Not many landscapes have had a famous poem dedicated to them. One such, of course, are the Golden Isles of the Georgia coast: sea islands surrounded by expanses of salt marsh that turn from green to yellow-brown in the chill of autumn.
Photo of the author sampling in a 'golden' cordgrass marsh near Marsh Landing on Sapelo Island, fall 1976.
Sidney Lanier's poem 'The Marshes of Glenn', composed in 1879, is a romantic paean to the natural beauty of coastal Glenn County. As he described it, a place:
'By a world of marsh that borders a world of sea.'
Scientific study of Lanier's beloved marshes only got going in the mid-20th century, when Professor Eugene Odum at the University of Georgia (UGA) in Athens, who is widely regarded as the patron of the field of ecosystem ecology, persuaded R.J. Reynolds, the owner of Sapelo Island, to convert the offices and dairy barn on the south end of the island into a research station, which became the University of Georgia Marine Institute.
Aerial view of the University of Georgia Marine Institute on the south end of Sapelo Island, where ground-breaking research on salt marsh estuaries has been done since the mid 1950's. The main laboratory building (and former dairy barn) is on the right, apartments for visiting scientists on the left, office and work buildings on either side. The tidal slough behind the Marine Institute is Barn Creek, named for the gray shed on the far right where Howard Coffin had a shrimp and oyster processing facility during his time on the island. Photo taken by E. Sherr from a small plane, August 1978.
Among the first scientists to live on the island and investigate the surrounding salt marsh estuaries were Lawrence (Larry) Pomeroy and John Teal, who arrived in the 1950's. They found rats scampering in recently vacated cow stalls still filled with hay in the main laboratory building. But they and other scientists who came to the island forged ahead, and understanding of the marsh ecosystems grew apace.
A major goal of the investigators was to establish how the expanses of productive Spartina (cordgrass) marsh nourished the animals that lived in the estuary, including commercially important fish, shrimp, and blue crabs.
Teal carried out a landmark study of the ebb and flow of plant carbon in Georgia salt marsh estuaries. A wooden walkway over the marsh where he worked in the 1950's still stands; it is called "Teal's boardwalk" (the cover photo for Marsh Mud and Mummichogs). By carefully measuring how much living Spartina was eaten by grasshoppers and other insects (very little) and the flow of dead cordgrass stems and leaf litter carried out of the marsh by tides (a lot), Teal surmised that decaying Spartina detritus fueled the food web both in the marsh and in the open estuary.
Mass of dead Spartina stems floating down a tidal creek. Although such rafts are impressive, research carried out by Larry Pomeroy, Dick Wiegert, and colleagues has shown that much of the plant matter in tidal creeks originates from algal, rather than cordgrass, production.
This explanation stood until the 1970's, when Larry Pomeroy and a UGA colleague, Dick Wiegert, an ecosystem modeler, carried out an intensive study of primary production and carbon flows in the Sapelo Island salt marshes. They found that algal growth in estuarine water and on sand and mudflats was much greater than expected. They also showed that much of the plant litter washed out of the marsh got carried back into the Spartina plains on the returning tide.
I had a small part in this research. A geochemical tracer technique known as stable carbon isotope analysis allowed me to follow the carbon isotope ratio 'fingerprints' of Spartina and of algal carbon through the marsh and estuarine food webs. The results of my analysis confirmed that most of the animals that lived in the marsh: grasshoppers, periwinkle snails, and fiddler crabs, had the same carbon isotope ratio 'fingerprint' as did Spartina, so they obviously relied on cordgrass, either fresh or decayed, for their food. But, in the open estuary, animal carbon isotope ratios told another story. Their carbon 'fingerprints' were midway between the carbon isotope ratios of Spartina and of algae, so these animals were gaining as much food from algal production as from cordgrass detritus. Even so, Pomeroy and Wiegert's project did underscore the importance of Lanier's 'Marshes of Glenn' as an indispensible nursery and larder for the crabs, shrimp, fish, birds, raccoons, and other wildlife living on the Georgia coast.