Wetlands on Guam occur predominantly in the southern one half of the island. This is an underpopulated region of small coastal villages separated by steep and rolling topography etched into volcanic rocks. Terrains are variously covered with grasslands or ravine forests, or they have degenerated into badlands. End-member wetland types include tidal estuarine, tidal riverine, non tidal riverine, permanent palustrine, and ephemeral palustrine, but combinations of these are common. Their origin, distribution, evolution, and vulnerability are related to bedrock geology, soil and slope processes, tectonics, sea level changes, and to land use modifications. Their function and value as to flood control and affecting water quality are the subject of considerable research at WERI.

This project is aimed at developing a geochemical-sedimentation model that describes the flux of metals and nutrients being stored and moving through a perennial palustrine wetland downslope from a large tract of badlands. The study involves establishing hydrologic parameters, measuring slope retreat and sediment throughput out of the badlands, and chemically analyzing surface runoff and wetland pore waters, the latter through a gridded lysimeter array in the wetlands. Preliminary analysis of pore waters indicates that the wetlands are mobilizing and storing iron and manganese that enter from the badlands via groundwater seepage and in suspension. Concentrations of those metals may exceed three orders of magnitude beyond normal Guam river waters.

The project has been funded by the Government of Guam, Bureau of Planning. Future related research will involve a) analyzing geochemical cycling in tidal riverine and estuarine wetlands, b) quantifying badlands denudation rates, c) studying geochemical reactions involving manganese and iron in the wetlands and downstream at the coast where they are co-precipitate on reef debris.

For More Information on Wetlands Projects send e-mail to Dr. H. Galt Siegrist: [email protected]