Saturday, March 5, 2016

Exploring Low Tide

As you might know, I went on a road trip over my Winter Break. Much of it was spent exploring the beautiful South Carolina Lowcountry. I spent 4 days of my time in the Lowcountry camping on Hunting Island State Park on the southern tip of South Carolina.

Hunting Island Beach
Driftwood on the beach at Hunting Island.
This isn't the first time I've been to Hunting Island State Park; the ornithology class I was taking last semester stayed here while on a birding trip (Link). It's an absolutely amazing place that I wanted to revisit, so I decided to come back on my break. I spent most of my time birding around the area, but whenever I wasn't birding, I was exploring the island's beach. First, some background on the setting. Hunting Island is a subtropical barrier island in the Atlantic Ocean. The natural beach is approximately 4 miles long. As with elsewhere, Hunting Island experiences 3 types of tidal cycles: daily, monthly, and annual. These are all caused by different types of interactions between the Earth, Moon, and Sun. The most obvious tidal cycle is the daily cycle. This cycle is caused by the interplay between the Earth's rotation and the Moon's gravity. This results in 2 daily high tides and 2 subsequent low tides. The tides can make the beach on Hunting Island go from only 10 or 20 yards wide during high tide to 100+ yards wide during low tide. I opted to explore during low tide, as many "goodies" are visible once the intertidal zone is exposed.

Forbes Sea Star
Until this trip, I've never had the chance to really explore a beach. I honestly didn't know what kinds of things to expect, especially in South Carolina. I was absolutely flabbergasted to see Sea Stars. One part of the beach during low tide had some rocky tide pools, and these tide pools were teeming with dozens of sea stars and various other life. All the sea stars were one species, the Forbes Sea Star (Asterias forbesi). The Forbes Sea Star can be found in Atlantic coast intertidal zones ranging from Maine down to the Gulf of Mexico. It has a characteristic orange madreporite. The madreporite (the round orange thing near the center) is a specialized opening which all sea stars have. The madreporite is essentially a valve which allows sea water into the specialized water vascular system which run throughout the sea star's body. Sea stars actually use sea water essentially as a means of locomotion in a rather complex process. You can read more about this process and the madreporite at The Echinoblog.

Starfish South Carolina
The Forbes Sea Star is a molluscivore, meaning it feeds on mollusks. Specifically, the Forbes Sea Star feeds on bivalve mollusks, which are mollusks that are enclosed by two shell parts which are attached by a hinge. Bivalves include commonly-known mollusks like clams, oysters, mussels, etc. The Forbes Sea Star tracks down bivalves by honing in on the chemical "smell" of bivalves. Once it senses a bivalve, the sea star will crawl toward it. Upon reaching it, the sea star will then grab the bivalve with its tube feet (which you can see in the photo above). The sea star then uses its tube feet to pry the bivalve's shell open, exposing the helpless mollusk inside. This is when things get a little strange. Instead of "swallowing" the squishy mollusk body like you might think it would, the Forbes Sea Star does things a bit differently. It pushes its stomach out of its body and up against the body of the mollusk where it then excretes digestive enzymes that begin to break the mollusk down. The stomach then absorbs the resulting nutrients before getting pulled back into the sea star's body. Pretty crazy, isn't it?

Bunodosoma cavernata
Another common sight in the tide pools I explored was the Warty Sea Anemone, Bunodosoma cavernata. Sea anemones are actually animals in the Order Actiniaria. The sea anemones are Cnidarians (Phylum Cnidaria), and as such they are related to jellyfish, corals, tube-anemones, and the like. The Warty Sea Anemone is a more southerly species in the US, ranging from North Carolina down throughout the Caribbean. The venom of the Warty Sea Anemone isn't toxic to humans like some other sea anemone venom can be, and so they pose essentially no threat to the beach goer. If you decide to gently poke one, you can witness their reactionary defensive behavior which consists of quickly pulling its tentacles in to a tight ball.

Live and dead Sand Dollar
Sand Dollars, with a live individual on the left, and a dead individual on the right.
As I moved away from the tide pools and walked along the beach, I often came across individuals of a species of Sand Dollar called Mellita isometra. Common names for this species include the Keyhole Sand Dollar and the Five-Holed Sand Dollar. Sand Dollars are actually a type of sea urchin that have a flattened body which helps them easily burrow under sand. Mellita isometra is a species which can be found in soft intertidal zones to shallow depths of ~100 meters from Massachusetts down to Florida and the Bahamas. Most of the Sand Dollars that people find along the beach are actually the "skeletons" of dead individuals, called "tests." To see the difference between a live Sand Dollar and a dead one, look at the photo above. The Sand Dollar on the left is alive; notice its purple coloration and fuzzy appearance. On the right you have the test of a dead Sand Dollar. Notice how it's smooth and a pale creamy color; it's much different looking than a live individual!

Knobbed Whelk South Carolina
Of course, one of the most common sights on the beach are various mollusk shells. There are, however, few shells in South Carolina as large and eye-catching as the Knobbed Whelk, Busycon carica. I was wading through a shallow channel on the north end of Hunting Island when I came across my lifer Knobbed Whelk. The large shell sitting in the sand easily grabbed my attention. Amazingly, this is a small Knobbed Whelk. A full grown adult will be between 5 and 12 inches long, while this one was only about 4 inches.

Knobbed Whelk
So what exactly is a whelk? A whelk is essentially just a type of sea snail. More specifically, they are sea snails in the family Buccinidae (the true whelks), but some sea snails in other families have "whelk" as part of their common name (which is one of the many issues with common names). The Knobbed Whelk can be found in near-shore environments ranging from the intertidal zone to 50 or so meters deep. Their range extends from Massachusetts to northern Florida, and in South Carolina they are the most common of the whelk species present (there are 4 total in South Carolina). They are a predatory snail that feeds on bivalves such as oysters and clams.

Hermit Crab South Carolina
As with all creatures, Knobbed Whelks eventually die. After their soft body decomposes, a nice empty shell is left over. That shell makes for a great hermit crab home. In fact, the hermit crab in the photo above is using a small Knobbed Whelk shell as its temporary home. Hermit crabs are a type of crustacean, but they aren't actually true crabs. Hermit crabs are kind of their own thing. Most crustaceans have a completely hard body due to it being nearly all calcified, but the hermit crabs have a non-calcified, and subsequently soft, abdomen. This soft abdomen is a very big weak spot for the hermits, and they have come up with an easy fix: crawl into an empty shell! Most often a hermit crab will choose a snail shell of some sort, like the individual above. By using this shell as a mobile protected "home," the hermit crab can better prevent becoming an easy meal for a hungry predator.

Hermit Crab

There are several species of hermit crabs in South Carolina, and I have essentially no knowledge when it comes to identifying crustaceans. I think this is a Long-Clawed Hermit Crab, Pagurus longicarpus, however I could be totally wrong. Another common species is the Thinstripe Hermit Crab, but this individual lacks the characteristic pinstripes. Another possibility is the Broad-Clawed Hermit Crab, but its claw doesn't look nearly large enough. If anyone can help me positively ID this species, please leave a comment!

Blue Crab in Sand
Of course, if I'm going to talk about hermit crabs, I should probably talk about the true crabs! This guy was a surprise find. I was in one of the tide pools looking around when I saw something just barely sticking out of the sand. At that point in time, all I could see was the outline of a round object. I thought it might be some sort of bivalve, so I put my hand under it and attempted to pull it out of the sand for a closer look. Suddenly, the object erupted in a flurry of movement, stirring up the sand and clouding the water. I jumped, and then felt a pinch on my hand. Oops, it was a crab. The sand settled to reveal the scene above - a now-obvious blue crab sitting half buried in the sand. My colleague Alayna Tokash identified this as the Atlantic Blue Crab, Callinectes sapidus, which is often just referred to as the "Blue Crab" (although there are several species of blue crabs in the Atlantic).

Blue Crab South Carolina
The Atlantic Blue Crab is a commonly consumed crab, and is also a very economically important species for the Atlantic Coast. However, there's some trouble. The Atlantic Blue Crab population has been declining for some time. It is estimated that the population declined from 900 million individuals to approximately 300 million individuals from the mid-1990's to 2004. In the Chesapeake Bay region, where the Atlantic Blue Crab is most heavily harvested, the population is estimated to have decreased by nearly 70% over the past few decades. Overharvesting is, as you might have guessed, a major problem, but several other factors, including diseases and habitat degradation, are to blame as well. These declining trends suggest an upcoming battle between conservationists advocating for the protection of the Atlantic Blue Crab and the crabbers who rely on this species to make a living. Hopefully it doesn't get to that point, but this is a scenario that is played out much too often nowadays...

I know this is a very different subject matter than what I normally get the chance to write about, so hopefully you enjoyed it! Thanks for reading!

Tuesday, March 1, 2016

An Exciting Snake on an Exciting Road

As I've mentioned in previous posts (here and here), I took a road trip over my Winter Break to South Carolina. I spent the first few days outside of Charleston exploring the vast Francis Marion National Forest. Francis Marion NF is a large reserve (258,864 acres) that contains a great example of the Middle Atlantic coastal forest ecoregion. Francis Marion NF is one of the most biologically and ecologically diverse parks in the southeastern United States, with swamps, freshwater marshes, salt marshes, upland Longleaf Pine savannas, and more.

Old Georgetown Road Francis Marion National Forest
Before we get to the exciting snake, I want to take a short history tangent. Nestled in the eastern side of Francis Marion NF, off US Route 17 and only about 2 miles from the Atlantic Coast, you can find an unassuming dirt road (pictured above). Now, there are many dirt roads like this throughout the park, but I made a trip to travel down this specific road. This road, now named Old Georgetown Road, has an incredibly long and incredible history. It started out as a trading path (named the Broad Path) used by the Sewee Native Americans. Then the British came. They founded Charleston in 1670, and there came an obvious need for a road to connect Charleston to the other colonies in the north. King Charles II ordered for a road to be created that connected Charleston, South Carolina, to Boston, Massachusetts, to fulfill this need. In this part of South Carolina, the colonists chose to use the already-existing Sewee Broad Path that went up the coast. By the early 1700's, this 1,300 mile dirt/mud/sand road was finished, with Charleston and Boston connected. It was the road to use when traveling up and down the coast. For example, in 1791, then-president George Washington decided to travel to all of the new states. He, as you might have guessed, traveled to South Carolina via this road. Most of this 1,300 mile road was eventually paved and slightly rerouted, with the vast majority of it becoming US Route 17. What makes this specific section of the "King's Highway" special is the fact it was never paved over. This 6.6 mile stretch is one of the last remaining unpaved, original sections of the King's Highway (as it became called in the 1900's). In fact, it's one of the few remaining unpaved sections of colonial period roads still left in the US at all. As a history geek, this was one of the most exciting roads I've ever driven down!

Corn Snake South Carolina
The road became even more exciting when I saw a snake laying in the middle of it! As I got out of my car, I could tell it was a species of snake I've never seen before. Upon getting closer, I saw that it was a Corn Snake! Francis Marion National Forest is a treasure trove of reptiles, with the Corn Snake being just one of the 58 reptile species that call the park home. As an Ohioan, that's a stunning diversity of reptiles, as there are only 42 species of reptiles here in Ohio.

Corn Snake
The Corn Snake, Pantherophis guttatus, is a species of non-venomous snake found throughout much of the Southeastern United States. They can be found in a variety of habitats such as overgrown fields, forest openings, palmetto flatwoods, and more urban areas such as around barns and sheds. Within a given habitat, the Corn Snake utilizes a range of space; it will climb trees, bask on rocks, explore underground mammal burrows to hunt, and visit everywhere in between. They feed primarily on rodents, so they can essentially be found wherever there are rodents.

Corn Snake Francis Marion
Corn Snakes are very popular in the pet trade, and one of the reasons for that lies in their beauty. The "wild type" coloration (which is what this guy is) is a stunning orange, red, and yellow. This photo also shows their slight iridescence (which many other snake species exhibit). A large variety of other color types have been selectively bred for in the pet trade, but I still think that the wild type is the best.

In my opinion, the Corn Snake is one of the most beautiful species of snake in the United States. Even if you aren't a snake lover, you can't help but appreciate the stunning coloration on this species.

Thanks for reading!