Sediment Fe:PO 4 ratio as a diagnostic and prognostic tool for the restoration of

aquatic biodiversity in fens

Jeroen Geurts, Leon Lamers, Fons Smolders, Jos Verhoeven & Jan Roelofs

Eutrophication and pollution

Eutrophication of Dutch peat lakesDutch peat lakesEutrophicationEutrophication of Dutch peat lakesof Dutch peat lakes

External loads decreased due to P-stripping and decrease of P in Rhine water

However, HCO3

-, SO42- and Cl - still high:

eutrophication of fen waters increased!

In a major part of The Netherlands allochtonous river Rhine water is used to counteract desiccation problems

This leads to strong eutrophication

Eutrophication and pollution

Internal eutrophication:Internal eutrophication:

Eutrophication by Eutrophication by increased mobilization of increased mobilization of nutrients nutrients in the sedimentin the sediment(particularly shallow peat (particularly shallow peat lakes)lakes)

Eutrophication and pollution

Rooting macrophytes

Iron phosphate

Iron

Iron sulphides

Clear water

Aerobic conditions

ShallowShallow fenfen waterswaters / / peatpeat lakeslakes: : undisturbedundisturbed

Lemna sp. & blue algae

Toxic sulphide No rootingmacrophytes

Phosphate mobilisation

Phosphate

Iron phosphate

Anoxic water layerTurbid water

Sulphate

Toxic sulphide Anoxic soil

Iron sulphide

Nutrients and Sulphate

Eutrophication and pollution

ShallowShallow fenfen waterswaters / / peatpeat lakeslakes: : eutrophiedeutrophied & & pollutedpolluted

Hypothesis

Sediment (pore water) data� less fluctuating in time – less frequent sampling needed� indicators of biogeochemical processes in the sediment,

especially Fe-S-P interactions (shallow lakes; 1-2 m)

� “early warning system” for future changes in water qualityAND� prognosis of biodiversity response after restoration measures

Water quality data� used for predicting restoration potential of aquatic

macrophyte diversity� strong temporal fluctuations (seasons, growth of plants &

algae)

Methods

145 fen waters in 17 different areas in the Netherlands, Ireland and Poland:

� Surface water and pore water samples� Vegetation relevées � threatened species� Sediment samples from 79 locations� Correlations and other statistical methods

Surface water quality and aquatic vegetation

� Highest biodiversity at lowest PO4 concentrations� Red List species � stronger related to surface water

chemistry than others � Red List species present � lower turbidity, pH, SO4, PO4

and NH4 concentrations

0

10

20

30

40

50

60

70

80

90

≤ 0.5 0 .5 - 2 2 -6 ≥ 6surface wa ter P O 4

spe

cies

cov

er (

%)

Helophytes RL

Helophytes

A q. macrophytes RLA q. macrophytes

0

1

2

3

4

5

6

7

≤ 0 .5 0 .5 - 2 2-6 ≥ 6surface wa te r PO 4

num

ber o

f spe

cies

Helophytes RL

Helophytes

A q. macrophytes RLA q. macrophytes

0

50

100

150

200

250

300

0.01 0.1 1 10 100surface water PO 4 (µmo l/l)

Cov

er (%

)

Red List speci es -.391***other species .012 ns

0

2

4

6

8

10

12

14

16

18

20

0.01 0.1 1 10 100su rface water PO 4 (µmo l/l)

Num

ber o

f spe

cies

Red List speci es -.365***other species -.112 ns

Sediment and surface water quality

� PO4 mobilization trigger at pore water PO4 > 6.5 µmol L-1

� Thresholds for pore water Fe:PO4 < 3.5 mol mol-1 and for total sediment Fe:P < 10 mol mol-1

� Low ratios / PO4 mobilization ↔ SO4 pollution / sulphide production

0

20

40

60

80

100

120

0 10 20 30 40 50t otal sed imen t F e:P (mol:mol)

pore

wat

er P

O4 (µ

mol

/l)

0

5

10

15

20

25

30

35

surf

ace

wat

er P

O4 (

µmol

/l)

pore water -.147 ns surface water -.363**

0

5

10

15

20

25

30

35

0.01 0.1 1 10 100 1000p ore w ater PO 4 (µmol/l)

surf

ace

wat

er P

O4 (µ

mo

l/l)

Fe:PO4 < 3,5Fe:PO4 > 3,5r = .666***

0

20

40

60

80

100

120

0.01 0.1 1 10 100 1000 10000 1E+05po re w ater Fe:PO 4 (mo l:mo l)

pore

wat

er P

O4 (µ

mol

/l)

0

5

10

15

20

25

30

35

surf

ace

wat

er P

O4 (µ

mol

/l)

porewater -.800***surface water -.612***

0

20

40

60

80

100

120

0.01 0.1 1 10 100 1000 10000po re w ater sulph id e (µm ol/l)

pore

wat

er P

O4 (µ

mo

l/l)

pore water .504***Fe:PO 4 < 3,5Fe:PO 4 > 3,5

Smolders et al. 2001

Sediment quality in relation to aquatic vegetation

� Fe:PO4 ratios � only correlation with Red List species� Number of species increased at Fe:PO4 > 1� Abundance increased at Fe:PO4 > 10� Red List species � more sensitive to toxic sulphide and ammonium

0

50

100

150

200

250

300

0.01 0.1 1 10 100 1000 10000 100000pore water Fe:PO 4 (m ol:m ol)

Co

ver (

%)

Red Lis t s pecies.324***other s pec ies -.171*

0

2

4

6

8

10

12

14

16

18

20

0.01 0.1 1 10 100 1000 10000 100000pore water Fe:PO 4 (m ol:mo l)

Nu

mbe

r of

spe

cies

Red Lis t s pec ies .309***other spec ies .148*

0

50

100

150

200

250

300

0.1 1 10 100 1000 10000pore water sulph id e (µmol/l)

Co

ver (

%)

Red List species -.293***other species .008 ns

0

2

4

6

8

10

12

14

16

18

20

0.1 1 10 100 1000 10000po re water sulp hide (µmol/l)

Num

ber o

f spe

cies

Red List species -.282***other species - .176*

Detrended correspondence analysis

-2 10

-28

Alkalinity (pw)

Sulphide (pw)

Al (pw)

SO4 (pw)

Ca (pw)

Fe (pw)

NO3 (pw)

NH4 (pw)

PO4 (pw)

Fe:PO4 (pw)

Alkalinity (sw)

Absorption (sw)Turbidity (sw)

SO4 (sw)

NO3 (sw)

PO4 (sw)

Aquatic macrophytesRed List

Red List

Oligotrophic and mesotrophic

Eutrophic

Hypertrophic

Other

Helophytes

� Turbid, alkaline, P- and S-rich: only eutrophic and hypertrophic species� High pore water Fe:PO4 ratio: more mesotrophic, oligotrophic and Red

List species. � Most helophytes: high S, Al and Fe:PO4 and low PO4

Conclusions

The pore water Fe:PO4 ratio is an indicator for bothbiogeochemical processes and biodiversity

It is a valuable tool to:

� understand biogeochemical key processes � predict future changes in water quality � evaluate the chances for reestablishment of aquatic

vegetation after restoration� select the most promising locations for restoration� optimize restoration measures

� Hein Pijnappel, Judith Sarneel, Babette Bontes, Marjolijn Christianen, Artur Banach, Marlies van derWelle, Bas Bierens, Kim Kobes, Jan van de Graaf, Martin Versteeg, Jelle Eygensteyn, Roy Peters, and Germa Verheggen

� The Dutch Ministry of Agriculture, Nature and Food Quality for funding the research

� All nature managers involved

� You, for listening!

Many thanks to