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

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Environmental changes affecting light climate in Andean Patagonian mountain lakes: implications for the plankton community. Presented by Beatriz Modenutti at the "Perth II: Global Change and the …

Environmental changes affecting light climate in Andean Patagonian mountain lakes: implications for the plankton community. Presented by Beatriz Modenutti at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

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  • 1. ENVIRONMENTAL CHANGES AFFECTING LIGHT CLIMATE IN ANDEAN PATAGONIANMOUNTAIN LAKES: IMPLICATIONS FOR THE PLANKTON COMMUNITY Beatriz Modenutti E. Balseiro, M. Bastidas Navarro, M.S. Souza, C. Laspoumaderes, F. CuassoloLab. Limnología. INIBIOMA-CONICET. Universidad Nacionaldel Comahue, Bariloche, Argentina.
  • 2. Andean Lakes fromChile and Argentina(Araucanian lakes)
  • 3. • 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.
  • 4. Field Studies
  • 5. Field Experiments
  • 6. Laboratory experiments
  • 7. Temperature, Light and Clorophyll a profiles
  • 8. Stentor araucanus Foissner & Wölfl
  • 9. 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).
  • 10. Photosynthetic efficiency 100 Stentor araucanus Ophrydium naumanning C (ng Chla)-1 / mol photons m-2 Picocyanobacterias 10 1 0.1 0.01 0 500 1000 1500 2000 -2 -1 µmol photons m s
  • 11. Ophrydium naumanni Pejler• Inhabit mainly the metalimnion andpreys on bacteria andpicocyanobacteria(Modenutti andBalseiro 2002).
  • 12. Photosynthetic efficiency 100 Stentor araucanus Ophrydium naumanning C (ng Chla)-1 / mol photons m-2 Picocyanobacterias 10 1 0.1 0.01 0 500 1000 1500 2000 -2 -1 µmol photons m s
  • 13. Picocyanobacteria in the DCMLago Espejo Lago Gutiérrez Lago Moreno
  • 14. Photosynthetic efficiency 100 Stentor araucanus Ophrydium naumanning C (ng Chla)-1 / mol photons m-2 Picocyanobacterias 10 1 0.1 0.01 0 500 1000 1500 2000 -2 -1 µmol photons m s
  • 15. Changing scenarios:
  • 16. 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.
  • 17. Vertical mixing can lead to a shortage of light ifplanktonic organisms are frequently mixed down tothe bottom, whereas stratification enhances lightsupply by decreasing mixing depth. Depth
  • 18. Interannual variability in wind speed may produce changes in thesummer thermocline depth and consequently in the epilimneticmean irradiance 1998-99 2003-04 t d.f. PZterm 27.7 ± 0.92 15.8 ± 0.71 9.339 13 P<0.001Kd PAR 0.141 ± 0.003 0.161 ± 0.002 4.175 13 P=0.001Kd 305 0.667 ± 0.017 0.772 ± 0.005 4.889 13 P<0.001Im PAR 199.35 ± 20.68 542.0 ± 48.3 7.380 13 P<0.001Im 305 0.05 ± 0.01 0.165 ± 0.018 6.152 13 P<0.001 Nutrient variations were statistically not significant (P> 0.05)
  • 19. In the water column: -2 -1 -2 -1 PAR (µmol m s ) PAR (µmol m s ) 1 10 100 1000 1 10 100 1000 0 0 305 320 340 10 10 380 Depth (m)Depth (m) 20 PAR < 100 µmol Photons m-2 s-1 PAR 20 30 30 40 40 6 8 10 12 14 16 18 6 8 10 12 14 16 18 Temperature ºC Temperature ºC •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
  • 20. 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.
  • 21. Rivadavia Gutiérrez 3 2 A Correntoso Mascardi Cat Prok TPP KdPAR Kd380 B 2 Mascardi Tron RDA Axis 3 TP PCA Axis 3 1 Nahuel Huapi Kd305 1 Kd340 Espejo TN Kd320 0 Futalaufquen 0 Chl TDP NF -1 -1 Ophry -2 -2 DOC -1 1 2 -3 0 1 -2 0 2 PC -1 is A 1 0 2 RD 0 1 -1 Ax Ax 2 xis AA A is -1 A xis 2 -2 RD 1 3 -2 P CA 1 3 50%The overall bacterial community composition 10%was similar in all lakes and over depth in eachlake 1%Actinobacteria β-Proteobacteria (banda 6) α-Proteobacteria Cytophaga-Flavobacterium-Bacteroides (CFB) were present in the sampledstrata.
  • 22. 103 Filaments mL-1 % Fuctional morphologies 0 5 10 15 20 25 100 0 20 40 60 80 Espejo 50% A C Espejo 10% Espejo 1% Correntoso 50% Correntoso 10% Correntoso 1% Nahuel Huapi 50% Nahuel Huapi 10% Nahuel Huapi 1% Nahuel Huapi 0.1% Gutierrez 50% Gutierrez 10% Gutierrez 1% Morphology Masc. Cat 50% Masc. Cat 10% Masc. Cat 1% Masc. Tro 50% Masc. Tro 10% Masc. Tro 1% Rivadavia 50% Rivadavia 10% Rivadavia 1% Futalaufquen 50% Futalaufquen 10% Futalaufquen 1% 50 10 Depth (% surface PAR) 1 B D 0 10 12 14 16 18 20 40 60 80 100 Filament length ( m) % Fuctional morphologiesCorno et al. 2009. Limnology and Oceanography 54: 1098-1112.
  • 23. µmol fotones m s 100 101 102 103 104•The relative proportion of filaments to total 0bacterial biovolume was higher in the upper 10layers, which have higher UVR intensities(305–340 nm). 20•We obtained a direct relationship between Profundidadmean UVR in the epilimnion and 30filamentation. 40 305 nm• Filament mean length in the upper layers 320 nm 340 nm 380 nmwas also significantly greater than at deeper 50 PARlevels. 60 10-1 100 101 102 103 305 nm 320 nm 60 R2=0.56 R2=0.52 60 Radiación UV (µW cm-2 nm-1) % Filaments % Filaments 40 40 20 20 0 0 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 W cm-2 nm-1 W cm-2 nm-1 60 340 nm 380 nm 2 60 R2=0.49 R =0.46 % Filaments % Filaments 40 40 20 20 Corno et al. 2009. Limnology and 0 0 1 2 3 4 5 6 0 5 10 15 20 25 0 Oceanography 54: 1098-1112. W cm-2 nm-1 W cm-2 nm-1
  • 24. Laboratory experiments: PAR UVR Modenutti et al 2010. Photochemistry and Photobiology 86: 871–881
  • 25. Epilimnetic levels of UVR induce filamentation and that this response is not a feature of aparticular cluster. However, β-Proteobacteria exhibited a high relative importance in filamentformation while Actinobacteria were almost absent among filaments. Modenutti et al 2010. Photochemistry and Photobiology 86: 871–881
  • 26. Consequences in the C transfer within the microbial loop •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.
  • 27. Climate change Masiokas et al (2008) indicated asignificant warming and decreasing precipitation•Glacier recession•Changes in light climate in lakes
  • 28. BLACK GLACIER 20091942
  • 29. LAGO MASCARDI•Gradient of turbidity in Tronador Arm
  • 30. PAR (µmol Photon m-2 s-1) 10-1 100 101 102 103 0The effect of the glacial claydecreases with the distance from the 10river mouth, and consequently thelake turns more transparent from P1 Depth (m)to P7 with a monotonically decrease 20in Kd values 30 P1 P2 P3 P4 40 P5 P6 P7
  • 31. 0 P1 P2 P3 10 P4 P5 P6 P7 DCM increase in depth andDepth (m) 20 magnitude along the 30 gradient from P1 to P7. 40 50 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -1 2.0 Chla (µg L ) DCM (Chla µg L ) 1.5 Magnitude of DCM -1 (concentration of Chla) has a 1.0 negative relationship with Total Suspended Solids. 0.5 0.0 0.1 1 10 -1 STS (mg L )
  • 32. 2.5 35 30 2.0TSS (mg L )-1 25 Picy (10 cell mL ) 1.5 20 3 15 1.0 10 0.5 -1 5 0.0 0 0 2 4 6 8 10 12 14 16 18 40 Distance from source (km) PICY (10 cel mL ) -1 30 Picocyanobacteria were very 20 3 sensitive to changes in light climate 10 0 0.5 1.0 1.5 2.0 TSS (mg L-1)
  • 33. Conclusions•Climate change (warming, wind, precipitations)caused changes in lake light supply.•Microbial food web was observe to be verysensitive to changes in light supply.•These changes may occur in scenarios wereanthropogenic deposition of nitrogen orincrease in phosphorus by dust was notrecorded.•This situation is of particular importance forlacustrine food webs.
  • 34. Thank you C O N IC E T