Download 14 Ocean Zones

Chapter 14: Ocean Zones
Section 1: Exploring the Ocean
1. Learning About the Ocean
a. People have studied the ocean since ancient times because the ocean provides food and serves as a route
for trade and travel
b. Trading Routes
i. Phoenicians—Mediterranean Sea
1. By 1200 B.C. they established sea routes for trade with other nations
2. 2,000 years ago, Polynesians sailed into open ocean—settled Hawaii, Tahiti, & New Zealand
c. Scientific Discoveries
i. Captain James Cook was hired by British Government in 1700s to lead 3 voyages of exploration
ii. Challenger—expedition marking the beginning of modern oceanography
d. Exploring the Ocean Floor
i. Studying the ocean floor is difficult
1. Very deep…Average depth = 3.8 kilometers
2. Totally dark
3. Very Cold
4. Tremendous pressure
ii. Scientists have developed ways to investigate and gather information
1. One method—lower a weight on a long line into the water until it reached the bottom
a. Used by the Challenger’s crew
b. Slow and inaccurate method
2. Sonar—Sound navigation and ranging
a. Uses sound waves to calculate the distance to an object
2. The Ocean Floor
a. Includes continental shelf, continental slope, abyssal plain, and mid-ocean ridge
b. Shallow Water
i. Continental shelf: gradually sloping area that borders each continent
ii. Extends outward from a continent
iii. Continental slope: incline beyond the edge of the continental shelf
1. At a depth of about 130 meters
c. Open Ocean
i. Seamounts are mountains whose peaks do not break the surface of the ocean water
ii. Abyssal plain: a smooth, nearly flat region of the ocean covered with thick layers of mud and silt
iii. Mid-ocean ridge: made up of a range of mountains that winds through the oceans
d. Deepest Depths
i. Trench: deep canyons in the ocean floor
3. Ocean Zones
a. Include the intertidal zone, the neritic zone, and the open-ocean zone
i. Intertidal zone: begins at the highest high-tide line and extends out to the lowest low-tide line
ii. Neritic zone: extends from the low-tide line out to the edge of the continental shelf
iii. Open-ocean zone: beyond the edge of the continental shelf
Section 2: Ocean Habitats
1. Life in the Ocean
a. Organisms inhabit the ocean at every depth
i. Marine organisms are classified into 3 categories according to where they live and how they move
ii. Plankton: tiny algae and animals that float in the water and are carried by waves and currents
1. Include diatoms, crustaceans—copepods, and some tiny young fish
iii. Nekton: free-swimming animals that can move throughout the water column
1. Include squid, most fishes, and marine mammals—whales, and seals
iv. Benthos: organisms that inhabit the ocean floor
1. Include crabs, sea stars, octopus, and lobsters—which move from place to place
2. Some stay in one place—sponges and sea anemones
b. Relationships Among Organisms
i. Plankton, nekton, and benthos are found in most marine habitats
1. Many plankton and benthos are algae
2. Algae use sunlight to produce their own food through photosynthesis
3. Photosynthetic plankton are called producers
4. Other plankton and benthos, as well as nekton, eat algae or other organisms
a. They are called consumers
5. Some organisms, decomposers, break down wastes and the remains of other organisms
ii. Ocean Food Webs
1. Food web: the feeding relationships in a habitat
2. In the ocean, each organism depends either directly or indirectly on the algae plankton
3. The biggest sharks and whales feed directly on plankton
2. The Intertidal Zone
a. The three major habitats in the intertidal zone are estuaries, sandy shores, and rocky shores
i. Organisms must be able to tolerate changes in the salinity and temperature of the water, as well as
periods of being underwater and periods exposed to the air.
ii. Must avoid drying out, hide from predators, and find food in the harsh setting
b. Estuaries: coastal inlets or bays where fresh water from rivers mixes with salty ocean water
i. Water that is partly salty and partly fresh is brackish
ii. Serve as valuable nurseries for fish and shellfish
iii. Serve as valuable feeding and resting areas for birds and land animals
iv. Found on coasts wherever a river meets the ocean
1. Ex: Chesapeake Bay
a. Rich source of oysters, clams, and blue crabs
b. Valuable feeding and resting stop for migrating birds
2. Ex: Monterey Bay—California
a. Contains Monterey Bay National Marine Sanctuary—one of the nation’s largest
research facilities and sanctuaries for ocean animals
c. Mangrove Forests
i. Most wetlands along the coasts of the US are either mangrove forests or salt marshes
1. Mangroves are short, twisted trees that grow in brackish water
2. Found in Florida and along the Gulf of Mexico
3. Mangroves’ arching roots anchor the trees to the land
a. Roots create a protected nursery, rich in nutrients, for many animals
4. Mangroves can absorb force of wind and waves
d. Salt Marshes
i. Oozes with smelly mud
1. Made of sediments, animal and plant matter, and nutrients carried into the marsh by fresh
water and tides
ii. Common along the east coast from Massachusetts to Florida
iii. Cordgrass—most common plant—can survive in salt water
1. Some is eaten by animals
2. The rest is decomposed by bacteria and fungi—provides nutrients to organisms
iv. Tidal channels run through cordgrass
1. Waves break up as they enter the channels
2. Fish, crabs, shrimp, and oysters hatch and feed
3. Crabs search for food in rich mud during low tide
4. Birds such as herons and stilts prey on the crabs and other benthos exposed by low tide
e. Sandy Shores
i. On all the ocean coasts of the United States
ii. Most animals live underground
1. Must tolerate changing water levels and temperatures, crashing waves, and a sandy
surface that is always moving
2. Animals such as clams, sand dollars, and sand crabs burrow for protection
f. Rocky Shores
i. Found along much of both US coasts
ii. The highest rocks, above the highest high-tide line, make up the spray zone
1. Never completely covered with water
2. Stripe of black algae indicates the highest high-tide line
iii. Rocks below this layer are covered with barnacles
1. Barnacles can close up their hard shells
a. Traps a drop of water to keep from drying up
2. Rocks are home to limpets, flat animals with a large, muscular foot used to hold tight
a. Release drops of mucus around the edges of the shells to form tight seal
g. Tide Pools
i. Some water remains in depressions among the rocks when a tide retracts
1. These puddles are called tide pools
2. Once water evaporates, the remaining water becomes saltier
a. After it rains, salinity decreases
3. Organisms must be able to withstand changes in temperature and salinity
ii. Sea stars cling to the rocks with rows of tiny suction cups
iii. Spiny sea urchins can use its spines to dig a hole when the bottom is sandy
iv. Sponges and sea anemones wait for the incoming tide to bring plankton and other food particles
under shady rock ledges
v. Some sea anemones can survive out of water for more than two weeks by pulling in its tentacles
and folding up into a round blob
3. Conditions in the Neritic Zone
a. Extends from the low-tide line out to the edge of the continental shelf
i. Contains a larger variety of organisms than any other ocean zone
ii. Most of the world’s major fishing grounds are found in this zone
b. Home to so many things because it is located over the continental shelf
i. The shallow water over the continental shelf receives sunlight and a steady supply of nutrients
washed from the land into the ocean—light and nutrients enable large algae to grow
1. These algae serve as food source and shelter for other organisms
ii. Upwelling brings additional nutrients to the surface which support large numbers of plankton
1. Plankton serve as the base of the ocean food webs
2. Schools of fish feed on the plankton
4. Coral Reefs
a. Another type of diverse habitat found in the neritic zone
i. Made of living things and their remains
ii. Created by colonies of tiny coral animals that produce a hard structure around their bodies
1. The empty structure remains after the coral dies
2. New coral animals attach to it and grow, building a reef over many years
b. Environment of Coral Reefs
i. Microscopic algae live in the bodies of the coral animals and provide food for the corals
ii. Algae need warm temperatures and sunlight
1. Therefore, coral can only form in shallow, tropical waters
iii. Reefs grow above continental shelves or around volcanic islands, where water is shallow
5. Ring-Shaped Reefs
a. A reef may develop into an atoll where the seafloor is sinking
i. Atoll: a ring-shaped reef surrounding a shallow lagoon
ii. Begins as a fringing reef that closely surrounds island
1. The island sinks as the seafloor sinks, while the reef grows upward
2. Water separates the top of the barrier reef from the island
3. Island continues to sink until it is submerged, forming the atoll
b. Life Around a Reef
i. Coral can form in a variety of shapes as suggested by the names of coral species
1. Elkhorn, brain, plate, star
ii. Coral-reef animals include octopuses, spiny lobsters, shrimp, and fishes in all colors and sizes
iii. Parrotfish scrape coral off the reef to eat
1. They grind up the broken coral inside their bodies, producing the fine, soft sand commonly
found around the reef
6. Kelp Forests
a. Stalks of giant kelp gently sway back and forth below the water’s surface
i. Sunlight filters through the water, producing a greenish light
ii. Small bulbs at the base of each frond keep heavy fronds upright in the water
b. Environment of Kelp Forests
i. Grow in cold neritic waters where the ocean has a rocky floor
ii. Kelp are large, heavy algae, and require a solid, rocky bottom to anchor stalks
1. A holdfast, a bundle of rootlike strands, attaches algae to the rocks
2. Can grow to 30 meters
c. Providing a Habitat
i. Kelp use sunlight and dissolved gases in the neritic zone to produce their own food
ii. Curtains of kelp hide young gray whales from predators while their mothers are feeding
iii. Sea slugs and snails live amid the tangle of the holdfasts
iv. Sea otters eat abalone and sea urchins, which eat the kelp
7. Conditions in the Open Ocean
a. Begins where the neritic zone ends, at the end of the continental shelf
i. Only a small part of the open ocean receives sunlight
ii. The water has fewer nutrients
iii. Open ocean, thus, supports fewer organisms
iv. Sunlight penetrates only a short distance into the water
1. In clear tropical waters, sunlight may reach as deep as a few hundred meters
b. The Surface Zone
i. The surface zone extends as far as sunlight reaches below the surface
1. Only part of the open ocean that receives enough sunlight for algae
a. Base of open-ocean food webs
2. Animal plankton that feed on algae include krill, crabs, mollusks, and fishes
c. The Transition Zone
i. Extends from the bottom of the surface zone to a depth of about 1 km
ii. Water is darker and colder than in the surface zone
d. The Deep Zone
i. Water is even darker and colder than in the transition zone
ii. Often compared to a desert since few organisms live in the deep ocean
iii. Finding food in the dark is a challenge
1. Many deep-sea fishes produce their own light
2. Bioluminescence: the production of light by living things
a. Produced by chemical reactions
b. Sometimes in bacteria on the bodies of fishes
c. Others, the chemical reactions take place in the bodies of the fishes
d. The anglerfish has a light organ on its head
i. Shrimp and fishes attracted to the light become prey
iv. Animals in the deep zone must be good hunters to survive
1. Gaping mouths are often filled with fanglike teeth
e. Hydrothermal Vent: an area where ocean water sinks through cracks in the ocean floor, is heated by the
underlying magma, and rises again through the cracks
i. Supports organisms of an unusual number, variety, and size
ii. Heated water carries gases and minerals from Earth’s interior
1. Bacteria use these chemical nutrients to produce food
2. These bacteria form the base of the food web at a hydrothermal vent
3. Giant clams and other organisms feed on the bacteria
4. Red-tipped tube worms are supplied with food by bacteria living within their tissues
5. Scuttling crabs feed on the remains of the other inhabitants of their unusual habitat
Section 3: Resources From the Ocean
1. Living Resources
a. People depend heavily on fishes and other ocean organisms for food
i. Ocean organisms also provide materials that are used in products such as detergents and paints
b. Harvesting Fish
i. Many fish are caught to be eaten
1. Anchovies, Pollock, mackerel, herring, and tuna
a. Caught from coastal areas or areas of upwelling
ii. Fisheries naturally renew themselves each ear if used wisely
1. Overfishing causes a decrease in the fish supply
iii. Technology enables people to catch large numbers of fish quickly
c. Aquaculture: the farming of saltwater and freshwater organisms
i. Likely to become more common as fish stocks decrease
ii. Involves creating an environment for the organisms
1. Have controlled nutrient levels, temperature, light, and other factors
2. Salmon are now being raised in Nebraska fields that once were cattle ranches
iii. Drawback—clearing mangrove forests
d. Other Ocean Products
i. Algae is an ingredient in many household products
1. Detergents, shampoos, cosmetics, paints, and ice cream
ii. Diatoms are used for abrasives and polishes
iii. Other organisms may be useful for medications in the future
2. Nonliving Resources
a. Include water, fuels, and minerals
b. Water
i. Desalination allows fresh water to be extracted from ocean water
1. Provides fresh water for dry areas and islands
c. Fuels
i. Remains of dead marine organisms sink to the bottom of the ocean and are buried
ii. Heat and pressure over thousands of years transform remains into oil and natural gas
1. Richest deposits are often on the continental shelves
iii. Oil rigs drill as much as 300 meters below the surface into rocky floor
d. Minerals
i. Solid substances that are obtained from the ground and the water
ii. Salts left behind are a valuable mineral resource
1. More than half of the world’s magnesium is obtained from seawater
iii. Gravel and sand covering the continental shelves are mined for use in construction
iv. Diamonds and gold can be mined from sand deposits
v. Metals like manganese accumulate on the ocean floor
1. Nodules: the metals concentrate around pieces of shell, forming black lumps
a. Sometimes as deep as 5,000 meters
3. Ocean Pollution
a. The ocean can absorb some wastes without permanent damage, but dumping large amounts of wastes
threatens marine organisms
i. Most ocean pollutants come from land and related to human activities
b. Natural Occurrences
i. Some is the result of weather
1. Surge of freshwater lowers salinity—can kill saltwater organisms
c. Human Activities
i. Sewage, chemicals, and trash dumped into coastal waters
ii. Runoff from fields and roads can end up in the ocean
iii. Poison build up in animals can harm other animals, or people, that eat them
iv. Air-breathing marine mammals can drown if they get tangled up in fishing lines or nets
v. Others swallow plastic bags that block their stomachs
vi. Oil Pollution
1. Oil from a spill can coat animal bodies, destroying their insulation and ability to float
2. Also harmful when swallowed
3. Certain bacteria feed on the oil and multiply—eventually clean up oily beach
d. Protecting Earth’s Oceans
i. The world ocean is a continuous body of water that has no boundaries, making it difficult to
determine who, if anyone, should control portions of it
ii. United Nations has established different ocean boundaries
1. A nation controls the first 22 km out from its coast
a. Also-controls resources in waters or on continental shelf within 370 km of shore
2. Half of ocean’s surface waters, or “high seas,” are not owned by any nation
iii. International efforts aim at reducing pollution
1. Include establishment of marine refuges and regulations on oil tankers