Construction of the Panama Canal brought the Smithsonian Tropical Research Institute (STRI) to Panama a century ago, placing it in the midst of a remarkable three million-year-old natural experiment in evolution and ecology. The Isthmus of Panama connects two continents and divides two very different oceans. Only 80 km apart, each has dramatically different coral reefs systems and near-shore marine environments. The Tropical Eastern Pacific (TEP) supports a great diversity and abundance of marine life due to upwelling, which makes it cooler and richer in nutrients than most tropical waters. The warmer, high-salinity Tropical Western Atlantic (TWA) hosts a suitable environment for abundant coral, but with episodic warming events causing bleaching of certain coral species. The presence of two oceans so close together provides a unique comparative framework for the study of coral reefs ecosystems and how they respond differently to environmental change.
The physical and nutrient drivers of primary and secondary production at Bocas del Toro in the TWA and the Gulf of Chiriqui in the TEP are dramatically different due to their position on either side of the Isthmus of Panama making them ideal sites for a comparative study using marine observatories. Both locations are subject to the annual movement of the Inter-Tropical Convergence Zone (ITCZ) causing intense seasonality. These volatile climatological conditions result in extreme temporal and spatial gradients in light penetration, temperature, salinity, nutrients, dissolved oxygen, primary and secondary production, geochemical processes, and benthic and pelagic community structure. The presence of sustained observational capabilities at both sites is allowing simultaneous, real-time measurements of key variables comparatively across the Isthmus and address critical questions regarding climate change, ocean acidification and their impacts on diversity.
During the dry season in the Gulf of Chiriqui, upwelling of cold, nutrient rich, and hypoxic water, coupled with strong vertical mixing by internal tides, and internal waves create eutrophic conditions leading to algal blooms and intense secondary and tertiary production that is reasonably homogenously distributed throughout the Gulf. Conversely, at the Bocas del Toro site, weak nutrient injections from local runoff, onshore transport of oceanic water, and weak vertical mixing lead to oligotrophic conditions and strong offshore/onshore gradients in fish diversity and sensitivity of coral to changing environmental conditions. These multi-scale physical forcing functions and potential sources of physiological stress differentially contribute to shaping the biological productivity in plankton, and the distribution of coral and fish communities observed across the Isthmus. Because of its dynamism, a comparison between the Caribbean and the Tropical Eastern Pacific is becoming the worlds natural laboratory for understanding and forecasting the two major marine climate change impacts: increased environmental volatility and ocean acidification in the presence and absence of coastal upwelling.
The Cross-Isthmus OceanCube Observatory System is providing data for the investigation of the tropical ocean-atmosphere-climate system in response to sea level rise and increasing CO2 concentrations (decrease in seawater pH, alkalinity, and carbonate saturation state), as well as its effect on marine communities and their associated feed-back mechanisms. Near-real-time telemetry and adaptive sampling of episodic events (e.g., red tide), which may dominate local and regional processes, on scales of seconds to years will provide the baseline for how the ecosystem is changing in response to anthropogenic (e.g., deforestation, altered atmospheric and ocean chemistry) and natural processes.