Ecological Indicators

A framework for measuring coral species-specific contribution to reef functioning in the Caribbean

Highlights

  • The configuration of coral communities determines ecosystems’ functioning.
  • There is a high variation in the functional contribution of Caribbean corals.
  • Reef functioning depends on the dominance patterns of key reef-building corals.
  • We propose a framework to assess the functional potential of Caribbean corals.
  • This approach serves to estimate reef condition under rapid ecological change.

Species morpho-functional traits provide general and predictable rules to understand the dynamics of ecological communities; therefore, considering species identity is crucial in understanding ecosystem functioning. Here, we propose a framework to estimate the species-specific functional contribution of Caribbean corals according to their capacity to create complex three-dimensional structures by means of calcium carbonate precipitation and their morphological complexity. We use a combination of field data and bibliographic information to integrate a Reef Functional Index (RFI) that considers the calcification rate, structural complexity and abundance (cover) of each coral species. As an example application of this tool, we evaluated various sites along the Mesoamerican Reef showing that the RFI can be used to compare reef sites or communities. The construction capacities of Caribbean coral species are highly variable, thus, different species configurations of a coral community result in a high level of functional variation. Most coral assemblages on the Mesoamerican Reef show non-framework species dominance (e.g. Undaria spp. and Poritesastreoides), compromising reef functioning. However, sites with key reef-building species present showed considerably greater functioning despite those species not being dominant. The functional approximation for coral species proposed can be used by future studies considering changes in coral community compositionkeystone species loss or to estimate reef function loss due to climate change or other stressors.

Date
2018
Data type
Scientific article
Theme
Research and monitoring

Evaluation of coral reef management effectiveness using conventional versus resilience-based metrics

With increasing stressors to coral reefs, defining tools that evaluate their dynamics and resilience is important to interpret system trajectories and direct conservation efforts. In this context, surveys must go beyond conven- tional monitoring approaches that focus on abundance and biomass of key groups and quantify metrics that better assess ecological processes and ecosystem trajectories. By measuring a variety of conventional (e.g. proportional cover of broad benthic groups, biomass of herbivorous fish) and complementary resilience-based metrics (e.g. algal turf height, coral recruitment rates, juvenile coral densities, herbivorous fish grazing rates), this study evaluated the ecosystem responses to community-based management in Fiji. The study was conducted across three paired tabu areas (periodically closed to fishing) and adjacent fished sites. Conventional metrics reflected no management effect on benthic or herbivorous fish assemblages. In contrast, the complementary metrics generally indicated positive effects of management, particularly within the benthos. Significant differ- ences were observed for turf height (33% lower), coral recruitment rate (159% higher) and juvenile coral density (42% higher) within areas closed to fishing compared to adjacent open reefs. In addition, turf height was in- versely related to coral recruitment and juvenile coral density, and longer turfs (≥5 mm) were more competitive in interaction with corals. These results emphasise that conventional metrics may overlook benefits of local management to inshore reefs, and that incorporating complementary resilience-based metrics such as turf height into reef survey protocols will strengthen their capacity to predict the plausible future condition of reefs and their responses to disturbances. 

Date
2018
Data type
Scientific article
Theme
Research and monitoring