UPMSI’s Kubi Follosco (second left) and DLSU’s Cai Sampson (far right) with members of the local community on their third field visit to El Nido for the CCRES project. (Picture: Gia Albano)

Measuring sedimentation in old-growth mangroves

The services which mangroves and seagrasses provide to coastal communities across the East Asia-Pacific region include preventing beach erosion and regulating water quality.

By trapping sediment (“sedimentation”), including fine particles that might otherwise stress adjacent coral reefs, mangroves and seagrasses stabilise beachfronts and filter water entering lagoons.

Among the research activities of CCRES in El Nido on the island of Palawan in the Philippines is a project to measure rates of sedimentation in mangroves over a gradient of genera-specific zones.

The mangroves of Barangays Aberawan and Manlag in El Nido are old, natural growth lining the banks of rivers in the area and extending seaward to Bacuit Bay.

The assorted forms of several resident genera contribute to a complex lattice of gnarled roots, stems, and branches. In Manlag, the mangrove forest is fronted by expansive seagrass meadows populated by hardy, long-lived Enhalus species.

These sites, along with another on Cadlao Island, are helping CCRES researchers from De La Salle University (DLSU) and the University of the Philippines Marine Science Institute (UPMSI) better understand the role of mangroves and seagrass in stabilizing the coast and regulating water quality.

One field activity involves the deployment of settling disks to measure just how much sediment accumulates in the different mangrove zones. Another is sediment characterization to potentially determine likely origins. Growth patterns of the seagrass Enhalus are also being analyzed because these reflect changes in sediment elevation.

The mangrove and seagrass research team (Component I) is led by Dr. Cai Samson from DLSU. The team’s field trip in March marked its third outing, with a fourth planned soon after.

-  Kubi Follosco, UPMSI, Manila.