Schultz, Emily Anne (2015-11). Characterizing the Taphonomically Active Zone in Subtropical Peat from Barnes Sound in Key Largo, Florida. Master's Thesis.
Thesis
Surficial mangrove peat from Barnes Sound in Key Largo, Florida preserves very thick leaf mats (19-37 stacked leaves). The incoherent leaf mat occurred below the coherent leaf mat to a depth of approximately 5 cm, and consisted of degraded and fragmented leaves intruded by living horizontal and vertical rootlets. Short cores (13 cm deep) indicated that the peat below the coherent and incoherent leaf mat consists primarily of living and dead roots and rootlets, large pieces of wood, and fecal pellets. Taphonomic analysis of 100 leaves from the coherent leaf mat at Barnes Sound indicated that fallen leaves record canopy herbivory and parasitism, as well as the decomposition pathways occurring on the mire surface: microbial decomposition and detritivory by snails. Canopy herbivory and parasitism by micro-arthropods, insects and the mangrove crab was most prominent. Abundant fecal pellets (106 um - 2 mm), edge feeding, and skeletonization in the coherent and incoherent leaf mats indicated the importance micro-detritivores. Shells belonging to the detritivorous neogastropod Melampus coffeus occurred in the core, but leaf deterioration by M. coffeus was hard to distinguish. Leaves showing attack patterns characteristic of detritivorous mangrove crabs appeared in the coherent leaf mat, but no crab burrows appeared on the mire surface. Macro-detritivores (specifically crabs) play an important role in the decomposition pathways in many modern mangrove mires. Mangrove peat at Barnes Sound preserved an exceptionally thick leaf mat, possibly due to the scarcity of detritivorous mangrove crabs at this locality. If crabs are reduced or absent, thick leaf mats can accumulate in saltwater mires. Our results indicate that in the absence of these and similar macro-detritivores, thick leaf mats could have accumulated in ancient saltwater mires. Low shoot-to-root ratios and the presence of thick leaf mats cannot confidently be used as taphonomic indicators of freshwater peat.
