A 2-decade (1988–2009) record of diatom fluxes in the Mauritanian coastal upwelling: impact of low-frequency forcing and a two-step shift in the species composition

Abstract. Eastern boundary upwelling ecosystems (EBUEs) are among the most productive marine regions in world's oceans. Understanding degree of interannual to decadal variability Mauritania system is crucial for prediction future changes primary productivity and carbon sequestration Canary Current EBUE as well similar environments. A multiyear sediment trap experiment was conducted at mooring site CBmeso (“Cape Blanc mesotrophic”, ca. 20∘ N, 20∘40′ W) highly coastal waters off Mauritania. Here, we present results on fluxes diatoms species-specific composition assemblage time interval between March 1988 June 2009. The temporal dynamics diatom populations allows proposal three main intervals: (i) early 1988–late 1996, (ii) 1997–1999, (iii) 2002–mid Atlantic Multidecadal Oscillation (AMO) appears be an important driver long-term population. AMO-driven trend interrupted by occurrence strong 1997 El Niño–Southern (ENSO). extraordinary shift relative abundance benthic May 2002 suggests strengthening offshore advective transport within uppermost layer filament subsurface deeper bottom-near layers. It hypothesized that dominance response community intensification slope shelf poleward undercurrents. This followed warm phase AMO associated Meridional Overturning Circulation. Transported valves (siliceous remains) from shallow Mauritanian into bathypelagic should considered calculation model experiments bathy- pelagic nutrients budgets (especially Si), burial diatoms, paleoenvironmental signal preserved downcore sediments. Additionally, our 1988–2009 data set contributes characterization impact low-frequency climate forcings northeastern will especially helpful establishing scientific basis forecasting modeling states its changes.