The impact of human sewage on tropical oceans: What you can do

From an article by Rebecca V. Ferrell, PhD, Professor of Biology, Metropolitan State College of Denver, posted on Sac-Be:

A hallmark of tropical ecosystems is they are low in the nutrients needed by living creatures, like nitrogen and phosphorous, because those nutrients cycle very quickly and don’t linger in a usable form. Organic material breaks down rapidly in the warm climate, and plants quickly take up any nutrients that are released to fertilize their lush growth. The result of this enthusiastic growth is that the soil and water are usually low in nutrients. In cooler climates, nutrients like nitrogen or phosphorous might linger in the soil or water, but not in the tropics. Creatures of the tropics, like the reef-building corals, evolved in a world where nutrients were not abundant, and they are well adapted to this nutrient-poor environment.

Humans can change the balance of nutrients by disturbing soils for construction, by adding chemical fertilizers directly to soils, as we do when farming or maintaining golf courses, and by the release of our wastes in the form of sewage, which is very rich in nutrients. Recent human activities on the Riviera Maya have increased nutrient levels substantially, and these nutrients are a real threat to the coral reefs that protect the coast of the Yucatan Peninsula. . . .

When nutrient levels go up, the tiny coral animals that build coral reefs feel the strain. Increasing levels of nitrogen, especially, cause algae to grow. Algae can grow right across the surface of a coral reef, blocking sunlight from reaching the coral animals underneath. . . .

There is much that can be done to protect this exquisite region from being loved to death by its visitors. For more than a decade, Centro Ecológico Akumal (CEA, pronounced “SAY-ah”) has been a leader in this effort, with programs that focus on water quality and conservation of the area’s fragile resources. The first constructed sewage treatment wetlands were built at CEA in 1996 in cooperation with Mark Nelson. Dr. Nelson later was a designer of the wetlands in the Biosphere 2 project, and he was one of the “biospherians” who lived in that experimental closed system in Arizona designed to increase understanding of the complex functions that take place on planet Earth. That original sewage treatment wetland is still working well, removing bacteria and nutrients from wastewater, and a second CEA wetland provides excellent treatment for sewage from the public restrooms that serve the Turtle Bay and Cueva del Pescador restaurants and local shops, as well as housing for CEA volunteers. Many homeowners and hotels in the area have followed suit, constructing wetlands to remove nutrients before sewage is released; it is estimated that over 200 wetlands are in operation along the Riviera Maya, with more than 50 of these in the Akumal area.