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Ritmos circadianos y perfiles verticales en un ecosistema litoral somero
Jesús M. Forja, Abelardo Gómez-Parra, and Julián Blasco

CIRCADIAN RHYTHMS AND VERTICAL PROFILES IN A SHALLOW MARINE ECOSYSTEM. - Circadian rhythms and vertical profiles of dissolved oxygen, pH, alkalinity, nutrients (NH4+ and SiO2) and other complementary parameters were studied in the water column of a salt pond located in the south of Cadiz Bay (SW Spain). This study was carried out during the spring and summer of 1985. In spring, vertical gradients of parameters analyzed have little importance and the daily evolution of their values are uniform in the water column, and independent of the degree of salt pond water renewal. In summer, oxygen concentration is very variable, ranging between anoxic conditions at the bottom in the early hours and over-saturation values of 180 lang=EN-GB 8.0pt;font-family:Arial'>% at the surface after noon. Gradients of up to -3.6 mg O2 l-1 m-1 1.0pt'> in only 2.5 m in depth have been detected. These data, such as the spatial-temporal evolution of pH and NH4+ concentration, indicate the importance of benthic regeneration of nutrients in these ecosystems. A model for prediction of dissolved oxygen concentration and pH values as a function of depth and day-time is proposed. The model is as valid for spring as for summer and the values of its parameters related to the importance of the main processes which affect the dissolved gas content in the ecosystem

Keywords: dissolved oxygen, pH, nutrients, vertical profiles, circadian rhythms, salt-ponds, shallow ecosystems, Bay of Cadiz, SW Spain.
Contents of this volume Sci. Mar. 54(1) : 9-18 Back PDF
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