Hello marine biology students.
This week we're going to talk about the impacts
that humans have had on the marine environment.
[Intro Music]
And so, we're going to talk about the impacts
that humans have had on habitats and also
endangered species and conservation efforts
this week.
As humans, one of the things we do is to modify
natural habitats.
This often results in their destruction.
And most habitat destruction occurs close
to shore as a direct result of human development.
Now, sometimes this is unplanned or sometimes
just poorly-planned development.
Destruction of marine habitats is more acute
in developing countries, but it is also common
in developed countries as well, where you
can clearly see this coastline is no longer
performing the natural functions it did on
the coast of Alabama before human development.
One example of a habitat that we often destroy
are coral reefs.
Approximately one-fourth of all coral reefs
have been lost or at risk.
One-third of reef building coral species now
face extinction and this can be from pollution,
either from sewage, agricultural runoff, or
sedimentation, also comes from rising temperatures,
from ocean acidification, by fishing with
explosives (which is more common than you
might guess), and from the collection of organisms
for the aquarium trade.
Here in these images we see an individual
who is harvesting coral using a crowbar.
Now, this could be as building materials or
it could be as souvenirs.
In the next image we see the results of coral
bleaching.
This bleaching is evidence that the coral
is stressed, either by temperatures or chemically.
The coral has decided to expel it zooxanthellae
and hopefully replace it with something that
will be better suited for the current environment.
Another way we destroy habitats is through
trawling.
Trawling nets are a major threat to subtidal
habitats.
Bottom trawling is when nets are dragged along
the bottom, causing resuspension of sediments
which can kill many suspension feeders as
well as deposit feeders, but not only that,
trawls can also break off attached organisms
and totally disturb the soft bottom community,
typically leading to destruction of that habitat.
There's a short video clip from the animated
movie Ponyo that can show you a bit of what
this trawling looks like.
It will be available after this video.
Pollution is another way that humans harm
habitats.
Pollution is defined as the human introduction
of a substance that reduces the quality of
the environment.
Most marine pollutants are actually the result
of land-based activities.
These sources of pollution include fertilizers,
sewage, oil, and persistent toxic substances.
So, with fertilizers, land-based fertilizers
wash into streams and rivers and are carried
into coastal waters.
This can increase the nutrients in the water,
known as eutrophication, and this eutrophication
in turn causes phytoplankton to bloom and
increases in the amount of bottom seaweeds.
Here we see muddy water running off a farm
field in Tennessee following a storm.
The fertilizers in that field can wash off
into these rivers and streams which make their
way to the oceans, and this would all be done
in an untreated manner.
As seaweeds take over at the bottom in certain
areas and the phytoplankton die off after
they bloom and drop to the bottom, the massive
amounts of organic matter causes an increase
in decomposition by bacteria.
In this decomposition, oxygen is consumed
and anoxic conditions develop affecting all
forms of life, often causing organisms not
to be able to survive in that area and the
motile ones end up leaving.
Phytoplankton blooms also can decrease the
amount of light available for other producers.
Domestic sewage 
comes from homes and city buildings as well
as stormwater runoff, and often this will
be treated in a wastewater plant of some sort,
but that will vary based on community and
based on economic status.
Industrial sewage comes from factories and
other manufacturing facilities and it may
contain a variety of substances.
Sewage can also contain disease-causing organisms
if it is untreated.
It may also contain heavy metals and other
toxic substances even if the sewage is treated.
One example of a biological molecule that
builds up, even in treated sewage, is that
of pseudo-hormones and these pseudo-hormones
can end up having drastic impacts on natural
communities and that's not a substance that's
removed from sewage with our current water
treatment methods.
Oil pollution is another thing that can affect
marine populations.
Organisms can accumulate 
components of oil, many of which are toxic.
These components can affect reproduction,
growth, development, behavior, and just survival
in general.
Often endothermic organisms 
may die if their feathers or fur become coated
with oil and that reduces their ability to
insulate themselves from the cold marine waters.
Organisms living in estuaries, seagrass meadows,
mangrove forests and corals are also at risk
if coated with oil.
Here in this image we see a sea turtle that's
covered with oil that hopefully will be cleaned
off by this individual helping after an oil
spill.
Now, it turns out that natural hydrocarbon
seeps actually are the source of the largest
amount of oil in the marine settings, but
there are various land-based pollution and
recreational boating which contributes a significant
amount.
The general transport of oil using tankers
and other things, and actually the smallest
contributor to oil pollution in the marine
environment is the actual exploration and
extraction of oil, but blowouts and oil spills
can have a significant impact on local communities
if and when they occur.
Persistent toxic substances are also a threat
to the marine system.
Pesticides can be an example.
Substances that are released in one setting
to control or kill organisms can have unintended
impacts 
in other areas.
Certain pesticides, such as DDT, can build
up in marine birds and decrease reproductive
success by making their eggshells very brittle.
The brown pelican had its numbers significantly
reduced because of DDT's use and now that
it's been banned, their numbers are coming
back.
Other examples of persistent toxic substances
include chlorinated hydrocarbons, polychlorinated
biphenyls, and heavy metals.
Chlorinated hydrocarbons dissolve in lipids
and so they can be carried in the fats and
lipids of organisms and are passed along the
food chain.
They can accumulate in the tissues of the
top predators of these ecosystems because
they are not biodegradable, and this is known
as biological magnification.
The levels of PCBs and heavy metals such as
mercury, lead, cadmium and copper in the oceans
continue to be a problem as well.
There's also a process known as global distillation,
in which the concentration of PCBs and heavy
metals are found primarily in the polar regions
where cold temperatures facilitate condensation
of these chemicals brought in by the winds.
So sometimes these populations that don't
have much direct human contact are still negatively
impacted by pollution generated by humans
hundreds even thousands of miles away.
Other pollutants include solid wastes, particularly
plastics.
Microplastics 
are of particular concern and they can come
from things such as toothpaste and pharmaceuticals,
but most importantly, recently discovered
degradation of macroplastics will result in
microplastics that impact communities.
Other examples of pollution include thermal
pollution or water that is used to cool certain
sections of power plants are then returned
back to the environment much hotter than they
were previously, and this can have dramatic
impact on the local communities and the general
temperature of that water basin.
Desalinization plants run through reverse-osmosis
to generate pure drinking water for humans,
but this results in highly concentrated salty
brine that is returned back to the marine
ecosystem, often to the detriment of the local
marine communities.
Radioactive wastes, whether from nuclear accidents
or wastes dumped at sea or even sunk in nuclear-powered
submarines and ships, can also affect marine
environments, harming the organisms.
So that takes us to the end of our discussion
of the impacts that humans have had on marine
environments.
Before our next video I would like you to
think about “What organism would you really
be sad if it no longer existed?”
We'll talk about that in the next video.
See you then.
