This term refers to the collection of minute or microscopic organisms that inhabit the surface layer of a body of water.

During the sexual reproduction of algae, eggs are formed within the relatively unmodified vegetative cells called oogonia that function as female structures and the sperms are produced within special male reproductive structures called antheridia, where the gametes are fused to produce a diploid zygote.

The molecule laminarin is a storage glucan found in brown algae. It is used as a carbohydrate food reserve in the same way that chrysolaminarin is used by phytoplankton. It is created by photosynthesis and is made up of Beta-1,3-(D)-glucan with Beta- 1,6-glucan linkage. This structure is quite similar to the structure of chrysolaminarin.

It is a type of blue green algae, which is rich in protein, vitamins, minerals, carotenoids, and antioxidants that can help to protect the cells from damage. It is made primarily from two species of cyanobacteria; Arthrospira platensis and Arthrospira maxima.

It results from eating marine fishes that have consumed the dinoflagellate gambierdiscus toxicus. The algal toxin called ciguatoxin accumulates in the flesh of fish. This is one of the most powerful toxins known and remains in the flesh even after it has been cooked.

Insecto is a diatomaceous earth product isolated from diatoms and is used to control the insects, which have their soft body parts exposed but covered by a waxy film to prevent dehydration. When they came in contact with diatoms in Insecto, the silica frustule break the waxy film on the insects causing them to dehydrate and die.

The colour of Phaeophyta reflects the presence of the brown pigment fucoxanthin. It is a type of carotenoid found naturally in edible brown seaweed, which are used widely in Asian cuisine and also available as a nutritional supplement in capsule form. It is explored for weight loss, and to decrease insulin and blood glucose levels, etc. It may have anti-tumour effects also.

Chlorella is a genus of single cell green algae, which belongs to the phylum Chlorophyta. Our body is contaminated with heavy metals from dental fillings, after receiving a vaccine by the use of certain types of cookware or eaten fish.

Lichens are the association between specific ascomycetes (the fungus) and certain genera of either green algae or cyanobacteria. In lichen, the fungal partner is termed the mycobiont and the algal or cyanobacterial partner is called the phycobiont. It is a type of mutualistic relationship.

Many marine invertebrates  (like sponges, jelly fish, sea anemones, corals, and ciliates) harbor endosymbiotic spherical algal cells called zooxanthelle within their tissues. The reef building corals satisfy most of their energy requirements using their zooxanthelle.

Paramylon is the main storage product of euglenoids. Paramylon is a carbohydrate similar to starch. The chloroplasts found in Euglena contain chlorophyll, which aids in the synthesis of carbohydrates to be stored as starch granules and paramylon. Paramylon is made in the pyrenoids of Euglena. It is stored in rod-like bodies through out the cytoplasm, called paramylon bodies and are often visible as colourless or white particles in light microscopy.

A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed of silica made from silicic acid, and is coated with a layer of organic substance. This layer is actually composed of several types of polysaccharides. The frustule is usually composed of two overlapping sections known as thecae. The join between two thecae is supported by bands of silica that hold them together. This overlapping allows for some internal expansion room and is essential during the reproduction process. The frustule also contains many pores and slits that provide the diatoms access to the external environment for processes such as waste removal and mucilage secretion.

Chlamydomonas is a single-celled alga about 10 micrometers in diameter that swims with two flagella. Flagella of Chlamydomonas are typical of eukaryotic cilia and flagella in that they are composed of micro tubules arranged in the well-documented 9 + 2 structure. They have two flagella of equal length at the anterior end by which they move rapidly in water.

Gonyaulax, a species of Pyrrhophyta or dinoflagellates, can produce light and are responsible for much of the luminescence or phosphorescence seen in ocean waters at night when the water is disturbed. In the phosphorescent bays, high densities of a single species occur. Red tides are blooms, essentially monocultures of a given dinoflagellate species, which may or may not be luminous.

The cell walls of most red algae include a rigid inner part composed of microfibrils and a mucilaginous matrix. The matrix is composed of sulphated polymer of galactose called agar, funori, porphysan and carrageenan. These four polymers give the red algae a flexible slippery texture. Agar is a component of the cell walls of several species of red algae. Agar is a mixture of two components; linear polysaccharide agarose and a heterogenous mixture of smaller molecules called agaropectin.