Species-sensitivity distribution methods assemble single-species toxicity data to predict hazardous concentrations (HCps) affecting a certain percentage (p) of species in a community. The fit of the lognormal model and required number of individual species values were evaluated with 30 published data sets. The increasingly common assumption that a lognormal model best fits these data was not supported. Fifteen data sets failed a formal test of conformity to a lognormal distribution; other distributions often provided better fit to the data than the lognormal distribution. An alternate bootstrap method provided accurate estimates of HCp without the assumption of a specific distribution. Approximate sample sizes producing HC5 estimates with minimal variance ranged from 15 to 55, and had a median of 30 species-sensitivity values. These sample sizes are higher than those suggested in recent regulatory documents. A bootstrap method is recommended that predicts with 95% confidence the concentration affecting 5% or fewer species.

Species-sensitivity distribution methods assemble single-species toxicity data to predict hazardous concentrations (HCps) affecting a certain percentage (p) of species in a community. The fit of the lognormal model and required number of individual species values were evaluated with 30 published data sets. The increasingly common assumption that a lognormal model best fits these data was not supported. Fifteen data sets failed a formal test of conformity to a lognormal distribution; other distributions often provided better fit to the data than the lognormal distribution. An alternate bootstrap method provided accurate estimates of HCp without the assumption of a specific distribution. Approximate sample sizes producing HC5 estimates with minimal variance ranged from 15 to 55, and had a median of 30 species-sensitivity values. These sample sizes are higher than those suggested in recent regulatory documents. A bootstrap method is recommended that predicts with 95% confidence the concentration affecting 5% or fewer species.

The ability of Spartina alterniflora to degrade tributyltin (TBT) in contaminated dredge spoils was investigated in a created wetland at Little Creek Naval Amphibious Base in Norfolk, Virginia, USA. Concentrations of TBT up to 250 ng/g did not inhibit S. alterniflora growth over a 16-month period. Disappearance rates of TBT in vegetated and unvegetated treatments were similar, with half-lives of 300 to 330 d. Disappearance rates were not constant, but they were correlated to temperature changes and were possibly due to microbial degradation within the sediment. Of the initial amount of TBT in the sediment, only 0.4% accumulated in S. alterniflora biomass. Uptake of TBT by S. alterniflora was greatest in belowground biomass (43 ng/g). During plant senescence, most of the TBT was retained in the detrital material. Whereas S. alterniflora did not expedite the degradation of TBT, using TBT-contaminated dredge spoils to create wetlands is plausible. However, this should only be undertaken after further investigation into the potential for plant biomass to become a biovector for TBT.

The ability of Spartina alterniflora to degrade tributyltin (TBT) in contaminated dredge spoils was investigated in a created wetland at Little Creek Naval Amphibious Base in Norfolk, Virginia, USA. Concentrations of TBT up to 250 ng/g did not inhibit S. alterniflora growth over a 16-month period. Disappearance rates of TBT in vegetated and unvegetated treatments were similar, with half-lives of 300 to 330 d. Disappearance rates were not constant, but they were correlated to temperature changes and were possibly due to microbial degradation within the sediment. Of the initial amount of TBT in the sediment, only 0.4% accumulated in S. alterniflora biomass. Uptake of TBT by S. alterniflora was greatest in belowground biomass (43 ng/g). During plant senescence, most of the TBT was retained in the detrital material. Whereas S. alterniflora did not expedite the degradation of TBT, using TBT-contaminated dredge spoils to create wetlands is plausible. However, this should only be undertaken after further investigation into the potential for plant biomass to become a biovector for TBT.