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)
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