Scientia Marina, Vol 74, No S1 (2010)

Coupling between the thermohaline, chemical and biological fields during summer 2006 in the northeast continental shelf of the Gulf of Cádiz (SW Iberian Peninsula)


https://doi.org/10.3989/scimar.2010.74s1047

Eleonora Anfuso
Departamento de Química Física, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz , Spain

Rocio Ponce
Departamento de Química Física, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz , Spain

Carmen Gonzalez Castro
Departamento de Oceanografía, Instituto de Investigaciones Marinas, CSIC , Spain

Jesús M. Forja
Departamento de Oceanografía, Instituto de Investigaciones Marinas, CSIC , Spain

Abstract


The coupling between the thermohaline, chemical and biological variables on the northeast continental shelf of the Gulf of Cádiz was determined during the Emigas I survey in summer 2006. Samples were collected to chemically characterize the different water types and to analyze the chlorophyll a distribution. Four different water masses were identified: North Atlantic Central Water (NACW), Surface Atlantic Water (SAW), considered a modification of NACW, and South and North Surface Waters. The highest nutrient levels were found in subsurface NACW, while surface waters were almost nutrient-depleted except in the Guadalquivir region. The isopycnal level of 26.3 kg m-3 marked the limit between nutrient-rich NACW and nutrient-poor surface waters. At the offshore stations, the subsurface cholorophyll a maximum was located at the depth of nitracline and associated with the 26.3 kg m-3 isopycnal level rather than with the pycnocline depth. At the inshore stations, chlorophyll a maxima were observed at the bottom, except for the surface maximum in the River Guadalquivir region.

Keywords


nutrients; chlorophyll a; nitracline; River Guadalquivir; Gulf of Cádiz

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