Macroalgae Threaten Coral Reefs
From 2006 to 2014, the macroalgae coverage over the coral reefs almost doubled, going from 13 to 23 percent. It is becoming a very prominent threat not only to the coral reefs of the Riviera Maya but to the whole Mesoamerican Reef. The excessive growth of algae blocks sunlight from reaching the reef and can affect the reproduction of corals and photosynthesis of zooxanthele (microalgae that lives inside corals’ polyps and gives them their color and other benefits).
The main problem, according to Marisol Rueda Flores, Mexico’s Coordinator for the Healthy Reefs Initiative, is closely linked to the decline in herbivorous fish of sizes bigger than 40 centimeters, such as parrotfish. Parrotfish spend the vast majority of their day eating algae growing on corals.
Rueda clarified that 78 percent of the parrotfish at sea were less than 20 centimeters. As a result, they don’t grow to more than 40 centimeters, the point at which they would be able to reproduce and increase the population.
Macroalgae increases due to an excessive amount of nutrient runoff into the sea (primarily from fertilizers, wastewater, or storm water), combined with sunlight and warm temperature. Some other algae species can have an algae bloom, being of particular concern as they release neurotoxins and can have severe biological impacts on organisms.
“In Quintana Roo, Cozumel has the highest coral cover, at 24 percent, which is very high compared to other areas where there is only between 16 and 18 percent coral cover. If the macroalgae continues to grow, the coral will suffocate,” Rueda explained.
Besides having the macroalgae inhibiting the growth of the coral, we can have coral bleaching due to the increase of water temperature, and it causes zooxanthalae microalgae to leave the coral, which is what gives corals their original color.
Healthy Reefs has made an alliance with the Mexican Center for Environmental Rights (CEMDA) and the State Environmental Secretary to campaign about the importance of the parrotfishes.
“We have a group working to kick start this campaign, we are going to hang posters with information to distribute to the fishing communities and Healthy Reefs will make informative videos about the importance of having laws to protect this specie of fish.”
Although the intention is to take the proposal to lawmakers for analysis and approval, they will first start the awareness campaign to create a better strategy.
In Quintana Roo, Cozumel has the most coverage of coral, at 24 percent, which is very high compared to other areas where there is only between 16 and 18 percent coral cover. If the macroalgae continues to grow, the coral will suffocate.”
Marisol Rueda Flores Mexico’s Coordinator of Healthy Reefs Initiative
/ Photo: Ian Drysdale