Spatial and temporal variations in physicochemical characteristics of water and sediment in the Yalahau coastal lagoon, Quintana Roo

Abstract

In the Yalahau coastal lagoon, Quintana Roo, we analyzed spatial (Outer, Sea-lagoon, South, and North zones) and temporal weather-season variations (rainy, nortes, and dry), in physicochemical characteristics of water and sediment. The salinity, soluble reactive silicate (SiRS), and sediment grain size were the variables with the highest spatial and temporal variability: (1) The Outer zone is characterized by marine salinity with little temporal variation, low concentrations of SiRS (<11 ?M), and predominantly fine sands; (2) The Sea-lagoon zone has the lowest mean salinity (35.5 psu) and little temporal variation, SiRS concentrations of about 10-15 ?M in rainy, and nortes that increased four times in dry, and predominantly coarse sands. (3) The South zone is characterized by mixoeuhaline conditions in nortes and hyperhaline conditions during rains, SiRS concentrations of about 15-20 ?M in rains and nortes that increased twofold in dry and predominantly coarse sands; (4) The North zone is characterized by a permanent trend to hyperhaline conditions, concentrations of SiRS > 10 ?M during the three seasons that increased up to six times in dry weather, when increased concentrations of ammonium and soluble reactive phosphorus were also observed, and predominantly fine sand. The relatively pristine condition of this protected area suggests that natural factors such as the presence of Thalassia testudinum meadows, the magnitude of freshwater inputs, the decomposition of organic matter, and the entry of exogenous nutrients (e.g., seabird droppings) have a great influence on the environmental heterogeneity of the Yalahau lagoon.