Marine inverts and climate change

It is almost Thanksgiving and everyone is really excited to see family and friends, eat lots of food that is not ramen or mac and cheese, and sleep. We also are getting closer to the end of the semester and that means two things: finals and projects. For Marine Invertebrate Zoology, we have to do a presentation and short paper on an invert of our choice and how climate change is affecting it. I have an unreasonable fascination with venomous and "dangerous" animals and so my invert of choice is Acanthaster planci, the "crown-of-thorns" sea star.

A little background information: Acanthaster planci is a nocturnal sea star that bears between 8 and 21 arms and can range up to ~70 cm in diameter making it the second largest species of sea star. Acanthaster comes in a variety of colors depending on diet and region. These sea stars have a calcium carbonate skeleton and possess large, venomous spines in contrast to the short, blunt spines usually present on sea stars. They are found throughout the Indo-Pacific region, though they are most common on the Great Barrier Reef. Their average life span is about 16 years. Juvenile A. planci eat plankton, but adults are opportunistic carnivores, consuming scleractinian corals, encrusting sessile invertebrates, and dead animals. Individuals crawl at the rate of up to 35 cm per minute and feed by everting their stomachs through their mouths onto their prey and digesting the tissues. While A. planci is generally protected by its venomous spines, predators of A. planci include the giant triton shell Charonia tritonis and various fishes. An average sized adult (40 cm) can consume up to 478 square cm of live coral per day.

So why study the impacts of climate change on this animal? It seems that it has a negative impact on their ecosystem and humans, so why should we care if it is negatively impacted by climate change? I thought it would be interesting to see whether this sea star is being negatively affected by climate change or thriving. Since we got the assignment two days ago, I do not have all the answers yet. But from what we have studied so far, I would expect ocean acidification to negatively affect these animals. Ocean acidification is caused by carbon dioxide mixing with ocean water, creating hydrogen ions (i.e., acid) that attach to carbonate and form bicarbonate. This also inhibits formation of calcium carbonate because the hydrogen ions attach to the carbonate, inhibiting calcium. Sea stars have a calcium carbonate skeleton and are dependent on the ability of calcium carbonate to form in the ocean. This process also affects coral calcification, so there is a double negative impact. From what I have read so far, the increase in temperature is likely to be extremely bad for coral reefs but beneficial for A. planci. More research has to be done but regardless, I think it will prove to be an interesting project.