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Climate Change Effects on Phytoplankton Composition in Cannonsville Reservoir

Study on effects of climate change on phytoplankton composition in Cannonsville Reservoir, examining biomass changes using innovative modeling methods.

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Climate Change Effects on Phytoplankton Composition in Cannonsville Reservoir

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  1. Upstate Freshwater Institute • Climate Change Effects on Phytoplankton Composition in Cannonsville Reservoir • Hampus Markensten1, Donald C Pierson2, Emmet M. Owens1, Aavudai Anandhi3, Elliot M. Schneiderman2, Mark S. Zion2 and Steven W. Effler1 • Email: hm@upstatefreshwater.org • 1) Upstate Freshwater Institute • Syracuse, USA • 2) Department of Environmental Protection (DEP) • NYC, USA • 3) Hunter College, Program in Earth and Environmental Sciences City Univ of New York, USA NYWEA 2009

  2. Cannonsville reservoir • Third largest reservoir serving New York City with drinking water. • Mesotrophic with a retention time of 2.6 years and a storage capacity of 373*106  m3 of water (98.5 billion gallons).

  3. Background • Future climate with warmer temperature and changed precipitation pattern increase reservoir water temperatures and affects the nutrient export from the watershed to the reservoirs. • Phytoplankton grows faster in warmer temperature and can obtain larger biomass with more nutrients. • What biological responses in the water reservoirs can be expected in the future?

  4. Objectives • Evaluate the effect on the total phytoplankton biomass and the functional groups from climate change. Method • Model phytoplankton functional groups using a dynamic mass balance water quality model.

  5. Model description PROTECH (Phytoplankton RespOnses To Environmental CHange) What makes algae grow? Light Nutrients Temperature Algae Source: Alex Elliot

  6. 1-D mass balance model using a phytoplankton biologydescripotion based on PROTECH-model (phytoplankton response to environmental change) developed by Colin Reynolds in UK. • Phytoplankton can respond to changes in nutrient, light and temperature byvertical movementsto reach the most favorable depth. • Phytoplanktongrowth ratesare calculated fromsize and volumerelationships that affect nutrient uptake, light harvesting, and temperature dependence. • Eight functional groups of phytoplankton are simulated that differ in theirsurface area/volume, capability tofix nitrogen, use silicaand buoyancy regulation.

  7. Overview of the hybrid 1D model including phytoplankton functional groups

  8. Size and Shape Influences • Growth • Temperature adaptation • Light absorption • Grazing • Passive movement (up or down)

  9. What is different in PROTECH? • Morphological relationships describe growth: r20 Reynolds (1989)

  10. Temperature-sensitivity of growth rate (rθ) as a function of s/v (Reynolds in Sommer 1989)

  11. Light effect on phytoplankton growth (Reynolds in Sommer 1989)

  12. (Reynolds in Sommer 1989) Light saturated growth Ik αr=0.257(M*s/v)0.236 αr Light intensity Ik=rθ /αr

  13. Phytoplankton Functional Groups • Large Filamentous Diatoms – Aulacoseira • Small Diatoms – Stephanodiscus • Small Flagellates – Cryptomonas, Rhodomonas • Large Flagellates – Ceratium • Large Buoyant Colonial Cyanobacteria – Microcystis • Large Buoyant N fixing Cyanobacteria – Anabaena, Aphanizomenon

  14. Main results Air temperature (Co), summary of 9 future (+65yr) scenarios.

  15. Discharge (mm), summary of 9 future (+65yr) scenarios.

  16. Water temperature (Co), Epilimnion Combined watershed and temperature effects Only temperature effect Only watershed effect

  17. SRP (µg l-1), Epilimnion Combined watershed and temperature effects Only temperature effect Only watershed effect

  18. Chlorophyll a (µg l-1), Epilimnion Combined watershed and temperature effects Only temperature effect Only watershed effect

  19. Large Buoyant Nitrogen fixers (µg Chl a l-1) , Epilimnion Combined watershed and temperature effects Only temperature effect Only watershed effect

  20. Large Filamentous Diatoms (µg Chl a l-1) , Epilimnion Combined watershed and temperature effects Only temperature effect Only watershed effect

  21. Epilimnion Base simulation Future simulation (ECHAM A1B +65yr)

  22. Conclusions • Climate may affect phytoplankton, either via in-lake changes in temperature and stratification, or due to altered processes at the catchment level, such as precipitation and temperature driven rates of nutrient export and water discharge. • This study demonstrates that in Cannonsville Reservoir, there is only a slight projected increase in total phytoplankton biomass. • Cyanobacteria biomass projected increase is largely attributable to changes in timing of nutrient export from the catchment. • Diatom biomass stay unchanged in the future scenarios except for a pronounced increase in spring attributed to both temperature- and watershed effects.

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