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Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect
Ist Teil von
Coral reefs, 2015-03, Vol.34 (1), p.329-338
Ort / Verlag
Berlin/Heidelberg: Springer Berlin Heidelberg
Erscheinungsjahr
2015
Link zum Volltext
Quelle
SpringerNature Journals
Beschreibungen/Notizen
We tested the hypothesis that the nitrogen (N) isotopic signature (δ
15
N) of coral skeletal organic material (CS-δ
15
N) matches that of the coral tissue and also reflects the δ
15
N of water column fixed N, such that CS-δ
15
N can be used as a proxy for spatio-temporal oceanic N isotope distributions. Strong correlations between the δ
15
N of skeletal organic material and that of coral tissue in two scleractinian corals (
Porites lutea
and
Favia stelligera
) across a tropical coral reef flat support the use of CS-δ
15
N in reconstructing coral biomass δ
15
N changes. However, we observed a consistent and species-specific offset between the coral tissue δ
15
N and the skeletal CS-δ
15
N. As such, the CS-δ
15
N is not an absolute measure of tissue δ
15
N. The CS-δ
15
N of both coral species and three species of macroalgae increased across the reef flat in response to a natural gradient in water column δ
15
N. There was an apparent dampening of the water column δ
15
N gradient recorded in the coral tissue δ
15
N and the CS-δ
15
N, possibly caused by shifting trophic status of corals across the reef flat. The CS-δ
15
N therefore appears to robustly reflect the δ
15
N of the coral tissue, and the coral system is responsive to the δ
15
N of the water column N pools. The distortion of the true water column δ
15
N by corals requires further investigation and is an important consideration for the use of coral skeletons in temporal reconstructions of water column δ
15
N.