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The Natural Resources Staff at War in the Pacific NHP is currently conducting a study to determine the spatial and temporal patterns of sedimentation on the park's coral reefs. This year-long project is measuring sedimentation rates at fifty sites along roughly two linear miles of reef using sediment collectors placed on the bottom at two depths (thirty and sixty feet). Sediment collectors are returned to the lab every twenty-one days and all collected dirt is dried and weighed. In addition to the dry weight, the percent of organic material and percent of carbonates is also determined using Loss on Ignition techniques. Sediment grain size is also determined. These descriptive measures allow the park staff to estimate how much of the collected sediments are coming off the land in runoff and how much are naturally occurring marine derived sediments such as beach sand.
At each site, additional data collection is also planned (and is scheduled to begin in the coming months). This includes collecting basic water quality data (e.g. temperature and light availability), coral larval recruitment data, and an assessment of the coral reef community present at the study sites.
Field work and data collection on this project has been running for approximately months, and results are currently, too preliminary to draw conclusions. The park staff hope to have sufficient data by late summer to move into Phase II of their work, developing a series strategies to try and reduce sediment loads on the reef. This will most likely involve the development and implementation of a series of Best Management Practices (BMPs) to reduce upland soil erosion, runoff and sedimentation coupled with active land management and restoration. Without better land management, Guam's diverse and beautiful coral reefs may become a thing of memory.
Dwayne Minton
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