Modeling of nutrient dynamics in a coastal lagoon through ecosystem model

Abstract

San Quintin Bay (SQB), Baja California (30º27’N-116º00’W), is a shallow (~ 2 m depth average) hypersaline coastal lagoon strongly influenced by upwelling events in Spring and Summer. Upwelling events and tidal pumping are the main cause of temporal variability of biological and chemical parameters throughout the lagoon. In order to describe nutrient and primary producer biomass dynamics, the European Regional Seas Ecosystem Model (ERSEM) was coupled with the 1-D physical General Ocean Turbulence Model (GOTM). ERSEM, an ecosystem-model originally developed for shelf waters, was adapted to SQB conditions by adding seagrass (Zostera marina) and macroalgae (Ulva spp.) modules in a way conceptually similar to that employed in ERSEM for pelagic phytoplankton and microphytobenthos. Sensitivity analyses are allowing the adjustment of key parameters to reproduce the seasonal dynamics of primary producer biomass, as the supply of nitrate apparently determine the seasonality of Ulva and phytoplankton that reach their maxima during the upwelling season. The maximum seagrass biomass occurs in late summer (non or weak upwelling) and its productivity depends on recycled nitrogen but is mostly controlled by light availabilit