University of North Carolina at Wilmington National Oceanic and Atmospheric Administration NURC's AUVs

Mapping the Oculina Bank Deep Coral Marine Protected Areas with New Undersea Technologies

Situation and Need

Figure 1: Oculina Bank off east coast of Florida in 80-120 m of water from Fort Pierce to Cape Canaveral; OHAPC and OECA noted. West boundary of OECA is 80W longitude. East boundary of OHAPC is 100 fm isobath (183 m). North boundary of OHAPC is 28-30N and south boundary is 27-30N.

Figure 1: Oculina Bank off east coast of Florida in 80-120 m of water from Fort Pierce to Cape Canaveral; OHAPC and OECA noted. West boundary of OECA is 80W longitude. East boundary of OHAPC is 100 fm isobath (183 m). North boundary of OHAPC is 28-30N and south boundary is 27-30N.

The Oculina Bank Habitat Area of Particular Concern (OHAPC) and the Oculina Experimental Closed Area (OECA) are marine protected areas (MPAs) designed to conserve deep coral habitat and fisheries in 70-110 meters of water off the east coast of Florida (Figure 1). Over the past thousand or more years, the ivory tree coral, Oculina varicosa, has built up coral mounds or bioherms, on limestone bedrock at the shelf edge; 100 km of these pinnacles, mounds, and ridges (5-35 m above bottom) from Fort Pierce to Cape Canaveral is the area covered by the Oculina Habitat Area of Particular Concern (OHAPC) (Figure 1). The mounds are overlain with living or dead coral, coral rubble, sand, or mud (Figure 2). Biodiversity of intact living Oculina colonies (thickets or heads) is similar to shallow tropical coral reefs and much greater than unconsolidated substrate (rubble, sand, shell, mud). Healthy, intact Oculina habitat also supports dense and diverse populations of fishes. Bank mounds are known breeding grounds for commercially exploited populations of gag and scamp grouper, nursery grounds for juvenile snowy grouper and speckled hind, and feeding grounds for many reef and pelagic fish species. Unfortunately, rock shrimp trawling and scallop dredging over the past three decades has destroyed most of the intact coral mounds on the Bank.

Fisheries in federal waters off Florida are managed by the South Atlantic Fishery Management Council (SAFMC). The Magnuson-Stevens Act mandates the Council to identify essential fish habitat (EFH) and adverse impacts on EFH from fishing and non-fishing activities, in all their Fishery Management Plans. Habitat Areas of Particular Concern (HAPC) are EFH especially critical for fish reproduction and growth to maturity. The Oculina HAPC was the first coral HAPC in federal waters (first established in 1984 and expanded in 2000). The Oculina Experimental Closed Area (OECA, southern portion of OHAPC, Figure 1) was closed to harvest or possession of snapper/grouper species in 1994, and was the first reef-fish Marine Protected Area in federal waters in the nation. Amendment 13A to the Snapper/Grouper Fishery Management Plan requires review of the OECA boundaries in 2007, and review of the research, outreach and law enforcement efforts supporting the OECA by 2014. Accurate maps are a top priority as identified in the draft OECA assessment, research and monitoring plan (download PDF).

Figure 2: Left — Healthy Oculina coral bank at 80 m depth photographed by JSL submersible in 1984; Right — Formerly healthy Oculina mound covered in coral rubble in 2001.

Figure 2: Left — Healthy Oculina coral bank at 80 m depth photographed by JSL submersible in 1984; Right — Formerly healthy Oculina mound covered in coral rubble in 2001.

2006 AUV Survey Objectives

Figure 3: OHAPC, OECA, previous MBS survey geotifs, and 2005 ROV Dive Sites; this cruise will survey reef balls (red box) and unsurveyed portions of the OECA (blue box).

Figure 3: OHAPC, OECA, previous MBS survey geotifs, and 2005 ROV Dive Sites; this cruise will survey reef balls (red box) and unsurveyed portions of the OECA (blue box).

The OHAPC is rugged and deep (beyond normal scuba diving depths) and swept by the Gulf Stream west wall and its associated dynamics. Habitat mapping and reef fish assessment is ineffective using standard trawls and towed sonar equipment. Habitat maps include biotic (e.g., sessile epifauna) and abiotic (e.g., sand, rock, wreck) structure. Acoustic sonar mapping using multi-beam sonar systems (MBS) provides high resolution bathymetry (depth) and bottom hardness (backscatter or reflectance). However, as water deepens, resolution goes down due to signal attenuation or lower frequency of the sonar required to see the bottom. Even at best resolutions, acoustic data must be ground-truthed, visually or using bottom samples, in order to assess biota; flat rock bottom is less interesting to fish than a “live-bottom” covered in corals, hydroids, sponges or macro-algae. The only way to get higher resolution (greater than 1-2 m) below 100 m depth is to put the sonar closer to the bottom. As towed systems are less accurately positioned and controlled with respect to beam angles (pitch, heave, yaw), especially in high currents, the best solution is to put the MBS on an Autonomous Underwater Vehicle (AUV).

In 2002 and 2005, ship-board MBS surveys covered the majority of Oculina habitat in the OHAPC (Figure 3). In 2003 and 2005, ROV dives throughout the OHAPC (at sites inside and outside) provided video and still images in various habitat types. Results will be integrated in a Geographic Information System. As a result of the limitations of ship-board mapping, both the 2002 and 2005 surveys were cut off above 100 m depth, or roughly longitude 79-57.5W in the OECA (Figure 3). The 2006 survey will accomplish the following major objectives using the NURP Eagle Ray AUV as MBS platform (Figure 4):

Technologies

An Autonomous Undersea Vehicle (AUV) and remotely operated vehicle (ROV) will be deployed from the M/V Liberty Star or its sister ship Freedom Star, owned by NASA and operated by the United Space Alliance out Cape Canaveral, FL. These ships are ideally suited for these operations due to their proximity to the survey area, and technical support capabilities (e.g., expert crew, dynamic positioning, ability to deploy AUV and ROV). NURC’s Phantom SII (Figure 4), 300 m max depth, color video camera and digital still camera; tethered to ship by umbilical; USA ships are particularly good (Dynamic Positioning is ideal) and proven for difficult operations on the Bank); major tasks will be to serve as rescue asset for the AUV if required, and to ground-truth acoustic survey done by AUV. NURC’s Eagle Ray AUV (Figure 4), 2200 m max depth, 5 meters long, 920 kg in air; major payload is a 300 kHz multi-beam echosounder which produces a high-resolution (less than 1m pixel) bathymetric and backscatter (seafloor reflectance) map. We will overcome the resolution limitations of deep water, ship-board MBES surveys by putting the system closer to the bottom on the Eagle Ray AUV.

Figure 4: Major equipment to be used on 2006 cruise: Left — Phantom SII ROV on deck of Liberty Star; Right — Eagle Ray 2200 m AUV with multibeam echosounder (details at http://www.uncw.edu/nurc/auv/explorer/).

Figure 4: Major equipment to be used on 2006 cruise: Left — Phantom SII ROV on deck of Liberty Star; Right — Eagle Ray 2200 m AUV with multibeam echosounder.

Expected Outcomes

Expected benefits of this project include:

Deliverables for the proposed activity, including but not limited to all GIS layers, map products, photography, metadata, will be disseminated to a wide audience through the Council’s Habitat and Ecosystem Homepage, which includes a Habitat and Ecosystem Internet Mapping System