Abstract.
Membrane
lipids
of
ammonia-oxidizing
Thaumarchaeota,
in
particular
isoprenoidal
glycerol
dialkyl
tetraethers
(isoGDGTs)
and
hydroxylated
isoGDGTs
(OH-isoGDGTs),
have
been
used
as
biomarkers
proxies
various
environments.
Controlled
growth
experiments
to
investigate
the
factors
that
influence
composition
these
lipids,
on
how
affect
TEX86
temperature
proxy,
which
is
based
degree
cyclization
isoGDGTs.
Recently,
ring
index
OH-isoGDGTs
(RI-OH'),
patterns
OH-isoGDGTs,
relative
abundance
(%OH)
emerged
promising
proxies.
Here,
we
examined
impact
phase
distribution
their
associated
using
cultures
two
thaumarchaeotal
strains.
Analysis
core
headgroup
compositions
showed
no
consistent
differences
between
mid-exponential
stationary
phases
for
both
Nitrosopumilus
adriaticus
NF5
shows
a
substantially
higher
(~49
%)
compared
piranensis
D3C
(~5
also
observations
reported
marine
environment
(<
17
%),
indicating
large
variations
%OH
values
even
among
closely
related
species.
Unlike
environment,
did
not
decrease
with
increasing
temperatures
either
strains,
possibly
reflecting
threshold
below
15
°C
this
response
natural
environment.
The
RI-OH'
increases
similar
regular
abundances
headgroups
varied
strains
respond
changes
nor
phase.
calculated
from
intact
polar
different
revealed
distinct
previously
observed
Together,
our
findings
suggest
has
pronounced
effect
contrast
mainly
exhibits
interspecies
variability.
Geophysical Research Letters,
Journal Year:
2024,
Volume and Issue:
51(6)
Published: March 18, 2024
Abstract
Hydroxylated
isoprenoid
GDGTs
(OH‐GDGTs)
have
emerged
as
a
novel
tool
for
reconstructing
sea
surface
temperatures.
However,
when
using
marine
OH‐GDGT
calibration
in
lacustrine
settings,
it
leads
to
significant
overestimation
of
temperatures,
emphasizing
the
necessity
thorough
examination
OH‐GDGTs
lakes.
Here,
we
investigated
distributions
sediments
from
65
lakes
West
China
and
compiled
published
Asian
lake
global
data
sets.
Among
all
GDGT‐based
indices,
RI‐OH
showed
strongest
correlation
with
temperature
across
The
value
was
higher
than
sediments,
likely
due
differences
composition
Group
1.1a
thaumarchaeotal
species
between
two
settings.
first
developed
addressed
issue
applied
both
water
column
sediment
core,
highlighting
potential
new
terrestrial
paleothermometer.
Organic Geochemistry,
Journal Year:
2024,
Volume and Issue:
194, P. 104780 - 104780
Published: April 9, 2024
Hydroxylated
Isoprenoidal
Glycerol
Dialkyl
Tetraethers
(OH-isoGDGTs)
have
recently
been
utilized
as
paleothermometers
in
the
marine
environment.
However,
their
ability
to
reconstruct
temperature
Mediterranean
and
Red
Sea
has
not
adequately
investigated.
Previous
research
shown
that
archaeal
communities
inhabiting
different
water
depths
these
basins
exert
a
substantial
influence
on
regular
isoGDGT
distributions
associated
proxies
such
TEX86.
impact
of
archaea
OH-isoGDGTs
corresponding
remains
unclear.
In
this
study,
we
examined
distribution
(%OH,
RI-OH,
RI-OH′
TEX86OH)
surface
sediments
Sea.
We
observe
strong
correlations
between
fractional
abundances
OH-isoGDGTs,
relative
all
isoGDGTs
depth
which
suggests
deep-water
lower
OH-isoGDGT
abundance
compared
shallow
communities.
As
result,
%OH
TEX86OH
are
strongly
correlated
with
depth,
particularly
at
<500
m
Interestingly,
RI-OH
show
no
correlation
Instead,
they
correlate
more
satellite-derived
sea
other
isoGDGT-based
proxies,
indicating
potential
paleothermometers.
Finally,
unlike
TEX86
TEX86OH,
%OH,
do
exhibit
distinct
'Red
cluster'
display
comparable
values
from
tropical
oceans.
Further
sedimentary
broader
geographical
coverage
within
enrichment
cultures
needed
confirm
observations.
Frontiers in Earth Science,
Journal Year:
2024,
Volume and Issue:
12
Published: Aug. 30, 2024
Archaeal
isoprenoid
glycerol
dibiphytanyl
tetraethers
(GDGTs)
preserved
in
sediments
are
popular
tools
for
the
reconstruction
of
past
temperature
global
ocean.
Whereas
most
common
GDGTs
have
been
well
studied
through
environmental
and
culture
studies,
their
hydroxylated
version
(OH-GDGTs)
is
just
emerging
as
a
new
proxy.
Some
empirical
evidence
suggests
that
distribution
OH-GDGTs
may
capture
sea
surface
variability.
However,
effects
additional
factors
on
OH-GDGT
distributions
not
rigorously
tested,
salinity,
ice,
seasonality,
terrestrial
input,
water
depth
be
some
settings.
In
this
study,
we
analyzed
modern
Holocene
marine
sediment
from
North
Iceland
Shelf.
By
statistically
comparing
biomarker
datasets
against
collection
instrumental
paleoceanographic
records,
separated
which
variables
controlling
OH-GDGT-derived
proxies
around
Iceland.
contrast
to
prevailing
theory,
found
nitrate
concentrations
water-column
stratification
best
correlated
distributions,
temperature.
These
results
hold
important
implications
application
high-latitude
oceans,
particularly
highly
stratified
locations,
future
studies
biological
sources
functionality
these
lipids.
Given
current
complexity
proxy
interpretation,
urge
caution
tool
paleotemperature
reconstructions.
