Sponges are animals that are incredibly important for improving water quality. Ounce for ounce, the amount of water they filter per day is astounding.
A basketball-sized sheepswool sponge can filter over 500 gallons of water per hour, which is over 12,000 gallons per day. Since sponges do not have tissues or organs, all of this is happening at a microscopic level with tens of thousands of tiny flagella waving water in through thousands of tiny pores called ostia and out through the larger oscula.
Sponges are the dominant filter feeders in the Florida Keys and they are eating phytoplankton, bacteria and viruses. They are essential fish habitat for juvenile spiny lobsters, stone crabs and bonefish. These sponges are important places to hide from predators and provide a buffet of tasty invertebrate snacks.
In the Florida Keys, these three species generate more than $150 million dollars to the economy from seafood, fishing and tourism. There is also a commercial sponge fishery and Monroe County leads the state in the number of sponges landed. Unlike most commercially-fished species, sponge landings are recorded by the piece and not by the pound.
From 2020 to 2023, there was an annual average of 135,000 sponge pieces landed in Key West and Marathon. The average price per sponge piece was less than $2, with an estimated average annual value of $262,935.
The city of Key West has a very long history with sponges. Until the early 20th century, sponges were a major export from Key West, second only to hand-rolled cigars. Before DuPont created synthetic cellulose sponges in the 1940s, these wild harvested sponges were a household staple for bathing and cleaning. When most people think about sponges, they probably picture a bath sponge. Yet out of the nearly 9,000 sponge species, only a couple of dozen worldwide are the types suitable for harvest because they stay soft and spongy when processed and dried.
In the Florida Keys, these are the species with the common names sheepswool, yellow, grass, mountain, hardhead and basket sponges which inhabit the shallow nearshore waters associated with seagrasses and hardbottom.
Sponges are also incredibly important in the search for new human medicines. Since sponges cannot bite, pinch or swim away, they have developed complex chemical defenses to ward off would-be predators. It turns out many of these chemicals have very potent anti-viral and anti-cancer properties. In fact, we have a very famous sponge located in just a few feet of water all over the Florida Keys. The scientific name is Tectitethya crypta, commonly called the volcano sponge because of the volcanic-shape and a single large, raised oscula usually covered in algae and sediments and it is very well camouflaged.
In 1969 this was the first human medication from the ocean, and it was used to treat leukemia and now synthesized to make medications for herpes, HIV and ebola. Next time you snorkel or dive, take a moment to admire these magnificent animals.
