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The history of toxicity tests with duckweeds shows that these assays with free-floating aquatic angiosperms are gaining increasing attention in ecotoxicological research and applications. Standard tests have been published by national and international organizations, mainly with the test species Lemna minor and Lemna gibba. Besides the former two test species the great duckweed Spirodela polyrhiza is to date also regularly used in duckweed testing. Under unfavorable environmental conditions, the latter species produces dormant stages (turions) and this has triggered the attention of two research groups from Belgium and Greece to jointly develop a “stock culture independent” microbiotest with S. polyrhiza. A 72 h new test has been worked out which besides its independence of stock culturing and maintenance of live stocks is very simple and practical to perform, and much less demanding in space and time than the conventional duckweed tests. Extensive International Interlaboratory Comparisons on the S. polyrhiza microbiotest showed its robustness and reliability and triggered the decision to propose this new assay to the ISO for endorsement and publication as a standard toxicity test for duckweeds. Sensitivity comparison of the 72 h S. polyrhiza microbiotest with the 7d L. minor assay for 22 compounds belonging to different groups of chemicals revealed that based on growth as the effect criterion both duckweed assays have a similar sensitivity. Taking into account its multiple advantages and assets, the S. polyrhiza microbiotest is a reliable and attractive alternative to the conventional duckweed tests.

In 1990, following an agreement with the Royal Nepal Academy of Science, the Italian National Research Council (CNR) installed a scientific laboratory (Pyramid) at 5,050 m (s.l.) in the Himalayan region. Among the environmental related researches, the task project RATEAP (Remote Areas Trace Elements Atmospheric Pollution), started in 2001, aims at obtaining information about the chemical composition of the high altitude airborne particulate matter. During the period of March-April 2002 series of samplings have been carried out by pump aspiration. Samples of total suspended particles (TSP) as well as of the particles size fraction PM10 and PM 2.5 have been collected and submitted to INAA for the determination of more than 30 elements present, at nanogram levels, in few micrograms of air dust. Data quality assurance has been performed by the analysis of different NIST SRMs and, in particular, the SRM 2783 Air particulate on Filter Media.

Auditory localization accuracy (in humans) in the median sagittal plane has been attributed, by some authors, to an effect of “spectral notches” that occurs in the frequency region of 4–8 kHz. Another possibility for decrements in vertical plane localization accuracy has been overlooked. Roffler and Butler (1967) and Hebrank and Wright (1974) both demonstrated that removal or absence of sound frequencies above about 8 to 10 kHz led to decrements in vertical plane localization accuracy. They did this by using carefully selected types of band pass or band limited noise. A reduction in accuracy of auditory vertical localization by occluding all or part of the pinna has been known for many years [Gardner and Gardner (1973)]. We have previously reported results that demonstrate disruption in accuracy with various partial pinna occlusions [ARO (2012)] that differs from results reported by Gardner and Gardner. We now have data that seems to indicate that the reduction in localization accuracy occurs, in part, because of disturbances in high frequency regions (above about 8 to 10 kHz) and that disruptions in “spectral notches” (4–8 kHz) has little to no effect upon vertical plane localization.

Cadmium enters the aquatic environment from numerous sources, e.g., via the atmosphere, from which the cadmium released by combustion, mainly of fossil fuels, is deposited. Since some fertilizers contain up to 40 mg/kg cadmium, wash-out from agricultural land is another source. Zinc ores contain up to several percent of cadmium, and there may be high concentrations in raw zinc, zinc alloys and zinc compounds, so that cadmium may enter the aquatic environment from mining residues, solid wastes and wastewater discharges. Once in the aquatic environment, cadmium is highly mobile. Its dissolved species are extremely labile, and are the first to be released, e.g., when salinity increases in estuaries. Sediments reflect the metal loading in the past, and their analysis can be the key to an understanding of the fate of anthropogenic discharges into the hydrosphere. The internal cadmium loading of aquatic systems can be estimated from the remobilization rates of cadmium from sediments.

Executive summary : One of the most internationally used bioassays for toxicity screening of chemicals and for toxicity monitoring of effluents and contaminated waters is the acute toxicity test with daphnid crustaceans, and in particular that performed with Daphnia magna. Standard methods have been developed for this assay that were gradually endorsed by national and international organisations dealing with toxicity testing procedures, in view of its application within a regulatory framework. As for all toxicity tests, the organisms used for the acute D. magna assay have to be obtained from live stocks which are cultured in the laboratory on live food (micro-algae). Unsurprisingly the various standard protocols of this particular assay differ – at least to a certain extent – with regard to the test organism culturing conditions. In addition, some technical aspects of the toxicity test such as the effect criterion (mortality of immobility), the exposure time, the type of dilution water, etc., also vary from one standard to another. Although this particular assay is currently used in many countries, the technical and biological problems inherent in year-round culturing and availability of the biological material and the culturing/maintenance costs of live stocks restrict its application to a limited number of highly specialised laboratories. This fundamental bottleneck in toxicity testing triggered investigations which brought forward the concept of “microbiotests” or “small-scale” toxicity tests. “Culture/maintenance free” aquatic microbiotests with species of different phylogenetic groups were developed in the early 1990s at the Laboratory for Environmental Toxicology and Aquatic Ecology at the Ghent University in Belgium. These assays which were given the generic name “Toxkits”, are unique in that they employ dormant stages (“cryptobiotic eggs”) of the test species, which can be stored for long periods of time and “hatched” at the time of performance of the assays. One of these microbiotests is the Daphtoxkit F magna, which is currently used in many laboratories worldwide for research as well as for toxicity monitoring purposes. The microbiotest technology has several advantages in comparison to the “traditional” tests based on laboratory cultures, especially its independence of the stock culturing burden. However, the acceptance (or possible non-acceptance) of performing assays with test organisms obtained from “dormant eggs” should be clearly dictated by the “sensitivity” and “precision” criteria of the former assays in comparison to the latter. The first part of this review therefore thoroughly reviews the scientific literature and of data obtained from various laboratories for assays performed with either D. magna test organisms obtained from lab cultures or hatched from dormant eggs. Attention has focused on data of quality control tests performed on reference chemicals, and in particular on potassium dichromate (K2Cr2O7) for which an acceptability range of 0.6–2.1 mg·L–1 has been set in ISO standard 6341 for the 24 h EC50 of the acute D. magna assay. Mean EC50s, standard deviations and variation coefficients were calculated from the collected data, all of which are presented in tables and figures and discussed in detail. The major conclusions drawn from the analysis of the large number of quality control (QC) data on the acute D. magna toxicity test are that : (1) Virtually all results from assays performed with Daphnias taken from lab cultures or with Daphnia microbiotests are within the acceptability range set by ISO standard 6341 for the reference chemical potassium dichromate. (2) The mean 24 h EC50s of the Daphnia microbiotests performed in different laboratories are within the range of the mean EC50s of the assays based on lab cultures, and the variation coefficients (20 to 30%) are similar. (3) The precision – in terms of the long term in house variability – of the quality control Daphnia microbiotests is as good as that of the QC tests based on lab cultures. The review further reports on intra-laboratory sensitivity comparison studies performed during the last 15 years on pure chemicals and on natural samples, with both laboratory cultured organisms and Daphnias hatched from dormant eggs. These studies carried out in different laboratories showed EC50 correlation coefficients of 0.86 to 0.98, corroborating a similar sensitivity of the two types of test organisms. The third part of the review reports and analyses data on proficiency ringtests on the acute D. magna assay which have been organised in different countries since 2002 with either reference chemicals or with natural samples, and in which part of the laboratories performed their assays with Daphnia microbiotests and others with lab cultured Daphnias. The conclusions drawn from all the ringtests indicate that the sensitivity of Daphnia neonates hatched from dormant eggs is similar to that of test organisms taken from lab cultures and that in most cases the precision of the Daphnia microbiotest is superior to that of the assays based on lab cultures. The review finally addresses the issue of possible sensitivity differences of Daphnias hatched from dormant eggs which are produced by different D. magna strains. From these investigations it appeared that the EC50s from assays performed with Daphnias hatched from dormant eggs of different strains did not differ significantly from those from assays undertaken with daphnids from lab cultures. The obvious advantages of Daphnia microbiotests over tests with Daphnias stemming from lab cultures have led to the worldwide use of these culture/maintenance free and low cost small-scale assays in both research and toxicity monitoring. The Daphnia microbiotest is in current use in several countries for toxicity testing in a regulatory framework, and recent calculations indicate that about 10 000 acute D. magna assays are now performed annually with neonates hatched from dormant eggs. The use of dormant eggs to obtain test organisms independently of stock culturing has recently also been accepted in international standards for toxicity testing. ISO standard 20665 (2008) related to the determination of chronic toxicity with Ceriodaphnia dubia, and ISO standard 20666 (2008) for the determination of the chronic toxicity with Brachionus calyciflorus in 48 h, both indicate that the assays can be conducted with organisms hatched from dormant eggs. On the basis of the extensive scientific evidence provided in this review that is justifiably supported by the two ISO methods mentioned above, the authors therefore recommend that the use of Daphnias hatched from dormant eggs should also be incorporated in national and international standards, as an alternative to the use of Daphnias taken from laboratory cultures.

Lake Orta (North Italy) is one of the series of north-south oriented lakes on the southern slopes of the Alps. Pollution of this lake began in the late 1920s with massive discharges of ammonium sulphate and copper from a rayon factory; phytoplankton, zooplankton and fish eventually disappeared. In the following decades, a low-pH regime was established due to the in-lake oxidation of ammonium to nitrate, the geological setting (granite, gneisses, and micaschists) favouring this development by not offering sufficient buffer capacity to the lake. Additional human activities in the catchment area, since the mid-seventies, have added further metals such as chromium, nickel, zinc and lead. The concentrations of C, P, N, S, Si, Ca, Mg, K, Al, Fe, Mn, Cd, Cr, Cu, Ni, Pb, Zn, Hg and Ti were estimated on the basis of 57 grab samples, evenly taken over the whole lake. The samples were analyzed by non-destructive X-ray fluorescence spectrometry, differential pulse anodic stripping voltammetry and electrothermal atomic absorption spectrometry. Distribution maps have been drawn (by means of computer-assisted cartography) for each individual metal to assist in the assessment of the dispersion and accumulation effects. It is very likely that the metal enrichment observed in the sediments in the northeast section of Lake Orta has been caused by focusing phenomena. The mapping, together with statistical treatment of the results and comparison with previous data, has allowed hypotheses to be advanced about the origin and fate of the various pollutants, and suggestions to be made for the recovery of the lake.