Transcript Chapter 6
Chapter 6 Aquatic Biodiversity Chapter Overview 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? Updates Online The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles. InfoTrac: Down the bayou: a marine biologist, a community, and the resolve to preserve an ocean's bounty. Taylor Sisk. Earth Island Journal, Autumn 2006 v21 i3 p27(6). InfoTrac: A scourge of the '70s returns to Great Lakes. The Christian Science Monitor, March 30, 2006 p14. InfoTrac: The fate of the ocean. Julia Whitty. Mother Jones, March-April 2006 v31 i2 p32(15). National Oceanic and Atmospheric Administration: Fisheries Amazon Conservation Association: Amazon Rivers Project Core Case Study: Why Should We Care About Coral Reefs? Coral reefs form in clear, warm coastal waters of the tropics and subtropics. Formed by massive colonies of polyps. Figure 6-1 Fig. 6-1a, p. 126 Fig. 6-1b, p. 126 Video: Florida Reefs PLAY VIDEO Video: Reef Fish (Bahamas) PLAY VIDEO Core Case Study: Why Should We Care About Coral Reefs? Help moderate atmospheric temperature by removing CO2 from the atmosphere. Act as natural barriers that help protect 14% of the world’s coastlines from erosion by battering waves and storms. Provide habitats for a variety of marine organisms. Video: Beach Pollution PLAY VIDEO From ABC News, Environmental Science in the Headlines, 2005 DVD. AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2 Ocean hemisphere Land–ocean hemisphere Fig. 6-2, p. 127 AQUATIC ENVIRONMENTS Figure 6-3 What Kinds of Organisms Live in Aquatic Life Zones? Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms. Plankton: important group of weakly swimming, free-floating biota. • Phytoplankton (plant), Zooplankton (animal), Ultraplankton (photosynthetic bacteria) Necton: fish, turtles, whales. Benthos: bottom dwellers (barnacles, oysters). Decomposers: breakdown organic compounds (mostly bacteria). Life in Layers Life in most aquatic systems is found in surface, middle, and bottom layers. Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth. Euphotic zone (upper layer in deep water habitats): sunlight can penetrate. Animation: Ocean Provinces PLAY ANIMATION SALTWATER LIFE ZONES The oceans that occupy most of the earth’s surface provide many ecological and economic services. Figure 6-4 Natural Capital Marine Ecosystems Economic Services Ecological Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Waste treatment Reduced storm impact (mangroves, barrier islands, coastal wetlands) Habitats and nursery areas Pharmaceuticals Harbors and transportation routes Coastal habitats for humans Recreation Employment Genetic resources and biodiversity Oil and natural gas Scientific information Building materials Minerals Fig. 6-4, p. 129 The Coastal Zone: Where Most of the Action Is The coastal zone: the warm, nutrient-rich, shallow water that extends from the high-tide mark on land to the gently sloping, shallow edge of the continental shelf. The coastal zone makes up less than 10% of the world’s ocean area but contains 90% of all marine species. Provides numerous ecological and economic services. Subject to human disturbance. The Coastal Zone Figure 6-5 Sun Euphotic Zone Photosynthesis Estuarine Zone Continental shelf Open Sea Sea level Bathyal Zone Abyssal Zone Darkness High tide Coastal Zone Low tide Fig. 6-5, p. 130 Marine Ecosystems Scientists estimate that marine systems provide $21 trillion in goods and services per year – 70% more than terrestrial ecosystems. Figure 6-4 Fig. 6-6, p. 130 Estuaries and Coastal Wetlands: Centers of Productivity Estuaries include river mouths, inlets, bays, sounds, salt marshes in temperate zones and mangrove forests in tropical zones. Figure 6-7 Herring gulls Peregrine falcon Snowy Egret Cordgrass Short-billed Dowitcher Marsh Periwinkle Phytoplankton Smelt Soft-shelled clam Zooplankton and small crustaceans Clamworm Bacteria Producer to primary consumer Primary to secondary consumer Secondary to higher-level consumer All consumers and producers to decomposers Fig. 6-7a, p. 131 Fig. 6-7b, p. 131 Mangrove Forests Are found along about 70% of gently sloping sandy and silty coastlines in tropical and subtropical regions. Figure 6-8 Estuaries and Coastal Wetlands: Centers of Productivity Estuaries and coastal marshes provide ecological and economic services. Filter toxic pollutants, excess plant nutrients, sediments, and other pollutants. Reduce storm damage by absorbing waves and storing excess water produced by storms and tsunamis. Provide food, habitats and nursery sites for many aquatic species. Rocky and Sandy Shores: Living with the Tides Organisms experiencing daily low and high tides have evolved a number of ways to survive under harsh and changing conditions. Gravitational pull by moon and sun causes tides. Intertidal Zone: area of shoreline between low and high tides. Rocky and Sandy Shores: Living with the Tides Organisms in intertidal zone develop specialized niches to deal with daily changes in: Temperature Salinity Wave action Figure 6-9 Rocky Shore Beach Hermit crab Sea star Shore crab High tide Periwinkle Sea urchin Anemone Mussel Low tide Sculpin Barnacles Kelp Sea lettuce Monterey flatworm Nudibranch Fig. 6-9, p. 132 Barrier Beach Beach flea Peanut worm Blue crab Tiger Beetle Clam Dwarf Olive High tide Sandpiper Low tide Silversides Mole Shrimp White sand macoma Sand dollar Ghost Shrimp Moon snail Fig. 6-9, p. 132 Barrier Islands Low, narrow, sandy islands that form offshore from a coastline. Primary and secondary dunes on gently sloping sandy barrier beaches protect land from erosion by the sea. Figure 6-10 Ocean Beach Intensive recreation, no building Primary Dune Trough Secondary Dune No direct No direct Limited passage passage recreation or building and walkways or building Back Dune Most suitable for development Bay or Lagoon Intensive recreation Grasses or shrubs Bay shore No filling Taller shrubs Taller shrubs and trees Fig. 6-10, p. 133 Threats to Coral Reefs: Increasing Stresses Biologically diverse and productive coral reefs are being stressed by human activities. Figure 6-11 Gray reef shark Green sea turtle Sea nettle Fairy basslet Blue tangs Parrot fish Sergeant major Hard corals Algae Brittle star Banded coral shrimp Phytoplankton Symbiotic algae Zooplankton Coney Blackcap basslet Sponges Moray eel Bacteria Producer to Primary to primary secondary consumer consumer Secondary to higher-level consumer All consumer and producers to decomposers Fig. 6-11, p. 134 Threats to Coral Reefs: Increasing Stresses Figure 6-12 Natural Capital Degradation Coral Reefs Ocean warming Soil erosion Algae growth from fertilizer runoff Mangrove destruction Bleaching Rising sea levels Increased UV exposure Damage from anchors Damage from fishing and diving Fig. 6-12, p. 135 Biological Zones in the Open Sea: Light Rules Euphotic Nutrient levels low, dissolved O2 high, photosynthetic activity. Bathyal zone: dimly lit middle layer. No photosynthetic activity, zooplankton and fish live there and migrate to euphotic zone to feed at night. Abyssal zone: brightly lit surface layer. zone: dark bottom layer. Very cold, little dissolved O2. Effects of Human Activities on Marine Systems: Red Alert Human activities are destroying or degrading many ecological and economic services provided by the world’s coastal areas. Figure 6-13 Natural Capital Degradation Marine Ecosystems Half of coastal wetlands lost to agriculture and urban development Over one-third of mangrove forests lost to agriculture, development, and aquaculture shrimp farms Beaches eroding because of coastal development and rising sea level Ocean bottom habitats degraded by dredging and trawler fishing At least 20% of coral reefs severely damaged and 30– 50% more threatened Fig. 6-13, p. 136 FRESHWATER LIFE ZONES Freshwater life zones include: Standing (lentic) water such as lakes, ponds, and inland wetlands. Flowing (lotic) systems such as streams and rivers. Figure 6-14 Natural Capital Freshwater Systems Ecological Services Economic Services Climate moderation Food Nutrient cycling Drinking water Waste treatment Irrigation water Flood control Hydroelectricity Groundwater recharge Transportation corridors Habitats for many species Recreation Genetic resources and biodiversity Employment Scientific information Fig. 6-14, p. 136 Lakes: Water-Filled Depressions Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of: Littoral zone (near shore, shallow, with rooted plants). Limnetic zone (open, offshore area, sunlit). Profundal zone (deep, open water, too dark for photosynthesis). Benthic zone (bottom of lake, nourished by dead matter). Animation: Lake Zonation PLAY ANIMATION Lakes: Water-Filled Depressions During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. This equalizes the temperature at all depths. Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top. What causes this overturning? Animation: Lake Turnover PLAY ANIMATION Lakes: Water-Filled Depressions Figure 6-15 Sunlight Green frog Painted turtle Blue-winged teal Muskrat Pond snail Littoral zone Limnetic zone Diving beetle Plankton Profundal zone Benthic zone Yellow perch Bloodworms Northern pike Fig. 6-15, p. 137 Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Figure 6-16 Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Plant nutrients from a lake’s environment affect the types and numbers of organisms it can support. Oligotrophic (poorly nourished) lake: Usually newly formed lake with small supply of plant nutrient input. Eutrophic (well nourished) lake: Over time, sediment, organic material, and inorganic nutrients wash into lakes causing excessive plant growth. Animation: Trophic Nature of Lakes PLAY ANIMATION Effects of Plant Nutrients on Lakes: Too Much of a Good Thing Cultural eutrophication: Human inputs of nutrients from the atmosphere and urban and agricultural areas can accelerate the eutrophication process. 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 Rain and snow Lake Glacier Rapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Delta Deposited sediment Ocean Source Zone Transition Zone Water Sediment Floodplain Zone Fig. 6-17, p. 139 Case Study: Dams, Wetlands, Hurricanes, and New Orleans Dams and levees have been built to control water flows in New Orleans. Reduction in natural flow has destroyed natural wetlands. Causes city to lie below sea-level (up to 3 meters). Global sea levels have risen almost 0.3 meters since 1900. Freshwater Inland Wetlands: Vital Sponges Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. Figure 6-18 Freshwater Inland Wetlands: Vital Sponges Filter and degrade pollutants. Reduce flooding and erosion by absorbing slowly releasing overflows. Help replenish stream flows during dry periods. Help recharge ground aquifers. Provide economic resources and recreation. Impacts of Human Activities on Freshwater Systems Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats. Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers. Flood control levees and dikes alter and destroy aquatic habitats. Cities and farmlands add pollutants and excess plant nutrients to streams and rivers. Many inland wetlands have been drained or filled for agriculture or (sub)urban development. Impacts of Human Activities on Freshwater Systems These wetlands have been ditched and drained for cropland conversion. Figure 6-19 Video: Elephant Seals PLAY VIDEO Video: Giant Clam PLAY VIDEO Video: River Flyover PLAY VIDEO Video: Schooling Fish PLAY VIDEO Video: Sea Anemones PLAY VIDEO Video: Seal Lions PLAY VIDEO Video: Sting Rays PLAY VIDEO