Search

Piscivorous birds in aquatic ecosystems exert predation pressure on fish populations. But the site-specific impact on fish populations, including stocked and commercially used fish species, remains disputed. One of the key questions for the management of piscivorous birds and fish is determining the origin of prey and thus which fish populations are targeted by the birds. We addressed this question by provenancing otoliths (earstones) of fish obtained from regurgitated pellets of piscivorous birds by otolith microchemistry analysis. We retrieved otoliths from regurgitated pellets of great cormorants (

The maternal transmission of a naturally occurring and non-toxic minor isotope of strontium (84Sr) to the central otolith region of the progeny of a typical European freshwater fish species, brown trout, Salmo trutta f.f. L. was accomplished. The focus was to apply minimum doses of a non-toxic solution at physiological salt concentration to minimise potential adverse effects on the fish. Female spawners were intraperitoneally injected with doses of 12.5 and 30.2 μg 84Sr kg−1 fish. Eggs were stripped and the resulting progeny were reared in a hatchery for about 1 year before sampling the otoliths. Strontium isotope ratios in the otoliths of the offspring were measured by cross-sectional line scans using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). Otolith cores of marked juveniles showed a significantly elevated 84Sr/86Sr ratio compared with control fish and to otolith regions created after hatching. Mass marking of cohorts of progeny from individually spiked brown trout with Sr isotopes is therefore possible for dispersal and migration studies without the necessity of handling eggs and applying other larval marking methods like immersion.

The potential to discriminate between wild and hatchery trout [Salmo trutta f. fario L. and Oncorhynchus mykiss (Walbaum)] by chronological microchemical patterns of different otolith regions was tested. Central and rim regions of otoliths were analysed for life stage specific elemental patterns of strontium (Sr), sodium (Na) and calcium (Ca) as well as of 87Sr/86Sr ratios using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Classification to life stage specific habitats was achieved with 100% accuracy by 88Sr/43Ca, 23Na/43Ca and 87Sr/86Sr ratios resulting in a discrimination of hatchery fish from wild fish. 87Sr/86Sr ratios and Sr concentration in otoliths were positively correlated with the ratio and amount in the water. Na content in otoliths did not directly reflect the concentration in the water, although the 23Na/43Ca ratio in otoliths contributed to the discrimination. Clear differences in otolith chemistry were found for fish experiencing different geological units or a groundwater-fed environment in a hatchery. Natural chronological microchemical patterns in otoliths proved to be a valuable tool for discriminating wild and hatchery fish without the necessity to use marking methods. LA-ICP-MS is well suited for this application because of its limited need for sample preparation, its potentially high sample throughput and the possibility of simultaneous measurement of multiple elemental and isotopic fingerprints.

Large concentrations of arsenic in soils, sediments, and freshwaters require risk assessment across the Central Alps and other regions. We measured arsenic concentrations in soil samples collected from 38 sites located in the Austrian Central Alps that had been contaminated due to mining and smelter activities and geogenic mineralization. Medians and ranges of arsenic concentrations (in mg kg—1) in the soil solid phase were: 77.1 (1—3000) for the total (Ast), 19.2 (0—726) for (NH4)2C2O4-extractable (Aso), 2.35 (0—169) for (NH4)2HPO4-extractable (Asp), and 0.143 (0—11.1) for (NH4)2SO4-extractable (Ass) arsenic. Arsenic concentrations in soil solutions (Assol) collected from organic surface layers and mineral horizons at five selected sites using suction cups fitted with nylon membranes ranged from 0 to 171 μg l—1. Typically, the prevailing species of As in the soil solution was As(V). Assol was correlated with Ass (Assol = 0.279 + 15.6 Ass; r2 = 0.938; n = 17) and Ast (Assol = 1.272 + 0.043 Ast; r2 = 0.833; n = 17). Using these empirical models, Assol can be predicted quite accurately based on extraction with 0.05 M (NH4)2SO4 or total arsenic concentrations in the soil. Linking these models to drinking water standards (DWS) we propose soil standards for freshwater protection that vary for Ass (mg kg—1) between 0.62 (for DWS = 10 μg l—1 WHO) and 3.19 (for DWS = 50 μg l—1). Corresponding standards for Ast (mg kg—1) are 203 (DWS = 10 μg l—1) and 1133 (DWS = 50 μg l—1). These considerations demonstrate that changes in legislation on DWS may have dramatic impact on As concentrations in soil that are acceptable for groundwater protection. Arsen in Bodenlosungen und Extrakten kontaminierter Boden und seine Bedeutung fur Bodenstandards Arsenkontaminationen in Boden, Sedimenten und Gewassern erfordern Risk Assessment in den Zentralalpen und anderen Regionen. Arsenmessungen in Bodenproben von 38 geogen oder durch Bergbau und Verhuttung kontaminierten Standorten in den osterreichischen Zentralalpen ergaben folgende Mediane und Spannweiten (in mg kg—1): 77.1 (1—3000) fur Arsen total (Ast), 19.2 (0—726) fur (NH4)2C2O4-extrahierbares (Aso), 2.35 (0—169) fur (NH4)2HPO4-extrahierbares (Asp), und 0.143 (0—11.1) fur (NH4)2SO4-extrahierbares (Ass) Arsen. Die Arsenkonzentrationen in mit Nylonsaugsonden aus organischen und Mineralbodenhorizonten an 5 ausgewahlten Standorten gewonnenen Bodenlosungen (Assol) variierten zwischen 0 und 171 μg As l—1. Die dominierende Arsenspezies in diesen Bodenlosungen war typischerweise As(V). Assol war mit Ass (Assol = 0.279 + 15.6 Ass; r2 = 0.938; n = 17) und Ast (Assol = 1.272 + 0.043 Ast; r2 = 0.833; n = 17) korreliert. Mit diesen empirischen Modellen kann Assol relativ genau aus der in 0,05 M (NH4)2SO4 gemessenen Arsenfraktion oder der Arsengesamtkonzentration geschatzt werden. Uber die Koppelung dieser Modelle mit Trinkwassergrenzwerten (DWS) konnen Bodengrenzwerte fur den Grundwasserschutz abgeleitet werden, welche fur Ass (mg kg—1) zwischen 0.62 (fur DWS = 10 μg l—1 laut WHO) und 3.19 (fur DWS = 50 μg l—1) liegen. Die entsprechenden Grenzwerte fur Ast (mg kg—1) liegen zwischen 203 (DWS = 10 μg l—1) und 1133 mg kg—1 (DWS = 50 μg l—1). Diese Uberlegungen zeigen den enormen Einfluss von Anderungen der Gesetzgebung fur DWS auf die im Hinblick auf den Grundwasserschutz akzeptablen Arsenkonzentrationen im Boden.