what is a reef?
Reefs are incredibly diverse living communities made up of corals and the organisms that live in and around them. Corals are invertebrates in the phylum Cnidaria. They come in two forms: soft corals, called Alcyonacea, and hard corals, called Scleractinia. Soft corals don’t form reefs, but they are often found in reef ecosystems. Reefs are primarily composed of hard corals, also known as stony corals. Reefs form when a free-floating coral larva, or a planula, encounters some sort of nonliving marine object (e.g. a boulder or a shipwreck) and attaches itself. Soon, it begins to develop a rock-like exoskeleton, and as more coral polyps join and build exoskeletons, the reef begins to grow.
All of this info came from the NOAA Coral Reef Conservation Program website. Check it out for a more detailed look at coral anatomy!
why are reefs important?
Reefs provide incredibly rich and diverse environments. In addition to the beautiful and ancient reef itself (some reefs date back thousands of years1), more than a million different creatures2 live in and around the corals! Brightly colored fish, sea turtles, anemones, sharks, seahorses, and clams are just a few of the incredible wildlife found in this ecosystem.
what is coral bleaching?
We’re losing our coral reefs- and quickly. More than 60% of corals are at risk of bleaching3, or losing their color and dying. To understand bleaching, you have to take a closer look at the anatomy of a coral polyp. Inside the coral’s stomach tissue are found microscopic organisms called zooxanthellae, a type of photosynthetic algae. These algae have a symbiotic relationship with the coral- in other words, they each benefit from the other’s presence. The algae provide the coral with energy, and the coral gives the algae shelter and the necessary nutrients for photosynthesis.
However, when the coral comes into contact with something dangerous, it expels the zooxanthellae to ensure its own survival, which turns the coral white. Although this allows it to survive temporarily, the coral starves, as the zooxanthellae provided most of its energy4.
what causes coral bleaching?
Many things contribute to coral bleaching: oil spills, rising ocean temperatures, and salinity changes are all culprits. However, one unexpected factor that is directly linked to coral bleaching is exposure to chemical products often found in personal care products such as sunscreen. These chemicals wash off our bodies when we jump into the ocean covered in sunscreen containing oxybenzone5 and a handful of other chemicals such as avobenzone, octisalate, octinoxate, octocrylene, homosalate. These chemicals often end up on coral reefs- in fact, about 5 tons of sunscreen washes off of our bodies and onto reefs every year6.
are all sunscreens bad for reefs?
Sunscreens containing mineral ingredients such as zinc or titanium oxides are better options than chemical-based sunscreens. Studies are still underway, but they appear to have substantially less impact on coral and other marine life. However, the easiest way to help reduce sunscreen-related bleaching is to use less sunscreen in general! Instead of putting on extra sunscreen, it’s a lot easier to simply wear a hat, put on a shirt, and use sunscreen as your last resort instead of your first option.7
1 “How Coral Reefs Grow | Coral Reef Alliance”. Coral.org.
2 “What Species Live In And Around Coral Reefs?”. Oceanservice.noaa.gov.
3“Global Coral Bleaching 2014-2017: Status And An Appeal For Observations”. Coralreefwatch.noaa.gov.
4“Coral Bleaching – GBRMPA”. Gbrmpa.gov.au.
5Downs, C. A. et al. “Toxicopathological Effects Of The Sunscreen UV Filter, Oxybenzone (Benzophenone-3), On Coral Planulae And Cultured Primary Cells And Its Environmental Contamination In Hawaii And The U.S. Virgin Islands”. Archives of Environmental Contamination and Toxicology 70.2 (2015): 265-288.
6Danovaro, Roberto et al. “Sunscreens Cause Coral Bleaching By Promoting Viral Infections”. Environmental Health Perspectives (2008): 441-7.
7Toline, C. Anna. “Protect Yourself, Protect The Reef”. National Park Service.