Phytoplankton and Algal Blooms

Algae Diversity

• Algae are organisms that are neither plants nor animals, belonging to the Kingdom Protista or Prototista, with varying forms, sizes, and colors.
• They can be found in both terrestrial and aquatic habitats, including freshwater and marine environments.
• Algae are a major source of oxygen on earth.

Habitat

• Small free-floating algae are known as phytoplanktons.
• Algae can be found in semi-permanent pools, ponds, lakes, streams, and along ocean shorelines.
• In terrestrial habitats, they can be found on rocks, wood surfaces, and in symbiotic association with fungal species (Lichens).

Divisions of Algae

• Algae are grouped into three divisions based on their pigmentation:
  • Rhodophyta (Red Algae)
  • Phaeophyta (Brown Algae)
  • Chlorophyta (Green Algae)

Characteristics of Algae Divisions

• Chlorophyta (Green Algae):
  • Unicellular, colonial, and multicellular forms.
  • Found in freshwater and some marine environments.
  • Reproduce asexually and sexually (biflagellated gametes).
• Rhodophyta (Red Algae):
  • Multicellular, mostly marine.
  • Cells are non-flagellated.
  • Alternation of generation is common.
  • Photosynthetic pigment (Chlorophyll) is masked by red pigments.
• Phaeophyta (Brown Algae):
  • Multicellular, mostly marine.
  • Found in intertidal zones.
  • Chlorophyll is masked by brown pigments.
  • Alternation of generation is common.

Algal Structure

• Algae exist in various forms:
  • Non-motile unicellular (sedentary)
  • Unicellular motile (single-celled, oval/pear-shaped with two flagella)
  • Motile coenobial (colony of flagellated cells)
  • Non-motile coenobial (colony of cells without flagella)
  • Filamentous (chains of cells joined into threads)
  • Thalloid (compact, multicellular body with flattened photosynthetic parts and holdfast for anchorage)
  • Special forms (complex thallus structure with annual and perennial parts and meristematic region)

Life-Cycle of Algae

• Algae reproduce via three different modes:
  • Vegetatively (e.g., fragmentation, fission)
  • Asexually (e.g., by spores)
  • Sexually (e.g., by gametes)
• Green algae reproduce vegetatively, asexually, and sexually.
• Sexual reproduction involves biflagellated gametes.

Mode of Nutrition

• Algae are autotrophic organisms, synthesizing their own food from inorganic substances using light or chemical energy.
• Algae are photoautotrophs, using light as the source of energy to prepare their food.

Economic Importance of Algae

• Algae are a link in the food chain, providing energy for aquatic organisms.
• Algae are useful in fish culture, serving as a source of feed for fish.
• Algae can be harmful in the form of algal blooms, which can produce toxins and have negative impacts on humans, marine and freshwater environments, and coastal economies.
• Algae are used in sewage treatment plants to provide oxygen from photosynthesis.
• Algae are used in the petroleum and gas industry, with some varieties serving as a source of bio-fuel.
• Algae contribute to limestone formation, accumulating calcium carbonate in their cell walls.
• Algae are used as food, rich in vitamins A and E, and containing vitamins C and D.
• Algae are used as fodder for livestock.
• Algae are used as fertilizer, with some species having nitrogen-fixing capabilities.
• Algae have medicinal uses, such as treating goiter and other glandular problems.