1. Aquatic Ecology

2. Ocean Notes given in class: Estuary – definition & importance
Mangroves
Other oceanic zones

3. Lakes/Ponds
Littoral Zone:
Limnetic Zone:
Profundal Zone:

4. Thermal Stratification
Lakes are divided into layers based on their temperatures.
The higher temperature, the less dense the water is
Warmer water stays on top, colder water sinks to the bottom

5. Thermal Stratification
Mixed Layer – high in DO, low in nutrients
Thermocline – acts as a barrier
Deep water – low DO, high in nutrients

6. Fall Turnover
As the temperatures begin to drop, the surface layer becomes more dense, and it sinks to the bottom. This mixing brings nutrients from the bottom up to the surface and sends oxygen to the bottom.

7. Spring Turnover
As top water warms and ice melts, it sinks through and below the cooler, less dense water, sending oxygen down and nutrients up.

8. Rivers
Watershed
Eutrophication
Dams

9. Freshwater Streams and Rivers: From the Mountains to the Oceans
Water flowing from mountains to the sea creates different aquatic conditions and habitats.
Figure 6-17

10. Headwater Stream Characteristics
A narrow zone of cold, clear water that rushes over waterfalls and rapids. Large amounts of oxygen are present. Fish are also present. Ex. trout.

11. Downstream Characteristics
Slower-moving water, less oxygen, warmer temperatures, and lots of algae and cyanobacteria.

12. USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER
Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.

13. Provides water for year-round irrigation of cropland
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation
Provides water for drinking
Downstream cropland and estuaries are deprived of nutrient-rich silt
Reservoir is useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Figure 14.13
Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?
Downstream flooding is reduced
Migration and spawning of some fish are disrupted
Fig a, p. 317

14. Powerlines Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317
Figure 14.13
Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?
Fig b, p. 317

15. Colorado River Basin
These are dams & reservoirs that feed from the Colorado River all the way to San Diego, LA, Palm Springs, Phoenix & Mexico. So far has worked because they haven’t withdrawn their full allocations.

16. The Colorado River Basin
Figure 14-14

17. UPPER BASIN LOWER BASIN Gulf of California
IDAHO
WYOMING
Dam
Aqueduct or canal
Salt Lake City
Upper Basin
Denver
Lower Basin
Grand Junction
UPPER BASIN
UTAH
Colorado River
NEVADA
Lake Powell
COLORADO
Grand Canyon
Glen Canyon Dam
Las Vegas
NEW MEXICO
CALIFORNIA
Boulder City
Los Angeles
ARIZONA
Albuquerque
Figure 14.14
Natural capital degradation: the Colorado River basin. The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states. Two large reservoirs—Lake Mead behind the Hoover Dam and Lake Powell behind the Glen Canyon Dam (Figure 14-15)—store about 80% of the water in this basin.
LOWER BASIN
Palm Springs
100 mi.
Phoenix
San Diego
Yuma
150 km
Tucson
Mexicali
All-American Canal
Gulf of California
MEXICO
Fig , p. 318

18. Case Study: The Colorado Basin – an Overtapped Resource
The Colorado River has so many dams and withdrawals that it often does not reach the ocean.
14 major dams and reservoirs, and canals.
Water is mostly used in desert area of the U.S.
Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).

19. Case Study: The Colorado Basin – an Overtapped Resource
Lake Powell, is the second largest reservoir in the U.S.
It hosts one of the hydroelectric plants located on the Colorado River.
Figure 14-15

20. Case Study: China’s Three Gorges Dam
There is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages.
The dam will be 2 kilometers long.
The electric output will be that of 18 large coal-burning or nuclear power plants.
It will facilitate ship travel reducing transportation costs.
Dam will displace 1.2 million people.
Dam is built over seismatic fault and already has small cracks.

21. Dam Removal
Some dams are being removed for ecological reasons and because they have outlived their usefulness.
In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S.
The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams.
Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

22. Eutrophication Too Much of a Good Thing!!
Excess nitrates and phosphates are released into a river (ranches, farms, water treatment plants, etc…)
These excess nutrients reach the lake or ocean (nutrients = euphotic = good!)
Excess nutrients are VERY good for algae
Algal growth increases to the point that an algal bloom forms over the water
Much less light can now get through this algal bloom
Plants die
Herbivores die
Carnivores die/leave the area
FYI – this is a VERY important concept

23. Core Case Study: Lake Victoria
Lake Victoria has lost their endemic fish species to large introduced predatory fish.
Figure 12-1

24. Core Case Study: A Biological Roller Coaster Ride in Lake Victoria
Reasons for Lake Victoria’s loss of biodiversity:
Introduction of Nile perch.
Lake experienced algal blooms from nutrient runoff.
Invasion of water hyacinth has blocked sunlight and deprived oxygen.
Nile perch is in decline because it has eaten its own food supply.

25. Aquifers Underground water source
Aquifers do recharge, but often the recharge rate is much less than the depletion rate
Aquifer depletion has the following negative consequences:
Loss of water source
Salt water may seep into aquifer
Loss of native species
Ground collapse

26. Aquifers An aquifer is an underground water sources
Aquifers have a recharge rate
Usually the recharge rate is much slower than the depletion rate
Running out of water!

27. Other Effects of Groundwater Overpumping
Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater.
Figure 14-10

28. Groundwater Depletion: A Growing Problem
Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S.
The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).
Figure 14-8

29. Ogallala Aquifer
This is the world’s largest known aquifer, and fuels agricultural regions in the U.S. It extends from South Dakota to Texas. It’s essentially a non-renewable aquifer from the last ice age with an extremely slow recharge rate. In some cases, water is pumped out 8 to 10 times faster than it is renewed. Northern states will still have ample supplies, but for the south it’s getting thinner. It is estimated that ¼ of the aquifer will be depleted by 2020.

30. Agriculture Agriculture is the LEADING cause of wasted water.
Solution – more efficient irrigation techniques
Hurdles – expense, education

31. (efficiency 60% and 80% with surge valves)
Drip irrigation
(efficiency 90–95%)
Gravity flow
(efficiency 60% and 80% with surge valves)
Figure 14.18
Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation.
Center pivot
(efficiency 80%–95%)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Water usually comes from an aqueduct system or a nearby river.
Fig , p. 325

32. Fishing
Deadliest Catch

33. Fishing Problems & Techniques
The major decline in the worldwide catch of fish since 1990 is because of over-fishing.
By-catch- fish or animals that were not meant to be caught.

34. Overfishing and Extinction: Gone Fishing, Fish Gone
About 75% of the world’s commercially valuable marine fish species are over fished or fished near their sustainable limits.
Big fish are becoming scarce.
Smaller fish are next.
We throw away 30% of the fish we catch.
We needlessly kill sea mammals and birds.

35. Deep sea aquaculture cage Fish caught by gills
Trawler fishing
Fish farming in cage
Spotter airplane
Sonar
Purse-seine fishing
Trawl flap
Trawl lines
Fish school
Trawl bag
Drift-net fishing
Long line fishing
Float
Buoy
Figure 12.A
Natural capital degradation: major commercial fishing methods used to harvest various marine species. These methods have become so effective that many fish species have become commercially extinct.
Lines with hooks
Deep sea aquaculture cage
Fish caught by gills
Fig. 12-A, p. 255

36. Trawler Fishing
Catches shrimp, shellfish, flounder and other anials that live on the ocean floor
Drags a funnel shaped net along the ocean floor, weighted down with chains or metal plates
Some nets are large enough to hold 12 jumbo jets!!

37. Purse Seines

38. Purse Seines
A large purse-like net is put into the ocean and is then closed like a drawstring purse to trap the fish.
Tuna is a fish typically caught in purse seines
Dolphins are a by-catch of purse seines

39. Long-line fishing
Lines are put out that can be up to 80 miles long w/ thousands of baited hooks on them. These are left out free-floating for days and then the boat comes back and picks them up.
Pilot whales, dolphins, sea turtles, and birds are by-catch of this technique.
Deadliest Catch

40. Drift-net fishing
Each net hangs as much as 50 feet below the surface and up to 34 miles long.
Anything that comes into contact w/ these nearly invisible nets are entangled.
This leads to overfishing
Many unwanted fish and marine mammals, turtles and seabirds are caught.

41. Regulations on Fishing
Marine and mammal protection act - provides for protection and conservation of marine mammals
Magnuson Act- Sets quotas, size limits and seasons for fishing
UN Law of the Seas – allows countries to establish fishing quotas
Marine Sanctuaries Act- provides protected habitat for marine organisms

42. Other human impacts on water
Salinazation (Aral Sea)
Deforestation
Development (florida everglades)

43. TOO MUCH WATER
Human activities have contributed to flood deaths and damages.
Figure 14-23

44. Evapotranspiration decreases Roads destabilize hillsides
After Deforestation
Tree plantation
Evapotranspiration decreases
Roads destabilize hillsides
Ranching accelerates soil erosion by water and wind
Winds remove fragile topsoil
Gullies and landslides
Agricultural land is flooded and silted up
Figure 14.23
Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber and fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.”
Heavy rain leaches nutrients from soil and erodes topsoil
Rapid runoff causes flooding
Silt from erosion blocks rivers and reservoirs and causes flooding downstream
Fig b, p. 330

45. Examples
Examples include drought and expanding deserts.

46. Overdrawing Surface Water
Lake levels drop, recreation use drops, fisheries drop, and salinization occurs. Ex. Soviet Union (Aral Sea); the inland sea drained the river that fed into it. Now it’s a huge disaster (read pg. 322 in text).
1997
1964

47. Case Study: The Aral Sea Disaster
Diverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a major ecological, economic, and health disaster.
About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared.
Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

48. Mono Lake
(like the Dead Sea) This has a huge salt concentration due to man’s draining.

49. Salinization of Irrigated Soil
Water is poured onto soil and evaporates. Over time, as this is repeated, nothing will grow there anymore.