Multi-partner mapping effort reveals largest known deep-sea coral reef habitat

Covering 6.4 million acres, an area larger than Vermont, an underwater seascape of cold-water coral mounds offshore the southeast United States coast has been deemed the largest deep-sea coral reef habitat discovered to date, according to a paper recently published  in the scientific journal GEOMATICS.

Large cold-water coral mounds were first documented offshore of the southeastern U.S. in the 1960s. Since that time, extensive research has been conducted by regional experts to discover new mounds throughout the Blake Plateau and to document the ecological importance of these habitats. Fisheries managers have used this information to protect known coral areas from physical damage. The recently completed mapping effort in the region builds on this foundational work by revealing the full extent and characteristics of these important deep-sea coral mound features.

For the study, “Mapping and Geomorphic Characterization of the Vast Cold-Water Coral Mounds of the Blake Plateau,” scientists synthesized bathymetric data from 31 multibeam sonar mapping surveys, the largest of which were led by NOAA Ocean Exploration, to produce a nearly complete map of the seafloor of the Blake Plateau, located about 100 miles off the southeast U.S. coastline. The study area is nearly the size of Florida, and stretches approximately from Miami, Florida, to Charleston, South Carolina. The authors used a standardized system developed as part of the study to classify, delineate, and quantify coral mound features. This automated system identified 83,908 individual coral mound peak features in the mapping data, providing the first estimate of the overall number of potential cold-water coral mounds mapped in the region to date. The study documents the massive scale of the coral province, an area composed of nearly continuous coral mound features that span up to 500 kilometers (310 miles) long and 110 kilometers (68 miles) wide, with a core area of high-density mounds up to 254 kilometers (158 miles) long and 42 kilometers (26 miles) wide. The results also highlight how different regions of the Blake Plateau exhibit large variations in the density, height, and pattern of coral mound formation.

Example of seafloor multibeam bathymetry data showing the coral mound features located on the Blake Plateau. Image courtesy of Sowers, et al.

Data analyzed, which included imagery from 23 submersible dives in addition to mapping data, were collected as part of a coordinated, multi-year ocean exploration campaign involving NOAA Ocean Exploration, NOAA Ocean Exploration Cooperative Institute  partners Ocean Exploration Trust  and the University of New Hampshire , the Bureau of Ocean Energy Management, Temple University , and the U.S. Geological Survey, with contributions from Fugro , the NOAA Deep Sea Coral Research and Technology Program, and the South Atlantic Fishery Management Council .

The largest area, nicknamed “Million Mounds” by scientists, is primarily made up of Desmophyllum Pertusum (previously called Lophelia Pertusa), a stony coral most commonly found at depths between 200 – 1,000 meters (656 – 3,280 feet), where waters have an average temperature of 4°C (39°F). Cold-water corals such as these grow in the deep ocean where there is no sunlight and survive by filter-feeding biological particles. While they are known to be important ecosystem engineers, creating structures that provide shelter, food, and nursery habitat to other invertebrates and fish, these corals remain poorly understood.

Studies such as this one provide a better understanding of how populations of corals and other deep-sea species may be related across geographically separated locales (a concept known as connectivity) which in turn can offer insight into the resiliency of these populations. This is important for predicting the impacts of human activities on coral communities and for developing solid plans for their protection.