Originally written September 2012
Sometimes, the best things in life are right in front of you. After a summer of diving all over Florida’s coasts, I discovered a hidden gem of a dive site practically right off of the coast of my parents’ home in Palm Harbor, Florida.
Dive Charter: Tanks-A-Lot Dive Charters
Hidden an hour or two from a bustling suburban setting lies the “Bent Knife” ledge – one of the few natural reefs I have explored along the greater Tampa area coast. Halimeda algae covered the site, proving that algae can sometimes be an important substrate and habitat in marine ecosystems. Hard and soft corals grew amongst the algae, all supported by a rocky ledge stretching for a good distance. One could travel along the top of the ledge, searching amongst the Halimeda for nudibranchs and tropical fish, and then return alongside the ledge, peering into the nooks and crannies for urchins, anemones, and toadfish. A lucky diver may even find an oddly shaped frogfish or batfish on the site.
When I descended upon the ledge, I bubbled in excitement at the sight of this royal blue and gold nudibranch, known as a Florida Regal Sea Goddess (Hypselodoris edenticulata). After further exploration, it became apparent that this nudibranch was actually quite abundant on the site. I had never seen one before, so it was amazing to see so many at this site. The dive charter explained that this is a fairly new occurrence. There was a time when nudibranchs were scarce, but, fortunately, they have been making a comeback over the past few years and are now regularly found at the ledge. Perhaps, this speaks to the health of the water. Invertebrates tend to be more susceptible to changes in water quality and temperature. An improvement in such conditions could spur the abundance of delicate nudibranchs.
The site was also covered in anemones and small sea worms, appearing to be translucent fans. In every small hole in the side of the ledge, one could discern the tentacles of a Warty Sea Anemone (Bunodosoma cavernata). Anemones are a type of cnidarian, which makes them related to corals and jellyfish. They are generally sedentary, staying in one place and using their mouth and tentacles to capture prey and for defense.
Another important invertebrate abundant on the site was long-spined sea urchins (Diadema antillarum). Sea urchins are grazing herbivores that eat algae, thereby preventing it from overgrowing the reef. Their removal of algae creates a patch of space that allows corals and other benthic animals to grow and flourish. In 1983, a mass mortality event of long-spined sea urchins occurred throughout the Caribbean waters. It is believed that this massive die off resulted in algae overgrowth in the coral reefs, further exacerbating the endangered status of hard corals like Staghorn and Elkhorn. The die off was due to a water-borne pathogen, to which the long-spined urchins were extremely susceptible.
During my dives in the Keys, I hardly observed any invertebrates, which seemed an odd contrast to the abundance at this site just outside of Clearwater. Perhaps this further speaks to their fragility and susceptibility to coastal run off, human collection activity, diseases, and changes in water temperature. Whereas the dive sites in the Keys were very close to shore and frequently visited, this ledge was much further from the coast and seemed to be hidden from divers and human activities. Except for the occasional stove… which looked to be obviously dumped at the site as either trash or as a failed attempt to create artificial reef habitat as a means to attract fish that would be good for fishing.
One of my favorite invertebrates is the sea hare. Previously, I had found a few of these strange sea slugs washed on shore, the Atlantic Sea Hare to be specific. During my second dive on the ledge, I was delighted to see a Spotted Sea Hare (Aplysia dactylomela). Although not a pelagic like the Atlantic Sea Hare, both share common features of appearing rabbit like and inking as a self-defense mechanism when startled or trying to escape a predator (or a diver carrying said Sea Hare to a location where I could then see it).
Another bizarre creature happened across my path, the Spotted Batfish (Ogcocephalus pantostictus). These benthic, “legged” fish are especially adapted for life on the bottom. They are distinct from frogfish, another legged benthic fish, in that their body is laterally compressed, giving them a similar appearance and shape to rays.