Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually these organisms die and decompose. Decomposition uses up all the dissolved oxygen in the water. Without oxygen, large numbers of plants, fish, and bottom-dwelling animals die. Every year dead zones appear in lakes and nearshore waters. A dead zone is an area of hundreds of kilometers of ocean without fish or plant life. The Mississippi is not the only river that carries the nutrients necessary to cause a dead zone. Rivers that drain regions where human population density is high and where crops are grown create dead zones all over the world (Figure 1.2).
Most ocean pollution comes as runoff from land and originates as agricultural, industrial, and municipal wastes (Figure 1.1). The remaining 20% of water pollution enters the ocean directly from oil spills and people dumping wastes directly into the water. Ships at sea empty their wastes directly into the ocean, for example. Coastal pollution can make coastal water unsafe for humans and wildlife. After rainfall, there can be enough runoff pollution that beaches must be closed to prevent the spread of disease from pollutants. A surprising number of beaches are closed because of possible health hazards each year. A large proportion of the fish we rely on for food live in the coastal wetlands or lay their eggs there. Coastal runoff from farm waste often carries water-borne organisms that cause lesions that kill fish. Humans who come in In some areas of the world, ocean pollution is all too obvious. contact with polluted waters and affected fish can also experience harmful symptoms. More than one-third of the shellfish-growing waters of the United States are adversely affected by coastal pollution.
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this contaminant gets washed from farms and yards into rivers, causing algae to grow.
a) toxins b) pesticides --> c) fertilizers d) all of the above
_____ can become runoff that travels from the land to the ocean where it becomes a marine pollutant.
a) agricultural waste b) industrial waste c) municipal waste --> d) all of the above
most ocean pollution comes from runoff while the remaining 20% of water pollution comes from ____.
a) oil spills b) people dumping wastes directly in water --> c) both a and b d) none of the above
humans can be affected by ocean pollution when they
a) eat contaminated fish. b) swim in contaminated water. c) engage in ocean sports. --> d) all of the above.
fertilizers create dead zones when
--> a) they cause the algae population to explode. b) they cause the fish population to explode. c) they take all the oxygen out of the water. d) none of these.
most ocean pollution comes from land and is found in or near coastal regions.
--> a) true b) false
fish are affected by oceanic pollutants, but humans are not affected because they do not live in the ocean.
a) true --> b) false
in what ways do fish rely on coastal wetlands?
a) for food b) to lay their eggs c) shelter --> d) all of the above
ships at sea treat their wastes and bring their trash back to land for recycling.
a) true --> b) false
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