About the Sargasso Sea
The Sargasso Sea, some 1,300 kilometers southeast of North Carolina, lies in the middle of the North Atlantic Gyre, a system of clockwise rotating currents that are related to global climate patterns. It covers an area roughly the size of the United States and is uniquely bounded by the surrounding currents, not land. Early explorers were vexed by its stagnant winds and the characteristic mats of floating brown seaweed that hindered their progress.
The large patches of the seaweed Sargassum are floating habitat islands in the otherwise nutrient-deficient conditions of the Sargasso Sea. Over the years, scientists have cataloged an array of life associated with Sargassum, from microscopic bacteria to commercially important fish. Many species are found only with the Sargassum in the Sargasso Sea and have unique adaptations. In the current study, MBARI scientists and collaborators seek to unlock some of the mysteries of this habitat and what it can reveal about the Earth’s changing climate.
The third cruise of Smith and Sherman's Sargasso Sea time series study will depart from Bermuda, traveling southward along a transect through four sampling stations, before docking in the Bahamas.
At each of the four stations, researchers will launch a small, inflatable, outboard boat to sample the Sargassum community both with dip nets and by free-diving. In order to locate patches of Sargassum for sampling, they will use satellite imaging acquired in real-time aboard the ship. Additionally, kites with attached cameras will be launched at each station to survey the surrounding area for Sargassum patches to both support the sampling program and provide ground-truthing for the satellite imaging.
Sargassum communities as indicators of surface ocean warming and increasing acidity
Sargassum is a brown alga found only in the surface waters of the western North Atlantic. These floating patches of algae serve as the basis for entire communities of organisms ranging from bacteria and phytoplankton to attached and free-swimming animals, many of which are unique to this environment.
The Sargassum community was extensively studied in the 1970s and 1980s before the impact of global warming was identified in the surface ocean. MBARI open-ocean ecologist Smith suspects that this sea-surface habitat has been significantly altered by warming surface waters. By observing the Sargassum community and surrounding surface waters, researchers will be able to compare the current state of this environment with records of the same region of the Sargasso Sea taken 25 to 35 years ago. Smith's team successfully sampled this community in February and August 2011, and will now conduct additional sampling in February 2012 to provide a seasonal perspective and complete their field program.
Climate, carbon cycling, and deep-ocean ecosystems
Climate variation affects surface ocean processes, including the production of organic carbon, the primary food supply to deep-sea ecosystems. Recently, studies conducted over the past two decades in the eastern North Pacific and eastern North Atlantic have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean. Data from these two, widely-separated areas of the deep ocean have provided compelling evidence that changes in climate can influence deep-sea processes.
The goal of this project is to establish a deep-sea observatory in the western North Atlantic—an area influenced by the growing intensity of seasonal storm systems—to further study the connection between climate change and deep-sea processes. This deep-sea observatory was initially deployed in February 2011. Data was collected in August 2011, at which time the observatory was redeployed to be recovered in February 2012. The current plan will be to redeploy the observatory in February 2012 for final recovery in August 2012.