Arctic food-web carbon is going isotopically light
Across 17 Arctic regions, water-column POC δ13C fell 0.149‰ per year—far faster than DIC/CO2 (0.011‰/yr)—and seal and whale tissues tracked the decline.
Source
Temporal and spatial trends in marine carbon isotopes in the Arctic Ocean and implications for food web studies
What they did
Authors compiled marine δ13C of POC (water and ice), DIC, dissolved CO2, and mammal teeth/baleen, then fit spatial ANOVAs and decadal linear trends.
What they found
Shelves were 13C-enriched versus basins; ice POC was often heavier than water POC. Combined-region DIC/CO2 declined 0.011‰/yr (1977–2014) while POC water declined 0.149‰/yr (1986–2013). Mammal δ13C also fell (e.g., ringed seals −0.046‰/yr).
The limits
What it doesn't show
Compiled opportunistic samples are summer-biased; diet shifts could contribute to mammal trends, so Suess+ice-loss is not the only possible driver.
Key terms
- δ13C-POC
- Carbon isotope ratio of particulate organic carbon at the food-web baseline.
- Suess effect
- 13C depletion of DIC from adding 13C-poor fossil-fuel CO2.
- POC ice vs water
- Organic carbon from sea-ice algae versus phytoplankton.
- Baseline
- Isotopic starting point that consumers inherit up the food web.
- Arctic shelves vs basins
- Shallow inflow/interior shelves versus deep central Arctic.
Flashcards
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POC-water δ13C decline was about:
Common questions
How fast did POC-water δ13C fall?
0.149 ± 0.020‰ per year (1986–2013).
DIC/CO2 rate?
0.011‰ per year.
Ice vs water POC?
Ice POC generally 13C-enriched.
Why it matters for food webs?
Diet studies must correct for a changing baseline, not only DIC Suess.
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