The question about how to identify reef resiliency (the reef endurance and recovering capacity) in the Mesoamerican Reef Region (MAR) has been an interesting issue since certain time ago. To progress in this theme, and within the Mesoamerican Reef Program (MAR) The Nature Conservancy (TNC) is planning to identify and accelerate the conservation work on the regional resilient reefs. The currently initiative work is presented below.
Resiliency has been defined as (1) the disturbance amount that an ecosystem can support without modifying its own processes and structures; (2)the time that a system needs to return to its stable state after absorbing a disturbance or, as the (3) the system ability to overcome, absorb and respond to changes and disturbances, without modifying its own functions and controls. Considering the reef whitening, reefs are defined as resilient when although their colonies are whitening and partially or completely dead, the reef coral communities rapidly recover reaching their initial state.
Whitening is coral and other composed animal response to symbiotic algae. Whitened corals have lost the symbiotic zooxantela algae and they turn into white color. In extreme cases of whitening, corals die. Whitening can be caused by a wide range of factors such as high temperatures, high ultraviolet sun radiation levels, salinity level changes, bacterial infection and chemical contamination. The whitening susceptibility differs among sites and species, in such a way that there are resistant areas (corals do not whiten) and resilient ones (corals do whiten and may be die, but the community itself is able to recover).
To identify resilient corals, factors that promote a coral community resiliency or rapid whitening recovery should be examined and then identify the resilient community sites. These communities provide a vital refuge, which is essential to the recovery and survival of prone to severe whitening degradation areas.
In the TNC resiliency reef model four elements are identified and they are: connectivity, refuge, representativity and replicability, and effective management. Connectivity is manage by the MAR Program through the development of ocean circulation models with the input of life cycle information of selected species in order to identify the larva source and destination. The practical management is being covered by effectiveness monitoring and management workshops of the Marine Protected Areas (MPA), during those workshops strength and weak management issues are identified. The other two components, representativity and replicability, are planned to be covered by the other initiatives. Eco-regional MAR Evaluation (using a decision making tool) and Rapid Reef Evaluation (using a standard protocol), the last one will be emphasized.
Representativity and replicability have to do with protection, in many sites – to alleviate the risk of total lost representative habitats, including the habitat of the targeted species. Different reef habitats are related with geomorphology, latitude, coast distance, land influence, and wave energy and ocean current effects. The purpose is to mainly identify reef type habitats in the MAR region using the Millenium Project maps and by means of the Ecoregional Evaluation that considers the geography, coast distance; land proximity influence, energy and sea currents. Moreover, through Reef Rapid Evaluation it will be possible to identify more precisely different habitat and community coral types and their associated organisms. Using satellite maps it will be possible to generate a reliable classification scheme of all reef types and the main reef zones that will assure a more thoroughly representation of biodiversity protection.
During the Rapid Reef Evaluation, shadiness records are used as a proxy to identify reefs where a shadow effect could be taking place. This evaluation will also identify and map superficial reefs, including reef lagoon, as well as those that due to their permanent adverse condition exposure, have a higher tolerance to a wide range of environmental conditions.
Other characteristics to be considered during the Rapid Reef Evaluation, useful to identify resilient reefs, include reef with high rate of living coral over dead coral and a wide range of size and age distribution, reef with oldest coral, high abundance of whitening resistant species, or reefs that have already undergone high temperature o whitening events.
They will also be considered resilient reefs, those that show high specie diversity, abundant and uniform reefs, as well as those areas with a wide range of coral colony size in different reef zones and a generally, high alive coral cover.
The Rapid Reef Evaluation will allow identifying high recruitment level areas, being current or potential, like those reefs with large recruit coral abundance or those with plant eating fish or porcupine high density, or with a low macro alga cover, that can prepare a successful recruitment substrate. Finally, the Eco-regional Evaluation as well as the Rapid Reef Evaluation will allow standing out those reefs that are under little or none anthropogenic stress.
Once resilient reefs have been identified in the Mesoamerican Reef region, it will be possible to compare and contrast resilient reef geographical distribution and those reefs in which the MRP presence implied any protection activity. This will enable to identify reef conservation gaps as well as to improve zonation schemes to protect specific MRP areas. Besides, the resilient reef mapping will enable MRP to centre its limited resources to high relative importance areas, such as whitening monitoring programs to try the hypothesis that resilient reefs are less affected by massive whitening events.