Nutrient and phytoplankton dynamics in a coastal lagoon strongly affected by coastal upwelling

Saúl Álvarez-Borrego

doi:10.7773/cm.v30i1a.2510

Abstract

San Quintín Bay is a coastal lagoon influenced by the California Current System (CCS) coastal upwelling. Upwelling brings nutrient-rich waters near the bay mouth and tidal currents propagate those waters throughout the bay. Upwelling intensification and relaxation events occur with a period of ~2 weeks, possibly due to the variability of circulation of the CCS. Off San Quintín, the CCS has an offshore component of the flux, causing upwelling intensification events as strong as off Point Conception (34.5°N), with high phytoplankton productivity. At the lagoon's mouth, upwelling is the main cause of variability for all physicochemical properties except temperature. Semi-diurnal tides are the main cause of variability for temperature. Nutrient remineralization at the sediments and turbulence induced by tidal currents and wind waves increase nutrient concentrations in the lagoon. At the heads of the bay, phytoplankton abundance was ten-fold lower, productivity and chlorophyll concentrations were three-fold lower, chlorophyll content per cell was three-fold higher, and turbidity was higher than at the mouth. The few available data suggest the hypothesis that the effect of ENSO events on phytoplankton biomass depends on the interdecadal regime shifts in the northeastern Pacific. At the lagoon's mouth and adjacent ocean, summer salinities as low as 32.4 suggest the arrival of water parcels that originate in the north, possibly the Columbia River estuarine plume.

Highlights

San Quintin Bay is a coastal lagoon where salinity increases from the mouth to the inner reaches due to the high evaporation rate and almost nil freshwater input from rainfall and surface runoff (Chavez-de-Nishikawa and AlvarezBorrego, 1974; Alvarez-Borrego et al, 1975)
Kjerfve' s (1994) classification, it is a restricted lagoon, with a permanent single connection to the ocean and tides that cooscillate with tides in the coastal ocean with little reduction of amplitude inside the lagoon. It is influenced by coastal upwelling of the California Current System (CCS), mainly in late spring and summer
The uniqueness of the oceanic area adjacent to San Quintin Bay is that the effect of the oceanic circulation is added to that of the winds to produce very intense upwelling

Summary

Introduction

San Quintin Bay is a coastal lagoon where salinity increases from the mouth to the inner reaches due to the high evaporation rate and almost nil freshwater input from rainfall and surface runoff (Chavez-de-Nishikawa and AlvarezBorrego, 1974; Alvarez-Borrego et al, 1975). With relation to the 197311974 sampling, only January and July data were used to show the main seasonal and spatial variations, from three regions: the lagoon's mouth and the two internal extremes, Falsa Bay and San Quintin Bay. In summer, water temperature increased from the mouth to the inner reaches, with highest temperatures in the eastern arm.

Results

Conclusion