PUERTO RICO - Seas at the Millennium
Jack Morelock, Jorge Capella, Jorge R. Garcia, Maritza Barreto
Abstract
Puerto Rico is part of a volcanic island platform that includes Puerto Rico and the Virgin Islands. Puerto Rico's prevailing weather is tropical. The trade winds blow consistently from east-northeast or east in the winter and from east-southeast in the summer. Stronger wind speeds are recorded during summer and winter than in spring and autumn.
The narrow island shelf can be described in terms of north, east, south and west provinces. The north is the narrowest and is marked by higher wave energy and more terrigenous sediments. The east, south and west are carbonate platforms with coral reefs and dominantly carbonate sediments. Each of these provinces has different physical energies.
Marine habitats are being diminished by excessive influxes of sediments and nutrients and by overfishing. During the past 50 years, more than 50 percent of the living coral has been lost and the rate of loss of reef areas has accelerated during the past 20 years. The high population density (>1,000 people per square mile) and a shift of population to coastal areas has had a strong effect.
Although the problems of loss of habitat are generally recognized, very little has been done to protect the environment. Local resources for protection are meager, and Federal (United States) efforts are directed to Florida, Hawaii and the Pacific in terms of coral reef preservation.
Introduction
The Island was born at the leading edge of the Caribbean plate as the Puerto Rico Trench subduction zone developed. Limestones filled in between volcanic flows to form an island 35 by 110 miles. This occurred over the last 65 million years, but the actual shape and size of the Island was essentially completed 40 million years ago. Active volcanism lasted from Cretaceous through Eocene time. The central mountain chain, a core of volcanic material and batholiths, lies south of the centerline, so that the coastal plain is wider on the north than the south, and most of the river drainage is to the north coast.
Figure 1
defines the part of the platform occupied by Puerto Rico and the smaller islands of Vieques and Culebra. The insular shelf is limited in size and drops abruptly to deep water. Variations in the character of the habitat are controlled by wave and current energies, sediment types and sediment influx, and bottom features. The north and northwest insular shelf are a different marine ecosystem from the west, south and east shelves.
Figure 1
defines the part of the platform occupied by Puerto Rico and the smaller islands of Vieques and Culebra. The insular shelf is limited in size and drops abruptly to deep water. Variations in the character of the habitat are controlled by wave and current energies, sediment types and sediment influx, and bottom features. The north and northwest insular shelf are a different marine ecosystem from the west, south and east shelves.