Sapelo Island Flyover: Video Transcript and Glossary

Video Transcript

0:28 – This is the Cabretta Island relict marsh, which crops out along the sandy shoreline of Cabretta Beach. Near it are a tidal channel, salt marshes, tidal creeks, and maritime forests.

0:39 – Here is the southeastern end of Sapelo Island along Nannygoat Beach, with shallow offshore, beach, coastal dune ridges, back-dune meadows, and maritime forest.

0:51 – This salt marsh has patchy areas with no vegetation, called “salt pans,” and marshes are cut by meandering tidal creeks connecting to a coastal inlet on Nannygoat Beach.

1:02 – In this view you can see abrupt transitions between a salt marsh, maritime forest, and artificial freshwater pond, which is in the foreground.

1:11 – A time-lapse of a rising tide on Cabretta Beach over the course of about five hours provides an example of tide-dominated processes on the Georgia coast.

1:22 – This is an overhead view of the University of Georgia (Athens) Marine Institute (UGAMI) and an adjacent tidal creek and salt marsh at high tide.

1:30 – The consequences of a “king tide” on the salt marshes, tidal creeks, and human-built structures on the south end of Sapelo Island include flooding of a road at high tide.

1:40 – Part of the same salt marsh at low tide reveals complex dendritic drainage patterns in tidal creeks, with a road, telephone wires, and power lines as human influences on these environments.

1:53 – This is Cabretta Beach, with dead trees on the shoreline as evidence of the shore encroaching on and succeeding a maritime forest, modeling the effects of future sea-level rises.

2:05 – Here is the salt marsh behind Cabretta Beach, with storm-washover fans of sand showing how the beach is moving laterally across the salt marsh.

2:13 – This is part of a time-lapse of marsh periwinkles (Littorina irrorata) grazing on smooth cordgrass (Spartina alterniflora) following a high tide.

2:21 – Cabretta Beach has a prominent sandbar and runnel system caused by the movement of sand supplied by an ebb-tidal delta, and it is next to back-dune meadows with human-made trails.

2:34 – The Cabretta Beach relict marsh here is next to storm-washover fans, which are covering former salt-marsh environments. Also note new-growth smooth cordgrass on the relict marsh.

2:46 – The transitions of Nannygoat Beach include offshore sands, beach, coastal dunes, back-dune meadows, and maritime forests, with dune ridges showing places of sand accretion.

2:58 – The Sapelo Island Lighthouse is an example of a human landmark connecting the island with past shipping of agricultural goods and slavery on the Georgia coast.

3:10 – Here is a well-developed sandbar and runnel system on the southeastern end of Sapelo, representing sand accretion from longshore drift. Curved breaks in the back-dune-meadow vegetation indicate previous shorelines. Notice also how shorebirds use such sandbars as resting places before flying away.

Glossary of Terms

Back-dune meadow – Vegetated area behind the dunes along a shoreline, often formed by previous dunes left behind as a shoreline shifted seaward and plants colonized it.

Coastal inlet – Narrow zone dissecting a beach that connects the open ocean with areas behind the beach, allowing tidal waters to move in and out.

Cordgrass (Spartina alterniflora) – Grass species that dominates lower parts of Georgia coastal salt marshes, also called “smooth cordgrass” or simply “Spartina.”

Ebb-tidal delta – Delta-shaped deposit of sediment formed on the seaward side of a coastal inlet as a result of strong ebb tides.

“King tide” – Informal term used to describe the highest tides that might occur during a given year, when the earth, moon, and sun align; such tides can be accentuated by local weather conditions.

Longshore drift – Lateral movement of sand along a shoreline by waves, causing a transport of sand from one part of a beach to another.

Maritime forest – Ecosystem proximal to shorelines, usually dominated by live oaks (Quercus virginiana), saw palmettos (Serenoa repens), pines (Pinus spp.), and other plants tolerant of seaside conditions.

Offshore sands – Sandy environments below the intertidal zone that normally remain submerged.

Periwinkle (Littorina irrorata) – Species of gastropod (snail) that lives in salt marshes, grazes on algae and fungi on smooth cordgrass; also called “marsh periwinkle.”

Relict marsh – Compacted remnant of former salt marsh that is typically buried and later exhumed along a shoreline, retaining old clams, oysters, fiddler crab burrows, and roots of smooth cordgrass.

Runnel system – Channel-like low area on a beach between coastal dunes and the shoreline, and often parallel to the shoreline, that is filled by flood tides and eroded by ebb tides.

Salt marsh – On the Georgia coast, an ecosystem dominated by tidal processes, mud, salt-tolerant plants, and animals adapted to daily tidal fluxes.

Salt pan – Relatively higher area on a salt marsh that experiences less tidal influx, and hence has higher evaporation rates that concentrate salt in its soils, excluding most plants.

Sand accretion – Net accumulation of sand in an area, whether through longshore drift, wind transport, or storm waves; can result in a shoreline “migrating” seaward.

Sandbar – Deposit of sand in offshore direction that is either shallowly submerged ore emergent during low tide.

Storm-washover fan – Fan-like deposit of sand and/or debris formed by storm waves, often covering adjacent environments (e.g., salt marshes)

Tidal channel – Meandering incision in a salt marsh carved by flood and ebb tides, resembling a mainland river.

Tidal creek – Smaller-diameter incisions in a salt marsh representing “tributaries” of a tidal channel, representing higher reaches of a flood tide; often form dendritic patterns.

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