Diatom flora of Toome Bridge - Northern Ireland

 Version 3
Compiled by Richard T. Carter


Please click on linked species below for image and description

A. Introduction
The freshwater diatomites of the Toome Bridge area, County Antrim, Northern Ireland, have been providing diatomists with remarkably well-preserved material for study since the mid-19th century. Antique microscope slides of this material are abundant, and often come up for sale on internet sites like eBay. Many researchers have continued to collect samples from these deposits until the present day, and most diatomists possess microscope slides of this material. Such slides are often objects of great beauty, particularly when made from well-cleaned samples.

The Toome Bridge diatomites occur over a fairly large area in the valley of the Lower River Bann, which serves as the only outlet for Lough Neagh, the largest body of fresh water in the British Isles. Recent studies have shown that diatomite deposition began around 2300 BC, when water levels in the Lough were considerably higher than they are today. Radiocarbon dating of oak wood from beneath some of the diatomite deposits suggests that much of the diatomite was formed subsequent to around 200 BC.1

This list of the diatom flora of the Toome Bridge deposits is based largely on my own identifications of species found on slides in my possession, as described below in Section C. I have also included a few identifications made by Robert I. Firth, as recorded in the holdings of the California Academy of Sciences. However, this second version of the floral list has profited greatly from my study of a similar list, prepared by Hartmut Besançon of Belgium, that was kindly provided by Raymond Hummelink (with Mr. Besançon's permission).

The Toome Bridge deposits exhibit a number of interesting floristic properties: for example, the genera Pinnularia and Stauroneis are well-represented, while Navicula and Nitzschia are relatively impoverished, both in number of species and individuals (with the exception of Navicula radiosa). Aulacoseira is very abundant in numbers of individuals, but not in species. Most samples are fairly uniform, but samples from Ballyscullan have a few interesting differences; e.g., an abundance of Stauroneis kriegeri.

There are undoubtedly some errors in my identifications, but they are the best I can offer at present, based on my rather limited library. The Gomphonema and Pinnularia species, in particular, may bear names that are not the most current. The list is also not complete, by any means, although this second version increases the count of species and varieties from 104 to almost 140. I will continue to study these materials, and will continue to update the floral list from time to time. My purpose in offering this list is to hopefully provide the interested diatomist with a little assistance in beginning the process of identifying the diatoms present in their own samples.

The estimates of relative abundance for each species should be interpreted as follows:
Abundant = numerous specimens found on most slides
Common = many specimens found on most slides
Rare = a few specimens occur on some slides
Very Rare = one valve or frustule seen on one slide
These estimates are purely impressionistic, and no statistical significance is intended!

The numbers following each listed species refer to the list of slides in Section C. These numbers are not exhaustive; i.e., I have only included numbers when I have happened to notice a species on a particular slide. Not all of the samples have been studied equally - I have particularly concentrated on samples that are clean, and with good preservation.

Comments and corrections are most welcome!

B. Floral List

Achnanthes calcar Cleve
Rare 2,7
Achnanthes obliqua (Gregory) Hustedt2
Very Rare 9
Achnanthes saxonica Krasske
Common 7,8

Achnanthidium exiguum (Grunow) Czarnecki
Rare 7

Amphora copulata (Kützing) Schoeman et Archibald3
Abundant 2,9,13,14
Amphora ovalis (Kützing) Kützing
Rare 14

Aneumastus minor (Hustedt) Lange‑Bertalot
Rare 4,5
Aneumastus tusculus (Ehrenberg) D. Mann et Stickle
Common 1,2,8,9,13

Asterionella formosa Hassall
Very Rare 4

Aulacoseira crenulata (Ehrenberg) Krammer
Rare 2
Aulacoseira islandica (O. Müller) Simonsen
Rare 5
Aulacoseira cf. subarctica (O. Müller) Haworth
Abundant 2

Brachysira serians (Brébisson) Round and Mann
Rare 4

Caloneis latiuscula (Kützing) Cleve
Very Rare 14
Caloneis leptosoma (Grunow in Van Heurck) Krammer
Rare 9
Caloneis ventricosa (Ehrenberg) Meister4
Common 2,9
Caloneis ventricosa var. subundulata (Grunow) Patrick
Rare 2
Caloneis ventricosa var. truncatula (Grunow) Meister
Rare 8

Campylodiscus hibernicus Ehrenberg5
Very Rare 13

Cavinula jaernefeltii (Hustedt) D. Mann and Stickle
Rare 5
Cavinula lacustris (Gregory) D. Mann and Stickle
Very Rare 5
Cavinula pseudoscutiformis (Hustedt) D. Mann and Stickle
Rare 5,7
Cavinula scutelloides (W. Smith ex Gregory) Lange-Bertalot
Rare 4,5,9

Cocconeis pediculus Ehrenberg
Rare 9
Cocconeis placentula Ehrenberg
Rare 2
Cocconeis placentula var. euglypta (Ehrenberg) Cleve
Rare 5,7,8
Cocconeis placentula var. lineata (Ehrenberg) Van Heurck
Abundant 2,7,8,13,14
Cocconeis cf. thumensis A. Mayer
Rare 5,8

Craticula cuspidata var. héribaudii (Peragallo) D. Mann
Rare 8,9

Cyclotella ocellata Pantocsek
Abundant 2,8,9,13
Cyclotella radiosa (Grunow in Van Heurck) Lemmermann6
Abundant 1,2,8,9,10,13

Cymatopleura elliptica var. hibernica (W. Smith) Van Heurck
Abundant 1,2,8,10,13
Cymatopleura solea (Brébisson) W. Smith
Rare 4,5,8,13

Cymbella aspera (Ehrenberg) Peragallo in Pelletan
Abundant 1,2,8,9,10,13,14
Cymbella cistula (Ehrenberg) Kirchner
Common 2,13,14
Cymbella cymbiformis Agardh
Rare 5
Cymbella designata Krammer in Krammer and Lange‑Bertalot
Rare 1,2
Cymbella ehrenbergii Kützing7
Common 5
Cymbella helvetica Kützing
Rare 14
Cymbella hybrida Grunow ex Cleve
Rare 8
Cymbella cf. reinhardtii Grunow ex A. Schmidt
Rare 14
Cymbella subcuspidata Krammer
Common 2,5,14

Denticula cf. kuetzingii Grunow
Very Rare 7

Diatoma vulgaris var. linearis Grunow in Van Heurck
Rare 5

Diploneis domblitensis var. subconstricta A. Cleve
Rare 2,5
Diploneis elliptica (Kützing) Cleve
Abundant 5
Diploneis puella (Schumann) Cleve
Rare 5

Ellerbeckia arenaria fo. teres (Brun) Crawford
Very Rare 8

Encyonema cf. caespitosum Kützing
Rare 8
Encyonema elginense (Krammer) D. Mann
Very Rare 5
Encyonema hebridicum (Gregory) Grunow ex Cleve
Very Rare 5
Encyonema cf. paucistriatum (A. Cleve‑Euler) D. Mann8
Rare 2,9
Encyonema prostratum (Berkeley) Kützing
Rare 14
Encyonema turgidum (Gregory) Grunow
Rare 2,5

Epithemia adnata (Kützing) Brébisson
Rare 2
Epithemia argus (Ehrenberg) Kützing
Common 5
Epithemia frickei Krammer
Rare 5,14
Epithemia goeppertiana Hilse
Common 2,14
Epithemia hyndmannii W. Smith
Common 1,5,13,14
Epithemia smithii Carruthers
Rare 14
Epithemia sorex Kützing
Rare 5,14
Epithemia turgida (Ehrenberg) Kützing
Rare 2

Eucocconeis flexella (Kützing) Cleve
Very Rare 5

Eunotia bilunaris (Ehrenberg) Mills
Rare 7,8
Eunotia circumborealis Lange‑Bertalot and Nörpel
Rare 9
Eunotia formica Ehrenberg
Common 2,9,14
Eunotia glacialis Meister
Abundant 2
Eunotia hemicyclus (Ehrenberg) Ralfs in Pritchard
Very Rare 4
Eunotia cf. pectinalis (O. F. Müller) Rabenhorst
Abundant 2,14
Eunotia praerupta var. bidens Grunow in Cleve and Grunow
Rare 7
Eunotia praerupta var. curta Grunow in Van Heurck
Rare 2

Fragilaria capucina var. vaucheriae (Kützing) Lange‑Bertalot
Rare 7,8
Fragilaria heidenii Oestrup
Rare 9

Frustulia amphipleuroides (Grunow) A. Cleve‑Euler9
Rare 9,13

Geissleria ignota var. palustris (Hustedt) Lange‑Bertalot and Metzeltin
Rare 4,7

Gomphonema acuminatum Ehrenberg
Abundant 2,8,10,13,14
Gomphonema acuminatum var. coronatum (Ehrenberg) W. Smith
Common 8,9,14
Gomphonema affine Kützing
Common 2,9
Gomphonema olivaceum (Hornemann) Brébisson
Rare 5,9
Gomphonema sarcophagus Gregory
Rare 9
Gomphonema truncatum Ehrenberg
Common 2,5,9,13,14
Gomphonema vibrio var. intricatum (Kützing) Ross
Common 2,9,13

Gyrosigma acuminatum (Kützing) Rabenhorst
Rare 5,8
Gyrosigma attenuatum (Kützing) Rabenhorst
Common 2,5,8

Hantzschia amphioxys (Ehrenberg) Grunow
Common 2,8,9,13
Hantzschia elongata (Hantzsch) Grunow
Common 2,8,13,14

Karayevia clevei (Grunow) Round and Bukhtiyarova
Rare 7
Karayevia clevei var. rostrata (Hustedt) Kingston
Very Rare 5

Mastogloia elliptica var. danseii (Thwaites) Cleve
Very Rare 5
Mastogloia smithii Thwaites ex W. Smith
Rare 4,5
Mastogloia sp. A10
Very Rare 5

Melosira undulata var. normanii Arnott in Van Heurck
Common 2,4,5,8,10,13,14
Melosira varians Agardh
Rare 2,13

Meridion circulare var. constrictum (Ralfs) Van Heurck
Rare 7,8,9

Navicula amphibola Cleve
Common 1,2,8,9,10,14
Navicula farta Hustedt
Very Rare 14
Navicula radiosa Kützing
Abundant 2,5,13,14
Navicula rhynchocephala Kützing
Rare 5,8
Navicula semen Ehrenberg emend. Donkin
Very Rare 2

Neidium affine (Ehrenberg) Pfitzer
Common 8
Neidium bisulcatum (Lagerstedt) Cleve
Rare 8
Neidium bisulcatum var. subundulatum (Grunow) Reimer
Rare 8
Neidium hitchcockii (Ehrenberg) Cleve
Very Rare 8
Neidium iridis (Ehrenberg) Cleve
Common 2,5,9,13,14
Neidium productum (W. Smith) Cleve
Common 2,5,9,10

Nitzschia sinuata var. tabellaria (Grunow) Grunow
Very Rare 7

Pinnularia acrosphaeria W. Smith
Abundant 1,2,8,9
Pinnularia biceps Gregory
Common 2
Pinnularia borealis Ehrenberg
Very Rare 9
Pinnularia borealis var. rectangularis Carlson
Very Rare 2
Pinnularia brevicostata Cleve
Abundant 2,9,13
Pinnularia cardinalis (Ehrenberg) W. Smith
Common 2,14
Pinnularia divergens W. Smith
Common 2,13,14
Pinnularia hemiptera (Kützing) Rabenhorst
Common 2
Pinnularia maior (Kützing) W. Smith
Common 1,2
Pinnularia mesolepta (Ehrenberg) W. Smith
Common 2
Pinnularia nobilis (Ehrenberg) Ehrenberg
Abundant 2,13,14
Pinnularia stomatophora (Grunow in A. Schmidt) Cleve11
?? 1
Pinnularia stomatophoroides A. Mayer
?? 1
Pinnularia streptoraphe Cleve
Common 2
Pinnularia subcapitata var. subrostrata Krammer
Rare 7
Pinnularia substomatophora Hustedt
Common 2
Pinnularia viridis (Nitzsch) Ehrenberg
Abundant 2

Placoneis elginensis (Gregory) E. Cox
Rare 7,9
Placoneis elginensis var. cuneata (M. Moller ex Foged)12
Rare 7

Planothidium lanceolatum (Brébisson in Kützing) Lange-Bertalot
Rare 5,7
Planothidium oestrupii (A. Cleve‑Euler) Round and Bukhtiyarova
Rare 5,7
Planothidium peragallii (Brun and Héribaud) Round and Bukhtiyarova
Very Rare 5

Pseudostaurosira brevistriata (Grunow in Van Heurck) Williams and Round
Rare 7

Rhopalodia gibba (Ehrenberg) O. Müller
Common 2,5,8,14

Sellaphora americana (Ehrenberg) D. Mann
Abundant 2,10
Sellaphora laevissima (Kützing) D. Mann
Common 2,5,8,14
Sellaphora rectangularis (Gregory) Lange‑Bertalot and Metzeltin
Common 4,5,7,8,9

Stauroneis acuta W. Smith
Common 2,8,14
Stauroneis cf. gracilior Reichardt
Common 2,4,13,14
Stauroneis javanica (Grunow) Cleve
Rare 2,14
Stauroneis kriegeri Patrick
Common 4,7,8,9
Stauroneis phoenicenteron (Nitzsch) Ehrenberg
Abundant 1,2,8,9,10,13
Stauroneis phoenicenteron f. gracilis (Ehrenberg) Hustedt
Common 2,4
Stauroneis phoenicenteron var. brunii (Peragallo and Héribaud) Voigt
Common 2,8,13,14
Stauroneis smithii Grunow
Very Rare 4

Staurosira construens Ehrenberg
Rare 5,7
Staurosira construens var. binodis (Ehrenberg) Hamilton
Rare 5,7,14
Staurosira martyi (Héribaud) Lange‑Bertalot
Common 2,9

Stenopterobia sigmatella (Gregory) R. Ross in Hartley
Very Rare 4

Stephanodiscus neoastraea Håkansson and Hickel13
Stephanodiscus rotula (Kützing) Hendey
Abundant 1,2,8,9,10,13

Surirella bifrons Ehrenberg14
Common 2,13,14
Surirella biseriata Brébisson in Brébisson and Godey
Common 2
Surirella elegans Ehrenberg
Rare 13
Surirella linearis W. Smith
Rare 8
Surirella turgida W. Smith
Rare 1,5,14

Synedra capitata Ehrenberg15
Common 13
Synedra ulna (Nitzsch) Ehrenberg
Common 5,13
Synedra ulna var. oxyrhyncus (Kützing) Van Heurck
Common 2

Tabellaria flocculosa (Roth) Kützing16
Abundant 2,4

C. Source Materials
1. Toome Bridge, California Academy of Sciences, sample 612621, identifications by Robert I. Firth.
2. Toome Bridge, Kemp sample 823B, ex F. Monson, medium fraction. Slide FF-1.
3. Toome Bridge, antique nineteenth century mount by WM, 136. Ex F. C. Wise collection. Slide FF-8.
4. Toome Bridge, sample mounted by Robert Pettigrew, Jr., 1888. Ex F. C. Wise collection. Slide FF-9.
5. Toome Bridge, antique nineteenth century mount by J. Long, ex F. C. Wise collection. Slide FF-10.
6. Portglenone, Kemp sample 761R. Slide FF-23.
7. Ballyscullan, Kemp sample 278R, ex B. Hartley 411, light fraction. (Ballyscullan is the name of a bog on the east side of Lough Beg, north of Toome.) Slide FF-24.
8. Ballyscullan, Kemp sample 279R, ex B. Hartley 411, heavy fraction. Slide FF-25.
9. Toome Bridge, Kemp sample 822B, ex F. Monson. Slide FF-27.
10. Toome Bridge, Kemp sample 824B, ex F. Monson. Slide FF-28.
11. Toome Bridge, Kemp sample 929R, ex B. Hartley 2844. Slightly contaminated with marine material. Slide FF-29.
12. Toome Bridge, Kemp sample 470R. Slide FF-30.
13. Toome Bridge, Kemp sample 090R. Slide FF-31.
14. Toome Bridge, Kemp sample 744B. Slide FF-32.


1. Cf. http://doi.wiley.com/10.1002/jqs.816 for details.
2. This species may belong in the genus Eucocconeis.
3. Frustulia copulata Kützing 1833 is a synonym of Amphora libyca Ehrenberg 1840. Which name is correct seems to be a matter of opinion: the Atlas of British Diatoms and the ANSP Database use the former, the European Diatom Database and ADIAC Database use the latter, and the Great Lakes Diatom Checklist uses A. ovalis var. affinis (Kützing) Van Heurck ex DeToni.
4. The synonymy of Navicula ventricosa Ehrenberg 1830 and Navicula silicula Ehrenberg 1839 was first pointed out by Ehrenberg himself, in 1854. Ruth Patrick has argued that priority must be given to the former name, a policy that I have followed here. The latter name remains current in Europe.
5. This species is rare in my material, appearing only as a few fragments on one slide.
6. Listed as C. comta in Version 1 of this list. Håkansson has shown that C. comta is a synonym of C. radiosa. More recently, Hedy Kling has shown in her M.Sc. Thesis (University of Manitoba, 1997) that C. radiosa and C. bodanica cannot be distinguished morphologically, at least in North America, the putative character differences between them being largely attributable to negative allometry (due to the size reduction that characterizes the life cycle of any diatom population). Hence, all of these forms presumably belong to a single, highly plastic species. I have here used the name C. radiosa, until this taxonomic mess gets sorted out.
7. Listed as C. inaequalis in Version 1 of this list. C. ehrenbergii seems to be the currently accepted name, as the basionym for C. inaequalis was apparently not validly published. The Atlas of British Diatoms and Great Lakes Diatom Checklist, however, continue to use the former name.
8. This species has an isolated punctum on the dorsal side of the central area. However, several recently-described species of Encyonema have such a punctum, and I am not certain that this identification is correct.
9. Also known as Frustulia rhomboides var. amphipleuroides (Grunow) Cleve.
10. This Mastogloia species is quite distinctive, but I am thus far unable to place it.
11. Robert I. Firth reported both P. stomatophora and P. stomatophoroides from Toome Bridge samples. I have seen neither, although the former is abundant in numerous diatomites that I have seen from northern Great Britain.
12. The type locality for this variety is diatomite from the Lower Bann Valley, i.e., the Toome Bridge deposits. When the species elginensis was moved from Navicula to Placoneis, however, this variety was "stranded", as the name given here was never published, to the best of my knowledge. It is an interesting question as to whether the name is warranted: this variety is always smaller than the nominate variety in my material, and may represent simple allometric variation. Further study of P. elginensis populations will undoubtedly clarify the matter.
13. I am currently unable to distinguish between the two Stephanodiscus species. I have simply lumped them together for the abundance estimate.
14. This is the form with protracted ends, conforming very closely to Krammer and Lange-Bertalot, Süsswasserflora von Mitteleuropa 2/2, Tafel 146, fig. 3.
15. Krammer and Lange-Bertalot, in Süsswasserflora von Mitteleuropa 2/1, merged the genus Synedra with Fragilaria. Most workers still maintain the two genera, however, even though they admit that there is little taxonomic validity in doing so. A consequence of the merger is that, since the specific epithet capitata is preoccupied in Fragilaria, if this species appears in that genus it must bear the next available name, which is Fragilaria dilatata(Brébisson) Lange-Bertalot.
16. Representatives of the genus Tabellaria are abundant in Toome Bridge samples. Some are clearly T. flocculosa, having a median inflation that is considerably wider than the poles. However, both this species and others produce forms in which the median inflation is of roughly the same width as the poles. Hence, the number of species present is not clear to me; although most species are distinguishable in girdle view, most methods of cleaning fossil samples result in valves that appear only in valve view, with very rare exceptions.