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
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 What makes algae grow? Light Nutrients
(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 biology descripotion 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 by vertical movements to reach the most favorable depth.
Phytoplankton growth rates are calculated from size and volume relationships that affect nutrient uptake, light harvesting, and temperature dependence.
Eight functional groups of phytoplankton are simulated that differ in their surface area/volume, capability to fix nitrogen, use silica and buoyancy regulation.

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

8. UFI PROTECH hybrid model
Feature
UFI PROTECH hybrid model
Representation of phyto-plankton
Carbon-based; constant stoichiometry; multiple (eight) algae classes
Nutrients
N, P, Si.
Zooplankton
Modeled.
Suspended Solids
VSS=Detritus + Algal material.
Phytoplankton Settling
Some phytoplankton. Others may actively move up or down.
Resuspension
Complete resuspension of deposited algal particulates (Algal C) in mixed layer
Deposition
Below mixed layer: determined by settling velocity.
In mixed layer: no deposition.
Sediment Release, Diagenesis
Release of SRP, NH3 and Si from phytoplankton at same rate as in the water column (respiration).

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

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

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

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

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

15. 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

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

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

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

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

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

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

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

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

24. 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.