Stable nitrogen isotope Research Papers (original) (raw)

The stable carbon and nitrogen isotopes from organic compounds, and stable oxygen and carbon isotopes from inorganic carbonate in modern and fossil ostrich eggshell (OES) at Equus Cave, South Africa, were used to determine relative... more

The stable carbon and nitrogen isotopes from organic compounds, and stable oxygen and carbon isotopes from inorganic carbonate in modern and fossil ostrich eggshell (OES) at Equus Cave, South Africa, were used to determine relative changes in C3 and C4 ...

Lake Tanganyika is a globally important lake with high endemic biodiversity. Millions of people in the lake basin depend on several fish species for consumption. Due to the importance of fish consumption as an exposure route of mercury to... more

Lake Tanganyika is a globally important lake with high endemic biodiversity. Millions of people in the lake basin depend on several fish species for consumption. Due to the importance of fish consumption as an exposure route of mercury to humans, we sampled Lake Tanganyika in 2000 to assess total mercury concentrations and biomagnification of total mercury through the food web. Stable nitrogen and carbon isotope analyses of food web structure indicate a complex food web with overlapping omnivory with some specialist fish species. Stable nitrogen isotope analyses further confirm that mercury is biomagnifying through the Tanganyika food web at rates similar to those seen in Lakes Malawi and Victoria, the other two African Great Lakes. Most collected fish species and all invertebrate species had mercury concentrations below 0.2 μg Hg/g wet weight. However, several fish species, Ctenochromis horei (average 0.15 μg/g ww), Neolamprologus boulengeri (0.2 μg/g ww) , Bathybates spp.spp. (0.21 μg/g ww), Mastacembelus cunningtoni (0.22 μg/g ww) and Clarias theodorae (0.22 μg/g ww) approached or slightly exceeded the World Health Organization (WHO)'s recommended guideline of 0.2 μg Hg/g for vulnerable populations with high rates of fish consumption. Two individuals of the piscivorous fish species Lates microlepis (0.54, 0.78 μg/g ww) and a Polypterus congicus (1.3 μg/g ww) exceeded the international marketing limit value of 0.5 μg/g ww. Because C. theodorae and L. microlepis are also important market fish species, there is a need to monitor mercury concentrations in internationally marketed fish from Lake Tanganikya to ensure that those fish do not present a risk to human consumers.

Information on aquaculture-related environmental impact along the eastern Adriatic coast is very scarce. In this paper, the area affected by fish farm and sewage derived particulate nitrogen in the Murter Sea and semi-enclosed Pirovac Bay... more

Information on aquaculture-related environmental impact along the eastern Adriatic coast is very scarce. In this paper, the area affected by fish farm and sewage derived particulate nitrogen in the Murter Sea and semi-enclosed Pirovac Bay (central Adriatic, Croatia) was assessed using the stable nitrogen isotopic composition (δ15N) in particulate organic matter (POM) and benthic sessile invertebrates (Aplysina aerophoba, Balanus perforatus and Anemonia sulcata) in the exposed areas compared to an unpolluted reference site. The results suggest that increased δ15N values in the POM and biota in the impacted areas are predominantly due to nitrogen losses through feed wastage and fish excretion (faeces), but also due to the sewage discharge into the marine coastal ecosystems. The δ15N values of the selected organisms were significantly higher around fish cages, as well as at sites polluted by urban waste, compared to the reference site and some other pristine offshore locations. The 15N enrichments of A. aerophoba, A. sulcata and B. perforatus collected around fish cages compared to the reference location were up to 6.8, 6.5 and 5.2‰, respectively, which exceeds the natural variability. While the δ15N values of A. sulcata and B. perforatus showed an excellent linear correlation with those of the POM, a weaker correlation was found between δ15N of A. aerophoba and the POM, although its δ15N values consistently increased with the increased δ15N values of POM. This is attributed to the presence of different bacterial populations hosting in the sponge. A geochemical map of the δ15N values in the POM and organisms was created, which could be used for tracing the dispersion of 15N loading generated by aquaculture and sewage in the receiving environment, and their transfer into biota in the adjacent coastal ecosystem. Sponges or other organisms, although known as non-selective suspension feeders, but hosting abundant bacterial populations, may have δ15N values lower than the POM, but still reflecting the overall enrichment of the environment in 15N due to the presence of enriched effluents from aquaculture operation or municipal discharges.

The isotopic composition (δ 15 N) of dissolved ammonium (NH 4 + ) in the Delaware Estuary was related to reactions in the nitrogen cycle occurring in different regions of the estuary and at different rates throughout the year. The range... more

The isotopic composition (δ 15 N) of dissolved ammonium (NH 4 + ) in the Delaware Estuary was related to reactions in the nitrogen cycle occurring in different regions of the estuary and at different rates throughout the year. The range of values at any one location (as great as ...

Atmospheric deposition fluxes of soluble nutrients (N, P, Si, Fe, Co, Zn) to the tropical North Atlantic were determined during cruise M55 of the German SOLAS programme. Nutrient fluxes were highest in the east of the section along 10°N,... more

Atmospheric deposition fluxes of soluble nutrients (N, P, Si, Fe, Co, Zn) to the tropical North Atlantic were determined during cruise M55 of the German SOLAS programme. Nutrient fluxes were highest in the east of the section along 10°N, owing to the proximity of source regions in West Africa and Europe, and lowest in the west, for both dry and

Increasing δ15N and δ13C values in coastal Baltic marine sediments are evaluated as indicator of changes in the trophic status of the ecosystem. The influence of eutrophication on the δ15N values was found to be so dominant that it even... more

Increasing δ15N and δ13C values in coastal Baltic marine sediments are evaluated as indicator of changes in the trophic status of the ecosystem. The influence of eutrophication on the δ15N values was found to be so dominant that it even overprints the usually observed mixing gradient from terrestrial (low isotope values) to the marine environment (high isotope values).A distinct gradient in stable nitrogen isotope values from eutrophic coastal areas to open more oligotrophic waters in the central Baltic Sea and Gulf of Bothnia was found. Our data show high δ15N values in surface sediments: 13‰ in the Oder Lagoon and the Pomeranian Bight, over 9‰ in the Gulf of Riga (Daugava River), 7‰ in the inner Gulf of Finland (Neva River), 6.5‰ in the Curonian Lagoon (Nemunas River), and 5.7‰ in the Gdansk Deep (Vistula River). In the Baltic Sea Proper, significantly lower δ15N values of 3–5‰ are found. A decrease in δ15N values with depth/age of the sediment was indicated in some cores that were analyzed down to 15–40 cm depth in 1-cm steps. There is a great overall difference between pre-industrial δ15N values in coastal sediments and recent ones of 2.3–10‰. As explanations for this increase are suggested, elevated nutrient δ15N values of waste water in combination with fractionation processes like nutrient uptake by phytoplankton and denitrification and nitrification processes in rivers discharging into the coastal water. Delta 13C values in sediment surfaces off the river estuaries primarily indicate differences between the inorganic carbon signatures of the rivers. However, since the δ13C values also decrease downcore, we contribute this change to increased primary production caused by the enhanced nutrient load. Since both stable isotope values in sediments (δ13C and δ15N) correlate downcore, this strongly suggests that the anthropogenic nutrient loads in the rivers might be the reason for the changes of stable isotope values.

The diet of king penguins (Aptenodytes patagonicus) brooding chicks was investigated during February 2001 at the Falkland Islands, where a small but increasing population is located at the limit of the breeding range of this species. Fish... more

The diet of king penguins (Aptenodytes patagonicus) brooding chicks was investigated during February 2001 at the Falkland Islands, where a small but increasing population is located at the limit of the breeding range of this species. Fish was the most important food source by number (98.0%) and reconstituted mass (97.8%), squids accounting for the remainder. Myctophid fishes represented the main part of the diet (97.7% by number and 96.6% by reconstituted mass), Protomyctophum choriodon being by far the main prey item (84.2% and 88.1%, respectively). Four other myctophids and one squid species each contributed to more than 1% of the diet by number: Krefftichthys anderssoni (4.8%), Electrona carlsbergi (4.6%), Gymnoscopelus nicholsi (2.2%) and Protomyctophum tenisoni (1.8%), together with small juveniles of Gonatus antarcticus (1.8%). Twelve squid species were identified from accumulated lower beaks, including the ommastrephid Martialia hyadesi (48.3% by number), the onychoteuthids Moroteuthis ingens (15.6%), Kondakovia longimana (10.5%) and Moroteuthis knipovitchi (7.3%), and Gonatus antarcticus (9.2%). The stable-carbon and stable-nitrogen isotopic composition of chick food and adult blood differed in a way that suggests that, during the same trip, adult birds fed for themselves in distant foraging grounds, and fed for their chicks on their way back to the colony. The study emphasizes that king penguins are specialist myctophid eaters throughout their breeding range in summer, and highlights the importance of Protomyctophum choriodon as a link between zooplankton and top predators in the pelagic ecosystem of the southwestern Atlantic Ocean.

Declines in populations of Pacific salmon Oncorhynchus spp. have been most pronounced in the southern extent of their range, and numerous anthropogenic stressors and natural drivers have been identified as potential causes. Using a... more

Declines in populations of Pacific salmon Oncorhynchus spp. have been most pronounced in the southern extent of their range, and numerous anthropogenic stressors and natural drivers have been identified as potential causes. Using a paleolimnological approach, we have reconstructed the natural variability in the population dynamics of endangered Snake River sockeye salmon O. nerka over approximately the past 1,370 years.

This paper explores the impact of animal manure application on the δ15N values of a broad range of crops (cereals and pulses), under a range of manuring levels/regimes and at a series of locations extending from northwest Europe to the... more

This paper explores the impact of animal manure application on the δ15N values of a broad range of crops (cereals and pulses), under a range of manuring levels/regimes and at a series of locations extending from northwest Europe to the eastern Mediterranean. We included both agricultural field experiments and areas where ‘traditional’ farming is practised. Our aim is to ground-truth

Stable nitrogen isotope ratios (15N/14N; δ15N) were determined in sediments, suspended matter, and water at selected sites in the Baltic Sea area in order to set up a source budget and trace the fate of anthropogenic N sources. Sediments... more

Stable nitrogen isotope ratios (15N/14N; δ15N) were determined in sediments, suspended matter, and water at selected sites in the Baltic Sea area in order to set up a source budget and trace the fate of anthropogenic N sources. Sediments of the shallow near-coastal area of the southern and eastern Baltic Sea have an average δ15N of 7.3 ± 2.1‰, interpreted