Fresh Water Ecology

Water Cycle

Water Cycle• oceanic water: majority ______

• continental water ______– surface

• glaciers (75% of continental water)• lakes, rivers (0.3% of continental water)• biomass

– subsurface (24.7 % of continental water)• groundwater• ____________

• atmospheric water _____– water vapor– ________, suspended crystals

• cycle driven by _________and ________

Water Cycle

• evaporation – liquid to vapor; major entry into atmosphere– _____________ – water vapor released by

organisms as part of their metabolism

• ____________ – solid to vapor; minor contribution – occurs over polar ice caps and glaciers

Water Cycle

• precipitation – transfer of water in various forms from the atmosphere to the continents and the oceans– Rain, dew, snow, sleet, hail– Most are trapped in the porous rocks as

subsurface water

• runoff – surface water flowing to the ocean– Rivers, lakes

Water Cycle

• __________ (infiltration) – movement of subsurface in the aquifer– Much slower than runoff– Filtration, adsorption

• _______ – porous, water-bearing layers of sediments; sealed by less permeable layers below and, usually above– _______ – surface water entry into the aquifer– Discharge – subsurface water exiting the aquifer

Aquifer System

• Defined by interconnected layers of rocks through which water percolates

– modified by _________, but is not necessarily constrained by surface geological structures

– system of conduits for _____________ flow

Edwards Aquifer

Aquifer System

• Parts of an Aquifer

– Contributing (or Drainage) zone

– Recharge zone

– Artesian zone

Edwards Aquifer

Aquifer System

• Contributing (Drainage) zone • area that collects surface water• usually _______• mostly ________ • most effective contributing zones – _______, ______

rock beds – Minimizes _________– Maximizes _________ into aquifer

Edwards Aquifer

Cibolo Creek

Helotes Creek

Aquifer System

• Recharge Zone• entry from surface into ___________

• most of surface water enters the aquifer

• Usually has ___________– cliffs, caves, escarpments, disappearing creeks/rivers

Edwards Aquifer

Helotes creek

Aquifer System

• Artesian zone • Much lower elevation

• Percolating water beneath overlying layers of less permeable rocks – higher pressure due to water entering the aquifer at ___________

• _________– typically do not need pumps to extract water

Edwards Aquifer

Critters inside Aquifers

• Adapted to _______, very low _________– ______, no pigments– Small bodies, fast _____________

Aquifer System

• Significance of aquifers

– Drinking water

– Agricultural irrigation

– Recreation

Drainage or Catchment Basins

• “a geographical area in which water , sediments, and dissolved materials drain into a common outlet” (EPA definition)

• ______ - highest points of land between two adjacent drainage basins; delineates the two basins

Continental Divides

Major River Basins of Texas

Watershed Dynamics

• _________ – the drainage basin plus:– _______ and rainfall– Geology and geography

• Nature of soil• ___________• Degree of urbanization

– Impurities and pollutants

• Large watersheds – very heterogenous

Freshwater Ecosystem

• Surface water communities in the Catchment basins

– Lotic (running water)

– Lentic (standing water)

Lotic Systems

• Constant, unidirectional flow• ________-rich• Often shallow

• deepens with age

• _______ retention of water• __________temperature distribution

Lotic Systems

• Stream order – 1st order (________ streams) – no tributaries

– 2nd order – has 1st order tributaries

– 3rd order – has 1st and 2nd order tributaries

– 4th order – has 1st, 2nd and 3rd order tributaries

– And so on….

Stream Ordering(Strahler method)

Stream Ordering(Shreve Method)

Lotic Systems

• Channel features of streams change as they increase in order

– _______ (lower order) - narrow channels and v-shaped; higher energy (faster flow); river bed of large rocks and cobbles

– ________(higher order) – more meandering, wider, more fine particles (sand, silt and clay particles ) on river bed

Lotic Systems

• Classification of streams based on flow:

– _________ (perennial) – continuous flow

– __________ – regular (lasting for weeks) interruption

– ________ (ephemeral) – unpredictable flow; dry for most parts of the year

Lotic Systems

• ________– upper surface of the aquifer_____ stream – water table at or close to the surface______ stream – water table below or shifts away from the surface

Aquarena Spring – a gaining spring

Lotic Habitats

• 2 distinct areas within a stream or river– _________ – deep, wide areas, with slow water

movement; fine sediments (mud and silt)• Pools• _________

– _________ – shallow areas with fast flowing water, with coarse sediments bearing coarse organic material (twigs)

• ______ – fast moving, turbulent water• _____ – fast flowing, non-turbulent• ______ – slower flowing

Lotic Habitats

• Depositional Zone– __________– provide habitat similar to lakes

and ponds (lentic)• Dragonflies, damselflies, water striders• Detritivores – organisms that eat non-living organic

particulates (snails, some bugs and crustaceans)• Algae – attach to rocks and large plants

– _______ – large fish, invertebrates and large plants that root into the muddy bottom

Lotic Habitats

• Erosional areas – _______means less stability, but more oxygen in the water – Few large plants; mostly small or unicellular

algae– Animals: fast moving or have strong

attachment structures• Fish fry, small fish, mayflies, caddisflies, water

pennies

Lotic Habitats

• _______ Zones – adjacent terrestrial habitats– Stream bank and lower flood plain– Source of nutrients – _________ stabilizes the stream bank

Lentic Systems

• sluggish flow of water in various directions• some depth may be _______________• become shallower with age• longer __________ of water• temperature __________ typical

Lentic Systems

• Origins:– ________ depressions – Rain-filled caldera– Oxbow (________) from meandering rivers– _______ depressions– Dammed up rivers (__________)

Lentic Systems

• ________ – adjacent to lakes; transition between water and land– Marsh – fed by surface run-off; soft stem

vegetation

– ______ – very wet soils, standing salt- or fresh-water; trees and shrubs

– ______ – peat covered, acidic water; peat moss, trees and shrub; more acidic; cool climate

– _____– ground water fed, peat covered, more alkaline water; cool climate

Marsh

Swamp

Bog

Fen

Lentic Habitats

• _________– shallow vegetated, wave-dominated, near-shore areas

• __________ – open water; well-lit

• _____________– bottom water; little or no light

Lentic Habitats

• Plants– ________ – rooted plants, near the shore

– _________ – rooted plants; leaves floating on surface; some floating plants

– __________ – rooted plants with all parts submerged

Lentic Habitats

• Consumers– _______ – close to or at the surface

– nekton – actively swimming

– _______ – cling to surfaces

– _______ – on or in the bottom

– _______ – drifting organism

Lentic Habitats

• Thermal Stratification - in larger, temperate lakes

– Summer, warmer water forms a surface layer (__________); low nutrients

– Cooler (around 4 ⁰C) water (________) lies below; high nutrients

– Separated by the __________; referred to as metalimnion

Lentic Habitats

• Thermal Stratification (continued)

– Fall, cooling surface water

– When cool surface water sinks and mixing occurs; nutrient-rich hypolimnion brought to surface = ____________

Lentic Habitats

• Thermal Stratification (continued)

– Winter, ice on top of well mixed water; surface at 0⁰C, bottom at 4⁰C – _______________

– Spring, ice melts to 4⁰C and sinks = _____________

Lentic Habitats

Lentic Habitats

• Thermal Stratification (continued)– Temperate lakes – _______; turnover twice a

year

– Warmer climates (Texas) – ________; turnover in the fall/winter season

Lentic Habitats

• Succession – natural aging process– Young lakes – deep, few rooted plants

• low organic matter and little nutrients• High clarity• High oxygen even in the hypolimnion• _____________

Lentic Habitats

– Mature lakes - gradually shallower due to build-up of organic material

• Lots of rooted plants• More nutrients being recycled• More turbid water• Higher microbial activity• Lower oxygen • hypolimnion may be _______ (low Oxygen) or

_______ (no Oxygen)• __________

Lentic Habitats

• Final stage – _________– Sediment accumulation – decrease depth– Shallow water drain and evaporate– Lake bed dries up to become a _________

• ______________ – hastening of succession due to fast build up of nutrients from sewage, septic and other waste sources

Lentic Habitats

Lentic Habitats

• Play video

Productivity of Freshwater Systems

• ___________ - considered on of the most productive – Provide food and habitat for diverse

organisms– Act as temporary water storage basins

(moderate flooding)– Act as ___________that absorb excessive

nutrients

Productivity of Freshwater Systems

• ___________– much lower productivity– Important in the cycling of nutrients and

carbon (CO2 and CH4)