Tools to Assess Recovery Status and Convergence Rates Between Restored and Undisturbed Coral Reef Habitats

Lirman, Diego; Miller, Margaret

Boating activities are an increasing source of physical damage to coral reefs worldwide. The damage caused by ship groundings can be significant and may result in a shift in reef structure and function. In this study, we evaluate the status of two restoration projects established in 1995, six years after two freighters, the M/V Maitland and the M/V Elpis, run aground on reefs of the Florida Keys National Marine Sanctuary. Our approach includes field monitoring in support of simulation model development to assess the effectiveness of the restoration efforts. A population model was developed for the coral Porites astreoides to predict the convergence rates of coral abundance and population size structure between the restored and surrounding reference habitats. The coral communities on the restoration structures are rapidly approaching the structure of reference habitats. Species richness and abundance of the dominant coral, Porites astreoides, were nearly indistinguishable between the restoration structures and reference habitats after only six years. However, while abundance and size structure of P. astreoides populations are rapidly approaching those of the reference habitats (a convergence in size structure within 10 years was predicted), maximum coral size will take twice as long to converge for this species. The sensitivity of the model to maximum recruitment rates highlights the importance of recruitment on the recovery rates of restored habitats, suggesting that special attention should be afforded to provide coral recruits with appropriate recruitment substrate at the time of restoration. Lastly, the rates of convergence and, hence, the level of success of a restoration effort, were shown to be determined not only by the recruitment and survivorship rates of corals on the restoration structures, but by the characteristics of the reference population as well. Accordingly, reference populations ought to be considered as a "moving target" against which restoration success has to be measured dynamically. The simple, cost-effective monitoring-modeling approach presented here can provide the necessary tools to assess the current status of a restoration effort as well as to predict the time required for coral populations to resemble those found on undamaged reference habitats.

Tools to Assess Recovery Status and Convergence Rates Between Restored and Undisturbed Coral Reef Habitats

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