(gentle music) ♪ (birds singing) (crickets chirping) With nearly half a million acres, South Carolina has more marshland than any state on the East Coast.

This rich and diverse ecosystem brimming with all types of marine species has a dynamic rhythm to it.

Life here revolves around the ebb and flow of the tides.

It is the heartbeat of the saltwater marsh, bringing and taking with it a swarm of activity.

(crickets chirping) Those who have learned to adapt to its changing environment have been able to exceedingly grow in numbers and thrive in some of the wildest ways.

♪ (gentle music) (crickets chirping) The saltwater marsh serves many purposes, aside from providing a home to countless organisms.

They act as filters for the environment, removing toxins and sediment from the water.

Marshes also protect the mainland by acting as a buffer, delaying and absorbing storm surges.

Economically, the salt marsh is extremely valuable to the South Carolina commercial fishing industry.

Three quarters of all species harvested as seafood spend at least part of their lives here.

One of the most noticeable features of the marsh is the rampant marsh grass called "Spartina."

This plant has little to no competition or predators.

Few other plants can withstand the salinity and virtually no grazing animals can reach it because of the marsh's soft surface called "pluff mud."

When Spartina leaves die in the fall, they break down into an organic soup known as detritus.

Small invertebrates and microscopic organisms feed on detritus and start a food web that extends to all the animals of the marsh.

One of these creatures is the fiddler crab, named so for its unusually large claw that resembles a violin.

(whimsical background music) Their sexually dimorphic claw is only found in male crabs and can account for 65% of their body weight.

♪ Far too big to eat with, the claw or "chelipid" is used for fashion more so than function.

Male fiddler crabs rhythmically wave their major claws up and down to attract females for mating and to intimidate potential male competitors.

♪ Their burrows, reaching several feet underground, help aerate the pluff mud and are used for mating as well as seeking refuge from predators and the tides.

♪ A similar species called the Squareback Marsh Crab, has a more daring approach when it comes to evading the elements.

Also known as "wharf crabs," they've adapted to become expert tree climbers in intertidal zones.

When they're not in the trees, most of their time is spent eating insects and soft maritime vegetation on the forest floor.

Like most crustaceans in the marsh, they too play an integral part of the ecosystem.

With over half the country's population living near the coast, the cumulative impact of water flow alterations and pollutants is the greatest threat to the saltwater marsh.

Since 1979, the South Carolina Department of Natural Resources has been keeping tabs on the local crustacean population throughout the state.

Once a month, this division of marine biologists in Charleston board their research vessel, the "Silver Crescent," and sail in South Carolina's larger creeks, rivers and open waters to conduct sampling excursions.

(seagulls squawking) To get these samples, a 20 foot trawl net is deployed and dragged at various depths to catch shrimp, blue crabs, and all manner of marine life.

♪ Once the catch is hauled in, the crew begins analyzing and recording the size, sex and maturity of key species, as well as making observations about the health status of these animals.

A water sample is also collected to measure the temperature and salinity of their environment since these factors can influence population abundances and movement patterns.

(seagulls squawking) The data collected by this long term survey is not only important for determining the overall health of the populations and habitats, but is also crucial in deciding commercial seasons.

♪ It's efforts like these that will keep unique environments like the saltwater marsh wild for years to come.

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