Biodiversity & Conservation

LR.FLR.Lic.YG

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
(View Benchmark)
Removal of the substratum would result in loss of the lichen flora and its associated fauna and an intolerance of high has been recorded. Recovery would depend on weathering and recolonization of the substratum followed by growth of the lichen fauna. Therefore, a recoverability of very low has been recorded (see additional information below).
Smothering
(View Benchmark)
Fletcher (1980) noted that littoral lichens were eliminated by silt deposition. But most supralittoral species are unlikely to be smothered by sediment. Smothering by wind blown sediment and dusts may occur on sloping surfaces. Smith (1968) noted that Xanthoria sp. survived when smothered by weathered oil in the splash zone, and Crump & Moore (1997) noted that Verrucaria maura and Caloplaca marina survived for 10 months under weathered oil. No information on the effects of smothering on the invertebrate fauna was found, although smothering by oil is probably detrimental. Overall, smothering will probably reduce photosynthesis and growth rates of lichens. However, the biotope will probably survive and an intolerance of low has been recorded.
Increase in suspended sediment
(View Benchmark)
Supralittoral lichens are not immersed, receiving only wave splash and spray, and are unlikely to be affected by changes in suspended sediment levels. Therefore, not relevant has been recorded. Deposition of wind blown sediment or industrial dusts may occur on sloping surfaces but no information on the potential effects of dusts was found.
Decrease in suspended sediment
(View Benchmark)
Supralittoral lichens are not immersed, receiving only wave splash and spray, and are unlikely to be affected by changes in suspended sediment levels. Therefore, not relevant has been recorded.
Desiccation
(View Benchmark)
The levels of moisture and relative duration of wet and dry periods are the most important factors controlling vertical zonation in supralittoral lichens. Water is supplied by tidal inundation, wave splash or sea spray at the bottom of the shore but by rainfall and runoff at the top of the shore. Rates of evaporation and hence desiccation is dependant of the slope and drainage of the shore, the rock type and its porosity, temperature and hence insolation and aspect, and wind exposure. Any activity that changes the exposure of the shore to wind, wave, rain or sunlight is likely to affect supralittoral communities.
  • The xeric-supralittoral receives the least amount of water from sea or land together with the greatest degree of evaporation and is therefore the driest and most drought prone zone (Fletcher, 1980)
  • The number of lichen species decreases on wind exposed shores, due to the loss of foliose species (e.g. Parmelia sp.), xeric-supralittoral and terrestrial lichens, and total lichen cover is reduced.
  • Wind related desiccation may restrict lichens to damp crevices and recesses.
  • Supralittoral lichens take up water faster than it is lost, unlike their littoral counterparts (Fletcher, 1980).
  • Growth form and thallus structure affects desiccation rates with crustose and closely appressed forms having lower rates of water loss (Fletcher, 1980).
  • Supralittoral lichens were reported to respire at 5-20% water saturation and photosynthesize at 10-30% although littoral species required 30-50% to respire and greater than 40% water saturation to photosynthesize (for further details see Fletcher, 1980).
  • Exposure to 21h drought and 3h submersion for 14 days in supralittoral lichens broke down their symbiosis resulting in liberation of the microalgal symbiont. Fletcher (1980) concluded that the lichen symbiosis required a suitable balance of dry and wet periods for each species.
  • The zonation of different species of acarid mites is partly determined by their tolerance to desiccation (Pugh & King, 1985b) so that the acarid species composition will probably change, with an increase in the number of terrestrial species.
  • Tardigrades are highly tolerant of desiccation and able to undergo anahydrobiosis to form resistant, dormant 'tuns' (Kinchin, 1994) and are probably tolerant of desiccation at the benchmark level.
Although supralittoral lichens are probably highly tolerant of high levels of desiccation when compared to littoral species, each species probably lives within a narrow range of environmental conditions and are intolerant of changes in the moisture levels and desiccation (Jones et al., 1974; Holt et al., 1995). Therefore, an increase in desiccation at the benchmark level is likely to increase the extent of the xeric-supralittoral to the detriment of the mesic or lower terrestrial zones but also potentially reduce the species richness and abundance of lichens in the xeric zone, restricting lichen species to damp crevices. An increase in desiccation is likely to adversely affect species richness and change to species composition of the lichen communities and the invertebrate fauna. Therefore, an intolerance of intermediate has been recorded. Recovery is likely to be slow (see additional information below).
Increase in emergence regime
(View Benchmark)
An increase in emergence will reduce the inundation of the mesic and submesic supralittoral and littoral fringe, and may reduce the upper extent of sea spray, especially on sheltered shores. Johannesson (1989) attributed the zone of bare rock (devoid of marine and terrestrial life) found on non-tidal rocky shores in Sweden, to prolonged periods of submergence and emergence due to changes in tidal height by atmospheric pressure.

The classification of acarid mites into maritime, nomadic or terrestrial species is partly related to their response to inundation by seawater (Pugh & King, 1985b). An increase in emergence is likely to favour more terrestrial and nomadic species.

Overall, an increase in emergence could potentially allow the mesic and xeric supralittoral zones to increase in extent down the shore, while halophilic terrestrial lichens may colonize the upper supralittoral. However, in one year (see benchmark) little difference is likely to be observed since lichens grow and colonize slowly, and the effects only manifest themselves if the change in emergence is prolonged. Therefore, the supralittoral lichen communities may benefit from a long term increase in emergence.
Decrease in emergence regime
(View Benchmark)
A decrease in emergence will increase the inundation of the lower supralittoral (mesic and submesic zones) and may increase the effects of wave splash further up the shore. Fletcher (1980) reported that 35 days submergence resulted in a breakdown of the symbiosis between lichenicolous fungi and the microalgae in supralittoral lichens. In a one year period (see benchmark) the mesic and submesic species are likely to be reduced in extent, while the littoral fringe communities are likely to increase in extent. If the decrease in emergence is prolonged the upper limit of the mesic and submesic zones is likely to increase while the extent of the xeric will decrease. The classification of acarid mites into maritime, nomadic or terrestrial species is partly related to their response to inundation by seawater (Pugh & King, 1985b). A decrease in emergence is likely to favour more maritime species. Overall, the extent of the biotope and its species richness is likely to decrease in the short term and an intolerance of intermediate has been recorded. Recoverability is likely to be moderate (see additional information below).
Increase in water flow rate
(View Benchmark)
The supralittoral is unlikely to be affected by changes in water flow.
Decrease in water flow rate
(View Benchmark)
The supralittoral is unlikely to be affected by changes in water flow.
Increase in temperature
(View Benchmark)
Supralittoral lichens are exposed to extremes of temperature from hot, dry summers to cold, frosty winters. The characterizing lichen species are widely distributed around Britain and Ireland and unlikely to be adversely affected by changes in temperature at the benchmark level. Therefore, 'not sensitive' has been recorded. However, an increase in temperature is likely to increase the risk of desiccation (see above).
Decrease in temperature
(View Benchmark)
Supralittoral lichens are exposed to extremes of temperature from hot, dry summers to cold, frosty winters. The characterizing lichen species are widely distributed around Britain and Ireland and unlikely to be adversely affected by changes in temperature at the benchmark level. However, a decrease in temperature is likely to decrease the risk of desiccation (see above) and increase the average humidity of the shore. Fletcher (1980) suggested that the lower average temperatures and increased rainfall of the shores of western Scotland resulted in a reduced xeric-supralittoral zone. Overall, the biotope will remain, and although the relative extent of the supralittoral lichen zones and species composition is likely to change in the long term, not sensitive has been recorded at the benchmark level.
Increase in turbidity
(View Benchmark)
The turbidity of sea water is not relevant in the supralittoral but lichens are affected by changes in light intensity (see additional information below).
Decrease in turbidity
(View Benchmark)
The turbidity of sea water is not relevant in the supralittoral but lichens are affected by changes in light intensity (see additional information below).
Increase in wave exposure
(View Benchmark)
The biotope has been recorded from very wave exposed to wave sheltered environments. Increased wave exposure raises the height of the lichen zones, reduces the number of species present and the overall lichen cover, and reduces the lower limit of terrestrial vegetation (Fletcher, 1973b,1980) due to an increase in the amount of wave splash and sea spray. As a result, the mesic and xeric zones increase in vertical extent. Increased wave action may remove some species, e.g. Xanthoria parietina which becomes restricted to fissures and crevices on wave exposed shores. On very wave exposed shores, littoral fringe and mesic-supralittoral lichen species may extend into the terrestrial zone. Overall, an increase in wave exposure is likely increase the extent of the biotope, although species richness will decline, and not sensitive* has been recorded. The extent of the area affected by sea spray (seawater droplets and salt) is also affected by wind exposure (see additional information below). It should be noted that the effects will probably take more than a year (see benchmark) to become observable.
Decrease in wave exposure
(View Benchmark)
Lichen cover increases on shores sheltered from wave or wind generated sea spray but the vertical extent of the supralittoral zones are much reduced in extent due to downward penetration of terrestrial vegetation. The mesic-supralittoral is poorly represented on sheltered shores (Fletcher, 1973b, 1980). Therefore, a decrease in wave exposure is likely to reduce the extent of the supralittoral lichens zone, although the abundance of individual species present may increase, and an intolerance of intermediate has been recorded. It should be noted that the effects will probably take more than a year (see benchmark) to become observable.
Noise
(View Benchmark)
Lichens are not known to respond to noise or vibration. The associated acarid mite, insect and tardigrade fauna may respond to local vibrations caused by potential predators but are unlikely to be affected by the types of noise represented by the benchmark.
Visual Presence
(View Benchmark)
Lichens have no known visual receptors, and the associated fauna probably have very limited visual acuity. Therefore, the biotope is unlikely to be affected by visual presence.
Abrasion & physical disturbance
(View Benchmark)
The biotope is susceptible to trampling by birds (in heavily populated sites), animals and man, animal rubbing and the physical abrasion caused by wind.
  • Physical abrasion by wind may discourage large foliose and fructicose lichens
  • Fletcher (1980) noted that large specimens of lichens, e.g. Ramalina siliquosa, were only found on vertical rocks inaccessible to animals, including man.
  • James & Syratt (1987) noted that rubbing by animals (e.g. sheep) damaged lichens resulting in loss of parts of some thalli and loss of Ramalina siliquosa at some sites, while it showed signs of regeneration at some sites.
  • Trampling damage is greatest when the thallus is wet, causing it too peel from the surface, while when dry, some fragments are likely to remain to propagate the lichen (Fletcher, 1980).
  • Physical disturbance of the lichen flora or substratum may reduce species richness and favour more rapid growing, disturbance tolerant species, e.g. Lecanora dispersa, Candelariella vitellina and Rinodina gennerii (Fletcher, 1980)
  • Extreme physical abrasion due to high pressure water cleaning techniques (used to clear oil after spills), damaged lichens even at low pressures, especially Ramalina siliquosa, Xanthoria sp. and Caloplaca marina, and removed all supralittoral lichens at high pressures (Crump & Moore, 1997; Menot et al., 1998).
Overall, supralittoral lichens appear to be intolerant of physical abrasion. Animal trampling and rubbing are likely to remove a proportion of lichen thalli in the short term, and alter the lichen communities in the long term. Therefore, an intolerance of intermediate has been recorded. Recovery is likely to be slow (see additional information below).
Displacement
(View Benchmark)
Crustose and foliose supralittoral lichens are closely adpressed to their substratum and their removal would probably be destructive. Fructicose lichens may survive removal but unattached specimens would probably not survive being transported to unsuitable habitats by the wind. No information on the re-attachment of lichens was found but it is presumed to be unlikely. Fragmentation of the thallus during displacement may help to disperse spores and asexual propagules. Overall, the lichens would probably be destroyed during displacement and lost. The many species of the associated invertebrate fauna would probably migrate to other suitable substrata. Therefore, the biotope would be lost, and an intolerance of high has been recorded. Recovery is likely to be low (see additional information below).

Chemical Factors

Synthetic compound contamination
(View Benchmark)
Dispersants and detergents
Several studies have documented the effects of oil spills on supralittoral lichen communities, although in many cases is difficult to separate the effects of oiling from the effects of dispersants. Most studies concluded that the decontamination methods, (including dispersants) were more toxic to lichens than the oil itself.
  • Ranwell (1968) reported 19 species of lichens that were killed by oil or dispersants, including the characterizing species Lichina sp., Caloplaca marina, Caloplaca thallincola, Tephromela atra, Ochrolechia parella, Ramalina siliquosa, and Xanthoria parietina.
  • In Bantry Bay, walls washed with the detergent (dispersant ) BP1100X were very clean. Although crustose species were little affected, Caloplaca citrina had turned green, Physcia sp. and other foliose species were absent and Xanthoria parietina thalli had changed colour and were peeling off (Cullinane et al., 1975).
  • Laboratory treatment (24hr) of lichens with dispersants resulted in discoloration, loss of chlorophyll and algal cells in several species (Brown, 1974).
  • Heavy use of dispersants in Caerthillian Cove, after the Torrey Canyon oil spill, was reported to have 'annihilated' the lichen flora, and subsequent recolonization did not begin until 7 years later (Brown, 1974).
Lichen communities were also reported to be affected by trampling during clean up and to be highly intolerant of high pressure spray washing techniques (see abrasion above) (Ranwell, 1968; Cullinane et al., 1975; Crump & Moore, 1997; Menot et al., 1998).

Air pollution
The effects of air pollutants on terrestrial lichens and their use as indicator species has been studied extensively (Holt et al., 1995) although few studies refer to maritime species (see reviews and bibliographies by Henderson (1999), Richardson (1992), and NHM (2002)). Fletcher (1980) suggested that supralittoral lichens were more intolerant of air pollution than littoral species, and had disappeared in the Clyde estuary and north eastern England. Studies of terrestrial locations suggest that Xanthoria parietina was less intolerant of air pollution than other lichens, although germination and growth were inhibited (Holt et al., 1995; Dobson, 2000). Jones et al. (1974) attributed dying Ramalina siliquosa, Verrucaria maura, Caloplaca marina and Lichina pygmaea, and a reduced cover of Xanthoria parietina in Bull Bay, Anglesey to fumes from a nearby petroleum plant, which were also reported to make working on the shore unpleasant.

Overall, although lichen species sensitivities vary, many of the characterizing species are intolerant of atmospheric pollution and synthetic chemicals. Therefore, an intolerance of high has been recorded. Recovery is likely to be very low (see additional information below).
Heavy metal contamination
(View Benchmark)
Lichens are well known indicators of heavy metals in the environment, especially iron Seashore lichens often indicate environmental concentrations of heavy metals or accumulate them, frequently to very high levels (Fletcher, 1980). The accumulation of high levels of heavy metals may deter grazers (Gerson & Seaward, 1977). For example, Verrucaria maura was reported to accumulate Fe to 2.5 million fold over the concentration in seawater, and Zn by a factor of 8000. Some species accumulate lead to 100ppm and cadmium to 2ppm of thallus dry weight (Fletcher, 1980). Heavy metals may be derived from rainfall, and dust as well as seawater (Fletcher, 1980). Gerson & Seaward (1977) noted that accumulated heavy metals could potentially accumulate up lichen based food webs, e.g. the lichen to caribou to man food chain in Alaska. However, no information on bioaccumulation through supralittoral communities was found. Overall, the ability of lichen to accumulate heavy metals to such high levels suggests a high tolerance to the heavy metal ions studied. Therefore, not sensitive has been recorded.
Hydrocarbon contamination
(View Benchmark)
Several studies have documented the effects of oil spills on supralittoral lichen communities, although in many cases is difficult to separate the effects of oiling from the effects of dispersants.
  • Ranwell (1968) reported 19 species of lichens that were killed by oil or dispersants, including the characterizing species Lichina sp., Caloplaca marina, Caloplaca thallincola, Tephromela atra, Ochrolechia parella, Ramalina siliquosa, and Xanthoria parietina.
  • Smith (1968) reported that Xanthoria parietina grew even under a covering of weathered oil, while Crump & Moore (1997) noted that Caloplaca marina survived 10 months under weathered oil.
  • Oil inundation caused discoloration of the thallus (e.g. Xanthoria parietina became dark brown), especially of the fruiting bodies, or bleaching of the thallus, while brittle tough thalli of Ramalina siliquosa and Lichina pygmaea became flaccid, soft and slimy (Cullinane et al., 1975).
  • In Bantry Bay, Cullinane et al. (1975) reported that a spill of crude oil affected fructicose species most of all, crustose species the least, while foliose species were affected at a intermediary level. Gelatinous and crustose lichens absorbed the oil and were removed from the substratum. Xanthoria parietina was the most severely affected species, while Ramalina siliquosa, Lichina pygmaea and Dermatocarpon miniatum were obviously affected (Cullinane et al., 1975). Cullinane et al. (1975) listed 9 species of lichen damaged by oil.
  • Crump & Moore (1997) reported that oiling with crude oil followed by fuel oil from the Sea Empress spill, severely damaged Ramalina siliquosa and Xanthoria parietina, resulting in necrosis, bleaching and peeling from the substratum. Almost all the Xanthoria parietina surviving after the spill in September 1996 had died by February 1997. Caloplaca thallincola was also damaged.
Overall, several of the characterizing species are probably highly intolerant of oiling, while others demonstrate sub-lethal effects and are likely to be damaged by oiling, depending on the type and weathering of the oil. Oiling is likely to have adverse effects of the invertebrate fauna, either through toxicity or smothering, and especially through loss of the lichen habitat. Therefore, an intolerance of high has been recorded. Recovery is likely to be very slow (see additional information below).
Radionuclide contamination
(View Benchmark)
Lichens have also been reported to accumulate radionuclides in a similar manner to other heavy metals (see above) (Gerson & Seaward, 1977; Fletcher, 1980). Radionuclides could potentially accumulate up food webs based on lichen species, however, no further information was found.
Changes in nutrient levels
(View Benchmark)
Nutrient levels are a determining factor in supralittoral lichen zonation. Nutrient-rich, acid runoff from terrestrial habitats influences the top of the supralittoral while saline, basic conditions dominate at the bottom of the shore. Heavy bird manuring can result in loss of the xeric-supralittoral to submesic lichen species such as Xanthoria parietina, Xanthoria candelaria and Caloplaca verruculifera (Fletcher, 1980). Wootton (1991) reported that the presence of guano on the shores of Washington State, resulted in loss of grey lichens allowing Caloplaca marina and Xanthoria parietina to colonize further up the shore (Wootton, 1991; Holt et al., 1995). The lichen Aspicilia leprosescens is exclusively associated with bird perches on siliceous rocks (Fletcher, 1980). Large populations of the lichen Candelariella vitellina on the shore are indicative of nutrient enrichment (Fletcher, 1980; Holt et al., 1995). Siliceous rocks are nutrient poor and dominated by grey lichens e.g. Ramalina siliquosa. It is likely that an increase in nutrients may promote lichen communities of more nutrient rich calcareous rocks, or halophilic terrestrial lichen species.

Nutrient enrichment by bird manuring is likely to result in an increase in 'orange belt' submesic species but the biotope will still be identifiable. An increase in nutrient runoff from the terrestrial zone, e.g. due to agricultural fertilizer and sprays may allow the halophilic terrestrial lichens species or species typical of calcareous rocks to colonize further down the shore, reducing the extent of the supralittoral lichen zone. Therefore, an intolerance of intermediate has been recorded, albeit at low confidence. It should be noted that the effects will probably take more than a year (see benchmark) to become observable. Recovery is likely to be low (see additional information below).

Increase in salinity
(View Benchmark)
The mesic-supralittoral is the only supralittoral zone subject to direct inundation by seawater. The supralittoral is exposed to a harsh regime of fluctuating salt (ionic) concentration due to deposition of wave splash or sea spray, subsequent evaporation and increased concentration, and the freshwater influences of rain, dew and runoff. Fluctuations in salt concentration and saline influence are important determinants of supralittoral zonation (Fletcher, 1980) Therefore, an increase in saline influence, e.g. via increased sea spray deposition is likely to have similar effects to that of increased wave exposure, an increase in the height of supralittoral zones, especially the xeric, on the shore. Therefore, supralittoral lichen zones are likely to increase in extent, although it may take more than a year (see benchmark) for the effects to be observable.
Decrease in salinity
(View Benchmark)
A decrease in the extent of the biotope in estuaries is probably more related to the reduction of wave action and sea spray, and the lack of suitable substrata than a reduction in salinity itself. Increased freshwater runoff or rainfall is likely to allow halophilic terrestrial lichens and vegetation to colonize further down the shore, forming lichen communities similar to those of shaded shores. For example, Fletcher (1980) reported that the xeric-supralittoral zones was better represented in south west Britain and Ireland than western Scotland, where even wind exposed shores bear halophobic terrestrial species. Fletcher (1980) suggested that the increased rainfall and lower temperatures in western Scotland mitigated the effect of salinity and sea spray.

A reduction in saline influence is likely to allow more terrestrial species to colonize further down the shore, increasing species richness but reducing the extent of the biotope. Therefore, an intolerance of intermediate has been recorded. It may take more than a year (see benchmark) for the effects to be observable. Recovery is probably low (see additional information below).

Changes in oxygenation
(View Benchmark)
Lichen communities are exposed to the atmosphere and rarely inundated by seawater, even at the bottom of the supralittoral. Therefore, this biotope is unlikely to experience deoxygenating conditions.

Biological Factors

Introduction of microbial pathogens/parasites
(View Benchmark)
No information concerning the diseases or parasites of lichens was found.
Introduction of non-native species
(View Benchmark)
No information found
Extraction
(View Benchmark)
Lichens, e.g. Ochrolechia parella,have been collected in the past for the manufacture of dyes. Collection of lichens to prepare lichen-dyed tweed has largely stopped (Richardson & Young, 1977), however no information concerning the use of coastal lichens was found. Extraction of lichens will undoubtedly reduce their abundance but probably not the extent of the supralittoral zone. An intolerance of intermediate has been recorded at the benchmark level, while recoverability is likely to be low.

Additional information icon Additional information

Light and aspect
Aspect and hence light intensity and duration affect lichen communities primarily by affecting temperature and hence moisture levels. Sunny shores tend to be dominated by orange and white photophilic lichens while shaded shores are dominated by greyer, shade-loving lichen species (see distribution). The supralittoral zones are reduced in height on shaded shores and the xeric-supralittoral is replaced by terrestrial lichens, resulting in an increase in species richness. However, the extent of the biotope is likely to be markedly reduced by shading.

Wind exposure
Wind exposure carries sea spray up the shore and inland, influencing the height of the supralittoral and the extent of the maritime influence inland. Increased wind exposure will also increase the risk of desiccation. On wind or wave exposed shores the presence of spray forces the terrestrial zone up the shore and the gap is filled by xeric-supralittoral lichen communities (Fletcher, 1980). Terrestrial and xeric-supralittoral lichens may be absent from very wind exposed shores due to increased desiccation and physical wind abrasion. Wind sheltered shores exhibit lichen communities of sheltered shores with little sea spray (see wave exposure above).

Recoverability
Sexual spores and asexual propagules of lichens are probably widely dispersed by the wind and mobile invertebrates, while the microalgal symbionts are probably ubiquitous. The thallus of lichens often dies from the centre out, growth occurring at the margin edge. However, fragments of the remaining thallus continue to grow, often faster than in a large thallus. Nevertheless, lichen growth rates are low, rarely more than 0.5-1mm/year in crustose species while foliose species may grow up to 2-5mm/year. Cullinane et al. (1975) noted that many of the lichens lost due to an oil spill in Bantry Bay were probably 20-50 years old based on their size, and life spans of lichens have been estimated to be 100 years or more (Jones et al., 1974). Given their slow growth rates lichens will probably take many years to recover their original cover, possibly taking up to 20 years.

Fletcher (1980) suggested that newly exposed substratum needs to be modified by weathering and that initiation of new thallus is thought to take several years. Crump & Moore (1997) observed that lichens had not colonized experimentally cleared substrata within 12 months. Brown (1974) reported that recolonization of substrata within Caerthillian Cove, Cornwall, which was heavily affected by oil and dispersants after the Torrey Canyon oil spill, took 7 years to begin.

Overall, although mobile invertebrate fauna will probably recolonize rapidly, recovery of lichens communities from damage will probably take many years. In heavily damaged areas, the prolonged recolonization period and subsequent slow growth is likely to take a very long time and recovery rates are likely to be extremely slow, probably in excess of ten years (Holt et al., 1995).

This review can be cited as follows:

Tyler-Walters, H. 2002. Yellow and grey lichens on supralittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 01/08/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=96&code=2004>