Resumen del producto

Sixteen monthly cruises were carried out at a station 6.5 km t o the NW of the mouth of Magdalena Bay (Mexico) to study the temporal variability of phytoplankton biomass and primary produ ction rates, and the response of phytoplankton to the prevailin g hydrographic characteristics. During each cruise, temperature and salinity w ere measured in the water column, and discrete samples were col lected to mea- sure inorganic nutrient concentrations (nitrate, phosphate, and silicate) and chlorophyll a content (as a proxy for phytoplankton biomass); in addition, in situ incubations were performed to estimate primary production (PP) rates using the 14 C technique. During spring and early summer (March–July), the water column at the study site was cold (14.4 ºC at 80 m depth and 17.7 ºC at the surface) and well mixed, w ith high nutrient concentrations (nitrate = 6.39 µM, phosphate = 0.91 µM, and sil icate = 11.87 µM) at the surface, typical of intense upwelling systems. On the contrary, from August to February the water column was stra tified (23.5 ± 3.2 ºC above the thermocline and 17.0 ± 1.7 ºC a t 80 m depth) and had low nutrient concentrations (nitrate = 3.90 µM, phospha te = 0.47 µM, and silicate = 10.30 µM) at the surface. Phytopla nkton abun- dance, chlorophyll a concentration, and PP rates in the euphotic zone were higher d uring the upwelling season, with maximum cell density of 1.7 × 10 6 cells·L –1 (nanoplankton fraction), integrated chlorophyll a content of 231 mg·m –2 , and integrated PP rates of 553 mg C·m –2 ·h –1 ). Abundance of cells

Palabras clave: biomass; Primary productivity; hydrography; Coastal Zone; Magdalena Bay

Para obtener una copia del documento contacta la personal de la biblioteca a través del correo bibliocicimar{a}ipn.mx