Radiocarbon Dating, Chronologic Framework, and Changes in Accumulation Rates of Holocene Estuarine Sediments from Chesapeake Bay

Colman, Steven M.; Baucom, Pattie C.; Bratton, John F.; Cronin, Thomas M.; McGeehin, John P.; Willard, Debra A.; Zimmerman, Andrew R.; Vogt, Peter R.

doi:10.1006/qres.2001.2285

Cited by 81 publications

(62 citation statements)

References 24 publications

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“…Perhaps, then, the expansive marshland observed today is a metastable, relict feature that developed under higher sediment supply rates in the past. For example, sedimentation rates in the Chesapeake Bay and Coastal Massachusetts increased 4 to 10 times after European settlement and deforestation (29,30), and marshes of the Plum Island Estuary in Massachusetts were likely restricted to the fringes of an open-water basin until some time after 680 years B.P. (31).…”

Section: Discussionmentioning

confidence: 99%

A coupled geomorphic and ecological model of tidal marsh evolution

Kirwan

Murray

2007

Proc. Natl. Acad. Sci. U.S.A.

457

433

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The evolution of tidal marsh platforms and interwoven channel networks cannot be addressed without treating the two-way interactions that link biological and physical processes. We have developed a 3D model of tidal marsh accretion and channel network development that couples physical sediment transport processes with vegetation biomass productivity. Tidal flow tends to cause erosion, whereas vegetation biomass, a function of bed surface depth below high tide, influences the rate of sediment deposition and slope-driven transport processes such as creek bank slumping. With a steady, moderate rise in sea level, the model builds a marsh platform and channel network with accretion rates everywhere equal to the rate of sea-level rise, meaning water depths and biological productivity remain temporally constant. An increase in the rate of sea-level rise, or a reduction in sediment supply, causes marsh-surface depths, biomass productivity, and deposition rates to increase while simultaneously causing the channel network to expand. Vegetation on the marsh platform can promote a metastable equilibrium where the platform maintains elevation relative to a rapidly rising sea level, although disturbance to vegetation could cause irreversible loss of marsh habitat. accretion ͉ erosion ͉ sea level ͉ vegetation ͉ wetland S ubsidence, erosion, sea-level rise, and anthropogenic changes to sediment delivery rates are affecting coastal marshes worldwide. In some regions these influences are converting significant portions of marshland to open water (1, 2). The fate of intertidal salt marshes is of societal importance and scientific interest; marshes provide highly productive habitat and serve as nursery grounds for a large number of commercially important fin and shellfish (3, 4). Additionally, marshes offer great value as buffers of coastal storms in cities such as New Orleans, which is separated from the Gulf of Mexico by marshland (5, 6).A variety of vertical accretion models have been used to address the response of tidal marshes to environmental change, including accelerated sea-level rise and reduced sediment supply (7,8). In these models, bed elevation of the marsh platform is adjusted according to a deposition rate that is proportional to water depth at high tide, a proxy for duration and frequency of inundation. In such models, an increase in the rate of sea-level rise is accompanied by an increase in water depth until the increasing deposition rate becomes equal to the sea-level rise rate. With the exception of recent work by Morris et al. (9), these models neglect the role of vegetation, despite Redfield's (10) hypothesis that vegetation and physical processes influence morphodynamics equally strongly in the intertidal zone. Vegetation traps inorganic sediment and provides a source of organic sediment. Based on field measurements, Morris et al. (9) argue that biomass density, and therefore deposition rates, increase with water depth up to some optimal depth. The role of biomass density in enhancing deposition rates in th...

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Section: Discussionmentioning

confidence: 99%

A coupled geomorphic and ecological model of tidal marsh evolution

Kirwan

Murray

2007

Proc. Natl. Acad. Sci. U.S.A.

457

433

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“…These cores vary in length from 0.5 to 20 m and contain histories of sedimentation rates, organic carbon sources, salinity and temperature regimes, O 2 conditions, and biological changes evidenced in microfossil assemblages and plant seeds over the last 12 000 yr (Colman et al 2002). Time lines have been established in cores using isotopic tracers (e.g.…”

Section: Sediment Record Of Eutrophicationmentioning

confidence: 99%

Eutrophication of Chesapeake Bay: historical trends and ecological interactions

Kemp¹,

Boynton²,

Adolf³

et al. 2005

Mar. Ecol. Prog. Ser.

1,261

1,019

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This review provides an integrated synthesis with timelines and evaluations of ecological responses to eutrophication in Chesapeake Bay, the largest estuary in the USA. Analyses of dated sediment cores reveal initial evidence of organic enrichment in ~200 yr old strata, while signs of increased phytoplankton and decreased water clarity first appeared ~100 yr ago. Severe, recurring deep-water hypoxia and loss of diverse submersed vascular plants were first evident in the 1950s and 1960s, respectively. The degradation of these benthic habitats has contributed to declines in benthic macroinfauna in deep mesohaline regions of the Bay and blue crabs in shallow polyhaline areas. In contrast, copepods, which are heavily consumed in pelagic food chains, are relatively unaffected by nutrient-induced changes in phytoplankton. Intense mortality associated with fisheries and disease have caused a dramatic decline in eastern oyster stocks and associated Bay water filtration, which may have exacerbated eutrophication effects on phytoplankton and water clarity. Extensive tidal marshes, which have served as effective nutrient buffers along the Bay margins, are now being lost with rising sea level. Although the Bay's overall fisheries production has probably not been affected by eutrophication, decreases in the relative contribution of demersal fish and in the efficiency with which primary production is transferred to harvest suggest fundamental shifts in trophic and habitat structures. Bay ecosystem responses to changes in nutrient loading are complicated by non-linear feedback mechanisms, including particle trapping and binding by benthic plants that increase water clarity, and by oxygen effects on benthic nutrient recycling efficiency. Observations in Bay tributaries undergoing recent reductions in nutrient input indicate relatively rapid recovery of some ecosystem functions but lags in the response of others. KEY WORDS: Eutrophication · Nutrients · Chesapeake Bay Resale or republication not permitted without written consent of the publisherChesapeake Bay is a large estuary which has undergone many changes in its ecological properties and processes in response to nutrient enrichment over the last 2 centuries. Susceptibility of the Bay to eutrophication arises in part from the long dendritic shoreline that intimately connects it to its large watershed (covering an area 15 times that of the Bay) which contains expanding human population centers and extensive agricultural activities. (Satellite image from MODIS,

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“…In this study, shell samples have been calibrated using the global average marine reservoir correction (᭝R ϭ0), for the following reasons. First, where recorded, near-zero ␦ 13 C values indicate a marine source of carbon (Colman et al, 2002). Second, while a strong, upwelling-related offset has been identified for the southern Portuguese margin (᭝R ϭ235 Ϯ35 14 C yr) (Soares, 1993), the same study also identified considerable variability between locations including a ᭝R value of 5 Ϯ70 14 C yr at Vila Real de San Antonio at the mouth of the Guadiana and a general reduction in ᭝R prior to 2000 14 C yr.…”

Section: Chronologymentioning

confidence: 99%