Aquatic Ecology I

1. Aquatic Ecology I Ann Zimmerman ann.zimmerman@utoronto.ca 402 Ramsay Wright

2. Ramsay Wright Ramsay Wright (402) Lash Miller 2

3. Ecosystem perspective on aquatic systems Emphasizing relationships among: • the physical aquatic habitat (temperature, morphometry, hydrology, light etc.) • chemical milieu and • biological community structure

4. Aquatic ecologists think of watersheds as systems and advocate ecosystem based, adaptive management Watershed - area of land draining to a particular lake, wetland or stream Everything that happens on the watershed affects stream/lake water quality

5. Individual lakes can also be thought of as ecosystems amenable to adaptive management However just as timber interests can operate independently from the rest of the forest ecosystem (at least for awhile), there are resource managers/commercial fisherman interested in lakes (or oceans) only for their fisheries or other commercial interests focused solely on water itself (drinking water, irrigation, hydroelectric generation).

6. So…. not surprisingly, just as humans eventually get themselves into trouble when they try to divorce timber production from the rest of the forest ecosystem, we get ourselves into serious difficulties when we forget that water and fish are intimately connected to each other and to other components of the aquatic ecosystem.

7. Given an ecosystem perspective, what kinds of questions might limnologists ask(and what might you expect to understand when we’re finished!)? Three-spined stickleback  (Gasterosteusaculeatusaculeatus)

8. What accounts for variance in growth rates of lake trout among lakes? Redrock Lake 7 yr old Lake Louisa 7 yr old 43-46 cm 35-38 cm lake size/shape? temperature? transparency? nutrients? forage? 8

9. Is water quality more likely to respond to watershed phosphorus control or in situ rehabilitation of piscivore populations? Northern Pike Esoxlucius

10. Can we do anything to reduce loss of the Aral Sea: once the world’s 4th largest freshwater lake? The "virtual water" trade: poor countries growing water-intensive crops for export to countries then able to conserve their own water supplies.

11. The nature of Canada’s coming water “crisis”? • Alberta: dry to start with • The Great Lakes Basin: billions of dollars in lost shipping, unprecedented nuisance and/or toxic blooms of algae • Pressures for export: the American situation www.inkcinct.com.au/

12. What are the likely consequences of diverting water from James Bay? climate change? massive loss of wetlands? eutrophication? habitat fragmentation? exotic invasions? 12

13. Rather than trying to take detailed notes, use the slide printouts and referencetheLimnological Facts of LifeENV234homepage and follow the linksenv.chass.utoronto.ca/env234y/bht Rainbow darter (Etheostomacaeruleum) 13

14. http://env.chass.utoronto.ca/env234y/bht

15. http://env.chass.utoronto.ca/env234y/bht

16. The limnological facts of life Not quite everything you always wanted to know about aquatic ecosystems in four lectures. http://env.chass.utoronto.ca/env234y/bht or ENV234Y homepage and follow the links

17. http://env.chass.utoronto.ca/env234y/bht

18. What? • stratification • morphometry • light regimes • hydrologic regimes • nutrient chemistry • primary producers • secondary producers • tri-trophic relationships

19. When? Today:physical limnology (temperature, morphometry, light) Wed:hydrology and chemical limnology (the bioassay lab) Mon:primary/secondary producers, tri-trophic interactions Wed:Case studies: ecosystem ecology (Scaviaet al.), the Aral Sea, the Grand Canal

20. Limnological Facts of Life I.Temperature/Density Relationships • maximum density of water does not occur at its freezing point • change in density of water as a function of temperature is not linear

21. Density (g.mL-1) of water as a function of temperature Maximum density not 0o C LFoL: I

22. 18o and 20o (998.6232) - (998.2323)= 0.3909 g Change in density wrt temperature is not a linear function Comparison of density (g.L-1) differences 12o and 14o (999.7277) - (999.5247)= 0.203 g

23. Take -home message • As water at the surface of a lake changes temperature (e.g. warming in response to incoming solar radiation or cooling as a result of convective losses), it will change its density. • As it cools, it will sink (and be mixed into the underlying water) • As it warms, it will float as a lens on top of underlying water unless/until wind energy is sufficient to mix adjacent layers.

24. LFoL Figure 1: Temporal changes in lake temperature profiles Check LFoL • epilimnion • metalimnion • hypolimnion • What’s happening wrt time 7? • epilimnion cools • thermocline degrades 7 24

25. Lakes at our latitude are dimictic: they “turn-over” twice a year (once in the fall and once in the spring). • Depending on latitude/altitude, lakes may turn-over only once a year (monomictic) or never (amictic) • Depending on depth, lakes may turn-over periodically (polymictic)  thermocline

26. inverse or - stratification isothermy + stratification isothermy While most Ontario lakes are dimictic . . . lakes can also stratify chemically e.g. Crawford Lake 26

27. Density as a function of salinity(kg.L-1)

28. 0% and 35% salinity (1000.00) - (1028.22)= 28.22 g Density differences due to temp and salinity (g.L-1) 4o and 1o (1000.0000) - (999.9267)= 0.033 g

29. Lakes that are chemically stratified are called meromictic lakes mixolimnion chemocline monimolimnion From Wetzel 2002 Limnology

30. Meromictic Lakes • ideal for paleolimnological studies • lack of bioturbation in sediments • highly predictable deposition characteristics • chemically interesting (speciation of redox-sensitive elements) • biologically interesting because diversity microbial fauna across the chemocline • most notorious, however, for releases of dissolved carbon dioxide and methane, such as at Lake Nyos in Cameroon, West Africa where 1800 people died of asphyxiation due to a CO2 emission

31. Iroquois villages and Canadian farm yard catchment is < 100 ha Crawford Lake is 70 km west of Toronto 2000 Fossil rotifer lorica Fossil maize smut spore Portulaca Cucurbita Fossil pollen from Iroquoian Zone -1950 Canadian Zone -1900 Charcoal rich (Clark and Royall 1995) turbidites -1750 Crawford Lake JOHN H. McANDREWS, University of Toronto JANE L. TERANES, Scripps Institute of Oceanography CHARLES L. TURTON, Royal Ontario Museum CHAD A. WITTKOP, University of Minnesota ERIK J. EKDAHL, University of Michigan

32. Changes in the density of seawater as a function of temperature (and salinity) also lead to stratification in the oceans . . . ,

33. . . .and rising sea levels as the oceans warm due to climate change Temporal variations in global mean sea level (MSL) computed from TOPEX/POSEIDONmeasurements between Dec 92 and Jul 02 • The vast volumes of water in the oceans and the increases in ocean temperatures associated with climate change are leading to rising sea levels from thermal expansion (increases of 57 mm since 1993) • Thermal expansion is currently the most significant element in increasing sea levels Walsh, J.E. 2005. Chapter 6: Cryosphere and Hydrology. ACIA Scientific Report.

34. Water at 10oC = 0.9999919 gm.cm-3 or a space 1 x 1 x 1.00002724 cm IBID Water at 12oC = 0.9995247 gm.cm-3 or a space 1 x 1 x 1.0000455 cm Sea level is not affected by melting sea ice as that simply displaces a volume of ocean water equivalent to its mass Projected global sea-level rise between 1990 and 2100 from both thermal expansion and land ice changes for each of seven AOGCMs (11 to 43 cm)

35. Remain skeptical • Local sea level is a surprisingly complicated function of wind, currents and temperature and globally sea levels can vary by up to 2 metres http://www.exitmundi.nl/images/sealevelamericaMap.jpg globalclimatechange.jpl.nasa.gov

36. Changes in (salinity derived) density may also impact THC (MOC) 1000 year residence time Currently it remains uncertain as to what might happen: Some models project a weakening or even collapse of the THC; others suggest its trajectory will shift either north or south; still others project no change (AR4 predicts slowing)

37. The whirlwind tour Largemouth bass (Micropterussalmoides) • stratification • morphometry • light regimes • hydrologic regimes • nutrient chemistry • primary producers • secondary producers • tri-trophic relationships http://www.gen.umn.edu/research/fish 37

38. Layer on morphometric effects(in 2 slides)!

39. High values of mean depth: large volumes relative to surface area Low values of mean depth: small volumes relative to surface area Morphometric descriptors(II: Lake Shape) • shoreline development (Plake:Pcircle of similar area) • mean depth m (V in m3/A in m2) Increasing influence of sediment chemistry on water column chemistry

40. High Low Watershed: Lake Surface Area Ratio How big is the watershed compared to the lake? Ratio = Watershed Area = Aw:Ao Lake Area Higher ratio = higher levels of nutrient loading; higher productivity; often reduced water quality

41. The whirlwind tour • stratification • morphometry • light regimes • hydrologic regimes • nutrient chemistry • primary producers • secondary producers • tri-trophic relationships 41

42. What happens to light (EMR) when it reaches Earth’s atmosphere? Reflection Transmission Scatter (proportional to 1/λ4 - short scatter more) Absorption (H2O, CO2 O2, O3, etc.) As EMR moves through the atmosphere, scattering and absorption change both its intensity and its spectral composition. Why is the sky blue?

43. Fig 6.1-5 latent/sensible heat = 30%

44. EMR that reaches the surface of a lake depends upon III. Light in Lakes • Latitude • Season • Time of day • Elevation of the lake • Meteorological conditions (ice cover, wave disturbance, suspended materials)