Environmental Science
Chapter 4, section 4.4
Name: ______________________________
NOTES
Kinds of Ecosystems
4.4 Marine Ecosystems
• The oceans of the world contain a wide variety of plants and animal communities
• The types of organisms present in marine ecosystems depend on temperature and the amount of sunlight
and nutrients are available.
Estuaries
• An ecosystem where fresh water from rivers mixes with the salt water from the ocean; mineral rich soil;
a nutrient trap; in shallow areas, marsh grass grows
• One week each spring, huge snowshoe crab crawl out of the ocean onto the beaches of the Delaware
Bay to mate and lay their eggs. Shorebirds wait for them and millions of migrating birds will stop
there to gorge on the eggs
Estuaries: Plant and Animal Adaptations
• Among the most productive ecosystems; contain plenty of light, nutrients for plants
• Rivers supply nutrients washed from the land; water is shallow; sunlight reaches the bottom
• Can support large amounts of plants, phytoplankton and zooplankton which provide food for larger
animals (fish, dolphins, manatees, seals, other mammals)
• Oysters, barnacles, clams live anchored to marsh grass or on the bottom and filter algae and debris out of
the water
• Organisms can tolerate variations in salinity
Threats to Estuaries
• Many of the world’s major ports are built on estuaries; seven of the ten largest urban areas (Tokyo, New
York, Shanghai, Calcutta, Buenos Aires, Rio de Janeiro, Bombay)
• Were used as dumping grounds, especially in California; now, plans are to restore them to estuary
wetlands
• Industrial waste, agricultural runoff, pesticides, fertilizers damage estuaries
• Most of the pollutants will break down over time, but estuaries cannot cope with the large amounts
produced by humans
Coral Reefs
• Limestone islands in the sea that are built by coral animals called polyps (very slow growing); thousands
of species of plants and animals live in the cracks and crevices; among the most diverse ecosystems
on Earth
• Corals live in only warm salt water; a lot of light for photosynthesis; shallow, tropical seas
Coral Reefs: Animal Adaptations
• Coral Polyps are predators that never chase their prey; use stinging tentacles to capture small animals
that float or swim too close
• Provide habitats for a variety of tropical fish, snails, clams, sponges
• Parrotfish have teeth fused into their beaks which they use to scrape algae and corals off the reefs to eat
Threats to Coral Reefs
• If they get too hot or too cold, or fresh water drains into the water surrounding the reef, corals cannot
produce limestone.
• If it is too muddy, too polluted, too high in nutrients, algae will die or grow out of control and smother
the corals
• Oil spills, sewage, pesticides, silt runoff are linked to coral-reef destruction
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Overfishing can devastate fish populations, upsetting the balance
Reef cannot repair itself after being destroyed by careless divers, shipwrecks, anchors, people breaking
off pieces
The Ocean
• Covers nearly ¾ of Earth’s surface
• Plants only grow where there are nutrients and light; most life is in shallow water around the edges of
continents; abundant with plants and animals in these areas
• Open ocean, phytoplankton grows near the surface (sunlight) if there are nutrients; one of the least
productive of all ecosystems
• The depths of the ocean are dark and most of the food consists of dead
Ocean: Plant Adaptations
• No flowering plants except around the edges
• Food for herbivores in the open ocean are phytoplankton (floating by being buoyant or having long
spines; whip-like flagella; oil droplets)
• When they die, they sink to the bottom
Ocean: Animal Adaptations
• Smallest herbivores are the zooplankton (jellyfish, tiny shrimp, fish larvae) which live near the surface;
others (oysters, lobsters) live at the bottom
• Dozens of fish, as well as seals and whales (mammals) feed on plankton
• Evolved sleek, tapered shapes for moving through dense water; silvery color (protective camouflage);
buoyancy devices to stay at one level (sharks –oily livers; bony fish – gas-filled swim bladders;
mammals – lungs
• Sunlight penetrates about 100 m (330 ft) into the sea; no light below that (decomposers, filter feeders
and organisms that eat them live here)
• Poor visibility at these depths so organisms use “light” to communicate (luminous) or sound (whales –
“songs”; dolphins – clicks and calls
Threats to the Ocean
• Pollution – comes from the land; same as the pollutants on the land (fertilizers causing toxic algal
blooms; industrial waste; sewage discharged into rivers, particularly from nuclear power plants)
• Overfishing and some fishing methods have destroyed fishing grounds, nets entangling every living
thing bigger than the holes (most of the catch are not used and are thrown back, dead); marine
mammals drown; fishing lines are discarded in the ocean and strangle fish, seal
• All of these things are reducing reproduction thus endangering many species
Polar Ecosystems
• Ice covered North and South Pole are considered marine ecosystems because most of the food supply is
phytoplankton
• South Pole lies on the continent of Antarctica and is covered with a permanent icecap (melts only
around the edges); North Pole is not on land at all; lies in the Arctic Ocean, frozen into a huge
iceberg throughout the year with little icebergs floating around it
The Arctic
• Relatively shallow; rich in nutrients; supports large populations of plankton
• This provides food for a diversity of fish, whales, ocean birds (who prey on the fish), seals
• The birds and seal bear their young on the ice; they provide food for the few humans that live there and
for the polar bear
The Antarctic
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Only continent never colonized by humans
Used mainly for research on the unusual animals that live there
Only a few plants live there
Plankton forms basis of the food chain; feeds fish, whales, penguins
Threats to Polar Ecosystems
• Contains reserves of minerals (oil) whose extraction would disrupt this large untouched ecosystem
• Conservationists want it made into a world wildlife refuge
• Main threat is tourism (garbage left behind, does not decay because it is so cold)
• They are working to solve that problem