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| Titel |
A 150-year record of ancient DNA, lipid biomarkers and hydrogen isotopes,
tracing the microbial-planktonic community succession controlled by
(hydro)climatic variability in a tropical lake |
| VerfasserIn |
Rienk Smittenberg, Kweku Yamoah, Nolwenn Callac, Ernest Chi Fru, Akkaneewut Chabangborn, Jayne Rattray, Barbara Wohlfarth |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124190
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| Publikation (Nr.) |
 EGU/EGU2016-3578.pdf |
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| Zusammenfassung |
| We investigated the decadal variations in phytoplankton communities, and their response to
environmental and climatic conditions, from a ∼150 year long sedimentary archive of Lake
Nong Thale Prong (NTP), southern Thailand. We applied a combination of analyses:
lipid biomarkers, compound-specific hydrogen isotopes, bulk carbon and nitrogen
concentrations and isotopes, environmental SEM, and fossil DNA using qPCR
targeted to specific taxa. Past hydrological conditions were reconstructed using the
hydrogen isotopic composition of leaf wax n-alkanes. Temperatures were reconstructed
using the tetraether-based MBT/CBT index, measured using a new and efficient
reverse-phase HPLC-MS method. The climatological data compared well with
meteorological data from the last decades. Reconstructed drier and warmer conditions from
∼1857-1916 Common Era (CE) coincided with oligotrophic lake water conditions and
dominance of the green algae Botryococcus braunii - evidenced by a combination of both
fossil DNA and the occurrence of characteristic botryococcene lipids. A change
to higher silica (Si) input ∼1916 CE was related to increased rainfall and lower
temperatures concurring with an abrupt takeover by diatom blooms lasting for 50
years - as evidenced by ancient DNA, characteristic highly branched isoprenoid
lipids, and SEM. From the 1970s onwards, more eutrophic conditions prevailed,
and these were likely caused by increased levels of anthropogenic phosphate (P),
aided by stronger lake stratification caused by dryer and warmer conditions. The
eutrophic conditions led to increased primary productivity in the lake, consisting
again of a Botryococcus sp., although this time not producing botryococcene lipids.
Moreover, Cyanobacteria became dominant – again evidenced by ancient DNA and
the characteristic C19 alkane. Throughout the record, stratification and primary
production could be linked to the intensity of methane cycling, by targeting and
quantifying the mcrA gene that is used both by methanogens and anaerobic methane
oxidizers. Our results show that a combined multi-proxy approach, especially the
combination of targeted qPCR and lipid biomarker analysis, allows a highly robust
reconstruction of past microbial ecosystem responses to climatic and environmental changes. |
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