Solitary deep-sea coral Desmophyllum dianthus, an example of deep-sea species represented in our estimation of the coral ‘family tree’ based on DNA sequences. Photo credit: Cheryl Morrison, USGS

Reef-building coral Enallopsammia profunda, an example of deep-sea species represented in our estimation of the coral ‘family tree’ based on DNA sequences. Photo credit: Cheryl Morrison, USGS

Solitary deep-sea coral Javania cailleti, an example of deep-sea species represented in our estimation of the coral ‘family tree’ based on DNA sequences. Photo credit: Cheryl Morrison, USGS

Accurate description of biodiversity begins with a classification system that reflects evolutionary history. For hard (scleractinian) corals, skeletal characteristics have traditionally been used to identify and classify species. High species diversity (close to 1,500 species), and a limited understanding of congruence among skeletal characters used for classification, have hindered efforts to reconstruct relationships among species. DNA sequence data provide additional characters for estimating evolutionary relationships. Counter to expectations, molecular phylogenies (‘family trees’ created through comparisons of DNA sequences) have shown that scleractinian corals are divided into two groups called ‘complex’ and ‘robust’ corals that diverged early in their evolutionary history. Species of the family Caryophylliidae, containing Lophelia and many other deep-sea species, also do not form a natural grouping, but are found in both major coral divisions.  We continue to add deep-sea coral species to this framework of relationships that includes Lophelia and other reef-building taxa (e.g., Enallopsammia, Madrepora) as well as solitary corals (e.g., Caryophyllia, Javania). This molecular framework allows for rapid assessment of the evolutionary relationships of new species encountered, species identification of juveniles or larvae, and verification of morphological identifications.

More information on this (Chapter 4, genetics) and related ecological studies can be found in a final report to the Minerals Management Service at http://fl.biology.usgs.gov/coastaleco/OFR_2008-1148_MMS_2008-015/index.html, or contact Cheryl Morrison, Leetown Science Center.

A large Lophelia pertusa coral bush at the North Carolina Lophelia banks with a squat lobster (Eumunida picta) and sea urchin (Echinus tylodes, below the crab). Photo credit: Image courtesy of Ross et al, NOAA-OE, HBOI

Deep-sea coral reefs have received increased public and scientific attention in recent years. Unfortunately, some of the attention stems from the realization that these diverse, fragile ecosystems are being impacted by human activities as deeper waters on continental slopes are exploited for food and energy. In order to effectively protect these habitats, an understanding of where reefs are, the biodiversity present, and the degree of connection between reef areas is needed.  Associations between certain invertebrates and fishes have been documented by a USGS research team in both the Gulf of Mexico and western Atlantic Ocean, suggesting close ecological ties with deep coral habitats. While estimates of genetic connectivity among Lophelia reefs are underway (see Lophelia Connectivity), geographic samples of several Lophelia-associated invertebrates have also been collected, including the squat lobster Eumunida picta, the sea urchin Echinus, a eunicid polychaete worm, plus several fish species (hagfish Eptatretus n. sp., blackbelly rosefish, coral hake, and conger eel).  Genetic data (DNA sequences) will provide an overall estimation of biodiversity and may serve to clarify taxonomic issues, including identification of cryptic species. Comparisons of genetic breaks in connectivity across species, latitudes, and oceans (community or seascape genetics) will provide an integrated perspective on broad patterns of linkages (i.e., connectivity) in deep reef areas and will identify important evolutionary and ecological mechanisms that shape reef communities.

More information about this and related, ecological studies can be found at http://oceanexplorer.noaa.gov/explorations/05coralbanks AND/OR http://www.naturalsciences.org/education/deepsea/index.html, or by contacting Cheryl Morrison, Leetown Science Center.

General information about deep-sea corals can be found at http://www.lophelia.org

Close-up of Lophelia pertusa polyps at Viosca Knoll, Gulf of Mexico. Photo Credit: USGS Deep Water Ecology Group

Lophelia pertusa is the major reef-forming coral along continental margins in the deep sea.  Similar to familiar shallow-water tropical coral reefs, L. pertusa creates structural habitat that is utilized by many fish and invertebrates.  As human activities such as bottom trawling and energy exploration move to deeper waters, L. pertusa reefs are increasingly threatened.

The Johnson-Sea-Link manned submersible (HBOI) was used for sampling L. pertusa reefs. Photo credit: Christina A. Kellogg, USGS

Genetic connectivity is the extent that populations of a species are linked by juvenile or adult exchange.  For corals that are sessile as adults, our ability to forecast how reefs will respond to environmental change requires knowledge of larval dispersal and whether new recruits are likely to come from nearby (low resiliency) versus far away (higher resiliency).  Due to the great depths and rugged bottom topography where L. pertusa reefs occur, these habitats are difficult to observe and sample, thus larval biology of L. pertusa remains poorly understood.  Microsatellite markers are being used to obtain indirect estimates of effective larval dispersal and connectivity.  In partnership with many others, our USGS team has utilized manned submersibles to visit L. pertusa reefs in the Gulf of Mexico and the western North Atlantic Ocean off the southeastern U.S. coast to collect nearly 400 samples for genetic analysis.  Results identify discontinuities, or breaks in connectivity, between ocean basins, suggestive of restricted dispersal, and complex patterns of connectivity within ocean basins.  Results from this work will be important for resource managers in efforts to mitigate impacts of human activities and in the development of efficient management plans.

More information on this and related ecological studies can be found in a final report to the Minerals Management Service at http://fl.biology.usgs.gov/coastaleco/OFR_2008-1148_MMS_2008-015/index.html or by contacting Cheryl Morrison, Leetown Science Center.

Cruise details can be found at http://oceanexplorer.noaa.gov/explorations/05coralbanks and/or http://www.naturalsciences.org/education/deepsea/index.html.

Venus fly-trap anemone (Actinoscyphia saginata), a prominent inhabitant of deep-sea reefs. Photo credit: Open-File Report 2008-1148

The 4-year multidisciplinary research program will focus on understanding the physical oceanography, biology, ecology, genetic connectivity, and trophodynamics of deep coral environments in the Gulf of Mexico (300-1000 m depths), both within natural and artificial (shipwreck) sites. The program has integrated a diverse group of collaborators, including scientists from the U.S. Geological Survey (USGS), University of North Carolina Wilmington (UNC-W), UNC Chapel Hill, National Oceanic and Atmospheric Administration (NOAA), the Royal Netherlands Institute for Sea Research (NIOZ), and the Scottish Association for Marine Science (SAMS). It is part of a larger effort involving the Minerals Management Service (MMS), NOAA Ocean Explorer, and TDI Brooks. We will use a combination of traditional techniques (for example, photography, quantitative sample collections) and several advanced tools (including remotely operated vehicles, multibeam sonar, benthic landers, and genetic analysis) in order to better understand these critical, poorly studied deep-sea habitats.

For more information, view http://fl.biology.usgs.gov/DISCOVRE/index.html, or contact USGS Co-Principal Investigators Amanda W.J. Demopoulos, Florida Integrated Science Center; Christina Kellogg, Florida Integrated Science Center; and Cheryl Morrison, Leetown Science Center.

Media inquiries should contact Gary Brewer.