Aquatic Ecology

Aquatic EcologyOceanNotes given in class:Estuary definition & importanceMangroves

Other oceanic zonesLakes/PondsLittoral Zone:Limnetic Zone:Profundal Zone:Lakes are divided into layers based on their temperatures.The higher temperature, the less dense the water isWarmer water stays on top, colder water sinks to the bottomThermal StratificationMixed Layer high in DO, low in nutrientsThermocline acts as a barrierDeep water low DO, high in nutrientsThermal Stratification

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.Fall TurnoverAs top water warms and ice melts, it sinks through and below the cooler, less dense water, sending oxygen down and nutrients up.Spring TurnoverRiversWatershed EutrophicationDams

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

9A narrow zone of cold, clear water that rushes over waterfalls and rapids. Large amounts of oxygen are present. Fish are also present. Ex. trout.

Headwater Stream Characteristics

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

Downstream Characteristics

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.USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER12

Fig. 14-13a, p. 317Provides water for year-round irrigation of croplandFlooded land destroys forests or cropland and displaces peopleLarge losses of water through evaporationProvides water for drinkingDownstream cropland and estuaries are deprived of nutrient-rich siltReservoir is useful for recreation and fishingRisk of failure and devastating downstream floodingCan produce cheap electricity (hydropower)Downstream flooding is reducedMigration and spawning of some fish are disrupted13Figure 14.13Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The worlds 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the worlds 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 countrys entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?

Fig. 14-13b, p. 317PowerlinesReservoirDamPowerhouseIntakeTurbine14Figure 14.13Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The worlds 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the worlds 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 countrys entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?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 havent withdrawn their full allocations.Colorado River Basin

The Colorado River BasinFigure 14-1416

Fig. 14-14, p. 318DamAqueduct or canalUpper BasinLOWER BASIN0100 mi.0150 kmLower BasinUPPER BASINIDAHOWYOMINGSalt Lake CityGrand JunctionDenverUTAHNEVADACOLORADOLake PowellLas VegasGrand CanyonGlen Canyon DamBoulder CityNEW MEXICOARIZONALos AngelesAlbuquerquePhoenixSan DiegoMexicaliYumaTucsonAll-American CanalGulf of CaliforniaMEXICOCALIFORNIAPalm SpringsColorado River17Figure 14.14Natural 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 reservoirsLake 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.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).Case Study: The Colorado Basin an Overtapped Resource18

Lake Powell, is the second largest reservoir in the U.S.It hosts one of the hydroelectric plants located on the Colorado River.Case Study: The Colorado Basin an Overtapped ResourceFigure 14-1519There is a debate over whether the advantages of the worlds 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. Case Study: Chinas Three Gorges Dam20Some 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.Dam Removal21EutrophicationToo 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 algaeAlgal growth increases to the point that an algal bloom forms over the waterMuch less light can now get through this algal bloomPlants dieHerbivores dieCarnivores die/leave the area

FYI this is a VERY important conceptLake Victoria has lost their endemic fish species to large introduced predatory fish.Core Case Study: Lake VictoriaFigure 12-1

23Reasons for Lake Victorias 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.Core Case Study: A Biological Roller Coaster Ride in Lake Victoria24AquifersUnderground water sourceAquifers do recharge, but often the recharge rate is much less than the depletion rateAquifer depletion has the following negative consequences:Loss of water sourceSalt water may seep into aquiferLoss of native speciesGround collapseAquifersAn aquifer is an underground water sourcesAquifers have a recharge rateUsually the recharge rate is much slower than the depletion rateRunning out of water!

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

27The Ogallala, the worlds largest aquifer, is most of the red area in the center (Midwest).Groundwater Depletion: A Growing ProblemAreas of greatest aquifer depletion from groundwater overdraft in the continental U.S.Figure 14-8

28This is the worlds largest known aquifer, and fuels agricultural regions in the U.S. It extends from South Dakota to Texas. Its 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 its getting thinner. It is estimated that of the aquifer will be depleted by 2020. Ogallala AquiferAgricultureAgriculture is the LEADING cause of wasted water. Solution more efficient irrigation techniquesHurdles expense, education

Fig. 14-18, p. 325Center pivotDrip irrigationGravity flow(efficiency 60% and 80% with surge valves)Above- or below-ground pipes or tubes deliver water to individual plant roots.Water usually comes from an aqueduct system or a nearby river.(efficiency 9095%)(efficiency 80%95%)Water usually pumped from underground and sprayed from mobile boom with sprinklers.31Figure 14.18Major 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.FishingDeadliest Catch

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.Fishing Problems & TechniquesAbout 75% of the worlds 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.Overfishing and Extinction: Gone Fishing, Fish Gone34

Fig. 12-A, p. 255Fish farming in cageTrawler fishingSpotter airplaneSonarTrawl flapTrawl linesPurse-seine fishingTrawl bagFish schoolDrift-net fishingLong line fishingLines with hooksFish caught by gillsDeep sea aquaculture cageFloatBuoy35Figure 12.ANatural 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.Trawler FishingCatches shrimp, shellfish, flounder and other anials that live on the ocean floorDrags a funnel shaped net along the ocean floor, weighted down with chains or metal platesSome nets are large enough to hold 12 jumbo jets!!

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 seinesDolphins are a by-catch of purse seinesPurse SeinesLines 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 CatchLong-line fishingEach 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 overfishingMany unwanted fish and marine mammals, turtles and seabirds are caught.Drift-net fishingRegulations on FishingMarine and mammal protection act - provides for protection and conservation of marine mammalsMagnuson Act- Sets quotas, size limits and seasons for fishingUN Law of the Seas allows countries to establish fishing quotasMarine Sanctuaries Act- provides protected habitat for marine organismsOther human impacts on waterSalinazation (Aral Sea)DeforestationDevelopment (florida everglades)

Human activities have contributed to flood deaths and damages.TOO MUCH WATERFigure 14-2343

Fig. 14-23b, p. 330Tree plantationRoads destabilize hillsidesEvapotranspiration decreasesRanching accelerates soil erosion by water and windWinds remove fragile topsoilAgricultural land is flooded and silted upGullies and landslidesHeavy rain leaches nutrients from soil and erodes topsoilSilt from erosion blocks rivers and reservoirs and causes flooding downstreamRapid runoff causes floodingAfter Deforestation44Figure 14.23Natural 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.Examples include drought and expanding deserts.Examples

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 its a huge disaster (read pg. 322 in text).Overdrawing Surface Water

19641997Diverting 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 seas salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

Case Study: The Aral Sea Disaster47(like the Dead Sea) This has a huge salt concentration due to mans draining.Mono Lake

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