Diatoms
SOME IMAGES ON THE DIATOM PAGES ARE IN THE PROCESS OF BEING REMOVED OR CHANGED
A representative of each genus of diatom found in sediment samples from sites in West Cork are shown below. For each genus, click on the image to see all species found in sediments in West Cork that are within that genus. Alternatively, click on a genus in the list under the diatoms tab on the right. The diatom page will display in a new tab.
All images are photographs taken through a microscope at either x400 or x1000. Most images are taken using phase contrast to better define the structure and outline of the diatoms. For details of how samples were prepared for examination see here.
Species are listed on the genus pages, and the sites and depths at which they were found are also detailed.
Achnanthidium
Achnanthidium is a mainly freshwater genus, often found in high energy waters, such as streams and rivers, or the upper layers of lakes.
Amphora
Both freshwater and marine genera. Amphora ovalis is a frequently occurring freshwater species.
Aulacoseira
A freshwater floating (planktonic) genus, most commonly found in large rivers and lakes.
Brachysira
A variable genus, but generally freshwater. May be unattached and planktonic, or benthic, or attached, occurring in a range of water types. Blooms may occur in bog waters.
Caloneis
Caloneis species may be freshwater, marine, brackish, or alkaline in preference. The species silicula and schumanniana are both freshwater species.
Cavinula
Species are from freshwater, low nutrient environments high in oxygen, including damp soils.
Cocconeis
A genus of solitary living species, often found attached to a surface, including other diatoms. Both marine and freshwater species.
Cyclotella
Cyclotella is a genus containing both freshwater and marine species. Cells may be solitary or may form colonies in chains.
Cymbella
The genus Cymbella is a bottom living (benthic) genus, often producing stalks. Cymbella cymbiformis is a freshwater species.
Cymbopleura
Cymbopleura is a genus of freshwater solitary diatoms that live on the bottom of water bodies (benthic).
Encyonema
Encyonema - The genus Encyonema is largley a bottom living (benthic) genus. Diatoms in these species may be solitary or colonial. Encyonema neomesiana (neomesianum), ventricosa, and minutum are freshwater species.
Epithemia
Epithemia - all species in the genus Epithemia are freshwater species. They are solitary and live on surfaces, including mud and other individuals. Tolerant of alkaline conditions.
Eunotia
Eunotia - individuals in the genus Eunotia occur as single cells, or attached, or in colonies. Eunotia is generally found in acid waters and bog conditions with high humic acid and low oxygen (dystrophic). Eunotia bilunaris, implicata, incisa, neocompacta, pectinalis, soleirollii, tetraodon, and veneris are all freshwater species.
Fragilaria
Fragilaria - a freshwater planktonic diatom, often abundant in lakes.Fragilaria do not have raphs (araphid), the slit by which mucus is extruded to aid movement.
Frustulia
Frustulia - to be completed.
Geissleria
Geissleria - a freshwater genus.
Gomphonema
Gomphonema - Gomphonema acuminatum, capitatum, coronatum, gracile, micropus, parvulum, subclavatum, truncatum are all freshwater species. Gomphonema often grows on mucilagenous stalks in water that is near neutral pH.
Halamphora
Halamphora - Halamphora was until 2009 a subgenus of the genus Amphora, but is now a genus in its own right. Halamphora species are most usually marine or brackish water, but some species may be found in freshwater.
Hannaea
Hannaea - Hannaea inhabits waters that are low nutrient but high in oxygen (oligotrophic). It grows attached to surfaces at the bottom of the water column (benthic).
Mayamaea
Mayamaea - Mayamaea is found in water with high nutrient levels as well as in temporary wet places (ephemeral), that are subject to reduction and even drying out.
Meridion
Meridion - Meridion circulare is a freshwater species. The frustules are either parallel sided or wedge shaped in girdle view, and may attach and form into fan shaped colonies.
Navicula
Navicula - Navicula is a large genus. Navicula cryptocephala and radiosa are both freshwater species. The genus is biraphid, that is possessing raphes on both valves - and therefore very motile.
Naviculadicta
Naviculadicta - There is little information available on Naviculaidcta that is pertinent. See here for listing of references.
Nitzschia
Nitzschia - A genus with a very large number of species, many of which are hard to distinguish from other species.
Pinnularia
Pinnularia - Another genus with a large number of species. Pinnularia are often large. Many species are found in abundance in slightly acid environments.This genus is also biraphid and thus motile.
Planothidium
Planothidium - Planothidium have a raphe slit on only one of the two valves. This valve is used to attach the cell to a surface.
Pseudopodosira
Pseudopodosira - identification unsure.
Pseudostaurosira
Pseudostaurosira - Pseudostaurosira is an araphid genus - these species have no raphe. Some species form colonies by individual cells linking face to face.
Reimeria
Reimeria - Reimeria uniseriata is a benthic (bottom living) freshwater species.
Rhopalodia
Rhopalodia - Rhopalodia parallela is a freshwater species. Rhopalodia favours low nitrogen environment where it can benefit from the symbiotic cyanobacteria that enable the diatom to fix nitrogen from the atmosphere.
Sellaphora
Sellaphora - Sellaphora inhabits waters of near neutral pH. Sellaphora pupula is a freshwater species. See the references for informsation on the pupula group.
Stauroforma
Stauroforma - Stauroforma exiguiformis is a freshwater species. Stauroforma often form colonies by the frustules linking together side by side.
Stauroneis
Stauroneis - Stauroneis - all species are freshwater and benthic (bottom living), commonly found in bogs, lakes and ponds, and also in wet soils and on moss.
Staurosira
Staurosira - Staurosira is an araphid genus - thus probably planktonic (?). Staurosira construens is a freshwater species.
Surirella
Surirella - Surirella is a benthic genus, found particularly on mud surfaces at the bottom of the water column. The genus is largely tolerant of different water types and chemical makeup. The raphe is raised and runs all around the perimeter of the frustules making Surirella species very mobile. Some specimens can be quite large. Surirella linearis is a freshwater species. Surirella is generally relatively recogniseable by it's shape and character.
Tabellaria
Tabellaria - Tabellaria are araphid - possess no raphe - and thus probably largely planktonic, or found amongst water plants. They form colonies either as chains, or as star shaped form with frustules attached all at one end in the centre. Tolerant of most water types. Flocculosa and fenestra are both freshwater species.
Tabularia
Tabularia - Tabularia is araphid (possessing no raphe) and thus largely planktonic, often found in waters that are high in dissolved solids. The frustiles may form colonies either as star shapes, or side by side ribbon colonies. Tabularia tabulata is a freshwater/marine species.
Ulnaria
Ulnaria - Ulnaria is an araphid genus (possessing no raphe); however they often attach to the bottom by a pad of mucialge secreted from one apex of the cell. Common in rivers and lakes. Ulnaria ulna is a freshwater species.
Unidentified
Unidentified - individuals that have not yet been successfully identified.