VARIATIONS IN PHYSICO-CHEMICAL PARAMETERS AND DISSOLVED TRACE METALS IN WATERS OF MANGROVE FRINGED BAHIA MAGDALENA LAGOON, BAJA CALIFORNIA SUR, MEXICO

Forty two samples were collected at the surface and bottom water profiles along 5 transects from the Bahia Magdalena lagoon, Baja California Sur in order to evaluate the geochemical processes and measure the environmental quality of the region. The region is ecologically significant due to the presence of large numbers of sea lions and grey whales. Physico chemical parameters (pH, dissolved oxygen, conductivity, temperature and ORP) were measured in every sampling station using the Hannah instrument. The results suggest that the characteristics of water vary with each sampling station based on the in-situ environmental conditions and the effect of fringing mangrove ecosystems surrounding the lagoon. Dissolved trace metals (Fe, Mn, Cr, Cu, Co, Pb, Ni, Zn, Cd As, Hg) in the surface and bottom water samples were analyzed using Atomic absorption spectrometry. The results indicate that minor enrichment of dissolved metals could be observed close to the shore line and in the regions with lower depth. Presence of hydrothermal vents and large mineral deposits also play a role in increasing the dissolved metal concentration in the aquatic environment. High concentrations of Ni and As are attributed to the local geology and phosphate deposits. In general, the region witnesses minor quantities of dissolved trace metals due to dispersion and high intense interaction with the open sea. The results were also compared with other studies to understand the enrichment pattern in this side of the pacific coast which experiences various geothermal activities.