Download Biology of Seaweeds

Biology of Seaweeds
What are algae?
Algae are a diverse group of mostly photosynthetic organisms that share a
few characteristics, but which lack the structural complexity associated with
higher plants…
Phycology - The study of algae (also referred by some as algology)
Algal classification:
Algae are subdivided into a number of distinct evolutionary lines. The
major groupings of algae are in form of divisions, a term parallel to
phyla in case of animals…
Algal divisions are based on the following features:
1. Light-harvesting pigments for photosynthesis
2. Polysaccharide reserve
3. Cellular organization
4. Morphology
5. Ecology
Review of Photosynthesis
What is photosynthesis?
The ability to use light to convert inorganic molecules into organic
molecules.
H2O + CO2 ==== light == sugar + O2
Sugar can then be used to make other required molecules, or it can be
broken down as a source of energy… O2 is simply a biproduct of photosynthesis… almost all the O2 in the earth’s atmosphere comes from
photosynthesis.
Photosyntesis – Pigments
The first step of photosynthesis involves using pigments to capture light.
The range of visible light used for
photosynthesis is from about
400 to 750 nanometer wavelengths
of electromagnetic radiation…
this range is referred to as PAR –
Photosynthetically Active Radiation.
Although chlorophyll is the primary
pigment used by plants (it’s what makes
plants green…), other pigments such as
carotenoids and phycocyanin are also
used… why do you think this is? Why
may this be of particular interest in
algal systems?
Photosyntesis – Effects of varying light levels
In marine systems, light can be a limiting factor to photosynthesis… The success of
Different algae at different depths/conditions may be a function of their ability to
Efficiently capture light and photosynthesize…
P: photosynthesis
Pmax: maximum photosynthesis
Pg : gross photosynthesis
Pn : net photosynthesis
R : respiration
IK : saturating irradiance
Biology of Seaweeds – Algal Divisions
Will cover on future lectures (on phytoplanktons):
Bacillariophyta (=Diatomophyceae) – Diatoms
Photosynthetic pigments: Chlorophyll a, c ; Carotenioids
Major storage products: Chrysolaminarin, oil
Major cell wall component: Silica, Pectin
Pyrophyta (=Dinophyta) - Dinoflagellates
Photosynthetic pigments: Chlorophyll a, c ; Carotenioids
Major storage products: Starch, oil
Major cell wall component: Cellulose
•Note that some researchers will classify diatoms into their own division, whereas
others will put diatoms into the class bacillariophyceae, under the division chrysophyta,
which would include a number of different algae, including all the different brown algae
off our coast…
Biology of Seaweeds – Brown Algae
Division Phaeophyta (=Fucophyta) - Brown algae
Photosynthetic pigments: Chlorophyll a, c ; Carotenioids (including
fucoxanthin which give the brown coloration)
Major storage products: Laminarin, oil
Major cell wall component: Cellulose
Brown algae are extremely common off the coast of California; here are some examples:
Biology of Seaweeds – Brown Algae
Brown algae are often the dominant primary producers in temperate and polar
regions… The brown algae often do best in these cold, nutrient-rich waters, and
some kelp have the capacity to grow as much as two to three feet per day!!
The complete algal body is known as the thallus; make sure you can identify all
the individual body parts and know what each of their functions are…
Biology of Seaweeds – Brown Algae
One more picture of the stype, pneumatocysts, and blades.
Biology of Seaweeds – Brown Algae
Distribution of kelp is very dependent on water temperature and is therefore a
function of both latitude and oceanic circulation…
In many of these areas, kelp (and other brown, red, and green algae) are harvested
for the resources they provide… more on this later…
Biology of Seaweeds – Red Algae
Division Rhodophyta – Red algae
Photosynthetic pigments: Chlorophyll a; Phycobilins [including
phycoerythrin (red in color) and phycocyanin
(blue in color)]
Major storage products: Starch
Major cell wall component: Cellulose, Agar, Carrageenan
and in case of coralline algae, Carbonates
Some examples of red algae from the California coast:
Biology of Seaweeds – Red Algae
Many red algae show calcification throughout their thallus (some in fact grow as an
encrusting layer over rocks), whereas others do not…
What do you think may be the reason for the calcification in some of these species?
What may be the advantages and/or disadvantages of having a calcified body?
Structural? …. Protection from intense sunlight? …. Protection from grazing?
Biology of Seaweeds – Green Algae
Division Chlorophyta – Green algae
Photosynthetic pigments: Chlorophyll a, b; Carotenioids
Major storage products: starch
Major cell wall component: Cellulose
but also carbonates in some coralline forms…
The similarity of photosynthetic pigments, storage products, and cell wall
components of green algae with higher plants suggest that higher land plants
probably evolved from a green algal type ancestor…
Some examples of typical green algae from the California coast:
Biology of Seaweeds – Economic Implications
Seaweeds have a wide range of potential uses:
Food – The most obvious use of seaweeds is in form of various foods prepared
directly or indirectly from algae or algal products…
Phycocolloids – used in food processing, they have the ability to form viscous
suspensions and gels…
Algin and carrageenen for example are often used as a stabilizers and
emulsifiers in dairy products, the baking industry, and for making
of shampoos and toothpastes, etc.
Agar, another phycocolloid, is used in canning of hams, fish, meats, etc.,
because of its ability to form jellies… this helps with protecting
the canned material… Other uses of agar include production of
various forms of pharmaceuticals, and even research media…
Seaweeds may also be used as a source of fertilizer, food additives in animal
feeds, etc., etc., etc.,… Big industry!!!!!
Biology of Seaweeds – One more type of algae to consider!!
Division Cyanophyta – Blue green algae (=cyanobacteria)
Photosynthetic pigments: Chlorophyll a; Phycobilins
Major storage products: Cyanophycean starch; Cyanophycin (protein)
Major cell wall component: Chains of amino sugars and amino acids
These bacteria (yes they are prokaryotes!) are some of the most primitive
plant-like organisms on earth… They are thought to have been among the
first photosynthetic organisms on earth, and as such played an important
role not only in the evolution of algae and plants, but also in the process
of the initial accumulation of oxygen in our atmosphere…
Many species are very eurythermal and euryhaline …
Make up much of the slime on tropical, submerged rocks…
Biology of Seaweeds – The Sea Grasses
Tracheophyta – Vascular plants
(The classification of tracheophyts will vary depending on whom you talk
to… many researchers cannot even agree on if algae and vascular plants
should be in the same kingdom or not… same issues need to be considered
when studying cyanobacteria)
Photosynthetic pigments: Chlorophyll a, b ; Carotenioids [including
Carotene (orange in color), and Xanthophyll (yellow
in color)]
Major storage products: Starch
Major cell wall component: Cellulose
Biology of Seaweeds – The Sea Grasses
As vascular plants, sea grasses have flow tubes called xylem and phloem.
Xylem – tube like hollow vessels that transport water and minerals in
vascular plants.
Phloem – a tissue that conducts food material (i.e. photosynthates) in vascular
plants…
The sea grasses do not look like your
typical “land plants”… what
adaptations do you think they have
for life in their shallow subtidal /
intertidal marine habitats?
Biology of Seaweeds – The Kelp Forest
More on this, next lecture…