Level 1 — Absolute Beginner
Water needs oxygen. Fish and other animals in water need oxygen to breathe.
Scientists say oceans, lakes, and rivers are losing oxygen. This is happening around the world.
The oceans have already lost some of their oxygen since long ago. Scientists think more oxygen will disappear.
Less oxygen is bad for fish. It can also hurt Earth's climate.
- oxygen
- a gas that living things need to breathe and survive
- ocean
- a huge area of salt water covering most of the Earth
- river
- a long, flowing body of fresh water
- disappear
- to stop existing or to no longer be seen
- climate
- the usual weather patterns of a place over a long time
- aquatic
- living or happening in water
- warn
- to tell someone about a possible danger
- damage
- harm caused to something
Level 2 — Elementary
A new scientific study warns that oxygen is disappearing from oceans, lakes, rivers, and coastal waters around the world at a worrying pace.
Researchers say this loss of oxygen threatens fish and other water animals, and it also weakens natural processes that help keep Earth's climate stable.
The world's oceans have already lost about 2 percent of their dissolved oxygen since the middle of the twentieth century, and scientists predict that another 1 to 7 percent could disappear by the end of this century if warming continues.
The main causes are human-driven warming, too many nutrients polluting the water, and changes in how deep ocean water mixes and moves.
- dissolved
- mixed completely into a liquid
- coastal
- located near the coast, or edge of the sea
- pace
- the speed at which something happens
- nutrient
- a substance that provides nourishment, but can cause pollution in excess
- pollution
- harmful substances that damage the environment
- stable
- steady and not likely to change suddenly
- predict
- to say what will happen in the future
- human-driven
- caused mainly by human activity
Level 3 — Intermediate
A new study led by researchers at the Scripps Institution of Oceanography at the University of California, San Diego, and published in the journal Limnology and Oceanography, warns that oxygen is vanishing from oceans, lakes, rivers, and coastal waters worldwide at a pace that scientists describe as alarming.
The researchers report that the world's oceans have already lost roughly 2 percent of their dissolved oxygen since the mid-twentieth century, and climate projections suggest that another 1 to 7 percent could vanish by the century's end if global warming continues on its current trajectory.
Aquatic deoxygenation, the scientific term for this process, is driven primarily by human-caused warming, excess nutrient pollution from agriculture and wastewater, and shifts in how interior waters are ventilated, or mixed with oxygen-rich surface water.
Even relatively modest reductions in dissolved oxygen can force fish populations to migrate away from affected areas, reduce reproductive success, increase disease among aquatic species, and shrink the habitats suitable for many forms of marine and freshwater life.
- vanishing
- disappearing gradually
- trajectory
- the path or direction something is following over time
- deoxygenation
- the process of losing oxygen from a body of water
- wastewater
- water that has been used and contains waste, requiring treatment
- ventilated
- supplied with fresh air or, in water, mixed and exchanged with oxygen
- reproductive success
- the ability of a species to successfully produce offspring
- habitat
- the natural environment where a plant or animal normally lives
- freshwater
- water that is not salty, such as in lakes and rivers
Level 4 — Advanced
A study spearheaded by researchers at the Scripps Institution of Oceanography at UC San Diego, published in the journal Limnology and Oceanography, warns that dissolved oxygen is vanishing from oceans, lakes, rivers, and coastal waters at a rate the authors characterize as alarming, with implications extending well beyond aquatic ecosystems.
The researchers document that the world's oceans have already shed approximately 2 percent of their dissolved oxygen since the mid-twentieth century, while climate projections indicate that a further 1 to 7 percent could be lost by century's end should current warming trajectories persist unabated.
Aquatic deoxygenation is attributed principally to anthropogenic warming, excess nutrient loading originating from agricultural runoff and inadequately treated wastewater, and disruptions to the ventilation processes by which interior water masses exchange with oxygen-rich surface layers.
Even comparatively modest reductions in dissolved oxygen can compel fish populations to migrate from affected regions, diminish reproductive success, elevate disease incidence among aquatic organisms, and contract the habitable range available to numerous marine and freshwater species, with researchers cautioning that some resulting changes may prove irreversible within human timescales.
- spearheaded
- led or directed an effort or project
- anthropogenic
- originating from human activity
- nutrient loading
- the accumulation of excess nutrients entering an ecosystem
- runoff
- water that flows over land, often carrying pollutants, into rivers or seas
- unabated
- without any reduction in intensity
- incidence
- the rate at which something occurs
- contract
- to become smaller or reduced in size
- irreversible
- impossible to change back to a previous state
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