Diatoms are autotrophs (organisms that produce their own food using light, water, and carbon dioxide), they are made up of a siliceous skeleton, and are created within a photosynthesising algae. They are located in a multitude of h20 environments. Diatoms are mainly non-motile, however, they are capable of moving along a substrate. This movement is possible as mucilaginous material is secreted upon a slit-like groove, called a raphe. Researchers have suggested that diatoms are only found in depths down to 200 meters, this is called the photic zone. However, they have been located in many areas of open water to include the benthic also known as the demersal zone (ecological region – the lowest level of the body of water and/or coast or shore) and the pelagic zone, which can be described as the part of the open water area comprising the water column, i.e., all of the sea other than that near the coast or shore or the water bed. Diatoms are part of the Chrysophyceae group, this group is generally called chrysophytes, golden-brown algae, chrysomonads, or golden algae, and are a varied group of algae protists which are either autotrophic or heterotrophic. These groups catalyze endoplasmic cysts, possess a bipartite cell wall, store oils rather than starch, and secrete silica, during their lifecycle. The average size of a diatom is between 20-200 microns in diameter. Diatoms are either solitary, or colonial. Diatoms can be used to form sediments made out of mainly diatom frustules, otherwise known as diatomites. Diatomites are used to manufacture products such as paints, toothpaste. A wider use for diatomites is to filter impurities out of water to make it safe for consumption, also diatomites are used to filter fluid products such as beer, wine, oils, and greases.
The different classifications of diatoms
Form researching several species of freshwater diatoms via light microscopy
Diatoms belong to a massive group called heterokonts, scientists have still not gained significant evidence to classify heterokonts, they may be put in groups such as; phylum, kingdom, or others which are intermediate to these groups. Heterokonts are consequently categorized anywhere from a class called Diatomophycea or Bacillariophyceae, to a division normally named Bacillariophyta, with changes in their subgroups depending on the type.
Genera and species
Currently, scientists have discovered over 200 genera of living diatoms, there are approximately 100,000 extant species.
Classes and orders of diatoms
As pennate diatoms have both a longitudinal groove and no longitudinal groove in the valve, which is called a raphe. Round, Crawford, and Mann – divided diatoms (as Bacillarophyta) into three divisions:
Class Coscinodiscophyceae: centric diatoms Round & R.M.Crawford
- Anaulales (Round & R.M.Crawford)
- Arachnoidiscales (Round)
- Asterolamprales (Round)
- Aulacoseirales (R.M.Crawford)
- Chaetocerotales (Round & R.M.Crawford)
- Chrysanthemodiscales (Round)
- Corethrales (Round & R.M.Crawford)
- Coscinodiscales (Round)
- Cymatosirales (Round & R.M.Crawford)
- Ethmodiscales (Round)
- Hemiaulales (Round & R.M.Crawford)
- Leptocylindrales (Round & R.M.Crawford)
- Melosirales (R.M.Crawford)
- Orthoseirales (R.M.Crawford)
- Paraliales (R.M.Crawford)
- Stictocyclales (Round)
- Stictodiscales (Round & R.M.Crawford)
- Triceratiales (Round & R.M.Crawford)
Class Fragilariophyceae: pennate diatoms without a raphe (araphids) F.E.Round
- Ardissoneales (F.E.Round)
- Climacospheniales (Round)
- Cyclophorales (Round & R.M.Crawford)
- Fragilariales (P.C.Silva)
- Licmophorales (Round)
- Protoraphidales (Round)
- Rhabdonematales (Round & R.M.Crawford)
- Rhaphoneidales (Round)
- Striatellales (F.E.Round)
- Tabellariales (Round)
- Thalassionematales (Round)
- Toxariales (Round)
Class Bacillariophyceae: pennate diatoms with a raphe (raphids) Haeckel, 1878, emend. D.G.Mann
- Achnanthales (P.C.Silva)
- Bacillariales Hendey
- Cymbellales (D.G.Mann)
- Dictyoneidales (D.G.Mann)
- Eunotiales (P.C.Silva)
- Lyrellales (D.G.Mann)
- Mastogloiales (D.G.Mann)
- Naviculales Bessey
- Rhopalodiales (D.G.Mann)
- Surirellales (D.G.Mann)
- Thalassiophysales (D.G.Mann)
Reduction of C02 and other toxins
Microalgal production facilities to include the use of diatoms, are used to absorb C02, and other toxins in a combined effort. These microalgal production facilities are useful for the likes of oil refining, and brewery production. Besides the removal of C02, diatoms can help eliminate biological NOx, which is nitrogen oxides that cause air pollution, to include; nitric oxide (NO) and nitrogen dioxide (NO2). Diatoms can also be used to remove nutrients from wastewater.
Biomass, which is raw waste material or purposely grown material, such as plants, animal material, waste from food factories, wood, forest waste, human waste, and sewerage plants. Is converted to energy, fibres, or industrial chemicals. Biomass can also be converted via either pyrolysis or HTL into a biocrude oil or otherwise known as Pyrolysis oil. For the conversion to be effective it needs to be hydro-processed due to its 02 content, and molecular weight. By utilising biocrude, diatom, technologies, the world can realistically be energy/fuel self-sufficient.
As an added bonus for the environment diatoms will leave a very minimalist toxic footprint, when used to produce liquid fuel. Residual waste (organic carbon) from this process can be recycled into biocrude, by utilizing thermal processing), and any remaining nutrients that are left post-processing can be reused. When not producing biocrude (non-thermal processing) the proteins in the waste are converted into certain products, such as; animal feeds, and fertilizers. While the frustules of the diatoms (the cell wall of the diatoms), are useful for the removal of heavy metals from industrial wastewater. For example, copper can be removed from wastewater, by using frustules.
Production and harvesting
The molecular scaffolding of diatoms and other microalgae, are quite similar to some land plants, however, microalgae can produce around 30 times more oil, than that of commercial oilseed crops. This is because single-cell organisms are far more efficient at converting solar energy as opposed to nonphotosynthetic plant cells.
Nasa are currently working on a project called OMEGA, which involves growing algae in enclosures, located offshore. With a view to clean freshwater, capture carbon dioxide, and produce biofuel. Thus, reducing the agricultural footprint.
The NASA project mainly consists of large flexible plastic tubes, named photobioreactors. The photobioreactors which contain freshwater algae growing in wastewater, are floated within enclosures in seawater.
The algae within the photobioreactors harvest energy from the sun, carbon dioxide, and gain nutrients from the wastewater. The algae naturally clean the wastewater by removing nutrients that contribute to hypoxic dead zones found in the world’s oceans, and large lakes. The OMEGA project produces biomass, this biomass can be converted into biofuels, and other products such as fertilizer, and animal feed.
The OMEGA project was developed to find out if a floating algae cultivation system is a feasible option for helping to make the world more self-sufficient. It has been suggested by research scientists and engineers that the OMEGA project is an effective way to cultivate microalgae, and treat wastewater.
NASA’s OMEGA project has been suggested to be an effective option for producing global friendly aviation fuels. This could ultimately reduce adverse fossil fuel footprints, by reducing; greenhouse gases, ocean acidification, and increasing national security.
NASA OMEGA project
Open system productions
Aquaculturists have been producing diatoms in closed facilities for a long period of time, embracing seed open pod technology. however, it has become apparent over the years that there are have been consistent misfortunes, due to the; initial capital costs, ongoing routine maintenance, and the need to remove heat. More so now, Diatom Chaetoceros sp production has been successful in open production environments.
Moving dangerous sea life
Diatoms are also useful for moving dangerous sea life to other ocean locations, for their wellbeing, and for the safety of humans. This process is fulfilled by producing diatoms in open system production facilities. Once an adequate amount of diatoms have been harvested, they are transported to a safe aquatic environment. Here the diatoms are fed on by Zooplankton, in turn, the Zooplankton sustains other larger aquatic organisms, such as fish. Effectively, the ocean sea life is dependant on the diatom either directly or non-directly.
As discussed, the diatom is essential for the world’s ecosystem to sustain itself, via combatting environmental issues, such as; filtration systems, C02 conversion to oxygen, and moving dangerous sea life. It is therefore important to sustain the diatom, for the world to survive.
Diatoms help the world as we know it survive, National Geographic