A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion tonnes of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.
Photosynthetic picoplankton or picophytoplankton is the fraction of the photosynthetic phytoplankton of cell sizes between 0.2 and 2 µm. It is especially important in the central oligotrophic regions of the world oceans that have very low concentration of nutrients.
Acanthoceras is a genus of radially symmetric planktonic diatoms comprising two taxonomically accepted species. They do not have any raphe and therefore lack motility. It appears rectangular with two setae extending from each valve. Not much is known about this genus because it is easily destroyed using common preparation techniques. They can be found all over North America in small lakes and short-lasting ponds.
Pseudo-nitzschia is a marine planktonic diatom genus that accounts for 4.4% of pennate diatoms found worldwide. Some species are capable of producing the neurotoxin domoic acid (DA), which is responsible for the neurological disorder in humans known as amnesic shellfish poisoning (ASP). Currently, 58 species are known, 28 of which have been shown to produce DA. It was originally hypothesized that only dinoflagellates could produce harmful algal toxins, but a deadly bloom of Pseudo-nitzschia occurred in 1987 in the bays of Prince Edward Island, Canada, and led to an outbreak of ASP. Over 100 people were affected by this outbreak after consuming contaminated mussels; three people died. Since this event, no additional deaths have been attributed to ASP, though the prevalence of toxic diatoms and DA has increased worldwide. This anomaly is likely due to increased awareness of harmful algal blooms (HABs) and their implications for human and ecosystem health.
Hemicentrotus pulcherrimus is a species of sea urchin, the only one in the monotypic genus Hemicentrotus. It was first described by the American engineer and marine zoologist Alexander Agassiz in 1864 as Psammechinus pulcherrimus. Its range extends along the coasts of Korea and China, and in Japan from Kyūshū to Ishikari Bay. An edible species, it is harvested from Kyūshū to Fukui, in the Sea of Japan.
Ornithocercus is a genus of planktonic dinoflagellate that is known for its complex morphology that features considerable lists growing from its thecal plates, giving an attractive appearance. Discovered in 1883, this genus has a small number of species currently categorized but is widespread in tropical and sub-tropical oceans. The genus is marked by exosymbiotic bacteria gardens under its lists, the inter-organismal dynamics of which are a current field of research. As they reside only in warm water, the genus has been used as a proxy for climate change and has potential to be an indicator species for environmental change if found in novel environments.
Chaetoceros pseudocurvisetus is a marine diatom in the genus Chaetoceros. It is an important primary producer in the oceans. C. pseudocurvisetus forms resting spores and resting cells, particularly in the absence of essential nutrients.
Thalassiosira weissflogii is a species of centric diatoms, a unicellular microalga. It is found in marine environments and also in inland waters in many parts of the world. It is actively studied because it may use C4-plant style strategies to increase its photosynthetic efficiency.
Bacillaria is a diatom genus in the family Bacillariaceae.
Thetys vagina, or the twin sailed salp, is the largest known solitary species of salp and the only valid species of the genus Thetys. First described by W.G Tilesius in 1802, the species is transparent and gelatinous, making it difficult to be seen in water, which is helpful in avoiding predators. The fossil range is very recent. Other animals often mistaken for T. vagina are Salpa fusiformis, Aurelia aurita, and Pegea confoederata. There is no known status of conservation in this species. T. vagina DNA was sequenced as part of a larger project in 2014 where spiny lobster larvae were found attached to T. vagina and consuming it.
Thalassiosiraceae is a family of diatoms in the order Thalassiosirales. The family of Thalassiosiraceae have the unique quality of having a flat valve face. These diatoms are common in brackish, nearshore, and open-ocean habitats, with approximately the same number of freshwater and marine species. Thalassiosiraceae are a centric diatom full of fultoportula. These can often be mistaken for Areola. These belong to many diatom families and can be found in different forms such as the different Areolae that can be found on Navicula or Gomphoneis known as lineolate and punctate. Unlike naviculaceae who are symmetrical in shape some Thalassiosiraceae take on being tangentially undulate.
Skeletonema is a genus of diatoms in the family Skeletonemataceae. It is the type genus of its family. The genus Skeletonema was established by R. K. Greville in 1865 for a single species, S. barbadense, found in the Barbados deposit [Jung 2009]. These diatoms are photosynthetic organisms, meaning they obtain carbon dioxide from their surrounding environment and produce oxygen along with other byproducts. Reproduce sexually and asexually [Guiry 2011]. Skeletonema belong to the morphological category referred to as centric diatoms. These are classified by having valves with radial symmetry and the cells lack significant motility [Horner 2002]. Skeletonema are cylindrical shaped with a silica frustule. Cells are joined by long marginal processes to form a filament [Horner 2002]. Their length ranges from 2-61 micrometers, with a diameter ranging from 2-21 micrometers [Hasle 1997]. They are found typically in the neritic zone of the ocean and are highly populous in coastal systems [Jung 2009]. The genus is considered cosmopolitan, showing a wide range of tolerance for salinity and temperature [Hasle 1973]. For example, they have been found in various aquatic environments such as brackish or freshwater. Skeletonema are found worldwide excluding Antarctic waters [Hevia-Orube 2016]. Some harmful effects these diatoms may have on an ecosystem are attributed to large blooming events which may cause hypoxic events in coastal systems. Additionally, they are known to cause water discoloration [Kraberg 2010].
Cyclotella is a genus of diatoms often found in oligotrophic environments, both marine and fresh water. It is in the family Stephanodiscaceae and the order Thalassiosirales. The genus was first discovered in the mid-1800s and since then has become an umbrella genus for nearly 100 different species, the most well-studied and the best known being Cyclotella meneghiniana. Despite being among the most dominant genera in low-productivity environments, it is relatively understudied.
Asterionella formosa is a species of diatom belonging to the family Tabellariaceae.
Gyrosigma is a genus of diatoms belonging to the family Pleurosigmataceae.
The Great Calcite Belt (GCB) refers to a region of the ocean where there are high concentrations of calcite, a mineral form of calcium carbonate. The belt extends over a large area of the Southern Ocean surrounding Antarctica. The calcite in the Great Calcite Belt is formed by tiny marine organisms called coccolithophores, which build their shells out of calcium carbonate. When these organisms die, their shells sink to the bottom of the ocean, and over time, they accumulate to form a thick layer of calcite sediment.
Greta Albrecht Fryxell was a marine scientist known for her work on the biology and taxonomy of diatoms. In 1996, she was elected a fellow of the American Association for the Advancement of Science.
Skeletonema costatum is a cosmopolitan centric diatom that belongs to the genus Skeletonema. It was first described by R. K. Greville, who originally named it Melosira costata, in 1866. It was later renamed by Cleve in 1873 and was more narrowly defined by Zingone et al. and Sarno et al. Skeletonemacostatum is the most well known species of the genus Skeletonema and is often one of the dominant species responsible for red tide events.
Nupela is a genus of diatom. Species of Nupela typically measure less than 20 µm. The genus was first described as being isovalvar, however many recently described species are heterovalvar. The main diagnostic characteristic of the genus is the presence of an external covering over the areolae. The genus was circumscribed by Wim Vyverman and Pierre Compère in 1991, with Nupela giluwensis asigned as the type, and at that time, only species.
Pleurosigma is a genus of widely distributed diatoms found abundantly in brackish to marine waters. It is a group of primarily pelagic or benthic species found in large populations on sediments, although some species are also found in planktonic samples.
