relative sensitivity of five species of aquatic macrophytes and six species of algae to four commonly used herbicides (atrazine, metribuzin, alachlor, and metolachlor). Toxicity tests consisted of 96-h (duckweed and algae) or 14-d (submerged macrophytes) static exposures. The triazine herbicides (atrazine and metribuzin) were significantly more toxic to aquatic plants than were the acetanilide herbicides (alachlor and metolachlor). Toxicity studies ranked metribuzin Ͼ atrazine Ͼ alachlor Ͼ metolachlor in decreasing order of overall toxicity to aquatic plants. Relative sensitivities of macrophytes to these herbicides decreased in the order of Ceratophyllum Ͼ Najas Ͼ Elodea Ͼ Lemna Ͼ Myriophyllum. Relative sensitivities of algae to herbicides decreased in the order of Selenastrum Ͼ Chlorella Ͼ Chlamydomonas Ͼ Microcystis Ͼ Scenedesmus Ͼ Anabaena. Algae and macrophytes were of similar overall sensitivities to herbicides. Data indicated that Selenastrum, a commonly tested green alga, was generally more sensitive compared to other plant species. Lemna minor, a commonly tested floating vascular plant, was of intermediate sensitivity, and was fivefold less sensitive than Ceratophyllum, which was the most sensitive species tested. The results indicated that no species was consistently most sensitive, and that a suite of aquatic plant test species may be needed to perform accurate risk assessments of herbicides.

Aquatic plant toxicity tests are frequently conducted in environmental risk assessments to determine the potential impacts of contaminants on primary producers. An examination of published plant toxicity data demonstrates that wide differences in sensitivity can occur across phylogenetic groups of plants. Yet relatively few studies have been conducted with the specific intent to compare the relative sensitivity of various aquatic plant species to contaminants. We compared the relative sensitivity of the algae Selenastrum capricornutum and the floating vascular plant Lemna minor to 16 herbicides (atrazine, metribuzin, simazine, cyanazine, alachlor, metolachlor, chlorsulfuron, metsulfuron, triallate, EPTC, trifluralin, diquat, paraquat, dicamba, bromoxynil, and 2,4-D). The herbicides studied represented nine chemical classes and several modes of action and were chosen to represent major current uses in the United States. Both plant species were generally sensitive to the triazines (atrazine, metribuzin, simazine, and cyanazine), sulfonureas (metsulfuron and chlorsulfuron), pyridines (diquat and paraquat), dinitroaniline (trifluralin), and acetanilide (alachlor and metolachlor) herbicides. Neither plant species was uniformly more sensitive than the other across the broad range of herbicides tested. Lemna was more sensitive to the sulfonureas (metsulfuron and chlorsulfuron) and the pyridines (diquat and paraquat) than Selenastrum. However Selenastrum was more sensitive than Lemna to one of two thiocarbamates (triallate) and one of the triazines (cyanazine). Neither species was sensitive to selective broadleaf herbicides including bromoxynil, EPTC, dicamba, or 2,4-D. Results were not always predictable in spite of obvious differences in herbicide modes of action and plant phylogeny. Major departures in sensitivity ofSelenastrum occurred between chemicals within individual classes of the triazine, acetanilide, and thiocarbamate herbicides. Results indicate that neither species is predictively most sensitive, and that a number of species including a dicot species such as Myriophyllum are needed to perform accurate risk assessments of herbicides.

The objective of this study was to determine if the acid‐volatile sulfide (AVS) content of freshwater sediments was important in limiting the bioavailability and toxicity of cadmium. Five different concentrations of cadmium were spiked into sediments with three different AVS concentrations, and 10‐d exposures with the oligochaete Lumbriculus variegatus and the snail Helisoma sp. were conducted. Concurrent water‐only cadmium exposures were also conducted. When the cadmium‐to‐AVS ratios were ≤1, toxicity was not observed. At ratios ≤1, mean whole‐body cadmium residue concentrations of organisms were approximately equal to or less than the maximum residues obtained in survivors of the cadmium exposures in water only. These results corroborated the results of a previous experiment conducted with saltwater sediments and indicate that metal/AVS relationships could be used to establish numeric sediment quality criteria for use in the protection of aquatic life.