Regional response of the coastal aquifer to Hurricane Ingrid and sedimentation flux in the Yax Chen cave system (Ox Bel Ha) Yucatan, Mexico

Coastal karst aquifers are an important source of potable water which can be affected by external forcing on various temporal and spatial scales (e.g. sea-level) but there is a lack of long-term data to understand their response. Sediment cores and their proxy records have been used in lakes and oceans to assess past environmental change, but haven't been extensively applied to anchialine caves where there is less known about the physical, biological and chemical processes affecting sedimentation. Over fifty sediment traps were placed in Yax Chen which is part of the Ox Bel Ha cave system near Tulum, Mexico and four water level sensors were placed in two additional cave systems (Ponderosa, Sac Actun) for comparative water table fluctuations. Data collected over the past three years (2011-2013) captured seasonal and spatial sediment flux including the effect of an intense rainfall associated with Hurricane Ingrid (September 18, 2013). The data indicates that sediment deposition was controlled by cenote size and the presence of mangrove. Areas upstream of Cenote Gemini had negligible sediment accumulation as there were few cenotes and the terrain is dominated by lowland tropical forest, while areas downstream from Cenote Gemini were dominated by mangrove forests and larger cenotes which resulted in higher sediment accumulation rates (0.014 vs. 0.22 mg/cm2/day). Bi-annual sedimentation rates in 2013-2014 were higher in the months after the rainy season (0.2 vs. 0.5 mg/cm2/day) indicating that cenote productivity was likely controlling sedimentation. Mangrove areas with their peat accumulations occlude the porous karst causing funneling of nutrient rich rainwater into the sunlit cenotes enhancing primary productivity and sedimentation in downstream areas. Hurricane Ingrid had little effect on the yearly sediment rate even though water table fluctuations were high (0.7 m) compared to the yearly values (0.3 m). This likely is due to water bypassing the cenotes with little residence time to enhance productivity and sedimentation in downstream areas.