Biology Reference
In-Depth Information
cures for various diseases. This chapter will discuss in brief, potentials of
bioprospecting of microalgae and other marine organisms as sources of
valuable nutraceuticals and other compounds.
MICROALGAE
Microalgae are single celled microscopic plants, which are responsible for
the primary productivity in the open oceans. The sea, composing about
three-fourth of the surface of the earth, absorbs signifi cant amounts of solar
radiation, which is utilized by autotrophic microalgae for photosynthesis,
providing food for diverse oceanic creatures including sponges, crustaceans
and other animals (Matsunaga et al., 2005; Irigoien et al., 2004; Falkowski,
2002). It has been estimated that the world's oceans absorb nearly half
of the carbon dioxide that is released into the atmosphere from burning
fossil fuels. When these organisms die, they sink down to the seabed, and
take the carbon with them. Concentrations of these algae usually range
between 10
5
and 10
6
cells/ml of open ocean waters. Microalgal cells are
more in inshore ocean areas, which are nutritionally richer than open
waters. Marine bays and inlets receiving sewage or industrial waste can
have very high phytoplankton and bacterial population, which, in turn,
supports higher densities of chemotrophic bacteria and aquatic animals
such as fi sh and shellfi sh (Madigan and Martinko, 2005; Prabhudas et al.,
2009).
Major Species
There are more than 40,000 different species of microalgae, which are divided
into several phylae Some of the major phylae include Dinofl agellates,
Cryptophytes, Euglenophyta, Haptophyta, Heterokontophyta,
among others (Nybakken, 1997; Irigoien, et al., 2004). Dinofl agellates
(Dinophyceae) form a signifi cant part of primary planktonic production
in both oceans and lakes. These microalgae could be autotrophs,
mixotrophs, osmotrophs, phagotrophs, or parasites and are usually
unicellular, fl agellated, often photosynthetic protests. Approximately 130
genera of dinofl agellates consisting of about 2000 living and 2000 fossil
species have been described, most of them belonging to marine habitat.
Extreme abundance of dinofl agellates (2 to 8 x 10
6
/l water) results in “red
tide” leading to signifi cant toxin formation with its devastating effect on
the mortality of fi sh and invertebrates. Cryptophytes, a major species of
phytoplankton, are unicellular fl agellates with 12 to 23 genera comprised
of 200 species. They are distributed both in freshwater and marine
environments. A few species are colorless heterotrophs, but most possess
various colored plastids with chlorohylls, carotenoids and phycobiliprotein
and alloxanthin, a xanthophyll that is unique to these algae. The phylum
