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Taupp T.,University of Koblenz-Landau | Wetzel M.A.,University of Koblenz-Landau | Wetzel M.A.,German Federal Institute of Hydrology BfG
Ecological Indicators | Year: 2013

In the context of the requirements of the European Water Framework Directive (WFD) numerous benthic indices have been proposed recently to assess the ecological quality of marine and transitional waters. In several studies these metrics were applied to coastal and estuarine environments under diverse anthropogenic pressures. Although currently the dumping of dredged material is one of the most prominent human impacts that modify estuaries, the performance of benthic indices to detect effects of dredged sediment relocation has not yet been tested explicitly. Hence we examined a selection of common metrics (species richness, Shannon diversity, AMBI, M-AMBI, W-value, BO2A) at 11 dumping and 11 nearby reference areas in the highly modified Elbe estuary (Germany), where permanent dredging is necessary to maintain the depth of the navigation channel. In order to cover the entire estuary, the study area spanned over the whole salinity gradient from limnic to euhaline. Additionally, we investigated changes in benthic communities due to dredged material placement. All indices, except the W-value, were suitable to differentiate between dumping and reference areas and showed significantly better index values exclusively at reference areas. The applicability of AMBI and M-AMBI was restricted in the limnic stretch due to the more frequent occurrence of freshwater species there. The W-value and BO2A were non-satisfactory in the case of azoic sediment, and in most cases these two indices indicated much better ecological status classifications than the other indices tested. Furthermore, the BO2A had restricted applicability with increasing salinity. At eight of eleven sites the benthic communities differed significantly between dumping and reference areas. Our findings show that the power of conventional benthic indices to detect physical disturbances like the dumping of dredged sediment varies greatly. Having this in mind, we suggest to choose carefully the benthic indices for ecological quality assessments according to the WFD in estuaries in order to avoid misclassifications. Such errors may lead to unnecessarily expensive remediation activities or, in the opposite case, to inactivity although actions were necessary. Furthermore, in order to better meet the WFD requirements we suggest that, regarding frequency and volume, dumping should be adapted as far as possible to the natural processes of sediment movement. © 2013 Elsevier Ltd. All rights reserved.

Wetzel M.A.,German Federal Institute of Hydrology BfG | Wetzel M.A.,University of Koblenz-Landau | Scholle J.,BioConsult Schuchardt and Scholle GbR | Teschke K.,Alfred Wegener Institute for Polar and Marine Research
Marine Environmental Research | Year: 2014

Artificial substrates are omnipresent today in most estuaries mostly in form of massive rip-rap used for groynes and jetties. In the Weser estuary, Germany, 60% of the shoreline is covered with such artificial substrates while, natural rocky substrate is lacking, as in all Wadden Sea estuaries. This large quantity of artificial substrates may be colonized by a benthic hard-substrate community which differs from the local natural soft-substrate assemblage. In this study we examined species compositions, abundances, biomass, and numbers of species of subtidal benthic communities on groynes and in the natural habitat, the sediment, along the salinity gradient of the Weser estuary. Species composition changed on both substrates significantly with salinity and was also significantly different between the substrates. In a comparison with the sediment, the groynes did not provide any benefit for non-indigenous nor for endangered species in terms of abundance, biomass, and number of species, but represent habitats with higher total abundances and biomass; though some non-indigenous species even occurred exclusively on groynes. In particular, groynes supported filter-feeding organisms which play an important role by linking benthic and pelagic food webs. The dominance of the suspension feeders affects crucial estuarine ecosystem services and may have important implications for the estuarine management by altering the estuarine ecological quality status. Hence, artificial substrates should be considered in future conservation planning and in ecological quality monitoring of the benthic fauna according to the European Water Framework Directive. © 2014 Elsevier Ltd.

Wetzel M.A.,German Federal Institute of Hydrology BfG | Wetzel M.A.,University of Koblenz-Landau | Wahrendorf D.-S.,German Federal Institute of Hydrology BfG | von der Ohe P.C.,Helmholtz Center for Environmental Research
Science of the Total Environment | Year: 2013

Sediment contamination is one of the most pressing environmental problems in estuaries of industrialized countries and is of special interest to water managers involved in waterway maintenance dredging. In the present study, eight heavy metals (As, Pb, Cd, Cr, Cu, Ni, Hg, and Zn) and 41 organic compounds (pentachlorbenzol (PeCB), hexachlorbenzol (HCB), 7 polychlorinated biphenyls (PCBs), the hexachlorocyclohexanes α-HCH, β-HCH, γ-HCH, 6 dichlorodiphenyltrichloroethane isomers, organochlorine styrene (OCS), octachloronaphthalene (OCN), 15 polycyclic aromatic hydrocarbons (PAHs), and 6 organotin (OT) compounds) were analyzed in surface sediments at 36 sites in the Elbe estuary in 2006. Correlation analysis showed a general decrease in sediment contaminant concentrations from the stations near the port of Hamburg towards the open sea. This decrease was significant (Spearman's rank correlation, p. <. 0.05) with most pollutants. In addition, cluster analysis identified five groups of sites with different sediment contaminant patterns within the Elbe estuary. Worst case toxic risks stemming from sediment-bound organic pollutants were predicted using the Toxic Unit approach, based on estimated pore-water concentrations under equilibrium conditions and acute LC50 values for three standard test organisms of the trophic levels of fish, invertebrates, and algae. The estimated sediment toxicity was significantly higher in the inner part (river-km 630 to 660) compared with the estuarine mouth. Moreover, potential toxicity of organic pollutants estimated for invertebrates and for fish exceeded acute-based effect thresholds at 30 and 24 stations, respectively. Chronic effects for invertebrates are expected at all sites investigated. We conclude that sediment pollution and related potential toxicity in the Elbe estuary may have more influence on the benthos fauna than expected to date. © 2013 Elsevier B.V.

Taupp T.,University of Koblenz-Landau | Wetzel M.A.,University of Koblenz-Landau | Wetzel M.A.,German Federal Institute of Hydrology BfG
Estuarine, Coastal and Shelf Science | Year: 2014

The Venice System is one of the best-known and most applied systems to classify waters with respect to salinity. It has often been subject to criticism because the criteria used to derive zone boundaries were not made explicit. Consequently, an alternative multivariate PCA method that aimed at identifying salinity zones by means of the salinity ranges preferred by species was introduced by Bulger etal. (1993). We tested the applicability of both methods using salinity and benthic macroinvertebrate data for the poikilohaline Elbe Estuary (Germany) from 1997 to 2012. This was done by comparing the resultant salinity zone limits from the two approaches with boundaries where significant community changes were found by means of cluster analysis. Only the Venice System polyhaline and limnetic zone boundaries, and the PCA method outer estuary zone limit, showed good agreement with the benthic community pattern. None of the other Venice System or PCA method zone limits reflected the benthic community patterns. Our findings suggest that zone limits can only be well determined from mean salinity at the inner and outer end of the estuary, where the variation of salinity is relatively low. In contrast, in the middle of the estuary variation in salinity is the better predictor of zone boundaries. Thus, application of the Venice System or the PCA method in poikilohaline estuaries, such as the Elbe, is not meaningful and their use should be limited to homoiohaline systems. For poikilohaline systems, we found cluster analysis to be a better tool to identify salinity-zone boundaries. © 2014 Elsevier Ltd.

Heye K.,Goethe University Frankfurt | Becker D.,Goethe University Frankfurt | Lutke Eversloh C.,German Federal Institute of Hydrology BfG | Durmaz V.,Zuse Institute Berlin | And 3 more authors.
Water Research | Year: 2016

The antiepileptic drug carbamazepine (CBZ) and its main metabolites carbamazepine-10,11-epoxide (EP-CBZ) and 10,11-dihydro-10,11-dihydroxy-carbamazepine (DiOH-CBZ) were chosen as test substances to assess chronic toxicity on the non-biting midge Chironomus riparius. All the three substances were tested in a 40-day sediment full life cycle test (according to OECD 233) in which mortality, emergence, fertility, and clutch size were evaluated. In addition, these parameters were considered to calculate the population growth rate which represents an integrated measure to assess population relevant effects. With an LC50 of 0.20 mg/kg (time-weighted mean), the metabolite EP-CBZ was significantly more toxic than the parent substance CBZ (LC50: 1.1 mg/kg). Especially mortality, emergence, and fertility showed to be sensitive parameters under the exposure to CBZ and EP-CBZ. By using classical molecular dynamics (MD) simulations, the binding of CBZ to the ecdysone receptor was investigated as one possible mode of action (MoA) but appeared to be unlikely. The second metabolite DiOH-CBZ did not cause any effects within the tested concentration rage (0.17-1.2 mg/kg).Even though CBZ was less toxic compared to EP-CBZ, CBZ is found in the environment at much higher concentrations and therefore causes a higher potential risk for sediment dwelling organisms compared to its metabolites. Nevertheless, the current study illustrates the importance of including commonly found metabolites into the risk assessment of parent substances. © 2016 Elsevier Ltd.

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