Publication Date:
2016-09-22
Description:
Dissolved organic nitrogen (DON) potentially plays a major role in sustaining the high productivity and biological diversity of coral reefs. However, data are scarce regarding sources and sinks of DON. This study, for the first time, determined the N-15 isotopic composition of total dissolved nitrogen (delta N-15(TDN)), reflecting the isotopic signature of DON, in the water column over a coral reef. The uniformity in delta N-15(TDN) during high tide (3.2 +/- A 0.3 aEuro degrees) indicated that the DON was mainly derived from offshore waters. In contrast, higher spatial heterogeneity of delta N-15(TDN) (3.1 +/- A 0.9 aEuro degrees) and DON concentrations during low tide indicated the existence of local DON sources patchily distributed over the reef. Low delta N-15(TDN) values located mid-reef were indicative of DON release from organisms that obtained their N via N-2 fixation, whereas high delta N-15(TDN) appeared to reflect localized release of DON by organisms exposed to dissolved inorganic nitrogen with elevated N-15, such as from terrestrial and offshore inputs. Collectively, the results highlight the importance of spatial patterns in DON release from reef communities in the N cycling of coral reefs.
Type:
Article
,
PeerReviewed
Format:
text
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