Infestations of crown-of-thorns sea stars destroy coral reefs, so researchers at Queensland University of Technology developed an autonomous robot sub that recognizes starfish and then kills them with a poison injection.
Video below! From IEEE Spectrum:
These infestations of crown-of-thorns sea stars (herein abbreviated COTSS) are only partially our fault: it's true that we've been relentlessly overfishing the things that eat COTSS, and that's a bad thing. However, the chief cause of COTSS population explosions seems to be correlated with rain over nearby land washing extra nutrients into the water, causing plankton blooms and making it easier for COTSS larvae to find food and grow up big and strong and spiky. Since one single large COTSS female can deliver upwards of 50 million eggs, even a modest boost to larvae survival rates can result in an enormous boom in mature sea stars…
(A new kind of) one-shot poison (which is harmless to everything else on the reef) is what makes autonomous robotic sea star control possible, since it means that a robot can efficiently target individual sea stars without having to try and keep track of which ones it's injected already so it can go back and repeat the process nine more times. At Queensland University of Technology in Australia, a group of researchers led by Matthew Dunbabin and Peter Corke spent the last decade working on COTSBot,* which has been specifically designed to seek out and murder crown-of-thorns sea stars as mercilessly and efficiently as possible.