COTS: Gatecrasher of the Reef
Coral reefs provide a shelter for diverse marine species that are often called the “rainforests of the sea” due to their diverse ecosystem.
However, according to a report conducted by the World Resources Institute, 75% of coral reefs are threatened. These threats include damage from anchors and climate change. This article, however, will focus on the Crown-of-thorns Starfish (COTS), a biological threat to coral reefs.
COTS are venomous invertebrates that are native to coral reefs located in the Indo-Pacific Ocean. The Australian Institute of Marine Science (AIMS) reported that the COTS are responsible for nearly half of the decline of the coral reefs.
COTS are regarded as powerful enemies of the ocean as they have between 14-21 arms, more than other starfish which have 5. Moreover, they are also capable of moving 20 metres per hour.
They position themselves on top of the live coral and then expel their stomach through their mouth, strangling the coral. They complete their eating by secreting digestive enzymes and absorbing the dissolved tissues. The major problem with this is that the COTS are eating the coral faster than the coral is able to reproduce. Researchers of the AIMS laboratory have also proven that the increase in the survival of COTS is a result of the abundance of phytoplankton, their food source.
What human factors result in an the increase in the population of COTS?
1. Changes in climate and ocean chemistry, caused by the human interference on the environment, degrades the marine ecosystem.
2. Fertilisers and pollutants carried by the early-season monsoonal and cyclonic floods cause a dramatic increase in the number of phytoplankton, a source of food for COTS.
"COTS are regarded as powerful enemies of the ocean as they have between 14-21 arms..."