Wildlife Health
Gray's Reef

sponges, corals and other invertebrates
Sponges, corals, and other invertebrates are important in structuring benthic habitat. Credit: Greg McFall, NOAA

Why is it a concern?

There are several genera and species that provide vital ecosystem functions and services within the fish and benthic communities of Gray’s Reef National Marine Sanctuary. These key groups and species include groupers, snappers, sponges, and tunicates.  On a regional scale, stock assessments show that populations of certain predatory fish are increasing: gag, scamp, black sea bass, king mackerel, and red snapper, although there was no data collected from within the sanctuary to support these trends. Information on contaminant levels in fish tissue for species within the sanctuary are limited to black sea bass samples collected in 2003, and these were found to be below human-health guidelines.  Much more data is needed to accurately assess conditions of important fish in the sanctuary.

Benthic cover of invertebrates on live-bottom areas is integral to the essential habitat provided within the sanctuary and is dominated by various species of sponges, corals, tunicates, arborescent bryozoans, bushy hydrozoans, and gorgonians. Fluctuations in percent cover of these species are caused primarily by storm impacts or natural seasonal cycles. Sponges, recognized as important in structuring habitat, have been found to contain organic contaminants (PCBs, PAHs etc.) in their tissues. These filtering organisms appear to be accumulating contaminants from the water column. No evidence of disease has been observed in these key benthic species to date, but more current and comprehensive sampling is needed.

Current monitoring efforts provide status and trends of the marine resources of the sanctuary, but more research is needed to identify potential stressors as human use of the sanctuary and surrounding areas increases, and the climate changes.  Researchers have the unique opportunity to assess the impacts of fishing on benthic and fish community health because one-third of the sanctuary is a Research Area (RA)—closed to recreational fishing and diving as well as anchoring of any kind.  The RA also allows scientists to document effects of climate change in the southeast on the stability of limestone reefs in the absence of fishing.

Overview of Research

Project Name PI and contacts Links

Recruitment and succession of sessile benthic invertebrates in the South Atlantic Blight

Dr. Danny Gleason


Influence of benthic features and fishing pressure on size and distribution of three exploited reef fishes from the Southeastern United States

Matt Kendall


Sponge and Octocoral Epifauna at Gray’s Reef National Marine Sanctuary

Anna Greene, Jeff Hyland


Benthic Macroinfaunal Communities and Levels of Chemical Contaminants in Sediments and Biota at Gray's Reef National Marine Sanctuary and Nearby Shelf Waters off the Coast of Georgia

Cynthia Cooksey, Jeff Hyland, Len Balthis



Science Needs and Questions

  • What role does the Research Area play in long-term changes in predator fish species populations?
  • What factors affect the population dynamics of key sponge and tunicate species?
  • What biotic and abiotic factors affect coral recruitment success of coral species in the Sanctuary?
  • Are there contaminants present in fish at GRNMS?

Education and Outreach Material

Gray’s Reef National Marine Sanctuary Education webpage


Cooksey, C.J. Hyland, W.L. Balthis, M. Fulton, G. Scott, D. Bearden. 2004. Soft-bottom benthic assemblages and levels of contaminants in sediments and biota at Gray’s Reef National Marine Sanctuary and nearby shelf waters off the coast of Georgia (2000 and 2001). NOAA Tech. Memo. NOS NCCOS 6. NOAA National Ocean Service, National Center for Coastal Environmental Health and Biomolecular Research, Charleston, SC. 55pp.

Freeman, C.J., D.F. Gleason, R. Ruzicka, R.W.M. van Soest, A.W. Harvey, G.B. McFall. 2007. A biogeographic comparison of sponge fauna from Gray’s Reef National Marine Sanctuary and other hard-bottom reefs of coastal Georgia, U.S.A. In: Porifera Research: Biodiversity, In-novation, and Sustainability, M.R. Custodio, G. Lobo-Hajdu, E. Hajdu, G. Muricy (eds.), Rio de Janeiro, Museu Nacional. pp. 319-325.

Gleason, D.F., A.W. Harvey, S.P. Vives. 2007. A guide to the benthic invertebrates and cryptic fishes of Gray’s Reef. Georgia Southern University. http://www.bio.georgiasouthern.edu/gr-inverts/index.html

Harris, P.J., G.R. Sedberry, H.S. Meister, D.M. Wyanski. 2005. A summary of monitoring and tagging work by the Marine Resources Monitoring and Assessment Program at Gray’s Reef National Marine Sanctuary during 2005. Report submitted to Gray’s Reef National Marine Sanctuary by Marine Resources Research Institute, South Carolina Department of Natural Resources, Charleston. 10pp.

Hyland, J., C. Cooksey, W.L. Balthis, M. Fulton, D. Bearden, G. McFall, M. Kendall. 2006. The soft-bottom macrobenthos of Gray’s Reef National Marine Sanctuary and nearby shelf waters off the coast of Georgia, USA. J. Exper. Mar. Biol. Ecol. 330:307-326.

Kendall, M.S., L.J. Bauer, C.F.G. Jeffrey. 2007. Characterization of the benthos, marine debris and bottom fish at Gray’s Reef National Marine Sanctuary. Prepared by National Centers for Coastal Ocean Science (NCCOS) Biogeography Team in cooperation with the National Marine Sanctuary Program. Silver Spring, MD. NOAA Technical Memorandum NOS NCCOS 50. 82 pp. + Appendices.

Wyanski, D.M., M.J.M. Reichert, S.M. Pate. 2012. A summary of reef fish monitoring by the Marine Resources Monitoring and Assessment Program at Gray’s Reef National Marine Sanctuary during 2011. MARMAP Technical Report #2012-019.