Beyond Climate Change: The Impact of Agrochemical Pollution on the Symbiotic Interactions and Ecological Success of Corals

Héctor Ocampo-Alvarez, Fabián Alejandro Rodríguez-Zaragoza y Amayaly Becerril-Espinosa

Abstract

Coral reefs are highly productive marine ecosystems that harbor a high biodiversity. The forming organisms of these reefs are the scleractinian corals, which form symbiotic interactions with multiple microorganisms. One of the best known symbiotic interactions in these systems is the one established with the microalgae Symbiodinium. The microalgae produce through photosynthesis up to 90% of the energy required by the coral. On the other hand, Symbiodinium receives from the coral an appropriate niche, that protects Symbiodinium from the external environment, from the competition with other organisms and predation; it also provides abundant nutrients produced by other coral symbionts highlighting the bacteria. As well as this, multiple symbiotic interactions confer metabolic capabilities to corals, which have enabled their capacity to adapt to climate changes for millions of years. However, in recent decades coral reef ecosystems are being extensively decimated. Given the new characteristics of an environment with significant changes sometimes somewhat erratic, probably the interactions that initially provided ecological advantages to corals are no longer sufficient to overcome environmental adversities or that as a result of the changes generated in the environment. The diversity of microorganisms capable of interactions that can be formed with the few remaining microorganisms do not confer to the coral, sufficient adaptative advantages to face the challenge of climate change. In this essay, we argue about the possibility that a decrease in the stock of microorganisms capable of interacting with corals, as a result of marine pollution, is a cause of the loss of biological aptitude of corals to survive in the current global climate change.