When one hears “Everglades”, it evokes landscapes of reeds moving in the water, alligators lunking and mangroves on the horizon. But what lies under its surface – and what science is just beginning to decipher – reveals an amazing complexity: a living water system, a natural laboratory, an ecological tightrope.

One of the keys to understanding why water sometimes looks clear (or at least surprisingly not cloudy) in the Everglades is in the way it flows: not like a deep river, but like a “water sheet” that extends. This phenomenon is known as sheet-flow: the water comes out of Lake Okeechobee and slides just downhill, on an almost perfectly flat limestone rock bed, with a slope of only a few centimeters per kilometer.

That extremely slow flow (for example, old studies show speeds such as 34 meters per day) makes suspended particles, fine sediments and nutrients have time to settle, integrate into the soil or be retained in biological communities before moving forward. The absence of violent currents limits the drag of turbidity.

In addition, the geological bed is crucial: the subsoil is composed predominantly of porous limestone and deposits of organic sediments (turband) that interact with water.

Microbes, periphyton and the microscopic factory of the ecosystem

This is where “invisible magic” comes into play. The Everglades are, in essence, a system maintained by microorganisms. Periphyton layers – a dense mixture of bacteria, algae, fungi, protozoa and combined debris – cover many submerged surfaces and are one of the main biochemical engines of the wetland.

These microbial communities fulfill vital functions:

Nutrient cycles: they transform nitrogen and phosphorus so that they are available to plants and other organisms.

Natural filtration: they retain particles and contaminants, helping the water that follows its course to “clean” gradually.

Primary production: many aquatic food chains depend on microbial biomass (aquatic insects, larvae, small crustaceans) that then serve as food for fish, amphibians and birds.

In sediments there is another mysterious role: anaerobic communities (microbes that live without oxygen) that transform sulfur compounds, methane, sulfur compounds and other gases.

These processes can generate dark and sulfurous zones in the subsoil, which is often not seen but has profound impacts on water chemistry.

Due to this microbial work, many nutrients are “trapped” locally or transformed into less mobile forms. Thus, the water that continues to advance has less load of sediments and floating particles in suspension.