Abstract Introduction Marl Prairie Habitat & Community Everglades Hydrologic History Methods Results > Discussion Conclusions Acknowledgements References Figures & Tables PDF

Sediment cores collected in the present marl prairie west of Shark River Slough contain records of distinct lithologic, hydrologic, and vegetation change during the 20^th century. The presence of peat in the lower part of the cores indicates sufficiently deep water for preservation of organic sediments before 1900 AD; moderate hydroperiods and water depths did not favor growth of carbonate-secreting periphyton. The upper 7-10 cm of each core consisted either of marl or marly peat, indicating the existence of shallower water and shorter hydroperiods that favored marl production and accumulation.

Peats deposited below ~10 cm in both cores represent pre-drainage assemblages, based on the radiocarbon date of 300 cal yrBP in core 03-9-16-6 and similarities in pollen assemblages from the two cores. These pre-20^th century assemblages (Pollen Assemblage Zone I) are analogous to sawgrass marshes and wet prairies present in the modern Everglades National Park, which possess sufficiently long hydroperiods to maintain sparse Cladium stands and accumulate organic sediments.

Sediments containing Pollen Assemblage Zone II were deposited during the 20^th century, based on modern radiocarbon dates from core 03-9-16-6 and the presence of Casuarina pollen in both cores. In this zone, pollen of Poaceae, Cyperaceae, Amaranthaceae, and Asteraceae doubled in abundance, and lithologic changes occurred. These assemblages are analogous to those from modern marl prairies. This evidence indicates the onset of shorter hydroperiods and shallower water than the sawgrass marshes that previously occupied the sites. Although paired ²¹⁰Pb and pollen analyses would be necessary to determine precisely when these changes occurred, these data clearly indicate that modern marl prairies west of Shark River Slough developed after 20^th century hydrologic modification of the system reduced flow to the region. These data stand in contrast to hypotheses that marl prairies west of Shark River slough were affected by extended flooding from flows through the S12A and S12B gates from WCA 3A. Rather, reconstructed vegetation patterns from these sites indicate initiation of drier conditions during the 20^th century.

Although marl prairie communities may have existed at other sites within the greater Everglades ecosystem prior to the 20^th century, plant communities at the sites analyzed in this pilot study consisted of sawgrass marshes before drainage of the system. These data indicate that the current spatial distribution and community composition of marl prairies are a response to water management and land cover changes of the 20^th century. Further sampling of modern marl prairie communities and adjacent communities is necessary to document the pre- and post- drainage distribution of marl prairie and associate faunal communities and to predict likely responses of marl prairie communities to anticipated changes in Everglades water management.