For most people, the beach is a place for sun, sand and surf. But when you look at from a naturalist’s perspective, it’s a unique and specific habitat. Many of the animals and plants that live here are very much adapted to it, and cannot simply move to another place. When we modify beaches for our own enjoyment, it’s usually to their detriment and destruction.
Every beach is different. Look at shorelines around the world and you’ll find places where the water meets sheer cliffs, rocky expanses, mangrove swamps, featureless mud and even ice. Since the beaches closer to home are mostly sand with relatively low-energy waves, that’s the habitat I’ll be focusing on.
These tiny bivalves (two shells that hinge, like a clam or scallop) live right in the surf zone, from the waves out to only a hundred or so feet from shore. On a healthy Florida west coast beach, they can be incredibly abundant. Every wave that washes up will toss hundreds up onto the sand, where they quickly dig in using their muscular foot.
Coquinas come in a huge range of colors: Yellow, orange, pink, creamy white, gray, blue and purple. Like other bivalves, they are filter feeders. After burrowing into the sand, they extend a siphon up to the water and suck water in, then filter out any edible particles and spit out the water.
Although each coquina is just a little thing, usually less than an inch long, their dense populations make them an important food source for many species. Plovers and pompano is particular feed on them in huge numbers. They can also be food for humans. When I was a kid, we sometimes collected coquinas on Englewood Beach to make chowder — a Florida Cracker recipe passed down from my mom’s family.
More properly called a mole crab, this is another surf zone species that can’t live elsewhere. Like the coquina, they dig into the sand to avoid predators — and like the coquina, they are found in huge numbers on healthy beaches, where they are again important food for birds and fish.
But unlike coquinas, mole crabs aren’t filter feeders. Instead, they sift through the sand seeking any small edible bits. These can be of animal or plant origin — mole crabs aren’t picky. Their main importance to humans is as fishing bait, although in some other parts of the world, they are regarded as crunchy and tasty snacks.
There are many species of univalve mollusks (basically, snails) that can be found on local beaches. Collecting their shells is one of the more popular shore pastimes. While the orange-shelled fighting conchs are among the most common and visible, other species can be regularly found: Lightning whelks, banded tulips, lettered olive, horse conchs and many others.
Snails have widely varying food habits. Some are mainly vegetarian and hoover up algae growing on rocks or other hard surfaces. Some are scavengers and will take what they can get. Some are predatory and drill holes into other mollusks to get at the soft bits inside. One group, the cone shells, even hunts small fish using venomous harpoons.
The only thing they truly have in common is that beaches with a wider diversity of other living things will also have a broader spectrum of univalve species.
Long a favorite beach souvenir, sand dollars are echinoderms and related to the sea stars (which we also find on local beaches, but not as often). Sand dollars are really modified sea urchins, just flatter. Like their urchin relations, sand dollars are grazers and feed mainly on algae.
Dead sand dollars are white, but live ones are brown and covered with short, fuzzy spines. The spines are used as tiny legs, allowing the sand dollar to slowly cruise across the top of the sand or dig down into it. When collected, live sand dollars will produce a yellow fluid that can stain your hands.
While many crabs can be found in the water off local beaches, the ghost crab is a shorefront specialist. These white crabs, with a leg span of about 4 inches, dig long burrows into the sand above the high-tide line. From this home base, the crab will forage along its stretch of beach. The crabs are territorial and spend much of their time chasing off rival crabs.
Ghost crabs are both scavengers and hunters. They will feed on pretty much any meaty foods. In summer and fall, hatchling sea turtles often fall prey to them. While this makes many people upset, it’s nature’s way of ensuring only the strongest babies make it to the water. The weak are slow, and predators collect them.
Now if your favorite beach is missing some or all of these things, there are good reasons. One cause is over-cleaning. While we may like the look of a bare sandy strip, healthy Florida beaches should have some wrack (the dead vegetation that washes up). Wrack is a major nutrient source and helps keep everything on the beach fed.
But beach renourishment is the big one. The sand brought in from offshore is siltier than what’s naturally found on our beaches. That silt clogs the gills and filter-feeding mechanisms of surf-zone dwellers, killing them. Worse, sand is dumped tight on top of them. That kills them too.
So the main problem with our beaches is that we’re loving them to death. It’s a painful truth, but one we have to accept.
Capt. Josh Olive is a fifth-generation native Florida Cracker and a Florida Master Naturalist, and has been fascinated by all sorts of wild things and places since he was able to walk. If you have questions about living with wildlife, contact him at Publisher@WaterLineWeekly.com or 941-276-9657. You can also follow him on Instagram @florida_is_wild.