coral reefs

• the outside of coral reefs are covered with small flowers called polyps

• the polyps take carbon (from the algae and seawater) and combine it with calcium, to create calcium carbonate

  • calcium carbonate is used to build the coral’s skeleton

• inside the polyps is algae (called zooxanthellae)

  • the algae is an autotrophs - needs to absorb sunlight in order to photosynthesize & produce sugars for themselves & their coral host, and also provide the coral with nutrients needed for growth and stability

    • also provides the coral with CO2, which can be used by the polyps to combine with calcium, and form calcium carbonate, and thus form the skeleton of the coral

when the coral undergoes stress, such as ocean acidification through high temperatures, overfishing or pollution, they will dispel or release the algae, meaning they dont gain the nutrients they need to survive. they also don’t receive CO2, meaning decreased calcification and weaker skeletons. they will also lose their color (since the zooxanthellae provide corals with color as well)