© 2011 Pearson Education, Inc. Lecture Outlines Chapter 16 Environment: The Science behind the...

© 2011 Pearson Education, Inc.

Lecture Outlines

Chapter 16

Environment:The Science behind the Stories

4th Edition

Withgott/Brennan


This lecture will help you understand:

• The marine environment• Ocean-climate relationships• Marine ecosystems• Marine pollution• The state of ocean fisheries• Marine protected areas and

reserves


Central Case: Collapse of the cod fisheries• No fish has had more impact on

civilization than the Atlantic cod

• Cod have been fished for centuries

• Large ships and technology have destroyed the cod fishery

• Even protected stocks are not recovering- Young cod are being preyed

on• But other species are recovering

in protected areas


Cod are groundfish

• Fish that live or feed along the bottom- Halibut, pollack, flounder

• Cod eat small fish and invertebrates

• They inhabit cool waters on both sides of the Atlantic

• The 24 stocks (populations) of cod crashed- Overfishing and destroyed

habitat

The U.S. and Canada have paid billions to retrain fishermen who lost their jobs


Oceans cover most of the Earth’s surface

• Oceans influence climate, team with biodiversity, provide resources, and help transportation and commerce

• Oceans cover 71% of Earth’s surface and contain 97.5% of its water

• Oceans influence the atmosphere, lithosphere, and biosphere


Seafloor topography can be rugged

• The seafloor consists of:- Underwater volcanoes- Steep canyons- Mountain ranges - Mounds of debris- Trenches- Some flat areas

• Some island chains are formed by reefs or volcanoes- Topographically complex areas serve as habitat and

productive fishing grounds


A stylized bathymetric profile of the ocean

A stylized map reflects the ocean’s bathymetry (depths) and topography (landforms)


Ocean water contains salt

• Ocean water is 96.5% water - Plus, ions of dissolved

salts• Evaporation removes pure

water - Leaving salt behind

• Low levels of nutrients (nitrogen and phosphorus)

• Oxygen is added by plants, bacteria, and atmospheric diffusion


Ocean water is vertically structured

• Temperature declines with depth• Heavier (colder, saltier) water sinks

- Light (warmer, less salty) water stays near the surface• Temperatures are more stable than land temperatures

- Water has high heat capacity (heat required to increase temperature by a given amount)

- It takes more energy to warm water than air• Oceans regulate Earth’s climate

- They absorb and release heat- The ocean’s surface circulation moves heat around


The ocean has several layers• Surface zone

- Warmed by sunlight and stirred by wind- Consistent water density

• Pycnocline = below the surface zone - Density increases with

depth• Deep zone = below the

pycnocline- Dense, sluggish water - Unaffected by winds,

storms, sunlight, or temperature


Ocean water flows horizontally in currents

• Currents = vast riverlike flows in the oceans- Driven by density differences, heating and cooling,

gravity, and wind - Influence global climate and El Niño and La Niña- Transport heat, nutrients, pollution, the larvae of

many marine species, and people• Some currents such as the Gulf Stream are rapid and

powerful- The warm water moderates Europe’s climate


Currents form patterns across the globe


Vertical movement affects ecosystems

• Upwelling = the upward flow of cold, deep water toward the surface - High primary productivity and lucrative fisheries- Also occurs where strong winds blow away from, or

parallel to, coastlines • Downwellings = oxygen-rich water sinks where surface

currents come together


Currents affect climate

• Horizontal and vertical movement of oceans affects global and regional climates

• Thermohaline circulation = a worldwide current system- Warmer, fresher water moves along the surface- Cooler, saltier, denser water moves beneath the surface

• North Atlantic Deep Water (NADW) = one part of the thermohaline conveyor belt- Water in the Gulf Stream flows to Europe- Released heat keeps Europe warmer that it would be- Sinking cooler water creates a region of downwelling


The North Atlantic Deep Water

• Interrupting the thermohaline circulation could trigger rapid climate change- Melting ice from Greenland will run into the North

Atlantic- Making surface waters even less dense- Stopping NADW formation and shutting down the

northward flow of warm water - Europe would rapidly cool

• This circulation is already slowing- But Greenland may not have enough runoff to stop it


El Niño–Southern Oscillation (ENSO)

• ENSO = a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation- In the tropical Pacific Ocean

• Normal winds blow east to west, from high to low pressure- This forms a large convective loop in the atmosphere

• Winds push water west, causing it to “pile up”- Nutrient-rich, cold water along Peru and Ecuador rises

from the deep• Decreased pressure in the eastern Pacific triggers El Niño

- Warm water flows eastward, suppressing upwellings


Effects of El Niño and La Niña

• Coastal industries (e.g., Peru’s anchovy fisheries) are devastated- Worldwide, fishermen lost $8 billion in 1982–1983

• Global weather patterns change- Rainstorms, floods, drought, fires

• La Niña = the opposite of El Niño- Cold waters rise to the surface and extend westward• ENSO cycles are periodic but irregular (every 2–8

years)- Globally warming sea and air may be increasing the

strength and frequency of these cycles


ENSO, El Niño, and La Niña

Normal conditions El Niño conditions


Climate change is altering the oceans• Global climate change will affect ocean chemistry and

biology• Burning fossil fuels and removing vegetation increase

CO2, which warms the planet

- Oceans absorb carbon dioxide (CO2) from the air

• But oceans may not be able to absorb much more CO2

• Increased CO2 in the ocean makes it more acidic

- Ocean acidification makes chemicals less available for sea creatures (e.g., corals) to form shells

- Fewer coral reefs decrease biodiversity and ecosystem services


Marine and coastal ecosystems

• Regions of ocean water differ greatly- Some zones support more life than others

• Photic zone = well-lighted top layer - Absorbs 80% of solar energy- Supports high primary productivity

• Pelagic = habitats and ecosystems between the ocean’s surface and floor

• Benthic = habitats and ecosystems on the ocean floor• Most ecosystems are powered by solar energy

- But even the darkest depths host life


Open ocean systems vary in biodiversity

• Microscopic phytoplankton are the base of the marine food chain- Algae, protists, cyanobacteria- They feed zooplankton- Which then feed fish, jellyfish, whales, etc.

• Predators at higher trophic levels - Larger fish, sea turtles,

sharks, and fish-eating birds


Animals of the deep ocean

• Animals adapt to extreme water pressure and the dark- Scavenge carcasses or organic detritus- Predators- Others have mutualistic relationships with bacteria- Some carry bacteria that produce light chemically by

bioluminescence• Hydrothermal vents support

tubeworms, shrimp, and other chemosynthetic species


Kelp forests harbor many organisms

• Kelp = large, dense, brown algae growing from the floor of continental shelves

• Dense strands form kelp forests along temperate coasts- They provide shelter and food for organisms

• They absorb wave energy and protect shorelines from erosion

• People use it in food, cosmetics, paints, paper, soap, etc.


Coral reefs are treasure troves of biodiversity• Coral reef = a mass of calcium carbonate composed of

the skeletons of tiny marine animals (corals)- They may be an extension of a shoreline- Or exist along a barrier island, parallel to the shore- Or as an atoll (a ring around a submerged island)

• Corals = tiny colonial invertebrate animals- Related to sea anemones and jellyfish- Attach to a rock or reef and capture passing food with

stinging tentacles- Get food from symbiotic algae (zooxanthallae)


Most corals are colonial

• Reefs consist of millions of densely packed animals• Reefs are located in shallow subtropical and tropical

waters- Protect shorelines by absorbing waves- Innumerable invertebrates and fish species find food

and shelter in reef nooks and crannies


Coral reefs are in worldwide decline

• “Coral bleaching” = occurs when zooxanthellae leave the coral or die- Corals lose their color and die, leaving white patches- From climate change, pollution, or unknown natural

causes• Nutrient pollution causes algal growth

- Which smothers coral• Divers damage reefs by using cyanide to capture fish• Acidification of oceans deprives corals of carbonate

ions for their structural parts


Deepwater coral reefs exist

• They thrive in waters outside the tropics - On ocean floor at depths of 200–500 m (650–1,650 ft)

• Occur in cold-water areas off the coasts of Spain, the British Isles, and elsewhere- Little is known about these reefs

• Already, many have been badly damaged by trawling - Some reefs are now being protected


Intertidal zones undergo constant change

• Intertidal (littoral) ecosystems = where the ocean meets the land - Between the uppermost reach of the high tide and the

lowest limit of the low tide• Tides = periodic rising and falling of the ocean’s height

due to the gravitational pull of the sun and moon• Intertidal organisms spend part of their time submerged

in water and part of their time exposed to sun and wind


A typical intertidal zone


Intertidal zones are a tough place to live

• But they have amazing diversity- Rocky shorelines, crevices,

pools of water (tide pools)- Anemones, mussels,

barnacles, urchins, sea slugs- Starfish and crabs

• Temperature, salinity, and moisture change dramatically from high to low tide

• Sandy intertidal zones have slightly less biodiversity


Salt marshes line temperate shorelines

• Salt marshes = occur along coasts at temperate latitudes- Tides wash over gently sloping sandy, silty substrates

• Tidal creeks = channels that rising and falling tides flow into and out of

• Salt marshes have very high primary productivity- Critical habitat for birds, commercial fish, and

shellfish- They filter pollution- They stabilize shorelines against storm surges


People change and destroy salt marshes

• People want to live or do business along coasts- We lose key ecosystem services- Flooding (e.g., from Hurricane Katrina) worsens


Mangrove forests line coasts

• In tropical and subtropical latitudes - They replace salt marshes along sandy coasts

• Mangroves = salt-tolerant trees - Their unique roots curve up for oxygen and down for

support• Nesting areas for birds• Nurseries for fish and shellfish

Mangroves provide food, medicine, tools, and construction materials


Mangrove forests have been destroyed

• Half the world’s mangrove forests are gone- Developed for residential, commercial, and

recreational uses- Shrimp farming

• Once destroyed, coastal areas no longer:- Slow runoff- Filter pollutants- Retain soil- Protect communities against storm surges


Fresh and salt water meet in estuaries

• Estuaries = water bodies where rivers flow into the ocean, mixing fresh and salt water

• They are biologically productive- Have fluctuations in salinity

• Critical habitat for shorebirds and shellfish• Transitional zone for fish that spawn in streams and

mature in salt water• They have been affected by development, pollution,

habitat alteration, and overfishing


Marine pollution

• People use oceans as a sink for waste and pollutants• Even into the mid-20th century, coastal U.S. cities

dumped trash and untreated sewage along their shores• Nonpoint source pollution comes from all over

- Oil, plastic, chemicals, excess nutrients

In 2008, 391,000 Ocean Conservancy volunteers from 104 nations picked up 3.1 million kg (6.8 million lb) of

trash from 27,000 km (17,000 miles) of shoreline


Nets and plastic debris endanger life

• Plastic items dumped into the sea harm or kill wildlife- Wildlife mistake it for food- 98% of dead northern

fulmars had plastic in their stomachs

• Plastic is nonbiodegradable- Drifts for decades- Breaks into tiny pieces

Trillions of tiny plastic pellets float in the oceans and are eaten


Plastic trash is accumulating in the oceans

• Circulating currents bring and trap plastic trash to areas- The northern Pacific Gyre stretches from California to

Hawaii to Japan- This “Great Pacific Garbage Patch” is the size of Texas

and has 3.3 plastic bits/m2

• The 2006 Marine Debris Research, Prevention, and Reduction Act is not enough

• We must reduce, reuse, and recycle more plastic- Participate in efforts such as the International Coastal

Cleanup


Oil pollution comes from spills of all sizes

• 30% of oil and 50% of natural gas come from seafloor deposits- North Sea, Gulf of Mexico

• Drilling in other places is banned- Spills could harm valuable

fisheries• The Deepwater Horizon

exploded off Louisiana’s coast in April 2010- Spilling 140 gallons/min- Hitting coasts of four states


Oil spills have severe consequences

• Major spills make headlines- Foul beaches- Coat and kill animals- Devastate fisheries

• Countless non-point sources produce most oil pollution- Small boat leaks, runoff

Major oil spills cause severe environmental and economic problems


Oil spills have decreased

• Due to emphasis on spill prevention and response- Stricter regulations are

resisted by the oil industry• The U.S. Oil Pollution Act

(1990)- Created a $1 billion

prevention and cleanup fund - Requires that all ships have

double hulls by 2015 Recently, oil spills have decreased


Toxic pollutants contaminate seafood

• Toxic pollutants can make food unsafe to eat• Mercury contamination from coal combustion and other

sources bioaccumulates and biomagnifies- Dangerous to children and pregnant or nursing women

• Avoid eating swordfish, shark, and albacore tuna- Eat seafood low in mercury (catfish, salmon, canned

light tuna)• Avoid seafood from areas where health advisories have

been issued


Excess nutrients cause algal blooms

• Harmful algal blooms = nutrients increase algae that produce powerful toxins

• Red tide = algae that produce red pigments that discolor water- Illness and death to wildlife

and humans- Economic loss to fishing

industries and beach tourism• Reduce runoff • Do not eat affected organisms


Emptying the oceans

• Overharvesting is the worst marine problem• We are putting unprecedented pressure on marine

resources- Half the world’s marine fish populations are fully

exploited and can’t be fished more intensively- 28% of fish population are overexploited and

heading to extinction• Total fisheries catch leveled off after 1988

- Despite increased fishing effort• The maximum wild fisheries potential has been

reached


The global fisheries catch has increased

It is predicted that populations of all ocean species we fish for today will collapse by 2048


We have long overfished

• People began depleting sea life centuries ago• Species have been hunted to extinction: Caribbean monk

seal, Steller’s sea cow, Atlantic gray whale• Overharvesting Chesapeake Bay oyster beds led to its

collapse, eutrophication, and hypoxia• Decreased sea turtle populations cause overgrowth of sea

grass and can cause sea grass wasting disease• Overharvesting nearly exterminated many whale species• People never thought groundfish could be depleted

- New approaches or technologies increased catch rates


Fishing has industrialized

• Factory fishing = huge vessels use powerful technologies to capture fish in huge volumes - Even processing and

freezing their catches at sea• Driftnets for schools of

herring, sardines, mackerel, sharks, shrimp

• Longline fishing for tuna and swordfish

• Trawling for pelagic fish and groundfish


Fishing practices kill nontarget animals

• Bycatch = the accidental capture of animals• Drift netting drowns dolphins, turtles, and seals

- Fish die on deck- Banned in international waters- But it is still used in national waters

• Longline fishing kills turtles, sharks, and over 300,000 seabirds/year- Methods (e.g., flags) are being developed to limit

bycatch


Dolphins and tuna

• Dolphins are trapped in purse seine nets used to catch tuna- Hundreds of thousands of dolphins were killed

• The 1972 Marine Mammal Protection Act forced fleets to try to free dolphins- Bycatch dropped dramatically

• Other nations fished for tuna, and bycatch increased • The U.S. government required that nations exporting tuna

to the U.S. minimize dolphin bycatch- Dolphin-safe tuna uses methods to avoid bycatch


Dolphin deaths have declined, but …

• Other animals (e.g., sharks) are still caught

• Dolphins have not recovered- Too few fish to eat

• Rules and technology have decreased dolphin deaths


Bottom-trawling destroys ecosystems

• Heavy nets crush organisms and damage sea bottoms- It is especially destructive to complex areas (e.g., reefs)

• It equals clear-cutting and strip mining- Georges Bank has been trawled three times

- Destroying young cod as bycatch- The reason the cod stock is not recovering


Modern fleets deplete marine life rapidly

• Grand Banks cod have been fished for centuries- Catches more than doubled with industrial trawlers- Record-high catches lasted only 10 years

• George Bank cod fishery also collapsed


Industrialized fishing is destroying fisheries

• Worldwide, industrialized fishing is depleting marine populations with astonishing speed- 90% of large-bodied fish and sharks are eliminated

within 10 years after fishing begins- Populations stabilize at 10% of their former levels

• Communities were very different before modern fishing- Removing animals at higher trophic levels allows

prey to proliferate and change communities

Oceans today contain only one-tenth of the large-bodied animals they once did


Several factors mask declines

• Industrialized fishing has depleted stocks- But global catch has remained stable for the past 20

years• How can stability mask population declines?

- Fishing fleets travel farther to reach less-fished areas - Fleets fish in deeper waters (now at 250 m)- Fleets spend more time fishing and set more nets- Improved technologies: faster ships, sonar mapping,

satellite navigation, thermal sensing, aerial spotting• Fleets expend more effort to catch the same number of

fish


We are “fishing down the food chain”

• Figures on total global catch do tell the whole story• As fishing increases, the size and age of fish caught

decline- 10-year-old cod, once common, are now rare

• As species become too rare to fish, fleets target more abundant species- Shifting from large, desirable species to smaller, less

desirable ones- This entails catching species at lower trophic levels


Purchasing choices influence fishing practices

• Buy ecolabeled seafood- Dolphin-safe tuna

• Consumers don’t know how their seafood was caught- Nonprofit organizations

have devised guides for consumers

- Avoid: Atlantic cod, wild-caught caviar, sharks, farmed salmon

Best choices: farmed catfish, mussels, oysters, tilapia


Diversity loss erodes ecosystem services

• Factors that deplete biodiversity threaten ecosystem services of the oceans

• Systems with reduced species or genetic diversity show less primary and secondary production- They are less able to withstand disturbance

• Biodiversity loss reduces habitat for nurseries for fish and shellfish

• Less diversity leads to reduced filtering and detoxification - Resulting in algal blooms, dead zones, fish kills, beach

closures


Fisheries management

• Based on maximum sustained yield to maximize harvest- While keeping fish available for the future- Managers may limit the harvest or restrict gear used

• Despite management, stocks have plummeted- It is time to rethink fisheries management

• Ecosystem-based management shifts away from species and toward the larger ecosystem- Considers the impacts of fishing on habitat quality,

species interactions, and long-term effects- Sets aside areas of oceans free from human

interference


We can protect areas in the ocean

• Marine protected areas (MPAs) = most are along the coastlines of developed countries- They still allow fishing or other extractive activities

• Marine reserves = areas where fishing is prohibited- Leave ecosystems intact, without human interference- Improve fisheries, because young fish will disperse

into surrounding areas• Many commercial, recreation fishers, and businesses do

not support reserves - Be sensitive to concerns of local residents


Reserves work for both fish and fisheries

• Marine reserves:- Increased densities of organisms by 91%- Increased biomass by 192%- Increased organism size by 31%- Increased species diversity by 23%

• Benefits inside reserve boundaries include:- Rapid and long-term increases in abundance,

diversity, and productivity of marine organisms- Decreased mortality and habitat destruction- Decreased likelihood of extirpation of species


Areas outside reserves also benefit

• A “spillover effect” occurs when individuals of protected species spread outside reserves- Larvae of species protected within reserves “seed the

seas” outside reserves- Improved fishing and ecotourism

• Local residents who were opposed support reserves once they see their benefits

• Once commercial trawling was stopped on Georges Bank:- Populations of organisms began to recover- Fishing in adjacent waters increased


How should reserves be designed?

• 20–50% of the ocean should be protected in no-take reserves - How large? - How many?- Where?

• Involving fishers is crucial in coming up with answers


Conclusion

• Oceans cover most of our planet and contain diverse topography and ecosystems

• As we learn about oceans and coastal environments, we are intensifying our use of their resources and causing severe impacts

• We need to address acidification, loss of coral reefs, pollution, and fisheries depletion

• Setting aside protected areas can maintain and restore natural systems and enhance fisheries

• Consumer choices can help us move toward sustainable fishing


QUESTION: Review

A “downwelling” is defined as:

a) The vertical flow of cold, deep water towards the surface

b) The vertical flow of warm, deep water towards the surface

c) Oxygen-rich water sinks

d) Oxygen-poor water sinks


QUESTION: Review

The area of an ocean that contains habitats on the ocean floor is called the _______ zone.

a) Littoral

b) Photic

c) Pelagic

d) Benthic


QUESTION: Review

_____ is defined as “a mass of calcium carbonate composed of the skeletons of tiny animals”.

a) A Coral reef

b) Red tide

c) Bottomfish

d) Kelp


QUESTION: Review

Which statement about coral bleaching is correct?

a) Corals reproduce most efficiently in colder waters.

b) Fish move into coral reefs and kill them.

c) Zooxanthellae leave the coral due to climate change or pollution.

d) Coral reefs expand their range after they have been bleached.


QUESTION: Review

An area that occurs along coasts at temperate latitudes is called a(n):

a) Estuary

b) Mangrove swamp

c) Salt marsh

d) Coral reef


QUESTION: Review

Which of the following does NOT mask the decline of fisheries?

a) Fishing fleets travel longer distances to reach less-fished areas.

b) Fishing fleets spend more time fishing.

c) Fishing fleets use sophisticated methods of fishing.

d) Fleets fish in shallower waters nearer coasts.


QUESTION: Review

Marine reserves have all the following benefits EXCEPT:

a) Fishing increases in areas surrounding the reserve.

b) The size of fish decreases

c) Larvae can “seed” areas outside the reserve.

d) Decreased mortality and habitat destruction occur.


QUESTION: Viewpoints What would you think about letting another country

fish 10 miles off the U.S. coast?

a) That’s fine, as long as the fleet paid the United States.

b) Let them fish, but make them follow the same rules as U.S. fishermen.

c) Let only U.S. fishermen fish in these waters.

d) Prevent most fishing – we need to protect the last fish stocks.


QUESTION: Interpreting Graphs and Data

What does this graph show about the future of global fisheries catch?

a) China will apply major fishing pressure.

b) China’s role in fishing pressure will decline.

c) The world will decrease its fishing pressure.

d) The United States is not included in this graph.


QUESTION: Interpreting Graphs and Data

Which conclusion can you draw from this graph about commercial catches of Atlantic cod?

a) Intensified fishing increased and the fishery crashed.

b) It is easier to find fish today.

c) There is little correlation between fishing and fish stocks.

d) Moratoria will bring the stocks back.

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