Vegetation and Sea-level History of a Mangrove Swamp at Levera Pond, Grenada (2004)

Grenada is a tropical, mountainous island in the Caribbean (12°1'N, 61°4'W).

Levera, a national park on the northeast coast, has a brackish pond (3 m deep, 0.5

km*) and mangrove swamp, sheltered by a beach barrier. Rhizophora fringes the

pond and tidal inlet, followed by an Avicennia zone, mixed mangrove zone, and

Hippomane zone. Surface pollen samples reflect local vegetation, but Rhizophora

and Conocarpus are over-represented, while Avicennia and Laguncularia are under-

represented. Sediment lithology, pollen, and macrofossil analysis indicate that the

mangrove swamp was formerly a bay. Two sediment cores (445 cm long) have a

basal horizon of marine shelly sand, overlain by Rhizophora peat, mixed mangrove

peat, and then clay. A sharp contact between shelly sand and Rhizophora peat

indicates a sudden decrease in energy of deposition. Approximately 2300 years

ago, formation of a beach barrier and accumulation of sediments caused the

mangrove swamp to prograde into the bay. The succession from Rhizophora peat

to mixed mangrove peat indicates a progressive drying of the swamp. In historic

times, forest clearance and agriculture have increased erosion, causing deposition

of clay. Pollen from weeds and Hippomane increase, while Conocarpus declines.

 Area of interest: Grenada 

Year: 1994