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Under the Sea Part II: Corals and Sponges

"Giant Brain Corals can live up to 900 years old. Just incredible. Interestingly, just as they resemble brains physically, it is also thought that they are a more advanced coral species due to the connectivity of the polyps..."

Curação has some of the healthiest reefs in the Caribbean

Curação has some of the healthiest coral reefs in the Caribbean, although, like elsewhere, it is subject to the general pressures of increasing ocean temperatures and acidification. In addition the reefs here are vulnerable to the location specific pressures of overfishing and pollution (which is why the reefs are in a worse state in more developed areas and in comparison to its better protected neighbour Bonaire), and the challenges and time it takes for reefs to rebuild after bouts of disease and hurricanes.

Luckily the reefs here benefit from the interventions of Carmabi, The Caribbean Research and Management of Biodiversity foundation, which was established in 1955 and manages five national parks in Curação. They protect areas of the island, conduct scientific research, work with schools to educate children on the island about their natural environment and intervene where necessary to support the restoration of ecosystems, such as coral reefs.

We've seen interventions to help rebuild coral populations at several locations around the island

Sea fans

Sea fans are constructed of a colony of coral polyps, each one having eight tentacles. The skeleton is made of a scleroprotein (as are collagen and keratin) called gorgonin and the polyps cover the skeleton in a layer. They spread out their tentacles to catch plankton to feed on.

Sea Fan

Staghorn coral

Staghorn coral are nocturnal predators, catching zooplankton using their minute stinging tentacles. They also harbour algae to get energy from sunlight while in return the algae gets protection from predators. Staghorn coral are vulnerable to bleaching and also take longer to recover from bleaching episodes compared to other coral species.

Staghorn Coral

Elkhorn Coral

Elkhorn coral is found in shallow water 1-5m deep and is fully grown at 10-12 years old. It is large and fast-growing, with branch length increasing by 2-4 inches each year. Individual polyps live 2-3 years, while the colony itself can endure for hundreds of years. During the day the polyps retreat into their coral nest, to hide from their predators, such as damselfish and emerge to feed at night on a tiny algae called zooxanthellae. They release their gametes (reproductive cells) during full moon in August and September. However, the bulk of their reproduction is asexual through the breakaway of part of their branches to propagate a new colony.

Elkhorn Coral

Lettuce coral

Lettuce coral is a type of plating coral, forming sheets rather than branches. The coral contains a tiny algae called dinoflagellates which gives the coral most of its energy through photosynthesis. The rest of the energy is provided through the polyps capturing plankton at night. Lettuce coral is one of the species most vulnerable to bleaching during periods of high water temperatures. Bleaching shows a coral to be under extreme stress causing it to expel the algae living in their tissues turning it white. Thankfully we haven’t seen any of the bleached lettuce coral, it has been a rich yellow ochre colour, although usually in very small colonies

Lettuce Coral

Mustard hill coral

Mustard hill coral looks a bit like a cauliflower. The polyps each have six tentacles and are generally retracted during the day. It grows in water that is usually up to 15m in depth but can be up to 50 metres deep. This relatively deep position makes it less susceptible to bleaching than shallower dwelling corals. The polyps contain stinging cells called nematocysts as a defence against stoplight parrotfish and creatures that eat it.

Mustard Hill Coral

Giant Brain Coral

Giant Brain Corals can live up to 900 years old. Just incredible. Interestingly, just as they resemble brains physically, it is also thought that they are a more advanced coral species due to the connectivity of the polyps, which are not segregated by the skeletal structure as other coral species are. This connectivity means that the polyps in essence can communicate as they pass on nutrients, hormones and oxygen to each other. Because of this connection though, they are more at risk of disease, such as black band disease and white plague.

Giant Brain Coral

Sponges are much simpler organisms than corals, with no tissues, while corals are complex organisms. Sponges feed and reproduce completely differently from corals. However, they both have colourful and immoveable invertebrates. Despite their simplicity, they are essential to the marine ecosystem. Their significance was actually discovered through scientific research done in Curação, which found that 'Sponges recycle nearly ten times as much matter as bacteria, and produce as much nutrition as all the corals and algae in a reef combined.' (BBC 2013)

Yellow Tube Sponge

The Yellow Tube Sponge can reach 20-50cm in height. They feed by filtering plankton, bacteria and dead organic material through the water they take in through their pipes. They defend themselves by emitting a chemical that is offputting to algae and barnacles to prevent them growing on them. They can also rearrange their cells to become upright again if the tubes are knocked on their side. They can clear their feeding filter systems by "sneezing."

Bless you!

Brown Variable Sponge

This encrusting sponge colonises dead corals and looks like bubbling lava.

Brown Variable Sponge

Marine environments that contain coral reefs, support a far greater diversity of species and the sponges contribute to providing nutrients to both the reefs and the fish and other aquatic life that support them. All of us can contribute to supporting the health of reefs by reducing our greenhouse gas emissions. The increasing ocean temperatures and ocean acidification contributes to bleaching events, to increased numbers of storms which can wipe them out and their vulnerability to disease, both improving the conditions for disease causing pathogens to thrive and weakening the immunity of the corals themselves.


References Acropora palmata (Elkhorn coral). (2009). Animal Diversity Web. Agaricia agaricites. (2023, April 16). Wikipedia. CARMABI. (n.d.). Retrieved September 24, 2023, from Geographic, N. (2020, March 3). Staghorn coral, facts and photos. Animals. News, B. (2013, October 7). Sponges help coral reefs thrive in ocean deserts. BBC News. Sponges, S. F. (n.d.). Cliona varians. toni. (2023, January 13). Yellow Tube Sponge - Creature Feature. WiseOceans. US. (2019). What are brain corals? Wikipedia. (2022, June 10). Porites astreoides. Wikipedia.

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Sep 24, 2023

I never knew there was so much about coral I didn't know 😄

There's truly a whole other world beneath the surface of the sea as precious, vulnerable and in need of TLC and preventative action as above xxx

Sep 24, 2023
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I know it’s a fascinating organism, hopefully they will be able to adapt to these increasing temperatures

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