Ecology of recovering degraded reef communities within no-take marine reserves

No-take marine reserves are a highly advocated tool to recover degraded marine ecosystems, but we have limited evidence as to how marine reserves facilitate recovery of marine communities. To address this limitation, we conducted monthly underwater visual censuses over three years on 423 reef fish species in eight sites where fishing had been excluded for different lengths of time.

We then used our data to assess four impacts of protection within no-take marine reserves in the central Philippines: (1) magnitudes and rates of reef fish community recovery; (2) changes in reef fish diversity; (3) patterns of reef fish community succession; and (4) shifts in community interactions, based on distributions of pairwise correlations among reef fish species biomass.

We found that total fish biomass increased with the duration of protection, but total fish abundance and species richness or diversity were both more influenced by site location than by reserve age. In addition, large-bodied herbivores drove the biomass recovery in older marine reserves, while small-bodied zoobenthivores and zooplanktivores influenced the higher abundance in offshore sites.

Moreover, our results showed that ubiquitous large-bodied herbivore species (e.g. Chlorurus bleekeri) increased in biomass dominance in older reserves, whereas ubiquitous medium-bodied species (e.g. Thalassoma lunare) lost biomass dominance. Our non-metric multidimensional scaling (MDS) representation of reef fish community trajectories with duration of protection showed convergent trends in sites within similar locations relative to the mainland.

Finally, the frequency distribution of pairwise correlation values among species biomass time-series within each site showed positive mean values regardless of protection-duration, as is typical of disturbed or high diversity systems. Indeed, less than ten percent of common species (those present in ≥50% of the 33 monthly surveys) within each site showed significant decline over time, while about 40 percent showed significant increase.

In summary, our research provides comprehensive evidence on how marine reserves recover depleted reef fish communities. However, it also emphasizes that understanding of reef ecological processes could improve marine reserve site selection and design in order to meet specific conservation goals of marine reserve establishment.

Anticamara, J.A (2009). Ecology of recovering degraded reef communities within no-take marine reserves. Doctoral dissertation, University of British Columbia, Canada.