Abstract
Abstract. The organic carbon fluxes mediated by planktonic communities in two cyclonic eddies (CEs) and two anticyclonic eddies (AEs) at the Canary Eddy Corridor were studied and compared with the dynamics in two far-field (FF) stations located outside the eddies. We observed favorable conditions and signs for upwelling at the center of CEs and for downwelling and mixing at the centers of AEs. CEs were characterized by a higher concentration of nutrients and the highest concentration of chlorophyll a (chl a), associated with the highest abundance of microphytoplankton and diatoms. AEs displayed concentrations of chl a values and nutrients similar to those at the FF stations, except for the highest ammonium concentration occurring at AE and a very low concentration of phosphorus at FF stations. AEs were transient systems characterized by an increasing abundance of picophytoplankton and heterotrophic bacteria. While primary production was similar between the systems, the production of dissolved organic carbon (PDOC) was significantly higher in the AEs. Phytoplankton cell mortality was lowest in the CEs, and we found higher cell mortality rates at AE than at FF stations, despite similar chl a concentration. Environmental changes in the AEs have been significantly prejudicial to phytoplankton as indicated by higher phytoplankton cell mortality (60% of diatoms cells were dead) and higher cell lysis rates. The adverse conditions for phytoplankton associated with the early-stage anticyclonic systems, mainly triggered by active downwelling, resulted in higher cell mortality, forcing photosynthesized carbon to fuel the dissolved pool.
Highlights
The dynamics of mesosHcalyededrdoielsoegxeyrtaprnofdound influences on the vertical fluxes of oErgaanritchmSattyers, nteutmrients and carbon (Owen, 1981; 2001; Mathis eAtrıaslt.e,g2u0i 0e7t;aAl.,loS2n0sc0o3i-e;GnMoncazreatilneszanetdRichards, al., 2010; Benitez-Nelson and McGillicuddy, 2008) and may modulate the oceanic vertical pump (Oschlies and Garcon, 1998)
Three contrasting zones were characterized during the cruise, the cyclonic and anticyclonic oceanic eddy (CE and anticyclonic eddies (AEs)) fields located at the lee of the Canary Islands and the far-field off the archipelago
It has been suggested that the counter-paired cyclonic and anticyclonic eddies generated by the Canary Current and trade wind perturbation by the Canary Islands influence biological processes in the NE Atlantic region (Arıstegui et al, 1997; Arıstegui and Montero, 2005; Gonzalez-Davila et al, 2006; Sangraet al., 2009)
Summary
The dynamics of mesosHcalyededrdoielsoegxeyrtaprnofdound influences on the vertical fluxes of oErgaanritchmSattyers, nteutmrients and carbon (Owen, 1981; 2001; Mathis eAtrıaslt.e,g2u0i 0e7t;aAl.,loS2n0sc0o3i-e;GnMoncazreatilneszanetdRichards, al., 2010; Benitez-Nelson and McGillicuddy, 2008) and may modulate the oceanic vertical pump (Oschlies and Garcon, 1998). Cyclonic eddies (CEs) tend to promote the biological pump by increasing nutrient supply, thereby enhancing the primary production (Smith et al., 1996; Garcon et al, 2001; McGillicuddy et al, 2007) and by favoring larger phytoplankton cells (Rodrıguez et al, 2001; Vaillancourt et al, 2003). On the basis of a submesoscale resolution quasi-synoptic temperature section crossing the Gran Canaria wake, Basterretxea et al (2002) observed evidence of downward/upward lineal Ekman surface-layer pumping coinciding with strong anticyclonic/cyclonic wind shear regions. Additional studies have been initiated at this zone to better understand the implication of counter-paired cyclonic and anticyclonic eddies for biological processes and to address their influence in carbon fluxes. Since anticyclonic structures can be long-lived coherent structures lasting several months (Sangraet al., 2005, 2009), the magnitude and the efficiency of biological processes such as production and health status of communities can be affected for extended periods and may have significant implications in carbon fluxes
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