Freshwater Life Zones

Melissa Eng, Martha Holland,Conner Martin, Colin Ng, and

David Wright

Aquatic Environments

• Water covers 71% of the Earth's surface• Saltwater• Freshwater• Four Groups of organisms 

o Planktono Nektono Benthoso Decomposers

• Euphotic Zone• Bottom of the Ocean

Climate

Lakes• Very low salt content• Largely varying temperature• Zonated, often with varying degrees of water clarity

 Rivers• Often cooler temperatures, warming as the river nears the

ocean• Murky water, progessively more so as the river nears the

ocean• High oxygen content

 Wetlands•  Higher salt content•  Wide variety of plant life

Plant Life

Why are there so many plants? • lots of carbon dioxide• sunlight and nutrients

 What kinds of plants?• surface: duckweed• water column: floating strands of waterweed• water surface: water lilies • shallow water at edge: reed varieties

 Limiting growth factors? • pressure• light intensity

   

Effects of Plant Nutrients on Lakes: Too Much of a Good Thing...Nutrients affect the types and numbers of organisms the lake can support• lakes are classified by:

nutrient content primary productivity

 o oligotrophic: poorly nourished o eutrophic: well nourishedo mesotrophic: between these extremes

 Cultural eutrophication: human inputs of nutrients from atmosphere and nearby urban/agricultural areas (accelerates eutrophication)   

Animal Life

10,000 species of fish Less than 5,000 species of amphibians Few hundred types of reptiles/mammals/birds

o newts and salamanders, frogs and toads, turtles, crocodiless, snakes, birds, beavers/otters/hippopotamus/sea cows

 Invertebrates: land-living but live in freshwater early on, adult freshwater stages, bottom-living community   Vertebrates: fish! 

40% of all fish species live in freshwater  

Lakes: Water-filled Depressions

What are lakes?Large bodies of standing freshwater formed when precipitation, runoff, and groundwater seepage fill depressions in the earth's surface What causes these depressions?    - glaciation    - crustal displacement    - volcanic activity Where do lakes get their water?    - rainfall    - melting snow    - streams that drain surrounding watersheds

Freshwater Lakes: The Littoral ZoneThe littoral zone is the top layer near the shore• sunlight penetrates all the way to sediment • most productive zone• biodiversity: algae, rooted plants, animals

(turtles, frogs, crayfish), fish(bass, perch, carp)

 

Freshwater Lakes: The Limnetic ZoneThe limnetic zone is the surface layer away from shore that extends to depth penetrated by sun• photosynthetic body of the lake• organisms:

microscopic phytoplankton (floating microorganisms) and zooplankton 

nekton (actively swimming animals) large fish

Freshwater Lakes: The Profundal ZoneThe profundal zone (also known as the euphotic zone) is the section of water too dark for photosynthesis• low oxygen levels• fish! • primary consumers

attached or at bottom of lakebenthos: bottom-dwelling animals

       

Freshwater Lakes: The Benthic ZoneThe benthic zone is the bottom of the lake • inhabitants: decomposers, detritus feeders, fish• nourished by dead matter from:

littoral and limnetic zones sediment

Lakes and the Seasons

What happens during summer and winter?• water stratified in different temperature layers• no mixing!

 What happens during fall and spring?• overturns: all layers mix

temperature equalizes throughout oxygen: surface to bottom nutrients: bottom to surface

Littoral Zone

Limnetic Zone

Profundal Zone

Benthic Zone

Sunlight

Painted Turtle

Green Frog

Pond Snail

Diving Beetle

YellowPerch

Bloodworms Northern Pike

Plankton

Muskrat

Blue-winged Teal

Textbook Figure 6.15

Water travelling from mountains to the sea creates different aquatic conditions and habitats! Terms to know: • Surface water is precipitation that does not sink into the ground or

evaporate.  When surface water flows into streams, it becomes runoff.

• A watershed (or drainage basin) is the land area that carries runoff, sediment, and dissolved substances to a stream.

 Small streams form rivers; rivers travel downhill to the ocean. Streams shape the land and receive nutrients from bordering land ecosystems.  

Freshwater Streams and Rivers; From the Mountains to the Oceans

http://www.eoearth.org/article/River 

Freshwater Streams and Rivers...

The Source ZoneStreams often begin in mountainous or hilly areas at the source zone. Source zone headwaters typically:• are shallow, cold, clear, and swiftly flowing• dissolve large amounts of oxygen from the air (high DO content)• lack nutrients/phytoplankton; streams are not very productive

 Most nutrients at the source zone come from the organic matter (leaves, branches, bodies of living and dead insects) that falls into streams. The zone is populated by cold water fish with compact, flattened bodies that allow them to live under stones; algae/mosses; organisms that require high levels of DO to survive 

Freshwater Streams and Rivers...

The Transition ZoneHeadwater streams merge to form wider, deeper, and warmer streams at the transition zone. At the transition zone, water flows down gentler slopes with fewer obstacles.  The transistion zone is characterized by water that:• is cloudier due to suspended sediment• slowelowing• contains less dissolved oxygen• is warmer in temperatuer, supporting producers - higher productivity

Freshwater Streams and Rivers...The Floodplain ZoneAt the floodplain zone, streams join into wider and deeper rivers that flow across broad, flat valleys. The floodplain zone is characterized by:• higher temperatures• less dissolved oxgen• slow moving water that supports a fairly large populations of

producers• increased erosion/run off• muddy water containing high oncentrations of silt

 At the mouth, the river may divide into channels as it flows through deltas.

Freshwater Inland Wetlands: Vital Sponges• Marshes, swamps, bogs • Not considered to be freshwater ecosystems, due to

higher salt content• Support many terrestrial and aquatic species• Home to over one third of endangered species in the

United States• Most biologically productive ecosystems in the world• Act as a filter for poll

Case Study: Inland Wetland Losses in the United States• Causes of Wetland loss

o 80% caused by crop growth o Mining o Forestry o Oil and Gas extraction

• Other countries o Ex. German and France 80% loss

• 95% of wetlands are inland freshwater wetlando Alaska has many wetlands

• The loss of natrual capital 

Impacts of Human Activities on Freshwater Systems• humans disrupt many freshwater systems

o through pollution of watershedso both irrigation and industrial byproducts can effect

freshwater farm land runoff waste from factories

o hydroelectricity or damso filling in wetlands

This is an example of a watershed

Current Event: India and Pakistan at Odds Over Shrinking Indus Riverhttp://news.nationalgeographic.com/news/2011/10/111012-india-pakistan-indus-river-water/ • India and Pakistan's major industries use billions of gallons of

water each year (on average, 737 billion gallons of water withdrawn from the Indus River annually to grow cotton)

• Irrigation and hydroelectric projects are draining the river's flow; glaciers are melting in Kashmir which will increase flooding and eventually drain the water supply

• Downstream provinces are drying out, coastal districts becoming "economically orphaned"

• Competition for water is provoking conflict between the two nations

• More conservation and adaptation is necessary!

To Do ListNote sheet for classAssessmentVideo clips/visual representations - everyone look for videos/photos to enhance slides! (give link to Baxley prior to class)    students.discovery.education.com            Code: GHS2010            Password: researchCurrent Event for discussionAll slides:    Martha - freshwater streams/rivers, current event    Melissa - lakes, effects of plant nutrients    Colin - impacts of human activities, aquatic environment    Connor - freshwater inland wetlands, freshwater systems    David - case study       

Works Consulted

Day, Trevor. Lakes and Rivers. New York: Chelsea House, 2006. Print.

Hicks, Sarah. "Pollution." Lake Scientist. Web. 19 Oct. 2011.<http://www.lakescientist.com/learn-about-lakes/water-quality/pollution.html>. "Humans and the Water Cycle | Sciencelearn Hub." Home | Sciencelearn Hub. Web. 18 Oct. 2011. <http://www.sciencelearn.org.nz/Contexts/H2O-On-the-Go/Science-Ideas-and-Concepts/Humans-and-the-water-cycle>.  Ruzycki, Elaine, and Lindsay Anderson. "Lake Ecology -- Lake Zones." Lake Access: Real Time and Historical Water Quality Data for Lake Users. Natural Resources Research Institute. Web. 19 Oct. 2011. <http://www.lakeaccess.org/ecology/lakeecologyprim9.html>.  Smith, David K. "The Freshwater Biome." University of California Museum of Paleontology. California Academy of Sciences, 2005. Web. 19 Oct. 2011. <http://www.ucmp.berkeley.edu/exhibits/biomes/freshwater.php>.