Effects of raised temperature

and northward species migration

on experimental tidal freshwater marsh

communities from European and American

estuaries

Marisa Schönfeldt1, Andrew Baldwin2, Kai Jensen1 1. University of Hamburg, Biocentre Klein Flottbek

2. University of Maryland

• Tidal Freshwater Marshes (TFM) are wetlands dominated by herbacious plant communities with

– tidal influence

– low salinity (< 0.05 ppt)

• IPCC projects an average global warming between

1.8-4.0°C at the year 2100

• Future global warming could favor northward species migration

2

Introduction

• Effects of elevated temperature and northward species migration on TFM?

• Hypothesis 1

Elevated temperature increases germination

• Hypothesis 2

Elevated temperature increases biomass production

• Hypothesis 3

Migration increases species richness

3

Introduction

Methods

Sampling

• Seed bank samples; 6 estuaries; Europe and North America

• 3 TFM per estuary (6600 cm³ soil / site)

4

Source: google maps, modified

Pamunkey (VA)

Connecticut (CT)

Waccamaw (SC)

Elbe (G)

Loire (FR)

Minho (PT)

Methods

Experimental setup

• Temperature (ambient; increased)

• Migration (no, limited, complete)

Measurements

• Initial seedling emergence

• Aboveground biomass

• Species richness

5

Picture credit: Florian Rink

6

Temperature Treatments

Mean difference: 2.85 °C

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

May June July Aug Sept

Tem

pera

ture

(°C

)

Ambient min

Ambient max

Elevated min

Elevated max

7

Migration Treatments

Homogenized

samples from

each site were

used separately

Samples from all

sites of an estuary

were mixed

Samples from all

sites of all

estuaries were

mixed

0

40

80

120

160

200

240

280

320

CT CT VA VA SC SC

-T +T -T +T -T +T

seedlin

gs / tra

y

a a

b

• EUR + NA: effect of temperature after 5 days (p<0.01)

• NA: effect of temperature after 10 days (p<0.01)

8

Effect of Temperature on Germination North America (NA)

0

40

80

120

160

200

240

280

320

G G FR FR PT PT

-T +T -T +T -T +T

seedlin

gs / tra

y

t5 t10 t15

a

b b

Europe (EUR)

G FR PT CT VA SC

0

5

10

15

20

25

30

35

CT CT VA VA SC SC

-T +T -T +T -T +T

bio

mass (

g)

/ tr

ay

a

a

b

b

0

5

10

15

20

25

30

35

G G FR FR PT PT

-T +T -T +T -T +T

bio

mass (

g)

/ tr

ay

Forbs Grasses Fabaceae

a

b b

North America (NA) Europe (EUR)

Effect of Temperature on Biomass

9

Forbs & grasses:

• EUR+NA: effect of temperature on biomass (p<0.05)

G FR PT CT VA SC FR FR

0

5

10

15

20

25

CT CT VA VA SC SC

-T +T -T +T -T +T

a a b

0

5

10

15

20

25

G G FR FR PT PT

-T +T -T +T -T +T

num

ber

of specie

s / tra

y Forbs Grasses Fabaceae

a b b

North America (NA)

Effect of Temperature on # Species

10

• NA: effect of temperature on number of forbs,

and on total number of species (p<0.05)

Europe (EUR)

G PT CT VA SC FR

0

5

10

15

20

25

No No Lim Lim Com Com

-T +T -T +T -T +T

a b

c

0

5

10

15

20

25

No No Lim Lim Com Com

-T +T -T +T -T +T

num

ber

of specie

s / tra

y

Forbs Grasses Fabaceae

a a

b

North America (NA)

Effect of Migration on # Species

11

• EUR+NA: effect of temperature on number of forbs

(p<0.05)

Europe (EUR)

No Com Lim No Com Lim

0

5

10

15

20

25

30

35

No No Lim Lim Com Com

-T +T -T +T -T +T

0

5

10

15

20

25

30

35

No No Lim Lim Com Com

-T +T -T +T -T +T

bio

mass (

g)

/ tr

ay

Forbs Grasses Fabaceae

North America (NA)

Effect of Migration on Biomass

12

• EUR+NA: no significant effect of migration on biomass

Europe (EUR)

No Com Lim No Com Lim

• Few species benefitted from elevated temperatures

• Lythrum salicaria had significantly higher biomass

production

13

Effect on Community Structure

0

2

4

6

8

10

12

G G FR FR PT PT

-T +T -T +T -T +T

bio

mass (

g)

/ tr

ay

G PT FR

Number of seedlings, biomass production,

& number of species

• increased from North to South

• was higher at North American estuaries

14

Patterns between Continents and

along Latitudinal Gradients

Summary

Ambient

Waccamaw (SC)

Ambient Elevated Elevated

Loire (FR)

Hypotheses 1 & 2:

Elevated temperature

• increased germination

• increased biomass production

• Reduced the number of species

Hypothesis 3:

• Migration increased the number of species

15

Effects of Temperature and Migration

Summary

Thanks for your attention!