Nutrient fluxes and net metabolism in a coastal lagoon SW peninsula of Baja California.

Abstract

Fluxes of nutrients and net metabolism were estimated in coastal lagoon Magdalena Bay using LOICZ biogeochemical model. In situ data were obtained from 14 sites in the lagoon and also from a fixed site in the adjacent ocean area. Intense upwelling (February to July) and faint upwelling (August to January) were analyzed from monthly time series. The temperature, nitrite + nitrate, ammonium and phosphate within the lagoon showed significant differences (P < 0.05) between the two periods. Salinity (P = 0.408) was more homogeneous (no significantly different) due to mixing processes. During the intense upwelling period, nutrients increased in and out of the lagoon due to the influence of Transitional Water and Subartic Water transported by the California Current. However, during the faint upwelling, from August to January, the Transition Water and Subtropical Surface Water were predominant. Magdalena Bay showed denitrification processes of throughout the year as it occurred in other semi-arid coastal lagoons. It also showed a net autotrophic metabolism during intense upwelling and heterotrophic metabolism during faint upwelling. Understanding nutrient flows and net metabolism through simple biogeochemical models can provide tools for better management of the coastal zone.