Ecologyof Lakes and Streams

(BIOL 435)• Course Introduction

• What is Limnology?

• Hydrologic Cycle

• Why Care About Water?

What is Limnology?• Does it have to do with ….

– Marine or inland waters?– Saltwater or freshwater?– Lotic or lentic habitats?– Ecology or biology?

• Multi-disciplinary:– Geography– Geology– Physics & Math– Chemistry– Biology

“Limnology is the study of the structural and functional interrelationships of organisms of inland waters as they are affected by their dynamic physical, chemical, and biotic environments.” (Wetzel, 2001)

The Hydrologic Cycle• Over large scales, water cycles between oceans, atmosphere, and the

terrestrial environment via the processes of evaporation, precipitation, transpiration, and surface and subsurface flows.

• Hydrodynamics is the variations in the movement of water and changes in its distribution in time and space.

Hydrologic flux (rate of movement)

The Hydrologic Cycle is driven largely by the energy from solar radiation, Earth’s gravity, the rotation of the Earth (Coriolis Effect), and Gravity of Moon and Sun (ocean tides).

Solar energy drives evaporation, transpiration and winds.

Solar energy causes liquid water movement, via thermal density differences and wind wave propagation.

Coliolis Effect influences the direction of wind and ocean circulation.

Earth’s gravity influences precipitation and surface and subsurface flow.

How Much Water? Where?

(Dodds, 2002; Table 1.1)

These volumes reside in their location (reservoir) for very different time scales. Ice caps for 16,000 y. Oceans for 3100 y. Groundwater for 300 y. Lakes from months to 100s y. Large rivers for 10-20 d. Atmosphere < 10 d.

What is our need for understanding aquatic ecosystems?

• Global Renewable Supply of Freshwater– 39,000 km3/y total– 9,000 km3/y accessible– Humans use 54% of

accessible

• Demotechnic Growth – Population growth.– Resource demands increase

by technology.– Positive feedback.

• Ecosystem Impacts:– Unsustainable Development– Climate Change

Resource crises in developing nations are increasing, with freshwater as a primary concern. These populations are simply not coping with increasing resource limitation. (Wetzel, 2001; Fig 1-1)

6.5 billion humans now; about 12 billion in 40 years!

Global Distribution of Per Capital Freshwater Consumption

(Dodds, 2002; Table 1.2)

Check out our luxury use compared to other countries with ample water supplies, i.e. Switzerland. (American vanity?)

Our Situation:• Not so much individuals at the tap, although that is increasing.

• Our bigger indirect consumption is for the agriculture, industry and energy we use.

• Per Capita improvement since 1970s (Clean Water Act; EPA).

• What creative technologies are out there to increase supply of improve conservation or reuse? (Dodds, 2002; Fig 1.3)

US water supply sources:• Situation is sustainable, for now!

• Surface water (lakes & streams) withdraws are greater.

• Which should we be more concerned about becoming polluted from a human resource perspective?

Global Distribution of RenewalTropical Moisture; Coastal MoistureWhat about Continental Interiors?

What is the value of water?

• Drinking water (treatment costs) $

• Crop irrigation $

• Industrial cooling processes $

• Cost of pollution on health $

• Direct value of fisheries $

• Intrinsic values ?

• Ecosystem services?