Decomposing Rocks and Discarded Exoskeletons

However improbable it may sound, deep inside this pale as a lily, born and bred midwesterner beats the heart of beach bum. I may never have what people will call a "tan," but good luck getting me out of the water or away from the shore once I’m there. I will gladly haul my beach gear on the subway. I regularly try to talk my family into moving our Christmas celebration from St. Louis to St. Lucia. I actively track real estate prices in the Caribbean. You get the idea.

Like virtually everyone with a pulse, I seem to be unable to resist the urge to collect seashells while I’m frittering the day away on the sand. Recently though, while getting ready for a trip to Cocoa Beach, Florida (where I was meeting my parents so they could see my work at Kennedy Space Center) I realized that I knew practically nothing about the creatures that had made those shells. And, come to think of it, I didn’t know much about a lot of what I see at the beach. The only thing left to do was buy some books, repack my suitcase to accommodate said books, nearly miss my plane (classic Emme), and get ready to be the nerdiest beach bum there ever was.

Here’s some of what I found:

Sand Ok, obviously I found sand. That in and of itself may not sound terribly exciting, but think of it like this: those inconvenient grains that invariably get stuck in every conceivable crevice of your flip flops and cling to your beach towel despite several rounds of vigorous shaking, are actually bits of decomposed rock. Sand is mostly made up of the remains of rocks that have been weathered down for an average of a couple hundred thousand years. There’s also a small amount of shelled sea critter bits and the hardened remains of other animals and plants thrown in for good measure.

The sand along each stretch of beach is unique—the result of the rock composition at its source (for beaches in Florida, that’s by and large the Appalachian Mountains) and the coastal conditions where it ended up. The daily action of waves and tides, the occasional large storm, and longer-term events like sea level change all play a role in a beach’s sand profile. The sand on most beaches in the eastern US is made predominantly of quartz with a little feldspar thrown in. Those minerals are not only abundant in the Earth’s crust, they’re also hard enough to stick around long after others have dissolved or been pulverized into dust.

Seashells Seashells are the exoskeletons of sea critters. They are made mostly of calcium carbonate (aka TUMS) with just a dash of protein, the same recipe that the first shelled organisms used when they evolved some 500 millions years ago. Animals build their shells by pulling calcium out of the seawater. It’s a pretty cool process that we still don’t fully understand, but it has some interesting possibilities for the world of biomimetics. Many of the shells that wash up on shore contain clues about how their former residents met their end—holes where predators drilled through the shell or long grooves made by parasitic worms are fairly common sights.

  • Arks I found shells from at least three species of these clams, including a few blood arks (Anadara ovalis). Unlike most clams, which have blood that is clear or bluish, blood arks have red blood. The color comes from hemoglobin, the same molecule that carries oxygen in our blood.
  • Lightning whelk (Busycon sinistrum) There are few phrases I enjoy typing more than ‘large predatory sea snail,’ so I was excited to find a few fragments of these guys. Lightning whelks are the southpaws of the sea; the leftward opening on their shells distinguishes them from most other marine animals.
  • Eastern white slippersnails (Crepidula atrasolea) These snazzy creatures start life as males, then change to female when conditions are right, i.e. when there are other slippersnails nearby to mate with. (An ability that I am sure would make dating in New York so much simpler.) Their shells are easy to spot because they have a shelf-like projection on the inside.
 Slurp, slurp "Tasty!"- The creature that ate these guys. (Image via  Verobeachgal  on Flickr)

Slurp, slurp "Tasty!"- The creature that ate these guys. (Image via Verobeachgal on Flickr)

Salle’s auger (Hastula cinera) Despite some pretty solid search attempts, I wasn’t able to capture all that many live shelled critters. But one morning my dad dug up this small sea snail from the surf zone. It’s a shame it wasn’t auger mating season because according to my guide book “their summer mating swarms are in the style portrayed by Burt Lancaster and Deborah Kerr in From Here to Eternity, with embracing pairs rolling in the swash zone" and that seems like something you don’t want to miss.

 Looks similar to me.

Looks similar to me.

Ghost crabs (Ocypode quadrata) The ghost crab lived up to its name and stealthy reputation during my visit. I saw quite a few of their characteristic burrow holes in the dry sand of the dunes, but only ever spotted one as it scurried under our deck and out of sight. They live so very close to the water and need to stay moist in order to breathe, and yet they can’t swim. This leads me to wonder if there is an untapped market for ghost crab-sized life preservers.

 I'm fairly certain one is not supposed to go digging around in the dunes, but Poppers and I couldn't resist trying to excavate a ghost crab burrow. It was highly unsuccessful in my opinion because we didn't find a single crab. Poppers, however, got to throw shovels full of sand on me, so it was mission accomplished for him.

I'm fairly certain one is not supposed to go digging around in the dunes, but Poppers and I couldn't resist trying to excavate a ghost crab burrow. It was highly unsuccessful in my opinion because we didn't find a single crab. Poppers, however, got to throw shovels full of sand on me, so it was mission accomplished for him.

Red Mangrove (Rhizophora mangle): These guys look more like a crazed shrub than your garden variety tree (HA), but despite their haphazard appearance, they know exactly what they’re doing. Red mangroves are incredibly well adapted to their environment. They grow in the soft muck that builds up along coasts and estuaries, needing very little fresh water or even stable ground to survive. I found a seed pod floating in the waves, which it turns out, it can do for over a year. The pods drift out from their parent tree and then drift off. The tip of the pod eventually becomes waterlogged, which pulls it toward the bottom where it can take root.

Skate egg cases Skates are related to sharks and rays, and like those creatures they have bodies made of cartilage. Unlike some sharks and all rays who have live babies, skates lay eggs encased in a capsule that looks like a seed from an alien tree. The embryo inside is pretty crafty—when it senses another creature’s electrical field, it can shut down all of its functions—including its heartbeat and respiration—until the would-be predator moves on. I also hear they’re quite tasty. I ordered a skate taco during a recent taco expedition to Queens, but they were out. I guess I’ll have to go back.

 Not my hand.  Or my picture , for that matter.

Not my hand. Or my picture, for that matter.

There was a multitude of other creatures and plants as well. Bottlenose dolphins, two different kinds of seagulls (one of which—the royal tern—my mom nicknamed “The Danny Devito Bird”), brown pelicans, and mullets (both the fish and the haircut) all made an appearance during my five days of beach basking. There were sea oats, seashore dropseed, and railroad vine growing in the dunes. And there were boatloads of green algae—which I initially mistook for a weird kind of seaweed—covered in tiny air-filled bladders that help the bunches float in water.

Unfortunately, despite Cocoa Beach being fairly clean and really pretty healthy, I also found a good deal of trash in the sand—bottle caps, small bits of plastic, cigarette butts. Part of appreciating the beach is taking care of it. So please, pick up your trash and be a responsible beachgoer. Some of us are trying to buy beachfront property and between the litter, the hurricanes, and the sea level rise, you all are really harshing my property-buying buzz.

 Farewell for now Cocoa Beach. I shall think of you often in the cold, dark, slushy months ahead...

Farewell for now Cocoa Beach. I shall think of you often in the cold, dark, slushy months ahead...