Carbonate Beach Sediment Composition at a Tourist Beach, Negril, Jamaica

In the last twenty years, Negril beach in Jamaica has seen more frequent and longer lasting periods of beach erosion. Sediment samples collected in 1980 and 1999 were analyzed and grain size and sediment composition determined. Grain size data indicate that there has been little change in the grain size of sediment along Negril beach between 1980 and 1999. Sediment grains were identified using thin sections and a petrographic microscope. The non-skeletal grains are dominated by amorphous and crystalline grains, while the skeletal grains are characterized by abundant foraminifera with smaller amounts of red algae, bivalves and Halimeda. Grains derived from corals are notably absent from the beach sediment. Comparisons between the 1980 and 1999 datasets suggest that there may have been a small decline in the percentage of foraminifera. The skeletal grains present indicate that the carbonate sediment was produced in the shallow water inner shelf characterized by Thalassia meadows and carbonate sand substrates. Recent development in the Negril area has seen an increase in nutrient influx to the marine system that has resulted in the decline in the coral reefs. A similar decline in the Thalassia meadows with the replacement of Thalassia by fleshy algae due to nutrient influx, coupled with the removal and/or damage of sea grasses by the Tourism industry is probably leading to smaller areas of sea grass cover. This loss in sea grass area will lead to a reduction of carbonate sediment production and consequently the increased likelihood of beach erosion.