D. salina under ideal conditions can yield 400 mg β-carotene/m 2 of
cultivation area. Growth of the microalga is comparable with that of Spirulina
and requires bicarbonate as a source of carbon and other nutrients such as
nitrate, sulfate and phosphate. Initial growth phase requires 12 to 14 d in
nitrate rich medium, and 25-30k lux light intensity for vegetative growth.
For optimal carotene synthesis the light should be reduced to 15 k lux,
besides, nitrate depletion and maintenance of the initial salinity. Harvesting
is done by fl occulation followed by fi ltration; the biomass can be directly
utilized for food formulation. Most of the pharmaceutical formulations
are made by extracting the alga with olive or soybean oil (Dufosse et al.,
2005). Although not from marine habitat, Haematococcus pluvialis is a green
alga that can grow both under autotrophic and heterotrophic conditions.
It is known for its ability to synthesize astaxanthin, up to 2.0% on dry
weight basis and hence, is one of the potential organisms for commercial
production of astaxanthin. Astaxanthin from H. pluvialis is obtained by
crushing the algae and supercritical carbon dioxide extraction. Several
European countries have approved its marketing as a dietary supplement
for human consumption . The maximum total recovery of astaxanthin
exceeded 97%. Another source of the pigments is Phaffi a rhodoxyma
( Xanthophyllomyces dendrorhous), which requires a large amount of feed
for suffi cient pigmentation leading to higher ash contents ( Dufosse et
al., 2005). Some current commercial microalgal products include a U.S.
FDA (Food and Drug Administration) approved dietary supplement
containing astaxanthin, called Zanthin , extracted from the microalga, H.
pluvialis. Martek DHA TM is a commercial oil product from microalga that
contains signifi cant amount of DHA. A carbohydrate extract from the
green microalga, Chlorella pyrenoidosa is claimed to boost response of the
immune system to the fl ue vaccine (Ohr, 2005).
CORAL REEF AND CORALS
Coral reefs are massive deposits of calcium carbonate in the oceans, which
harbor a rich and diverse ecosystem of animals. The reefs are produced
primarily by corals with minor additions from calciferous algae and
other organisms that secrete calcium carbonate. The coral carbonate
is composed of two distinct mineral forms—calcite and aragonite, the
latter containing signifi cant amounts of magnesium. The reefs are unique
among marine associations in that they are built up entirely by biological
activity. Some major physical factors that infl uence coral reef development
are temperature, depth, light, salinity, sedimentation and emergence into
air. Coral reefs are also found in the clean coastal waters of the tropics and
subtropics, which give optimal conditions such as moderate temperature
and good sunlight favoring growth of reef forming organisms. It has been