earthworms and their balls of calcite · 2013-04-11 · osmoregulation . 11 ... production...

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