Chapter 11

Sustaining Aquatic Biodiversity

Core Case Study: A Biological Roller Coaster Ride in Lake Victoria

Lake Victoria has lost their endemic fish species to large introduced predatory fish.

Figure 12-1

Core Case Study: A Biological Roller Coaster Ride in Lake Victoria

Reasons for Lake Victoria’s loss of biodiversity: Introduction of Nile perch. Lake experienced algal blooms from nutrient

runoff. Invasion of water hyacinth has blocked sunlight

and deprived oxygen. Nile perch is in decline because it has eaten its

own food supply.

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

Human activities have destroyed, disrupted or degraded a large proportion of the world’s coastal, marine and freshwater ecosystems. Approximately 20% of the world's coral reefs

have been destroyed. During the past 100 years, sea levels have risen

10-25 centimeters. We have destroyed more than 1/3 of the world’s

mangrove forests for shipping lanes.

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

Area of ocean before and after a trawler net, acting like a giant plow, scraped it.

Figure 12-2

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

Harmful invasive species are an increasing threat to marine and freshwater biodiversity. Bioinvaders are blamed for about 2/3 of fish

extinctions in the U.S. between 1900-2000. Almost half of the world’s people live on or

near a coastal zone and 80% of ocean water pollution comes from land-based human activities.

Population Growth and Pollution

Each year plastic items dumped from ships and left as litter on beaches threaten marine life.

Figure 12-3

Overfishing and Extinction: Gone Fishing, Fish Gone

About 75% of the world’s commercially valuable marine fish species are over fished or fished near their sustainable limits. Big fish are becoming scarce. Smaller fish are next. We throw away 30% of the fish we catch. We needlessly kill sea mammals and birds.

Fig. 12-A, p. 255

Fish farming in cage

Trawler fishing

Spotter airplane

Sonar

Trawl flapTrawl lines

Purse-seine fishing

Trawl bagFish school

Drift-net fishingLong line fishing

Lines with hooks

Fish caught by gills

Deep sea aquaculture cage

Float Buoy

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

Laws, international treaties, and education can help reduce the premature extinction of marine species.

Since 1989 the U.S. government has required offshore shrimp trawlers to use turtle exclusion devices. Sea turtle tourism brings in almost three times as

much money as the sale of turtle products.

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

Six of the world’s seven major turtle species are threatened or endangered because o human activities.

Figure 12-4

Case Study: The Florida Manatee and Water Hyacinths

Manatee can eat unwanted Water Hyacinths.

Endangered due to: Habitat loss. Entanglement from fishing

lines and nets. Hit by speed boats. Stress from cold. Low reproductive rate

Figure 12-B

Case Study: Commercial Whaling

After many of the world’s whale species were overharvested, commercial whaling was banned in 1960, but the ban may be overturned.

Figure 12-6

Case Study: Commercial Whaling

Despite ban, Japan, Norway, and Iceland kill about 1,300 whales of certain species for scientific purposes. Although meat is still sold

commercially.

Figure 12-5

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

Fully protected marine reserves make up less than 0.3% of the world’s ocean area. Studies show that fish populations double, size

grows by almost a third, reproduction triples and species diversity increases by almost one fourth.

Some communities work together to develop integrated plans for managing their coastal areas.

MANAGING AND SUSTAINING MARINE FISHERIES

There are a number of ways to manage marine fisheries more sustainably and protect marine biodiversity.

Some fishing communities regulate fish harvests on their own and others work with the government to regulate them. Modern fisheries have weakened the ability of

many coastal communities to regulate their own fisheries.

PROTECTING, SUSTAINING, AND RESTORING WETLANDS

Requiring government permits for filling or destroying U.S. wetlands has slowed their loss, but attempts to weaken this protection continue.

Figure 12-8

Case Study: Restoring the Florida Everglades

The world’s largest ecological restoration project involves trying to undo some of the damage inflicted on the Everglades by human activities. 90% of park’s wading birds have vanished. Other vertebrate populations down 75-95%. Large volumes of water that once flowed through

the park have been diverted for crops and cities. Runoff has caused noxious algal blooms.

Restoring the Florida

Everglades The project has

been attempting to restore the Everglades and Florida water supplies.

Figure 12-10

PROTECTING, SUSTAINING, AND RESTORING LAKES AND RIVERS

Lakes are difficult to manage and are vulnerable to planned or unplanned introductions of nonnative species.

For decades, invasions by nonnative species have caused major ecological and economic damage to North America’s Great lakes. Sea lamprey, zebra mussel, quagga mussel,

Asian carp.

PROTECTING, SUSTAINING, AND RESTORING LAKES AND RIVERS

Dams can provide many human benefits but can also disrupt some of the ecological services that rivers provide. 119 dams on Columbia River have sharply

reduced (94% drop) populations of wild salmon. U.S. government has spent $3 billion in

unsuccessful efforts to save the salmon. Removing hydroelectric dams will restore native

spawning grounds.