Presentation on theme: "Aquatic Ecology Limnology- study of freshwater ecosystems"— Presentation transcript:
1 Aquatic Ecology Limnology- study of freshwater ecosystems Lentic- standing waterLotic- moving water
2 Lentic Ecosystems Depressions in land 1-2,000 meters deep In northern hemispheres, glaciers left behind carved out basins that filled with rain and snowOther causes include:Silt, driftwood and other materials that block the flow of streamsStreams that were flat get cut off to create “oxbows”
3 Lentic EcosystemsCraters from extinct volcanoes fill with water
4 Lake Formation Many lakes are formed by one of two mammals Humans- dam rivers for power, irrigation, diggingBeavers- dam streams to form shallow ponds or lakes
5 Lake Layers3 layersEpilimnion- “upper lake” consists of a free circulating upper layerMetalimnion- also called thermocline or “middle lake” has a rapid decline in temperature (1 degree Celsius for every meter you go down)Hypolimnion- “lower lake” is the deep, colder layer
6 Lake StructureLittoral zone- shallow water zone, light reaches the bottom and it usually has plantsEmergents- plants whose roots and stems are in water but upper stems and leaves are out of the waterLimnetic or Pelagic zone- open water, and hasPlankton- suspended organismsNekton- free swimming fish
7 Lake Zones Benthic zone- sediment on bottom of lakes and ponds Photic zone- where light penetrates to the bottomAphotic zone- under water area where light does not reachEutrophic- nutrient richOligotrophic- nutrient poorHypertrophic- excessive nutrients
8 Lake Temperatures Summer/Spring Water is warm on top and cold on bottom
9 Lake Temperatures Fall/winter Temperature on surface drops and metalimnion sinksEpilimnion increases until all water is the same temperature\Water circulates oxygen and nutrientsOverturn- seasonal mixing of water
10 Water Chemistry Dissolved Oxygen (DO) Enters the water through the atmosphere and photosynthesisAmount of oxygen the water can hold depends on pressure, temperature, and salinityCold water holds more oxygen that warm waterAs atmospheric pressure increases, so does the amount of oxygen in the waterOxygen absorbed by the surface is mixed by turbulence of internal currentsOverturn replenishes oxygen in the water
11 Water Chemistry Carbon Dioxide Carbon dioxide is usually the same concentration as that in the atmosphere
12 Water Chemistry pH A measure of the acidic or basic the water is On a scale of 1-141 is very acidic and 14 is very basic7 is neutralFreshwater 3-10Rainwater 5-6Streams and lakesLimestone under the water causes the pH to increase(or become more basic)
13 Lotic Ecosystems Flowing water (rivers and streams) Velocity and current decide most things because it cuts channels and affects living organismsVelocity is determined by size, shape, gradient of the channel, roughness of bottom, depth, and precipitation
14 Streams May begin as outlets of ponds or lakes Flow is determined by the lay of the land if the stream has not been disturbedAs water flows, it picks up debris that scrapes the bottom and makes the stream bigger
15 Terms Meander- bends in streams (aka. Sinuosity) Watershed- body of land where all runoff collects in a common body of waterTurbidity- the amount of particles suspended in water prohibiting light to shine throughChannel- the stream bed and banks formed by flowing waterFlood Plain- a strip of land that is normally dry and flat that is on the sides of a river or stream and is wet during floods.
16 TermsRiparian Zone- the land and vegetation bordering flowing or standing waterRiffle- a section of a stream where the water is shallow, fast moving, and is broken into waves by an obstructionSiltation- deposition of fine particles (silt) on the beds of streams or lakesPools- water that is relatively deepBankfull Width- where water will stop if it comes out of the stream
17 How can you tell if a stream is healthy? Stream Quality is determined byArea coverDo things hang over the stream?EmbeddednessAre there dirt particles on the bottom?DepthIs the stream shallow or deep?Sediment depositsAre there sediment build ups?Channel flowDoes water fill up the channel?
18 Stream quality continued… Channel AlterationHas concrete, rock, or anything else been added to the stream?Frequency of riffles or bendsDoes the stream curve or have any white water?Bank stabilityAre the banks falling into the stream?Vegetative Protection (on the banks)Are there plants growing on the banks?Riparian zone widthHow big is the area on the bank where plants grow?
20 Stream ChemistrypHA range of 6-9 is ideal for running freshwater fish and bottom dwelling invertebratesSynergistic EffectsHappens when two things combine to produce effects greater than their sumExample.) Pollutants can change the pH of a stream
21 Stream Chemistry Dissolved Oxygen (DO) If dissolved oxygen drops below 5 mg per liter, aquatic life is stressedThe lower the concentration, the more stressLevels below 1-2 mg per liter for a few hours result in “fish kills”
22 Stream Chemistry BOD (biochemical oxygen demand) The amount of oxygen needed for decompositionIf there is little oxygen, decomposers that use it will dieToo much oxygen causes “gas bubble disease”RareOxygen blocks blood vesselsCan see bubbles on the fins and the skin
24 Stream OrdersStreams join together to form rivers. Each time one stream joins another “order” changes.A first order stream is one that does not have any other stream joining it.A stream can only increase in order if a stream of a similar order joins it.For example, when a first order stream runs into another first order stream, it becomes a second order stream. Likewise, when two second order streams join each other, it becomes a third order stream and so on.
25 Stream OrdersOrder is not increased when a lower order stream joins one of a larger order.Generally:First through third order streams are usually called headwater streamsFourth through sixth order streams are usually called medium-sized streamsAbove sixth order, the streams become riversLower order streams are usually on steep slopes compared to higher order streamsHigher order streams have flood plains
26 A watershed is a section of land where all the water runoff flows into a common basin.
27 Stream RestorationThere are many aspects to stream restoration, but some suggestions would be:Decrease the slope of the banks (if it will not compromise or eliminate the riparian zone). This is generally accomplished by using a 3:1 ratio.Stream3 ft.1 ft.BankReduces the stress on channel walls from flowing waterBecomes more stableStops erosion and sedimentationCreates a surface for vegetationStream3 ft.1ft.Bank
28 Stream Restoration Stabilize the Stream Banks Riparian Forestation Plant native vegetation on the stream banks to stop erosion. The roots of the plants will hold the soil onto the banks.Add big structures to the banks like wood, stone, or fabric that will not wash away. Fabric provides a surface to hold planted vegetation.Drive posts into the bank to keep soil from eroding into the stream.Make the channel bigger.
29 Stream Restoration Construct riffles and pools Adding large rocks and/or other materials from the site to the stream prevents natural areas from being disturbed by trucks hauling rock to the stream.Allows more DO to enter the waterSlows the velocity of flowing waterBefore adding rock to the stream, organic matter must be cleared from the bottom to be sure the rock will be stable.The rock must be lower than the bank.
30 Stream Restoration Cut and Fill Widening the channel in a particular area to allow water a larger surface to pass overIf the channel has been cut very deep, the water will not be able to get into the flood plain. By adding rock to the bottom of the channel, the water level is raised allowing it to reach the flood plain if needed.
31 Stream Restoration Add a waterfall Remove garbage Create a difference in elevation allowing the water to fall. This will increase DO, slow the flow of the water, and create a habitat for aquatic life.Remove garbage