This comprises ten lists of plants using the Ellenberg scale for salt tolerance, which goes from 9, the maximum possible salt tolerance to just 1 where the plants are just slightly tolerant to low concentrations of salt. The remaining plants exhibit no tolerance of salt and are accorded the Ellenberg value of 0 for 'zero' salt-tolerance. This last, salt-intolerant, list is by far the longest.
• Salt Tolerance 9. Species of extremely saline conditions, in sites where sea water evaporates, precipitating salt (Salicornia europaea agg.; these could equally well be treated as species of the lower marsh)
• Salt Tolerance 8. Species more or less permanently inundated in sea water (Zostera spp.)
• Salt Tolerance 7. Species of lower saltmarsh (Spartina anglica, Suaeda maritima)
• Salt Tolerance 6. Species of mid-level saltmarsh (Atriplex portulacoides, Cochlearia anglica, Limonium vulgare)
• Salt Tolerance 5. Species of the upper edge of saltmarsh, where not inundated by all tides (includes obligate halophytes of cliffs receiving regular salt spray) (Aster tripolium, Crithmum maritimum, Puccinellia maritima, Suaeda vera)
• Salt Tolerance 4. Species of salt meadows and upper saltmarsh, subject to at most only very occasional tidal inundation (includes species of brackish conditions, i.e. of consistent but low salinity) (Atriplex littoralis, Elytrigia atherica, Glaux maritima, Triglochin maritimum)
• Salt Tolerance 3. Species most common in coastal sites but regularly present in freshwater or on non-saline soils inland (includes strictly coastal species occurring in sites such as cliff crevices and sand dunes that are not obviously salt-affected) (Cakile maritima, Cochlearia officinalis, Juncus gerardii, Spergularia rupicola)
• Salt Tolerance 2. Species occurring in both saline and non-saline situations, for which saline habitats are not strongly predominant (Atriplex prostrata, Elytrigia repens, Phragmites australis, Rumex crispus)
• Salt Tolerance 1. Slightly salt-tolerant species, rare to occasional on saline soils but capable of persisting in the present of salt (includes dune and dune-slack species where the ground water is fresh but where some inputs of salt spray are likely) (Calystegia sepium, Chenopodium album, Oenanthe crocata, Sedum anglicum)
• Salt Tolerance 0. Absent from saline sites; if in coastal situations, only accidental and non-persistent if subjected to saline spray or water (85% of the flora).
Ellenberg Salt-tolerance scales 1-3 include plants which would rather be in non-salty areas where they would normally grow much better and larger; they only inhabit these slightly salty areas because there is no competition from the zero-salt-tolerant plants where they would rather be if only it weren't so overcrowded with these salt-intolerant plants. They have learned to cope with a little salt in order to enjoy a less crowded landscape. Some plants in these categories can also be found well inland in non-salty areas where they will grow better. Salt-tolerance costs the plants energy, and if the plant can also live in saltless areas, then it need not expend energy sequestering salt in special compartments or pumping salt out from itself.
The salinity of sea-water is normally 3.5%, but in restricted seas can be much higher. It must be remembered that the salinity of the ground further away from the sea diminishes due to two main factors. The distance sea ground-water or sea-spray can reach, and the dilution caused by rainwater or rain ground-water. Naturally, this varies week to week.
N.B. 'Salt' does not necessarily imply only NaCl, but can also include many other components of sea water. Here is a list in decreasing amounts, listing just the ions and anions followed by their concentrations in mol/kg: H2O 53.6, Cl- 0.546, Na+ 0.469, Mg2+ 0.0528, (SO4)2- 0.0282, Ca2+ 0.0103, K+ 0.0102, Br- 0.000844, B 0.000416, Sr2+ 0.000091, F- 0.000068.
2 - Sea Water Composition (and plants)