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South American Lake Gradient Analysis

Impact of climate on shifts in stable states in shallow lakes. South American Lake Gradient Analysis. Sarian Kosten Wageningen University The Netherlands. Project outline. Research questions. Preliminary results. Outline

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South American Lake Gradient Analysis

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  1. Impact of climate on shifts in stable states in shallow lakes South American Lake Gradient Analysis Sarian Kosten Wageningen University The Netherlands

  2. Project outline Research questions Preliminary results

  3. Outline Temperate shallow lakes tend to be in either of two alternative stable states. Preliminary work suggests that shallow lakes may be very sensitive to climatic change.

  4. Low nutrient High nutrient

  5. 83 lakes Latitude 5 – 55 degrees south

  6. Sample sites

  7. 83 lakes Latitude 5 – 55 south Low altitude / coastal Shallow lakes (average 1.8 m [4.5 – 0.5]) Area between 9 and 250 ha. November 2004 – March 2006 Mid-summer samples All sampled by the same team

  8. Questions • How do algae react to higher temperatures? • N versus P-limitation? • reach higher concentrations? • How do macrophytes react to higher temperatures? • resist higher turbidities? • disappear at higher nutrient levels? Does the interaction between algae and macrophytes change at higher temperatures?

  9. Questions • How do algae react to higher temperatures? • N versus P-limitation? • reach higher concentrations? • How do macrophytes react to higher temperatures? • resist higher turbidities? • disappear at higher nutrient levels? Does the interaction between algae and macrophytes change at higher temperatures?

  10. Gyllstrom et al., 2005

  11. N. American & European lakes (Mazumder 1994) 192 (sub)tropical lakes (Huszar et al. 2006) Huszar et al., 2006 Algae reach a higher biomass – at a given total-P concentration - in colder climates

  12. Why do algae reach lower concentrations at a certain nutrient leven when the temperature increases? • Both production and respiration will increase but respiration increases relatively more than production (Lopez-Urrutia et al., 2006)

  13. Preliminary results from our study: Trophic state

  14. Tropical with distinct dry season Tropical – Subtropical with and without dry season Subtropical Polar tundra Köppen Climate Classification

  15. Polar Subtropic Tropic All lakes Total phosphorus (μg L-1) Log Chl-a Log Tot-P R2 1.5 1.4 1.9 1.6 0.59 0.94 0.56 0.38

  16. Nitrogen limited Phosphorus limited Next 2 slides is I did not show because of lack of time, but isn’t it interesting to see that we have a dominance of N limitation along almost the entire gradient. It will be nice to compare that with other shallow lakes around the globe. Limiting nutrient Redfield ratio N:P = 16:1

  17. Log Chl-a Log Tot-N R2 1.1 1.1 1.1 1.1 0.78 0.72 0.81 0.69 SLOPE EXACTLY THE SAME FOR ALL REGIONS!! Polar Subtropics Tropics All lakes Chl-a (μg/l) Total nitrogen (μg/l)

  18. Overall the algae seem to reach a slightly higher biomass at a given total-P level at higher temperatures In a comparative study between temperate and artic lakes Flanagan et al. (2003) found higher biomasses at higher temperatures as well.

  19. Why would warmer be better for algae? • Low enzyme activity when cold (Markager et al. 1999) • Presence of cyanobacteria • Absence of large zooplankton

  20. Questions • How do algae react to higher temperatures? • N versus P-limitation? • reach higher concentrations? • How do macrophytes react to higher temperatures? • resist higher turbidities? • disappear at higher nutrient levels? Does the interaction between algae and macrophytes change at higher temperatures?

  21. Coverage percentage of submerged plants

  22. Lakes with a coverage percentage of submerged plants <30% Lakes with a coverage percentage of submerged plants >30% Tropical (Sub)tropical Subtropical Polar

  23. Tropical (Sub)tropical Subtropical Polar

  24. How do macrophytes react to higher temperatures? Do they occur at higher turbidities? >>> NO Do they occur at higher nutrient levels? >>> NO

  25. Why? Not only temperature changes but total daily irradiance as well. Unbalance of data set

  26. Questions • How do algae react to higher temperatures? • N versus P-limitation? • reach higher concentrations? • How do macrophytes react to higher temperatures? • resist higher turbidities? • disappear at higher nutrient levels? Does the interaction between algae and macrophytes change at higher temperatures?

  27. Water clearing effect of submerged macropytes

  28. We found a small effect on the TP chl-a relationship Preliminary results We did not find submerged macrophytes in more turbid conditions in warmer climates We found a water clearing effect of submerged macropytes along the whole climate gradient

  29. NWO/WOTRO The National Geographic Society The Schure-Beijerinck- Popping fund Kosten Watersport bv.

  30. Gissell Lacerot Andy Lotter Bart Koelmans Carla Kruk Christina Branco David da Motta Marques Erik Jeppesen Egbert van Nes Fabio Roland Jeroen de Klein John Beijer Jose Luiz Attayde Jose Paggi Katleen van der Gucht Luc de Meester Marten Scheffer Miquel Lurling Nestor Mazzeo Susana de Paggi Vera Huszar www.salga.wur.nl

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