What Are Biological Dead Zones and
How Do They Form?
Have you ever heard the term dead
zone used in the context of oceans
or lakes? A biological dead
zone refers to an area in a body of
water where oxygen levels are so low
that most marine life cannot survive.
These zones are called hypoxic
zones or anoxic zones, depending
on the level of oxygen depletion. In
this article, we will explore what
biological dead zones are, how they
form, and why they are a serious
problem for marine life.
How Do Dead Zones Form?
A biological dead zone is caused by an excess of certain
nutrients in the water especially nitrogen and phosphorus.
These nutrients come from a variety of sources, often due
to human activities.
For example:
•
• Fertilizers: Farmers use
fertilizers to help crops
, grow, but when it rains, these fertilizers often wash off
elds and into nearby rivers, lakes, and oceans.
•
• Sewage: Wastewater from homes, factories, and
sewage plants can also contain high levels of nitrogen
and phosphorus.
•
• Runoff from cities: Rainwater that runs off streets,
roads, and parking lots can carry pollutants like oil, pet
waste, and chemicals into nearby water bodies.
•
• Animal waste: Large farms that raise animals can
release nutrients from manure into rivers and lakes.
When these nutrients enter the water, they create an
environment that supports the rapid growth of tiny
organisms called algae. This growth is known as an algal
bloom. While algae are a natural
part of healthy aquatic
ecosystems, too many nutrients
cause the algae to grow
uncontrollably. Algal blooms can
cover the surface of the water,
blocking sunlight from reaching
plants below the surface, which
can harm underwater vegetation.
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How Do They Form?
Have you ever heard the term dead
zone used in the context of oceans
or lakes? A biological dead
zone refers to an area in a body of
water where oxygen levels are so low
that most marine life cannot survive.
These zones are called hypoxic
zones or anoxic zones, depending
on the level of oxygen depletion. In
this article, we will explore what
biological dead zones are, how they
form, and why they are a serious
problem for marine life.
How Do Dead Zones Form?
A biological dead zone is caused by an excess of certain
nutrients in the water especially nitrogen and phosphorus.
These nutrients come from a variety of sources, often due
to human activities.
For example:
•
• Fertilizers: Farmers use
fertilizers to help crops
, grow, but when it rains, these fertilizers often wash off
elds and into nearby rivers, lakes, and oceans.
•
• Sewage: Wastewater from homes, factories, and
sewage plants can also contain high levels of nitrogen
and phosphorus.
•
• Runoff from cities: Rainwater that runs off streets,
roads, and parking lots can carry pollutants like oil, pet
waste, and chemicals into nearby water bodies.
•
• Animal waste: Large farms that raise animals can
release nutrients from manure into rivers and lakes.
When these nutrients enter the water, they create an
environment that supports the rapid growth of tiny
organisms called algae. This growth is known as an algal
bloom. While algae are a natural
part of healthy aquatic
ecosystems, too many nutrients
cause the algae to grow
uncontrollably. Algal blooms can
cover the surface of the water,
blocking sunlight from reaching
plants below the surface, which
can harm underwater vegetation.
fi
