Seepages are very small, flowing waterbodies. They are characterised by generally slow rates of flow, and by being extremely shallow, sometimes no more than a film of water over the substrate. This means that they are most often associated with the uppermost sections of waterbodies, being transitional to streams and rivers as they gather water lower in the catchment. They are also very often derived from springs.
The seepage fidelity scores originate from a review of the invertebrate fauna of seepage systems in England (Boyce 2002). Five main types of seepage habitat have been identified in England: slumping cliff seepages; stable cliff seepages; woodland seepages; acid-neutral seepages; calcareous seepages.
Invertebrates showing a strong fidelity for seepages are categorised as obligates, specialists or generalists:
- Grade A – seepage obligates: species that are exclusive inhabitants of seepages and their margins, with almost all of their British records referring to these habitats.
- Grade B – seepage specialists: species that are primarily found in seepages and their margins, but which occasionally occur in other situations. Generally in excess of 75% of British records refer to these habitats.
- Grade C – seepage associates: species found in and around other types of running and shallow water, but which nonetheless have a strong association with seepages and their margins. Generally in excess of 50% of British records refer to these habitats.
Pantheon presents separate fidelity grades for each of the five seepage habitat types, to highlight links between the species and the different habitat types, but it should be noted that the fidelity grade assigned to each species refers to its fidelity to seepages as a whole, rather than to any individual seepage habitat type. This is because a number of the invertebrates graded are found in more than one of the seepage habitats discussed.
For more information see: Boyce, D.C. 2002. A review of seepage invertebrates in England. English Nature Research Report 452.