Robotic Submarine injects poison and kills ‘Crown of Thorns Sea Stars’ to save Coral Reefs

Australian researchers have build a COTSBot (Crown-of-Thorns Starfish roBot) which can identify and poison the crown of thorn sea stars that is responsible for the destruction of coral reefs.

As per a research by the Australian Institute of Marine Science, it was observed that over the past 30 years, there has been a severe decline (almost 50 percent) of the coral cover on some surveyed reefs. Surprisingly, the study also reflected that besides climatic changes, pollution, over fishing by humans and fins of the scuba divers one of the major attribution to the destruction is by the Crown-of-thorns starfish a.k.a Crown of thorns sea stars or COTSS.

The COTSS are big, spiky and it is totally dependent on the corals for survival.

The sea stars are known to regenerate even from the most devastating physical damages and according to researchers the only method of destroying the COTSS is to kill them to death or mutilate them! Thus, it is very difficult to combat the infestations of the COTSS.

A study reveals that human divers have to go deep down into the waters and repeatedly inject the individual sea stars (as many as ten times!) so as to ensure that they are dead because a single shot of injection cannot ensure their complete death.

Study also mentions that during the times of ‘population explosions’ of these sea stars one can find almost 100,000 COTSS per square kilometer.

Also human divers can inject only 120 sea stars per hour, which indicates that it is pretty impossible for humans to inject such a huge population of the COTSS.

The only viable option which seems to combat the rapid and massive growth of the COTSS is by using autonomous  “poison injecting robot submarines” or COTSBot (which is actually COTSSBot).

Major causes for the infestations of these COTSS:

One most important reason is over-fishing of those things which actually eat the COTSS and help to balance the ecosystem.

Another important factor which helps in the ‘population explosions’ of the COTSS seems to be related to the rains. It seems due to heavy rainfall extra nutrients from the neighboring lands get washed off into water which further results in boom of the plankton on which the COTSS larvae feed.

Interestingly, a single large female COTSS is known to deliver more than 50 million eggs. So the boom of plankton helps to boost the survival rates of these larvae which then flourish and grow much stronger with big spikes. It is believed that even moderate boosting of larvae survival leads to enormous boom of the mature sea stars.

Whenever there is a massive outbreak of COTSS it becomes necessary to curb and eradicate their growth at a much faster rate so as to keep the reefs intact. However, human divers have some limitations and it seems the maximum they can achieve is to poison only 120 sea stars per hour.

Autonomous Robotic submarine used to inject poison and kill the COTSS:

Last year researchers at the James Cook University in Queensland, Australia, developed an effective poison known as ‘thiosulfate-citrate-bile salts-sucrose agar’ and it was able to kill a COTSS within a time gap of 24 hours after just a single shot of the poison that caused discoloration and necrotic skin ulcerations, loss of body turgor, accumulation of colorless mucus, loss of spines accompanied with large and open sores that exposed the internal organs of these invertebrates.

This ‘one-shot poison’ is very effective in killing the COTSS and it has also been proved to be harmless to the ecosystem which prevails on the coral reef.

Furthermore, with the help of this ‘one-shot poison’ the robotic submarine can be sure of killing the COTSS in one go as it need not keep a track of checking which COTSS has been injected already and then keep injecting the same COTSS multiple times.

The major purpose of designing the ‘Robotic Submarine’ is to kill the COTSS with better efficiency. This COTSBot (an acronym for Crown-of-Thorns Starfish Robot) is the result of persistent efforts of Matthew Dunbabin and Peter Corke, a group of researchers at Queensland University of Technology in Australia, who have been constantly working for the past ten years to create such a device which would help to preserve the Great Barrier Reefs.

The COTSBot developed by Dunbabin and Corke is a yellow torpedo that weighs 30 kilogram and has a speed of over 2 meters per second.

It has been provided with five thrusters which actually helps the robot to hover over the COTSS in the deep water and then attack them by injecting the poison using its integrated system. The robot has an endurance for over 6 hours to successfully accomplish its mission.

The robot is fully autonomous and it can identify and even target the COTSS that is hidden between the coral.

The below footage shows how the COTSBot visualizes and even  injects the poison into the Crown of Thorns Sea Stars

Researchers believe that by deploying a small fleet of these COTSBot it is possible to destroy a major chunk of the COTSS over a period of say some days or weeks and later human divers and other natural predators can do the destruction of the remaining COTSS which will help to keep the COTSS population under control and also save the coral reef.

The paper titled “Robotic Detection and Tracking of Crown-of-Thorns Starfish“- is a joint effort by Feras Dayoub, Matthew Dunbabin and Peter Corke which they would be presenting at IROS 2015 that would be held in Germany next month.