Florence L. Harrison

The bioavailability of sediment-sorbed organic chemicals: A review

Xenobiotic chemicals that are present in aquatic environments are typically concentrated on suspended particles and sedimentary materials where they represent a source of chronic contamination to benthic and pelagic organisms. Laboratory and field studies of bioaccumulation, toxicity, and food-chain transfer of chemicals bound to sediment have shown the potential ecological impacts that may result from the contamination of sediments. In this review, the chemical and physical processes that determine the environmental fate of sediment-sorbed organic chemicals are outlined, and their relationship to bioavailability is discussed. Methods currently used to predict the fate of pollutants in the aquatic environment are of limited use for the assessment of sediment-sorbed chemical bioavailability because they are based on the compounds behavior in the water column. Furthermore, an organisms morphology and ecological niche can profoundly affect its ability to accumulate xenobiotic chemicals from sediments and these must be considered before the populations at greatest risk can be identified.

The toxicity of copper to the adult and early life stages of the freshwater clam,Corbicula manilensis

The copper sensitivity of adult and larval stages of the freshwater clamCorbicula manilensis was evaluated. In addition, copper concentrations were determined in adult clams exposed for 4 to 10 weeks to copper in a high-volume, flow-through bioassay. All bioassay systems utilized water that was low in total hardness and alkalinity.The response of the clams to copper depended on life stage. Copper sensitivity of larvae decreased markedly in successive developmental stages. LC5024s of veliger and juvenile larvae were 28 and 600 μg Cu/L, respectively. The mortality of trochophore larvae exposed to 10 μg Cu/L for one hr was 91.5%. The sensitivity to copper decreased with increased amounts of larval shell deposition.Adult clams were resistant to copper; the LC5096 was greater than 2,600 μg Cu/L. By comparison, the incipient lethal concentration (ILC, was lowless than 10 μg Cu/L. Adult clams accumulated more copper as concentrations in the water increased. Evidence was obtained for copper loss near or at death.Labile and total copper, as well as the coppercomplexing capacity, in the bioassay water were determined; the majority of copper was present as labile species. Toxicity was related to the quantities of labile copper in the water.

An in vivo sister-chromatid exchange assay in the larvae of the mussel Mytilus edulis: response to 3 mutagens.

An in vivo sister-chromatid exchange (SCE) assay using the larvae of the mussel Mytilus edulis was developed. Larvae were exposed to mutagens beginning 12 h after fertilization and harvested 12 h later in the late trochophore stage. Dose responses to the mutagens bromodeoxyuridine, mitomycin C and methyl methanesulfonate were linear. The sensitivity of the SCE response of mussel larvae to these mutagens compares favorably with that of other systems and indicates this assay to be valuable in marine genetic toxicological monitoring.

The influence of organic chelators on the toxicity of copper to embryos of the pacific oyster,Crassostrea gigas

The effects of copper on the development ofCrassostrea gigas embryos were determined with a 48-hr static bioassay. In filtered, sterilized seawater from Bodega Bay, California, the LC100 was 20μg Cu/L, and the LC50 was 12μg Cu/L. Destruction of the naturally occurring dissolved organic material in the culture water by UV oxidation decreased embryo survival at 10μg Cu/L.The addition to seawater of five organic chelators (ethylenediaminetetraacetic acid (EDTA), sodium citrate, glycine, and oxalate at 1×10−6 M, and humic matter at 2 mg/L) increased embryo survival. EDTA and humic matter were the most effective chelators; EDTA significantly increased survival at 100μg Cu/L and humic matter did so at 40μg Cu/L. The ability of a chelator to increase survival was related to the stability constant of the copper-chelator complex.

The bioavailability of sediment-sorbed chlorobenzenes to larvae of the midge, Chironomus decorus

Larval stages of the midge, Chironomus decorus, were used to define the bioaccumulation of sediment-sorbed mono-, di-, tri-, and hexachlorobenzene. Larvae were exposed to high- and low-organic-content sediments that had been equilibrated with individual radiolabeled chlorobenzenes prior to testing. Equilibrium or nonequilibrium aqueous concentrations of the volatile test chemicals were flowed through sealed chambers in a sediment-water exposure system. The uptake of chlorobenzenes by midge larvae was rapid for all compounds tested, and apparent steady-state conditions were reached within 48 hr of exposure. Bioconcentration factors for the accumulation of chlorobenzenes from sediments and from interstitial and overlying waters were related to the octanol/water partition coefficients of the compounds. Because the diffusion of chlorobenzenes to overlying water during nonequilibrium flow through conditions was very slow, bioaccumulation was dependent on the concentration of the chemicals in interstitial water. These results show how benthic organisms may be able to accumulate significant levels of chlorinated aromatic compounds from ecosystems where their concentrations in the water column are relatively low.

Cytogenetic evidence of inducible processes linked with metabolism of a xenobiotic chemical in adult and larval Mytilus edulis

Abstract Sister chromatid exchange (SCE), a sensitive cytogenetic endpoint for measuring the effects of mutagens on chromosomes, was assayed in vivo in adult and larval mussels to determine whether these different life-history stages possess any capability for converting promutagens to mutagenic species. Cyclophosphamide (CPA), a water-soluble promutagen that is dependent for its mutagenic activity in mammals on transformations accomplished via the cytochrome P-450 pathway, was selected for this investigation. CPA was found to cause increased frequencies of SCE in both adult and larval M. edulis . In addition, the presence of phenobarbital (PB), an inducer of the microsomal detoxication system in mammals, was found to increase the levels of SCE produced by CPA, indicating that the effect of PB may have been to increase the rate at which CPA was metabolized. Operating as it does at the level of the individual cell nucleus, SCE is thus shown to have potential as an extremely sensitive indicator of stimulation of the microsomal detoxication system in the common mussel. The apparent inducibility of this activity may have important consequences for these organisms when they are exposed to the complex mixtures of xenobiotic chemicals found in the environment.

Effects of acute irradiation on reproductive success of the polychaete worm, Neanthes arenaceodentata.

Effects of acute irradiation on the reproductive success of a relatively low-fecundity species were investigated by exposing pairs of female and male polychaete worms (Neanthes arenaceodentata) to either no radiation (controls) or 0.5, 1.0, 2.0, 5.0, 10 or 50 Gy of acute irradiation (5 Gy min-1) at the time when oocytes were visible in the female. The broods from the pairs were sacrificed before hatching occurred, and information was obtained on the number in the brood, the number of normal and abnormal embryos, and the number of embryos that were living, dying and dead. Developing gametes of N. arenaceodentata appeared to be sensitive to acute irradiation. There was a significant reduction in the percentage of live embryos in the broods from pairs receiving doses as low as 0.5 Gy, which is lower than the lowest dose at which effects in invertebrates have been reported previously. This was most likely due to the induction of lethal mutations in the developing gametes, which affected the survival of embryos in early stages of life. Except for those pairs receiving 10 or 50 Gy, there was no evidence of decreased fertility or fecundity or of reduced fertilization success; the number of embryos in the broods from only these irradiated groups was significantly different from the controls.

Sublethal responses of Mytilus edulis to increased dissolved copper

Abstract Changes in the composition of copper-binding proteins and in the latency of lysosomal enzymes were detected in digestive gland cells of Mytilus edulis exposed to metals. Chronic exposure to copper resulted in concentrations of copper in low-molecular weight metallothionein-like proteins that were dependent on exposure concentration and time, and in a dose-dependent reduction in the latency of lysosomal hexosaminidase activity. A direct relationship between the copper concentration associated with the high molecular weight proteins and the mortality of mussels was observed.

Comparison of cellular and whole-animal bioassays for estimation of radiation effects in the polychaete wormNeanthes arenaceodentata (Polychaeta)

The polychaete wormNeanthes arenaceodentata was used in experiments to determine possible relationships between short-term genotoxicity tests and reproductive and lethal consequences of exposure to ionizing radiation. Groups of juvenileN. arenaceodentata received one of four different radiation doses (2, 4, 8, and 16 Gy) to determine dose-effect estimates for chromosomal aberration induction, and groups of both adult and juveniles received one of seven different radiation doses (1, 4, 8.4, 46, 102, 500, and 1000 Gy) to determine dose-effect estimates for reproduction, mortality, and life span. Effects on reproduction and genetic material were observed at the lowest doses and in the same range; detrimental reproductive effects were observed at 1 to 4 Gy, and the frequency of chromosomal aberrations were significantly increased at 2 Gy. Only high doses resulted in acute mortality (>500 Gy) and decreased life span (>100 Gy).Dose-effect estimates for chromosomal aberration induction were dependent on radiation dose and on the stage of the cell cycle at the time of irradiation. Dose-effect estimates for reproduction were dependent on dose and the potential for repopulation of gonadal tissue. It is concluded that short-term genotoxicity test can be predictive of detrimental reproductive effects in those model systems for which basic cell kinetics and reproductive parameters are well known.

Effect of cations on copper adsorption by kaolin

Varying amounts of CaCl2 or MgCl2 were first equilibrated with a dilute suspension of H+-kaolin and then with spiked (high activity radioactive 64Cu) water. After filtration, through 0.45 μm Millipore membrane the amount of radioactivity on the filter and the filtrate was measured separately using a Gamma ray well counter. Adsorption of Cu (expressed as distribution coefficient −Kd) was plotted against Ca or Mg concentration. Kd values decreased sharply at Ca or Mg concentration from 0 to 10 mg l−1 and changed only slightly from 10 to 200 mg l−1. Increase in the concentration of Ca or Mg reduces the Cu binding capacity of the clay.