The Reproduction, Microscopy, & Classification Of Algae Types

If you have ever had a pond in your backyard or taken a high school biology class, you will be familiar with the term algae. You will probably also, automatically conjure images of a green substance on the surface of still or stagnant water.

The Reproduction, Microscopy, & Classification Of Algae Types

However, algae is a much more varied and diverse organism than that with a wide range of species and various ways of reproducing. This article will cover the classification of algae with examples, how algae can reproduce, and the microscopy of algae.

What Is Algae?

Algae are defined as photosynthetic organisms, a singular organism is known as an alga.  The organisms that make-up algae have a huge range of sizes depending on the species, from large, complex species, to intricate micro-organisms.

They can be microscopic, single-celled micro-algae, such as chlorella, and they can be as large as kelp that can commonly reach lengths of 200 feet. 

Algae can be found in both marine and freshwater environments. The species present in each environment develop and adapt to their surroundings in order to survive effectively.  

The photosynthetic pigment that is present within the algae organisms differs from the pigment that is present in plants in both complexity and variety.

They also vary on a cellular level, with algae organisms lacking elements such as xylem, phloem, and stomata that are present in land plants. They also lack physical attributes such as roots and leaves that are characteristic of vascular plants.

Algae play a vital role in the protection and maintenance of the ecosystems they inhabit, from oxygenating the bodies of water they inhabit to providing a valuable food source for many aquatic species.

Outside of the benefits provided to the habitats of algae, they have been used as a source of crude oil, as well as in the pharmaceutical industry, helping to further advance the health and survival of mankind. 


Algae organisms can reproduce by both asexual and sexual methods. They also have various ways of performing both sexual and asexual reproduction. 

Asexual Reproduction

The process of asexual reproduction varies dependent on the type and size of the alga organism.  In minor species of algae, asexual reproduction occurs through ordinary cell division, also called fragmentation.

The union of cells and the combination of different genetic materials is absent in this process.  

In larger or superior algae species, asexual reproduction occurs through the formation of spores. Depending on the specific species of algae, the spores can be produced in either normal or specialized cells, and they may be motile or non-motile. 

Sexual Reproduction

The process of sexual reproduction in algae usually features meiosis, a form of cell splitting, using the genetic material of two different parent cells.

Sexual reproduction in algae organisms is strongly influenced and regulated by environmental factors such as natural events and water quality. 

Within the sexual reproduction process in algae, there are commonly two distinct phases. The first stage involves one set of chromosomes, referred to as haploid.

The second phase involves two sets of chromosomes and is referred to as diploid. 


There are different stages in the process of identifying algae species. Below we will look at each of the stages, including the microscopy of algae types.  


The two main collection methods used for micro and macro-algae are either by hand or using a knife. A pocket microscope is commonly used to identify the reproductive cells which can be important for certain categories of algae.

An example of this method is the collection of phytoplankton which is done using a tight mesh net. The collected sample is allowed to settle overnight which causes the algae to concentrate at the bottom of the water. 

There are occasions when a squeezing method is used as a means of increasing the biomass of the sample, this is often used in the collection of Sphagnum.

For samples that are difficult to obtain, such as when the algae organisms are present in the soil, it is important to undertake a culturing process before a microscopic examination is possible. 

If you are collecting samples of algae for scientific purposes, it is important that certain details are recorded before the examination takes place.

The name of the collector, the date of collection, locale, the texture of water, and whether the algae was free-floating or attached should be recorded. 


The examination process for algae is similar to that of most microscopic organisms.  

After placing algae onto a microscopic slide, add a drop of water or specimen. Carefully cover the slide using a coverslip and view it through the microscope, a microscopic range of between 40X and 100X magnification should be used.

It is important to remember that the specimen should contain a very small quantity to avoid the issue of clumping. 

It is also possible to use the hanging drop method to examine the specimen. In this method, the sample is placed on a coverslip and examination takes place using liquid paraffin or paraffin wax.

The hanging drop method is useful in examining the motility of a sample. 


The type of microscope used in the examination of algae organisms or samples is hugely important in ensuring that you are able to view the organisms properly. 

If you are using a compound microscope, it is necessary to utilize a higher magnification power, greater than 100X to properly facilitate the observation of specific details within the organism. 

Drawings and photographs play a vital role in the proper identification of algae species.  A camera attachment on the microscope can be used for these purposes.

A scanning microscope or transmission electron microscope is rarely used in the examination and identification of algae; they are primarily reserved for a select few, small algae.

Algae Classification

Algae Classification

The classification of protists or single-celled organisms is a highly debated topic and there is no current, established standard for classifying them. However, through the use of taxonomic variations, it is possible to group algae into six different types.


The algae within this classification are usually single-celled, or unicellular naked motile organisms which commonly are found in fresh-water habitats. Some species form colonies with multiple branches.

The thallus consists of a definite nucleus and the striking grass-green color is a result of the presence of chlorophyll localized within chromatophores.

They are also photosynthetic, and some can be Heterotrophic, meaning they get their nutritional requirements from complex organic substances. 

In Euglenophyta algae, chlorophyll is stored outside of the chloroplasts. There are over 1000  species of algae that fall into this classification.

Example: Eutreptiella

When viewed through the microscope, this algae species appears with either two or four flagella featuring wide-ranging stripes. The chloroplasts blister from two paramylon hubs. This type of algae is most commonly found in early spring. 


Like the Euglenophyta, algae organisms within this classification are usually unicellular organisms. Both photosynthetic and heterotrophic types are present with over 1,500 species for each type.  Dinoflagellata mainly consists of marine plankton.

The name Dinoflagellata is given due to the two dissimilar flagella that are a feature of the algae in this group. Dinoflagellata algae also have characteristics of both animal species and plant species.  

Example: Alexandrium

Alexandrium is a fascinating algae species from the Dinoflagellata genus featuring the most detrimental dinoflagellates that form toxic and destructive rapid-growth algae. There are almost 30 known species of Alexandrium that can form an ancestral population. 


Rhodophyta differs slightly from the first two classifications in this article. Rhodophyta algae organisms are commonly photosynthetic and filamentous.  It is also possible for some species to be parasitic too.

There are over 7,000 species of Rhodophyta algae, also known as red algae.

This genus of algae is one of the oldest groups of eukaryotic algae. The majority of species mostly consist of multicellular, marine algae, including many notable seaweed species. 

Example: Corallina

This species of algae is mainly characterized by a thallus that has been solidified through calcareous deposits that are limited to the interior walls of the cell.

This species of algae live up to the name of red algae with natural pink coloring. It is also possible for Corallina algae to be found in other shades of red and including yellow, purple, blue, or white.  

As the name suggests, this particular species of algae plays an integral role in the biology and maintenance of coral reefs.


This species of algae is characterized by the presence of Chlorophyll-c and carotenoids which provide their color, mitochondria featuring cristae with a tubular shape or structure, and biflagellate cells (with two flagellates), as well as containing zoospores. 

There are many classifications that are included in this category, many of which are outlined below. 


These algae are also known as diatoms. The characteristics of these algae organisms include a yellow-green appearance, silica cell walls, and bilateral symmetry.  Within this category, there are between 12,000 and 15,000 species that have been identified.

Example: Cyclotella

Cyclotella is a genus of diatoms that can be found in both marine and freshwater habitats. When viewed under the microscope, these organisms look like small, drum-shaped cells that are rarely part of a chain.  

These cells feature a valve face with a visible difference between the ornamentation of the marginal and central areas.  


This type of algae organism features colorless flagellate cells that present a vase-like appearance when viewed through a microscope. The cells of this organism are attached to a protective outer shell known as a lorica.

Lorica can attach to the surfaces of algae, plants, animals, and even water.  

This category features only 50 species.

Example: Cafeteria

The Cafeteria species is a tiny eukaryotic organism that can be found in marine habitats. As the name suggests, this particular species of algae is often consumed by protozoa and small invertebrates.

These algae play a significant role in the food chain of their habitat and help to promote the health of the ecosystem they are a part of. 


Also known as Golden Algae, this species is easily characterized by its striking color.

Within this particular species, algae can range from unicellular to colonial flagellates with various types. There are 12,000 species of algae within this group that are freshwater inhabitants. 

Example: Chrysamoeba 

When viewed under the microscope, these algae appear to be solitary or amoeboid. Amoeboid cells can be characterized by their ability to transform into a Chromulina-like shape with an extended anterior flagellum that is commonly retracted. 


The organisms within this classification are marine inhabitants. There are almost 25 species included within this classification. This class differs from others in that it is divided into two separate orders as described below.


Pedinellales are classified as single-celled algae that can be found in both marine and freshwater environments. They include 6 chloroplasts organized in a radical form with the flagella base attached directly to the nucleus. 

Order Dictyochales

These organisms are known as silicoflagellate due to having silicon present in their skeleton. They are similar to the Pedinellales with the flagella directly attached to the cell nucleus.


The Eustigmatophyceae organisms are characterized by their small size and their pale green appearance. There are only 15 species within this category. 

Example: Nannochloropsis

This micro-algae species is a marine inhabitant. The algae in these species are categorized as being insignificant, non-motile spherical organisms that cannot be made eminent through light or electron microscopy.


This species is commonly known as brown seaweed and is found in marine habitats. They vary in size from microscopic to up to 20 meters in length.  There are 1,500 species within this category.  

Example: Macrocystis

Macrocystis is a singular species of kelp otherwise known as large brown algae. This category includes the majority of all the Phaeophyceae or brown algae.

Macrocystis has floating structures at the base of its edges. The individual alga may live for up to three years.  


When these algae are viewed under a microscope, it appears as though they have appendages that resemble hair between their flagella.

This particular classification of algae plays an important role in the reduction of global warming and its effects. The majority of the carbon consumption that occurs within the ocean can be accredited to the activity of this algae. 

They are a primarily marine dwelling type that has 300 species within its classification.  

Example: Prymnesium

This particular species of algae is a unicellular motile alga. The ellipsoidal shape, combined with its unique flagellum allows this organism to move through the water. 


This classification consists of flagellates that possess mucilage-producing bodies. These flagellates are most commonly found in freshwater and marine areas.  This category consists of 50 species. 

Example: Gonyostomum

This particular type of algae is commonly found in freshwater habitats in areas all over the world. They are known to produce nuisance algae blooms and can cause an allergic reaction in people who swim in lakes that they inhabit.  


The cryptophyte division of algae is comprised of chlorophyll-c containing unicellular algae.  The organisms within this classification contain chloroplasts that have four surrounding membranes.

Within these membranes, a nucleomorph occurs between the outer membrane pair and the inner membrane pair.

Example: Plagioselmis

When these species of Cryptophyta are viewed under the microscope, they appear to have the recognizable shape of a comma and commonly have a red hue to them.

There are some species within this genus that present with grooves, although this is not present in all species, nor is it a required characteristic.  

Some algae investigators have suggested that Plagioselis algae that present without grooves should be placed into their own genus, rather than grouped in with grooved Plagioselmis. 


The species within this classification are green algae that are characterized as having mitochondria with flat cristae, flagella, chloroplast, and zoospores. There are currently between 9,000 and 12,000 species within this category.

The common colors of these species vary from yellowish-green to dark green.  The majority of Chlorophyta inhabit fresh water and are  commonly attached to rocks and wood. However, some terrestrial and marine species have also been found.

Green algae that are found within this classification are often used for studying plant evolution.  For example, single-celled Chlamydomonas can be used in the ancestral study of vascular plants.

Typically, there are both motile and non-motile species. They are capable of storing food in the form of starch. These algae vary in both their size and shape. They are found in unicellular, colonial, filamentous, and tubular forms.

Chlorophyta is divided into different classes within this classification as outlined below. 


These algae are found within freshwater habitats and include species such as Volvox, Chlorella, and Chlamydomonas


These algae are microscopic in size and include species such as filamentous Spirogyra, Desmids, and Stonewort.


These species of algae are freshwater and marine inhabitants.  They include marine flagellate Tetraselmis.


These algae are marine inhabitants that are also sometimes referred to as Micromonadophyceae.  They include the species Micromonas, Pyramimonas, and Ostreococcus.


The final subclass within the Chlorophyta classification is also the most important marine type.  The species within this category include Caulerpa, Monostroma, and Genus Ulva, also known as Sea Lettuce.

Final Thoughts

There are many different types of algae, all with different classifications and characteristics.  Each type of algae and each species within each type plays a significant role in the maintenance and protection of their environment.  

Jennifer Dawkins

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