Abstract
The in situ primary productivity (PP) and phytoplankton biomass (chlorophyll a concentration, Chla) of the Cabo Corrientes region, in the eastern tropical Pacific off Mexico, were studied using data from three oceanographic cruises (May and November 2002, and June 2003). The coastal region (<60 km) was found to be affected by coastal upwelling, causing phytoplankton biomass and production rates in this region to be up to two times higher than at the offshore stations. The highest surface Chla values were registered in May 2002 (>2 mg m–3), when the mean PP was 361 mgC m–2 d–1. The highest PP values were recorded in June 2003, with a mean value of 447 mgC m–2 d–1, and the lowest in November 2002, with a mean value of 200 mgC m–2 d–1. Satellite ocean color images, supported by our field data, suggest that the area off Cabo Corrientes can be characterized by three periods: (1) a relatively intense upwelling period, with high Chla and PP (spring); (2) an upwelling relaxation period, when the highest PP values of the year were recorded (late spring-early summer); and (3) a summer-fall period, with strong stratification and lowest Chla and PP values. The high PP registered for the region off Cabo Corrientes during the spring season leads us to conclude that this is an area of high fertility, similar to other rich regions in the Pacific Ocean off Mexico.
Highlights
The eastern tropical Pacific Ocean (ETP) off Mexico has been described as an area of low phytoplankton productivity as characterized by its clear waters, attributed to low chlorophyll a concentrations (Stevenson 1970)
The sea surface temperature (SST) distribution for May 2002 showed that to the north of Cabo Corrientes the temperature was very homogeneous; to the south of Cabo Corrientes there was a coastal band of cool SST, suggesting upwelling
Thermocline and mixed layer depths are very important for phytoplankton, which depend on irradiance and on the supply of nutrients to perform their two most important physiological functions: photosynthesis and growth
Summary
The eastern tropical Pacific Ocean (ETP) off Mexico has been described as an area of low phytoplankton productivity as characterized by its clear waters, attributed to low chlorophyll a concentrations (Stevenson 1970). 1) develops relatively high pigment concentrations (García-Reyes 2005, Pennington et al 2006). This feature is apparent in many images Tradicionalmente, el Océano Pacífico oriental tropical frente a México ha sido descrito como un área de baja productividad del fitoplancton, caracterizada por aguas claras atribuidas a las bajas concentraciones de clorofila a (Stevenson 1970). Imágenes satelitales de color del océano muestran que en ciertas temporadas del año (principalmente primavera) la región frente a Cabo Corrientes Aunque este caracter es aparente en muchas imágenes (e.g., fig. 12 de Pennington et al 2006), no ha sido investigada por observaciones directas
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