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Fueling plankton production by a meandering frontal jet: a case study for the Alboran Sea (Western Mediterranean).

Oguz T, Macias D, Garcia-Lafuente J, Pascual A, Tintore J - PLoS ONE (2014)

Bottom Line: Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet.The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data.The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.

View Article: PubMed Central - PubMed

Affiliation: SOCIB, Balearic Islands Coastal Ocean Observing and Forecasting System, Palma de Mallorca, Spain; Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin, Turkey.

ABSTRACT
A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15-20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.

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Cross section of biological tracers.Vertical cross-sections of (a) nitrate concentration, (b) phytoplankton biomass, and (c) zooplankton biomass expressed in mmol N m−3 along the transect shown in Fig. 2d.
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pone-0111482-g007: Cross section of biological tracers.Vertical cross-sections of (a) nitrate concentration, (b) phytoplankton biomass, and (c) zooplankton biomass expressed in mmol N m−3 along the transect shown in Fig. 2d.

Mentions: The zonal nitrate cross-section for the transect shown in Fig. 2d indicated maximum concentrations of 3.0 mmol N m−3 and 2.0 mmol N m−3 at the northwestern and eastern flanks of the WAG, respectively (Fig. 7a). They occupied subsurface levels centered at 25 km and 140 km from the origin in Fig. 7a. The upward compression of the nitracline in these regions indicated a higher nitrate input towards the surface by the relatively high vertical velocities (Fig. 4c). This feature also developed with a slightly weaker efficiency around the EAG periphery (centered at 190 km and 290 km). Relatively high concentrations of approximately 1.5 mmol N m−3 within the central parts of the WAG and 1.2 mmol N m−3 within the EAG at depths between 75 and 175 m were likely related to the isopycnal subduction of upwelled nutrients, as well as those arising from the organic matter recycling. On the contrary, the narrow cyclonic zone confined between the eastern flank of the WAG and the western flank of the EAG reflected the strong subduction associated with the downward motion, leading to a pronounced reduction in nitrate concentrations (Fig. 4c). This region was also deficient in phytoplankton biomass, whereas its higher concentrations coincided with those of nitrate in the frontal regions (Fig. 7b). The phytoplankton biomass was much higher and extended deeper around the WAG than around the EAG, which was consistent with the nitrate transect.


Fueling plankton production by a meandering frontal jet: a case study for the Alboran Sea (Western Mediterranean).

Oguz T, Macias D, Garcia-Lafuente J, Pascual A, Tintore J - PLoS ONE (2014)

Cross section of biological tracers.Vertical cross-sections of (a) nitrate concentration, (b) phytoplankton biomass, and (c) zooplankton biomass expressed in mmol N m−3 along the transect shown in Fig. 2d.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4221033&req=5

pone-0111482-g007: Cross section of biological tracers.Vertical cross-sections of (a) nitrate concentration, (b) phytoplankton biomass, and (c) zooplankton biomass expressed in mmol N m−3 along the transect shown in Fig. 2d.
Mentions: The zonal nitrate cross-section for the transect shown in Fig. 2d indicated maximum concentrations of 3.0 mmol N m−3 and 2.0 mmol N m−3 at the northwestern and eastern flanks of the WAG, respectively (Fig. 7a). They occupied subsurface levels centered at 25 km and 140 km from the origin in Fig. 7a. The upward compression of the nitracline in these regions indicated a higher nitrate input towards the surface by the relatively high vertical velocities (Fig. 4c). This feature also developed with a slightly weaker efficiency around the EAG periphery (centered at 190 km and 290 km). Relatively high concentrations of approximately 1.5 mmol N m−3 within the central parts of the WAG and 1.2 mmol N m−3 within the EAG at depths between 75 and 175 m were likely related to the isopycnal subduction of upwelled nutrients, as well as those arising from the organic matter recycling. On the contrary, the narrow cyclonic zone confined between the eastern flank of the WAG and the western flank of the EAG reflected the strong subduction associated with the downward motion, leading to a pronounced reduction in nitrate concentrations (Fig. 4c). This region was also deficient in phytoplankton biomass, whereas its higher concentrations coincided with those of nitrate in the frontal regions (Fig. 7b). The phytoplankton biomass was much higher and extended deeper around the WAG than around the EAG, which was consistent with the nitrate transect.

Bottom Line: Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet.The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data.The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.

View Article: PubMed Central - PubMed

Affiliation: SOCIB, Balearic Islands Coastal Ocean Observing and Forecasting System, Palma de Mallorca, Spain; Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin, Turkey.

ABSTRACT
A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15-20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive.

Show MeSH
Related in: MedlinePlus