Pulley Ridge is the deepest known photosynthetic coral reef in continental U.S. waters.
Pulley Ridge lies in the Gulf of Mexico, 100 miles west of the Dry Tortugas at the far end of the Florida Keys. Pulley Ridge is a submerged 100 km x 5 km barrier island that was originally discovered in 1950. It has less than 10 m of relief across the 5 km wide ridge at depths of 65 to 75 m. According to USGS inn 2005, the coral on Pulley Ridge was “considerably healthier then coral from shallow water reefs nearly worldwide”. This is of particular interest because research shows that shallow water reefs worldwide are stressed due to climate change, habitat loss, human impact, and coral diseases.
Benthic Animals and Algae
Southern Pulley Ridge has an atypical array of photosynthetic hard corals, macroalgae, sponges, and a large variety of tropical fishes. These reefs are termed mesophotic reefs which are relatively deep compared to shallow water reefs. At depths of 50 to about 100 m, mesophotic reefs still receive enough sunlight to support photosynthetic algae and corals with zooxanthellae (algal symbionts). Based on photographs collected by the USGS’s SeaBOSS camera system in 2003, Hine et al. (2008) reported that Pulley Ridge is dominated by coralline algae which covers 45-65% of limestone bottom.
Pulley Ridge is also home to a wide variety of fleshy macroalgae including Halimeda tuna, Dictyota sp., Kallymenia sp., and the endemic species Anadyomene menziesii, which look like large heads of lettuce and can be as dense as tens of plants per square meter. Halley et al. (2013) also reported Agaricia spp. and Helioseris cucullata as the two most abundant species of scleractinian coral which form flat plates as large as 50 cm in diameter and make up almost 60% of the live coral cover in some locations. These species are typically found only on the deeper slopes of shallow water reefs in the Caribbean and Florida. Montastraea cavernosa (the giant star coral) is another species found on Pulley Ridge but is also common on shallow water reefs.
Pulley Ridge is home to more than 80 species of fish including both shallow water and deep reef species. These include the commercially caught species Epinephelus morio – the red grouper. Red grouper form large 8-15 m wide and 1-2 m deep pits in the sand and rubble bottom that provide an oasis-like shelter for numerous smaller reef fish. Unfortunately lionfish are also showing up here recently in virtually every red grouper burrow. Since CIOERT-HBOI discovered the first lionfish on Pulley Ridge in 2010, our research cruises in 2011 and 2012 have shown the population to have exploded.
The second area of study was near the Tortugas Bank
Tortugas Bank is adjacent to but outside of the western boundary of the Florida Keys National Marine Sanctuary (FKNMS) and the North and South Tortugas Ecological Reserves (TER). No benthic surveys have been made previously of these mesophotic reef habitats outside of the protected areas. However, areas within the TERs such as Miller’s Ledge, Riley’s Hump, and Sherwood Forest have been mapped, and are relatively well studied.
It is well known that shallow-water reefs worldwide are increasingly stressed and losing habitat due to climate change, human impact, and coral diseases. However, how well are deep reefs doing in comparison? Deep mesophotic coral ecosystems such as Pulley Ridge are of particular interest and may provide clues to the future of coral reefs.
Questions asked include:
- do mesophotic reefs act as refugia for shallow-water reef species;
- what connectivity, if any, exists between mesophotic and shallow reef species?
Understanding the ecology of mesophotic reefs and the connectivity of the mesophotic and shallow-water reefs may provide a baseline denoting impacts of coral bleaching and other effects of climate change (NOAA 2013). These are some of the questions we hope to answer. These different sub-themes within the grant will produce outputs that are vital to providing managers with knowledge to make informed decisions about the spatial scales of connectivity and functioning of the overall South Florida coral reef ecosystem, and whether specific actions are warranted for the Mesophotic Coral Ecosystem within the area.
We have completed the analysis of data from all of the four cruises. We have identified 216 species of macro-invertebrates and algae. These consist of 102 species of Porifera; 27 Scleractinia; 19 Octocorals; 5 Antipatharia; and various mobile taxa such as crabs, snails, sea stars, and sea urchins, as well as 31 species of algae (green, red, and brown seaweeds).
August 14-28, 2012
The first expedition of the Pulley Ridge- Understanding Coral Ecosystem Connectivity Project involved deployments of:
- ROV Dives
- Drifters (surface current)
- Light Traps (plankton traps)
- MOCNESS (plankton)
- Oceanographic Buoy
- Tech Dives
August 13-29, 2013
The second expedition of the Pulley Ridge- Understanding Coral Ecosystem Connectivity Project. Our 2013 cruise involved a team of 22 scientists and divers working on two ships, the R/V F.G. Walton Smith and the M/V Spree, to accomplish all of our mission objectives.
- Characterized the benthic habitat and fish communities at Pulley Ridge and in the Dry Tortugas using the University of North Carolina’s Super Phantom S2 remotely operated vehicle (ROV).
- Collected genetic and other samples from larger fish species using fish traps.
- Collected samples to characterize planktonic larval fish and invertebrates using plankton nets and light traps. We conducted five MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) tows and seven light trap deployments to collect larval fish and invertebrates.
On the Spree, the nine science divers conducted 85 dives, totaling 22.85 hours of bottom time at depths ranging from 55 to 75 m (180 to 245 ft). Additionally, the divers swapped out the instrumentation at the three Physical Oceanography moorings installed last year at Pulley Ridge and in the Dry Tortugas.
Overall, we had a very successful cruise and were able to accomplish all of our objectives. Plus, this research cruise has gotten us closer towards our ultimate goal – defining what role the reefs of Pulley Ridge may play in replenishment of key fish species, corals, and other organisms in the downstream reefs of the Dry Tortugas and Florida Keys. Our intent is to create a comprehensive understanding of Pulley Ridge to facilitate resource planning in the eastern Gulf of Mexico and allow resource managers to develop more effective strategies to protect these and other reefs.
Read More about the 2013 cruise…
August 14-28, 2014
The third expedition of the Pulley Ridge- Understanding Coral Ecosystem Connectivity Project, is focused on investigating the role that the relatively healthy deep, mesophotic reefs of Pulley Ridge (off the southwest coast of Florida) may play in replenishing key fish species, such as grouper and snapper, and other organisms in the downstream reefs of the Florida Keys and Dry Tortugas. Because of the well-documented decline of Florida’s reefs, it is important to identify, protect, and manage sources of larval reef species that can help sustain Florida’s reef ecosystems and the tourism economy that depends on it.
Read more about the 2014 cruise…
August 22-September 4, 2015
We successfully concluded our fourth and final field season to investigate the role that the mesophotic coral ecosystems of Pulley Ridge (off the southwest coast of Florida) may play in replenishing key fish species, such as grouper and snapper, and other organisms in the downstream reefs of the Florida Keys and Dry Tortugas. Our team of 16 scientists and divers working on two ships, the R/V F.G. Walton Smith and the M/V Spree, accomplished all planned objectives for the 2015 field season. The data collected during this summer will be analyzed, along with the data collected from our 2012-2014 field seasons, to determine the connectivity of reef species living in Pulley Ridge to those of the Florida Keys and describe the structure of Pulley Ridge’s mesophotic communities. The results will then be provided to resource managers to enable development of more effective strategies to protect mesophotic reefs
Read more about the 2015 cruise…
This project is a unique collaboration of more than thirty scientists pooling the expertise from within two NOAA CI’s: the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) at the University of Miami (UM), and the Cooperative Institute for Ocean Exploration Research and Technology (CIOERT) at Harbor Branch Oceanographic Institute/Florida Atlantic University (HBOI-FAU), as well as the wider Gulf of Mexico scientific and management communities. This research was a collaboration of University of Miami (Drs. Robert Cowen, Peter Ortner), CIOERT-HBOI (Dr. Shirley Pomponi, Dr. Dennis Hanisak, John Reed, Dr. Joshua Voss), NOAA Fisheries (Andy David, Stacey Harter, Heather Moe), Florida State University Coastal and Marine Laboratory (Drs. Felicia Coleman and Chris Koenig), the University of North Carolina at Wilmington (Lance Horn, Jason White), the Florida Keys National Marine Sanctuary, and the Gulf of Mexico Fishery Management Council. We thank CIOERT for continued support of the mesophotic reef research program at HBOI-FAU. The crew of
University of Miami’s ship R/V F.G. Walton Smith provided excellent support for the four cruises. ROV pilots Lance Horn and Jason White, University of North Carolina at Wilmington (UNCW-CIOERT) Undersea Vehicle Program, are especially thanked for their support and effort which made these ROV dives a success. UNCW provided the Super Phantom 2 ROV in 2012 and 2013 and the U.S. National Marine Sanctuary Foundation provided the Mohawk ROV in 2014 and 2015. The cruises, ROV dives, and benthic analyses were led by CIOERT-HBOI.
NOAA’s National Marine Fisheries Service/Southeast Fisheries Science Center (NMFS/SEFSC), Panama City Laboratory, provided at-sea support and video analysis of fishes. This research was funded by the NOAA National Centers for Coastal Ocean Science under award NA11NOS4780045 (Project Title: “Understanding Coral Ecosystem Connectivity in the Gulf of Mexico – Pulley Ridge to the Florida Keys”) to CIMAS at UM, and the NOAA Office of Ocean Exploration and Research under awards NA09OAR4320073 and NA14OAR4320260 to CIOERT at HBOI-FAU. This is Harbor Branch Oceanographic Institute Technical Report Number 178.