Assessing the use of mangrove pollen as a quantitative sea‐level indicator on Mahé, Seychelles

Abstract

We investigated the potential of mangrove pollen from Mahé, Seychelles, to improve existing metre‐scale Late Holocene sediment‐based sea‐level reconstructions. Mangrove species at two mangrove sites are broadly zoned according to elevation within the tidal frame. Modern pollen rain from traps deployed for 1 year generally have a poor relationship with modern vegetation, and relatively low pollen production rates. Pollen from mangrove species that live in narrow elevation zones (e.g. Avicennia marina) are poorly represented in modern pollen rain, while pollen from mangrove species that live across a larger elevational range (e.g. Rhizophora mucronata) are relatively well represented. Pollen was found in extremely low concentrations in mangrove surface and core sediments, which inhibited further study into pollen transport and preservation. The results from this modern study demonstrate that utilizing mangrove pollen would not decrease existing metre‐scale vertical uncertainties in Late Holocene sea‐level reconstructions in the Seychelles. We suggest that this approach may still be successful in other locations if mangrove vegetation is (i) zoned at a more extensive lateral scale and (ii) is closely associated with modern pollen rain and surface sediments, and (iii) sedimentological conditions promote the preservation of pollen in fossil sequences.

Sea level rise and climate change acting as interactive stressors on development and dynamics of tropical peatlands in coastal Sumatra and South Borneo since the Last Glacial Maximum

“…Similarly, a mangrove seaward migration was also recorded in the Kampar core after 4800 cal year BP, as indicated by less mangrove taxa and a higher proportion of taxa commonly growing landward of a mangrove forest (Figure 2b; Table 1) (Engelhart et al, 2007; Sefton & Woodroffe, 2021; Sosef et al, 1998; Woodroffe et al, 2016). The disappearance of foraminifera test‐lining from the Kampar record afterwards also indicates that the site no longer received marine water input (Mathison & Chmura, 1995), which further confirms that the sea level was regressing at that time (Bird et al, 2007, 2010).…”

GEORGIA: A Graph Neural Network Based EmulatOR for Glacial Isostatic Adjustment

“…Milne and Mitrovica (2008) provide a series of BSL maps at different time slices, based on GIA modeling results that use two ice histories (Bassett et al., 2005; Peltier, 2004), each paired with 162 plausible sets of Earth parameters. These maps have been used by the field community to target locations that approximate BSL during different parts of the deglacial period (e.g., Sefton, 2020; Woodroffe et al., 2015).…”

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

“…(Tomlinson, 2016). Despite the presence of Rhizophora mucronata and other terrestrial pollen-producers in the Grand Anse mangrove environment and immediate surroundings, poor pollen preservation in sediments contribute to pollen concentrations too low for radiocarbon measurements (Sefton and Woodroffe, 2021). As for the bulk, organic and macrofossil samples discussed above, the transport of pollen to the sedimentary sequence and its preservation potential may be affected by low rates of burial and potentially high rates of degradation in surface sediments at Grand Anse.…”