Life in the Saltmarsh - Part 2

 

Saltmarsh in summer.
McIntosh County, Georgia. 

Southeastern saltmarshes are like a string of emeralds strung along the coast.  They are found up coastal rivers, lining estuaries and in the lee of barrier islands. The water in saltmarshes is brackish with a mix of fresh water from rivers and seawater coming in on the tide.  Saltmarshes are highly productive ecosystems and in the southeast this productivity starts with the flowering plant Saltmarsh Cordgrass, Spartina alterniflora. Other plants, animals and microbes contribute to the stunning biodiversity of this unique habitat. 

Eastern Oysters (Crassostrea virginica) starting a saltmarsh oyster bar.
Huntington Beach State Park, South Carolina. 

A large oyster bar at low tide.
Huntington Beach State Park, South Carolina. 

Eastern Oysters (Crassostrea virginica) are bivalve mollusks that colonize the mud of the marsh and often form large bars.  Oyster bars stabilize the saltmarsh by catching sediment and slowing erosion.  Since mature Eastern Oysters are attached to the mud their food must come to them.  Eastern Oysters are filter feeders, taking in large volumes of water, straining out plankton and releasing the filtered water back into the marsh.   Eastern Oysters are eaten by many animals including people.  Ancient wisdom held that we should eat oysters only in months that have the letter R in them.  In other words, do not eat oysters in May, June, July and August.  There were a variety of good reasons to do this in previous centuries when all oysters were wild harvested and refrigeration was nonexistent.  Oysters spawn in the warm months and this gives them a bad taste.  Also, the filter-feeding oysters could accumulate toxic red tide organisms and slow transportation could deliver spoiled oysters to market.  Now, oysters are on the menu year-round with rapid refrigerated transport and farmed oysters that are sterile and do not spawn. 

American Mink (Neogale vison) hunting on a rock jetty
adjacent to a saltmarsh. 
Huntington Beach State Park, South Carolina. 

American Minks (Neogale vison) are mammals related to weasels and otters.  They inhabit much of North America including the edges of saltmarshes where they catch fish, invertebrates, rodents and birds.  American Minks make dens in burrows, among tree roots or in crevices between rocks where the females raise their young.  Domestic American Minks are still grown on farms and are skinned to make fur coats.     

Male Atlantic Marsh Fiddler Crab (Minuca pugnax). 
The crab is standing by the mouth
of his burrow and surrounded by mud balls.
Edisto Beach State Park, South Carolina. 

Atlantic Marsh Fiddler Crabs (Minuca pugnax) live in the mud of the marsh.  Females Fiddler Crabs have two small front claws, and the males have one large claw, the fiddle, and one small front claw.  Both males and females use the small claws to pick up particles of mud and eat the algae that coats the sand grains.  The crabs then roll the cleaned grains into mud balls and deposit them on the surface of the marsh.  Male Fiddler Crabs use their large claw to show off for females and fight with other males. This combat between males gave this crab its specific name pugnax, from the Latin for fight.  Pairs of Fiddler Crabs mate in burrows and the larval forms are released into the water at high tide. Larvae live a planktonic existence until they transform into the adult form of the crab.   

 

Blue Crab (Callinectes sapidus).
Isle of Palms, South Carolina.

Another crab of the saltmarsh is the Blue Crab (Callinectes sapidus). Blue crabs have the most apt of scientific names which translates from the Latin as tasty, beautiful swimmers.  They are beautiful and delicious.  Blue Crabs have a greenish brown carapace and blue claws and legs, including the rear paddle-shaped swimming legs.  Blue Crabs are caught on the Gulf and east coasts of the United States. Chesapeake Bay has traditionally been the heart of the Blue Crab fishing industry but overharvesting and pollution have reduced their numbers.  Many Blue Crabs eaten at the Inner Harbor of Baltimore are trapped in Louisiana.  

Seaside Sparrow (Ammospiza maritima).
Huntington Beach State Park, South Carolina. 

Several species of sparrows are saltmarsh specialists.  Seaside Sparrows (Ammospiza maritima) live in saltmarshes from Texas to New England.  These hefty sparrows have a large, pointed beak, a streaked breast, and a yellow spot in front of the eye.  Seaside Sparrows feed on Spartina seeds and insects they catch on the marsh grass.  

Saltmarsh Sparrow (Ammospiza caudacuta) on
a causeway next to a saltmarsh. 
Huntington Beach State Park, South Carolina. 

Saltmarsh Sparrows (Ammospiza caudacuta) also inhabit saltmarshes.  We see Saltmarsh Sparrows wintering in the southern marshes, but these birds breed in the Mid-Atlantic and northeastern coastal states.   Saltmarsh Sparrows are brown with streaks on the breast, orange on the face and gray cheeks. The population of Saltmarsh Sparrows has declined over 80% in the last 25 years.  Threats to this sparrow include habitat loss and sea level rise.   

Saltmarsh with Spartina behind the dunes.
Huntington Beach State Park, South Carolina. 

As with most good things, climate change is threatening saltmarshes and their inhabitants.  Sea level rise caused by the melting icecaps is the most imminent threat to saltmarshes.  The sea on the North Carolina coast has risen about one foot since 1950 and is now rising about an inch every two years.  Higher sea levels pour more salt water into the marshes.  Higher seal levels will inundate the marsh and higher salt concentration will kill the Spartina. Salt marshes can invade higher ground, but it is unlikely the newly formed marshes will keep up with the loss.  With every visit to a saltmarsh I am dazzled, but I also feel like it is slipping away.