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Paleohydrology record of the stromatolites of the Bacalar Lagoon: new insight for climate change assessment in the Mexican Caribbean

IWRA World Water Congress 2017 - Cancun Mexico
5. Water ecosystems and physical regimes
Author(s): Nidia Tobon
Nidia Tobon
Centro de Investigación Cientí­fica de Yucatán
nidia.tobon@cicy.mx


Keyword(s): stromatolites, paleohydrology, Bacalar, protection, climate change
Article: Oral:

Abstract

The stromatolites are organosedimentary carbonate deposits formed from the interaction between benthic microbial communities and detrital sediments. These structures are unique in the Bacalar lagoon because they are one of the largest freshwater microbialite occurrences in the world. The Bacalar lagoon is facing to antrophogenic activities increasing like wastewater non treated, use of pesticides, etc. The Bacalar town becomes a municipality 3 years ago, and the plans for urban development, and tourism (infrastructure and activities) investments are causing a pressure over these ancient structures and over the symbolic lagoon (called “Seven colors Lagoon”). Besides, the tourist activities in the lake also disturb the water characteristics.

The carbonate structures(stromatolites) are present worldwide and in the Bacalar lagoon are particularly important, because they preserve past information about the climatic and life conditions in the moment of their sedimentation. The analysis of sedimentary record of these structures permit to realize a paleohydrology reconstruction indicated how the Bacalar lagoon have changed through the time, in terms of the chemical composition, changes in temperature and precipitation (climate change), and due to the groundwater contribution and other factors.

Through this investigation it could be seen the changes in the composition and dynamic of the lagoon, and the results can let us to make some projections (climatic, recharge and anthropogenic).

For the study, six cores of the stromatolites were collected in the west part of the lagoon. Also, sediment and water samples were collected in order to assess the quality in the influence area of the collected cores. To establish the chronology of the lacustrine sequence, the cores were dated through AMS 14C at the University of California Santa Cruz. Furthermore, the stable isotopes as 18O and 13C were analyzed. Additionally, it was determined the concentration of trace elements and the rare earth elements (REE). To water characterization, the pH, temperature, dissolved oxygen, conductivity, alkalinity, nutrients, major and trace elements concentration were determined in the collected samples. With the analysis we can infer the factors of regulation and behavior patters.

The Bacalar lagoon does not have a regulation like protected area, and the management plan is been developed. The tourism and economic activities are impacting the ecosystem. The Bacalar Lagoon ecosystems need a protection, governance and policies in adaptation/resilience programs facing to climate change. To define policies based on scientific research, using ancient structures like stromatolites as proxies, to explain the past and to help us to answer the present challenges, and to visualize the future transformations, it is fundamental in order to make decisions and take action about the management of the coastal lagoon in the Mexican Caribbean.

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