Aquatic Biodiversity

Aquatic BiodiversityChapter 8Miller and Spoolman (2010)Core Why Should We Care about Coral Reefs?Coral reefs form in clear, warm coastal waters of the tropics and subtropics.Among the oldest, most diverse, and most productive ecosystems.Formed by massive colonies of tiny animals called polyps.Secrete crust of limestone (CaCO3) around their soft bodies.Elaborate network of crevices, ledges, and holes.Symbiosis with Zooxanthellae, which live in the tissues of polyps.Coral reefs occupy only 0.2% of the ocean floor, but provide important ecological and economic services.Moderate atmospheric temperaturesAct as natural barriers protecting coasts from erosion (protect 15% of worlds coastline)Provide habitatsSupport fishing and tourism businessesProvide jobs and building materialsStudied and enjoyedDegradation and decline15% of coral reefs destroyedAnother 20% damaged by coastal development, pollution, overfishing, warmer oceansCoral bleachingIncreasing ocean acidity

Decline of coral reefs should serve as a warning about threats to the health of the oceans, which provide crucial ecological and economic sevices.

Figure 8.1A healthy coral reef in the Red Sea covered by colorful algae (left) and a bleached coral reef that has lost most of its algae (right) because of changes in the environment (such as cloudy water or high water temperatures). With the colorful algae gone, the white limestone of the coral skeleton becomes visible. If the environmental stress is not removed and no other alga species fill the abandoned niche, the corals die. These diverse and productive ecosystems are being damaged and destroyed at an alarming rate.

8-1 What Is the General Nature of Aquatic Systems? Concept 8-1A Saltwater and freshwater aquatic life zones cover almost three-fourths of the earths surface with oceans dominating the planet.

Concept 8-1B The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food and availability of light and nutrients necessary for photosynthesis. Figure 8.2The ocean planet. The salty oceans cover 71% of the earths surface. Almost all of the earths water is in the interconnected oceans, which cover 90% of the planets mostly ocean hemisphere (left) and half of its landocean hemisphere (right). Freshwater systems cover less than 2.2% of the earths surface (Concept 8-1A).

Most of the Earth Is Covered with WaterGlobal ocean is single continuous body of water divided into four large areas.AtlanticPacificArcticIndian

Freshwater makes up less than 2.2% of earths surface.Aquatic equivalents of biomes are called aquatic life zones.Distribution of many aquatic organisms is determined in large part by the waters salinity. aquatic life zones are classified into two major types:Saltwater, or marine (oceans, estuaries, coastal wetlands, shorelines, coral reefs, and mangrove forests)Freshwater (lakes, rivers, streams, and inland wetlands) Aquatic systems play vital roles in the earths biological productivity, climate, biogeochemical cycles, and biodiversity, and they provide us with fish, shellfish, minerals, recreation, transportation routes, and many other economically important goods and services.Figure 8.3Natural capital: distribution of the worlds major salt water oceans, coral reefs, mangroves, and freshwater lakes and rivers. Question: Why do you think most coral reefs lie in the southern hemisphere?

Most Aquatic Species Live in Top, Middle, or Bottom Layers of WaterMajor types of aquatic organismsPlankton driftersPhytoplanktonZooplanktonUltraplankton Photosynthetic bacteria may be responsible 70% of PP near ocean surface

Nekton swimmers

Benthos bottom dwellers

Decomposers

Key factors that determine the distribution of organisms in an aquatic life zoneTemperatureDissolved oxygen contentAvailability of foodAvailability of light and nutrients needed for photosynthesis in the euphotic, or photic, zone

Depth of euphotic zone in lakes and oceans can be reduced by turbidity cloudiness caused by algal blooms or excessive silt.Excessive nutrient loading cultural eutrophicationClearing land causes erosion and silt with runoff

In shallow systems: open streams, lake edges, and ocean shorelines, nutrients are usually available

In most areas of open ocean, nitrates, phosphates, iron, and other nutrients are in short supply limits NPP.

8-2 Why Are Marine Aquatic Systems Important? Concept 8-2 Saltwater ecosystems are irreplaceable reservoirs of biodiversity and provide major ecological and economic services.

Oceans Provide Important Ecological and Economic ResourcesEnormously valuable ecological and economic services: estimated at $12 trillion annually (Figure 8-4)Oceans still poorly understood.Huge reservoirs of biodiversityMany ecosystem typesVariety of species, genes, and biological and chemical processesImportant for sustaining life.Marine life is found in three major life zones: coastal, open sea, and ocean bottom (Figure 8-5).

Figure 8.4Major ecological and economic services provided by marine systems (Concept 8-2). Question: Which two ecological services and which two economic services do you think are the most important? Why?

Figure 8.5Natural capital: major life zones and vertical zones (not drawn to scale) in an ocean. Actual depths of zones may vary. Available light determines the euphotic, bathyal and abyssal zones. Temperature zones also vary with depth, shown here by the red curve. Question: How is an ocean like a rain forest? (Hint: see Figure 7-17, p. 156.)

Coastal zoneWarm, nutrient rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf.< 10% of worlds ocean area but contains 90% of marine speciesMost commercial fisheriesMost ecosystemsestuaries, coastal wetlands, mangrove forests, and coral reefshave high NPP. ample supplies of sunlight and plant nutrients, which come from land.

Estuaries and Coastal Wetlands Are Highly ProductiveLife in these coastal ecosystems is harshSignificant daily and seasonal changes in Tidal and river flows, temperature, salinity and runoff of pollutants such as eroded sediments and chemicals form land.May be composed of only a few plant species that can withstand rapidly changing environmental factors, athough such species are highly productive.EstuariesWhere rivers meet the seaPartially enclosed bodies of water where sea water mixes with freshwater as well as nutrients and pollutants from streams, rivers, and runoff from land (Figure 8-6).

Figure 8.6View of an estuary from space. The photo shows the sediment plume (turbidity caused by runoff) at the mouth of Madagascars Betsiboka River as it flows through the estuary and into the Mozambique Channel. Because of its topography, heavy rainfall, and the clearing of forests for agriculture, Madagascar is the worlds most eroded country.

Coastal wetlandsCoastal land areas covered with water all or part of the yearRiver mouths, inlets, bays, sounds, salt marshes (Figure 8-7) in temperate zones, and mangrove forests in tropical zones.Some of the earths most productive ecosystems high nutrient inputs, rapid circulation from tidal flows, and ample sunlight penetrates shallow water.Seagrass bedsAnother component of coastal marine biodiversity.60 species of plants that grow in shallow marine and estuarine areas along most continental shorelines.Support a variety of speciesStabilize shorelines and reduce wave impacts.Figure 8.7Some components and interactions in a salt marsh ecosystem in a temperate area such as the United States. and decomposers. The photo shows a salt marsh in Peru.

Mangrove forestsMagroves69 tree species that can grow in salt water (Figure 8-8)Tropical equivalent of salt marshes.70% of gently sloping, sandy and silty coastlines in tropical and subtropical regions.Provide important ecological and economic servicesMaintain water qualityFood, habitat, and nursery sites for aquatic and terrestrial speciesReduce storm damage and coastal erosionHistorically, sustainably supplied timber and fuelwood to coastal communitiesBetween 1980 and 2005, and estimated 20% of mangrove forests were lost mostly due to coastal development. polluted drinking water, salt water intrusion reduced protection from storms reduced biodiversityFigure 8.8Mangrove forest in Daintree National Park in Queensland, Australia. The tangled roots and dense vegetation in these coastal forests act like shock absorbers to reduce damage from storms and tsunamis. They also provide a highly complex habitat for a diversity of invertebrates and fishes.

Rocky and Sandy Shores Host Different Types or OrganismsMoon and sun cause ocean tides that rise and fall every 6 hoursIntertidal zone the area of shoreline between low and high tides.Organisms here are adapted to extreme conditions: waves, varying water levels, varying salinityOrganism hold on to something, dig in, and/or hide in protective shellsRocky shores (Figure 8-9, top)Pounded by wavesOrganisms occupy different niches in response to daily and seasonal changes in temperature, water flows, and salinity.

Figure 8.9, TopLiving between the tides. Some organisms with specialized niches found in various zones on rocky shore beaches.

Sandy shores or barrier beaches (Figure 8-9, bottom)Support other types of organisms; most survive by burrowing, digging, and tunneling in sandShorebirds have specialized feeding niches (Figure 4-13, p. 93)Barrier Islands (Figure 8-10) low, narrow, sandy islands that form offshore, parallel to some coastlines.South Padre IslandUndisturbed barrier beaches generally have one or more rows of natural sand dunes in which the sand is held in place by plant roots.First line of defense against storm surges and heavy wave action from storms.Such areas are valuable for real estate development.

Figure 8.9, BottomLiving between the tides. Some organisms with specialized niches found in various zones on barrier or sandy beaches.

Figure 8.10Primary and secondary dunes on gently sloping sandy barrier beaches help protect land from erosion by the sea. The roots of grasses that colonize the dunes hold the sand in place. Ideally, construction is allowed only behind the second strip of dunes, and walkways to the ocean beach are built so as not to damage the dunes. This helps to preserve barrier beaches and to protect buildings from damage by wind, high tides, beach erosion, and flooding from storm surges. Such protection is rare in some coastal areas because the short-term economic value of oceanfront land is considered much higher than its long-term ecological value. Rising sea levels from global warming may put many barrier beaches under water by the end of this century. Question: Do you think that the long and short-term ecological values of oceanfront dunes outweigh the short-term economic value of removing them for coastal development? Explain.

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Coral Reefs Are Amazing Centers of BiodiversityMarine equivalent of tropical rain forests

Habitats for one-fourth of all marine species

Figure 8.11Natural capital: some components and interactions in a coral reef ecosystem.

The Open Sea and Ocean Floor Host a Variety of SpeciesOpen sea is marked by a sharp increase in depth at the edge of the continental shelf.Divided into three vertical zones based on light penetration and temperature (Figure 8-5).Euphotic zoneBrightly lit upper zone where phytoplankton carry out some 40% of the worlds photosynthesis.Nutrient levels are low, except at upwellings.DO levels are highLarge fast-swimming predatory fish: swordfish, sharks, and bluefin tuna.

Bathyal zoneDimly lit middle zone does not contain photosynthesizing producers.Zooplankton and smaller fishes which migrate to feed at the surface at night.Abyssal zoneDark and very cold, with little DOAbundant with life even though there is no photosynthesis to support it.Marine snowDeposit feeders such as wormsFilter feeders such as clams and spongesAvg. NPP per unit area is low, but make larger overall contribution to earths overall NPP.NPP, higher at upwellings8-3 How Have Human Activities Affected Marine Ecosystems? Concept 8-3 Human activities threaten aquatic biodiversity and disrupt ecological and economic services provided by saltwater systems.

Human Activities Are Disrupting and Degrading Marine SystemsA four year study by U.S. National Center for Ecological Analysis and SynthesisExamined 17 different human activities41% of the worlds oceans, heavily affectedNo area left completely untouchedIn 2006, 45% of worlds population lives near the coast. destruction and degradation of natural resources and services (Figure 8-4).Projected to be 80% in 2040

Major threats to marine systemsCoastal developmentRunoff of non-point source pollution: fertilizers, pesticides and livestock wastePoint source pollution such as sewage from cruise ships and oil tanker spillsHabitat destruction from coastal development and trawler fishing

OverfishingInvasive speciesHuman enhanced climate change causing sea level rise: destroys coastal habitats, coastal cities and coral reefsClimate change: warming oceans and decreasing pHPollution and degradation of coastal wetlands and estuaries

Case Study: The Chesapeake Bayan Estuary in Trouble

Figure 8.13Chesapeake Bay, the largest estuary in the United States, is severely degraded as a result of water pollution from point and nonpoint sources in six states and from the atmospheric deposition of air pollutants.Case Study: The Chesapeake Bayan Estuary in TroubleLargest estuary in the USPolluted since 1960 Population increased significantly to 16.6 million in 2007The estuary receives wastes from point and nonpoint sourcesBay has become a huge pollution sink; only 1% of waste is flushed to the Atlantic OceanPhosphate and nitrate levels too high Large algal blooms and oxygen depletion60% of phosphates come from point sources60% of nitrates come from non-point sources

Overfishing of oysters, crabs, and important fishesCombined with pollution and disease, has caused populations to fall since 1960.1983, U.S. Implemented the Chesapeake Bay ProgramIntegrated coastal management, including citizens groups, communities, state legislatures, and federal governmentLand-use regulations in six states to reduce ag and urban runoffBanned phosphate detergentsClosely monitoring industrial dischargesRestoration of wetlands and sea grassesNative oyster problemChesapeake Bay Program has achieved some successBetween 1985 and 2000Phosphorus, -27%Nitrogen, -16%Sea grasses coming back

There has been a drop in federal funding

8-4 Why Are Freshwater Ecosystems Important?Concept 8-4 Freshwater ecosystems provide major ecological and economic services and are irreplaceable reservoirs of biodiversity.

Water Stands in Some Freshwater Systems and Flows in OthersStanding (lentic) bodies of freshwaterLakesPondsInland wetlands

Flowing (lotic) systems of freshwaterStreamsRivers

Cover only 2.2% of earths surface but provide important ecological and economic Figure 8.14Major ecological and economic services provided by freshwater systems (Concept 8-4). Question: Which two ecological services and which two economic services do you think are the most important? Why?

Formation of lakesLarge natural bodies of standing freshwater formed when precipitation, runoff, streams or groundwater fills depressions in the earths surface.

Four zones based on depth and distance from shoreLittoral zoneLimnetic zoneProfundal zoneBenthic zone

Figure 8.15Distinct zones of life in a fairly deep temperate zone lake. Question: How are deep lakes like tropical rain forests? (Hint: See Figure 7-17, p. 156)

Some Lakes Have More Nutrients Than Others

Figure 8.16The effect of nutrient enrichment on a lake. Crater Lake in the U.S. state of Oregon (left) is an example of an oligotrophic lake that is low in nutrients. Because of the low density of plankton, its water is quite clear. The lake on the right, found in western New York State, is a eutrophic lake. Because of an excess of plant nutrients, its surface is covered with mats of algae and cyanobacteria.Some Lakes Have More Nutrients Than OthersOligotrophic lakesLow levels of nutrients and low NPP

Eutrophic lakesHigh levels of nutrients and high NPP

Mesotrophic lakes

Cultural eutrophication leads to hypereutrophic lakes

Freshwater Streams and Rivers Carry Water from the Mountains to the Oceans Surface water

Runoff

Watershed, or drainage basin the land area that delivers runoff, sediment, and dissolved substances to a stream,

Three aquatic life zones in the downhill flow of waterSource zoneTransition zoneFloodplain zone

Figure 8.17Three zones in the downhill flow of water: source zone containing mountain (headwater) streams; transition zone containing wider, lower-elevation streams; and floodplain zone containing rivers, which empty into the ocean.

Source zoneShallow, cold, clear, and swiftly flowingLarge amounts of DOLack nutrients, not very productiveNutrients come from organic matter that falls into the river.Fauna: cold-water fishes and other animals adapted for fast moving water.Flora: algae and mosses attached to rocksTransition ZoneHeadwater streams merge to form wider, deeper, and warmer streamsSlower flowing, less DO, and can be turbidCool- and warm-water fishes, and more producers.Flood Plain ZoneSteams join into wider and deeper rivers that flow across broad flat valleys.Water higher in temp, less DOProducers such as algae, cyanobacteria, and rooted aquatic plants along the shores.Water, muddy and high concentration of suspended particulate matter (silt).Main channels support distinct fishes (carp, catfish), backwaters support fish similar to lakesAt mouth of river, may divide into many channels as it flows through the delta, built up by deposits of silt, and coastal wetlands and estuaries.Case Study: Dams, Deltas, Wetlands, Hurricanes, and New OrleansFigure 8.18Much of the U.S. city of New Orleans, Louisiana, was flooded by the storm surge that accompanied Hurricane Katrina, which made landfall just east of the city on August 29, 2005. When the surging water rushed through the Mississippi River Gulf Outlet, a dredged waterway on the edge of the city, it breached a floodwall, and parts of New Orleans were flooded with 2 meters (6.5 feet) of water within a few minutes. Within a day, floodwaters reached a depth of 6 meters (nearly 20 feet) in some places; 80% of the city was under water at one point. The hurricane killed more than 1,800 people, and caused more than $100 billion in damages, making it the costliest and deadliest hurricane in the U.S. history. In addition, a variety of toxic chemicals from flooded industrial and hazardous waste sites, as well as oil and gasoline from more than 350,000 ruined cars and other vehicles, were released into the stagnant floodwaters. After the water receded, parts of New Orleans were covered with a thick oily sludge.Figure 8.18Much of the U.S. city of New Orleans, Louisiana, was flooded by the storm surge that accompanied Hurricane Katrina, which made landfall just east of the city on August 29, 2005. When the surging water rushed through the Mississippi River Gulf Outlet, a dredged waterway on the edge of the city, it breached a floodwall, and parts of New Orleans were flooded with 2 meters (6.5 feet) of water within a few minutes. Within a day, floodwaters reached a depth of 6 meters (nearly 20 feet) in some places; 80% of the city was under water at one point. The hurricane killed more than 1,800 people, and caused more than $100 billion in damages, making it the costliest and deadliest hurricane in the U.S. history. In addition, a variety of toxic chemicals from flooded industrial and hazardous waste sites, as well as oil and gasoline from more than 350,000 ruined cars and other vehicles, were released into the stagnant floodwaters. After the water receded, parts of New Orleans were covered with a thick oily sludge.54Case Study: Dams, Deltas, Wetlands, Hurricanes, and New OrleansCoastal deltas, mangrove forests, and coastal wetlands: natural protection against storms

Dams and levees reduce sediments in deltas: significance?

New Orleans, Louisiana, and Hurricane Katrina: August 29, 2005

Global warming, sea rise, and New Orleans

Figure 8.18Much of the U.S. city of New Orleans, Louisiana, was flooded by the storm surge that accompanied Hurricane Katrina, which made landfall just east of the city on August 29, 2005. When the surging water rushed through the Mississippi River Gulf Outlet, a dredged waterway on the edge of the city, it breached a floodwall, and parts of New Orleans were flooded with 2 meters (6.5 feet) of water within a few minutes. Within a day, floodwaters reached a depth of 6 meters (nearly 20 feet) in some places; 80% of the city was under water at one point. The hurricane killed more than 1,800 people, and caused more than $100 billion in damages, making it the costliest and deadliest hurricane in the U.S. history. In addition, a variety of toxic chemicals from flooded industrial and hazardous waste sites, as well as oil and gasoline from more than 350,000 ruined cars and other vehicles, were released into the stagnant floodwaters. After the water receded, parts of New Orleans were covered with a thick oily sludge.55Figure 8.19Projection of how a 1-meter (3.3-foot) rise in sea level from global warming by the end of this century would put New Orleans and much of Louisianas current coast under water. (Used by permission from Jonathan Overpeck and Jeremy Weiss, University of Arizona)

Freshwater Inland Wetlands Are Vital SpongesInland wetlands are lands covered with freshwater all or part of the time (excluding lakes, reservoirs, and streams).Marshes, dominated by grasses and reedsSwamps, dominated by trees and shrubsPrairie potholes, carved out by ancient glaciersFloodplainsActic tundra

Some wetlands are permanent, some are seasonalWetlands are highly productiveHabitat for game fishes, muskrats, otters, beavers, migratory waterfowl, and many other birds species.Ecological and economic servicesFilter and degrade toxic wastesReduce flooding and erosionHelp to replenish streams and recharge groundwater aquifersBiodiversityFood and timberRecreation areas

8-5 How Have Human Activities Affected Freshwater Ecosystems?Concept 8-5 Human activities threaten biodiversity and disrupt ecological and economic services provided by freshwater lakes, rivers, and wetlands.Human Activities Are Disrupting and Degrading Freshwater SystemsHuman activities affect freshwater ecosystems in four major ways:Dams and canals Alter and destroy terrestrial and aquatic habitatsReduce water flow and sedimentation in coastal deltas and estuaries.Flood control levees and dikesDisconnect rivers from their floodplainsDestroy aquatic habitatsAlter or reduce the function of wetlandsCities and farms add pollutants and excess nutrients to streams and lakesCultural eutrophicationDraining or filling in wetlandsCase Study: Inland Wetland Losses in the United StatesMore than half of inland wetlands in continental U.S. lost since 1600s80% destroyed to grow crops20% lost to mining, forestry, oil and gas extraction, highways and urban development.Has caused increased flood and drought damage in the U.S.Other countries tooFor example, 80% of all wetlands in Germany and France have been destroyed.