Incorporating Connectivity
Understanding the physical processes of an area, such as eddies and currents, enables managers to better identify source and sink reefs and to link these into a network of protected areas. This figure displays eddies in the Gulf of Mexico. Red circles in the figure are eddies that rotate clockwise, and the blue circles rotate counter-clockwise. Eddies are important to the regional ecosystem because they transport nutrient-rich coastal waters and organisms, and their recurrence, intensity, and persistence have biological effects. Image courtesy CCAR Real-Time Altimeter Data Group
A network of MPAs should maximize connectivity between individual MPAs to ensure the protection of ecological functionality and productivity.1 In this toolkit, connectivity and ecological linkages include:
- Connections of linked habitats such as coral reefs and seagrass beds, or among mangrove and seagrass nursery areas and coral reefs
- Connections through regular larval dispersal in the water column between and within MPA sites.
- Regular settlement of larvae from one MPA to inside another MPA
- Marine life adult movements in their home range, from one site to another, or because of spillover effects from MPAs
Persistence of a population in an MPA network depends on two mechanisms:
- self-persistence of local populations
- persistence that depends on connectivity among all or many locations in the network
In the context of MPA design, the potential for network persistence may be an important consideration when it is impossible to ensure that any single MPA will be self-persistent. Moreover, a network of self-persistent MPAs may be more resilient to local disturbances than a network-persistent system would be.2
Therefore, it is important to take a system-wide approach in the design of MPA and MPA networks, one that recognizes patterns of connectivity within and among ecosystems (including the linkages among coral reefs, seagrasses, mangroves, watershed, etc.), as well as the connectivity between two populations. The strength of connectivity between locations depends on the abundance and fecundity of source populations, how far larvae disperse before settling to adult habitat, spawning sites and movement patterns of adults, as well as oceanographic effects (e.g., current patterns and retention features).
Linked Habitats, Larval Dispersal, Adult Movement Patterns, and Size and Spacing provide detailed information and guidelines on ways to account for connectivity elements in the MPA design.