Phytoplankton and primary production characteristics at selected sites in the geostrophic Almeria-Oran front system (SW Mediterranean Sea)

Mesoscale subduction at the Almeria–Oran front

“…This suggests that the frontal-jet system exhibits a fertilising effect on the otherwise oligotrophic waters of the Alboran Sea. Such a frontal enhancement is thought to result from the vertical input of nutrients caused by upwelling (Videau et al, 1994;Fiala et al, 1994;Claustre et al, 1994) and this idea is supported by L'Helguen et al…”

“…Diatom and nanoplankton abundance, chlorophyll content and primary production have been observed to be higher in the jet, either from satellite data (Arnone and La Violette, 1986;Lohrenz et al, 1988;Arnone et al, 1990) or in-situ shipboard data (Prieur et al, 1993;Videau et al, 1994;Fiala et al, 1994). This suggests that the frontal-jet system exhibits a fertilising effect on the otherwise oligotrophic waters of the Alboran Sea.…”

“…Frontal enhancement of phytoplankton populations has been observed at the AlmeriaOran front (Lohrenz et al, 1988;Prieur and Sournia, 1994;Videau et al, 1994;Fiala et al, 1994). Diatom and nanoplankton abundance, chlorophyll content and primary production have been observed to be higher in the jet, either from satellite data (Arnone and La Violette, 1986;Lohrenz et al, 1988;Arnone et al, 1990) or in-situ shipboard data (Prieur et al, 1993;Videau et al, 1994;Fiala et al, 1994).…”

“…(1992) and Videau et al (1994) who observed a shallower nitracline in frontal waters than in Mediterranean waters (18-30 m and 30-60 m respectively). Numerical simulations undertaken by Zakardjian and Prieur (1994) support this hypothesis of production enhancement through vertical advection of nutrients.…”

“…This increase in biomass is thought to result from various mechanisms including: vertical motion affecting the light field encountered by phytoplankton (Lillibridge, 1990); mixing of phytoplankton and nutrients along the frontal interface (Yoder et al, 1983;McClain et al, 1990;L'Heguen et al, 1993); death and subsequent remineralisation of foreign populations supporting higher endemic species growth, and along front advection of populations in the presence of an along front gradient in other environmental parameters (Olsen et al, 1994). In ageostrophic fronts, where crossfrontal secondary circulation exists, this production can be exported downwards along sloping isopycnals (Dewey et al, 1991;Gorsky et al, 1991;Videau et al, 1994).…”