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Long-term retrospection on mangrove development using sediment cores and pollen analysis: a review
Citation
Ellison, JC, Long-term retrospection on mangrove development using sediment cores and pollen analysis: a review, Aquatic Botany, 89, (2) pp. 93-104. ISSN 0304-3770 (2008) [Refereed Article]
DOI: doi:10.1016/j.aquabot.2008.02.007
Abstract
Mangroves are biogenic systems that accumulate sedimentary sequences, where cores can provide records of mangrove species variation in
distribution with past climate change and sea-level change. Fossil evidence used for palaeoecological reconstruction is based on organic remains that
preserve identifying features so that they can be identified to generic levels at least. This includesmacrofossils such as fruit, flowers, wood or leaves, or
microfossils particularly pollen. Anaerobic conditions in mangrove sediment allow the long-term preservation of these fossil records. Fossil pollen
from core samples is concentrated formicroscopic examination by use of standard chemical treatments, but refinements of these are necessary for the
peculiarities ofmangrove peat. Pollen diagrams are expressed in concentrations, ormore usefully in mangrove environments as proportions relative to
others, as this has been shown to demonstrate the depositional environment actually underneath the mangrove forest. Radiocarbon dating of
sedimentary sequences is used to date palaeoecological successions shown by fossil sequences, or long-term sedimentation rates. Sediment accretion
in the last 50200 years can been analysed better using Cs137 and Pb210 analyses. From pollen and macrofossils mostly recovered from stratigraphic
cores of sedimentary rock and more recent sediment, the evolution and dispersal ofmangroves through geological time has been reconstructed.While
reconstruction of actual temperatures in these earlier records is associative to the fossil types present, it is apparent that mangroves have always been
tropical species, extending to higher latitudes only during global warm periods. Many sedimentary records show mangroves deeper than the present
lower limit of mangrove growth at mean sea-level. These indicate sea-level rising over time, and mangroves keeping pace with rising sea-level.
Stratigraphic dating shows accretion rates of 1 mm a1 for low island locations, and up to 1.5 mm a1 in high islands/continental margins.
Sedimentary records can also show die-off of mangroves with more rapid sea-level rise and replacement by open water during rising sea-level,
landward retreat of mangrove zones, or replacement of mangroves by freshwater forest with sedimentary infill. The causes of mangrove community
changes identified in the palaeoecological record can only be inferred by comparison with ecological studies in the modern environment, the link
between the two that may be possible through long-term mangrove monitoring being poorly established.
Item Details
Item Type: | Refereed Article |
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Keywords: | Stratigraphy; Pollen analysis; Palaeoecology; Macrofossil; Sedimentation; Palynology |
Research Division: | Earth Sciences |
Research Group: | Physical geography and environmental geoscience |
Research Field: | Physical geography and environmental geoscience not elsewhere classified |
Objective Division: | Environmental Management |
Objective Group: | Coastal and estuarine systems and management |
Objective Field: | Coastal or estuarine biodiversity |
UTAS Author: | Ellison, JC (Associate Professor Joanna Ellison) |
ID Code: | 55243 |
Year Published: | 2008 |
Web of Science® Times Cited: | 100 |
Deposited By: | Geography and Environmental Studies |
Deposited On: | 2009-03-06 |
Last Modified: | 2009-03-19 |
Downloads: | 0 |
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