A heterocyte glycolipid-based calibration to reconstruct past continental climate change

Bauersachs, Thorsten; Russell, James M.; Evans, Thomas W.; Schwalb, Antje; Schwark, Lorenz

doi:10.1038/s41467-021-22739-3

Cited by 8 publications

(11 citation statements)

References 68 publications

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“…S13 ) holds in the MH, the reduced seasonality inferred from our coral records would imply warmer mean MH WP SSTs in the WIO. This is confirmed by the sediment records from the WIO and East African lakes that show substantial, sustained warming between 8 and 5 ka BP 15 , 16 , 30 , 32 . Reduced seasonality coupled with warmer mean SSTs would imply greater warming in the cold season, e.g.…”

Section: Discussionsupporting

confidence: 61%

“…This suggests that a warmer Indian Ocean will have a more uniform SST distribution and a reduced SST seasonality. We therefore believe that the reduced seasonality observed in our coral Sr/Ca records can be attributed to warmer mean temperatures in the WIO and equatorial East Africa between 8 and 5 ka BP, as inferred from sediment records covering the MH 15,16,30,32 . Furthermore, we propose that rapid warming in boreal fall driven by the fall insolation maximum raised SSTs at the start of the warm season to the upper limit of Indian Ocean SSTs under MH climatic conditions.…”

Section: Mid-holocene Temperatures In the Western Indian Ocean And Ea...mentioning

confidence: 67%

“…sediment records indicate warmer mean MH WP temperatures in equatorial East Africa between 8 and 5 ka BP 15,16,30,31 . A temperature reconstruction derived from a marine sediment core taken off the coast of Tanzania also indicates warmer SSTs (0.79 ± 0.22 °C) in the time interval between 7.8 and 5.6 ka BP 32,33 .…”

Section: Mid-holocene Temperatures In the Western Indian Ocean And Ea...mentioning

confidence: 98%

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Mid-Holocene expansion of the Indian Ocean warm pool documented in coral Sr/Ca records from Kenya

Leupold

Pfeiffer

Watanabe

et al. 2023

Sci Rep

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Proxy reconstructions suggest that mid-Holocene East African temperatures were warmer than today between 8 and 5 ka BP, but climate models cannot replicate this warming. Precessional forcing caused a shift of maximum insolation from boreal spring to fall in the mid-Holocene, which may have favored intense warming at the start of the warm season. Here, we use three Porites corals from Kenya that represent time windows from 6.55 to 5.87 ka BP to reconstruct past sea surface temperature (SST) seasonality from coral Sr/Ca ratios in the western Indian Ocean during the mid-Holocene. Although the Indian monsoon was reportedly stronger in the mid-Holocene, which should have amplified the seasonal cycle of SST in the western Indian Ocean, the corals suggest reduced seasonality (mean 3.2 °C) compared to the modern record (mean 4.3 °C). Warming in austral spring is followed by a prolonged period of warm SSTs, suggesting that an upper limit of tropical SSTs under mid-Holocene conditions was reached at the start of the warm season, and SSTs then remained stable. Similar changes are seen at the Seychelles. Bootstrap estimates suggest a reduction in SST seasonality of 1.3 ± 0.22 °C at Kenya and 1.7 ± 0.32 °C at the Seychelles. SST seasonality at Kenya corresponds to present-day SST seasonality at 55° E–60° E, while SST seasonality at the Seychelles corresponds to present day SST seasonality at ~ 65° E. This implies a significant westward expansion of the Indian Ocean warm pool. Furthermore, the coral data suggests that SST seasonality deviates from seasonal changes in orbital insolation due to ocean–atmosphere interactions.

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Section: Discussionsupporting

confidence: 61%

Section: Mid-holocene Temperatures In the Western Indian Ocean And Ea...mentioning

confidence: 67%

Section: Mid-holocene Temperatures In the Western Indian Ocean And Ea...mentioning

confidence: 98%

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Mid-Holocene expansion of the Indian Ocean warm pool documented in coral Sr/Ca records from Kenya

Leupold

Pfeiffer

Watanabe

et al. 2023

Sci Rep

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“…Similar observations have been made in cultured cyanobacteria, in which the proportion of HG diols has been found to increase with growth temperature (Bauersachs et al, 2014). The HDI 26 , a HG based proxy to reconstruct surface water temperatures (SWT) in lacustrine environments (Bauersachs et al, 2015(Bauersachs et al, , 2021, revealed substantial variations between the Antarctic meltwater ponds (HDI 26 : 0.24 -0.68, SWT: -6 -11 • C) and lakes (HDI 26 : 0.32 -0.54, SWT: -5 -5 • C) compared to the (sub)tropical mats (HDI 26 : 0.90 -0.97, SWT: 21 -23 • C). HG distribution patterns and the HDI 26 thus express a significant climate-driven component, which may compensate for varying rates of oxygen diffusion into the heterocyte with temperature variation and provide cyanobacteria with an anaerobic microenvironment to allow for biological N 2 fixation (Bauersachs et al, 2009a).…”

Section: Temperature Controls On Heterocyte Glycolipid and Bacterioho...supporting

confidence: 52%

Lipid Biomarkers From Microbial Mats on the McMurdo Ice Shelf, Antarctica: Signatures for Life in the Cryosphere

et al. 2022

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Persistent cold temperatures, a paucity of nutrients, freeze-thaw cycles, and the strongly seasonal light regime make Antarctica one of Earth’s least hospitable surface environments for complex life. Cyanobacteria, however, are well-adapted to such conditions and are often the dominant primary producers in Antarctic inland water environments. In particular, the network of meltwater ponds on the ‘dirty ice’ of the McMurdo Ice Shelf is an ecosystem with extensive cyanobacteria-dominated microbial mat accumulations. This study investigated intact polar lipids (IPLs), heterocyte glycolipids (HGs), and bacteriohopanepolyols (BHPs) in combination with 16S and 18S rRNA gene diversity in microbial mats of twelve ponds in this unique polar ecosystem. To constrain the effects of nutrient availability, temperature and freeze-thaw cycles on the lipid membrane composition, lipids were compared to stromatolite-forming cyanobacterial mats from ice-covered lakes in the McMurdo Dry Valleys as well as from (sub)tropical regions and hot springs. The 16S rRNA gene compositions of the McMurdo Ice Shelf mats confirm the dominance of Cyanobacteria and Proteobacteria while the 18S rRNA gene composition indicates the presence of Ochrophyta, Chlorophyta, Ciliophora, and other microfauna. IPL analyses revealed a predominantly bacterial community in the meltwater ponds, with archaeal lipids being barely detectable. IPLs are dominated by glycolipids and phospholipids, followed by aminolipids. The high abundance of sugar-bound lipids accords with a predominance of cyanobacterial primary producers. The phosphate-limited samples from the (sub)tropical, hot spring, and Lake Vanda sites revealed a higher abundance of aminolipids compared to those of the nitrogen-limited meltwater ponds, affirming the direct affects that N and P availability have on IPL compositions. The high abundance of polyunsaturated IPLs in the Antarctic microbial mats suggests that these lipids provide an important mechanism to maintain membrane fluidity in cold environments. High abundances of HG keto-ols and HG keto-diols, produced by heterocytous cyanobacteria, further support these findings and reveal a unique distribution compared to those from warmer climates.

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“…We detected heterocyte glycolipids HG 26 diols and keto-ols as well as HG 28 diols and keto-ols, organic molecules consisting of a sugar functionality glycosidically bound to long carbon chains with hydroxy and/or ketone functionalities, which are exclusively synthesized by N 2 -fixing heterocytous cyanobacteria ( 16 ) that are common in freshwater. Application of the HDI 26 (heterocyte diol index of 26 carbon atoms) lipid paleothermometer ( 17 ) using a previously established modern lake surface sediment calibration ( 18 ) yielded a reconstructed summer water temperature of 18.7°C (with a calibration error of ±1.7°C) for the depositional environment.…”

Section: Resultsmentioning

confidence: 99%

A large-scale transcontinental river system crossed West Antarctica during the Eocene

Zundel,

Spiegel,

Mark

et al. 2024

Sci. Adv.

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Extensive ice coverage largely prevents investigations of Antarctica’s unglaciated past. Knowledge about environmental and tectonic development before large-scale glaciation, however, is important for understanding the transition into the modern icehouse world. We report geochronological and sedimentological data from a drill core from the Amundsen Sea shelf, providing insights into tectonic and topographic conditions during the Eocene (~44 to 34 million years ago), shortly before major ice sheet buildup. Our findings reveal the Eocene as a transition period from >40 million years of relative tectonic quiescence toward reactivation of the West Antarctic Rift System, coinciding with incipient volcanism, rise of the Transantarctic Mountains, and renewed sedimentation under temperate climate conditions. The recovered sediments were deposited in a coastal-estuarine swamp environment at the outlet of a >1500-km-long transcontinental river system, draining from the rising Transantarctic Mountains into the Amundsen Sea. Much of West Antarctica hence lied above sea level, but low topographic relief combined with low elevation inhibited widespread ice sheet formation.

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A heterocyte glycolipid-based calibration to reconstruct past continental climate change

Cited by 8 publications

References 68 publications

Mid-Holocene expansion of the Indian Ocean warm pool documented in coral Sr/Ca records from Kenya

Mid-Holocene expansion of the Indian Ocean warm pool documented in coral Sr/Ca records from Kenya

Lipid Biomarkers From Microbial Mats on the McMurdo Ice Shelf, Antarctica: Signatures for Life in the Cryosphere

A large-scale transcontinental river system crossed West Antarctica during the Eocene

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