Water column characterization of anchialine caves in Quintana Roo, Mexico

Abstract

Water column characteristics of three coastal cave systems in Quintana Roo, Mexico on the Yucatan Peninsula were profiled from January 1996 to July 1997. A Hydrolab Data Sonde 3 Multiprobe Logger was used to acquire in situ water column data on temperature, salinity, dissolved oxygen, and pH of the caves. Water columns were divided into three zones, brackish, transition, and saline, and a new method was employed to define these boundaries by using "best it" calculations and subsequent regression coefficients for comparisons. Profiled Hydrolab data displayed the striking and perennially stratified nature of these cave systems while statistical analyses revealed their highly dynamic character. Temperature profiles remained stable and persistent throughout the study. In these systems the presence of a thermal discontinuity or thermocline, is the norm. Salinity profiles exhibited sharp density gradients, or haloclines, one to three meters in thickness. Dissolved oxygen concentrations were consistently low and revealed negative heterograde oxygen curves, otherwise known as oxygen minima, residing at the transition zone. Hydrogen ion concentrations (pH) varied and also displayed a marked decrease at the transition zone. Transition zone thickness changed considerably over time and from system to system. Statistical analysis indicated a significant difference in temperature, salinity, DO, pH, and transition zone depth from profile to profile and between dry and rainy seasons.