Gray's Reef National Marine Sanctuary
Gray's Reef National Marine Sanctuary
2016 Gray's Reef Research Cruise Photos
Mission Information

Gray's Reef Research
Expeditions 2016


Project Overview

NOAA Ship Nancy Foster

NOAA Ship Nancy Foster
(Photo: NOAA)

Beginning July 7, a research team will conduct SCUBA operations and undertake a variety of research missions to collect information necessary to help make informed management decisions within Gray's Reef. The expedition, underway until July 16th, will utilize two research vessels: The NOAA Ship Nancy Foster and NOAA's SRVx Sand Tiger.

NOAA SRVx Sand Tiger

NOAA SRVx Sand Tiger
(Photo: NOAA)

Divers will examine relationships between large predatory fish and their smaller prey and conduct surveys of fish and invertebrates to examine differences between management zones. Non-diving scientists aboard the NOAA Ship Nancy Foster will use the ship's acoustic instruments to survey for fish at different times during the day and night (the ship operates 24-hours a day while underway). Each project planned for this expedition is described in more detail below.


Gray's Reef National Marine Sanctuary (GRNMS) is located 16 miles offshore of Sapelo Island, Georgia, and protects 22 square miles of rocky carbonate-cemented sandstone reefs. These rocky reefs consist of ledges that can be as tall as six feet and provide shelter for a diverse community of invertebrates, algae, and fishes.

NOAA established a research area in Gray's Reef to increase the opportunity to scientifically discriminate between natural ecological changes within the sanctuary versus changes caused by humans.

Schooling Spadefish with Predators Above

Diver with quadrat
(Photo: Katalin Zakar, ONMS)

One goal of the research area is to determine the effect of bottom fishing on benthic (associated with the ocean bottom) fish populations. This year scientists aboard the NOAA Ship Nancy Foster, will continue the collection of annual data by conducting benthic habitat and fish community surveys at numerous sites located within and outside the research area.

Quadrats are a PVC frame of a known unit of area (such as 0.25 m2) which are used to identify and photograph invertebrate organisms present on the bottom. We will also census the large, colorful, (conspicuous) fishes such as groupers and snappers together with the small, juvenile, and often times subdued-colored (cryptic) fishes such as blennies and wrasses that can serve as important prey for larger fishes. These fish communities will be censused by swimming along a ledge for a known unit of length and width (conspicuous fishes are censused with a 50 m transect that is 10 m wide) and counting, identifying, and estimating the sizes of all fishes seen within the transect.


Schooling spadefish with predators above

Schooling spadefish with predators above
(Photo: Peter Auster, UCONN, Mystic Aquarium)

Reefs, or undercut ledges, in GRNMS are the ecological stage where fish predators and their prey strongly interact. The results of research over the past seven years has shown that predators act in single and mixed species groups to enhance predation success, that predator and prey activity vary over the course of the day and from reef to reef, and that both predator and prey abundance at reefs also vary over space and time. Acoustic surveys to assess fish distribution and abundance at and around reefs from 2011-2013 have demonstrated that overall, prey fish have increased over time. However, direct underwater observations suggest a reverse trend when we only focus on reefs. This suggests that prey fish resources have moved away from reefs as their abundance increased, a density-dependent effect. Further, perhaps predators, at least those large enough to avoid becoming prey for most larger fish, follow the prey fish away from reefs.

This year Dr. Peter Auster and his team will address questions that have emerged from previous observations. That is: how do prey resources at reefs vary over the course of day-night periods and at different tidal stages; do aggregations of prey fish on and off reefs have a characteristic pattern in relation to density and school shape; do predators follow prey away from reefs and interact differently than on reefs? Dr. Auster's team will use acoustic and direct visual survey methods to assess spatial variation in distribution of prey and associated predators both on and off reefs over 24 hour periods to collect fine-scale data to answer these and related questions about the ecology of reef communities. This project is a collaboration between University of Connecticut Department of Marine Sciences, Mystic Aquarium and NOAA's National Centers for Coastal Ocean Science.

Echinoderm Assessment

Sea star and Sea urchin

Sea star and Sea urchin
(Photo: Greg McFall, NOAA)

Dr. Tim Henkel will be assessing the distribution and abundance of echinoderms living on Gray's Reef. This includes sea cucumbers, sea stars and sea urchins. These organisms are prominent members of the benthic community. They are mobile and therefore able to traverse Gray's Reef, though they are slow and therefore easily counted. Most importantly, they can be extremely prolific grazers on algae and predators on sessile invertebrates such as corals, sponges and ascidians. Thus, assessing the populations of these different species is a critical component of understanding the ecology of Gray's Reef.

Invasive Lionfish

Venomous spines adorn the invasive lionfish

Venomous spines adorn the invasive lionfish.
(Photo: FGBNMS)

In recent years, invasive Indo-Pacific lionfish have become a serious threat to Atlantic, Gulf of Mexico, and Caribbean reefs, including waters within Gray's Reef National Marine Sanctuary. Primary reasons for the invasion's success include prolific breeding and an apparent lack of lionfish predators. With their venomous spines, lionfish also represent a safety risk to recreational divers, snorkelers, swimmers and anglers.

In some areas, lionfish may also contribute to the decline of commercially and recreationally important fish and invertebrates, including species caught for local consumption. Tourism is also potentially affected by the reduction in biodiversity, which can lead to declines in popularity of dive destinations. Thus, assessing the scope and status of the lionfish invasion is a high priority for sanctuary managers. During this expedition, scientists will document lionfish observations and remove these invasive species when encountered.

The team will update this webpage with daily logs describing our progress with these planned investigations. Please check back to keep up with our progress!


Nautical Terms



leaving site Indicates a link leaves the web site; Please view our Link Disclaimer for more information | Privacy Policy | Contact Us
Revised by Gray's Reef National Marine Sanctuary Webmaster | User Survey
National Marine Sanctuaries | National Ocean Service | National Oceanic & Atmospheric Administration | U S Dept of Commerce
Web Site Owner: National Ocean Service