Algae are abundant and ancient
organisms that can be found in
virtually every ecosystem in the
biosphere. They may range from
tiny single-celled species one
Algae in many habitats often go unnoticed unless environmental
conditions become favorable for the development of conspicuous and
sometimes massive proliferations of their numbers—a situation often
brought about by human activity.
With the advent of biotechnology,
algae are poised to play greater,
albeit often subtle, roles in the
day-to-day lives of human beings.
The following is a brief description
of algal habitats and activities that
demonstrates algae occur in both
expected and highly surprising
If we dive in a ocean, there are "trees" of similar height that are less widely
appreciated because we by chance spend time in the water. Brown
undulating forests of 50-meter-long giant kelps, as tall and crowded as their terrestrial counterparts,
Like trees, kelps use photosynthesis to
convert the energy of sunlight into chemical energy, but the green of their chlorophyll is masked by large amounts of brown pigments. These accessory pigments aid in the
1. Brown seaweeds : Brown seaweeds are not limited to temperate (cold)
waters, but they are also found beneath polar ice sheets.
These organisms live at depths greater than 250 meters, where the light
The accessory pigments of
these algae whose role is the
same as that for those found
in the kelps
—
are essential for
the survival of photosynthetic
organisms in such
2. Zooxanthellae:
Tropical fringes are typically populated with a breathtakingly diverse array of submersed reef-forming corals, whose very existence and form are dependent upon intracellular
tenants-microscopic golden algal cells known as
zooxanthellae that generate food and oxygen in exchange for metabolic by-products (carbon
dioxide and ammonia) released by the coral cells. Zooxanthellae allow corals to thrive in
Zooxanthellae are the algae cells that
are hosted by a coral and they
provide the coral with energy; this
relationship is essential for coral
survival as without the zooxanthellae
the coral will not only lose its
3. Stromatolites:
In some seashore regions, calcium
carbonate-depositing, sediment-trapping, cyanobacteria have built layered
hummocks up to two meters high. These hummocks represent modern versions of more widespread fossil formations known as stromatolites, which are commonly
Phytoplanktons: Phytoplankton, also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll and require sunlight in
order to live and grow. Most
Furthermore, the surrounding ocean
waters-occupying approximately 70% of the Earth's surface-teem with some 5000 species of tiny floating or swimming. They are variously coloured. Populations of
marine phytoplankton can become so large that they are detectable by satellite remote sensing technology. Such blooms are in fact one of the more dramatic vegetational
Phytoplankton also require
inorganic nutrients such as nitrates,
phosphates, and sulfur which they
convert into proteins, fats, and
carbohydrates.
The two main classes of
Phytoplanktons come in many
II. The Algae of Freshwaters
Freshwater lakes, ponds, and streams contain similar botanical gardens of planktonic microalgae and attached forms (periphyton), which are often
themselves decorated with epiphytes. Freshwater algae display a wide
As in the oceans, it is not
uncommon to find that certain
photosynthetic freshwater
algae colonize the cells and
tissues of protozoa or
coelenterates like the familiar
Hydra
containing
endosym-biotic green
algae known
as
Cyanobacteria living within the
tissues of water ferns can be a
major contributor to the
nitrogen economy of rice
cultivation in paddies and thus
influence the nutrition of
Some examples of
freshwater algae are
Zygnema, Spirogyra,
Oedogonium, Cladophora,
Nostoc, Oscillatoria,
Algal Blooms:
Conspicuous blooms of microscopic algae occur in marine and freshwaters, often in
response to pollution with nutrients such as nitrogen and/or phosphate. Nutrient
Epiphytic Algae
Species of
Aphanochaete
Endophytic Algae
Endophytic algae are those which are found in another plant, not growing parasitically rather they are symbiotic. For example, Anabaena species are
found in Azolla (a water fern). Nostoc
species are found in the roots of
III. Terrestrial Algae
A considerable number of algae have adapted to life on land, such as those occurring in the snows of mountain ranges, in "cryptobiotic crusts"
typical of desert and grassland soils, or embedded within surfaces of
Several species of terrestrial algae, together with fungi, form the
distinctive life-forms known as lichens. Lichens are ecologically
important because of their role as pioneers in early stages of
succession, where they help to convert rock into soil, slowly
Lichens
growing
on a
The examples of
terrestrial algae are
Fritschiella, Chlorella,
Vaucheria, Euglena,
Oscillatoria, Phormidium
Cryophilic algae:
(cryophilic =
cold-loving)
Chlamydomonas nivalis
, a
species of green algae
containing a secondary
red carotenoid
This found on ice and snow
imparting red colour to the
snow. It is also called
Water elo s ow , red
s ow , or
blood s ow ,
because of reddish or pink in
color, with the slight scent of a
fresh watermelon.
Parasitic algae:
Some algae are parasitic like
Cephaleuros. Its common name is red
rust. Specimens can reach around 10 mm in size. Dichotomous branches are formed. The alga is parasitic on some important economic plants of the
Extremophiles:
Organisms that occupy extreme environments are called as
Extremophiles.
Algae in Hot Environments:
A number of species of cyanobacteria can tolerate temperature as high as 88°C in
At the center of this spring in Yellowstone National Park, water temperatures reach near 88°C too hot to support most life-but along the edges of
Algae are also found in
Antarctica. Presently there
are over 300 algal taxa
identified on Antarctica,
with blue-green algae,
diatoms and green algae
This is a patch of green snow, colored from the presence of
