Mineral Distribution and Weathering in the Greater Everglades: Implications for Restoration

Abstract

The Greater Everglades encompasses two regions of mineralogical contrast—the Lake Okeechobee Basin (LOB) and the region south of the lake that includes the Everglades and Florida Bay. Lake Okeechobee is a transition zone with mineralogical similarities to both regions. Weathering in the LOB is mainly unidirectional and flow driven, whereas in the Everglades it tends to be cyclical and driven by diurnal and seasonal biogeochemical gradients. LOB soils formed in quartz-dominated marine sediments of various ages under diverse landscape, hydrology, vegetation, and weathering intensities. Calcite and quartz are dominant south of the lake, with quartz diminishing southward. Secondary calcite forms via algal photosynthesis to become a major constituent of marl soils and periphyton. Phosphorus immobilized via periphyton formation is mainly in microbial biomass, but calcite is essential to the process. Minerals of lesser abundance can have disproportionate ecological influence. These include phyllosilicates, oxides, sulfates, sulfides, and phosphates, which have roles in turbidity and biogeochemical processes affecting the fate of P, Hg, and possibly As. Mineral-related perturbations of ecological impact include inhibited precipitation of calcite in periphyton mats, enhanced Hg methylation via sulfide formation from agricultural sulfate, and entrainment of readily-suspended minerals via construction of canals. The nature and rate of Ca-P interactions bear on the rate of ecological recovery. Understanding the dynamics of mineral redistributions is critical for effective restoration.

KEYWORDS:

• arsenic mobilization
• calcium phosphate
• crystal growth rate inhibition
• Florida Bay
• Lake Okeechobee
• marl
• mercury methylation
• periphyton
• sulfate reduction
• turbidity

Notes

^aHIV = hydroxyl-interlayered vermiculite. ^bOxides include metal hydroxides and oxyhydroxides; noncrystalline analogues are common.