Environmental changes affecting light climate in Andean Patagonian mountain lakes: implications for the plankton community [Beatriz Modenutti]

ENVIRONMENTAL CHANGES AFFECTING

LIGHT CLIMATE IN ANDEAN PATAGONIAN

MOUNTAIN LAKES: IMPLICATIONS FOR THE

PLANKTON COMMUNITY

Beatriz Modenutti

E. Balseiro, M. Bastidas Navarro, M.S. Souza,

C. Laspoumaderes, F. Cuassolo

Lab. Limnología. INIBIOMA-CONICET. Universidad Nacional

del Comahue, Bariloche, Argentina.

Andean Lakes from

Chile and Argentina

(Araucanian lakes)

• Oligotrophic. TP less than 5 µg L-1

• DOC concentration (0.5 mg L-1) • High PAR & UVR transparency (KdPAR: 0.09 m-1 and Kd305: 0.52 m-1) Euphotic zone up to 55 m.

Field Studies

Field Experiments

Laboratory experiments

Temperature, Light and Clorophyll a profiles

Stentor araucanus Foissner & Wölfl

Stentor araucanus

•Mainly inhabits upper epilimnetic levels (Modenutti et al 2005).

•High UVR resistance (Modenutti et al 1998).

•Prey on long bacterial rods (Foissner and Woelf, 1994).

Photosynthetic efficiency

µmol photons m-2

s-1

0 500 1000 1500 2000

ng C

(ng C

hla

)-1 /

mo

l p

ho

tons

m-2

0.01

0.1

1

10

100

Stentor araucanus

Ophrydium naumanni

Picocyanobacterias

Ophrydium naumanni Pejler

• Inhabit mainly the metalimnion and preys on bacteria and picocyanobacteria(Modenutti and Balseiro 2002).

Photosynthetic efficiency

µmol photons m-2

s-1

0 500 1000 1500 2000

ng C

(ng C

hla

)-1 /

mo

l p

ho

tons

m-2

0.01

0.1

1

10

100

Stentor araucanus

Ophrydium naumanni

Picocyanobacterias

Picocyanobacteria in the DCM

Lago Espejo Lago Gutiérrez Lago Moreno

Photosynthetic efficiency

µmol photons m-2

s-1

0 500 1000 1500 2000

ng C

(ng C

hla

)-1 /

mo

l p

ho

tons

m-2

0.01

0.1

1

10

100

Stentor araucanus

Ophrydium naumanni

Picocyanobacterias

Changing scenarios:

In temperate lakes:

• Wind action is important in determining mixing depth.

• Epilimnion can undergo periods of heating during hot and calm weather and periods of strong mixing by wind.

Vertical mixing can lead to a shortage of light if planktonic organisms are frequently mixed down to the bottom, whereas stratification enhances light supply by decreasing mixing depth.

Dep

th

1998-99 2003-04 t d.f. P

Zterm 27.7 ± 0.92 15.8 ± 0.71 9.339 13 P<0.001

Kd PAR 0.141 ± 0.003 0.161 ± 0.002 4.175 13 P=0.001

Kd 305 0.667 ± 0.017 0.772 ± 0.005 4.889 13 P<0.001

Im PAR 199.35 ± 20.68 542.0 ± 48.3 7.380 13 P<0.001

Im 305 0.05 ± 0.01 0.165 ± 0.018 6.152 13 P<0.001

Nutrient variations were statistically not significant (P> 0.05)

Interannual variability in wind speed may produce changes in the summer thermocline depth and consequently in the epilimnetic mean irradiance

In the water column:

Temperature ºC

6 8 10 12 14 16 18

Depth

(m

)

0

10

20

30

40

PAR (µmol m-2

s-1

)

1 10 100 1000

Temperature ºC

6 8 10 12 14 16 18

Depth

(m)

0

10

20

30

40

PAR (µmol m-2

s-1

)

1 10 100 1000

305

340

380

PARPAR < 100 µmol Photons m-2

s-1

320

•The shallower thermocline depth implies an increase in light supply favouring Stentor araucanus which has higher critical light level, and higher resistance to UVR.

•The vertical segregation gives Stentor araucanus the advantage of driving light availability for other phototrophs located lower in the water column.

•Ophrydium naumanni has a lower critical light intensity consequently it is a superior light competitor. However, the sharp decrease in Ophrydium PE may result also from the incidence of UVR.

Modenutti et al 2008. Limnology and Oceanoraphy 53: 446-455

UVR and Bacteria Morphology

• The solar radiation and particularly ultraviolet radiation (UVR) have strong effects on the production, activity, and abundance of bacterioplankton (Helbling et al. 1995; Sommaruga et al. 1997;Tranvik and Bertilsson 2001).

• However, up to now few studies have shown evidence of the effects of UVR on bacterial community composition and morphological distribution.

-2

-1

0

1

2

3

-3-2

-10

12

3-2

-1

0

1

RD

A A

xis

3

RDA Axis 1RDA A

xis 2

KdPAR

Kd380

Kd305

Kd340Kd320

TP

TPPProk

TN

TDPChl

DOC

Ophry

NF

-2

-1

0

1

2

-10

1

2

3-2

-1

0

12

PC

A A

xis

3

PCA Axis 1PCA Axis 2

A BRivadavia

Gutiérrez

Correntoso

Mascardi Cat

Mascardi Tron

Nahuel Huapi

Espejo

Futalaufquen

The overall bacterial community composition was similar in all lakes and over depth in each lake

50%

10%

1%

Actinobacteria β-Proteobacteria (banda 6) α-Proteobacteria Cytophaga-Flavobacterium-Bacteroides (CFB) were present in the sampled strata.

Esp

ejo

50

%

Esp

ejo

10

%

Esp

ejo

1

%

Corr

en

toso

50

%

Corr

en

toso

10

%

Corr

en

toso

1

%

Nah

ue

l H

ua

pi 5

0%

Nah

ue

l H

ua

pi 1

0%

Nah

ue

l H

ua

pi

1%

Nah

ue

l H

ua

pi 0

.1%

Gutie

rre

z 5

0%

Gutie

rre

z 1

0%

Gutie

rre

z

1%

Ma

sc.

Cat

50

%

Ma

sc.

Cat

10

%

Ma

sc.

Cat

1

%

Ma

sc.

Tro

50

%

Ma

sc.

Tro

10

%

Ma

sc.

Tro

1

%

Riv

ad

avia

50

%

Riv

ad

avia

1

0%

Riv

ad

avia

1

%

Fu

tala

ufq

ue

n 5

0%

Fu

tala

ufq

ue

n 1

0%

Fu

tala

ufq

ue

n

1%

10

3 F

ilam

en

ts m

L-1

0

5

10

15

20

25

% F

uctio

na

l mo

rph

olo

gie

s

0

20

40

60

80

100

% F

uctio

na

l m

orp

ho

logie

s

0

20

40

60

80

100

A

C

B

Depth (% surface PAR)

50 10 1

Fila

me

nt le

ngth

(m

)

10

12

14

16

18D

Morphology

Corno et al. 2009. Limnology and Oceanography 54: 1098-1112.

305 nm

W cm-2

nm-1

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

% F

ilam

ents

0

20

40

60320 nm

W cm-2

nm-1

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

% F

ilam

ents

0

20

40

60

340 nm

W cm-2

nm-1

0 1 2 3 4 5 6

% F

ilam

ents

0

20

40

60380 nm

W cm-2

nm-1

0 5 10 15 20 25

% F

ilam

ents

0

20

40

60

R2=0.52

R2=0.49 R

2=0.46

R2=0.56 Radiación UV (µW cm

-2 nm

-1)

10-1 100 101 102 103

Pro

fun

did

ad

0

10

20

30

40

50

60

Radiación Fotosintéticamente Activa (PAR 400-700 nm)

µmol fotones m-2

s-1

100 101 102 103 104

305 nm

320 nm

340 nm

380 nm

PAR

•The relative proportion of filaments to total bacterial biovolume was higher in the upper layers, which have higher UVR intensities (305–340 nm). •We obtained a direct relationship between mean UVR in the epilimnion and filamentation. • Filament mean length in the upper layers was also significantly greater than at deeper levels.

Corno et al. 2009. Limnology and Oceanography 54: 1098-1112.

Laboratory experiments:

PAR UVR

Modenutti et al 2010. Photochemistry and Photobiology 86: 871–881

Epilimnetic levels of UVR induce filamentation and that this response is not a feature of a particular cluster. However, β-Proteobacteria exhibited a high relative importance in filament formation while Actinobacteria were almost absent among filaments.

Modenutti et al 2010. Photochemistry and Photobiology 86: 871–881

•The biovolume of bacteria that became inedible (cells > 7 μm) increase significantly in the epilimnion. •In the epilimnion nanoflagellates and ciliates encounter prey assemblage composed by a large extent of inedible cells. Thus, bacterivory would be reduced with a consequent decrease in epilimnetic trophic energy transfer.

Consequences in the C transfer within the microbial loop

Climate change

Masiokas et al (2008) indicated a significant warming and decreasing

precipitation

•Glacier recession •Changes in light climate in lakes

1942 2009

BLACK GLACIER

LAGO MASCARDI

•Gradient of turbidity in Tronador Arm

PAR (µmol Photon m-2

s-1

)

10-1 100 101 102 103

Depth

(m

)

0

10

20

30

40

50

P1

P2

P3

P4

P5

P6

P7

The effect of the glacial clay decreases with the distance from the river mouth, and consequently the lake turns more transparent from P1 to P7 with a monotonically decrease in Kd values

DCM increase in depth and magnitude along the gradient from P1 to P7.

Magnitude of DCM (concentration of Chla) has a negative relationship with Total Suspended Solids.

Chla (µg L-1

)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Depth

(m

)0

10

20

30

40

50

P4P5P6

P1P2P3

P7

STS (mg L-1

)

0.1 1 10

DC

M (

Chla

µg L

-1)

0.0

0.5

1.0

1.5

2.0

Distance from source (km)

0 2 4 6 8 10 12 14 16 18

TS

S (

mg L

-1)

0.0

0.5

1.0

1.5

2.0

2.5

Pic

y (1

03 c

ell m

L-1)

0

5

10

15

20

25

30

35

TSS (mg L-1

)

0.5 1.0 1.5 2.0

PIC

Y (

10

3 c

el m

L-1

)

0

10

20

30

40

Picocyanobacteria were very sensitive to changes in light climate

•Climate change (warming, wind, precipitations) caused changes in lake light supply. •Microbial food web was observe to be very sensitive to changes in light supply. •These changes may occur in scenarios were anthropogenic deposition of nitrogen or increase in phosphorus by dust was not recorded. •This situation is of particular importance for lacustrine food webs.

Conclusions

Thank you

C O N I C E T