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

Figure 6.1 Natural capital: a 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 too warm temperatures). With the 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. Fig. 6-1a, p. 126

Figure 6.1 Natural capital: a 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 too warm temperatures). With the 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. Fig. 6-1b, p. 126

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.

AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2

Land–ocean hemisphere Figure 6.2 Natural capital: the ocean planet. The salty oceans cover 71% of the earth’s surface. About 97% of the earth’s water is in the interconnected oceans, which cover 90% of the planet’s mostly ocean hemisphere (left) and 50% of its land–ocean hemisphere (right). Freshwater systems cover less than 1% of the earth’s surface. 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.

SALTWATER LIFE ZONES The oceans that occupy most of the earth’s surface provide many ecological and economic services. Figure 6-4

Harbors and transportation routes Natural Capital Marine Ecosystems Economic Services Ecological Services Climate moderation Food CO2 absorption Animal and pet feed Nutrient cycling Pharmaceuticals Waste treatment Harbors and transportation routes Reduced storm impact (mangroves, barrier islands, coastal wetlands) Coastal habitats for humans Figure 6.4 Natural capital: major ecological and economic services provided by marine systems. Scientists estimate that marine systems provide $21 trillion in goods and services per year—70% more than terrestrial ecosystems. QUESTION: Which two ecological services and which two economic services do you think are the most important? Habitats and nursery areas Recreation Employment Genetic resources and biodiversity Oil and natural gas Minerals Scientific information Building materials 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

High tide Coastal Zone Open Sea Sun Low tide Sea level Photosynthesis Euphotic Zone Estuarine Zone Continental shelf Bathyal Zone Twilight Abyssal Zone Figure 6.5 Natural capital: major life zones in an ocean (not drawn to scale). Actual depths of zones may vary. Darkness 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

Figure 6.6 Natural capital degradation: view of an estuary taken from space. The photo shows the sediment plume at the mouth of Madagascar’s 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 world’s most eroded country. 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 Figure 6.7 Natural capital: some components and interactions in a salt marsh ecosystem in a temperate area such as the United States. When these organisms die, decomposers break down their organic matter into minerals used by plants. Colored arrows indicate transfers of matter and energy between consumers (herbivores), secondary or higher-level consumers (carnivores), and decomposers. Organisms are not drawn to scale. The photo below shows a salt marsh in Peru. Zooplankton and small crustaceans Soft-shelled clam 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

Figure 6.7 Natural capital: some components and interactions in a salt marsh ecosystem in a temperate area such as the United States. When these organisms die, decomposers break down their organic matter into minerals used by plants. Colored arrows indicate transfers of matter and energy between consumers (herbivores), secondary or higher-level consumers (carnivores), and decomposers. Organisms are not drawn to scale. The photo below shows a salt marsh in Peru. 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 Figure 6.9 Natural capital: living between the tides. Some organisms with specialized niches found in various zones on rocky shore beaches (top) and barrier or sandy beaches (bottom). Organisms are not drawn to scale. Barnacles Kelp Sea lettuce Monterey flatworm Nudibranch Fig. 6-9, p. 132

Barrier Beach Beach flea Peanut worm Tiger Beetle Blue crab Clam Dwarf Olive High tide Sandpiper Ghost Shrimp Low tide Silversides Figure 6.9 Natural capital: living between the tides. Some organisms with specialized niches found in various zones on rocky shore beaches (top) and barrier or sandy beaches (bottom). Organisms are not drawn to scale. Mole Shrimp White sand macoma Moon snail Sand dollar 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

Primary Dune Secondary Dune Grasses or shrubs Bay or Lagoon Ocean Beach Trough Back Dune Intensive recreation, no building No direct passage or building Limited recreation and walkways No direct passage or building Most suitable for development Intensive recreation Grasses or shrubs Bay shore No filling Taller shrubs Taller shrubs and trees Figure 6.10 Natural capital: primary 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 help hold the sand in place. Ideally, construction is allowed only behind the second strip of dunes, and walkways to the beach are built over the dunes to keep them intact. This helps preserve barrier beaches and protect buildings from damage by wind, high tides, beach erosion, and flooding from storm surges. Such protection is rare because the short-term economic value of oceanfront land is incorrectly 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. 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

Green sea turtle Banded coral shrimp Symbiotic algae Gray reef shark Green sea turtle Sea nettle Fairy basslet Blue tangs Parrot fish Sergeant major Hard corals Brittle star Algae Banded coral shrimp Phytoplankton Symbiotic algae Coney Figure 6.11 Natural capital: some components and interactions in a coral reef ecosystem. When these organisms die, decomposers break down their organic matter into minerals used by plants. Colored arrows indicate transfers of matter and energy between producers, primary consumers (herbivores), secondary or higher-level consumers (carnivores), and decomposers. Organisms are not drawn to scale. See photos of a coral reef in Figure 6-1 and photo 10 in the Detailed Contents. Zooplankton Blackcap basslet Sponges Moray eel Bacteria Producer to primary consumer Primary to secondary consumer Secondary to higher-level consumer All consumer and producers to decomposers Fig. 6-11, p. 134

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 Figure 6.12 Natural capital degradation: major threats to coral reefs. QUESTION: Which three of these threats do you think are the most serious? Fig. 6-12, p. 135

Biological Zones in the Open Sea: Light Rules Euphotic zone: brightly lit surface layer. 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: 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 Figure 6.13 Natural capital degradation: major human impacts on the world’s marine systems. QUESTION: Which two of these threats do you think are the most serious? 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

Habitats for many species Natural Capital Natural Capital Freshwater Systems Ecological Services Economic Services Climate moderation Nutrient cycling Waste treatment Flood control Groundwater recharge Habitats for many species Genetic resources and biodiversity Scientific information Food Drinking water Irrigation water Hydroelectricity Transportation corridors Recreation Employment Figure 6.14 Natural capital: major ecological and economic services provided by freshwater systems. QUESTION: Which two ecological services and which two economic services do you think are the most important? 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).

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?

Lakes: Water-Filled Depressions Figure 6-15

Sunlight Painted turtle Green frog Blue-winged teal Muskrat Pond snail Littoral zone Limnetic zone Figure 6.15 Natural capital: distinct zones of life in a fairly deep temperate zone lake. Diving beetle Plankton Profundal zone Benthic zone Northern pike Yellow perch Bloodworms 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.

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

Oxbow lake Deposited sediment Rain and snow Glacier Lake Rapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Deposited sediment Delta Ocean Source Zone Transition Zone Figure 6.17 Natural capital: three 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. 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