The Riviera Maya is known for its beautiful coral reefs and also for its mysterious cenotes, these two defining characteristics of the area play important roles in the tourism industry and have very distinct assets: On one side, coral reefs provide a home to a large number of marine organisms, including recreational and commercial valuable species. Not to mention the year round tourism that visits the Riviera Maya with the sole purpose of exploring the underwater ecosystem and, most of all, catching and eye of the world famous megafauna, such as the Akumal turtles and the whale sharks in Isla Mujeres. On the other hand we have cenotes, which are essentially an entrance to underwater cave systems. Cenotes are known for their crystal clear waters, their overall breathtaking beauty, and their cultural meaning, all of which attract tourists from over the world. In the Mayan civilization cenotes were considered sacred places where the Mayans communicated with their Gods. In addition, they also acted as kind of oasis in a dessert, providing a source of freshwater in remote areas of the luscious jungle. Nonetheless, cenotes are also of great interest amongst scientists and explorers, but because of the physical challenges that constitute mapping underwater cave systems, they remain largely unexplored.
How are cenotes and coral reefs connected?
As I mentioned before, cenotes are part of underwater cave systems and these systems eventually discharge water into the ocean through the ground. Now, think about the last time you went snorkeling. Did you ever feel pockets of colder or warmer water? Did your visibility underwater ever seem to worsen very suddenly, almost looking like there was oil in the water? Well, if you have ever experienced this while snorkeling in the Riviera Maya then it is very possible that you found an area where the cenote meets the ocean! This phenomenon is called water stratification and is caused by the mixing of, cold and fresh, cenote water with, warm and salty, ocean water.
What causes water stratification?
Water stratification is caused when water masses with distinct qualities, such as differing salinities and temperatures, come together. Significant differences between the water masses cause the formation of a layer between them, instead of mixing. So when you are swimming and the temperature of the water suddenly drops or it suddenly becomes a lot warmer, that means you just crossed a layer from one water mass to the other. And sometimes the layer between the water masses is so pronounced that you can see it! Which is why your visibility underwater might become a little fuzzy. Pretty cool huh? But, unfortunately, it’s not quite that simple. Cold vs. warm water pockets or fresh vs. salty water pockets are not just randomly distributed, when it comes to water, density is the ultimate decider of where each water mass is found. Low temperature and high salinity lead to higher density and in fact, in the open ocean the saltiest and coldest water masses are found at great depths. These cold water masses come from currents that carry warm surface waters from low latitude locations, such as the Caribbean, all the way to the earth’s poles, where the surface waters cool down and sink, producing movements of water, which, believe it or not, drive the earth’s climate.
Now you know how cenotes and coral reefs are connected, which is something, that from my experience, not many people know about. But next time you go snorkeling in the bay and encounter water stratification caused by cenote and ocean water masses you will know exactly what it is and the science behind it!
Article by Ava Ibanez, coral restoration intern, 2016.