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By Kira Krall
The rock-like appearance of coral reefs makes it seem like these stunning habitats can survive just about anything. However, even a slight temperature increase can threaten the world’s most biodiverse ecosystem.
Coral reefs are known for their bright and brilliant colors. Recently, stark white reefs have been replacing these vibrant and thriving coral reef habitats. This coral bleaching occurs when the relationship between the coral and a special kind of alga,called zooxanthellae, is disrupted.
While the coral polyp itself is an animal related to anemones and jellyfish, corals are commonly mistaken for plants. Plants play a vital role in coral health. Corals build protective skeletons around their soft tissues. There’s just enough room in there for the algae, called zooxanthellae, to move in.
In return for protection from the elements and herbivorous fish, the zooxanthellae photosynthesize food for the coral. In this relationship, known as symbiosis, both the coral and the algae benefit. It is from the zooxanthellae that corals also get their bright, distinctive coloration.
Zooxanthellae can be pretty particular. This type of algae requires crystal clear water in order to photosynthesize. An increase in land runoff and fertilizers has led to decreased visibility in the waters where corals like to grow. The algae can’t grow food in these low light conditions, and its response to this stress is to eject itself.
Climate change and pollution are also impacting the coral itself. Increasing ocean temperatures damage the soft coral tissue and cause the algae to leak through the now thin coral membranes. Coral will also digest the zooxanthellae cells in response to stressors like high water temperatures. Any algae remaining in the coral’s tissues is unable to photosynthesize, causing the coral polyp to starve. The coral’s color fades and we are left with a graveyard filled with the bright white bones of the reef.
Millions of species of plants and animals use coral habitat at some point in their life cycle. The world’s reefs contribute almost $30 billion per year in the form of tourism, aquaculture, and coastline protection. Such a vital habitat has garnered a lot of attention.Facilities like the Florida Aquarium and Mote Marine Laboratory farm healthy coral and replant it on wild reefs.
Want to help out? General ocean conservation strategies like reducing land runoff carbon dioxide emissions will contribute to the health and regrowth of our coral reef habitats.