Nicole Williamson
The role of artificial reef systems as sustainable habitats
BSES Senior Research Project 2007

Abstract

The objective of the study was to examine the different coral cover patterns, growth, and recruitment in artificial reef systems. With constant stress on natural reef systems, alternative sites must be sought out and used for alternative ways to sustain these living reefs. Two 1733 shipwrecks were examined in the Summer of 2007, led by Professor Charles Beeker, using underwater documentation of video and photographs, scale bars, underwater mapping and measuring techniques. A total of 7 logged dives on the sites, with two teams of four made a biological inventory of specific coral heads to the equivalent of 60 hours of underwater research. The San Pedro located 1.25 nautical miles south of Indian Key in 20 feet of water acts as a shallow patch reef system. The site had been disturbed much through the 20th century until it became on the national registrar of historic places in the late 1980’s.

Figure 1. Hard at work on the San Felipe (undisturbed)

The site is composed of approximately 65 ft by 40 ft of loose ballast stones of the remains of the ship, acting as a loose substrate for coral recruitment approximate 6-.9 meters high. The sister ship, the San Felipe, which also sunk in the 1733 hurricane, is located one mile offshore of Lower Matecumbe Key in 18 ft of water. Unlike the other heavily salvaged shipwrecks the San Felipe was left relatively undisturbed allowing the ballast stone to form a conglomerated matrix. The 54 ft long ballast pile offers the corals recruited here 2 meters of relief from the seabed in a slightly heavier sedimentation channel. Both sites support an over 250 year old, artificial, in shore patch reef community.

The results showed overall different community composition and density of each site. Results showed equal ability for each sites recruit and sustain massive and non-massive coral heads. The community species structure differed at each site, Colpohyllia natans dominating in the disturbed site and Siderastrea siderea in the disturbed. These differences can be attributed to each species response to different stress situations. The high percentage (70%) of massive corals at both sites indicates their ability to out compete their non-massive counterparts with a long life history strategy. The findings on each reef present potential patterns of recruitment, growth, and coral composition for artificial reefs with varying stress factors.