Abstract.Pollen samples were taken along nine transects across local vegetational belts bordering bogs or ponds in overall deciduous and coniferous-deciduous forest regions.

The individual effect of different major cations (Ca2+, Mg2+, Na+, K+, and H+) on the acute toxicity of zinc to the waterflea Daphnia magna was investigated. The 48-h median effective concentration (EC50) in the baseline test medium (i.e., a standard medium with very low ion concentrations) was about 6 microM (Zn2+). An increase of Ca2+ (from 0.25 mM to 3 mM), Mg2+ (from 0.25 mM to 2 mM), and Na+ activity (from 0.077 mM to 13 mM) reduced zinc toxicity by a factor of 6.3, 2.1, and 3.1, respectively. No further toxicity reduction was observed when Ca2+ and Mg2+ activities exceeded 3.0 and 2.0 mM, respectively. Both K+ and H+ did not significantly alter zinc toxicity (expressed as Zn2+ activity). From these data, conditional stability constants for Ca2+ (log K = 3.24), Mg2+ (log K = 2.97), Na+ (log K = 2.16), and Zn2+ (log K = 5.31) were derived and incorporated into a biotic ligand model (BLM) predicting acute zinc toxicity to D. magna in surface waters with different water quality characteristics. Validation of the developed BLM using 17 media with different pH, hardness, and dissolved organic carbon (DOC) content resulted in a significant correlation coefficient (R2 = 0.76) between predicted and observed 48-h EC50. Eighty-eight percent of the predictions were within a factor of 1.3 of the observed 48-h EC50.

In the past five years the use of rotifers in ecotoxicologial studies has substantially increased. This greater interest has been due to the central role of rotifers in freshwater planktonic communities, the ease and speed of making quantitative measurements of mortality and reproduction, their sensitivity to common pollutants, the commercial availability of cysts, and the existence of reliable, standardized protocols. The main endpoints used in ecotoxicology studies are reviewed, including mortality, reproduction, behavior, cellular biomarkers, mesocosms, and species diversity in natural populations. For each endpoint, published studies are cited, along with the compounds investigated, duration of exposure, and the LC50s, EC50s or NOECs reported. Rotifers have been included as part of a standardized mesocosm and in several large-scale, outdoor mesocosm studies. A critique of rotifer use in ecotoxicology is offered and it is concluded that the scientific basis for including rotifers as part of a battery of ecotoxicological tests is well established.

Triqlochin maritima Chamaedaphne calyculata Menyonthes trifol!ato Comorum (Potentilla} polustre-Utriculoria vulgaris Betula pumilo Larix loricina Sorrocenio purpurea Sphaqnum sp Ledum groenlondicum Oxycoccus quodripetalus Piceo mariana Soqiltoria /alifo/ia Sporgonium eurycorpum Companula u!iqinoso

Although a large body of evidence indicates that metal toxicity to soil organisms is affected by physicochemical soil properties, use of this knowledge in ecological risk assessments is limited because of the lack of a model applicable to a wide range of soils. To study the effect of soil characteristics on the toxicity of copper to terrestrial invertebrates, chronic toxicity tests with Eisenia fetida and Folsomia candida were performed in 19 European field soils. These soils were carefully selected to cover the range of toxicity-influencing parameters encountered in the European Union. Toxicity values varied greatly among soils, with 28-d median effect concentrations ranging from 72.0 to 781 mg Cu/kg dry weight for E. fetida and from 45.4 to 2,270 mg Cu/kg dry weight for F. candida. For both species, variation in copper toxicity values was best explained by differences in the actual cation-exchange capacity (CEC) at soil pH. Using the obtained regression algorithms, the observed toxicity could, in most cases, be predicted within a factor of two for E. fetida and within a factor of three for F. candida. The developed models were validated in three additional European field soils, a standard artificial soil and a standard field soil. The presented regression equations, based on the actual CEC, offer an easy-to-apply method for taking the influence of soil properties on metal toxicity into account.

The cellular energy allocation (CEA) methodology was used to assess the adverse effects of toxic stress on the energy budget of test organisms. This biochemical assay is quantified by determining changes in the available energy reserves, Ea (total carbohydrate, protein, and lipid content) and the energy consumption, Ec (electron transport activity). The CEA methodology was fully explored by using neonates of Daphnia magna exposed for 96 h to six model toxicants (CdCl2, K2Cr2O7, tributyltin chloride, linear alkylbenzene sulfonic acid, sodium pentachlorophenolate, and 2,4-dichlorophenoxyacetic acid). To evaluate the ecological relevance of the CEA parameter, we compared the suborganismal responses with population-level parameters (obtained from 21-d life-table experiments) such as the intrinsic rate of natural increase (rm) and the mean total offspring per female. The observed reductions in CEA values were both the result of a decrease in Ea and an increase in Ec. From all individual CEA components analyzed, the lipid reserve criterion was the most sensitive endpoint studied. Both the CEA-based lowest-observed-adverse-effect concentration (LOAEC) values and the effective concentration of 10% (EC10) values were significantly (p < 0.05) and linearly correlated with the chronic (21-d) LOAEC and EC10 values based on growth, survival, and reproduction. This relationship demonstrates the usefulness of the methodology to predict long-term effects. Furthermore, significant (p < 0.0001) sigmoid relationships between the 96-h CEA value (expressed as percentage relative to the control) and population-level effects were observed.

Pollen grains and spores in moss polsters are compared with vegetation along transects across vegetational gradients in a large peatland in northern Minnesota. The distribution, percentage values, and source of 135 pollen and spore types are traced and related to the broad-scale vegetation pattern in the midwestern United States, and to the fine-scale vegetation pattern in the peatland.The pollen assemblages of taxa presently not growing in the peatland constitute the regional pollen deposition, with nearly constant proportions of pollen types distributed across the study area. Regional pollen values are compared for several peatlands in northern Minnesota and with the regional forest composition. The fine-scale pattern of peatland vegetation types corresponds well with the spatial pattern of the local pollen assemblages. Peatland vegetation types are characterized on the basis of these pollen assemblages. Conclusions on development of peatland vegetation can be drawn from local pollen assemblages preserved in sediment cores. Pollen transport for wind-pollinated Abies, Pinus, Betula, Alnus, Fraxinus, and Typha is discernible in the peatland only within 200 m from their source in local plant populations. The dispersal pattern of Abies pollen from an Abies balsamifera stand is related to wind speed and direction and sky cover for as much as 5 yr preceding sample collection. Most peatland pollen types are restricted in distribution to their corresponding vegetation types.

Development of zinc tolerance is described for the cladoceran Daphnia magna Straus. Zinc tolerance (i.e., toxicity and deficiency) was monitored during successive generations of D. magna acclimated to different zinc concentrations. Survival, reproduction, carapax length measurements, and cellular energy allocation assessments were used as test endpoints. Special attention was paid to the consequences of zinc deficiency. The zinc acclimation concentration clearly influenced the overall fitness of the organism. After several generations of acclimation, an optimal concentration curve was observed, with an optimum zinc concentration between 300 and 450 microg/L. Zinc deficiency resulted in a lower zinc tolerance, a higher coefficient of variation for brood size, and an increased pH sensitivity. These results clearly indicate that (background) zinc concentrations present in test and culture media have to be considered in the evaluation of toxicity test results, especially when the toxicity data are used for water-quality guideline derivation and/or ecological risk assessment. Culture and test media containing very little or no zinc do not provide a basis for useful ecotoxicological data.