2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 245-13
Presentation Time: 4:45 PM


CRESSWELL, Jacque N.1, VAN HENGSTUM, Peter J.2 and ILIFFE, Thomas M.1, (1)Department of Marine Biology, Texas A&M University at Galveston, 1001 Texas Clipper Road, Galveston, TX 77554, (2)Department of Marine Sciences, Texas A&M University at Galveston, 1001 Texas Clipper Road, Galveston, TX 77554, jacque.cresswell@gmail.com

Submarine caves are circum-global coastal environments that host diverse endemic fauna and unique ecosystems. However, their response to coastal anthropogenic activity and urbanization remains unknown. In 1941 CE, sediment was dredged from a marine lagoon and pumped into a flooded sinkhole (Eve’s Pond) that was connected with Bermuda’s Green Bay Cave System. Given the sensitivity of benthic foraminifera to coastal disturbance and their preservation potential in the sediment record, our objective was to examine how the 1941 CE disturbance impacted cave benthic foraminfera. Sediment cores were collected along the cave tunnel that led to Eve’s Pond and examined with X-radiography, granulometry, radiocarbon dating, and foraminiferal paleoecology. In the downcore stratigraphy, a recent deposit of coarse-grained allochthanous lagoonal sand was clearly juxtaposed against the background fine-grained carbonate mud that has been accumulating in the submarine cave over the last ~1600 years. The benthic foraminiferal community prior to the 1941 CE event was comparable to other modern well-circulated and oxygenated benthic habitats in Green Bay Cave. In the 1941 CE sediment layer, lagoonal taxa dramatically increase (e.g., Quinqueloculina), while cave-dwelling foraminifera decrease (e.g., Spirophthalmidium, Sigmoilina). Immediately after the 1941 CE event, some benthic foraminifera were favorably impacted (e.g., Cyclogyra, Rotaliella), while others were negatively impacted (e.g., Sigmoilina, Globocassidulina) and some showed no impact. Sixty-four years later, the modern core-top benthic foraminifera in the tunnel impacted by the sediment injection event are indistinguishable from core-top assemblages in non-impacted cave tunnels with similar microhabitat environments. These results suggest some resiliency in the submarine cave benthos to minor disturbance.