APES_Chapter_6_Aquatic_Biodiversity - Chapter 6 Chapter...

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Unformatted text preview: Chapter 6 Chapter Aquatic Biodiversity AP Environmental Science Edinburg North High School Chapter 6: Aquatic Biodiversity Chapter Focus Questions: • What are the basic types of aquatic life zones, and what factors influence the kinds of life they contain? • What are the major types of saltwater life zones, and how do human activities affect them? • What are the major types of freshwater life zones, and how do human activities affect them? Core Case Study: Core Why Should We Care about Coral Reefs? • Coral reefs – – – Warm coastal waters Marine equivalents of tropical rainforest (Fig. 6-1a) Polyps (jellyfish relative), CaCO3, symbiotic symbiotic zooxanthellae zooxanthellae – 0.1% of world’s ocean area • Ecological and economic services – – – – – – Moderate atmospheric temperature Natural barriers protective 15% of world’s coastline Provides habitats for marine organisms Produce one-tenth of global fish catch Building materials for poor countries • Conservation – 20% of the world’s coral reefs lost to coastal 20% development, pollution, overfishing, warmer oceans, and other stresses oceans, – Another 30% will be lost in next 20-40 yr – Coral bleaching, linked to warmer water and Coral silt from land (Fig. 6-1b) silt I. Aquatic Environments I. • The Water Planet: Saltwater and Freshwater – Oceans cover 71% earth’s surface, freshwater < 1% (Fig. 6-2) – Major types of organisms determined by salinity. Major salinity – Aquatic life zones classified into two major types: • Marine, or saltwater, iincludes estuaries, coastlines, coral reefs, or saltwater ncludes coastal marshes, mangrove swamps, and oceans. coastal • Freshwater, iincludes lakes, ponds, streams, rivers, and inland ncludes wetlands. wetlands. – Distribution of the worlds major saltwater oceans, coral Distribution reefs, mangroves and freshwater lakes and rivers reefs, (Fig. 6-3) – Play vital roles in ecosystems and human Play systems systems • • • • • • • Biological productivity Climate Biogeochemical cycles Biodiversity Fisheries: fish and shellfish Oil, natural gas, and minerals Recreation and transport routes • What kinds of organisms live in aquatic life What zones? zones? – Plankton • • • Phytoplankton Zooplankton Ultraplankton – Nekton – Benthos – Decomposers • Life in Layers – Three main layers: surface, middle, and bottom – Factors that determine the distribution and Factors abundance of organisms: abundance • Temperature, light, DO, nutrients – Photosynthesis confined to upper layer, or Photosynthesis euphotic zone. euphotic • Depth depends on water clarity. – Nutrients (nitrates, phosphates, iron, and others) Nutrients more limited in open ocean. more • Upwellings (see Suppl. 10) however has high NPP. – Most deep bottom organism depend on dead Most debris that falls to the bottom. debris II. Saltwater Life Zones II. • Why should we care about the oceans? – They provide many important ecological and They economic services (Fig. 6-4). economic – We know less about the oceans and We freshwater systems than we do about the surface of the moon. surface • Further study could yield immense ecological and Further economic benefits. economic • The Coastal Zone: Where Most of the Action is – Two major life zones: coastal and open ocean ( Fig. 6-5). – Extends from high tide mark to end of continental Extends shelf. shelf • Relatively shallow, nutrient-rich • Numerous interaction with land, so easily affected by Numerous human activities. human – Only 10% of the world’s ocean area, but contains Only 90% of marine species 90% – Site of most large commercial fisheries – High NPP because of ample nutrients and High sunlight. sunlight. • Estuaries and Coastal Wetlands: Centers of Estuaries Productivity Productivity – Estuary – area where rivers meet the sea • Seawater mixes with freshwater along with nutrients Seawater and pollutants (Fig. 6-6) and – Coastal wetlands – coastal land areas covered with water all or part of the year with • River mouths, inlets, bays, sounds, and salt marshes ( Fig. 6-7; iin temperate areas) and mangrove forests in n tropical zones (in tropical areas). tropical • Significant daily and seasonal changes in tidal and Significant river flows, and land runoff of sediment and other pollutants pollutants – Estuaries and coastal wetlands very productive – Mangrove forests are the tropical equivalents of Mangrove salt marshes. salt • 70 % of gently sloping sandy and silty coastlines in 70 tropical and subtropical regions. tropical • Mangrove trees can grow in saltwater (Fig. 6-8). • Systems provide important ecological and economic Systems services services – – – – Filter toxic pollutants, excess nutrients, and sediments. Reduce storm damage Provide food, habitats, and nursery sites Intact mangroves worth $200,000-$900,000/km2 • Based on sustainable fishing and fuel wood use; does Based not include ecological services. not • 10-45x more worth than when cleared for aquaculture • Protecting mangrove forest cost only $1000/km2 • More than a third of the world’s have been destroyed. – For shrimp farms, crops, and coastal development – Bangladesh and the Philippines have lost almost ¾ • Rocky and Sandy Shores: Living with the Rocky Tides Tides – Gravitational pull from the sun and the moon Gravitational causes tides to rise and fall every 6 hours (depending). (depending). – Intertidal zone – area of the shoreline between low and high tides. between – For an organism, lots of physical and For physiological stress. physiological • Crashing waves • High and low tides – periodic immersion and High emersion emersion • Changing levels of salinity – Rocky shores (Fig 6-9a) • Are pounded by waves • Numerous pools and other niches in the intertidal Numerous zone zone • Remarkable number of niches in response to daily Remarkable and seasonal changes in and – – – Temperature Water flow Salinity Salinity – Barrier beaches, or Sandy Shores (Fig. 6-9b) or Sandy • Gently sloping shores • Many critters burrow into the sand • Variety of shorebirds with specialized feeding niches Variety (Fig. 4-8) (Fig. – Barrier Islands (Fig. 6-10) • Low, narrow, sandy islands that form offshore from Low, a coastline. coastline. • Prime targets for development – Examples: Atlantic City, NJ; Palm Beach, FL; South Examples: Padre Island, TX Padre – Development prone to destruction from mother nature • Flooding, beach erosion, and hurricanes – According to climate models many of the world’s barrier According islands may be under water by end of century. islands • Undisturbed barrier islands – One or more rows of sand dunes – Dunes act as a line of defense against storm surges – Development disrupts these natural barrier island Development formations formations • “People inaccurately call these human-influenced People events ‘natural disasters’.” events • Threats to Coral Reefs: Increasing Stresses – Coral reefs found in clear,warm tropical and Coral subtropical waters subtropical • Thrive in clear, warm, fairly shallow water of constant Thrive salinity. salinity. • Temperature range (18–30 oC); bleaching can be 30 C); triggered with an increase of just one degree. triggered – One-fourth of all marine species (Fig. 6-11) • Biodiversity can be reduced by: – – – – Severe storms Freshwater floods Invasion of predatory fish Human activities (Fig. 6-12) – Loss of Coral Reefs • 20% are so damaged that they are unlikely to 20% recover recover • By 2050, 30-50% could be lost due to climate By change, habitat loss, pollution, and overfishing change, • Only 300 of 6000 reefs are protected (at least on Only paper) paper) – Ecology and Economy 21 • Worth an estimated $100,000-$600,000 km--2 y--1 from small-scale sustainable fishing, tourism, and pet trade. trade. – Does not include ecological services – If included, much cheaper to protect than to use them If unsustainably unsustainably – There is evidence that coral reefs can recover. • • protection by restricted fishing reducing inputs of nutrients and other pollutants • Biological Zone in the Open Ocean: Light Biological Rules Rules – Open sea – at edge of continental shelf. – Divided into three vertical zones depending on Divided light availability (Fig. 6-5) light – Euphotic zone – brightly lit upper zone • • • • Phytoplankton carry out photosynthesis Nutrients low except at upwellings DO high Populated with fast-swimming predatory fish – Bathyal zone – dimly lit middle zone • No photosynthesizers • Zooplankton and smaller fish – Migrate to surface to feed at night. – Abyssal zone – lowest zone, dark and very cold, and has little DO cold, • Contains enough nutrients to support a large Contains number of species number • Ocean floor is complex – Mid-Atlantic Ridge – Canyons – Trenches deeper than the height of Mt. Everest • Food rains from above, called marine snow Food marine – Deposit feeders – Filter feeders – Average productivity and NPP per unit area is Average low except at equatorial upwellings low • Absolute productivity is large because ocean Absolute covers large area. covers • Productivity increase as latitude increases. • Effect of Human Activities on Marine Effect Systems: Red Alert Systems: – Humans have an affinity for the coast – Ecological and economic services being Ecological degraded or destroyed (Fig. 6-13) degraded – In 2006, 45% of world’s pop. and more than In half in the US lived near the coast half – By 2010, 80% projected to live near the coast III. Freshwater Life Zones III. • Freshwater Systems – 1% of earth’s surface – Lentic, or standing: lakes, ponds, and inland or wetlands. wetlands. – Lotic, or flowing: streams and rivers – Ecological and economic services (Fig. 6-14) • Lakes: Water-Filled Depressions – Large natural standing bodies of standing Large freshwater formed from precipitation, runoff, and groundwater seepage. groundwater • Causes of depressions: – Glaciation, crustal displacement, and volcanic activity – Water supplied by rainfall, melting snow, and Water streams streams – Vary tremendously in size, shape and nutrient Vary availability availability – Four distinct zones defined by depth and Four distance from shore (Fig.6-15) distance • Littorral zone – Shallow, near shore to depth rooted plants cannot grow – Most productive zone – Biodiversity high: algae, rooted plants, turtles, frogs, Biodiversity crayfish, bass, perch, carp crayfish, • Limnetic zone – – – – Open sunlit layer away from shore Main photosynthetic body of the lake Primary organism: phyo- and zooplankton Large fish inhabit this zone, move into littoral zone to feed Large and reproduce and • Profundal zone – Open water where it is too dark for photosynthesis – Fish adapted to lakes cooler, darker and lower oxygen Fish levels levels • Benthic zone – Bottom of the lake – Decomposers, detritus feeders, and fish that move from one Decomposers, zone to another. zone – Nourished from limnetic and littoral, and sediments that Nourished wash in wash – Thermoclines form in winter ad summer, but mix Thermoclines in the fall and spring. in • These overturns mix the water equalizing These overturns temperature, taking oxygen to the bottom, and nutrients to the top. nutrients • Effects of Plant Nutrients on Lakes: Too Much of a Effects Good Thing Good – Lake classified according to their nutrient content and Lake primary productivity. primary • Oligotrophic – poorly nourished (Fig. 6-16a) – – – Newly formed, deep, steep banks Low NPP ⇒ clear water Low Small populations of phytoplankton and fish (e.g., smallmouth bass Small and trout) and • Eutrophic – well-nourished (Fig. 6-16b) – Excessive phosphates and nitrates ⇒ high NPP Excessive – Sediments, organic material, and inorganic nutrients have washed Sediments, in in – Plant growth and decomposition – Typically shallow, murky brown or green w/ poor visibility • Cultural eutrophication • Many lakes are mesotrophic Many mesotrophic • Freshwater Streams and Rivers: From Freshwater Mountains to the Oceans Mountains – Surface water – precipitation that does not Surface sink into the ground or evaporate. sink – Runoff – surface water that flows into streams – Watershed, or drainage basin – land area that Watershed, delivers runoff, sediment, and dissolved substances into a stream. substances – Most streams begin in elevated areas (e.g., Most mountains, hills) mountains, – Flow from a mountain can be divided in to three different Flow life zones (Fig. 6-17): life • Source zone (or headwaters) – Usu. Shallow, cold, clear, and swiftly moving ⇒ high O2 Usu. – Low production ⇐ lack of nutrients and phytoplankton Low – Nutrients mostly from once living material (leaves, branches, Nutrients insects) insects) – Plants, algae and mosses that attach to rock – Fish and other animals have compact or flattened bodies to live Fish under stones under • Others with streamlined, muscular bodies to swim in strong Others currents. currents. • Transition zone – – – – Merging of headwaters forming wider, deeper, and warmer streams Gentler slopes with fewer obstacles Higher turbidity, slower moving, less oxygen More phytoplankton, and cool and warm-water fishes with less More oxygen requirements. oxygen • Flood plain zone – Streams join into wider, deeper rivers that flow across broad, Streams flat valleys flat – Water usu. w/ higher temp and less DO – Support large populations of producers: algae, Support cyanobacteria, and rooted aquatics along the shore cyanobacteria, – Muddy and contains high concentration so suspended silt – Main channels support distinctive varieties of fish (e.g., carp Main and catfish) and – Backwaters support species similar to lakes – Mouth of river may be divided in to many channels as is Mouth flows through the delta flows • Sediments deposit here and in the coastal wetlands and Sediments estuaries. estuaries. – Coastal deltas, wetlands and inland floodplains Coastal are important parts of earth’s natural capital. are • Relatively high diversity and productivity • Absorb floodwater and protect against tropical storms Absorb and tsunamis and – Human activities have degraded or destroyed Human the natural protection of coastal surface formations formations • Hurricanes, typhoons and tsunamis become partially Hurricanes, unnatural disasters (see Case Study, p. 140) unnatural – Streams shape the land over which they pass. – Watershed must be the focus when we wish to Watershed protect streams and rivers from excessive inputs of nutrients and pollutants. of • Freshwater Inland Wetlands: Vital Sponges – Inland wetlands – lands covered with freshwater all or part of the time, excluding lakes, reservoirs, and streams, located away from coastal areas. and • • • • • Marshes Swamps (Fig. 6-18) Prairie potholes Floodplains Arctic tundra in summer – When a wetland is dry, a wetland may be When recognized by soil composition and certain plants. plants. – Highly productive – Habitats for game fish, muskrats, otters, Habitats beavers, migratory waterfowl, and other birds beavers, – Inland wetlands provide free ecological and Inland economic services. economic • Filter and degrade toxic wastes and pollutants – In US, worth at least $1.6 billion/yr • Reduce flooding and erosion by absorbing and Reduce releasing stormwater slowly, and by absorbing overflows from streams and lakes overflows – In US, worth $3-4 billion/yr • • • • Help replenish stream flows during dry periods Help recharge groundwater aquifers Help maintain biodiversity Supply valuable products such as fish and shellfish, Supply blueberries, cranberries, wild rice, and timber blueberries, • Provide recreation for birdwatchers, nature Provide photographers, boaters, anglers, and waterfowl hunters hunters • Impacts of Human Activities on Freshwater Impacts Systems Systems – Four major impacts • First, dams, diversions, or canals fragment about 40% dams, of world’s 237 large rivers. of • Second, flood control levees and dikes alter and flood destroy aquatic habitats. destroy • Third, cities and farmlands as pollutants and excess cities nutrients to watershed. nutrients • Fourth, draining or filling of inland wetlands to grow draining crops (Fig. 6-19) or have been converted with crops or concrete, asphalt, and buildings. concrete, • Case Study: Inland Wetland Losses in the United Case States (Science and Politics) States – In US 95% of wetlands are freshwater; remaining are In saltwater or coastal. saltwater – Alaska has more wetlands than the other 49. – More than half the inland wetlands in continental US More have been lost since the 1600s. have • 80% for crops • Rest for mining, forestry, oil and gas extraction, highways, and Rest urban development urban • Iowa has lost 99% – Loss of this natural capital has been an important factor Loss in increased flood and drought damage. in – Other countries too: France and Germany lost 80% A Healthy Coral Reef (Fig 6-1a) Healthy Back Bleaching in Coral Reefs (6-1b) Bleaching Back The Ocean Planet (Figure 6-2) The Back Distribution of Major Oceans, Coral Reefs, Mangroves, and Freshwater Lakes and Rivers (Figure 6-3) Freshwater Back (Fig. 6-4) (Fig. Back Major Ocean Life Zones (Fig. 6-5) Major Back Back to Op Sediment Plume at Mouth of Madagascar’s Betsiboka River (Fig. 6-6) Betsiboka Back Components and Interactions in a Temperate Salt Marsh Ecosystem (Fig. 6-7) Temperate Back Mangrove Forest in Daintree National Park In Queensland, Australia (Fig. 6-8) In Back Specialized Niches in a Rocky Shore (Fig. 6-9) Shore Back Specialized Niches in a Sandy Shore (Fig. 6-9b) Shore Back Typical Barrier Island Profile (Fig. 6-10) (Fig. Back Components and Interactions in a Coral Reef Ecosystem (Fig. 6-11) Coral Back Major Threats to Coral Reefs (Fig 6-12) Major Back Major Human Impacts on the World’s Marine Systems (Fig. 6-13) Marine Back Major Ecological and Economic Services (Fig. 6-14) (Fig. Back Life Zones in a Temperate Zone Lake (Fig. 6-15) Lake Back Oligotrophic Lake (Fig. 6-16a) Oligotrophic Back Eutrophic Lake (Fig. 6-16b) Eutrophic Back Three Zones in the Downhill Flow of Water (Fig. 6-17) (Fig. Back Cypress Swamp in Tennessee (Fig. 6-18) Cypress Back Prairie Pothole Wetland That Has Been Ditched and Drained for Cropland (Fig. 6Ditched 19) Back ...
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