Coral reefs are one of the world’s most biologically diverse and productive ecosystems, yet also one of the most threatened. Human activities have dramatically contributed to this decline. Apart from overfishing, sediment run-off from agriculture, industry and sewage disposal has increased nitrates and phosphates in our oceans and rivers. This increases algae growth and when algal bloom covers the water surface, sunlight cannot reach the corals and other plants. Over time, this affects the marine animals and we may see an even greater decline in biodiversity in our waters. While some reefs can recover from these disturbances, many are overgrown with seaweed (macroalgae), which are not as beneficial to our ecosystems.