A Coded List of Freshwater Algae of the British Isles
Second Edition
The 8-digit Code
Allocation of digits in the 8-digit Code
The eight digits are allocated as follows:
| Digits 1 and 2 | Coding the phylum or one or more major subgroups within a phylum (see the section Sequence of taxa used in the Code).
e.g. 03 = Rhodophyta (the red algae) The Chlorococcales include more than 99 genera, so these have been split between 17 and 18. However, all the known photosynthetic forms are included in 17, so there is likely to be little need to use the 18 series. |
| Digits 3 and 4 | Coding the genus
e.g. within the red algae, 02 = Bangia |
| Digits 5, 6 and 7 | Coding the species (The 2-digit code used previously is inadequate for the number of species in genera such as Navicula and Cosmarium.) (see the section Coding of species width categories).
e.g. within the genus Bangia, 001 = atropurpurea |
| Digit 8 | Coding varieties or other infraspecific taxa (see the section Digit 8 in the Code). |
Use of the digits in the Code
In all cases, all of the eight digits must be used. Where it is impossible to identify the organism fully, then zeros must be added for the missing taxonomic level.
e.g. 03020000 = Bangia sp.
The final 0 must be included for every species unless the organism is recognized as belonging to a particular infraspecific taxon such as a variety. The numbering for this starts at 2 (rather than 1). This is to permit researchers to use 1 for the final number if they want to stress that the organism corresponds closely to the original description of the species, rather than one of the named varieties or forms. Where there are a number of infraspecific taxa, the use of 0 for the final number means that the organism could belong to any of them.
It is proposed that further additions to the flora will be added at the end of lists of species within genera or genera within major taxonomic groups: the sequence will no longer be strictly alphabetical. This already occurs with one diatom genus (Kraskella) and three varieties of a species of desmid (Staurastrum anatinum).
Sequence of taxa used in the Code
Listed below are the first 2 digits of the Code and the major taxa they represent.
| 01 | Cyanophyta |
| 02 | Prochlorophyta |
| 03 | Rhodophyta |
| 04 | Euglenophyta |
| 05 | Cryptophyta |
| 06 | Pyrrophyta / Dinophyceae |
| 07 | Raphidophyta |
| 08 | Haptophyta |
| 09 | Chrysophyta |
| 10 | Xanthophyta |
| 11 | Eustigmatophyta |
| 12 | Bacillariophyta (centric forms) |
| 13 | Bacillariophyta (pennate forms) |
| 14 | Phaeophyta |
| 15 | Prasinophyta |
| 16 | Chlorophyta / Volvocales, Tetrasporales |
| 17 | Chlorophyta / Chlorococcales |
| 18 | Chlorophyta / Chlorococcales (con.) |
| 19 | Chlorophyta / Oedogoniales |
| 20 | Chlorophyta / Cladophorales |
| 21 | Chlorophyta / Ulvales |
| 22 | Chlorophyta / Trentepohliales |
| 23 | Chlorophyta / Siphonales |
| 24 | Chlorophyta / Chaetophorales, Chlorosarcinales, Ctenocladales, Microsporales, Prasiolales, Ulotrichales |
| 25 | Chlorophyta / Klebsormidiales |
| 26 | Chlorophyta / Coleochaetales |
| 27 | Conjugatophyta |
| 28 | Charophyta |
| 29 | Glaucophyta |
When coding unknown forms the full eight digit code must be used.
e.g. 03000000 = Rhodophyta
Genera (digits 3 and 4) are listed alphabetically within each major taxon and species (digits 5, 6 and 7) alphabetically within each genus. Infraspecific taxa are listed first with varieties listed alphabetically and then with any lower level taxa listed alphabetically.
Coding of species width categories
It is recommended that records for genera where it is especially difficult to identify the species should be coded according to their width category. This poses a risk that some organisms may be recorded at one time by their width category and at other times by their specific name. However, this seems a worthwhile risk for many types of study; it is up to the user to consider this possibility when analyzing data. The same categories are recommended for use with all groups, though in only one genus of the blue-green algae are all the categories potentially applicable.
The suggested width categories are as follows:
| Category | Width |
| 1 | ≤ 1µm |
| 2 | > 1 ≤ 2µm |
| 3 | > 2 ≤ 4µm |
| 4 | > 4 ≤ 8µm |
| 5 | > 8 ≤ 16µm |
| 6 | > 16 ≤ 32µm |
| 7 | > 32 ≤ 64µm |
| 8 | > 64 ≤ 128µm |
| 9 | > 128µm |
The genera where its use should be considered in particular are:
| Cyanophyta | Oscillatoria, Lyngbya, Phormidium, Tolypothrix (in sheathed forms, apply to trichome, not whole filament) |
| Oedogoniales | Oedogonium |
| Chaetophorales | Microspora, Ulothrix |
| Conjugatophyta | Mougeotia, Spirogyra, Zygnema |
The procedure for coding is to use phylum and genus digits as usual, but to code the species as 00 and follow this with the relevant numerical code for width category.
e.g. 27340007 = Spirogyra sp. > 32 ≤ 64 µm wide
Digit 8 in the Code
One major taxonomic group, the Chlorococcales, contains more than 99 genera, so different 2-digit numbers are required for these. However, the second set only includes taxa which are colourless or whose status in the British Isles is very rare or doubtful, so will probably seldom be needed (see below). The allocation of three digits for species means that there should always be enough numbers (999) within a genus. The allocation of only one digit (digit 8) for infraspecific taxa may eventually prove inadequate, but it did not seem justified to increase the number of digits to cover this rare occurrence. The number of infraspecific taxa so far does not exceed the maximum of eight possible within the present system for any species.
No infraspecific taxon has been included with the same name as the specific name. This has meant the omission of a few such infraspecific taxa for the diatoms and the desmids (latter mostly by J. Ruzicka). However, in the 8th digit, the number 1 has been left vacant and this should be used if it is needed to emphasize that the organism corresponds closely to the type, as opposed to one of the other infraspecific taxa.
The combination of genus, no species name and a final number to indicate width could be extended to further genera. However, it seems unwise to encourage its use, unless the genus is large and recognition to the species level is difficult. These width categories are often not the same as those in the 1978 Coded List, where different numbers were used for different genera in order to permit the use of narrow ranges of filament width.
