Ch. 16 Notes APES This chapter will help you … · Ch. 16 Notes APES 1 This chapter will help you...
Transcript of Ch. 16 Notes APES This chapter will help you … · Ch. 16 Notes APES 1 This chapter will help you...
Ch. 16 Notes APES
1
This chapter will help you understand:
• The marine environment
• Ocean-climate relationships
• Marine ecosystems
• Marine pollution
• The state of ocean fisheries
• Marine protected areas and reserves
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 _______________ (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 _____% of Earth’s surface and contain __________% 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
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- 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 __________% 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 ___________________________
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 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
• _____________________________ zone
- Warmed by sunlight and stirred by wind
- Consistent water density
• _____________________________ = below the surface
zone
- Density increases with depth
• ___________________ zone = below the pycnocline
- Dense, sluggish water
- Unaffected by winds, storms, sunlight, or
temperature
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Ocean water flows horizontally in 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 __________________________’s climate
Currents form patterns across the globe
Vertical movement affects ecosystems
• ______________________________ = 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
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Currents affect climate
• Horizontal and vertical movement of oceans affects global and regional climates
• _______________________________ 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)
• _______________ = 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
• _________________________ 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
• ___________________________ = 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
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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 ____________________
- 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
• ____________________ zone = well-lighted top layer
- Absorbs 80% of solar energy
- Supports high primary productivity
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• _______________________________ = habitats and ecosystems between the ocean’s surface and floor
• _______________________________ = 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
• _______________ = 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
• _______________ ________________ = 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
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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
• _____________________ 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
• _______________________________ (littoral) ecosystems = where the ocean meets the land
- Between the uppermost reach of the high tide and the lowest limit of the low tide
• _______________ = 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
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• Temperature, salinity, and moisture change dramatically from high to low tide
• Sandy intertidal zones have slightly less biodiversity
Salt marshes line temperate shorelines
• _______________ ________________ = 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
• _________________________ = 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
• _______________________________= 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
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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
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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
• _____________________ 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
• __________ __________ = 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
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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
• ___________________________ 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
• _____________________ = the accidental capture of animals
• Drift netting drowns dolphins, turtles, and seals
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- 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
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Industrialized fishing is destroying fisheries
• Oceans today contain only one-tenth of the large-bodied animals they once did.
• 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
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
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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:
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- 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
Conclusions
• 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