IDs have been checked against "The Freshwater Algal Flora of the British Isles" (FAFBI). Some older IDs done using "How to Know the Freshwater Algae" (Prescott).
Question marks (?) added where ID is uncertain.
| Name | Image Links | Description |
|---|---|---|
| Scenedesmus | 1 2 3 4 5 6 7 | coenobial Chlorophyte: up to 4 spindle-shaped cells clustered together |
| Scenedesmus abundans | 1 | |
| Scenedesmus aculeolatus | 1 2 3 | |
| Scenedesmus ?armatus v. bicaudatus | 1 | |
| Scenedesmus communis | 1 2 3 4 | |
| Scenedesmus dimorphus | 1 2 3 4 | |
| Scenedesmus hystrix | 1 | |
| Scenedesmus obliquus | 1 | |
| Scenedesmus obtusus | 1 | |
| Scenedesmus opoliensis | 1 | |
| Scenedesmus ?opoliensis v. carinatus | 1 | |
| Schizochlamydella | 1 2 3 4 5 6 7 | colonial Chlorophyte: spherical cells in a structureless mucilage sheath surrounded by semicircular mother cell-wall fragments |
| Scytonema | 1 2 | filamentous Cyanobacterium: sheathed, false branching not at heterocyst, sometimes two branches emerging at the same point |
| Selenastrum capricornutum | 1 2 | Crescent-shaped unicellular chlorophyte: the capricornutum means 'like a goat's horns '. This is its old name -it is now Pseudokirchneriella subcapitata. It is widely used in toxicity testing. |
| ?Sellaphora laevissima | 1 2 3 | unicellular Diatom |
| Sirogonium | 1 2 3 4 | filamentous Chlorophyte, related to and similar to Spirogyra, but parallel, ribbon-like chloroplasts form less than half a complete twist round the circumference. |
| Snowella | 1 2 3 4 | colonial Cyanobacterium: oval cells in spherical mucilage forming a layer some distance from outside, at the end of branched stalks |
| Sorastrum | 1 2 3 | colonial chlorophyte (coenobium): cells linked by mucilage stalks to centre of spherical colony; cells with short spines |
| Sphaerobotrys fluviatilis | 1 2 | colonial Chlorophyte: grows attached; cells somewhat pear-shaped, arranged in rows |
| Sphaerocystis sp. | 1 2 3 4 5 6 7 8 9 10 11 | colonial
Chlorophyte (coenobium): spherical cells regularly arranged in a colonial
mucilage sheath, without pseudocilia; reproduce by autospores which
may remain in mother cell wall for a time. See also Coenochloris. Images 7,8 & 9 show the effect of increasing exposure to Lugol's Iodine |
| ?Sphaerocystis planctonica | 1 2 3 | Showing spherical clusters of (?)autospores (approx. 3µm diameter) within a mucilage sheath |
| Sphaerozosma | 1 | filamentous Desmid: each cell with a deep median incision and semicells a flattened ellipse; linked by terminal extensions to form long filaments, sometimes with a mucilage sheath. (There are similar related genera, eg, , eg, Spondylosium) |
| Spirogyra | Descriptive notes | filamentous Chlorophyte: non-branching, long-cylindric cells with spiral band chloroplasts. Feels very smooth, hence common name 'Pond Silk' |
| Spirogyra 11µm. | 1 | |
| Spirogyra 15 µm. | 1 | Single cell: contrast shape with Spirotaenia |
| Spirogyra 17µm. | 1 | |
| Spirogyra 20µm. | 1 2 | |
| Spirogyra 22µm. | 1 | |
| Spirogyra 28µm. | 1 | |
| Spirogyra 38µm | 1 | |
| Spirotaenia | 1 2 3 4 | unicellular Chlorophyte (Placoderm desmid) : cylindrical cell with rounded ends and spiral band chloroplast |
| Spondylosium sp. | 1 | filamentous Desmid: each cell with a deep median incision and semicells a flattened ellipse (similar to some Cosmarium); linked to form long filaments, sometimes with a mucilage sheath. (There are similar related genera eg. Sphaerozosma) |
| Spondylosium planum | 1 2 3 | |
| Staurastrum | Details | unicellular Desmid: semicells without marginal incisions or spines, but have many small processes and arms tipped with spines (2 or more arms per semicell) |
| Staurastrum anatinum | 1 2 3 | |
| Staurastrum arctiscon | 1 2 3 4 | |
| Staurastrum armigerum fo. furcigerum | 1 2 3 4 5 6 7 | |
| Staurastrum asperum | 1 | |
| Staurastrum avicula | 1 2 3 ?4 5 | |
| Staurastrum bieneanum | 1 2 3 | |
| Staurastrum ?cerastes | 1 2 3 4 5 6 | |
| Staurastrum chaetoceras | 1 2 | |
| Staurastrum cingulum | 1 2 3 4 | |
| Staurastrum ?cingulum v. obesum | 1 2 | |
| Staurastrum crenulatum | 1 | |
| Staurastrum ?cyrtocerum | 1 2 | |
| Staurastrum ?dilatatum | 1 | |
| Staurastrum ?furcatum | 1 2 | |
| Staurastrum gracile | 1 2 3 | |
| Staurastrum ?hirsutum | 1 2 3 | |
| Staurastrum ?hirsutum v. muricatum | 1 | |
| Staurastrum inflexum | 1 | |
| Staurastrum johnsonii | 1 2 | |
| Staurastum longispinum | 1 2 | |
| Staurastrum lunatum | 1 2 3 4 5 6 7 8 9 | |
| Staurastrum manfeldtii | 1 | |
| Staurastrum ophiura | 1 2 3 4 5 | |
| Staurastrum pingue | ?1 | |
| Staurastrum planctonicum | 1 2 | |
| Staurastrum polytrichum | 1 2 3 | |
| Staurastrum proboscideum | 1 2 | |
| Staurastrum pseudopelagicum | 1 2 | |
| Staurastrum punctatulum | 1 | |
| Staurastrum sexangulare | 1 | |
| Staurastrum teliferum | 1 ?2 3 4 | |
| Staurodesmus | Details | unicellular Desmid: semicells have a smooth appearance, with spines marginal, or at the angles |
| Staurodesmus aversus | 1 | |
| Staurodesmus convergens | 1 2 3 | |
| Staurodesmus cuspidatus | 1 2 3 | |
| Staurodesmus dejectus | 1 2 | |
| S. dejectus fo. apiculatus | 1 2 3 | |
| Staurodesmus ?extensus | 1 2 | |
| Staurodesmus ?indentatus | 1 | |
| Staurodesmus mamillatus | 1 2 3 | |
| Staurodesmus ?megacanthus | 1 2 | |
| Staurodesmus subtriangularis | 1 2 3 4 5 | |
| Staurodesmus triangularis | 1 2 3 | |
| Stauroneis legumen | 1 | unicellular Diatom: cell longer than broad, 2 chloroplasts against the girdles. S.legumen is 'bean-shaped' |
| ?Staurosirella | 1 | unicellular Diatom: |
| Stenopterobia sigmatella | 1 2 3 4 | unicellular Diatom: sigmoid, narrow |
| Stephanodiscus minutulus | 1 | unicellular centric Diatom |
| Stigeoclonium | Descriptive notes | filamentous Chlorophyte: branched, ends of branches pointed or drawn out into long hairs; grows attached by a prostrate basal system of filaments (usually not collected when sampling) which is important in identifying species. Chloroplast a parietal plate; no colonial mucilage. Cf. Draparnaldia and Chaetophora |
| Stigeoclonium | 1 | |
| Stigeoclonium sp. | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | |
| Stigeoclonium ?amoenum | 1 2 3 | |
| Stigeoclonium farctum | 1 2 3 | |
| Stigeoclonium helveticum | 1 2 3 4 5 | |
| Stigeoclonium tenue | 1 2 | |
| Stigonema | 1 2 3 | branched filamentous Cyanobacterium: cells spheroidal in a dense mucilaginous sheath, uniseriate in younger branches becoming multiseriate with branches starting as small protuberances growing out at right angles, plant a dark brown or green colour |
| Stylosphaeridium | 1 2 3 | unicellular chlorophyte: epiphytic on other algae esp. cyanobacteria, attached by means of a stalk |
| Surirella angusta | 1 | unicellular Diatom: fairly large cells with prominent marginal costae |
| Surirella capronii | 1 2 3 4 5 | |
| Surirella elegans | 1 2 | |
| Synechococcus | 1 2 | Cyanophyte: solitary, or a pair of cells following cell division, blue-green colour without a mucilage sheath |
| Synechococcus aeruginosus ? | 1 | |
| Synechocystis | 1 | Cyanophyte: solitary or a pair of cells followiing cell division, blue-green colour with a mucilage sheath. |
| Synedra acus | 1 2 (both in valve view) | unicellular Diatom: long, narrow cells with 2 chloroplasts against the girdles |
| Synedra berolinensis | 1 2 2 | |
| Synedra ulna | 1 (girdle view) 2 | |
| Synura sp. | 1 | colonial Chrysophyte: oval cells with 2 brown chloroplasts and 2 flagella. |
