Lecture Outlines Chapter 16 Environment: The Science behind the Stories 4th Edition Withgott/Brennan

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

Lecture Outlines Chapter 16 Environment: The Science behind the Stories 4th Edition Withgott/Brennan