129-64 Fern Spores From Inland Lake Sediment Core Indicate Floral Change at Poisonwood Blue Hole, New Providence, The Bahamas

Abstract:

The Bahamas supports a remarkable diversity of endemic plants, birds, reptiles, and marine life, but these ecosystems are threatened by climate change, including projected sea-level rise and increased hurricane intensity, as well as coastal development, pollution, and invasive species. Creating a natural baseline for Bahamian terrestrial communities and better understanding how these communities have reacted to environmental shifts in the past, can help inform conservation and management strategies in the present. Ferns are diverse and encompass a wide variety of habitats in The Bahamas, with preserved spore records offering a useful proxy to their past abundance. The Bahamas is an optimal setting for the study of these records due to its well-documented human habitation, diverse climatic history, and wealth of depositional sites. Analyzing trends in spore records allows us to track shifts in fern communities through time, infer past environmental conditions, and define ecological baselines: environmental conditions before human influence. A spore record obtained from a sediment core from Poisonwood Blue Hole (PWBH) on New Providence Island, The Bahamas, allows us to reconstruct the past environment, identify when and how the environment shifted naturally or as a result of human disturbance, and see how the plant community responded to these changes.  

We have identified three major fern species in the PWBH sediment core record: Acrostichum aureum, Pteridium aquilinum, and Phlebodium aureum. We analyzed fern diversity and abundance over time and defined three distinct zones within the core. Beginning at the bottom of the core ~6500 cal yr BP, Zone 3 is dominated by wetland ferns (A. aureum) and likely represents a shallow wetland. Zone 2, beginning ~1150 cal yr BP, is defined by an increase in epiphytic (P. aureum) and coppice ferns (P. aquilinum). This zone occurs concurrently with spikes in charcoal and pine pollen seen in other floral records consistent with Lucayan habitation and agricultural burning. Zone 1 is defined by the loss of the previously mentioned epiphytic and coppice ferns and returned dominance of wetland ferns. Abundance of fern spores throughout the sediment core can help us reconstruct past environmental conditions, as well as floral shifts due to both natural and anthropogenic stress. Ecological baselines, which represent what the floral community was like, could be used to aid in local plant conservation efforts.

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