The Impacts of the Middle Holocene High Sea-Level Stand and Climatic Changes on Mangroves of the Jucuruçu River, Southern Bahia – Northeastern Brazil

Fontes, Neuza A.; Moraes, Caio Alves de; Cohen, Marcelo Cancela Lisboa; Alves, Igor Charles Castor; França, Marlon Carlos; Pessenda, Luiz Carlos Ruiz; Francisquini, Mariah Izar; Bendassolli, José Albertino; Macario, Kita C. D.; Mayle, Francis E.

doi:10.1017/rdc.2017.6

Cited by 33 publications

(33 citation statements)

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“…Considering a RSL higher than the modern one and a stable fluvial discharge during the middle Holocene, mangroves would have expanded on flood plains and accumulated organic mud banks in higher topographic zones above the modern tidal range. Such a situation was recorded in a floodplain of the Jucuruçu River, near the city of Prado‐Bahia, north‐eastern Brazil, 23 km distant from the coastline, where a stratigraphic succession revealed the presence of an estuarine system with tidal flats colonized by mangroves and sedimentary organic matter sourced from estuarine organic matter 3.4 ± 1.35 m above the modern mangrove zone during the middle Holocene (Fontes et al, ).…”

Section: Interpretation and Discussionmentioning

confidence: 92%

Allogenic and autogenic effects on mangrove dynamics from the Ceará Mirim River, north‐eastern Brazil, during the middle and late Holocene

Ribeiro

Batista

Cohen

et al. 2018

Earth Surf Processes Landf

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It is possible that climate changes and sea level fluctuations (allogenic processes) are and will cause major changes in mangrove dynamics. However, other driving forces may be significantly affecting this system. Distinguishing allogenic and autogenic influence on mangroves is a challenging question, because mechanisms related to the natural dynamics of depositional environments (autogenic processes) have strong influences on the establishment and degradation of mangroves. Thus, impacts on mangroves caused by autogenic processes may be erroneously attributed to allogenic mechanisms. Therefore, it is imperative to identify the ‘fingerprint’ of global changes in modern mangrove dynamics. In order to characterize the influence of these forces on mangroves, this work has used geomorphology and vegetation maps integrated with sedimentological and palynological data, radiocarbon dating, as well as δ13C, δ15N and C/N from sedimentary organic matter. The inter‐proxy analyses reveal an estuarine influence with mangrove development along the Ceará Mirim River, north‐eastern Brazil, since ~6920 cal yr bp, after the post‐glacial sea level rise. Relative sea level (RSL) has been stable during the middle and late Holocene. Mangrove establishment along this fluvial valley begins at about 6920 cal yr bp, caused by the sea‐level stabilization, an allogenic influence. However, after its establishment, wetland dynamics were mainly controlled by autogenic factors, related to channel migrations, instead of allogenic process. Some influence of sea‐level and climate changes on mangrove dynamics in this estuarine channel have been weakened by more intense tidal channels activities. Therefore, the expansion and contraction of mangrove areas along the estuary of the Ceará Mirim River since 6920 cal yr bp has been mainly influenced by channel dynamics that regulate the accretion and erosion of mangrove substrates. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Interpretation and Discussionmentioning

confidence: 92%

Allogenic and autogenic effects on mangrove dynamics from the Ceará Mirim River, north‐eastern Brazil, during the middle and late Holocene

Ribeiro

Batista

Cohen

et al. 2018

Earth Surf Processes Landf

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“…Not all changes in coastal vegetation may be attributed to autogenic processes. For instance, a previous publication (Fontes et al, ) based on a multi‐proxy analysis of one core (core PR07) located 23 km from the mouth of the Jucuruçu River (Figure B) revealed that the landscape was an estuarine system with tidal flats colonized by mangroves between ~7450 and ~5500 cal yr bp . During the past ~5500 cal yr bp , the mangroves shrank and herbaceous terrestrial vegetation expanded.…”

Section: Interpretation and Discussionmentioning

confidence: 98%

“…Considering core PR07 was sampled from a floodplain with herbaceous vegetation positioned about 4.5 ± 1 m above the relative sea‐level (RSL), this environmental change may signify a progressive rise in RSL, with the consequent marine incursion into the Jucuruçu River valley during the early to middle Holocene. Conversely, during the late Holocene, RSL fell, causing marine regression and the restriction of mangroves to the tidal flats near the modern coastline (Fontes et al, ).…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Late Holocene mangrove dynamics dominated by autogenic processes

Moraes

Fontes

Cohen

et al. 2017

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Generally, palaeoenvironmental interpretations consider only allogenic processes, when autogenic factors may have a strong influence on proxies of stratigraphic sequences. For instance, the Holocene history of the vegetation along the southern littoral of the State of Bahia in north-eastern Brazil is characterized by mangrove dynamics controlled by allogenic processes. However, over smaller timescales (~700 years), autogenic processes may have controlled vegetation dynamics and hence observed pollen distribution. This work proposes tidal channel dynamics as one of the main cause for changes in pollen assemblage along the studied stratigraphic profiles during the last centuries, based on sedimentology, pollen and elemental analysis (δ 13 C, δ 15 N and C/N) and radiocarbon dating of sedimentary organic matter from two cores sampled from an abandoned meander and a tidal flat at the mouth of the Jucuruçu River. One core was sampled from a mangrove formed during the past~550 cal yr BP. Another core recorded sediments in a várzea forest (swamp seasonally and permanently inundated by freshwater) located~2.7 km from the current shoreline, which displayed a maximum age of~680 cal yr BP. Two facies associations were identified: tidal channel (A) and tidal flat/oxbow lake (B). This work proposes allogenic processes as the main driving forces controlling the wetlands dynamics at the studied site during the Holocene. However, our data also reveal that part of the changes in vegetation over the last~700 years reflect tidal channels and tidal flats development, which represent autogenic processes. The change in timescale analysis from the Holocene to recent centuries may have weakened the influence of allogenic factors. However, this needs interpretation with reference to the spatial scale of the depositional environment as the larger the depositional system analyzed, the stronger the influence of autogenic processes on stratigraphic sequences over longer timescales.

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“…Mangrove forests appear to have back-stepped on the Great Barrier Reef, and the Belize barrier reef in the western Caribbean, where mangrove peats are preserved on the shelf beneath lagoonal sediments (Grindrod et al, 1999). Basal transgressive organic-rich peaty mangrove muds occur at the base of cores through coastal plains in southeast Asia and northern Australia (Woodroffe, 1993), as well as in eastern Brazil (Fontes et al, 2017). It will be shown below that about 8,000 years ago mangrove sedimentation was unable to keep pace with sea-level rise on open coasts, with mangrove forests back-stepping landwards, impinging on the hinterland ecosystems.…”

Section: Mangrove Responsementioning

confidence: 99%

“…Radiocarbon ages on mangrove material have provided much of the evidence for the trajectory and rates of sea-level change during the Holocene, both specifically in the Northern Territory (Woodroffe et al, 1987) and around other parts of Australia (Lewis et al, 2013), as well as elsewhere in the world (Toscano and Macintyre, 2003;Fontes et al, 2017). However, these sedimentary archives also provide insights into the way in which coastal wetlands have responded to sea-level change.…”

Section: Introductionmentioning

confidence: 99%

Mangrove response to sea level rise: palaeoecological insights from macrotidal systems in northern Australia

Woodroffe¹

2018

Mar. Freshwater Res.

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Accelerated sea-level rise threatens coastal wetlands; it is unclear whether sediment accretion beneath mangroves will be sufficient to keep pace. A conceptual framework, used to describe the response of reefs, can also be applied to mangroves, discriminating drowning or back-stepping with rapid rise from keep-up or catch-up under moderate rates. In macrotidal estuaries of northern Australia, different mangrove species grow across particular elevation ranges and accretion rates decrease with tidal elevation. Palaeoecological reconstructions, from drilling, dating and pollen analysis, record mangrove distribution over past millennia. Estuarine plains are underlain by a vertically continuous stratigraphy of muds, implying continuity of widespread 'big swamp' mangrove forests during decelerating stages of post-glacial sea-level rise c. 7000 years ago. In contrast, on higher-energy open coasts, mangroves back-stepped, but re-established as the shoreline prograded when the nearshore built to suitable elevation: a catch-up mode. These results demonstrate that mangrove response to sea-level rise has varied, determined by the availability of sediment and the oceanographic processes by which it is redistributed. How mangrove forests adjust in future will also vary as a function of local topography and sediment availability. Extensive plains flanking estuarine systems are particularly vulnerable to tidal creek extension and saline incursion under future higher sea levels. AbstractAccelerated sea-level rise threatens coastal wetlands; it is unclear whether sediment accretion beneath mangroves will be sufficient to keep pace. A conceptual framework, used to describe response of reefs, can also be applied to mangroves, discriminating drowning or backstepping with rapid rise from keep-up or catch-up under moderate rates. In macrotidal estuaries of northern Australia, different mangrove species grow across particular elevation ranges, and accretion rates decrease with tidal elevation. Paleo-ecological reconstructions, from drilling, dating and pollen analysis, record mangrove distribution over past millennia. Estuarine plains are underlain by a vertically-continuous stratigraphy of muds implying continuity of widespread 'big swamp' mangrove forests during decelerating stages of postglacial sea-level rise about 7,000 years ago. By contrast, on higher-energy open coasts, mangroves back-stepped, but re-established as the shoreline prograded when the nearshore built to suitable elevation: a catch-up mode. These results demonstrate that mangrove response to sea-level rise has varied, determined by availability of sediment and the oceanographic processes by which it is redistributed. How mangrove forests adjust in future will also vary as a function of local topography and sediment availability. Extensive plains flanking estuarine systems are particularly vulnerable to tidal creek extension and saline incursion under future higher sea levels.

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The Impacts of the Middle Holocene High Sea-Level Stand and Climatic Changes on Mangroves of the Jucuruçu River, Southern Bahia – Northeastern Brazil

Cited by 33 publications

References 49 publications

Allogenic and autogenic effects on mangrove dynamics from the Ceará Mirim River, north‐eastern Brazil, during the middle and late Holocene

Allogenic and autogenic effects on mangrove dynamics from the Ceará Mirim River, north‐eastern Brazil, during the middle and late Holocene

Late Holocene mangrove dynamics dominated by autogenic processes

Mangrove response to sea level rise: palaeoecological insights from macrotidal systems in northern Australia

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