THE BEACHES:

Nannygoat Beach is the most readily accessible beach on Sapelo and provides and assortment of geological features.

The sand itself has a history. Differing in composition from the Pleistocene sands of the central part of the island, this fine grained, well sorted quartz sand has originated most recently from the landward transport of sand from the shallow continental shelf, primarily transported shorewards by wave energy.

Mud on the beach comes from several sources. Soft, oozing fecal mud is found in the troughs of the runnels. This is derived from the activities of ghost shrimps and tube worms inhabiting the lower beach. Larger mud balls (looking deceptively like small stones) may be found occasionally. These result from the breakup of older Holocene marsh terraces which periodically become exposed on the beaches.

The beach is an area characterized by sand, tides, wind and waves. As it can vary from season to season, day to day, and in a storm or calm weather, so those organisms, which live here, have to grow opportunistically.

The low water mark has its characteristic fauna. This is the area in which to find hermit crabs scurrying about in their borrowed shell and sea pansies lying like purple valentine hearts on the sand surface. In the retreating waves small amphipods – looking and moving like overgrown fleas – are eagerly sought by sandpipers and other shorebirds.

The lower beach provides only indirect clues to many of its other inhabitants. These spend their lives buried below the surface and their burrow entrances or linings are seen much more commonly than are the architects of the burrows. The ghost shrimp (Callianassa) produces a characteristic array of fecal pellets on the sand surface, and when the wave swash has removed the top few centimeters of sand, the thick mud tube entrance to its burrow may be found readily. Onuphis, a tube worm, produces thin parchment-like tubes, composed of chitin covered with fine sand, while another worm Diopatra cements pieces of shell and Spartina debris into its distinctive tube.

Further up the beach, the community is constrained by the shifting nature of the substrate, by the physical effect of currents and wave motion at high water, and by desiccation at low water. Residents tend to burrow into the sand; deposit feeders are found more often in low energy, silty areas while filter feeders appear to prefer sandy high energy areas. This then is an area where the activity appears clandestine. At low tide ghost crabs furtively search the beach debris for an easy meal, and beach hoppers and smaller crabs burrow under stranded horseshoe crabs and Spartina wrack deposited at the high tide line.

In the shallow water in ripple marks and runnels, colored patches may be seen. The colors are brought about by the presence of micro-algae (microscopic one-celled simple plants), euglenoids producing green patches and diatoms producing golden patches. The beach in warmer weather and low light conditions (early morning, late afternoon and overcast weather) shows intense patches of color, especially between low and mid-tide levels. Euglenoids are motile and may be found at greater depths below the sand surface as the intensity of the light increases throughout the day.

One member of the animal kingdom which is often found stranded on the beach among the debris on the high tide line is the plant-like, often brightly colored gorgonian coral. Gorgonians require a solid base on which to grow. A profuse mass of gorgonians can be seen on debris at the bottom of Cabretta Creek at very low tides and it is assumed that this may well be the origin of the majority of the material found on the beach.

Beyond Nannygoat is another Holocene barrier beach know as Cabretta. At its northern end there is an eroded relict Holocene saltmarsh (X) exposed in a series of terraces, representing at least three subenvironments. Oyster clumps reflect earlier tidal creek banks. The presence of mussels indicates short Spartina high marsh. The sandy sediments and Salicornia and Juncus stems represent a different, even higher marsh. This area also provides mute testimony to the massive erosion of more recent beach sands from this northerly aspect.

Another feature of north Cabretta is the presence of washover fans. These are points where beach sand has been driven landward to overlie the modern marsh and are formed by the erosion of the dunes.

Central Cabretta currently has a slough behind the beach foredunes which has varied greatly in character; it has been both open to high tide influence and cut off by a bar to become self-contained. Such a feature may last weeks or years depending on circumstances. This slough has already developed a limited saltmarsh environment of its own.

The ‘big hole’ (Z) area comprises the northern end of Nannygoat Beach and the southern end of Cabretta, which are separated by Cabretta Creek. This is an area of erosion, as can be seen by the large number of uprooted trees and the exposure of old saltmarsh muds as a result of a significant retreat of the shoreline.