Coral Ecosystem Connectivity 2014

Expedition Purpose

A key purpose of NOAA’s Office of Ocean Exploration and Research is to investigate the more than 95 percent of Earth’s underwater world that until now has remained virtually unknown and unseen. Such exploration may reveal clues to the origin of life on Earth, cures for human diseases, answers on how to achieve sustainable use of resources, links to our maritime history, and information to protect endangered species.

Most people are familiar with shallow water and deep-sea coral ecosystems, but ocean explorers are also focusing on a third type of coral ecosystem: light-dependent deep reefs living in what coral ecologists call the mesophotic zone (or “twilight zone”) in depths of 30 m to over 150 m, depending upon water clarity. Shallow-water coral reefs have been intensively studied by scientists using self-contained underwater breathing (SCUBA) equipment, while deep-sea coral systems are being investigated with human-occupied submersibles and remotely operated underwater vehicles (ROVs). Mesophotic coral ecosystems are beyond the safe range of conventional SCUBA equipment, yet are too shallow to justify the use of expensive submersibles and ROVs; but advances in undersea technologies over the past decade have begun to make investigating these ecosystems possible. While only a few studies of mesophotic reefs have been done using these new capabilities, data from these studies suggest these ecosystems include coral, sponge, and algal species that provide important refuges and nursery habitats for corals and fishes found on shallower reefs.

Pulley Ridge is a mesophotic coral ecosystem off the southwest coast of Florida in 60-80 meters depth, and is the deepest light-dependent coral reef that has been discovered off the United States. Pulley Ridge was originally discovered in 1950, and was found again in 1999 by scientists from the U.S. Geological Survey (USGS) and graduate students from the University of South Florida. Since then, a series of expeditions have revealed that coral ecosystems at Pulley Ridge are considerably healthier compared to the Florida Keys. Scientists hypothesize that Pulley Ridge may play an important role in replenishing key fish species, such as grouper and snapper, and other organisms in downstream reefs of the Florida Keys and Dry Tortugas. Since most of Florida’s reefs have severely declined over the past 30 years, this potential role means it is important to protect and manage Pulley Ridge as a possible source of larvae that can help sustain Florida’s reef ecosystems and the tourism economy that depends on them.

In 2011, NOAA’s National Centers for Coastal Ocean Science’s Center for Sponsored Coastal Ocean Research began a five-year project to investigate the role that the reefs of Pulley Ridge in the Gulf of Mexico may play in replenishing key fish species and other organisms in the downstream reefs. Explore the 2013 expedition at The Coral Ecosystem Connectivity 2014 Expedition is the third year of this interdisciplinary study. Results will be used by resource managers to help manage and protect shallow and mesophotic coral ecosystems. During the 2014 expedition, fieldwork will include: Leg 1: June 18-27, 2014 (R/V Spree).

  • Collecting specimens: On Leg 1 of this expedition (June 2014), divers collected specimens of targeted coral, fish, sponge, and algal species. Scientists will use molecular tools back in their labs to identify relationships among populations at these sites and other reefs in the Gulf of Mexico and the Florida Keys. (For more about technical diving, please see the Expedition Purpose for the Cayman Islands Twilight Zone 2007 Expedition,

Leg 2: August 14-28, 2014 (R/V F.G. Walton Smith)

  • Characterizing the benthic habitat and fish communities at Pulley Ridge and in the Dry Tortugas using the MOHAWK remotely operated vehicle (ROV). Video and photographic surveys will be conducted to quantify and characterize the benthic habitats, fish communities, benthic macrobiota, and coral/sponge cover.
  • Deploying three surface velocity drifters to measure surface currents. Learn more about these drifters at
  • Collecting genetic and other samples from larger fish species using fish traps.Populations of red groupers (Epinephelus morio) and other important fishery species will be sampled using chevron fish traps. Samples for age, growth, and genetics will be taken from each fish, and then the fish will be tagged and released.
  • Characterize planktonic larval fish and invertebrates using an imaging system and light traps. Researchers are interested in the dispersal potential of these various populations, so must pay particular attention to the larval (young) stages, since this stage is often where dispersal occurs – especially for species that remain closely affiliated with (or attached to) the bottom as adults. To achieve this, scientists are sampling the plankton (where the larval stages reside) using an imaging system and light traps – each method serves to capture information about different species. For example, an imaging system (known as the In Situ Ichthyoplankton Imaging System or ISIIS) is used to look at fine scale distribution of larval fishes (and their prey) from the surface to near the bottom whereas, light traps are used to capture the larval fishes as they end their larval stage and ‘settle’ to the bottom as juveniles. These specimens are also used for genetic studies and additional biological analyses (e.g. age and growth) back in the laboratory.
  • Beginning to archive information about Pulley Ridge in a database at Harbor Branch Oceanographic Institute.