PRISTINE TO MODERN: A COMPARISON OF SHALLOW-WATER MODERN AND MID-HOLOCENE BENTHIC FORAMINIFERAL ASSEMBLAGES FROM COASTAL BOCAS DEL TORO, PANAMA

Coral reefs and other coastal marine habitats have declined in the last few decades. Although anthropogenic disturbance is a factor, reefs are known to have naturally thrived and declined over geologic time. We are using benthic foraminifera as an environmental proxy to compare modern, marine coastal habitats of Bocas del Toro, Panama (BDT), to a “pristine” Acropora cervicornis-dominated reef on Isla Colon, the largest island in the BDT archipelago, to suggest the cause of both natural and human-influenced changes. Bocas del Toro is an ideal location to study these changes because coastal habitats remain mostly intact and human settlement there was fairly recent ~AD 690, with significant anthropogenic disturbance such as land clearing and pollution not occurring until the late 1880s. However, changes in physical parameters such as water clarity and sediment load and changes in mollusk and coral communities suggest water quality in BDT has declined.

This study analyzes and compares the community structure of benthic foraminiferal assemblages from 38 sediment samples from BDT, including 20 shallow-water (~2 m avg.) modern samples and 18 from the mid-Holocene reef on Isla Colon. Unpublished ¹⁴C and U-Th ages from in situ A. palmata and A. cervicornis date the mid-Holocene subfossil samples to ~7.2-5.8k YBP. Initial cluster analysis results show clear differences between the mid-Holocene and modern samples, with few similarities. Seagrass and mangrove habitats are well-differentiated from reefal habitats, without respect to age. Mangrove samples show the least diversity, with near-even diversity between seagrass and reefal samples. Two proposed explanations for these results are 1) the modern samples were collected from coastal habitats in Almirante Bay which incorporate physiographic differences and coastal effects such as runoff and sediment input from nearby mountains, whereas the subfossil samples may reflect a normal, marine setting resulting from the isolation of Isla Colon from the mainland and 2) pollution and anthropogenic land-use changes have altered the modern coastal habitats. Ongoing analyses will help determine the cause for the observed differences between the ages, which has implications for the preservation and future restoration of coastal, tropical habitats.