Vincent R. Mattson

Relative Sensitivity of Three Freshwater Benthic Macroinvertebrates to Ten Contaminants

The objective of this study was to determine the suitability of Hyalella azteca, Chironomus tentans and Lumbriculus variegatus as representative species for the assessment of sediment toxicity. Ten chemicals were tested at the U.S. EPA Environmental Research Laboratory-Duluth, always using H. azteca and C. tentans and, occasionally, L. variegatus. The exposures were water-only, flow-through tests with measured chemical concentrations, which were conducted for 10 days in Lake Superior water. Chemicals tested included five metals (copper, lead, zinc, nickel, cadmium) and five pesticides (chlorpyrifos, dieldrin, p,p′-DDD, p,p′-DDE, p,p′-DDT). The amphipod was quite sensitive to the metals, while the midge often was exceptionally sensitive to the pesticides. No one of the three species was most (or least) sensitive to the toxicants. Toxicity of the contaminants to the three species was compared to the genus mean acute and chronic data found in U.S. EPA Water Quality Criteria (WQC) documents, as well as information from the AQUIRE database. The results of these comparisons indicated that the three species reasonably represent the range of sensitivities of other aquatic test species, and occasionally are among the most sensitive species when compared to others in the WQC database.

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.

Effects of light intensity on the phototoxicity of fluoranthene to a benthic macroinvertebrate.

Conceptual models suggest that the toxicity of photoactivated polycyclic aromatic hydrocarbons (PAHs) should be a direct function both of chemical (PAH) dose and intensity of the ultraviolet (UV) light to which the organism is exposed. However, there have been only limited studies with aquatic organisms to quantify the relationship between PAH dose and UV intensity in producing phototoxicity. In this study, oligochaetes (Lumbriculus variegatus) were exposed, via the water, to multiple concentrations of fluoranthene, a PAH known to be phototoxic, and then placed under UV light at three different intensities. The resultant phototoxicity clearly was a function both of PAH dose and light intensity. Time-dependent mortality of the oligochaetes could be accurately predicted through evaluation of the product of fluoranthene dose (in the tissue of the animal) and light intensity to which the organisms were exposed. These results indicate that criteria for phototoxic chemicals should incorporate consideration not only of xenobiotic exposure but also of light intensity in specific aquatic environments.

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.

Evaluation of models for predicting the phototoxic potency of polycyclic aromatic hydrocarbons

Abstract The objective of this study was to evaluate the validity of two previously developed models to predict: (a) the relative phototoxic potency of polycyclic aromatic hydrocarbons (PAHs) through structure activity relationships (SARs), and (b) the interactive effects of variable light intensity and PAH dose on phototoxicity. The oligochaete Lumbriculus variegatus was exposed to multiple concentrations of the PAHs anthracene, pyrene, fluorene and fluoranthene for 96 h, followed by a 96 h holding period in clean water at three different ultraviolet (UV) light intensities. Based upon measured tissue residue concentrations, anthracene and pyrene were approximately equitoxic, and both were four-fold more potent than fluoranthene. Fluorene was not phototoxic to the oligochaete. These results were in good quantitative agreement with the toxicity predictions of the SAR model. Time-dependent lethality of the three phototoxic PAHs to the oligochaete was accurately modeled by plotting mortality as a function of the product of initial tissue residue of the PAH and UV light intensity to which the organisms were exposed, which also was in good agreement with the interactive toxicity model. These studies contribute to the technical basis for developing an integrated modeling approach to predicting the ecological risk of mixtures of phototoxic PAHs.

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.

Use of the oligochaete, Lumbriculus variegatus, as a prey organism for toxicant exposure of fish through the diet

The oligochaete, Lumbriculus variegatus, has several characteristics that make it desirable as a prey organism for conducting dietary exposure studies with fish. We conducted 21- and 30-d experiments with young fathead minnows (Pimephales promelas) and rainbow trout (Oncorhynchus mykiss), respectively, to determine whether a diet consisting solely of L. variegatus would support normal growth and to compare performance with standard diets (Artemia nauplii, frozen brine shrimp, or trout chow). All diets were readily accepted, and fish survived and grew well. Food conversion in both fathead minnows and rainbow trout was as high as or higher for the oligochaete diet compared with others, although this comparison is influenced by differences in ration, ingestion rate, or both. The oligochaete diet had gross nutritional analysis similar to the other diets, and meets fish nutrition guidelines for protein and essential amino acids. Methodologies and practical considerations for successfully using oligochaetes as an experimental diet are discussed. Considering their ready acceptance by fish, their apparent nutritional sufficiency, the ease of culturing large numbers, and the ease with which they can be loaded with exogenous chemicals, we believe that L. variegatus represents an excellent choice of exposure vector for exposing fish to toxicants via the diet.

Photoactivated polycyclic aromatic hydrocarbon toxicity in medaka (Oryzias latipes) embryos: Relevance to environmental risk in contaminated sites

The hazard for photoactivated toxicity of polycyclic aromatic hydrocarbons (PAHs) has been clearly demonstrated; however, to our knowledge, the risk in contaminated systems has not been characterized. To address this question, a median lethal dose (LD50) for fluoranthene photoactivated toxicity in medaka (Orvzias latipes) embryos was determined experimentally and then compared with ultraviolet-A (UV-A; 320-400 nm) radiation exposures in a PAH-contaminated field site. The dose metric, J/cm2/ microg fluoranthene/g egg wet weight, provided the means to estimate risk as the depth where the LD50 level would be exceeded at realistic field PAH concentrations, based on estimates of UV-A exposure. The estimates were made using 30 years of solar radiation data for Duluth (MN, USA) and measurements of water-column UV-A transmittance in a PAH-contaminated field site. Medaka embryo failure was strongly related to tissue PAH concentration and UV-A exposure. The LD50 was estimated to be 12.64 J/cm2/ microg fluoranthene/g egg wet weight; the 95% confidence interval was 8.46 to 19.7 J/cm2/microg fluoranthene/g egg wet weight. Embryo failures were characterized by undifferentiated cell proliferation that occurred very early in development. No partial effects or embryo/larval malformations were observed. Estimates of the depth at which the LD50 would be exceeded in the contaminated field site ranged from 10.7 cm (clear-sky conditions and lowest attenuation) to 0.0 cm (cloudy conditions and highest attenuation). Similar calculations were done using water-column attenuation estimates from 12 sites across the Great Lakes (USA). For these, the depths at which the LD50 would be exceeded ranged from 0.00 to 271.6 cm under the conditions described above. These results suggest that PAH phototoxicity may be a risk factor in specific contaminated sites, and they provide a framework for assessing that risk.

Photoactivated toxicity in amphipods collected from polycyclic aromatic hydrocarbon-contaminated sites

The risk of photoactivated PAH toxicity in contaminated aquatic systems has not been well characterized. To document risk, amphipods (Gammarus spp.) were collected from two polycyclic aromatic hydrocarbon (PAH)-contaminated sites in the lower St. Louis River and Duluth Harbor, USA (Hog Island and USX) as well as a reference site (Chipmunk Cove) and were exposed in two separate, replicate tests to controlled intensities of solar radiation for 3 d. Contaminated site organisms died significantly faster compared to control site organisms. In all tests, mortality was strongly related to ultraviolet-A (UV-A; 320-400 nm) dose. Ultraviolet-B (280-320 nm) radiation did not increase mortality. To compare susceptibility among populations, regressions of arcsine-transformed, proportionate mortality versus UV dose were completed for each, and the slopes were statistically compared. Response slopes for the two contaminated site populations were both significantly greater than the reference site population (p = 0.0001 for test 1; p = 0.0002 for test 2). These results indicate that organisms residing in PAH-contaminated environments can accumulate PAH concentrations sufficient to be at risk for photoactivated toxicity. Although amphipods are not typically at risk of PAH-photoactivated toxicity because they are largely protected from exposure to sunlight, they are representative surrogates for species that may be similarly protected at some life stages (and thus able to accumulate significant PAH tissue concentrations) but not at others.