Usability of the bivalves Dreissena polymorpha and Anodonta anatina for a biosurvey of the neurotoxin BMAA in freshwater ecosystems.

The environmental neurotoxin ß-methylamino-L-alanine (BMAA) may represent a risk for human health in case of chronic exposure or after short-term exposure during embryo development. BMAA accumulates in freshwater and marine organisms consumed by humans. It is produced by marine and freshwater phytoplankton species, but the range of producers remains unknown. Therefore, analysing the phytoplankton composition is not sufficient to inform about the risk of freshwater contamination by BMAA. Filter-feeders mussels have accumulation capacities and therefore appear to be relevant to monitor various pollutants in aquatic ecosystems. We investigated the suitability of the freshwater mussels Dreissena polymorpha and Anodonta anatina for monitoring BMAA in water. Both species were exposed to 1, 10, and 50 µg of dissolved BMAA/L daily for 21 days, followed by 42 days of depuration in clean water. On days 0, 1, 7, 14, and 21 of exposure and 1, 7, 14, 21 and 42 of depuration, whole D. polymorpha and digestive glands of A. anatina were sampled, and the total BMAA concentration was measured. D. polymorpha accumulated BMAA earlier (from day 1 at all concentrations) and at higher tissue concentrations than A. anatina, which accumulated BMAA from day 14 when exposed to 10 µg BMAA/L and from day 7 when exposed to 50 µg BMAA/L. As BMAA accumulation by D. polymorpha was time and concentration-dependent, with a significant elimination during the depuration period, this species may be able to reflect the levels and dynamics of water contamination by dissolved BMAA. The species A. anatina could be used for monitoring water concentrations above 10 µg BMAA/L.

Bio-accumulation of lanthanum from lanthanum modified bentonite treatments in lake restoration.

Lanthanum (La) modified bentonite (LMB) is one of the available mitigating agents used for the reduction of the phosphorus (P) recycling in eutrophic lakes. The potential toxicity of the La from LMB to aquatic organisms is a matter of concern. In this study the accumulation of La was investigated in the macrophyte Elodea nuttallii, in chironomid larvae and in several fish species during periods up to five years following in situ LMB applications. The application of LMB increased the La concentration of exposed plants and animals. During the first growing season following LMB applications, the La content of E. nuttallii increased 78 fold (3.98-310.68 µg La g-1 DW) to 127 fold (2.46-311.44 µg La g-1). During the second growing season following application, the La content decreased but was still raised compared to plants that had not been exposed. The La content of chironomids was doubled in the two years following LMB application, although the increase was not significant. Raised La concentrations in fish liver, bone, muscle and skin were observed two and five years following to LMB application. Liver tissues showed the highest La increase, ranging from 6 fold (0.046-0.285 µg La g-1 DW) to ∼20 fold (0.080-1.886 µg La g-1, and 0.122-2.109 µg La g-1) two years following application and from 6 fold (0.046-0.262 µg La g-1) to 13 fold (0.013-0.167 µg La g-1) after five years in pelagic and littoral fish. The La content of the liver from Anguilla anguilla (eel) had increased 94 fold (0.034-3.176 µg La g-1) two years and 133 fold (0.034-4.538 µg La g-1) five years following LMB application. No acute and chronic effects of La accumulation were observed and human health risks are considered negligible. We advocate the long-term study of effects of La accumulation following future LMB applications.

Effects of combined flocculant - Lanthanum modified bentonite treatment on aquatic macroinvertebrate fauna.

A low dose flocculant (FeCl3), combined with lanthanum modified bentonite (LMB) as phosphate-binding agent, has been applied for eutrophication management in Lake De Kuil (The Netherlands). After the treatment, the state of the lake shifted from hypertrophic to mesotrophic. Although macroinvertebrate fauna is important for lake ecosystems, the knowledge of its response to this lake restoration method is fragmented and scarce. Because insight in the macroinvertebrate fauna response is important to assess future applications, pre and post application macroinvertebrate assemblages were identified in Lake De Kuil. The research was accompanied by a microcosm experiment in which the effects of LMB, FeCl3 and LMB + FeCl3 were studied on macroinvertebrate communities. Results show the reduction of macroinvertebrate numbers and taxa during the first month following the application. The number of Gastropoda was strikingly reduced one month after the application. One year after the application, the macroinvertebrate numbers and taxa exceeded the pre-application situation and Gastropoda and Oligochaeta prospered. The effects one month after the treatment are most likely due to the combination of physical impacts of the use of bentonite and chemical impacts of the use of FeCl3, while effects after one year are likely attributed to the shift in trophic state of the lake.

Effects of an anionic surfactant (FFD-6) on the energy and information flow between a primary producer (Scenedesmus obliquus) and a consumer (Daphnia magna).

The effects of a commercially available anionic surfactant solution (FFD-6) on growth and morphology of a common green alga (Scenedesmus obliquus) and on survival and clearance rates of the water flea Daphnia magna were studied. The surfactant-solution elicited a morphological response (formation of colonies) in Scenedesmus at concentrations of 10-100 µl l(-1) that were far below the No Observed Effect Concentration (NOEC) value of 1,000 µl l(-1) for growth inhibition. The NOEC-value of FFD-6 for colony-induction was 3 µl l(-1). Daphnia survival was strongly affected by FFD-6, yielding LC(50-24h) and LC(50-48 h) of 148 and 26 µl l(-1), respectively. In addition, clearance rates of Daphnia feeding on unicellular Scenedesmus were inhibited by FFD-6, yielding a 50% inhibition (EC(50-1.5h)) at 5.2 µl l(-1) with a NOEC of 0.5 µl l(-1). When Daphnia were offered FFD-6-induced food in which eight-celled colonies (43 × 29 µm) were most abundant, clearance rates (~0.14 ml ind.(-1) h(-1)) were only 25% the rates of animals that were offered non-induced unicellular (15 × 5 µm) Scenedesmus (~0.56 ml ind.(-1) h(-1)). As FFD-6 concentrations in the treated food used in the experiments were far below the NOEC for clearance rate inhibition, it is concluded that the feeding rate depression was caused by the altered morphology of the Scenedesmus moving them out of the feeding window of the daphnids. The surfactant evoked a response in Scenedesmus that is similar to the natural chemically induced defensive reaction against grazers and could disrupt the natural information conveyance between these plankton organisms.

Metribuzin impairs the unicell-colony transformation in the green alga Scenedesmus obliquus.

Active growth is a prerequisite for the formation of grazing-protective, mostly eight-celled colonies by the ubiquitous green alga Scenedesmus in response to chemical cues from zooplankton. Colonies can also be evoked by chemically quite similar manmade anionic surfactants, such as FFD-6. In this study, it was hypothesized that growth-inhibiting concentrations of the herbicide metribuzin impair the ability of Scenedesmus obliquus to form colonies in response to the surfactant morphogen FFD-6. The results confirmed that the formation of colonies in S. obliquus was hampered by metribuzin. EC50 values of metribuzin for colony inhibition (approximately 11 µg L(-1)) were similar to those for growth and photosynthesis inhibition (12-25 µg metribuzinL(-1)). In the absence of the colony-inducing surfactant FFD-6, S. obliquus populations were comprised of 92% unicells, having on average 1.2 cells per colony at all tested metribuzin concentrations (0-100 µg L(-1)). In contrast, in the presence of FFD-6 and at low metribuzin concentrations (0 and 5 µg L(-1)), S. obliquus had more than five cells per colony with a high portion of eight-celled colonies. However, increasing concentrations of metribuzin decreased the number of colonies in the FFD-6-exposed populations and caused them to remain mostly unicellular at the highest concentrations (50 and 100 µg L(-1)). This study revealed that metribuzin impeded growth and by doing so, also obstructed the possibility for unicellular Scenedesmus to form colonies. Consequently, an increase in mortality of Scenedesmus from grazing is expected.

Behavioural responses of Gammarus pulex (Crustacea, Amphipoda) to low concentrations of pharmaceuticals.

The continuous discharge of pharmaceuticals and personal care products into the environment results in a chronic exposure of aquatic organisms to these substances and their metabolites. As concentrations in surface waters are in the ng/L range, and sometimes in the low microg/L range, they are not likely to result in lethal toxicity. However, prolonged exposure to low concentrations of anthropogenic chemicals may lead to sublethal effects, including changes in behaviour. The aim of this study was to assess the effect of three pharmaceuticals, the antidepressant fluoxetine, the analgesic ibuprofen and the anti-epileptic carbamazepine, and one cationic surfactant, cetyltrimethylammonium bromide (CTAB), on the activity of the benthic invertebrate Gammarus pulex (Crustacea: Amphipoda: Gammaridae). We used the multispecies freshwater biomonitor to assess changes in activity of G. pulex in a quantitative manner. Exposure to low concentrations (10-100ng/L) of fluoxetine and ibuprofen resulted in a significant decrease in activity, whereas the activity of G. pulex at higher concentrations (1microg/L-1mg/L) was similar to the control. Response to carbamazepine showed a similar pattern, however, differences were not significant. The tested surfactant CTAB evoked a decrease in activity at increasing concentration. These behavioural effect concentrations were 10(4) to 10(7) times lower than previously reported LOECs and in the range of environmentally occurring concentrations. The potential consequences of this decreased activity for G. pulex population growth and benthic community structure and the exposure to mixtures of pharmaceuticals deserves further attention.

Life-history consequences for Daphnia pulex exposed to pharmaceutical carbamazepine.

The effects of the antiepileptic, analgesic drug carbamazepine on the growth, morphology, and life-history characteristics of Daphnia pulex were examined at nominal concentrations of 0, 0.1, 1, 10, 100, and 200 microg L(-1). At 1 microg carbamazepine L(-1), Daphnia matured and reproduced slightly earlier than did controls, and at a given body length females produced more offspring than did controls or those receiving other treatments. In combination with a relatively high juvenile somatic growth rate and highest total number of progeny produced per female, carbamazepine at 1 microg L(-1) seemed to exert a stimulatory effect. The rates of population growth of the 100 and 200 microg L(-1) treatment groups was 9% and 32% lower, respectively, than the rates of growth of the controls and the Daphnia receiving treatments of up to 10 microg carbamazepine L(-1). At the highest dose, retardation of juvenile somatic growth resulted in delayed maturity and consequently in a lower rate of population growth. Adult somatic growth, spine length, reproductive output, and size of newborns were similar among treatments. Male offspring were only produced in the third broods, with broods that were 8% and 28% male at 1 and 10 microg L(-1), respectively. Neck teeth were never observed in Daphnia. Chronic adverse effects of carbamazepine on nontarget Daphnia were detected at 200 microg carbamazepine L(-1), but stimulatory effects might occur at environmentally realistic concentrations. However, additional studies of chronic toxicity investigating various combinations of pharmaceuticals and various environmental stresses, such as food condition, temperature, and kairomones, are needed to fully explore potential long-term adverse effects and to assess the environmental risk of common pharmaceuticals.

Effects of a surfactant (FFD-6) on Scenedesmus morphology and growth under different nutrient conditions.

Surfactants are man-made compounds that are meanwhile omnipresent in the environment, but environmental concentrations of surfactants are such that they are thought to have little risk for aquatic systems. The major anionic surfactants currently on the global market are linear alkylbenzene sulfonates (LAS), a class where the commercially available FFD-6 belongs to. The hypothesis was tested that sublethal effects of FFD-6, i.e. the morphological effect of colony formation in the common test alga Scenedesmus obliquus, occurs at a concentration lower than the no-observed-effect concentrations for endpoints commonly used in regulatory toxicity testing with algae. The surfactant FFD-6 induced colonies in Scenedesmus at concentrations a few orders of magnitude lower (i.e. between 0.001 and 0.01 g l-1) than at which growth inhibition was observed (i.e. between 1 and 10g l -1). Growth rates were lowest for Scenedesmus grown in P-limited medium, intermediate for algae reared in N-limited medium and highest for algae cultured in non-limited standard medium. Growth inhibition due to FFD-6 was similar for non-limited and nutrient-limited Scenedesmus, but colony formation was stronger in non-limited Scenedesmus than in nutrient limited cultures. The colony inducing effect of the surfactant FFD-6 on Scenedesmus occurs at much lower concentrations than growth inhibition and might affect species interactions, the survival of species and the energy flow along the food chain.

Effects of microcystin-free and microcystin-containing strains of the cyanobacterium Microcystis aeruginosa on growth of the grazer Daphnia magna.

Harmful effects of the common bloom-forming cyanobacterium Microcystis aeruginosa on the grazer Daphnia have been explained from morphological features, nutritional insufficiency, and the production of toxins called microcystins. The effects of four M. aeruginosa strains, including one free of microcystins, on the growth of Daphnia magna were examined. Population growth was measured in Daphnia fed each M. aeruginosa strain alone and fed mixtures of each strain with the green alga Scenedesmus obliquus to avoid nutritional deficiency. The presence of Microcystis in the food resulted in decreased Daphnia population growth rates. A significant correlation (P < 0.001) was found between the amount of microcystins (MC) in the food and the population growth rate, but growth inhibition in Daphnia fed with the MC-free strain could not be explained by the toxicity of the microcystins. Inasmuch as there was greater reduction in growth of the Daphnia fed mixtures of the MC-free strain with Scenedesmus than of the Daphnia fed only the same amount of Scenedesmus as in the mixtures, other factors associated with this Microcystis strain must have inhibited growth. However, morphology and nutritional insufficiency could be excluded as causal factors. The strong relationship between Daphnia feeding activity and population growth suggests that feeding inhibition may have caused the observed detrimental effects on the animals.