It’s not an oil pattie; it’s a tunicate
Mote Marine Laboratory has recently been getting inquiries from the public asking whether the darkened blobs they’re seeing on some Southwest Florida beaches is oil washing in from the Gulf of Mexico because of the Deepwater Horizon oil rig blowout. Rest assured: It isn’t.
Believe it or not, these amorphous blobs are actually living organisms called tunicates and their shapes, sizes and even their coloration can vary widely. Some 78 species have been documented in the Gulf of Mexico. They’re invertebrate species that have characteristics of back-boned critters including a notochord, dorsal nerve cord and pharyngeal slits. In adults, these features become simple ganglion.
As larva, tunicates can swim and look like tadpoles, but once they grow up, they’re immobile filter feeders. Adult tunicates have sack-shaped bodies with two siphons they use to filter water. The hard covering on their bodies is called a tunic.
You may also know them by their other name: sea squirt. We can only assume that they picked up this moniker because when playful little brothers (and sisters) on the beach squeeze a tunicate’s body, water squirts out the end. Think nature’s finest squirt gun.