earthworms and their balls of calcite · 2013-04-11 · osmoregulation . 11 ... production...
TRANSCRIPT
Earthworms and their balls of
calcite
Mark Hodson
2
Earthworm calcium carbonate
Caroline Layton, Kerrie Gwilliam (BSc)
Graham Langworthy, Anna Fraser (MSc)
Denise Lambkin, Emma Versteegh, Loredana Brinza
(PDRAs)
Stuart Black (Reading)
Trevor Piearce (Lancaster)
Matt Canti (English Heritage)
Martin Lee (Glasgow)
Paul Schofield (NHM)
Fred Mosselmans (Diamond)
Natural Environment Research Council, Science and
Technology Facilities Council
3
Earthworm calcium carbonate
4
Earthworm calcium carbonate
Earthworm calcium carbonate
“It may be doubted whether
there are many other
animals which have played
so important a part in the
history of the world, as
have these lowly organized
creatures."
Darwin, 1881
…several small, or two or
three larger, or a single very
large concretion of carbonate
of lime as much as 1.5 mm in
diameter…they are often found
in the gizzard, intestines and in
the castings of worms…
Darwin, 1881
Jack Kelly Clark, UCDavis
Gago-Duport et al. 2008
Canti and Piearce, 2003 after Darwin, 1881 and Robertson, 1936
Morgan, 1981
What is the function of granules?
Elimination of excess Ca
Neutralisation of gut pH
Fixing metabolic CO2
Osmoregulation
11
Earthworm calcium carbonate
What are they made of?
Metal mobility
C and Ca biogeochemistry
Dating potential
Palaeoindicators
12
What are they made of?
13
Earthworm calcium carbonate
14
What are they made of?
What are they made of?
(a) BSE image of a mixed calcite-ACC granule. (b) Corresponding EBSD
orientation contrast map. Calcite generates good Kikuchi patterns (inset) and crystal
orientations are colour coded. ACC lacks a Kikuchi pattern (inset), rendering it black
in the EBSD map.
What are they made of?
1/voxel CT images, University of Leeds
What are they made of?
18
Earthworm calcium carbonate
What are they made of?
Metal mobility
C and Ca biogeochemistry
Dating potential
Palaeoindicators
Metal mobility
Pb-rich soils: Pb in calcite, PbCO3
Sr-rich soils: Sr in calcite, vaterite
Zn-rich soils: Zn in calcite, Zn5(CO3)2(OH)6
20
Earthworm calcium carbonate
What are they made of?
Metal mobility
C and Ca biogeochemistry
Dating potential
Palaeoindicators
21
Production experiment
11 contrasting
soils
1 earthworm
per 300 g soil
27 days
22
Production experiment
23
Production experiment
24
Production experiment
25
Production experiment
pH related to
granule
production
No correlation
with organic
matter content,
bulk or
exchangeable
elements
r = 0.68, p < 0.01
0
0.5
1
1.5
2
2.5
3
4 5 6 7 8
soil pH
Gra
nu
le p
rod
uctio
n / m
g
CaC
O3 d
ay -
1
26
Production experiment
Average production rate =
0.75 mg calcite day-1
Range = 0 (0.05) to 4.3 mg calcite day-1
27
Production experiment
From Canti (2007) J Quat Sci 22
111-118
Putting granules into perspective
Earthworm density in pasture
Putting granules into perspective
Earthworm density in pasture 200 m-2
Putting granules into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Rate = 0.7 – 63 g m-2 a-1 (units also tonnes km-2 a-1)
Putting granules into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Rate = 0.7 – 63 g m-2 a-1 (units also tonnes km-2 a-1)
UK is
Putting granules into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Rate = 0.7 – 63 g m-2 a-1 (units also tonnes km-2 a-1)
UK is 242900 km2
Say 37% of land area is suitable for earthworms
Granule production = 65 x 103 – 5.7 x 106 tonnes CaCO3 a
-1
Putting granules into perspective
Granule production =
65 x 103 – 5.7 x 106 tonnes CaCO3 a-1
9 – 840 Olympic swimming pools
From This is Bristol
Putting granules into perspective
Granule production =
0.01 – 0.5 % UK C emissions
Up to c. 5 % of C emitted from soils
0.04 – 3 % of C fixed by temperate grassland
Putting the Ca into perspective
Granule production = 0.7 – 63 g CaCO3 m-2 a-1
Granule production = 0.28 – 25 g Ca m-2 a-1
Typical Ca fluxes in soils due to:
mineral weathering = 0.08 – 3 g Ca m-2 a-1
plant uptake = 0.05 – 1.5 g Ca m-2 a-1
runoff = 0.2 – 0.7 g Ca m-2 a-1
deposition = 0.2 - 0.4 g Ca m-2 a-1
Production experiment
pH related to
granule
production
Maybe not production but
production + dissolution
r = 0.68, p < 0.01
0
0.5
1
1.5
2
2.5
3
4 5 6 7 8
soil pH
Gra
nu
le p
rod
uctio
n / m
g
CaC
O3 d
ay -
1
Dissolution experiment 1
Three soils
Mix granules into
soil
Keep soil moist
Saturate soil,
collect leachate
Monitor granule
mass loss and solution chemistry
0
5
10
15
20
25
30
35
40
0 50 100 150 200
Hamble
Soil Science
St Albans
Day
% m
ass lo
ss o
f g
ran
ule
s f
ollo
win
g le
ach
ing
y = 0.19x - 6.5
r2 = 0.88, p < 0.01
y = 0.05x + 4.8
r2 = 0.77, p < 0.01
y = 2.1Ln(x) - 5.8
r2 = 0.62, p < 0.01
Dissolution experiment 1
39
Dissolution experiment 1
0
5
10
15
20
25
30
35
40
0 50 100 150 200
Hamble
Soil Science
St Albans
Day
% m
ass lo
ss o
f g
ran
ule
s f
ollo
win
g le
ach
ing
y = 0.19x - 6.5
r2 = 0.88, p < 0.01
y = 0.05x + 4.8
r2 = 0.77, p < 0.01
y = 2.1Ln(x) - 5.8
r2 = 0.62, p < 0.01
The SLIM model
Limestone
Ca free water
Ca flushed out of system
Dissolution rate increases
Reacts with acid
Ca released into solution
Dissolution slows
Ca moves onto
exchange sites
Dissolution
increases
41
Dissolution experiment 1
0
5
10
15
20
25
30
35
40
0 50 100 150 200
Hamble
Soil Science
St Albans
Day
% m
ass lo
ss o
f g
ran
ule
s f
ollo
win
g le
ach
ing
y = 0.19x - 6.5
r2 = 0.88, p < 0.01
y = 0.05x + 4.8
r2 = 0.77, p < 0.01
y = 2.1Ln(x) - 5.8
r2 = 0.62, p < 0.01
Balancing production and
dissolution
0
5
10
15
20
25
30
35
40
Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8
Gra
nu
les in s
oil
Putting the C into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Granules last for 5 years
Granules are located in top 10 cm of soil
Soil density is 900 kg m-3
Soil contains 5 % organic matter (50 % C)
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Granules last for 5 years
Granules are located in top 10 cm of soil
Soil density is 900 kg m-3
Soil contains 5 % organic matter (50 % C)
Granule carbon = 1% of total soil carbon
Putting the C into perspective
Putting the Ca into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Granules last for 5 years
Granules are located in top 10 cm of soil
Soil density is 900 kg m-3
Soil contains 1 % calcium
Soil contains 2500 mg kg-1 exchangeable calcium
Putting the Ca into perspective
Earthworm density in pasture 200 m-2
1 in 5 is granule producing
Granules last for 5 years
Granules are located in top 10 cm of soil
Soil density is 900 kg m-3
Soil contains 1 % calcium
Soil contains 2500 mg kg-1 exchangeable calcium
Granule calcium = 8 % of total soil calcium
Granule calcium = 33 % of exchangeable soil calcium
47
Earthworm calcium carbonate
What are they made of?
Metal mobility
C and Ca biogeochemistry
Dating potential
Palaeoindicators
Granules and climate change
What can the
granules tell us
about the climate
in the past?
The alternatives
Granules and climate change
I formed …
years ago
and the
temperature
was…
Dating
You gotta check this out, Stuart.
Vinnie’s over on the couch putting
the moves on Zelda Schwartz – but
he’s talkin’ to the wrong end
U
U/Th dating
234
230
92
90
U
Th
U/Th dating
Uranium-234
radioactive
decay chain
U/Th dating
time
am
ou
nt
thorium
uranium / thorium
uranium
U/Th dating
Silbury
Silbury
U-series isochron plot of multiple analyses of earthworm granules form Silbury hill. The
earliest date for this is circa 4400 B.P. which is consistent with the U-series age for the
carbonate granules, indicating they are contemporaneous with the soil formation.
230 Th/U age = 4.67 ± 0.44 ka
MSWD = 63, probability = 0.000
230Th / 232Th
238U / 232Th
Granules and climate change
I formed
1000 years
ago
and the
temperature
was…
Oxygen isotopes
Heavy water
Varying water composition
light heavy
Oxygen isotope thermometer
temperature
calcite
heavy oxygen
light oxygen
light
heavy
Establishing a thermometer
3 temperatures
x
3 waters
x
2 soils
Establishing a thermometer
10 ºC
16 ºC
20 ºC
oxygen isotope composition of water
oxyg
en
iso
top
e c
om
po
sitio
n o
f ca
lcite
light heavy
light
heavy
temperature
en
rich
me
nt in
he
avy o
xyg
en
Establishing a thermometer
temperature
calcite
heavy oxygen
light oxygen
light
heavy
temperature
calcite
heavy oxygen
light oxygen
light
heavy
Temperature equation
1000 ln α = 20.21 (103 T-1) - 38.58
α = (1000 + δ18OcVSMOW) / (1000 + δ18OwVSMOW)
66
Applying the thermometer
Applying the thermometer
Time travelling
Boxgrove 500,000 years ago