Post-colonial pollution of the Bay of Cartagena, Colombia

The city of Cartagena, Colombia, was founded in 1533, making it the fifth oldest, continuously inhabitated colonial city in South America. Today, Cartagena is the fifth largest city in Colombia, with ~ 1.2 million inhabitants. Las Quintas Lagoon lies near the center of Cartagena and is connected hydrologically to the Bay of Cartagena and Las Virgenes Lagoon via channels. The sediments of Las Quintas Lagoon thus offer a unique opportunity to explore the environmental history of one of the oldest cities in South America. We analysed a 210Pb- and 14C-dated sediment core from Las Quintas Lagoon to investigate the environmental effects of long-term urban development in this tropical, estuarine setting. The sediment core from Las Quintas Lagoon displays evidence of change in the depositional environment during the last few centuries. Principal Component Analysis indicated relatively stable conditions in Las Quintas Lagoon from the begining of the record (about 1300 CE) until ca. 1900 CE, when the ongoing eutrophication began. PC1 shows statistical significance and was dominated by geochemical indicators, whereas PC2 correlated with pollen spectra. Upcore decreases in TOC/TN values, together with increases in TOC, TN and δ15N values, indicate greater autochthonous (i.e. phytoplankton) production and eutrophication. Lack of statistical significance of PC2 points to low variability among pollen spectra, and hence vegetation, through time. Diatom assemblages in the Las Quintas Lagoon sediment record display two shifts during the last 100 years, ca. 1940 and 2000, which also reflect progressive eutrophication of the system.