Summary
1. Ship‐induced waves disturb benthic invertebrate assemblages colonizing littoral zones of lakes and rivers. However, the impact of ship‐induced waves on invertebrates has rarely been ...quantified, and the influencing factors have not been addressed.
2. In an experimental wave tank, five benthic invertebrate species, Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeseli and Laccophilus hyalinus, were exposed to waves of increasing shear stress (0.43–2.19 N m−2). Mean number of detached individuals was recorded for five littoral habitats coarse woody debris (CWD), reeds, sand, stones and tree roots, representing different levels of structural complexity as quantified by their fractal dimensions (FD).
3. Results showed that detachment of invertebrates was significantly related to shear stress in all habitats except tree roots. Detachments averaged for the five species were significantly lower in habitats with a high degree of structural complexity, decreasing in the habitat sequence: sand, CWD, stones, reeds and tree roots.
4. Consistent with their different morphologies and methods of attachment to substrates, the five species displayed differences in their response to hydraulic stress that were dependent on habitat.
5. The increasing sheltering effect of structural habitat complexity was mirrored by increasing dissipation of the kinetic energy of waves; i.e. the FD of the habitat was positively correlated with shear stress reduction due to the flow resistance of the habitat.
6. Network habitats such as tree roots provided the best sheltering conditions against hydraulic disturbance, because they combined good refuge availability for all studied invertebrate species and maximal dissipation of kinetic wave energy. Consequently, persistent anthropogenic impacts, such as lakeshore modification or long‐term exposure to ship‐induced waves, which cause disappearance of complex littoral habitats such as tree roots or dense reed belts, will drastically increase the adverse effects of boating and ship traffic on littoral invertebrate assemblages.
Fluvial networks are globally relevant for the processing of dissolved organic matter (DOM). To investigate the change in molecular DOM diversity along the river course, high-field FTICR mass ...spectrometry and NMR spectroscopy of riverine DOM as well as bacterial abundance and activity were measured in a third order stream along a land-use gradient from pristine, agricultural to urban landscapes. DOM composition showed a clear evolution along the river course with an initial decrease of average oxidation and unsaturation followed by an increased relative abundance of CHNO and CHOS compounds introduced by agriculture and waste water, respectively. DOM composition was dominated by rather unsaturated CHO compounds (H/C ≤ 1) in headwaters and by more aliphatic molecules at downstream sites. Oxygenated functional groups shifted from aromatic ethers and hydroxyl groups to aliphatic carboxylic acids and aliphatic hydroxyl groups. This massive dislocation of oxygen significantly increased the diversity of atomic environments in branched aliphatic groups from headwater to downstream DOM. Mass spectra of DOM enabled the detection of compositional relationships to bacterial abundance and activity which was positively related to more aliphatic components (H/C > 1) and negatively related to unsaturated components. FTICR mass and NMR spectra corroborated the initial decline in DOM molecular diversity predicted by the River Continuum Concept (RCC) but demonstrated an anthropogenic increase in the molecular diversity of DOM further downstream. While the high DOM molecular diversity in first order headwater streams was the result of small scale ecosystem plurality, agriculture and waste water treatment introduced many components in the lower reaches. These anthropogenic influences together with massive bacterial oxidation of DOM contributed to a growth of molecular diversity of downstream DOM whose composition and structure differed entirely from those found in pristine headwaters.
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•DOM composition evolved from unsaturated to more aliphatic components.•Proportions of CHNO and CHOS compounds increased downstream.•Bacterial activity was positively related to more aliphatic components.•DOM diversity decreased in the upper part (river continuum concept).•DOM diversity increased in the lower part with agriculture and urban areas.
In this paper, we consider the application of the U-Th-He method of isotope geochronology for native gold dating. It was shown that inclusions of uranium- and thorium-bearing minerals, including rare ...earth element phosphates, are one of the main form of uranium and thorium occurrence and, consequently, the main source of radiogenic helium in native gold. Since these inclusions are submicrometer-sized, the radiogenic helium formed in them is not accumulated but implanted in the structure of native gold, which suggests its good preservation over billions of years. This suggestion was experimentally supported by the investigation of the kinetics of radiogenic helium release from native gold. The first results of the U-Th-He dating of native gold from the Pedrolampi (central Karelia) and Witwatersrand (South Africa) deposits are in adequate agreement with available independent geochronological data. This allows us to consider native gold as a U-Th-He mineral geochronometer for the direct dating of ore-forming processes.
New Os isotope data obtained for oxides separated from samples of the Jurassic dolerites of Tasmania (Australia) are used to constrain the petrogenesis of the Ferrar continental flood basalt ...province. It is proposed here that the unradiogenic initial Os ratio (187Os/188Os = 0middot145 + or - 0middot049 2sigma) of these rocks is inconsistent with petrogenetic models involving the assimilation of continental crust by mantle-derived magmas. Instead, the results are more readily explained by models in which the introduction of upper-crustal materials into the mantle contaminates the source of these magmas before melting. The increasing body of Os isotope data for mantle-derived rocks also provides new opportunities to assess whether any distinction between the roles of asthenospheric vs lithospheric mantle in the genesis of continental flood basalts might be possible. It is concluded that, in the absence of an Os-rich phase with low Re/Os, the uncertainties in calculated initial ratios preclude the distinction between mantle sources in this particular case.
The assessment of the exposure of aquatic wildlife to complex environmental mixtures of chemicals originating from both point and diffuse sources and evaluating the potential impact thereof ...constitutes a significant step towards mitigating toxic pressure and the improvement of ecological status. In the current proof-of-concept study, we demonstrate the potential of a novel Aggregated Biomarker Response (ABR) approach involving a comprehensive set of biomarkers to identify complex exposure and impacts on wild brown trout (Salmo trutta fario). Our scenario used a small lowland river in Germany (Holtemme river in the Elbe river catchment) impacted by two wastewater treatment plants (WWTP) and diffuse agricultural runoff as a case study. The trout were collected along a pollution gradient (characterised in a parallel study) in the river. Compared to fish from the reference site upstream of the first WWTP, the trout collected downstream of the WWTPs showed a significant increase in micronucleus formation, phase I and II enzyme activities, and oxidative stress parameters in agreement with increasing exposure to various chemicals. By integrating single biomarker responses into an aggregated biomarker response, the two WWTPs' contribution to the observed toxicity could be clearly differentiated. The ABR results were supported by chemical analyses and whole transcriptome data, which revealed alterations of steroid biosynthesis and associated pathways, including an anti-androgenic effect, as some of the key drivers of the observed toxicity. Overall, this combined approach of in situ biomarker responses complemented with molecular pathway analysis allowed for a comprehensive ecotoxicological assessment of fish along the river. This study provides evidence for specific hazard potentials caused by mixtures of agricultural and WWTP derived chemicals at sublethal concentrations. Using aggregated biomarker responses combined with chemical analyses enabled an evidence-based ranking of sites with different degrees of pollution according to toxic stress and observed effects.
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•Three lines of evidence characterised a longitudinal contamination profile.•Aggregated Biomarker Response (ABR) enabled identification of toxic hot spots.•Transcriptome analyses identified mechanistic drivers of biological effects in fish.•Combined approach enabled comprehensive characterisation of toxic stress in fish.•Integration with chemical data allowed site-specific ranking of contamination.
Agricultural and urban land use has dramatically increased over the last century and one consequence is the release of anthropogenic chemicals into aquatic ecosystems. One of the rarely studied ...consequences is the effect of land use change on internal concentrations of organic micropollutants (OMPs) in aquatic invertebrates and its effects on their genotype diversity. Here, we applied population genetic and internal concentrations of OMPs analyses to determine evolutionary implications of chemical pollution on Gammarus pulex populations from a natural and two agricultural streams. Along 14 consecutive months sampled, 26 different OMPs were quantified in G. pulex extracts with the highest number, concentration, and toxic pressure in the anthropogenically stressed stream ecosystems. Our results indicate distinct internal OMP profiles and changes in both genetic variation and genetic structure in streams affected by anthropogenic activity. Genetic variation was attributed to chemical pollution whereas changes in the genetic structure were attributed to environmental disturbances, such as changes in discharge in the impacted stream ecosystems, which worked both independently and in tandem. Finally, we conclude that human-impacted streams are subjected to severe alterations in their population genetic patterns compared to nonimpacted stream ecosystems.
A new, rapid, low-blank method for extraction of osmium from geological materials is described. As with existing techniques, this new Os accumulation procedure relies upon the oxidation of Os in the ...sample solution to OsO
4 and utilises the volatile nature of this oxide. In contrast to previous distillation methods, however, osmium oxide is caught in a cold trap, coated on its inner surface with sulfuric acid instead of bubbling an Os oxide bearing carrier gas through chilled HCl or HBr. Once the distillation is complete, the trapped Os is extracted into 500 μl of HBr concentration and undergoes a final cleaning step which can be accomplished by employing conventional micro-distillation techniques. The entire extraction procedure from the sample solution takes approximately 90 min and requires only 2 μl of H
2SO
4 to trap the osmium, which is achieved with great efficiency. Thus, apart from the digestion medium, the extraction and recovery of Os in this technique employs a total of only ∼502 μl of reagents instead of approximately 5–10 ml in conventional procedures that ‘see’ the Os. As demonstrated here, the efficient extraction of Os and low reagent volumes required mean that it is possible to achieve yields of 80% and total procedural blanks of 100 fg routinely.
We compared the invertebrate production and stable isotope signatures of key ecosystem compartments of urban sites subjected to the input of tertiary-treated wastewater with those of upstream sites ...in an agricultural lowland stream. We detected a significant shift in the trophic basis of invertebrate production from upstream, natural and agricultural resources, to urban resources, i.e., wastewater-derived organic matter as well as autochthonous primary production based on wastewater-derived nutrients. Invertebrate production was higher at urban sites than at agricultural sites. However, the median contribution of the most important secondary producer, the shredder
Gammarus roeseli
, to total invertebrate production was lower at urban sites (9%) than at agricultural sites (61%). The low production of G. roeseli at urban sites was associated with the absence of allochthonous coarse particulate organic matter (CPOM) habitats, rather than the loss of CPOM as a food resource. Our results suggest that contemporary urban stressors in developed countries affect secondary producers less severely than historically recorded, but still profoundly change the matter fluxes and ecosystem functioning of running waters. Restoration of the native riparian vegetation, channel naturalization, and adequate dilution of tertiary-treated wastewater may partially mitigate adverse effects on invertebrate communities and their secondary production.
Lake ecosystems are strongly linked to their terrestrial surroundings by material and energy fluxes across ecosystem boundaries. However, the contribution of terrestrial particulate organic carbon ...(tPOC) from annual leaf fall to lake food webs has not yet been adequately traced and quantified. In this study, we conducted wholeâlake experiments to trace artificially added tPOC through the food webs of two shallow lakes of similar eutrophic status, but featuring alternative stable regimes (macrophyte rich vs. phytoplankton dominated). Lakes were divided with a curtain, and maize (Zea mays) leaves were added, as an isotopically distinct tPOC source, into one half of each lake. To estimate the balance between autochthonous carbon fixation and allochthonous carbon input, primary production and tPOC and tDOC (terrestrial dissolved organic carbon) influx were calculated for the treatment sides. We measured the stable isotope ratios of carbon (δ¹³C) of about 800 samples from all trophic consumer levels and compared them between lake sides, lakes, and three seasons. Leaf litter bag experiments showed that added maize leaves were processed at rates similar to those observed for leaves from shoreline plants, supporting the suitability of maize leaves as a tracer. The lakeâwide carbon influx estimates confirmed that autochthonous carbon fixation by primary production was the dominant carbon source for consumers in the lakes. Nevertheless, carbon isotope values of benthic macroinvertebrates were significantly higher with maize additions compared to the reference side of each lake. Carbon isotope values of omnivorous and piscivorous fish were significantly affected by maize additions only in the macrophyteâdominated lake and δ¹³C of zooplankton and planktivorous fish remained unaffected in both lakes. In summary, our results experimentally demonstrate that tPOC in form of autumnal litterfall is rapidly processed during the subsequent months in the food web of shallow lakes and is channeled to secondary and tertiary consumers predominantly via the benthic pathways. A more intense processing of tPOC seems to be connected to a higher structural complexity in littoral zones, and hence may differ between shallow lakes of alternative stable states.
