As you watch the male fiddlers waving their massive claws,
the tide approaches its lowest point, during which one of the
most fascinating marsh communities may become visible.
Gaze into the now-shallow water, and vibrant colors of yellow,
red, purple, white, and orange will catch your eye. These are
gorgonians, or soft corals, commonly referred to as colorful
sea whip (Leptogorgia virgulata). They are colorful branching
corals that sit attached to a hard, immobile object. Each coral
will extend hundreds of tiny polyps to collect floating organic
matter in the gently flowing water column.
It is unlikely you will ever find a sea whip alone. If you look
closely—very, very closely—you can find some incredible
symbiotic partners. Disguised as small bumps attached to
the thin branches of the sea whip, snails slowly graze on the
corals. These are one-tooth simnias (Simnialena uniplicata),
and the shells of these snails will match their host’s color. So,
a purple sea whip will have purple simnias, a yellow whip
has yellow simnias, and so forth. The snails will often take it
a step further by exposing their mantle, which resembles the
polyps of the sea whip, creating a seamless transition from
sea whip to snail shell. The snails are grazing on the polyps
of the sea whip, exposing the inner skeleton of the coral and
making way for another organism to set up shop, the sea whip
barnacle (Conopea galeata). Barnacles need hard places to
anchor where they can grow and consume passing organic
matter from the water column. As the barnacle settles on
to its gorgonian home, the sea whip regenerates its tissues,
eventually covering the barnacle in polyps. This provides the
barnacle with spectacular camouflage, as there are very few
animals that graze on sea whips, except for the one-tooth
simnia, of course. But without this predation, the barnacle
finds a cozy and colorful residence on the sea whip.
By now, the oyster beds will be fully exposed, and an
entirely different population is available for exploration.
Oysters are ecosystem engineers and are pivotal to the
health of our marshes. They grow in dense communities
constructing nooks and crannies where invertebrates
and small fish can find refuge from predators. Oyster
communities also passively and actively collect a ton of
SUMMER/FALL 2018 • VOLUME 40
organic matter that feeds not only the oysters but also the
residents hiding in the beds. This is apparent on the fringe of
the oyster reef during low tide. It will likely be riddled with
fish that are anxious to take advantage of the shelter and blue
crabs (Callinectes sapidus) eager to forage for food.
If you look closer, or even pick up a detached chunk
of oysters, you can find additional organisms that take
advantage of these reefs. You might find a small, bright red
shrimp called a peppermint shrimp (Lysmata wurdemanni).
This shrimp scavenges the oyster bed but will also clean
skin parasites from small fish that visit the place. When they
are disturbed, other small crustaceans such as mud crabs
(Panopeus herbstii) and green porcelain crabs (Petrolisthes
armatus) will tuck themselves away between the crux of
two shells. When not threatened, both will come out and
forage in two very different ways. The mud crabs will move
through the oyster bed seeking small mollusks, crushing
their shells with powerful claws. The green porcelain crab
is equipped with two large feathery mouthparts that it uses
to collect zooplankton by fanning the water into its mouth.
It is only recently that the green porcelain crab arrived in
South Carolina’s estuaries. As a result of warming water
temperatures, the crabs have settled in South Carolina,
and over 10,000 of them can reside in every square meter
of an oyster bed.
The salt marshes surrounding Kiawah hold an incredible
diversity and abundance of life. It is crucial to recognize
and understand these tiny communities because each has a
significant impact on this planet. These tiny organisms clean
our waters, filtering out pollutants and consuming waste
products and decay. Not only that, they feed larger organisms,
many of which we watch, like dolphins, and many of which
we eat, such as redfish and flounder. As much as two-thirds
of the fish that ends up on your dinner plate was reliant upon
the richness of a salt marsh for at least a portion of its life. So
the next time you’re driving over the Kiawah River bridge, or
if you’re visiting the salt marsh, via kayak, paddleboard, or
boat, throw out a big thank you for the intricate networks
that make this place and this world so wonderful. NK
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