Characterization of physical variables at La Escollera, a humanmade coastal lagoon in Santa Marta, Colombian Caribbean

Abstract

Coastal lagoons are a focus of primary production and a refuge for biodiversity due to their relative confinement and low depth. La Escollera is a human-made coastal lagoon in El Rodadero, Santa Marta (Colombian Caribbean), excavated in the early 1980s
to hold a marina and its fringes planted with mangroves. To generate a baseline of physical variables that contribute to the understanding of water circulation and its influence on ecosystem attributes, salinity, temperature, sea level and light penetration data are routinely obtained through electronic recorders and handheld sensors. Salinity and temperature data from January 2017 to February 2018 followed the seasonal pattern of the open sea in the Santa Marta area, alternating between lower temperature (minimum of 24.6 °C) and higher salinity (maximum of 38.9) in the dry season and coastal upwelling (December to April), an between higher temperature (maximum 34.7 °C) and lower salinity (< 35) in the rainy season (May to November), with the lowest salinity values after persistent rains (minimum 15.1). The water column is generally well mixed and stratified after heavy showers in the rainy season (mixing rapidly in hours or days). This seems to be mainly due to tidal exchange with the sea, the tide oscillating from +0.37 to –0.31 m (maximum range 0.68 m [one-year
data]), and following the regular astronomical pattern of mixed tides in the Caribbean. Lagoon waters are regularly green and of varied transparency except during heavy rains, after which they become brownish. Vertical light extinction is generally high and not very variable (2-6.5 % cm-1), but the light frequently reaches the bottom, which allows the presence of benthic macroalgae in some portions of the lagoon.