Tracking and comparing historical land-use nitrogen inputs to cuban marine environments using stable isotopes from coral cores
The Cuban archipelago has undergone significant changes in land use both after the Cuban revolution of 1959, and after the collapse of the Soviet Union and subsequent era of economic hardship in Cuba known as the “Special Period” of the 1990s. While the Cuban revolution brought about a spatial redistribution of the land and its agricultural areas, the Special Period marked the beginning of the phasing off of synthetic nitrogen fertilizers used in agriculture in favor of organic methods, which predominate today. Coral isotope geochemistry (in particular δ15N) has been used in Pacific reefs to trace past nutrient concentrations and sources in coastal waters using cores from massive corals, since long lived corals can provide quantitative baselines of past seawater isotopic compositions. The δ15N of corals has been shown to exhibit significant variation between corals from sites exposed to agricultural fertilizers versus organic manure fertilizers, as well as nitrogen from sewage runoff. Corals away from such anthropogenic nitrogen sources also exhibit a distinctive isotopic signature.
Using these techniques, CariMar and its collaborators at CIM, aim to reconstruct the effects of land use changes in Cuba during the last 50-60 years using coral cores collected in key habitats which have experienced varying nutrient loadings due to variable runoff from changing land use practices. Coral cores from massive starlet coral (Siderastrea siderea) and Great star coral (Montastrea cavernosa) are being collected along a nearshore-offshore gradient in different habitats in the three gulfs exposed to runoff from agricultural areas, coastal development, sewage effluent, and in non-impacted sites. Such ecological reconstructions provide a historical context for present-day land-based nutrient sources in Cuban coastal waters, permitting new insights into the effects of land management (e.g., the transition to organic agriculture) in Cuban coral reef waters. Cuba’s reefs, because of the country’s adoption of organic agriculture and its effect in water quality, may have benefited from these transitions, which could represent an example for the broader region. This study allows for a unique test and quantification of this hypothesis.
Collaborators:
Dr. Patricia Gonzalez, Centro de Investigaciones Marinas (CIM) de la Universidad de la Habana, Cuba
Orlando Perera Perez, Centro de Investigaciones Marinas (CIM) de la Universidad de la Habana, Cuba
Collaborators:
Dr. Patricia Gonzalez, Centro de Investigaciones Marinas (CIM) de la Universidad de la Habana, Cuba
Orlando Perera Perez, Centro de Investigaciones Marinas (CIM) de la Universidad de la Habana, Cuba
Cover photo by Claudia Legge