The Tropics and Global Climate Change

Stony Brook University, USF researchers and partners publish findings in Proceedings of the National Academy of Sciences.


Researchers deploy equipment in the Cariaco Basin in the Caribbean.         Photo: Courtesy USF College of Marine Science


From USF News


ST. PETERSBURG, Fla. (Oct. 18, 2012) - Reports of declining ice coverage and drowning polar bears in the Arctic illustrate dramatic ecosystem responses to global climate change in Earth’s polar regions. But in a first-ever account of a long-term project in the southern Caribbean, a professor at the University of South Florida working with an international team of researchers has now found  that tropical ecosystems are also affected by global climatic trends and accompanying economic impacts.


In new research published this week in the Proceedings of the National Academy of Sciences, the researchers examined how the complex food web overlying the Cariaco Basin in the southern Caribbean off the coast of Venezuela has changed in a relatively short time frame. Microscopic plankton production has steadily declined and the species of plants supporting the food web have shifted. These ecosystem changes have affected the way this region exchanges carbon dioxide with the atmosphere and contributed to the collapse of the local sardine fishery, having a negative impact on the local economy.


Frank Muller-Karger, a USF College of Marine Science professor in Biological Oceanography and Remote Sensing; worked with Professor Gordon Taylor and colleagues from Stony Brook University’s School of Marine and Atmospheric Sciences, the University of South Carolina and two Venezuelan institutions - EDIMAR, Fundación de la Salle de Ciencias Naturales and Universidad de Oriente - in the analysis of 14 years of continuous monthly oceanographic observations.


The research, known as the CARIACO Ocean Time-Series Program, has been continually funded by the National Science Foundation and Venezuelan science agencies since 1995. Muller-Karger, principal investigator of the CARIACO Ocean Time-Series, conceived the program in 1990 and has worked closely with colleagues in Venezuela and the U.S. to establish an observing platform for precise scientific measurements of the changing climate.


The CARIACO Ocean Time-Series is helping scientists document how changes at the ocean surface are recorded at the bottom of the ocean in accumulated sediments. The Cariaco Basin has one of the finest climate records in the world's oceans, Muller-Karger said.


The analyses of the datasets collected over the last decade and a half now also reveal how these changes affect the economy of the population in the region, for example by impacting the basic sardine fishery.


The sardine is one of the largest fisheries in the Caribbean Sea. It is a local food staple and also represents a major export commodity for coastal communities of Venezuela. Yet, warming temperatures and a change in the plankton, combined with high fishing efforts caused a collapse in the fishery in 2005, from which local communities have not recovered, Muller-Karger said. Several local canneries closed in 2006, and people in many coastal towns of eastern Venezuela lost both jobs and a vital food source.


The CARIACO program is an example of international collaboration which highlights the advances in science that can explain critical changes in environmental conditions that affect social and economic factors. We can only make advances such as this through close work and collegial relationships with researchers in Latin America,” Muller-Karger said.


The researchers linked the ecosystem changes to declining upwelling of nutrient-rich waters caused by weakening trade winds in the region and an average sea surface warming of 1°C during their observations. The researchers reported the changes trace back to the global heat budget, corresponding to climatic shifts in well-known indices of atmospheric circulation.


The study is the first report to link long-term, shipboard time-series oceanographic and local meteorological observations in the Tropics with global scale climatic changes.


The CARIACO Ocean Time-Series Program is currently funded by NSF and Venezuela to continue monthly sampling until the end of 2013 and has a five-year renewal proposal pending.


“We will continue the same measurements which also includes looking at ocean acidification, molecular characterization of microbial communities, and cycling of major elements,” said Taylor, a Marine microbiologist.