Environment: The Science behind the Stories 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 a 31

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 oil spills cause severe environmental and economic problems Major spills make headlines Foul beaches Coat and kill animals Devastate fisheries Countless non-point sources produce most oil pollution Small boat leaks, runoff

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 … Rules and technology have decreased dolphin deaths Other animals (e.g., sharks) are still caught Dolphins have not recovered Too few fish to eat

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 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

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: The vertical flow of cold, deep water towards the surface The vertical flow of warm, deep water towards the surface Oxygen-rich water sinks Oxygen-poor water sinks Answer: c 64

QUESTION: Review The area of an ocean that contains habitats on the ocean floor is called the _______ zone. Littoral Photic Pelagic Benthic Answer: d 65

QUESTION: Review _____ is defined as “a mass of calcium carbonate composed of the skeletons of tiny animals”. A Coral reef Red tide Bottomfish Kelp Answer: a 66

QUESTION: Review Which statement about coral bleaching is correct? Corals reproduce most efficiently in colder waters. Fish move into coral reefs and kill them. c) Zooxanthellae leave the coral due to climate change or pollution. Coral reefs expand their range after they have been bleached. Answer: c 67

QUESTION: Review An area that occurs along coasts at temperate latitudes is called a(n): Estuary Mangrove swamp Salt marsh Coral reef Answer: c 68

QUESTION: Review Which of the following does NOT mask the decline of fisheries? Fishing fleets travel longer distances to reach less-fished areas. Fishing fleets spend more time fishing. Fishing fleets use sophisticated methods of fishing. Fleets fish in shallower waters nearer coasts. Answer: d 69

QUESTION: Review Marine reserves have all the following benefits EXCEPT: Fishing increases in areas surrounding the reserve. The size of fish decreases Larvae can “seed” areas outside the reserve. Decreased mortality and habitat destruction occur. Answer: b 70

QUESTION: Viewpoints What would you think about letting another country fish 10 miles off the U.S. coast? That’s fine, as long as the fleet paid the United States. Let them fish, but make them follow the same rules as U.S. fishermen. Let only U.S. fishermen fish in these waters. Prevent most fishing – we need to protect the last fish stocks. Answer: any 71

QUESTION: Interpreting Graphs and Data What does this graph show about the future of global fisheries catch? China will apply major fishing pressure. China’s role in fishing pressure will decline. The world will decrease its fishing pressure. The United States is not included in this graph. Answer: a 72

QUESTION: Interpreting Graphs and Data Which conclusion can you draw from this graph about commercial catches of Atlantic cod? Intensified fishing increased and the fishery crashed. It is easier to find fish today. There is little correlation between fishing and fish stocks. Moratoria will bring the stocks back. Answer: a 73