bioRxiv (Cold Spring Harbor Laboratory),
Journal Year:
2025,
Volume and Issue:
unknown
Published: May 13, 2025
Abstract
Prochlorococcus
is
a
diverse
and
widespread
cyanobacterium
with
significant
contributions
to
the
marine
nitrogen
carbon
cycles.
Some
reduce
divert
up
20-30%
of
nitrate
that
they
take
external
pools
nitrite.
Given
nitrite
central
intermediate
cycle
highly
abundant
in
nitrogen-limited
waters,
our
goal
was
advance
understanding
cycling
context
limitation.
Here
we
observe
nitrate-limited
have
cell-specific
production
rates
are
approximately
magnitude
higher
than
nitrogen-replete
when
challenged
pulse
nitrate.
Nitrite
unchanged
or
depressed
during
light
cold
shocks,
suggesting
not
used
as
an
alternative
electron
acceptor
mitigate
impacts
excess
photochemically
generated
electrons.
These
results
suggest
regions
where
phytoplankton
growth
limited
by
nitrogen,
cells
could
be
primed
transform
substantial
quantities
into
extracellular
episodic
upwellings
nitrate-rich
water.
important
cycle,
these
ramifications
for
open
ocean
ecosystems.
Geophysical Research Letters,
Journal Year:
2022,
Volume and Issue:
49(21)
Published: Oct. 4, 2022
Abstract
Chromium
stable
isotope
composition
(δ
53
Cr)
is
a
promising
tracer
for
redox
conditions
throughout
Earth's
history;
however,
the
geochemical
controls
of
δ
Cr
have
not
been
assessed
in
modern
redox‐stratified
basins.
We
present
new
chromium
(Cr)
concentration
and
data
dissolved,
sinking
particulate,
sediment
samples
from
Lake
Cadagno
(Switzerland),
Proterozoic
ocean
analog.
These
demonstrate
fractionation
during
incomplete
(non‐quantitative)
reduction
removal
above
chemocline,
driving
isotopically
light
accumulation
euxinic
deep
waters.
Sediment
authigenic
distinct
overlying
waters
but
comparable
to
average
continental
crust.
New
published
other
basins
show
analogous
patterns.
This
challenges
assumptions
paleoredox
applications
that
quantitative
limits
fractionation.
Instead,
non‐quantitative
leads
sedimentary
records
offset
reflecting
high
oxidative
weathering.
Geochimica et Cosmochimica Acta,
Journal Year:
2023,
Volume and Issue:
360, P. 36 - 56
Published: Sept. 7, 2023
It
has
been
estimated
that
the
acid
mine
drainage
(AMD)
impacted
Odiel
river
basin
in
southern
Spain
supplies
0.37%
and
15%
of
global
riverine
fluxes
Cd
Zn
to
oceans,
respectively
(Sarmiento
et
al.,
2009).
However,
behaviour
Ria
Huelva
estuary,
which
connects
Tinto
watersheds
with
Gulf
Cadiz,
yet
be
fully
investigated.
Furthermore,
very
few
studies
have
investigated
isotope
estuaries
worldwide.
This
study
presents
concentrations
isotopic
compositions
for
estuary
surrounding
watersheds,
sampled
2017
2019.
Sulfide-rich
rock
samples
extracted
from
three
mines
yield
range
–0.14‰
+0.07‰
(n
=
4)
δ114Cd
–0.01‰
+0.29‰
δ66Zn.
a
uniform
signal
about
+0.02‰
+0.17‰
indicates
tracing
individual
mining
regions
using
isotopes
is
challenging.
Limited
variability
was
observed
dissolved
values
throughout
watershed,
including
AMD,
mean
value
±0.00
±
0.13‰
25,
2
SD;
excludes
one
AMD
outlier,
at
+0.48‰),
both
2019
data.
By
contrast,
δ66Zn
ranged
–0.12‰
+0.35‰
28)
same
geographical
temporal
scope.
In
May
2017,
large
spill
an
abandoned
mine,
La
Zarza,
resulted
drastic
increase
trace
metals
reaching
compared
2019,
but
no
impact
this
on
or
observed.
coincided
high
pH
(up
8.8)
chloride
(2.73%),
may
reflect
alkaline
anthropogenic
input
active
neighbouring
industrial
complex.
Overall,
are
largely
consistent
conservative
mixing
behaviour.
non-conservative,
removal
49
97%
during
period
associated
relatively
small
shift
lighter
compositions.
Removal
particulate
phase
therefore
attenuates
indicating
previously
were
overestimated.
Nevertheless,
variable
generally
light
compositions,
coupled
metal
concentrations,
suggest
useful
tracers
regionally
averaged
inputs
Cadiz
beyond.
Journal of Geophysical Research Oceans,
Journal Year:
2022,
Volume and Issue:
127(4)
Published: March 22, 2022
Early
studies
revealed
relationships
between
barium
(Ba),
particulate
organic
carbon
and
silicate,
suggesting
applications
for
Ba
as
a
paleoproductivity
tracer
of
modern
ocean
circulation.
Geochimica et Cosmochimica Acta,
Journal Year:
2023,
Volume and Issue:
348, P. 239 - 257
Published: March 6, 2023
In
the
marine
sediment
record,
concentrations
and
isotope
ratios
of
chromium
(Cr)
can
be
used
to
reconstruct
ocean
biogeochemical
conditions.
These
reconstructions
rely
on
a
detailed
understanding
chemical
pathways
that
Cr
undergoes
as
it
is
transferred
from
water
column
record.
We
examined
in
pore
fluids
sediments
six
continental
margin
sites,
which
grouped
into
two
basic
environments:
(1)
sites
where
are
oxygenated
rich
solid
phase
Mn
(herein
termed
oxic),
(2)
organic
C
(Corg)-rich
oxygen
depleted
(anoxic).
found
lower
(maximum
12
nM
124
ppm
phase)
at
oxic
compared
with
anoxic
77
184
ppm).
Our
findings
confirm
previously
published
interpretations
dissolved
(Brumsack
Gieskes,
1983;
Shaw
et
al.,
1990).
surface
sediments,
particulate
Cr(III)
oxidised
by
oxides,
leads
elevated
co-occurring
same
depth
sediment.
Under
these
oxidising
conditions,
down-core
contain
relatively
low
solid-phase
concentrations.
speciation
reveals
most
fluid
Cr(VI)
state.
At
site
oxide-rich
rest
below
an
column,
oxidative
loss
bottom
lowest
estimated
burial
efficiency
here.
Corg-rich
both
phases
high
concentrations,
40–80%
present
Cr(III).
This
enrichment
appears
tightly
linked
presence
total
carbon
(TOC)
content
scavenging
(organic)
particles
column.
Combined,
data
highlight
strong
dependence
sedimentary
redox
conditions
well
biological
productivity.
Based
modern
we
propose
compositions
authigenic
fraction
may
record
combination
productivity
If
confirmed
analyses,
will
add
support
for
notion
serve
proxy
sedimentological
Thus,
careful
assessment
impact
matter
required
records.
