Scientists solve mystery of Caribbean sea urchin die-off.

Scientists have identified the cause of a mysterious die-off of sea urchins in the Caribbean last year as a tiny parasite known as a ciliate. The long-spined sea urchins were losing their spines and dying in "droves," which is concerning as they eat up the algae that would otherwise decimate coral reefs. The ciliate responsible for the die-off is a specific kind called scuticociliate, which has been linked to mass killings of other marine species. The finding could help mitigate risk to marine life through such things as boat traffic or dive gear.