Research

Restoration Design and Post-Restoration Monitoring Project

Principal Investigator:

Issue

Pouring the mud to create 160 small Reef Balls that will be arrayed in 40 square quads of four each to test various attractant and fill-complexity hypothesisThe United States nuclear submarine MEMPHIS grounded in approximately 10 m of water on a southeastern Florida coral reef off Broward County in February 1993. This grounding caused extensive physical and biological damage to the reef substrate and to the coral community. As part of a mitigation plan, an experimental restoration project was initiated.

Project and Findings

Restoration design mapThis multivariate project compared settlement, growth, and survival rate of corals amongst concrete artificial reefs with and without potential coral attractants. One hundred-sixty small (1.13 m) Reef Balls® were organized into 40, 4-module reef units (quads), each in a square configuration with 3-m sides. Each quad had ReefBalls with one of four attractant treatments: iron, limestone, coral transplants, or plain concrete (control). Each ReefBall had two standardized settlement plates incorporating one of the attractant treatments. The quads were further divided into four treatments of structural complexity by filling the central void space of the ReefBall with differently sized fill (empty, small, mixed, large).

This allowed the determination of the interactive effects of four different fish communities on coral settlement and growth. Different fill complexities generated different fish assemblages. Empty ReefBalls had lower total fish abundance and richness than the three treatments with fill which did not differ from each other. Interestingly, corals were also lower on the outer surface of empty ReefBalls than on those with fill. Corals tended to be higher on limestone- treated settlement plates than other substrate treatments. Porities spp. were the predominant corals recorded followed by Agaricia spp., and Diploria spp.. Montastrea cavernosa and Meandrina meandrites were selected for coral transplantation. All of the M. cavernosa and most of the M. meandrites transplants maintained or increased their tissue surface area. The remaining M. meandrites transplants showed varying degrees of tissue mortality.

Implications for Management

The knowledge required for coral reef restoration is lacking. Currently, "green thumb" or "best guess" approaches are used. The results of this experimental, hypothesis-driven study highlight the interaction of biotic and abiotic ecosystem components and indicate the need for a broad, ecosystem approach to restoration rather than a myopic single-organism approach. The species-specific differences in transplant growth and mortality indicate that species selection must be an important considered in future coral reef restoration efforts. The unanticipated species-specific difference in mortality also indicates the need for an adaptive-management approach to restoration.

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