The Marine Life Information Network

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Loss of substratum would entail loss of the population of Mya arenaria.
Recovery is dependant on recolonization by juveniles, perhaps transported by bedload transport, and successful recruitment of spat. Strasser et al. (1999) noted that population densities in the Wadden Sea were patchy and dominated by particular year classes. Mya arenaria has a high fecundity and reproductive potential but larval supply is sporadic and juvenile mortality is high, so that although, large numbers of spat may settle annually, successful recruitment and hence recovery may take longer than a year. Beukema (1995) reported that a population of Mya arenaria in the Wadden Sea, drastically reduced by lugworm dredging took about 5 years to recover. Therefore a recovery of high has been recorded.

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

Emerson et al. (1990) examined smothering and burrowing of Mya arenaria after clam harvesting. Significant mortality (2 -60%) in small and large clams occurred only at burial depths of 50 cm or more in sandy substrates. However, they suggested that in mud clams buried under 25cm of sediment would almost certainly die. Dow & Wallace (1961) note that large mortalities in clam beds have resulted from smothering by blankets of algae (Ulva sp.) or mussels (Mytilus edulis). In addition clam beds have been lost due to smothering by 6 cm of sawdust, thin layers of eroded clay material, and shifting sand (moved by water flow or storms) in the intertidal. Therefore, Mya arenaria is probably of intermediate intolerance to smothering by 5cm of sediment (the benchmark level), although it should be noted that intolerance would also depend on the nature of the smothering material.
Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Newell & Hidu, (1986) point out that because adults occupy permanent burrows they are vulnerable to smothering as a result of e.g. coastal engineering works but they also point out that clams continue filtration even when suspended solid concentrations exceed 300mg/l. Grant & Thorpe (1991) noted that in short term exposures to suspended sediment between 0 -2000 mg/l resulted in reduced oxygen consumption and respiration with increasing sediment concentration, pseudofaeces production being initiated at 100-119 mg/l. This results in rejection of particulates as pseudofaeces and loss of energy as mucus. However, Mya arenaria was unable to obtain adequate nutrition at particle loads of 100-200 mg/l and metabolised protein. Grant & Thorpe (1991) suggested, therefore, that prolonged exposure to concentrations >100 mg/l for > 2 weeks would result in reduced condition and reduced growth, increased mortality and decline of the fishery. Therefore, an intolerance of intermediate to siltation has been recorded. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Desiccation

1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

The burrowing habit of Mya arenaria protects it from the risk of desiccation. However, juveniles, and adults removed from the sediment are likely to be highly intolerant of the effects of desiccation, especially as the siphons can not be enclosed in the shell, forcing the shell to gape. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Increased emergence will result in increased drainage of the sediment and reduced time for Mya arenaria to feed. High shore populations are likely to be most vulnerable. Overall increased emergence may reduce the extent of the population towards the top of the shore. However, given this species wide range of habitat preference decreased emergence is unlikely to adversely affect the population. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Changes in the water flow rate will affect the hydrodynamics of the shore, sediment grain size and distribution. Shifting sands and erosion result in the loss of soft-shell clam beds in the intertidal due to smothering (see above) or loss of intertidal habitat (Dow & Wallace, 1961). Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

Increase in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The southern distribution of Mya arenaria may be restricted by a limit of 28 °C for both adults and larvae (Newell & Hidu, 1986; Strasser, 1999). Clams did not survive temperatures higher than 28 °C in Chesapeake Bay, and 24 hr LT₅₀ for adults were 32.5 °C and 34.4 °C in larvae Stickney (1964) found that all larvae died after 14 days at 28°C. However, clams from the high intertidal survived higher temperatures (>25 °C ) than clams from the mid tidal level (Kennedy & Mihursky, 1972). Growth, burrowing, and pumping rates are affected by temperature. Over-wintering Mya arenaria survived temperatures as low as -2°C in Alaska, persisted in the St. Lawrence estuary exposed to freezing winter air temperatures, and survived 60 days of ice in the severe 1995/1996 winter in the Wadden Sea (Strasser, 1999). However, severe winters have been known to cause mortality (Rasmussen, 1973; Strasser, 1999). Overall, Mya arenaria is tolerant of a wide range of temperatures (eurythermal) although at its upper thermal limit a small increase in temperature (1 °C) results in substantial mortality (Anonymous, 1996). This species burrowing habit removes it from the direct influence of extreme temperatures, especially the deep dwelling adults. Therefore, a low intolerance to temperature change is reported, although populations at the edge of its range or at high tidal level are likely to be more intolerant. Similarly, juveniles dwelling near the surface are likely to be more vulnerable to extremes of temperature. It is likely that individuals affected by temperature change would recover within a few weeks of a return to original temperature regime.

Decrease in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

Increase in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Changes in light attenuation are likely to affect phytoplankton, benthic diatom and algal productivity and therefore affect food availability for the soft-shell clam. However Mya arenaria is unlikely to be affected directly.

Decrease in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Increased wave exposure in the long term is likely to alter the sediment grain size, and erode finer sediments, while decreased wave exposure is likely to increase the deposition of finer sediments. Overall, changes in wave exposure may increase or decrease the available habitat for Mya arenaria. Therefore an intolerance of intermediate has been recorded.
Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Noise

1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

This species probably responds to local vibration, especially in the vicinity of the siphonal opening, withdrawing its siphons in response to potential predators, however it is unlikely to respond to noise pollution.

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

The siphons bear sensory tentacles that are probably light sensitive and responsive to shading, so that siphons withdraw to avoid predators, however, the visual range is probably extremely limited and this species is unlikely to respond to visual disturbance.

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

Up to 50% of juveniles and 20% of un-harvested clams have been reported to be killed by shell breakage or smothering by tailings resulting from hydraulic dredging for clams. However, abrasion due to a passing scallop dredge (see benchmark) may kill a few individuals where the sediment is penetrated. Mya arenaria can occupy burrows of 15-20 cm deep and up to 40 cm deep so that adults are likely to survive, while young adults and juveniles may be lost. Therefore, an intolerance of intermediate has been recorded. A recoverability of high has been recorded (see additional information below).

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

Clams can not burrow unless they are submerged. Small clams could re-burrow in ca. 5 min whereas older clams (>5cm) took >10 hrs. Pfitzenmeyer & Droebeck (1967) reported that 62% of small clams (35-50 mm), 39% of medium sized (51-65 mm) and only 21% of large clams (66-75 mm) had reburrowed within 48 hours. Emerson et al. (1990) noted that large clams could not burrow unless their anterior edge was in contact with the sediment and that small clams were held in suspension, but suggested that this would not result in significant mortality. Clams took longer to burrow in mud. Disturbed clams that re-buried themselves often burrowed to shallower depths than before the disturbance. Hence increasing their susceptibility to predation from shorebirds, and crabs. Together with the increased risk of predation, desiccation and temperature extremes while exposed at the sediment surface this may result in increased mortality. Therefore, an intolerance of intermediate has been recorded. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

• evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
• evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
• evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

Mya arenaria has been shown to accumulate Tributyl tin (TBT) with a concentration factor of 539,690 (Bryan & Gibbs, 1991). Bouchard et al. (1999) reported that 8.1 x 10^-7M dibutyltin and 4.5 x 10^-6 tributyltin resulted in 50% reduction of phagocytic activity in haemocytes, resulting in immunosuppression, and presumably a higher susceptibility to disease. However, little other information regarding the toxicity of TBT in the soft-shell clam was found. Bivalve mollusc larvae have been shown to be sensitive to TBT. Bryan & Gibbs (1991) reported evidence for the correlation between TBT contamination and recruitment failure in a number of bivalve species. Lack of recruitment in affected population would result in a significant decline in the population due to natural mortality of the adults alone. Newell & Hidu (1986) reported that Mya arenaria accumulated pesticides, however, no information concerning toxicity was given. Therefore, an intolerance of intermediate has been recorded. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Heavy metal contamination

Evidence

The embryonic and larval stages of bivalves are the most intolerant of heavy metals (Newell & Hidu, 1986; Bryan, 1984). Bryan (1984) suggested that mercury (Hg) was the most toxic, but that Cu, Cd and Zn may be the most problematic in the field. Eisler (1977) exposed Mya arenaria to a mixture of heavy metals in solution at concentrations equivalent to the highest recorded concentrations in interstitial waters in the study area. At 0 °C and 11 °C (winter temperatures)) 100% mortality occurred after4-10 weeks. At 16-22 °C (summer temperatures) 100% mortality occurred after 6-14 days, indicating greater intolerance at higher temperatures. Eisler (1977) reported the following LC₅₀ in mg/l:

• 0.035 Cu;
• 0.15 Cd;
• 1.55 Zn;
• 8.8 Pb;
• 300 Mn; and
• >50 for Ni.

In Eisler's study (1977) the Mya arenaria accumulated Pb > Cu and Zn > Mn > Ni. Therefore an intolerance of intermediate has been recorded. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Hydrocarbon contamination

Evidence

A spill of fuel oil and jet fuel contaminated sediments in Long Cove, Maine. Small clams close to the surface were killed first but as the oil penetrated the sediment larger clams were killed. Subsequent weathering removed oils from the surface of the sediment, but oil accumulated between 15-25 cm in the sediment for at least 6 years, varying in depth between 2-15 cm below the surface depending on location. Mya arenaria spat attempting to recolonize the affected area survived near the surface, even in the presence of 250 ppm of hydrocarbons. As the juveniles grew they burrowed deeper and died once they contacted the oil layer (Dow, 1978; Johnston, 1984). Mya arenaria was excluded from polluted sediments in an estuarine mudflat affected by petrochemical effluents, and did not appear until 2.5-4 km from the outfalls (moderate pollution) (McLusky, 1982). Therefore an intolerance of high has been recorded. Given the patchy nature of populations, the sporadic nature of recruitment, and the extended recoverability in oil contaminated sediments, as in the example above, a recoverability rank of moderate has been recorded (see additional information below).

Radionuclide contamination

Evidence

Insufficient
information

Changes in nutrient levels

Evidence

No information regarding the direct effects of nutrients on Mya arenaria was found. However, increased nutrients are likely to enhance ephemeral algal and phytoplankton growth, increased organic material deposition and bacterial growth. At low levels increase phytoplankton and benthic diatoms may increase food availability for benthic infauna, including Mya arenaria. The presence of algal mats may act as refuges from predators (Newell & Hidu, 1986). However, increased levels of nutrient (beyond the carrying capacity of the environment) may result in eutrophication, algal blooms and concomitant reductions in oxygen concentrations and hypoxia e.g. in the Kattegat (Rosenberg & Loo, 1988) (see oxygenation below). Eutrophication is often associated with the growth of blankets of algae (Ulva sp.) or mussels (Mytilus edulis). Large-scale mortalities due to smothering by algal mats were reported by Dow & Wallace (1961). Mussels beds form on the surface of the sediment, and in high enough densities may deprive the infaunal clams of food and eventually of oxygen. In the long term, bio-deposition by the mussels and sedimentation between the mussels raises the height of the sediment, preventing the clams from reaching the surface, therefore destroying the clam bed (Dow & Wallace, 1961). Therefore, an intolerance of intermediate has been recorded at the level of the benchmark, although intolerance to severe nutrient enrichmant and eutrophication may be higher.
Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Increase in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Mya arenaria tolerates a wide range of salinities and is a euryhaline osmoconformer (Strasser, 1999). Like several bivalves it can regulate cell volume to some extent by mobilising its amino acid pool (Newell & Hidu, 1986). The lowest salinity at which Mya arenaria occurred in the Baltic was 4.5-5.0 psu and lower limits of 4 psu and 5 psu have also been reported from the west Atlantic coast (Strasser, 1999). Larvae are more intolerant of low salinity than adults and grow optimally between 16-32 psu (Stickney, 1964). Salinity tolerance is correlated with temperature, the clams tolerating lower salinities at lower temperature and being able to acclimate to decreasing salinities more rapidly at higher temperatures (Newell & Hidu, 1986). High mortalites (98%) were reported due to freshwater runoff after hurricane Agnes in Chesapeake Bay when salinities dropped to 2 psu (Shaw & Hammons, 1974). However, in St Lawrence Bay clams survived 1.5 days at 1 psu at low temperatures (Newell & Hidu, 1986). Mya arenaria also persists in areas that reach >35 psu (Strasser, 1999). Therefore, given its wide salinity tolerance and widespread distribution from the subtidal to estuaries Mya arenaria is probably tolerant of changes in salinity at the benchmark level and an intolerance of low has been recorded. Populations in the upper intertidal or the upper reaches of estuaries and juveniles living on the surface and shallow depth in the sediment are probably more vulnerable to changes in salinity. Newell & Hidu (1986) reported laboratory studies that demonstrated acclimation from 30 - 22 psu with 60 hrs at 4°C and 10 hours at 10°C. Therefore, recovery from salinity stress is likely to be rapid, within a few days and a recoverability of immediate has been recorded.

Decrease in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

Mya arenaria tolerates low oxygen concentration and the presence of hydrogen sulphide for several days or weeks. Fifty percent mortality was observed after 21 days at 10 °C exposed to 0.15 ml O₂/l (0.21 mg/l) in the presence of H₂S (Theede et al. 1969). At 0.5-1.0 ml O₂/l (0.7-1.4mg/l), 8% survived in sediment for 32 days and 54% survived for 43 days (Rosenberg et al., 1991). Rosenberg & Loo (1988) reported mass mortalities of Mya arenaria and Cerastoderma edule in the 1980s in the Kattegat, which were associated with eutrophication and resultant low oxygen concentrations over several years (often <1 ml O₂/l). However, Mya arenaria species is probably tolerant of 2mg/l for a week and a rank of low intolerance has been given. Anaerobic metabolism allows bivalves to maintain important metabolic function while emersed or under hypoxic conditions but may deplete energy reserves and result in an 'oxygen debt' on return to normal conditions. Therefore, recovery on return to normoxic conditions may take several hours or even days.

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

Several parasites occur in Mya arenaria, e.g. cercaria of Himasthla leptosoma, the nemertean parasite Malacobdella sp. and the copepod Myicola metisciensis may be commensal (Clay, 1966). The protozoan, Perkinsus sp. related to the species responsible for 'Dermo' disease in oysters, has recently been isolated from Mya arenaria in Chesapeake Bay, USA (McLaughlin et al., 2000, summary only). Mya arenaria is also known to suffer from cancers, disseminated neoplasia and gonadal tumours. Disseminated neoplasia has been reported to occur in 20% of the population in north eastern United States and Canada, and caused up to 78% mortalities in New England (Brousseau & Baglivo, 1991; Landsberg, 1996). Presumably gonadal tumours reproduce reproductive capacity. The occurrence of gonadal tumours in Mya arenaria was related to the occurrence of the blooms of the toxigenic dinoflagellate Alexandrium spp. Lansberg (1996) reported a correlation between the occurrence of gonadal tumours and neoplasia in bivalves and paralytic shellfish poisoning due to the accumulation of toxins released by toxigenic dinoflagellate blooms. Therefore an intolerance of intermediate has been recorded. However, so far there have been no records of parasites or disease in the UK or Europe (Strasser, pers comm.). Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

The American hard-shelled clam Mercenaria mercenaria colonized the niche left by Mya arenaria killed after cold winter of 1947 and1962/63 in Southampton Water (Eno et al. 1997). The Mya arenaria populations had not recovered in this area by 1997 (Eno et al., 1997). Therefore, the above non-native species may compete with Mya arenaria for suitable habitat and an intolerance of intermediate has been reported. Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Removal of Mya arenaria will remove a high proportion of the population, either removed by harvesting or killed in the process. For example, up to 50% of juveniles and 20% of un-harvested clams have been reported to be killed by shell breakage or smothering by tailing by hydraulic dredging for clams (Emerson et al., 1990). Disturbed clams that re-buried themselves often burrowed to shallower depths than before the disturbance, hence increasing their susceptibility to predation from shorebirds, and crabs (Emerson et al., 1990). Together with the increased risk of predation, desiccation and temperature extremes while exposed at the sediment surface this may result in increased mortality and an intolerance of intermediate has been recorded.
Given the patchy nature of populations and the sporadic nature of recruitment a recoverability of high has been recorded (see additional information below).

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Oyster dredging removed most fauna except Abra tenuis, Cerastoderma edule and Mya arenaria, which were probably displaced (Gubbay & Knapman, 1999). Mechanical harvesting (dredging) for Arenicola marina resulted in drastic reduction in the population Mya arenaria in the Wadden Sea (Beukema, 1995). Some clams were harvested by bait diggers, but most of mortality resulted from broken shells and predation on those individuals (especially large clams) that could not burrow before the tide receded. As a result the population of Mya arenaria became very low between 1979-1986, and the population took about 5 years to recover its original density (Beukema, 1995). Therefore ,an intolerance of high has been recorded together with a recoverability of high.