29 Reconstructing Paleo-Environmental Changes (Posters)

Friday, 29 March 2019
8:00 AM - 12:00 PM
Carolina Ballroom

THE IMPRINT OF SEA-LEVEL RISE AND LAND-USE CHANGE ON OYSTER HABITATS IN A SMALL TRIBUTARY CREEK OF THE UPPER CHESAPEAKE BAY

Paper number: 29-18
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Indicators of sea-level rise and enhanced terrestrial sediment fluxes associated with colonial deforestation and land-use change are observed throughout estuaries of the U.S. East Coast. Here, we use multiple paleoenvironmental proxies to extend that record to a small tributary creek in the Upper Chesapeake Bay (Maryland, USA), and explore the impacts of pre- to post- Colonial land-use change on sediment deposition and the role of rising sea level and the impacts of these changing environmental conditions on the quality of local oyster habitats. Two 7 m long vibracores were collected in June 2018 along a longitudinal transect in Cheston Creek, a small tributary with a < 1 km2 watershed. Cores were sampled at decimeter resolution and sediments analyzed for bulk density, grain size, loss-on-ignition and bulk carbon and nitrogen content. Core age models were developed from radiocarbon dating of in situ marine shells and terrestrial root fragments found in the cores, and show that the upper and lower creek cores capture 5100 and 2900 years of deposition, respectively. Results demonstrate that the creek overall experienced a gradual decrease in grain size, organic matter content, and bulk density, indicating the transition towards more estuarine conditions and deeper water during a 2000-year period of slow sea-level rise prior to European colonization. Drowning of the proximal creek edge is recorded prior to colonization as an abrupt fining of sediments and decrease in C:N, denoting enhanced aquatic organic matter input. Cheston Creek sediments record a rapid increase in terrestrial organic matter inputs, which coincided with additional expanded human use of the local ecosystem, including widespread oyster consumption. During the 18th and 19th Century anthropogenic activities like deforestation and massive agriculture in the Chesapeake Bay, increased sediment inputs to Bay tributaries, and extensive eutrophication in the upper Chesapeake Bay. Our results confirm earlier studies of enhanced terrestrial sedimentation to Chesapeake Bay associated with European Colonization but extend this to even the smallest of estuary tributaries, and link these changes with coincident degradation of oyster habitat and populations.

Geological Society of America Abstracts with Programs. Vol. 51, No. 3

doi: 10.1130/abs/2019SE-326567

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