Publication Date:
2016-10-16
Description:
Studies of the nitrogen cycle in the ocean generally assume that the distribution of the marine diazotroph, Trichodesmium , is restricted to warm, tropical and sub-tropical oligotrophic waters. Here we show evidence that Trichodesmium are widely distributed in the North Atlantic. We report an approximately five-fold increase during the 1980s and 1990s in Trichodesmium presence near the British Isles with respect to the average over the last 50 years. A potential explanation is an increase in the Saharan dust source starting in the 1980s, coupled with changes in North Atlantic winds that opened a pathway for dust transport. Results from a coarse-resolution model in which winds vary but iron deposition is climatologically fixed, suggest frequent nitrogen limitation in the region and reversals of the Portugal current, but it does not simulate the observed changes in Trichodesmium. In addition, modeling results suggest frequent nitrogen limitation in the region and possible reversals of the Portugal current. These factors, when coupled with iron fertilization, could benefit Trichodesmium . Our results suggest that Trichodesmium may be capable of growth at temperatures below 20 o C and challenge assumptions about their latitudinal distribution. Therefore, we need to reevaluate assumptions about the temperature limitations of Trichodesmium and the dinitrogen (N 2 ) fixation capabilities of extra-tropical strains, which may have important implications for the global nitrogen budget.
Print ISSN:
0886-6236
Electronic ISSN:
1944-9224
Topics:
Biology
,
Chemistry and Pharmacology
,
Geography
,
Geosciences
,
Physics
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