ESTABLISHING THE EFFECTS OF SEA SPRAY ACROSS TRINIDAD USING SULFUR ISOTOPES

The island of Trinidad lies only 12 kilometers from Venezuela at its northwestern point. Considered to be the southernmost edge of the Caribbean archipelago, this small island has a unique cultural and environmental history. Yet minimal research considering interactions between humans and the environment has been conducted on the island. Establishing spatial patterns in the sulfur isotope (δ³⁴S) values of vegetation is one way to address this gap. Sulfur isotope values can be used to quantify the variable influence of sea spray across the island. After determining spatial patterns in modern sulfur isotope values, we can use sulfur isotopes in bones from archaeological middens to interpret the degree to which human inhabitants exploited coastal and inland resources in the past. Sulfur isotope values for marine water are typically around 20‰ while terrestrial sources can range from -22‰ to +22‰. Therefore, the incorporation marine sulfur in most terrestrial environments should be very clear. Wind is the primary factor determining how sea spray travels across Trinidad. Since people first populated Trinidad (ca. 8,000 years ago), the climate has been dominated by strong winds from the east. We would, therefore, expect that the influence of sea spray is strongest (and vegetation δ³⁴S values are highest) along the eastern coast of the island.

We present isotopic data for foliage samples that were collected at increasing distances from Trinidad’s windblown east coast to the interior of the island, and on to the calm west coast. Our sample includes the common plant genera Heliconia, Mimosa, Musa, and Cecropia, as well as multiple palms from the Arecaceae family. We find that δ³⁴S values for plants from the east coast resemble marine water. In contrast, δ³⁴S values for interior and west coast plants are dramatically lower. As expected, these data suggest a strong gradient in δ³⁴S values exists with increasing distance from the windward coast. However, we also find substantial isotopic differences among species and among individuals of the same species collected at the same locality. These results will provide a foundation for investigating spatial patterns in the resources used by early inhabitants on Trinidad.