Effect of turbulent kinetic energy on the spatial distribution of chlorophyll a in a small coastal lagoon

Abstract

In order to observe the effect of turbulent kinetic energy (TKE) on the spatial distribution of chlorophyll a, four spatial variations were analysed (two during high and two during low tide) on 15 and 16 April, 1989 in Puerto Don Juan. Observations were made of buoy drifts and tidal height, and surface water samples were taken at 20 stations to determine chlorophyll a concentration in each variation. A pattern for ebb conditions is inferred, which shows a direct relationship between a smooth bottom slope and a high concentration of chlorophyll a. For flow conditions, the relationship is inverse. We suggest that the higher concentrations of chlorophyll a are due to a simple mechanical process of accumulation in areas with certain morphological characteristics that attenuate the TKE. That is, the speed of transport of the phytoplankton that enters the lagoon decreases on reaching areas of low TKE, causing stagnation of the particles. This long-term pattern produces high concentrations in the inner part of the lagoon, resulting in higher concentrations of chlorophyll a at the innermost stations. When the tide begins to ebb, these patches of high concentration are transported to the outer part of the lagoon.