Aquatic Biodiversity

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

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

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

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

Euphotic Zone

Photosynthesis

Sun

Twilight

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 (Stopped)  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

White sand macoma

Sand dollar

Mole Shrimp

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

Grasses or shrubs Taller shrubs

Back Dune Most suitable for development

Bay or Lagoon Intensive recreation

Bay shore No filling

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

Bacteria Producer to Primary to primary secondary consumer consumer

Secondary to higher-level consumer

Moray eel

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 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 Fig. 6-13, p. 136

FRESHWATER LIFE ZONES(STOPPED)  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 EcologicalNatural CapitalEconomic Services 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 Scientific information

Employment

Fig. 6-14, p. 136

Lakes: Water-Filled Depressions(STOPPED 6-7)  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?

Lake in Winter

Lake in Spring

Lake in Summer

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.

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

Floodplain Zone

Water Sediment

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