Ocean plankton. Environmental characteristics of Agulhas rings affect interocean plankton transport
Authors: Villar E, Farrant GK, Follows M, Garczarek L, Speich S, Audic S, Bittner L, Blanke B, Brum JR, Brunet C, Casotti R, Chase A, Dolan JR, d'Ortenzio F, Gattuso JP, Grima N, Guidi L, Hill CN, Jahn O, Jamet JL, Le Goff H, Lepoivre C, Malviya S, Pelletier E, Romagnan JB, Roux S, Santini S, Scalco E, Schwenck SM, Tanaka A, Testor P, Vannier T, Vincent F, Zingone A, Dimier C, Picheral M, Searson S, Kandels-Lewis S; Tara Oceans Coordinators, Acinas SG, Bork P, Boss E, de Vargas C, Gorsky G, Ogata H, Pesant S, Sullivan MB, Sunagawa S, Wincker P, Karsenti E, Bowler C, Not F, Hingamp P, Iudicone D
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Journal: Science. 2015 May 22;348(6237):1261447. doi: 10.1126/science.1261447

Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.