An
isoscape is a map of isotope distributions. It is a spatially explicit prediction of elemental
isotope ratios (δ) that is produced by executing process-level
conceptual model of elemental isotope fractionation or distribution in a geographic information system (GIS).
The word isoscape is derived from isotope land scape and was first coined by Jason B. West.
Isoscapes of hydrogen, carbon, oxygen, nitrogen, strontium and sulfur[
Open access.] have been used to answer scientific or forensic questions regarding the sources, partitioning, or provenance of natural and synthetic materials or organisms via their isotopic signatures. These include questions about Earth's element cycles, water resources, climate, archaeology, forensic science, pollution, organismal human migration patterns and food web dynamics. Isoscapes of hydrogen and oxygen isotopes, modeling precipitation,
Marine Isoscapes
Carbon Isoscapes
Scientists are able to map carbon isotope ratios (δ
13C) due to the predictable sorting of two
Stable isotope of
carbon:
13C and
12C. This sorting is known as isotope fractionation. In the ocean, δ
13C changes due to many environmental factors including water temperature, upwelling of deep ocean water,
diffusion of
Carbon dioxide from the air into the ocean and the burning of fossil fuels. Carbon fixation by
Autotroph also greatly influences δ
13C at the oceans surface. Different groups of primary producers such as
phytoplankton and
Seaweed have different strategies for fixing carbon during
photosynthesis and can further alter δ
13C. As a result carbon isoscapes in the ocean largely reflect global patterns of temperature and primary production.
Since δ13C is influenced by so many factors, isoscapes are powerful for visualizing spatial or temporal patterns and provide baseline context for applications of stable isotope analysis in marine systems. Carbon isoscapes can be used in conjunction with stable isotope analysis of marine Trophic level or Apex predator to determine the relative contributions of different primary producers to a food web or infer human migration patterns of a consumer between isotopically distinct locations.
Nitrogen Isoscapes
Like carbon, scientists are able to map nitrogen isotope ratios (δ
15N) due to the fractionation of two stable isotopes of
nitrogen:
14N and
15N. Marine nitrogen is sourced from
diffusion of
Nitrogen from the air into the ocean, freshwater run-off from continents including fertilizers and other land-based nutrients, and nitrogen fixation by primary producers like
cyanobacteria which can all influence the baseline δ
15N of the ocean in a given area. From there, nitrogen fractionation is mainly controlled through
Biological pump that utilize nitrogen, further detailed in the
Nitrogen cycle. For example the process of
denitrification and the use of NH4+
Ammonia, NO2-, and NO3-
Nitrate by marine organisms alters the δ
15N in the water. As a result, δ
15N patterns in the ocean reflect areas where nitrogen is being heavily altered through
denitrification or by organismal use within a
food web. It is important to note that seasonality influencing primary productivity also plays a role in δ
15N patterns at certain times of the year. For an example of marine nitrogen isoscape...
.
Due to the large role of biological reactions on the fractionation of nitrogen, δ15N isoscapes provide valuable information for stable isotope analysis in marine ecology. Nitrogen isoscapes provide spatial and temporal δ15N baselines that can be used to inform food web studies. Due to the alteration of nitrogen as it is passed up the food chain, stable isotope analysis of marine Trophic level can be paired with δ15N isoscapes to place a consumer at a trophic level within a food web.
See also
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Isotopic signature
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Isotope analysis
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Isotope geochemistry
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Stable isotope composition of amino acids
Notes
