Lentic Systems Lakes and Ponds

Formation of Lakes Glacier lakes Glacier lakes Oxbow lakes Oxbow lakes Playas Playas Man-made lakes Man-made lakes

Glacier Lakes Carved out by glaciers (glaciation), which fill with water Carved out by glaciers (glaciation), which fill with water Northern U.S. and Canada Northern U.S. and Canada

How Does Glaciation Work? As the glaciers retreat (melt) they act as scouring pads on the ground underneath them. As the glaciers retreat (melt) they act as scouring pads on the ground underneath them. Rocks are eroded and mineral deposits become sediments at the bottom of the lake Rocks are eroded and mineral deposits become sediments at the bottom of the lake Some suspended minerals are used by algae for growth, making the water appear green Some suspended minerals are used by algae for growth, making the water appear green

The Seven Rila Lakes in Rila, Bulgaria The Great Lakes in northern United States are the largest glacial lakes in the world.

Lake Jokulsarlon, in Iceland

Oxbow Lakes Formed by meandering rivers Formed by meandering rivers Loops of river gets cut off Loops of river gets cut off Lakes are long and narrow, and usually U- shaped Lakes are long and narrow, and usually U- shaped Common in low valleys and flat coastal areas Common in low valleys and flat coastal areas

Oxbow Lake Oxbow lake and the Chippewa River in Eau Claire, Wisconsin. Oxbow lake and the Chippewa River in Eau Claire, Wisconsin.

How Does an Oxbow Lake Form? (1) On the inside of the loop, the river travels more slowly leading to deposition of silt.

(2) Meanwhile water on the outside edges tends to flow faster, which erodes the banks making the meander even wider. (3) Over time the loop of the meander widens until the neck vanishes altogether.

(4) Then the meander is removed from the river's current and the horseshoe shaped oxbow lake is formed. Without a current to move the water along, sediment builds up along the banks and fills in the lake.

Texas Oxbow Lakes Oxbow lakes are commonly formed in the mature segments of Texas rivers. Oxbow lakes are commonly formed in the mature segments of Texas rivers. In the lower Rio Grande Valley, these oxbows are called “Resaca's”. In the lower Rio Grande Valley, these oxbows are called “Resaca's”.

Playas Formed from multiple things that leave a depression Formed from multiple things that leave a depression Soil erosion, wind, animal herds Soil erosion, wind, animal herds Small, shallow, and circular Small, shallow, and circular Common in dry plains areas Common in dry plains areas These lakes are ephemeral, and only form at certain times of the year These lakes are ephemeral, and only form at certain times of the year

Playas are important habitat for migratory birds and waterfowl. The Red-winged Blackbird, Blue- winged Teal, and the Mallard can all be found in playa lakes at some time of the year. Playas are important habitat for migratory birds and waterfowl. The Red-winged Blackbird, Blue- winged Teal, and the Mallard can all be found in playa lakes at some time of the year.

Sandhill cranes winter in playa lakes Sandhill cranes winter in playa lakes

Playa lakes in Kansas agricultural area

Man-Made Lakes Water reservoirs formed from Water reservoirs formed from Damming rivers Damming rivers Old rock quarries or mines Old rock quarries or mines Stock ponds on farms and ranches Stock ponds on farms and ranches Lake Mead is formed as a result of damming the Colorado River by the Hoover Dam. In Nevada

Zipingpu Dam on the Min River in China

Lentic Habitats Characterized by Characterized by The shoreline The shoreline The sides of the basin The sides of the basin The surface of the water The surface of the water The bottom sediments The bottom sediments

Zones of Lentic Habitats Based on Light Penetration Based on Light Penetration Littoral zone Littoral zone Limnetic zone Limnetic zone Profundal zone Profundal zone

Littoral Zone Def. The shallow, well-lighted, warm water close to shore Def. The shallow, well-lighted, warm water close to shore Light can penetrate to the bottom (part of photic zone) Light can penetrate to the bottom (part of photic zone) Rooted plants can grow (and will also have floating vegetation) Rooted plants can grow (and will also have floating vegetation) Shores have coarse sediments from action of waves Shores have coarse sediments from action of waves Sheltered areas have finer sediments (silt and clay) – plant growth in this zone occurs here Sheltered areas have finer sediments (silt and clay) – plant growth in this zone occurs here Animal life is very diverse Animal life is very diverse Invertebrates common to lotic habitats Invertebrates common to lotic habitats Small fish, waterfowl, crustaceans, reptiles, amphibians) Small fish, waterfowl, crustaceans, reptiles, amphibians)

Limnetic Zone Def. Open, well-lit waters away from the shore Lack of rooted plants because light can’t penetrate the bottom Def. Open, well-lit waters away from the shore Lack of rooted plants because light can’t penetrate the bottom Plankton and fish are common Plankton and fish are common

Profundal Zone Deep, bottom-water area with no light penetration (aphotic zone) Deep, bottom-water area with no light penetration (aphotic zone) No photosynthetic organisms or rooted plants No photosynthetic organisms or rooted plants Sediments are silt and clay mixed with organic matter that settles to the bottom Sediments are silt and clay mixed with organic matter that settles to the bottom An area of decomposition where detritus (dead organic matter that drifts from above) is broken down An area of decomposition where detritus (dead organic matter that drifts from above) is broken down Organisms living here are tolerant of little or no light or oxygen. Organisms living here are tolerant of little or no light or oxygen. Nutrients are plentiful because of decomposition Nutrients are plentiful because of decomposition

Benthic Zone Refers to the floor itself…we’ll look at this when we examine organisms at this level Refers to the floor itself…we’ll look at this when we examine organisms at this level

Biological Productivity The amount of plankton, algae, aquatic macroinvertebrates and fish that a body of water can produce and sustain The amount of plankton, algae, aquatic macroinvertebrates and fish that a body of water can produce and sustain Usually limited to the depth of light penetration Usually limited to the depth of light penetration Light penetration is limited by color of the water and amount of suspended solids Light penetration is limited by color of the water and amount of suspended solids

Ponds vs. Lakes Pond = body of water where light penetrates all the way to the bottom Pond = body of water where light penetrates all the way to the bottom Lake = depth of light penetration varies from several inches to several feet Lake = depth of light penetration varies from several inches to several feet

Determining the Trophic State Total Plant Nutrients Total Plant Nutrients Phosphorous and nitrogen are needed for plant growth and maintenance Phosphorous and nitrogen are needed for plant growth and maintenance Certain level is needed (too much or too little is not a good thing) Certain level is needed (too much or too little is not a good thing) If nutrients are too high, algae blooms occur If nutrients are too high, algae blooms occur Increase the turbidity of the water Increase the turbidity of the water Decrease the oxygen levels Decrease the oxygen levels

Chlorophyll a Chlorophyll a Measure of the algae population Measure of the algae population Influenced by the amount of nutrients Influenced by the amount of nutrients Water Clarity (turbidity) Water Clarity (turbidity) Water clarity determines how far light can penetrate Water clarity determines how far light can penetrate Phytoplankton and plants need light to grow, so won’t grow if light is limited Phytoplankton and plants need light to grow, so won’t grow if light is limited Algae blooms cause lower water clarity Algae blooms cause lower water clarity

Ecological Succession in Lakes

Ecological Succession Ecological succession is the progression of an ecosystem from one form to another Ecological succession is the progression of an ecosystem from one form to another It includes a natural aging process of a lake It includes a natural aging process of a lake Lakes and ponds evolve differently then rivers Lakes and ponds evolve differently then rivers

Over time, sediments become higher on the floor of ponds and lakes and build up. Over time, sediments become higher on the floor of ponds and lakes and build up. The shallower the lake becomes, the further light can penetrate, so more plants grow on the bottom. The shallower the lake becomes, the further light can penetrate, so more plants grow on the bottom. Water tolerant plants and shrubs move in. Water tolerant plants and shrubs move in. Marshes, swamps, and bogs are usually the mature stage of a lake. Marshes, swamps, and bogs are usually the mature stage of a lake. Finally, a meadow completes the succession stages Finally, a meadow completes the succession stages If left undisturbed, grasses and shrubs will be replaced by larger trees and forests. If left undisturbed, grasses and shrubs will be replaced by larger trees and forests.

Biological Productivity

Characteristics of Biological Productivity 4 categories of lake classification based on biological productivity (amount of organic matter)…stages of succession 4 categories of lake classification based on biological productivity (amount of organic matter)…stages of succession Oligotrophic Oligotrophic Mesotrophic Mesotrophic Eutrophic Eutrophic Hypereutrophic Hypereutrophic

Oligotrophic Lakes Def. deep, nutrient-poor lakes in which plankton is not very productive Def. deep, nutrient-poor lakes in which plankton is not very productive Nutrient level and productivity is low Nutrient level and productivity is low Water is usually clear Water is usually clear Low aquatic plants and plankton Low aquatic plants and plankton Few fish Few fish High oxygen content because of little detritus from limnetic zone High oxygen content because of little detritus from limnetic zone Sandy bottoms with little organic material Sandy bottoms with little organic material May turn into eutrophic lake over time (if runoff brings in excess nutrients or fertilizers) May turn into eutrophic lake over time (if runoff brings in excess nutrients or fertilizers)

Mesotrophic Lakes Nutrients and productivity is moderate Nutrients and productivity is moderate Some aquatic plants Some aquatic plants Water clarity is becoming somewhat cloudy Water clarity is becoming somewhat cloudy

Littoral habitat in a mesotrophic lake Littoral habitat in a mesotrophic lake

Eutrophic Lakes Def. Shallow, nutrient-rich lakes with very productive plankton Def. Shallow, nutrient-rich lakes with very productive plankton Nutrient level and productivity is high Nutrient level and productivity is high Large populations of algae, plankton, fish, plants, and macroinvertebrates Large populations of algae, plankton, fish, plants, and macroinvertebrates Frequent plankton blooms Frequent plankton blooms Sediments with high organic matter Sediments with high organic matter Water is commonly colored because of numbers of plankton and detritus material (Oxygen level may become low during summer months) Water is commonly colored because of numbers of plankton and detritus material (Oxygen level may become low during summer months)

Hypereutrophic Nutrient levels and productivity are very high Nutrient levels and productivity are very high Large populations of aquatic plants and animals Large populations of aquatic plants and animals Frequent plankton blooms Frequent plankton blooms Sediments with most organic matter Sediments with most organic matter

Temperature Stratification and Turnovers

Ponds and Shallow Lakes Temperature and dissolved oxygen remains about the same from top to bottom Temperature and dissolved oxygen remains about the same from top to bottom Water is easily mixed by the wind Water is easily mixed by the wind Photosynthesis and plant growth can occur from top to bottom (since light can penetrate all the way down) Photosynthesis and plant growth can occur from top to bottom (since light can penetrate all the way down)

Deep Lakes Water temperature and dissolved oxygen levels can remain same from top to bottom layers in the winter Water temperature and dissolved oxygen levels can remain same from top to bottom layers in the winter During warm summer months, layers form During warm summer months, layers form The surface if warmed up by the sun The surface if warmed up by the sun Denser, colder water remains below it Denser, colder water remains below it Doesn’t get mixed by the wind Doesn’t get mixed by the wind

Fall Turnover

Effects of Turnovers Mixing of once layered water returns oxygen levels to the deep areas. Mixing of once layered water returns oxygen levels to the deep areas. Areas in the south have one turnover per year in the fall. Areas in the south have one turnover per year in the fall. In the north, lakes become stratified in the summer and the winter (because ice forms on the surface, causing inverse stratification). Thus, there are two turnovers (fall and spring). In the north, lakes become stratified in the summer and the winter (because ice forms on the surface, causing inverse stratification). Thus, there are two turnovers (fall and spring).

Stratification Zones During summer months increased sunlight and warm winds heat the surface water trapping colder water on the bottom. During summer months increased sunlight and warm winds heat the surface water trapping colder water on the bottom. Differences in the densities of warm and cold water resist mixing by wind Differences in the densities of warm and cold water resist mixing by wind Stratification creates three different zones: Stratification creates three different zones: Epilimnion Epilimnion Metalimnion Metalimnion Hypolimnion Hypolimnion

Zones of Stratification Three distinct layers form in deep lakes during the summer months: Three distinct layers form in deep lakes during the summer months: Epilimnion Epilimnion Metalimnion Metalimnion Hypolimnion Hypolimnion

Epilimnion Warmest zone near the surface Warmest zone near the surface Circulates freely with varying temperatures according to location on the globe Circulates freely with varying temperatures according to location on the globe Wind and currents mix surface water Wind and currents mix surface water Most organisms found in this layer Most organisms found in this layer Area of greatest productivity Area of greatest productivity Greatest light penetration Greatest light penetration Greatest oxygen content Greatest oxygen content

Metalimnion Middle layer Middle layer Steep declines in temperature (area of the thermocline) Steep declines in temperature (area of the thermocline) Temp. decreases 1 o C per meter of depth Temp. decreases 1 o C per meter of depth

Hypolimnion Third layer Third layer Deep and cold with little to no temperature change Deep and cold with little to no temperature change Low oxygen due to few or no plants Low oxygen due to few or no plants Little to no mixing by wind Little to no mixing by wind Bottom-dwelling organisms and bacteria feed on organic matter and further deplete the oxygen Bottom-dwelling organisms and bacteria feed on organic matter and further deplete the oxygen Little or no light penetration Little or no light penetration

Lets Review

What is an example of a lotic system? What is an example of a lotic system?

What is an example of a lentic system? What is an example of a lentic system?

The Littoral, Limnetic, Profundal, and Benthic zones are all categorized based on what? The Littoral, Limnetic, Profundal, and Benthic zones are all categorized based on what?

Oligotrophic and eutrophic lakes are classified according to what? Oligotrophic and eutrophic lakes are classified according to what?

Name one example of a habitat that can be found in a flowing river. Name one example of a habitat that can be found in a flowing river.

Name one example of a habitat that can be found in a lake. Name one example of a habitat that can be found in a lake.

Where is the water going from and coming to in a gaining stream? Where is the water going from and coming to in a gaining stream?

Where is the water coming from and going to in a losing stream? Where is the water coming from and going to in a losing stream?

What two factors are most important in creating an oxbow lake from a meandering river? What two factors are most important in creating an oxbow lake from a meandering river?

What is the difference between a riffle and a run? What is the difference between a riffle and a run?

Stratification in lakes in the south occurs when? Stratification in lakes in the south occurs when?

When do turnovers occur in northern lakes that freeze over? When do turnovers occur in northern lakes that freeze over?

What is the riparian zone? What is the riparian zone?

What process forms sand bars? What process forms sand bars?

The three types of streams (ephemeral, perennial, and intermittent) are categorized based on what? The three types of streams (ephemeral, perennial, and intermittent) are categorized based on what?

The epilimnion, metalimnion, and hypolimnion zones are categorized based on what? The epilimnion, metalimnion, and hypolimnion zones are categorized based on what?

Depositional and Erosional zones in lotic systems are based on what? Depositional and Erosional zones in lotic systems are based on what? The rate of the water flow The rate of the water flow