Download Humans depend on the ocean for many reasons

Humans depend on the ocean for many reasons including food, transportation,
energy sources, and recreation. The use of resources from the world’s oceans
has had a major impact on the biodiversity in these ecosystems. Human activities
play an important role in changing the environment of the oceans.
Runoff is the flow of water that occurs when the soil is saturated and excess
water from rain, or other sources, flows over the land and can accumulate in
larger reservoirs of water including oceans. When runoff flows along the ground,
it can pick up contaminants, such as toxic chemicals or pollutants. Human
urbanization increases surface runoff by creating more impermeable surfaces
such as concrete and pavement that do not allow percolation of water down
through the soil and into the aquifer. Instead, water is forced directly into the
water source such as a river, lake, or ocean. When contaminants are dissolved in
runoff, the human impact creates water pollution that can have a detrimental
effect on water quality and the living organisms dependent on that water source.
Artificial reefs are man-made underwater structures built to promote marine life in
areas that typically have a flat, featureless bottom. They can be intentional by
placing unused or non-working structures that were once used for other purposes
such as old automobiles, buses, train cars, and oil rigs down to the ocean floor.
Artificial reefs can also occur unintentionally such as a ship that sinks during a
shipwreck. These artificial reefs provide hard surfaces where algae and
invertebrates such as coral, oysters, and barnacles can attach. As they grow and
accumulate, these reefs then provide a structure for habitats and food for other
marine life including many types of fish. Although they may be first used as
benefits for marine life, artificial reefs may have some environmental concerns.
These concerns include toxicity of some man-made structures, damage to
natural ecosystems, and even worsening the effects of overfishing by
accumulating fish into one area.
Current research shows the impacts of human activity on ocean ecosystems can
be seen worldwide and in every type of ecosystem found in the oceans. As
humans depend on resources from oceans on an increasing basis, the effects
raise environmental concerns. Activities such as overfishing, pollution from
dumping, pollution from shipping transportation, recreation use, runoff, and
coastal development all have had a major impact on some parts of the world’s
oceans. These impacts affect most marine life, coral and rocky reefs, seamounts,
estuaries, open waters, as well as shallow and deep ocean ecosystems. Most
human activities including using resources from the oceans have a major impact
on fragile marine ecosystems.
Oceans are Earth’s largest ecosystem. Ocean systems circulate energy and
ocean temperatures regulate Earth’s climate and weather.
Marine algae produce oxygen and consume atmospheric carbon and play an
important role in the cycling of matter for life on Earth.
Human activity such as runoff pollution can originate from small or large
sources on land and water, including motorized vehicles, oil spills, agricultural
chemicals, and recreation. Runoff pollution negatively affects beaches and ocean
habitats.
Overharvesting food from the ocean creates an imbalance in existing ocean
food webs. Other examples of the effects of human activity on oceans include
climate change, spread of disease, and introduction of exotic species.
Runoff and the Ocean
For many years, scientists believed that runoff from commercial farms can cause
excessive phytoplankton blooms. In 2005, Stanford University scientists were
able to finally prove that theory. Now we have verified the information we need to
better protect oceans from human pollution. How does this affect the ocean
ecosystem and the human food chain? To answer that, we need to understand
how humans interact with the ocean.
The ocean ecosystem is more sensitive than it looks. We can see with the naked
eye that plants and fish live in a delicate balance. Schools of fish move through
the ocean in ways that do not put too much pressure on any one source of food.
Different populations are kept in check by both the amount of food available and
their predators. We must use scientific methods, however, to see that amounts of
tiny molecules like nitrogen and oxygen also have a profound affect on ocean
ecosystems.
The ocean drives Earth’s water cycle. All but 3% of the water on Earth is in the
ocean. It also strongly influences Earth’s climate because much of the Sun’s heat
is absorbed by the ocean. We get many resources from the ocean, such as tuna,
shrimp, fish, crab, kelp, and blubber, among many others. The ocean influences
all life on Earth. That is why it is very important that we are aware of how we
affect ocean systems.
Water that travels over the ground and drains into a stream, lake, river, or ocean
is called runoff. Most runoff comes from rain, but pollution in the runoff often
comes from water that has been used for agricultural purposes. This is water that
has been used to irrigate the plants that farmers grow. Sometimes this water can
collect contaminants from the ground as it rolls downhill. These contaminants can
include lead, nitrogen, and phosphorus. Nitrogen is a chemical element that
many farmers use to increase crop yields. It is the “active” ingredient in manure
and many other plant fertilizers. Unfortunately, it has the same affect on ocean
plants. This introduction of additional plant fertilizer into the ocean changes the
balance of ocean plant growth. This can have serious consequences for ocean
wildlife.
Phytoplankton are microscopic algae that live in the ocean. Phytoplankton form
the base of the aquatic food chain. Thousands of marine organisms rely on
phytoplankton for food. Individually they are too small to be seen. They can be
easily seen as a green color in the water when millions of phytoplankton are
together. The chlorophyll in their bodies causes the green color. When
phytoplankton quickly increase in numbers, these large concentrations of them
are called “algal blooms.” Algal blooms have been happening naturally since man
has been recording observations about the ocean. However, we have now begun
to understand the relationship between contaminated runoff and ocean algal
blooms.
Algal blooms can cause hypoxic (low-oxygen) areas in waters. As the short-lived
algae die, oxygen is taken from the water to help bacteria decompose their
bodies. Hypoxic areas, or dead zones, are places where most oxygen dependent
life forms cannot live. Dead zones can cause fish kills and other events where
large amounts of marine organisms die.
The scientists at Stanford University were the first to prove the connection
between nitrogen in runoff water and algal blooms. They studied aerial photos of
the Gulf of California. The land surrounding the Gulf of California is used heavily
for agriculture. Hundreds of thousands of acres are used as farm land. Farmers
fertilize these farms four times per year. They spray their crops with a nitrogenbased fertilizer. The fertilizer collects in the runoff and drains into the ocean. The
researchers discovered that there was always an algal bloom within days of this
fertilization cycle.
Algal blooms can cause major problems for both aquatic life and commercial
fisheries. It is important to understand how humans can cause — and prevent —
abnormally concentrated algal blooms.