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Title: Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise

Abstract

Sea-level rise is a major factor in wetland loss worldwide, and inmuch of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mmyr -1 due to regional subsidence.Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, andmay exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidal freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mmyr -1 in elevation on average, at least 5 mmyr -1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among themarshes studied, and ranged from-9.8 ± 6.9 to 4.5 ± 4.3 mmyr -1. Surface accretion of depositedmineral and organic matter was uniformly high across the estuary (~9–15 mmyr -1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associatedmore » salinity regime were not related to elevation change or surface matter accretion. In conclusion, previous studies have focused on surface elevation change inmarshes of uniformsalinity (e.g., salt marshes); however, our findings highlight the need for elevation studies inmarshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries.« less

Authors:
 [1];  [2];  [2];  [3]
  1. Univ. of Maryland, College Park, MD (United States); Northwest Indian Fisheries Commission, Olympia, WA (United States)
  2. Univ. of Maryland, College Park, MD (United States)
  3. Univ. of South Alabama, Mobile, AL (United States)
Publication Date:
Research Org.:
Univ. of Maryland, College Park, MD (United States)
Sponsoring Org.:
U.S. Department of Energy, National Institute for Climatic Change Research; USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1377826
Grant/Contract Number:
TUL-543-06/07
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
PLoS ONE
Additional Journal Information:
Journal Volume: 11; Journal Issue: 7; Journal ID: ISSN 1932-6203
Publisher:
Public Library of Science
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; marshes; salinity; estuaries; sediment; fresh water; wetlands; linear regression analysis; decomposition

Citation Formats

Beckett, Leah H., Baldwin, Andrew H., Kearney, Michael S., and Cebrian, Just. Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise. United States: N. p., 2016. Web. doi:10.1371/journal.pone.0159753.
Beckett, Leah H., Baldwin, Andrew H., Kearney, Michael S., & Cebrian, Just. Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise. United States. doi:10.1371/journal.pone.0159753.
Beckett, Leah H., Baldwin, Andrew H., Kearney, Michael S., and Cebrian, Just. Thu . "Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise". United States. doi:10.1371/journal.pone.0159753. https://www.osti.gov/servlets/purl/1377826.
@article{osti_1377826,
title = {Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise},
author = {Beckett, Leah H. and Baldwin, Andrew H. and Kearney, Michael S. and Cebrian, Just},
abstractNote = {Sea-level rise is a major factor in wetland loss worldwide, and inmuch of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mmyr-1 due to regional subsidence.Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, andmay exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidal freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mmyr-1 in elevation on average, at least 5 mmyr-1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among themarshes studied, and ranged from-9.8 ± 6.9 to 4.5 ± 4.3 mmyr-1. Surface accretion of depositedmineral and organic matter was uniformly high across the estuary (~9–15 mmyr-1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associated salinity regime were not related to elevation change or surface matter accretion. In conclusion, previous studies have focused on surface elevation change inmarshes of uniformsalinity (e.g., salt marshes); however, our findings highlight the need for elevation studies inmarshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries.},
doi = {10.1371/journal.pone.0159753},
journal = {PLoS ONE},
number = 7,
volume = 11,
place = {United States},
year = {Thu Jul 28 00:00:00 EDT 2016},
month = {Thu Jul 28 00:00:00 EDT 2016}
}

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  • Estuaries are geologically transitory features whose evolution depends on a delicate balance among relative sea level basin geometry, shoreline erosion, fluvial sediment discharge, littoral drift, and tidal exchange. Models of modern estuarine development require specific sea level scenarios; almost all assume a continuation of the decelerating sea level rise of the last few thousand years. However, under constant external conditions, estuaries are ephemeral because they rapidly fill with fluvial and marine sediment. The rate of filling changes with time, but only a few thousand years are required to fill most estuaries. The persistence of estuaries, therefore, requires that relative seamore » level rises at a rate sufficient to compensate for the inherent tendency of estuaries to fill with sediment. Coastal plain estuaries, of which Chesapeake Bay is a prime example, are often referred to as drowned river valleys. Although this description is appropriate for the first-order morphology of Chesapeake Bay, the implied passivity can be misleading, especially in the high-tidal-energy area of the bay mouth where dramatic spit progradation and channel migration have occurred in the last few thousand years. Holocene sediment accumulation rates are more irregular along the length of the estuary than most models would predict; but in general, sediment accumulation has been greater at the mouth and at the head of the bay and less along the middle reaches. If relative sea level were to stabilize, the estuary would fill with sediment from both ends within a few thousand years. Evidence for two previous generations of the bay is preserved as the estuarine fill of major fluvial valleys, demonstrating that estuarine episodes have been closely tied to cyclic sea level changes.« less
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