Transcript Current Threats to Marine Mammals

Current Threats to Marine
Mammals
By Tim Chin
Current Threats
◊ Pollution
◊ Overfishing
◊ Entanglement
◊ Other
Pollution
◊ Noise
◊ Oil
◊ Chemical
◊ Plastics and Debris
◊ The Plastic Sea
Noise Pollution
◊
Many cetaceans, such as certain
whales and dolphins, rely on
sound for communication and
locating food. They are adversely
affected by human-made noise.
◊
Noise pollution can come from a
wide variety of sources, with some
of those being ship traffic, seabed
drilling, seismic surveys, sonars,
oceanographical experiments,
recreational activities, and
underwater explosions.
Noise Pollution
◊
Low levels of noise pollution are
enough to cause a change of
behavior in whales and dolphins.
They will generally try to escape
from the source of the noise,
which can result in them being
forced out of their habitat.
◊
Higher levels of noise pollution,
such as the sound of underwater
explosions, can cause great
discomfort and stress. It can even
result in physical acoustic trauma
in the form of tissue damage to
the ears.
◊
Cetaceans affected by high
intensity noise pollution, with
sonars being an example, are
likely to become stranded and die.
Oil Pollution
◊
Oil is another type of pollution
that negatively impacts marine
mammals. It is generally
introduced into the environment
through accidental spills.
◊
Oil is a compound that can
destroy the insulating properties
of a marine mammal’s skin.
Oil Pollution
◊
It is often the case that oil is
unintentionally eaten during
removal attempts. If ingested, the
toxic oil can damage a marine
mammal’s organs, which could
result in death.
◊
If inhaled, which is usually done
by whales and dolphins coming up
for air, the oil can cause
pneumonia.
◊
Many times it is overlooked, but
oil pollution can destroy the
habitats of marine mammals,
forcing them to travel elsewhere
or perish.
Chemical Pollution
◊
Chemical pollution is a type that
can contaminate the whole of a
marine food web.
◊
In a contaminated environment,
as smaller fish eat plankton, and
the larger fish eat the smaller fish,
the toxins that exist will greatly
accumulate in the bodies of large
fish.
◊
Since marine mammals are at the
top of their food chain, the high
levels of chemical pollutants in
their food will build up in their
bodies, in areas such as fatty
tissue and breast milk.
Chemical Pollution
◊
Marine mammals suffer from the
increasing concentrations of heavy
metals, PCBs, dioxins, DDT, and other
persistent organic pollutants that are
dumped or leaked into the ocean.
◊
Due to the bioaccumulation of
chemical pollutants, marine mammals
can suffer from a wide array of
illnesses and disruptions to their
normal body functions. Pesticides and
industrial compounds usually have a
negative impact on the endocrine,
digestive, and nervous systems, which
can lead to a decrease in health,
growth and development issues, a
weakened immune system, and
diminished reproductive abilities.
◊
Chemical pollutants can also cause
cancer.
Plastics and Debris
◊
Plastic and other debris in the
ocean are a large threat to the
wellbeing of marine mammals,
especially due to the fact that they
take a very long time to break
down.
◊
Studies suggest that over 60% of
the debris in the sea is plastic.
Plastics and Debris
◊
Plastic and other debris can easily
trap and get tangled on various
marine mammals. This can lead to
numerous complications.
◊
Marine mammals sometimes
mistake marine debris for food
and accidentally ingest it. This can
cause a blocking of the digestive
tract, choking, internal injuries,
and an accumulation of toxic
compounds. All of these
implications can be fatal.
The Plastic Sea
◊
Due to gyres, the circular currents
in the ocean, it is common for
plastic and other flotsam to build
up in certain areas.
◊
In the Pacific Ocean, between
California and Japan, there are
two linked patches of garbage
which are often referred to as a
plastic soup. It is roughly twice
the size of the continental US and
is a threat to marine mammals.
◊
It is estimated that this plastic sea
is the cause of death for over
100,000 marine mammals every
year.
Overfishing
◊ What is Overfishing?
◊ Negative Impacts on
Marine Mammals
What is Overfishing?
◊
Overfishing is the act of fishing a
body of water so extensively that
it depletes the supply of fish in an
area.
◊
It occurs when the quantity of fish
harvested exceeds the amount
that can be re-supplied by growth
and reproduction, which results in
a population collapse of the target
species.
Negative Impacts on Marine
Mammals
◊
When fishing, commercial fisheries
often compete for the resource of
fish with their natural predators.
This can make it more difficult for
a population of marine mammals
to obtain food.
◊
Overfishing can also cause an
imbalance in an aquatic
ecosystem by removing one of the
links in the food chain. This in turn
can result in the decline or
displacement of marine mammals
which depended on the harvested
fish as a food source.
Entanglement
◊ What is
Entanglement?
◊ Nets
◊ Debris
What is Entanglement?
◊
Entanglement is a large threat to
marine mammals. It occurs when
they are accidentally trapped in
fishing nets, fishing lines, six-pack
rings, or other snares.
◊
It is estimated that hundreds of
thousands of marine mammals are
entangled each year.
Nets
◊
Drift nets are one of the most
threatening types of nets used by
fisheries.
◊
They are essentially nets made of
thin strands of nylon that are left
to freely drift and catch everything
in their path.
◊
They can sometimes be miles long
and be left unattended for weeks.
◊
Drift nets typically catch a large
amount of bycatch, or the nontarget species that become
tangled in the nets, such as
whales, dolphins, and seals.
Nets
◊
Marine mammals that are trapped
in these and other nets will often
drown if they cannot escape.
◊
Those that do escape usually end
up with scars or missing fins as a
result of being cut by the thin
nylon strands of the nets.
Debris
◊
Debris, such as plastic rings and
fishing lines, mainly pose a threat
to pinnipeds, or walruses and
seals.
◊
These marine mammals often
become trapped with debris
around their necks or heads,
which can restrict breathing,
eating, and even swimming.
Debris can also inflict physical
wounds. At the very least, these
negative impacts will debilitate
their targets.
◊
Once snared, it is a very difficult,
if not impossible task for a marine
mammal to remove its bindings.
Other
◊ Collisions
◊ Climate Change
Collisions
◊
Ship traffic is another danger to
marine mammals.
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Those that are hit by a boat will
often die.
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However, marine mammals
sometimes do survive boat
collisions, but will usually end up
with disfiguring wounds and
scarring.
Collisions
◊
Ship strikes are not very
uncommon. Many marine
mammals have scar patterns that
indicate multiple boat collisions.
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Right Whales are highly vulnerable
to collisions, due to their slow
surface-foraging nature.
Climate Change
◊
Due to global warming, marine
mammals could lose valuable food
sources and habitats.
◊
Populations of fish, which are
preyed upon by marine mammals,
are predicted to move into deeper
and cooler water which is farther
away from shore. This change is
troubling to seals and other
pinnipeds that require land in
order to reproduce and sleep on.
◊
Migratory whales could also
suffer, as they are dependent on
finding certain resources at the
ends of their migratory routes.
Conclusion
◊
Overall, there are many threats
that oppose marine mammals,
such as the numerous types of
pollution, overfishing,
entanglement, ship collisions, and
climate change.
◊
However, these threats are not
without hope of being remedied,
as numerous laws, regulations,
and organizations, such as the
Marine Mammal Protection Act
and the creation of aquatic
reserves, are in place to ensure
the safety and stability of the
marine mammal populations.