Representation focuses on ensuring that all ecosystems and habitats within the region are represented in the MPA network. Representation at the habitat scale assumes that by representing all habitats, most elements of biodiversity (species, communities, physical factors, etc.) will also be represented in the network. Biodiversity changes locally, regionally, and with latitude. To address the changes in biodiversity across space, each MPA should be carefully placed to capture the full diversity of reef types and adjacent linked habitats, and to include the diversity of characteristics/conditions of the area. In addition to the biological characteristic of an area, the physical factors across an area need to be represented within the network of MPAs. This helps to build in the resilience by including a variety of conditions that may confer resilience.
When assessing representation for MPA network design, three universal factors should be considered and accounted for in the planning:
- Biodiversity composition: each habitat supports a unique community, and most marine animals use more than one habitat during their lives.
- Biogeographic structure: the environmental/latitudinal gradients in habitats and species composition that should be represented.
- Ecosystem integrity: maintenance of the ecological processes of the system is as important as representing all habitats.
MPAs should contain many different reef zones and habitats to maintain a full complement of biodiversity, and a steady, varied supply of larvae to replenish damaged areas and to replace dead or emigrated organisms (see Biodiversity and Replication).
Different reef types, depths, and zones within reefs are characterized by different coral assemblages, and different responses to temperature stress and bleaching. There are different species of corals and community types found in shallow lagoons, reef flats and reef crests. Others are found down the reef slope, and may only occur deeper than ~20 meters. Dominant corals and coral diversity differ in each assemblage. For example, sheltered reefs may have dense overlapping colonies of staghorn coral (Acropora) or large whorls of leafy corals (Montipora, Pachyseris, Echinopora) that are aesthetically pleasing, but have few species. Such reefs may be valuable for tourism, but are less so for conserving a representative range of biodiversity. They also tend to be more susceptible to bleaching.
To identify representative and unique habitats, a simple multidimensional classification of habitat, including, but not limited to, depth, exposure, substrate, and dominant flora and fauna is essential in MPA design. In practice, three categories of habitats should be considered for inclusion in coral reef MPAs to attain adequate representation:
- Coral habitats
- Contiguous habitats (i.e., submerged, intertidal, or above water) (see Linked Habitats)
- Habitats linked across far distances (see Connectivity)
To address the biogeographic structure of the area, the reef type and major reef zones of each bioregion should be protected and geographically represented (e.g., at different latitudes) to reduce potential threats at each site. The MPA should aim to capture the onshore-offshore or habitat-habitat ontogenetic (or life-stage) shifts of species. For example, the MPA should capture the gradient from mangrove to reef as fish move from larval to adult stages, respectively.
Ecosystem integrity refers to the degree to which a given area (potential MPA site) functions as an effective, self-sustaining ecological unit. Distinct processes and physical attributes give rise to different coral reef communities; for example, seaward reefs endure greater wave stress than back reef lagoons. These distinct processes are reflected in variations of coral assemblages and zonation patterns. The protection of ecosystem processes is equally important as the protection of all habitats. Representation of physical factors of the area helps to build resilience into the MPA network. MPAs should be placed in areas that capture all major physical characteristics including:
- Energy regimes
- Wave energy
- Weather patterns
- Strong currents
One method to protect biodiversity is to include representatives of all habitats in all biogeographic regions into MPAs.1 MPAs should be designed at a system-level, recognizing patterns of connectivity within and among ecosystems. When possible, MPAs should include the entire ecological unit (e.g., coral reef and associated seagrass-mangrove systems, dominant physical attributes/characteristics of an area). Identifying the latitudinal gradients in community structure of the coral reef will help to characterize the biogeographical patterns in species distribution and abundance and support adequate representation of the bioregion. Comprehensive representation of the bioregion can be achieved by including the full range of ecosystems/habitat recognized at an appropriate scale across and within each bioregion. The MPAs in the network should reflect the biotic diversity of the marine ecosystems in the biogeographic region.