The Biology of Microalgae - Biotechnological Applications of Microalgae - page 13

and lakes), epipelic algae (attached to sand and mud), endophytes (living inside the
tissue of other plants), epizoic algae (on shell of snails), and endozoic forms (inside
sponges). Considerable research has been carried out on various water bodies with
reference to hydrological conditions and the periodicity, abundance, and seasonal
variation of algae. Members of the green algae dominate in summer and become less
dominant in winter. High temperatures and organic matter support the occurrence of
euglenoids, while high phosphates and low organic matter facilitate the abundance of
diatoms. An increase in pH, organic matter, and nutrients sometimes leads to the for-
mation of blooms. Microcystis aeruginosa forms blooms in several highly alkaline
and nutrient-rich ponds. Diurnal variations of microalgae have also been noticed.
Lakes and reservoirs have been found to show highest algae occurrence during sum-
mer and winter. The shallow waters near the shores contain epiphytic filamentous
green algae, and the deeper waters support only deep euplanktonic organisms such
as desmids and diatoms. Blue-green algae occur in low dissolved oxygen, abundant
organic matter, and high temperature, and become possible indicators of pollution,
while green algae occur with exactly the opposite conditions. Diatoms show seasonal
periodicity, always reaching a maximum during summer, and correlate with the sili-
cates. Desmids are very sensitive to pollution. Hydrobiological studies on polluted
waters have led to spotting microalgal indicators by calculating the species diversity
index. Studies on the relationship of microalgae and their nutrient requirements in
some lakes have in certain cases led to developing approaches for conservation and
prevention from pollution.
2.4.2 M arine
Marine ecosystems that form the marine environment are the largest habitats on
Earth for a diversified group of organisms. The biotic community of marine envi-
ronments is dominated by microalgae. They are among the largest primary pro-
ducers of biomass in the marine environment and are common inhabitants of the
tidal and intertidal areas of the marine ecosystem. These algae exhibit a character-
istic geographical distribution pattern under the influence of several environmen-
tal factors (Vijayaraghavan and Kaur, 1997). Nevertheless, the coastal ecosystem
in the marine environment is very complex where all organisms exist in mutual
dependency. Although considerable attention has been paid to distribution, abun-
dance, growth, culture, biochemical constituents, by-products, and bioactivity of
marine algae in different parts of the world (Faulkner, 1984), information is avail-
able on the microbes, planktonic and faunal associates of marine algae, and the
impact of various environmental factors on their distribution. The algal biotope
with its morphological diversity is considered important in providing food, living
space, and refuge, and offers a variety of potential habitats for the faunal spe-
cies, including planktonic forms. A detailed investigation is therefore necessary
to understand the actual nature of the association between algae and other forms
to appreciate the potential importance of this interaction in the marine ecosystem.
Steele (1988) described the “heuristic projection,” which illustrates the scales of
importance in monitoring pelagic components of the ecological unit. The large
marine ecosystem (LME) approach defines a spatial domain based on ecological