Hi marine biology students.
In this last video of the week we're gonna
talk about plants that live in and near the
oceans.
[Intro Music]
So, are their true plants that live in the
oceans?
The answer is yes.
Flowering plants or angiosperms 
are true plants, having true leaves, stems,
roots, and conducting tissues.
There are over 250,000 species worldwide,
but it turns out that only a few are truly
marine.
All land plants with fruits and flowers fall
into this category, and so that's where most
of our recognized species come from.
In order for a plant to live in the oceans,
it must be adapted to live in seawater.
So one major category of marine plants are
the sea grasses.
There are around 60 species of seagrasses
and they live mostly in tropical waters, although
some can also live in temperate climates.
These are flowering plants, but their flowers
are usually small and inconspicuous in most
species of sea grasses.
These flowers do generate pollen, which contain
the sperm or the male gametes for the plants,
and this pollen will be carried by water currents.
After fertilization, tiny seeds are formed
and these seeds can also be carried by water
currents or also in the feces of animals that
consume the sea grasses like sea turtles.
Sea grasses form highly productive seagrass
meadows or beds
that provide a habitat for many organisms
that hide among the leaves.
One particular type of seagrass, the eelgrass
from the genus Zoestra, is the most widely
distributed of the sea grasses, very common
in shallow temperate waters around the world.
We will be talking about seagrass meadows
in greater depth in future chapters during
the semester.
Here we see what a few of these different
types of sea grasses look like.
They show remarkable similarity, even though
they are distinct species, even from different
genera.
Our next category of marine plants are salt
marsh plants.
These are plants bordering shallow bays and
estuaries at river mouths.
The most common of these are the cordgrass
Spartina.
This is the dominant salt marsh plant, in
many salt marshes.
These salt marsh plants are exposed to seawater
at high tide and so they need to have mechanisms
to rid themselves of excess salt.
Some do that through the use of salt glands.
These salt marsh plants provide an important
habitat
to many marine organisms, including juvenile
invertebrates and fishes.
These estuary environments are very important,
serving as nurseries of the oceans.
As these plants photosynthesize and grow and
ultimately break down, they form detritus
and this detritus ends up being a food source,
a source of nutrients for countless marine
organisms.
There are other halophytes or salt tolerant
plants
that grow in areas of higher elevation than
the cordgrass.
They cannot tolerate being totally submerged
in seawater like the cordgrass can, but they
are an important part of these salt marsh
communities.
We'll look at estuaries in salt marshes more
again later this semester.
Here we can see an image of what these salt
marsh estuaries look like.
The last category of marine plant that I want
to discuss are the mangroves.
Mangroves are any woody plants that are able
to live being submerged or partially submerged
in seawater.
There are about 80 species of mangroves and
they live only in tropical and subtropical
areas of the world.
One of the reasons for their limited distribution
is that they cannot withstand freezing temperatures.
Even though they can't tolerate freezing,
they can tolerate at least partial saltwater
submergence.
Many mangroves have prop roots that are exposed
during low tide and submerged during high
tide.
Here we can see some mangroves and their prop
roots and the fluctuation of the tide level.
Often the seeds of mangroves can germinate
while still being attached to the parent plant,
so the seed actually starts sprouting while
attached to the parent and it develops into
a seedling before it even falls into the water.
Once they fall, they can either be embedded
into the soft sediment or they can be carried
away from the parent before they end up getting
stuck into sediment and growing themselves.
So the seedlings 
drop into the soft sediments or are carried
by currents to a new location.
And here in this picture we can see a fruit
of a mangrove tree that has already started
to sprout its root and when it separates from
the parent plant it can embed into the soft
sediment nearby or again be carried just a
short ways down.
Mangrove forests or mangals as they are called,
are highly productive communities that provide
habitats to many marine and land organisms.
They are the tropical equivalent of salt marshes.
Here we see a distribution of mangroves and
salt marshes around the world.
In some areas in which both salt marshes and
mangroves can be found, usually though it
seems like the coastline will have one or
the other, either a mangal or a salt marsh.
This table, Table 6.1 is one that compares
the three major types of marine algae or seaweeds
with flowering plants that live in the oceans
as well.
Again, you can see their characteristics,
their photosynthetic pigments, the components
of their cell walls, and also the role they
play in their ecosystems.
So that takes us to the end of our discussion
on marine plants.
Next week we're going to be talking about
animal life in the oceans and so before next
week I'd like you to think about “What animals
do you think are the most common in the oceans?”
Alright, I'll see you next week.
Bye!
