Reflections on the Salt Marsh in Autumn

The salt marsh that borders Cumberland goes through a noticeable change during the month of November.  This is when the dominant salt marsh spartina grasses turn from green to gold.  It’s this annual die back of mature spartina leaves and flowering stalks that produces the bio-mass needed to start the food chain in our coastal waters.  Salt marshes are biologically among the richest natural areas on the planet.  One acre of spartina produces five to seven times more protein than the same area of a Kansas wheat field.  However, the nutritional value of spartina is not realized until it decomposes and becomes a major component of the organically rich mud seen in the marshes at low tide.  So marsh mud, as miserable as it may seem to anyone trying to walk through it, is really wonderful stuff.

The decomposition process of spartina starts with bacteria.  Among these are the purple sulfur bacteria that look like an oil slick on the surface of the water.  This anaerobic life form actually lives under the mud that floats to the surface if the ground is disturbed and because of its oily appearance has been mistaken for pollution in some areas.  As dead spartina is digested by bacteria, it mixes with algae in the marsh to become a nutrient rich soup known as detritus.

A great number of animals feed on this abundant food source with the smallest of these detritavores being protozoa and nematode worms that are so tiny they can be selective in eating certain types of bacteria and algae.  However, larger animals like mud snails and fiddler crabs eat all components of the detritus soup.  The largest detritavores in the marsh creeks are mullet.  Large schools of these fish graze in the marshes over the summer but in the autumn when the water cools they move to warmer areas farther south.  Menhaden are another schooling fish that feed directly on detritus in the marsh.  The most commercially valuable detritavore we have around Cumberland are shrimp which actually spawn in the ocean but grow up in the salt marsh.

With such an abundance of grazing animals in these wetlands there are also a host of predators here to feed on them.  Blue crabs will feed on fish and fiddler crabs but may be eaten themselves by river otters or bottle nosed dolphins.  Dolphins feed mostly on fish though, and will chase schools of mullet and menhaden onto mud flats to capture them.  Several kinds of predatory fish like sea trout and red fish go after the bait fish as well, and fishing for these popular game species is often rewarding around Cumberland. 

There are many fish eating birds in the area such as ospreys, the only bird to dive totally feet first into the water to catch fish.  Along the creek banks egrets and herons are able to grab and sometimes spear fish with their dagger like bills.  Clapper rails and white ibis with their probe shaped bills are more adapted to feeding on mud snails and fiddlers.  The most voracious predator of fiddler crabs though are probably the raccoons that roam the marshes at low tide eating them.

This, of course, is just a sampling of all the animal activity in our salt marshes.  So when the green marsh grasses turn gold in November, I keep in mind what it could eventually lead to and when I trek into a wet, unstable salt marsh, I think of all the life forms below my feet that more often than not will end up well above my knees.

The Newcomer

Well I’ve seen some of their tracks from time to time and heard a few stories about people seeing them on Cumberland; although most of these sightings were dismissed as being another animal, but on October 25th the Greyfield tour actually got a good look at a coyote off the North Cut Road on the north end of the Island. 

Originally an animal of our western states; coyotes have moved into most all of the eastern states over the last few decades and are now well established in all of Georgia counties, so it was just a matter of time before they made their way to Cumberland.  But how could this have happened?  Only two ways:  they were either brought over by man or they swam over from the mainland.  The swimming story is certainly plausible because like other canines, coyotes are good swimmers and like their larger cousins the wolves, they have a great deal of stamina.  Coyotes also follow their noses like other canines, so could this be how they found Cumberland?  The prevailing winds here are from the east which means the mainland is usually down wind from the island.  The scent from a large dead animal could possibly be carried to the mainland a couple miles away over mostly tidal marsh. 

This kind of feeding behavior also brings up another characteristic of the coyote and that is they will eat just about anything.  Being both highly adaptive and secretive they can be equally at home raiding garbage cans in a city or chasing down deer in an isolated wilderness area.  However, it’s the impact on game animals as well as livestock that has turned so many people against this elusive animal.  As a matter of fact, just about every hunter and farmer I’ve talked with over the years hates coyotes.  One western sheep farmer that was suffering heavy losses of lambs to coyotes stated that “Nature just can’t be safe with coyotes around”.  Even though the coyotes were more a natural part of the land than the sheep.  But it’s been this competition between people and coyotes that has reached epic proportions in some areas and condemned the wily coyote to a life on the run.

So how will this newcomer impact Cumberland?  Well; we don’t have sheep but we do have hogs that need to be eradicated and coyotes might take some of the smaller pigs.  But they won’t stop there.  These highly effective predators will also go after white-tailed deer along with many other native species.  With a native predator this keeps the system in balance.  But should the coyote be considered a native predator?  Even though they are native to many parts of North America, they are relatively new to the southeast and really new to Cumberland; (so new I don’t have photos of them yet for the blog).  However, some biologists have suggested they might be filling a niche left open when the native red wolf was nearly driven into extinction in this area sometime during the 1800’s.

Whatever the case, coyotes could change the dynamics of wildlife populations on the Island while providing a challenge to photograph in the future.