Hey hey hey welcome back.
As we already know, zooxanthellae are little algal bodies that live in symbiosis with coral. They live in a mutualistic relationship, which means both organisms benefit. If you have any question about that, look at my last blog post.
We’re going to talk about something a little dark this week…. coral bleaching.
So first off, lets define what coral bleaching is. The actual mechanism of coral bleaching is when the coral “spits out” its zooxanthellae partner. This happens when sea temperatures change drastically, warm or cold, which as we know is inevitable. When sea temperatures change drastically, the zooxanthellae starts creating oxygen free radicals in its photosynthesis process. This in turns hurts the coral, so it rids itself of the zooxanthellae. This doesn’t happen simultaneously. The zooxanthellae is spit out one by one, but eventually all are gone. This leaves the coral “bleached” because the zooxanthellae is what gives the coral its vibrant color. Once the coral begins a bleaching event, if it has spit out enough of the zooxanthellae, it will eventually die. Some corals can feed themselves, but because nutrients greatly comes from the zooxanthellae, mortality comes quickly after full bleaching events.
You may be asking, why do I care?
Long story short, YOU SHOULD CARE A LOT.
Coral reefs are detrimentally important to the ocean and it’s balanced ecosystem. Coral reefs provide shelter and habitat to many fish. They only inhabit 1% of the ocean floor, but are homes to over 25% of the marine life. I took a class in the Florida Keys over spring break, and seeing the corals alive and well was something to behold. So many fish call the coral reef home. What happens when that coral bleaches? No home for the fish anymore. Another reason that coral reefs are necessary is their ability to assist in carbon and nitrogen fixing. If you didn’t know nitrogen and carbon isn’t just ready and available for us to use (us in this case being the fish). Also when you think about the symbiotic relationship, the zooxanthellae is a very important player is cycling nutrients through the coral but also the ocean as a whole. Coral also acts as an important source of food for many organisms. One in particular, is the parrotfish. The parrotfish is a funny looking fellow.
He has a little beak that scrapes off pieces of the living coral, digests the zooxanthellae, and poops out the coral skeleton which becomes sand. If a coral bleaches, the parrotfish no longer has food. If the parrotfish goes extinct, than things that eat it like the moray eel and the reef shark no longer have that as a food option. Coral bleaching leads to major disruptions in the oceanic food chain. The ocean as we know it relies on these coral reef populations.
Here is some scary numbers for you: Coral bleaching is five times more frequent now than it was 40 years ago. This can be seen following global warming trends. After significant warming weeks, coral bleaching reaches a dangerous level. Pictured below is coral bleaching risks for the year 2016. 2016 was the last major coral bleaching event.
So yeah lets save the planet and stuff. This is kind of getting a little scary.
Brittany,
What a beautiful fish the parrotfish is!! I really liked your blog post not only because of all the great details you provided, but also because you emphasize a serious problem that is occurring at such a rapid rate. I was truly frustrated the first time I ever heard about coral bleaching because corals essentially provide a home for millions of marine organisms. I still remember snorkeling in Hanauma Bay in Hawaii and seeing the vibrant coral reefs and fishes. It would be heartbreaking to not see that the next time I visited! People really need to buckle down and focus in on the serious issues that we are facing from global warming.
-Simi P.
I remember when I took marine bio, we talked about the effect of lionfish on coral reefs as well! They’re an incredibly invasive species that have few predators to keep their population in check and also reproduce pretty quickly. They feed on the herbivores that eat algae from the corals, and if too much algae grows, it can be harmful for the reef which is already under enough stress as you described!
I always thought about the importance of coral reefs and how global warming is affecting them. Now that I understand the process of coral bleaching, I am very concerned for the oceans ecosystem because it seems its inevitable now.
Hi, first off I wanted to say we did our blogs on the same microbe which is cool. I like how you made your blog into more of a conversation to make it more understandable for everyone. I never knew how color sand came about but now I know its the parrotfish and they can only do this because of the zooxanthellae.