Atmospheric Electricity Influencing Biogeochemical Processes in Soils and Sediments.

The Earth's subsurface represents a complex electrochemical environment that contains many electro-active chemical compounds that are relevant for a wide array of biologically driven ecosystem processes. Concentrations of many of these electro-active compounds within Earth's subsurface environments fluctuate during the day and over seasons. This has been observed for surface waters, sediments and continental soils. This variability can affect particularly small, relatively immobile organisms living in these environments. While various drivers have been identified, a comprehensive understanding of the causes and consequences of spatio-temporal variability in subsurface electrochemistry is still lacking. Here we propose that variations in atmospheric electricity (AE) can influence the electrochemical environments of soils, water bodies and their sediments, with implications that are likely relevant for a wide range of organisms and ecosystem processes. We tested this hypothesis in field and laboratory case studies. Based on measurements of subsurface redox conditions in soils and sediment, we found evidence for both local and global variation in AE with corresponding patterns in subsurface redox conditions. In the laboratory, bacterial respiratory responses, electron transport activity and H2S production were observed to be causally linked to changes in atmospheric cation concentrations. We argue that such patterns are part of an overlooked phenomenon. This recognition widens our conceptual understanding of chemical and biological processes in the Earth's subsurface and their interactions with the atmosphere and the physical environment.

Resource niche overlap promotes stability of bacterial community metabolism in experimental microcosms.

Decomposition of organic matter is an important ecosystem process governed in part by bacteria. The process of decomposition is expected to benefit from interspecific bacterial interactions such as resource partitioning and facilitation. However, the relative importance of resource niche breadth (metabolic diversity) and resource niche overlap (functional redundancy) on decomposition and the temporal stability of ecosystem processes received little scientific attention. Therefore, this study aims to evaluate the effect of an increase in bacterial community resemblance on both decomposition and the stability of bacterial metabolism in aquatic sediments. To this end, we performed laboratory microcosm experiments in which we examined the influence of bacterial consortia differing in number and composition of species on bacterial activity (Electron Transport System Activity, ETSA), dissolved organic carbon production and wavelet transformed measurements of redox potential (Eh). Single substrate affinities of the individual bacterial species were determined in order to calculate the metabolic diversity of the microbial community. Results presented here indicate that bacterial activity and organic matter decomposition increase with widening of the resource niche breadth, and that metabolic stability increases with increasing overlap in bacterial resource niches, hinting that resource niche overlap can promote the stability of bacterial community metabolism.

Cell turnover and detritus production in marine sponges from tropical and temperate benthic ecosystems.

This study describes in vivo cell turnover (the balance between cell proliferation and cell loss) in eight marine sponge species from tropical coral reef, mangrove and temperate Mediterranean reef ecosystems. Cell proliferation was determined through the incorporation of 5-bromo-2'-deoxyuridine (BrdU) and measuring the percentage of BrdU-positive cells after 6 h of continuous labeling (10 h for Chondrosia reniformis). Apoptosis was identified using an antibody against active caspase-3. Cell loss through shedding was studied quantitatively by collecting and weighing sponge-expelled detritus and qualitatively by light microscopy of sponge tissue and detritus. All species investigated displayed substantial cell proliferation, predominantly in the choanoderm, but also in the mesohyl. The majority of coral reef species (five) showed between 16.1±15.9% and 19.0±2.0% choanocyte proliferation (mean±SD) after 6 h and the Mediterranean species, C. reniformis, showed 16.6±3.2% after 10 h BrdU-labeling. Monanchora arbuscula showed lower choanocyte proliferation (8.1±3.7%), whereas the mangrove species Mycale microsigmatosa showed relatively higher levels of choanocyte proliferation (70.5±6.6%). Choanocyte proliferation in Haliclona vansoesti was variable (2.8-73.1%). Apoptosis was negligible and not the primary mechanism of cell loss involved in cell turnover. All species investigated produced significant amounts of detritus (2.5-18% detritus bodyweight(-1)·d(-1)) and cell shedding was observed in seven out of eight species. The amount of shed cells observed in histological sections may be related to differences in residence time of detritus within canals. Detritus production could not be directly linked to cell shedding due to the degraded nature of expelled cellular debris. We have demonstrated that under steady-state conditions, cell turnover through cell proliferation and cell shedding are common processes to maintain tissue homeostasis in a variety of sponge species from different ecosystems. Cell turnover is hypothesized to be the main underlying mechanism producing sponge-derived detritus, a major trophic resource transferred through sponges in benthic ecosystems, such as coral reefs.

Hazard and risk of herbicides for marine microalgae.

Due to their specific effect on photosynthesis, herbicides pose a potential threat to coastal and estuarine microalgae. However, comprehensive understanding of the hazard and risk of these contaminants is currently lacking. Therefore the aim of the present study was to investigate the toxic effects of four ubiquitous herbicides (atrazine, diuron, Irgarol(®)1051 and isoproturon) and herbicide mixtures on marine microalgae. Using a Pulse Amplitude Modulation (PAM) fluorometry based bioassay we demonstrated a clear species and herbicide specific toxicity and showed that the current environmental legislation does not protect algae sufficiently against diuron and isoproturon. Although a low actual risk of herbicides in the field was demonstrated, monitoring data revealed that concentrations occasionally reach potential effect levels. Hence it cannot be excluded that herbicides contribute to observed changes in phytoplankton species composition in coastal waters, but this is likely to occur only occasionally.

Laboratory algal bioassays using PAM fluorometry: effects of test conditions on the determination of herbicide and field sample toxicity.

Pulse Amplitude Modulation (PAM) fluorometry, based on chlorophyll a fluorescence, is a frequently used technique in algal bioassays to assess toxicity of single compounds or complex field samples. Several test conditions can influence the test results, and because a standardized test protocol is currently lacking, linking the results of different studies is difficult. Therefore, the aim of the present study was to gain insight into the effects of test conditions of laboratory algal bioassays using PAM fluorometry on the outcome of toxicity tests. To this purpose, we described the results from several pilot studies on test development in which information is provided on the effects of the main test factors during the pretest phase, the test preparation, the exposure period, and the actual measurement. The experiments were focused on individual herbicides and complex field samples and included the effects of culturing conditions, cell density, solvent concentration, exposure time, and the presence of actinic light. Several of these test conditions were found to influence the outcome of the toxicity test, and the presented information provides important background information for the interpretation of toxicity results and describes which test conditions should be taken into account when using an algal bioassay with PAM fluorometry. Finally, the application of PAM fluorometry in algal toxicity testing is discussed.

Metal leaching, acidity, and altitude confine benthic macroinvertebrate community composition in Andean streams.

Andean streams drain metal-rich bedrock and are subjected to an extreme altitude gradient, which may create highly selective conditions for life. The aim of the present study was to evaluate the combined effects of metals and altitude on benthic macroinvertebrate community composition in Andean streams. Metal-rich sites were characterized by high metal concentrations and low pH, and high-altitude sites were characterized by high ultraviolet-B radiation and low concentrations of dissolved organic matter. Canonical correspondence analysis indicated that the patterns in faunal composition were best explained by metals followed by altitude, with dipterans and collembolans occurring mostly under harsh conditions of high altitude and high metal levels. Interaction between metals and altitude was most evident at metal-rich sites. It is suggested that in Andean streams, metal leaching from igneous rock and altitude may be important factors confining benthic macroinvertebrate communities, reducing their numbers and changing their composition toward specialized taxa.

Changes in the planktonic microbial community during residence in a surface flow constructed wetland used for tertiary wastewater treatment.

Suspended particles are a major constituent of municipal wastewater and generally contain high levels of bacteria, including human pathogens. Discharge of these particles of anthropogenic nature can have profound effects on receiving aquatic ecosystems and mitigation of these effects requires additional polishing of treated municipal wastewater. Previously it was shown that surface flow constructed wetlands are effective in improving water quality by reducing the numbers of fecal indicator organisms. However, fecal indicator organisms represent only a minor fraction of the total planktonic bacterial community and knowledge on the effects of these constructed wetlands on the composition and functioning of the entire planktonic bacterial community is limited. The aim of this descriptive study was therefore to identify changes in the planktonic bacterial community during residence of secondary treated municipal wastewater in a full-scale surface flow constructed wetland. To this purpose water samples were taken in which the bacterial community composition and functioning were analyzed using FISH, DGGE and BIOLOG. Surprisingly, the bacterial abundance at the inflow of the constructed wetland was relatively low compared with more natural surface waters. However, the inflowing bacterial community showed high metabolic activity and functional diversity. During residence in the surface flow constructed wetland the bacterial abundance doubled, but decreased in metabolic activity and functional diversity. Shifts in the community composition indicate that these changes are related to turn-over of the bacterial community. The planktonic bacterial community in the effluent of the constructed wetland closely resembled natural bacterial communities in urban and agricultural ditches. Based on these observations we conclude that constructed wetlands are capable to mitigate possible impacts of the particle load in treated wastewaters by transforming the anthropological bacterial community to a bacterial community resembling more "natural" surface waters.

UV radiation and organic matter composition shape bacterial functional diversity in sediments.

UV radiation and organic matter (OM) composition are known to influence the species composition of bacterioplankton communities. Potential effects of UV radiation on bacterial communities residing in sediments remain completely unexplored to date. However, it has been demonstrated that UV radiation can reach the bottom of shallow waters and wetlands and alter the OM composition of the sediment, suggesting that UV radiation may be more important for sediment bacteria than previously anticipated. It is hypothesized here that exposure of shallow OM-containing sediments to UV radiation induces OM source-dependant shifts in the functional composition of sediment bacterial communities. This study therefore investigated the combined influence of both UV radiation and OM composition on bacterial functional diversity in laboratory sediments. Two different OM sources, labile and recalcitrant OM, were used and metabolic diversity was measured with Biolog GN. Radiation exerted strong negative effects on the metabolic diversity in the treatments containing recalcitrant OM, more than in treatments containing labile OM. The functional composition of the bacterial community also differed significantly between the treatments. Our findings demonstrate that a combined effect of UV radiation and OM composition shapes the functional composition of microbial communities developing in sediments, hinting that UV radiation may act as an important sorting mechanism for bacterial communities and driver for bacterial functioning in shallow waters and wetlands.

Daphnid life cycle responses to new generation flame retardants.

Relatively hazardous brominated flame retardants (BFRs) are currently substituted with halogen-free flame retardants (HFFRs). Consequently, information on their persistence, bioaccumulation and toxicity (PBT) is urgently needed. Therefore, we investigated the chronic toxicity to the water flea Daphnia magna of two HFFRs, aluminum diethylphosphinate (ALPI) and 9,10-dihyro-9-oxa-10-phosphaphenanthrene-oxide (DOPO). The toxicity of ALPI increased from a 48 h LC50 of 18 mg L(-1) to a 21 day LC50 value of 3.2 mg L(-1), resulting in an acute-to-chronic ratio of 5.6. This may imply a change in classification from low to moderate toxicity. ALPI also affected sublethal life cycle parameters, with an EC50 of 2.8 mg L(-1) for cumulative reproductive output and of 3.4 mg L(-1) for population growth rate, revealing a nonspecific mode of action. DOPO showed only sublethal effects with an EC50 value of 48 mg L(-1) for cumulative reproductive output and an EC50 value of 73 mg L(-1) for population growth rate. The toxicity of DOPO to D. magna was classified as low and likely occurred above environmentally relevant concentrations, but we identified specific effects on reproduction. Given the low chronic toxicity of DOPO and the moderate toxicity of ALPI, based on this study only, DOPO seems to be more suitable than ALPI for BFR replacement in polymers.

Surviving in a marine desert: the sponge loop retains resources within coral reefs.

Ever since Darwin's early descriptions of coral reefs, scientists have debated how one of the world's most productive and diverse ecosystems can thrive in the marine equivalent of a desert. It is an enigma how the flux of dissolved organic matter (DOM), the largest resource produced on reefs, is transferred to higher trophic levels. Here we show that sponges make DOM available to fauna by rapidly expelling filter cells as detritus that is subsequently consumed by reef fauna. This "sponge loop" was confirmed in aquarium and in situ food web experiments, using (13)C- and (15)N-enriched DOM. The DOM-sponge-fauna pathway explains why biological hot spots such as coral reefs persist in oligotrophic seas--the reef's paradox--and has implications for reef ecosystem functioning and conservation strategies.

Toxicity of new generation flame retardants to Daphnia magna.

There is a tendency to substitute frequently used, but relatively hazardous brominated flame retardants (BFRs) with halogen-free flame retardants (HFFRs). Consequently, information on the persistence, bioaccumulation and toxicity (PBT) of these HFFRs is urgently needed, but large data gaps and inconsistencies exist. Therefore, in the present study the toxicity of a wide range of HFFRs to the water flea Daphnia magna was investigated. Our results revealed that four HFFRs were showing no effect at their Sw (saturated water concentration) and three had a low toxicity (EC50>10 mg L(-1)), suggesting that these compounds are not hazardous. Antimony trioxide had a moderate toxicity (EC50=3.01 mg L(-1), 95% CL: 2.76-3.25) and triphenyl phosphate and the brominated reference compound tetra bromobisphenol A were highly toxic to D. magna (EC50=0.55 mg L(-1), 95% CL: 0.53-0.55 and EC50=0.60 mg L(-1), 95% CL: 0.24-0.97 respectively). Aluminum trihydroxide and bisphenol A bis(diphenyl phosphate) caused limited mortality at Sw (26 and 25% respectively) and have a low solubility (<10 mg L(-1)). Hence, increased toxicity of these compounds may be observed when for instance decreasing pH could increase solubility. By testing all compounds under identical conditions we provided missing insights in the environmental hazards of new generation flame retardants and propose as best candidates for BFR replacements: APP, ALPI, DOPO, MHO, MPP, ZHS and ZS.

Persistence, bioaccumulation, and toxicity of halogen-free flame retardants.

Polymers are synthetic organic materials having a high carbon and hydrogen content, which make them readily combustible. Polymers have many indoor uses and their flammability makes them a fire hazard. Therefore, flame retardants (FRs) are incorporated into these materials as a safety measure. Brominated flame retardants (BFRs), which accounted for about 21% of the total world market of FRs, have several unintended negative effects on the environment and human health. Hence, there is growing interest in finding appropriate alternative halogen-free flame retardants (HFFRs). Many of these HFFRs are marketed already, although their environ- mental behavior and toxicological properties are often only known to a limited extent, and their potential impact on the environment cannot yet be properly assessed. Therefore, we undertook this review to make an inventory of the available data that exists (up to September 2011) on the physical-chemical properties, pro- duction volumes, persistence, bioaccumulation, and toxicity (PBT) of a selection of HFFRs that are potential replacements for BFRs in polymers. Large data gaps were identified for the physical-chemical and the PBT properties of the reviewed HFFRs. Because these HFFRs are currently on the market, there is an urgent need to fill these data gaps. Enhanced transparency of methodology and data are needed to reevaluate certain test results that appear contradictory, and, if this does not provide new insights, further research should be performed. TPP has been studied quite extensively and it is clearly persistent, bioaccumulative, and toxic. So far, RDP and BDP have demonstrated low to high ecotoxicity and persistence. The compounds ATH and ZB exerted high toxicity to some species and ALPI appeared to be persistent and has low to moderate reported ecotoxicity. DOPO and MPP may be persistent, but this view is based merely on one or two studies, clearly indicating a lack of information. Many degradation studies have been performed on PER and show low persistence, with a few exceptions. Additionally, there is too l ittle information on the bioaccumulation potential of PER. APP mostly has low PBT properties; however, moderate ecotoxicity was reported in two studies. Mg(OH)2, ZHS, and ZS do not show such remarkably high bioaccumulation or toxicity, but large data gaps exist for these compounds also. Nevertheless, we consider the latter compounds to be the most promising among alternative HFFRs. To assess whether the presently reviewed HFFRs are truly suitable alternatives, each compound should be examined individually by comparing its PBT values with those of the relevant halogenated flame retardant. Until more data are available, it remains impossible to accurately evaluate the risk of each of these compounds, including the ones that are already extensively marketed.

Contribution of soil, water and food consumption to metal exposure of children from geological enriched environments in the coastal zone of Lake Victoria, Kenya.

Geologically enriched environments may contain high concentrations of some metals. In areas where industrial exposures remain superficial, children may be exposed to these geological metals through soil, drinking water and consumption of food locally grown. The aim of this study was to assess the contribution of soil, water and food consumption to cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), cobalt (Co) and titanium (Ti) body burden of children in the geologically metal rich coastal zone of Lake Victoria, Kenya. We evaluated the relationship between the metal body burden of children by analyzing the hair samples and the estimated metal intake through exposure to soil, drinking water, and food consumption. The body burdens of all metals in children at the exposed sites were high, suggesting environmental exposure. Most of the foods consumed resulted in metal intake below the maximum recommended daily intake. However, the net contribution of all food items jointly exceeded the recommended maximum daily intake at some of the exposure sites. Our results further demonstrated that the highest intake of metals occurred via ingestion of high quantities of the cyprinid fish Rastrineobola argentea. Positive linear relationships between the metal body burden in children and estimated daily intake were observed for Cd, Cr, Ti in children consuming high quantity of R. argentea; for Zn and Co in children highly exposed to soils and consuming high quantity of Brassica oleraceae, while Co burden in the body was associated with high consumption of maize meal. This study demonstrated that exposure to soil and consumption of higher quantities of some foods contributed to the increased metal body burdens of children in a geologically exposed region.

Persistence of chironomids in metal polluted andean high altitude streams: does melanin play a role?

In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple stress conditions, hypothesizing that melanin counteracts both the adverse effects of solar radiation and of metals. Melanin was determined in chironomids from reference and metal polluted streams at 3000 and 4000 m altitude, being 2-fold higher at 4000 m compared to 3000 m, and 2-fold higher in polluted streams than in reference streams at both altitudes. The field observations were experimentally verified by assessing the combined effects of Cu and UV-B on the survival and melanin concentration in larvae of the model species Chironomus riparius (Chironomidae, Diptera). In laboratory exposures, the highest melanin concentrations were found in larvae surviving toxic Cu concentrations, but not in those exposed to the highest UV-B radiation. Pre-exposure to UV-B decreased the sensitivity of the larvae to UV-B and to Cu+UV-B. It is concluded that in the field, melanin may protect chironomids partially against both elevated metal concentrations and solar radiation, allowing them to persist under the harshest conditions in high altitude streams.

Suspended particle and pathogen peak discharge buffering by a surface-flow constructed wetland.

Constructed wetlands (CWs) have been shown to improve the water quality of treated wastewater. The capacity of CWs to reduce nutrients, pathogens and organic matter and restore oxygen regime under normal operating conditions cannot be extrapolated to periods of incidental peak discharges. The buffering capacity of CWs during peak discharges is potentially a key factor for water quality in the receiving waters. Therefore, the aim of the present study was to investigate the behaviour of peak discharges of suspended particles, (associated) physiochemical parameters and pathogenic organisms from a wastewater treatment plant (WWTP) in a full scale constructed wetland (CW). By mixing clarified water and sludge rich water from the settlement tank of the WWTP, the suspended particle concentration was increased for 8 h from ± 3.5 to ± 230 mg L(-1), and discharged into a full scale horizontal surface flow constructed wetland. An increase of suspended particle concentration following the peak discharge concurred with increases in turbidity and oxygen demand, total nutrient load (nitrogen, phosphorus and carbon) and pathogens (Escherichia coli and Enterococci). Temperature, pH, conductivity and dissolved nutrient concentrations (nitrogen, phosphorus and carbon) were however unaffected by the initial peak discharge. After retention in the unvegetated ponds (the first CW compartment) the applied suspended particle peak with a total load of 86.2 kg was reduced by >99%. Similar peak buffering was observed for the turbidity, oxygen demand and settable volume. Simultaneously dissolved nutrient concentrations increased, indicating partial mineralization of the suspended particles during retention in the unvegetated ponds. The peak buffering of pathogens was lower (40-84%), indicating differences in removal processes between other suspended particles and pathogens. The results indicated that the suspended particles were probably mostly removed by sedimentation and mineralization, where pathogens were more likely buffered by biofilm retainment, mortality and predation, mainly in reed ditches. After passing through the total CW the residuals of the suspended particle peak discharge were temporal increased concentrations of inorganic carbon (IC), NH(4) and E. coli (respectively 11%, 17% and 160% higher than steady state concentrations). The observations support the positive role of CWs for effective buffering of wastewater discharge peaks.

Gene expression patterns and life cycle responses of toxicant-exposed chironomids.

Cellular stress responses are frequently presumed to be more sensitive than traditional ecotoxicological life cycle end points such as survival and growth. Yet, the focus to reduce test duration and to generate more sensitive end points has caused transcriptomics studies to be performed at low doses during short exposures, separately and independently from traditional ecotoxicity tests, making comparisons with life cycle end points indirect. Therefore we aimed to directly compare the effects on growth, survival, and gene expression of the nonbiting midge Chironomus riparius. To this purpose, we simultaneously analyzed life cycle and transcriptomics responses of chironomid larvae exposed to four model toxicants. We observed that already at the lowest test concentrations many transcripts were significantly differentially expressed, while the life cycle end points of C. riparius were hardly affected. Analysis of the differentially expressed transcripts showed that at the lowest test concentrations substantial and biologically relevant cellular stress was induced and that many transcripts responded already maximally at these lowest test concentrations. The direct comparison between molecular end life cycle responses after fourteen days of exposure revealed that gene expression is more sensitive to toxicant exposure than life cycle end points, underlining the potential of transcriptomics for ecotoxicity testing and environmental risk assessment.

Combining next-generation sequencing and microarray technology into a transcriptomics approach for the non-model organism Chironomus riparius.

Whole-transcriptome gene-expression analyses are commonly performed in species that have a sequenced genome and for which microarrays are commercially available. To do such analyses in species with no or limited genome data, i.e. non-model organisms, necessary transcriptomics resources, i.e. an annotated transcriptome and a validated gene-expression microarray, must first be developed. The aim of the present study was to establish an advanced approach for developing transcriptomics resources for non-model organisms by combining next-generation sequencing (NGS) and microarray technology. We applied our approach to the non-biting midge Chironomus riparius, an ecologically relevant species that is widely used in sediment ecotoxicity testing. We sampled extensively covering all C. riparius developmental stages as well as toxicant exposed larvae and obtained from a normalized cDNA library 1.5 M NGS reads totalling 501 Mbp. Using the NGS data we developed transcriptomics resources in several steps. First, we designed 844 k probes directly on the NGS reads, as well as 76 k probes targeting expressed sequence tags of related species. These probes were tested for their affinity to C. riparius DNA and mRNA, by performing two biological experiments with a 1 M probe-selection microarray that contained the entire probe-library. Subsequently, the 1.5 M NGS reads were assembled into 23,709 isotigs and 135,082 singletons, which were associated to ~55 k, respectively, ~61 k gene ontology terms and which corresponded together to 22,593 unique protein accessions. An algorithm was developed that took the assembly and the probe affinities to DNA and mRNA into account, what resulted in 59 k highly-reliable probes that targeted uniquely 95% of the isotigs and 18% of the singletons. Concluding, our approach allowed the development of high-quality transcriptomics resources for C. riparius, and is applicable to any non-model organism. It is expected, that these resources will advance ecotoxicity testing with C. riparius as whole-transcriptome gene-expression analysis are now possible with this species.

Response of the nonbiting midge Chironomus riparius to multigeneration toxicant exposure.

The ability of the nonbiting midge Chironomus riparius to withstand long-term toxicant exposure has been attributed to genetic adaptation. Recently, however, evidence has arisen that supports phenotypic plasticity. Therefore, the present study aimed to investigate if Chironomus riparius indeed copes with prolonged toxicant exposure through phenotypic plasticity. To this purpose, we performed a multigeneration experiment in which we exposed C. riparius laboratory cultures for nine consecutive generations to two exposure scenarios of, respectively, copper, cadmium, and tributyltin. Total emergence and mean emergence time were monitored each generation, while the sensitivity of the cultures was assessed at least every third generation using acute toxicity tests. We observed that the sublethally exposed cultures were hardly affected, while the cultures that were exposed to substantially higher toxicant concentrations after the sixth generation were severely affected in the eighth generation followed by signs of recovery. A marginal lowered sensitivity was only observed for the highly exposed cadmium culture, but this was lost again within one generation. We conclude that C. riparius can indeed withstand long-term sublethal toxicant exposure through phenotypic plasticity without genetic adaption.

Dynamics of metal uptake and depuration in a parasitized cyprinid fish (Rastrineobola argentea).

Infestation of fish by endoparasites may potentially influence metal uptake and elimination by the host. We quantified the metal uptake rate constant (k(u)) and efflux rate constants (k(e)) of radiolabeled Cd and Co in the cyprinid fish Rastrineobola argentea experimentally infected with the parasite Ligula intestinalis. During 24h, the accumulation of Cd and Co increased linearly with no evident steady state in uninfected fish, infected fish and in the parasite. Following aqueous exposures, the k(u) for Cd in parasites was about 3× higher than that of infected fish and 6× higher than for the uninfected fish. The k(u) for Co was up to 15× higher in the parasites than that of infected fish and 7.5× higher than for the uninfected fish. The k(e) for excretion of Cd were consistently higher for the uninfected fish than for the infected fish and also higher for uninfected fish than the parasite. The k(e) for Co for the uninfected fish was 1.4-2.0× lower than in the infected fish, but higher for parasites compared to uninfected fish (1.3-2.3×). Pulse-chase feeding experiments with radiolabeled copepods showed that Cd assimilation efficiency from food was higher in infected fish, while Co was assimilated more effectively by uninfected fish. The observed differences in metal dynamics between infected and uninfected R. argentea in the laboratory concord with differences in metal concentrations measured in natural populations in Lake Victoria. Our findings provide evidence that L. intestinalis infection enhances Cd accumulation, but depletes the essential Co in the cyprinid fish R. argentea. We conclude that the combined stress of parasites and pollution changes metal risks to fish hosts in a metal specific manner.

Element profiles in hair and nails of children reflect the uptake from food and the environment.

The present study evaluated if the element profiles in hair and nails of children from the Lake Victoria region in Kenya reflect uptake from food and the environment. To this purpose, the element concentrations in hair and nails were related to element concentrations measured in food items, water, and soil. The highest intake of most elements occurred via ingestion of the fish Rastrineobola argentea, which is consumed in higher quantities than other fish and food items. Element concentrations in hair and nails were correlated to food and soil in element-specific patterns. Multivariate analysis combining principal component analysis and multidimensional scaling enabled us to cluster individuals from specific sites and to relate differences between sites to food-consumption patterns and environmental exposures. Site-specific differences in macroelement concentrations among the children were attributed to patterns of food consumption, while those in microelement concentrations reflected differences in geochemical background. It is concluded that the simultaneous analysis of elements in human hair and nails allows separation of populations based on food consumption and geochemical background.