d15N

Delta-N-15; δ15N

Measure for the enrichment of the stable nitrogen isotope 15N in the food web

Nitrogen exists naturally in the form of two stable isotopes, 14N and 15N, which differ in their atomic mass. By means of mass spectrometry (MS) both isotopes can be analysed separately (isotope ratio MS). In the air, 99.634% of the total nitrogen is 14N whereas 15N contributes only with 0.366%.

In organisms, 15N has a higher retention time, i.e. it is transformed and excreted more slowly and consequently accumulates in the organism. This leads to an increase of 15N relative to 14N. The ratio 15N/14N is expressed in the δ-notation (δ15N).

In the food web δ15N increases: carnivores have higher values than herbivores and herbivores have higher δ15N values than plants. With each trophic level the δ15N value increases by about 3 to 4 per mille (‰). The δ15N value can therefore be used to determine the trophic level of organisms.

When assessing chemical pollution, the trophic position of organisms can help to identify the accumulation of substances and their potential for biomagnification in the food web. This requires the parallel measurement of trophic position and chemical residues in the organism.
However, it must be kept in mind that also environmental conditions and physiological characteristics of organisms affect the δ15N value.

Specimen

  • Common mussel species as invasive animal in rivers and lakes with high information level for water pollution
  • Bioindicator in rivers and lakes
  • Fine insoluble mineral or organic particles in the water phase
  • Common brown alga of the coastal areas of the North and Baltic Sea
  • One of the most important edible mussel species common in the North and Baltic Sea
  • As the only viviparous fish in German nearshore waters, it is a bioindicator in nearshore coastal marine ecosystems.
  • Inshore, the herring gull mainly feeds from the sea: upon fish, mussels, and crabs.
  • A major primary producer in semi-natural and anthropogenic affected ecosystems.
  • A major primary producer in semi-natural and anthropogenic affected ecosystems.
  • A deciduous tree typical of ecosystems close to dense conurbations and an indicator for the characterisation of the immission situation during the vegetation period.
  • As the most dominant deciduous tree species in Central Europe, it plays a significant role in most nearly natural and also anthropogenically influenced forest ecosystems up to an altitude of 1100 m.
  • The roe deer is the most common of the larger herbivores (first order-consumer) to be found in the wild in Europe.
  • A pigeon species home in nearly every city.
  • As an organism living at ground level, it is a major driver of the decomposition of organic material (e.g. plant litter).
  • As an organism living at ground level, it is a major driver of the decomposition of organic material (e.g. plant litter).
  • Soil is livelihood and biosphere for humans, animals, plants and soil organisms. All the substances brought in are transported, transformed and/or accumulated in the soil.

Sampling area

Sampling period

1991 - 2019