List examples of human impact on the reef?

Answer 1

Humans do numerous things that threaten the vivacity and basic survival of the reefs. For one, deforestation. Deforestation near coral reefs adds a lot of sediment to the ocean which either blocks out sunlight and kills the photosynthetic zooxanthellae in the coral or raises the water temperature, changes pH, etc (because coral is so small it has a very specific range of tolerance). Another is pollution from agriculture an industry. Runoff can encourage eutrophication (an algal bloom which lowers dissolved oxygen and increases the biological oxygen demand--in other words, causes other organisms not to get enough oxygen) which blocks sunlight and creates competition for dissolved oxygen in the water which kills off many corals. Something interesting I found when researching for my IB Environmental class project on coral bleaching was that human Skin Care products (such as sunscreen) that wash off into the ocean cause coral bleaching by chaging the pH and temp. of the water. Here's a quote from an article I found: “Research shows that chemicals in sunscreens can accumulate in aquatic animals, have an oestrogen-like effect and biodegrade into toxic by-products. The researchers investigated the effects on coral of adding controlled amounts of three brands of sunscreen to the surrounding seawater. The research was carried out at locations in Mexico, Indonesia, Thailand and Egypt, representing a range of ecosystems. Even when sunscreen was added in low quantities, large amounts of coral mucous, composed of algae and coral particles, was released within 18-48 hours. Within 96 hours, complete bleaching of corals had occurred” (European Commission, Environment DG). Global warming (if you believe that humans augment its impact) can be considered a human impact on the reefs, too. As I said, the corals are so small that their range of tolerance is extremely limited--raising the temperature of the waters at all is detrimental to their health. Overall it's our mindset and collective way of life, not only individual examples. These are only few--you can find myriad others, but these are main contributors.