ORIGIN AND EVOLUTION OF CORAL REEFS: ONSHORE AND OFFSHORE FRESHWATER CONNECTIVITY

Coastal coral reefs and submerged mesophotic carbonate buildups form at, and are dependent upon fluids seeping through the seabed. The seeping fluids at the seabed, sometimes originating from submarine groundwater discharge (SGD) from coastal aquifers that extend offshore, may provide pulses of nutrients and organic nutriments. The pulses are related to storms, hurricanes and seasonal torrential rains magnified at the coastal zone. Depending on the biogeochemical characteristics of the SGD, diagenetic mineral precipitation occurs and cementation forms a solid substrate adequate for colonisation and development of coral, sponges, or bioherm forming organism, etc. Due to watershed disturbance, excessive water use or coastal development, this source of nutrients may be shut off but the carbonate buildup may continue as an “Ahogado” reef or mesophotic reefs as extensive has the seepage may have been and as tall as the building up may reach by the migration of nutrients. We propose that SGD can explain the development of bordering coral reefs. Over time, the bordering reef may form a reef platform on the continental shelf and eventually create an isle that can collect rain. Rain then provides a local source of SGD with nutrients at the reef lagoon and allow the coral reef to become independent of SGD sourced from onshore. The case study of the Veracruz coral reefs in the Gulf of Mexico is presented.