Trouble in paradise: The effect of glyphosate and Roundup toxicity on coral fertilization and settlement

Abstract

Coral reefs are some of the world’s most ecologically important ecosystems, supporting more species per unit area than any other marine environment. Globally, there has been a decrease in coral reef cover and species diversity, resulting in a loss of ecological, economic and cultural value. In particular, the Hawaiian Archipelago is home to unique reef communities which have declined in health due to pollution, overfishing, recreational overuse (tourism pressure) and sedimentation. Previous research indicates that pesticides and herbicides entering the ocean as runoff are a significant problem. Several studies have been done to assess the effects of herbicide pollution in ecosystems near farms, but very few or no studies have been done to examine its effect in saltwater environments. This paper seeks to answer the question: does the presence of glyphosate or its commercial formulations (e.g. Roundup) have any effect on the coral Montipora capitata during fertilization and settlement stages? We exposed M. capitata gametes and larvae to increasing concentrations of glyphosate and Roundup following spawning periods in July and August 2015. We found that there was a significantly lower fertilization and settlement rate in M.capitata exposed to Roundup (p < 0.05), but no significant difference when exposed to glyphosate. This suggests that levels glyphosate in coral reef communities ought to be monitored for coral conservation efforts and the effect of other Roundup ingredients on coral health ought to be investigated. To our knowledge, this is the first experiment to show a deleterious effect of Roundup on a coral species.