The impact of grazing, resource competition and light on prokaryotic growth and taxonomic composition in subtropical and tropical surface waters was studied through 10 microcosm experiments conducted between 30°N and 30°S in the Atlantic, Pacific and Indian oceans. Under natural sunlight conditions, significant changes in taxonomic composition were only observed after the reduction of grazing by sample filtration in combination with a decrease in resource competition by sample dilution. Sunlight exposure significantly reduced prokaryote growth (11±6%) and community richness (14±4%) compared to continuous darkness but did not significantly change community composition. The largest growth inhibition after sunlight exposure occurred at locations showing deep mixed layers. The reduction of grazing had an expected and significant positive effect on growth, but caused a significant decrease in community richness (16±6%), suggesting that the coexistence of many different OTUs is partly promoted by the presence of predators. Dilution of the grazer-free prokaryotic community significantly enhanced growth at the level of community, but consistently and sharply reduced the abundance of Prochlorococcus and SAR11 populations. The decline of these oligotrophic bacterial taxa following an increase in resource availability is consistent with their high specialization for exploiting the limited resources available in the oligotrophic warm ocean. This article is protected by copyright. All rights reserved.
|Original language||English (US)|
|Number of pages||15|
|State||Published - Mar 20 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This study was supported by the by the Spanish Ministerio de Ciencia e Innovación through project Consolider-Ingenio Malaspina 2010 (CSD2008-00077). Sample sequencing was funded by grant M’OMICS-MALAN (CTM2011-15461-E PI) of the Spanish Ministerio de Economía y Competitividad. We thank our fellow scientists, chief scientists, and the crew of BIO Hespérides for their work, Carlos M. Duarte for the conception and coordination of the Malaspina 2010 Circumnavigation Expedition, the members of the physical oceanography party for collecting, calibrating, and processing the CTD data, the providers of chlorophyll a(Marta Estrada) and nutrient data (Dolors Blasco and Montse Vidal), and the people involved in the experimental set-up (Hugo Sarmento, Ana Gomes, Francisco M. Cornejo-Castillo, Laura Alonso-Sáez, Victor Hernando, Irene Forn, Joaquín Valencia and Teresa Serrano).