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The physical properties of lagoon and mangrove deposits.
Abstract
Summary only. The deposits of mangrove swamps and tropical lagoons are varied and range from coarse sands through mixed deposits to muds and clays. Many are saline with relatively high organic contents. The prevailing high fairly constant temperature is of major influence on the physical properties. Analysis of deposits in terms of closely graded fractions permitted the approximation of sands to systems of uniform spheres. Measurements of the porosity and permeability of such grades at different degrees of packing and at different temperatures were made; porosity and permeability were related linearly at constant temperature for different levels of packing except when the system approached the limits of close packing. Permeability at constant porosity rose with temperature at the average rate of 3.6% per °C. Deposits of given composition are thus considerably more permeable at the high temperatures of the tropics than in cooler regions. In submerged deposits exchange of interstitial water largely depends on convection arising from temperature differences. In the tropics these differences are relatively slight so that, despite higher permeability, nutrients would tend to remain locked within the deposits and not to be released into the water above.