How Sedimentation, Nutrient Enrichment, and Overfishing Impact a Coral Reef Ecosystem Immediately Following a Disturbance

by Natalie Ireland

Coral reefs are regularly disturbed by natural phenomena such as bleaching, storms, and outbreaks of predators, such as the corallivorous sea star Ancanthaster planci. Corrallivores are animals that eat coral polyps. Coral reef ecosystems are resilient, and are often able to recover from large-scale disturbances quickly. However, anthropogenic stressors such as overfishing, nutrient enrichment, and sedimentation can prevent coral reefs from recovering. Nutrient enrichment, caused by terrestrial runoff, creates the perfect environment for benthic algae to grow on disturbed and broken coral reefs. Overfishing, working in tandem with nutrient enrichment, causes an overgrowth of algae if there are not enough fish to graze it, and the successive degradation of the reef. Sedimentation is also another side effect of terrestrial runoff. Sedimentation buries corals, which blocks light from reaching them and potentially stops coral recovery. However, sedimentation, when not paired with any other stressor, can also stop the growth of algae by burying surfaces for algae to grow on. Gil et. al. (2016) set out to test the interactive effects that overfishing, sedimentation, and nutrient enrichment have on coral reefs in French Polynesia. They hypothesized that these anthropogenic disturbances, when working interactively, will negatively impact corals, while promoting algal cover. Continue reading