Syringammina fragilissima field on Atlantic lower bathyal mud

Summary

UK and Ireland classification

Description

The assemblage is characterized by dense aggregations of the xenophyophore Syringammina fragilissima on coarse sediment. The associated species vary with depth but may include squat lobsters (Munida), ophiuroids, Majid crabs, pale encrusting sponges (yellow, white, grey, cream, pink) and sediment-dwelling anemones. The same epifaunal assemblage is also found in the lower bathyal and on other sediments but associated infauna are likely to differ. The characterizing species listed refer to all Syringammina fragilissima assemblages not just those associated with the zone and substratum specified in this biotope. (Information from JNCC, 2022).

Depth range

1300-2100 m

Additional information

Syringammina fragilissima was the first xenophyophore described (Brady, 1883) but details of life history, ecology, and taxonomy remain largely unknown (Pawlowski et al., 2003). DNA evidence from a congeneric species, Syringammina corbicula, suggests the genus is part of the subphylum Foraminifera (Pawlowski et al., 2003). 

Syringammina fragilissima is the dominant species on mud within the mid bathyal zone (M.AtMB.Mu.XenCom.SyrFra biotope) and the lower bathyal zone (M.AtLB.Mu.XenCom.SyrFra biotope), on coarse substrata in both the mid and lower bathyal zones (M.AtMB.Co.XenCom.SyrFra and M.AtLB.Co.XenCom.SyrFra respectively) and on mixed sediments in the mid and lower bathyal zones (M.AtMB.Mx.XenCom.SyrFra and M.AtLB.Mx.XenCom.SyrFra respectively). This review assesses the sensitivity of the XenCom.SyrFra biotopes as a group. 

Listed By

- none -

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

The xenophyophore Syringammina fragilissima occurs on mud, mixed and coarse substrata, at a range of depths in the Atlantic deep-sea. Assemblages occur on mud within the mid bathyal zone (M.AtMB.Mu.XenCom.SyrFra biotope) and the lower bathyal zone (M.AtLB.Mu.XenCom.SyrFra biotope), on coarse substrata in both the mid and lower bathyal zones (M.AtMB.Co.XenCom.SyrFra and M.AtLB.Co.XenCom.SyrFra respectively) and on mixed sediments in the mid and lower bathyal zones (M.AtMB.Mx.XenCom.SyrFra and M.AtLB.Mx.XenCom.SyrFra respectively). The sensitivity of these Syringammina fragilissima field biotopes is therefore assessed as a group, assuming that their sensitivity is very similar in terms of substratum and functional groups present. Any differences in species or biotope response to pressures are highlighted.

The predominant species for the biotopes is the xenophyophore Syringammina fragilissima. Syringammina spp. can reach high densities, for example, up to 40 /m2 at 3,300 m on the Cape Verde Plateau, 1 /m2 at bathyal depths on the New Zealand Plateau, 1 to 2 /m2 and 15 to 20 /m2 on the Northwest Atlantic slope (Tendal & Lewis, 1978; Tendal, 1996; Levin & Gooday, 1992; Hughes & Gooday, 2004). In the Rockall Trough, Syringammina fragilissima was recorded at a density of 10 /m2 at 1,108 m  (Roberts et al., 2000; Hughes & Gooday, 2004). 

Xenophyophores are gigantic multinucleate unicellular protists found on the seafloor below 500 m worldwide, that develop complex tests and can grow between a few millimetres and 20 cm across. However, the biology of Syringammina spp. is poorly studied and information is derived from studies of this species and other xenophyophores. Buhl-Mortensen et al. (2010) reported that xenophyphores increase the biodiversity and habitat heterogeneity of deep-sea habitats. Gooday et al. (2017) suggested that, when abundant, xenophyphores were keystone species in deep-seafloor habitats because they can host a diverse assemblage of macrofaunal, meiofaunal and microfaunal organisms and enhance the deposition of organic-rich particulates. For example, Hughes & Gooday (2004) reported a total of 3647 specimens of foraminiferans, of 259 species from four dead (empty) tests of Syringammina fragillissima from the Darwin Mounds area, together with 175 to 1217 metazoans per test. Macrofauna and meiofauna within the test include species of polychaetes, molluscs, isopods, ophiuroids, sipunculids, sponges, nemerteans, turbellarians, nematodes (the dominant taxa), ostracods and harpacticoids copepods (Hughes & Gooday, 2004; Buhl-Mortensen et al., 2010, Table 12). Lewis & Thomas (1988) suggested that the contribution of xenophyophores to diversity was greatest on coarse sediments in the Eastern Pacific. Xenophyophore tests may also passively trap larvae and other propagules and concentrate prey populations for the benefit of other species (Hughes & Gooday, 2004). Therefore, the loss of the Syringammina fragilissima population would result in the loss or degradation of the biotope. Therefore, the sensitivity of the biotope is dependent on this species' sensitivity alone.

Some asteroids, holothurians, and monoplacophoran molluscs are reported to feed on xenophyophores but they are thought to be of low food values since their biomass is low compared to their volume, but their associated community may provide a better food source (Tendal, 1985; Hughes & Gooday, 1984, Gooday et al., 2020).  No other characterizing species are listed for these biotopes. However, several associated species may occur. These may include squat lobsters (Munida), Ophiuroids, Majid crabs, pale encrusting sponges (yellow, white, grey, cream, pink) and sediment-dwelling anemones. As these are all ubiquitous organisms and are not unique to these biotopes, they are not considered significant to the sensitivity assessment. Furthermore, the presence of all these species is not essential for the classification of these biotopes. More information on many of these species can be found in other biotope assessments available on this website.

Resilience and recovery rates of habitat

Specific evidence about the ecology, life history and population dynamics of Syringammina fragilissima is limited. Hence, the evidence used to assess its recovery rates and resilience is based on xenophyphore ecology and cogeneric species. Xenophyophores comprise a multinucleate plasmodium (cytoplasm), surrounded by tubes of an organic material called 'granellare'. The cytoplasm characteristically contains barite crystals (barium sulphate) called 'granellae' (but may also include other metals). Strings or masses of faecal pellets known as 'stercomare' are retained outside the 'granellare' but inside the test. The cytoplasm and 'stercomare' are enclosed by a test made of agglutinated sediment particles. The xenophyophore test ranges from <1 cm to 20 cm in size and varies in shape and organization depending on the species (Tenday, 1972, 1996; Levin & Thomas, 1988).

A detailed description of Syringammina fragilissima is given by Tendal (1972). Agglutinated xenophyophore tests are extremely fragile and break up in a trawl or dredge (Roberts et al.,  2000). They are composed of materials from the surrounding sediment, e.g. fine sediment particles and dead foraminifera tests (Tendal, 1972; Levin & Thomas, 1988; Hughes & Gooday, 2004). Hughes & Gooday (2004) collected four empty (dead) Syringammina fragilissima tests from the Darwin Mounds that ranged from 3 to 5 cm across. They noted that the largest recorded specimen was 10 cm in diameter but that this specimen was probably trimmed by the core tube (Lamont, 1998, cited in Hughes & Gooday, 2004).  Hughes & Gooday (2004) described the test as friable, slightly eroded, with substantial amounts of mud trapped between the branches. Brady (1883) described the test as fragile, composed of fine sand, without sufficient strength to bear handling without injury.

Xenophyophores reach high densities in areas of high surface productivity and high particle flux on topographical features such as seamounts, canyons, troughs, ridges and continental slopes (Tendal, 1972; Levin & Thomas, 1988; Roberts et al., 2000; Levin & Nittrouer, 2013; Henry et al., 2014). Levin & Thomas (1988) suggested that their aggregation on raised seafloor features or on continental slopes where water flow was adequate to transport particulates or the concentration of suspended sediment supported suspension feeding. Levin & Thomas (1988) also noted their abundance declined where water flow was high enough to mobilise the sediment or form ripples on the seabed. Most xenophyophores, including Syringammina fragilissima, are epifaunal and sessile living in the top few centimetres of the sediment (Tendal, 1972; Tendal & Lewis, 1978; Henry et al., 2014). Tendal & Lewis (1978) suggested that Syringammina species were suspension feeders using a network of pseudopodia (arm-like projections) within the test cavity to filter passing particulates. Direct evidence for feeding is limited but Laureillard et al. (2004) concluded that Syringammina corbicula were selective suspension feeders that accumulated bacteria in their 'stercomare' as a possible food reserve. The species has been documented on various sediment types and grain sizes (Henry et al., 2014). Tendal & Lewis (1978) found that a New Zealand species Syringammina tasmanesis was unselective with grain type, constructing their test with the same sediment (in terms of grain size and composition) it was living on.

Syringammina fragilissima has been recorded in the Faroe Channel, Darwin Mounds, the Rockall-Hatton Channel, the Hebridean slope, the Hebrides Terrace Seamount and the Nazare Canyon in the North East Atlantic and off New Zealand (Brady, 1883, Tendal, 1972; Roberts et al., 2000; Hughes & Gooday, 2004; Gooday et al., 2011; Henry et al., 2014; Ashford et al., 2014). Gooday et al. (2020) noted that chronic undersampling was an issue for establishing geographical ranges of deep-sea Foraminifera. Ashford et al. (2014) used habitat modelling to predict the distribution of xenophyophores, including Syringammina fragilissima. They suggested that Syringammina fragilissima had a more narrow distribution than xenophyophores as a whole and was likely to be limited to: Rockall Bank, Hebrides Terrace and Anthon-Dohrn Seamounts, Rosemary Bank, Wyville Thomson Ridge and along the UK continental slope, the Iceland-Faroe Rise, the Icelandic continental slope and Reykjanes Ridge, along the mid-Atlantic Ridge near the Azores, to the north Labrador Sea, north of the Bahamas, the Madagascar Plateau, and around New Zealand, but noted that the lack of samples required extrapolation of the model so it may not represent the entire distribution. Ashford et al. (2004) concluded that depth, oxygen parameters, carbon chemistry, nitrate concentration and temperature were the most important parameters affecting xenophyophore distribution while hydrographic parameters were the least important. Ashford et al. (2004) suggested that the 'peak habitat suitability parameters' for Syringammina fragilissima were at a depth between ca 870 and 1180 m, a calcite saturation state of between ca 2.6 and 3.4, and a temperature of between 5.3 and 7.7°C. It should be noted that the species is recorded from a greater depth range. 

No evidence of growth rates of Syringammina fragilissima was found. However, some species of xenophyophores are thought to construct their tests rapidly (Levin, 1994). For example, during an in situ observational experiment on the Madeira Abyssal Plain, Reticulammina labyrinthica (from the Family Psamminidae) was shown to roughly double in size, with a 3-10x increase in volume over eight months during which sediment was incorporated into the test, growing in phases of 2 to 3 days in between two-month gaps of no activity (Gooday et al., 1993). Gooday et al. (1993) also noted that the smallest specimen showed no signs of growth during the first five months of observation, suggesting an early quiescent stage. They also suggested that their specimens could not be more than one to two years old. Furthermore, observations of Reticulammina tests on eastern Pacific seamounts indicated rapid growth (Levin, 1994).

The life history of xenophyophores, including Syringammina fragilissima remains largely unknown. Buzas et al. (1982) suggest xenophyophores switch between sexual and asexual reproduction, alternating between haploid and diploid generations, as do other foraminifera. Shallow water benthic foraminifera life cycles are also thought to be strongly influenced by seasonality and environmental stability (Austin, 2003). In foraminifera, the haploid form (gamont) is the sexual form, which divides via mitosis (asexually) to form tens to thousands of small flagellate haploid gametes (depending on species). On fertilization, they form the larger asexual form (the agamont). At maturity, after cycles of asexual reproduction, the agamont leaves its test and divides meiotically (sexually) to form a number of flagellate haploid gamonts (see Haynes, 1981, cited in Wikipedia, 2024). Hence, the 'dead' or 'empty' tests observed in xenophyphore assemblages. Asexual reproduction is expected to be adopted more frequently in stable environments, where identical offspring will be adapted to the environment (Murray, 2014). Sexual reproduction is thought to be adopted in variable environmental conditions to increase genetic diversity and, therefore, resistance (Hallock, 1985). Other species of smaller foraminifera exhibit rapid growth and maturity at between 4 and 104 weeks, and a longevity of 0.3 to 24 months depending on the species (Murray, 1991, 2014).

No information on recovery rates in xenophyophores was found. However, Gooday et al. (2017) suggested they may recover from mining impacts quickly based on their rapid growth rates and may be pioneer colonizers of new substrata. For example, Hess et al. (2001) reported that xenophyophores (possibly Syringammina (?) fragilissima) were absent from the benthos in 1994 after the June 1991 Mt Pinatubo ashfall that deposited ash across the deep-seafloor of the South China Sea. They were rare by June 1996 but were important recolonizers and occurred in large numbers in December 1996 and summer 1998, ca. five years after deposition. No information on 'adult' mobility was found. Adults probably have limited mobility using their pseudopodia but dispersal is probably achieved via their flagellate gametes.  

Resilience assessment: Syringammina fragilissima has a more restricted distribution than other xenophyophores (Ashford et al., 2014) but occurs on a range of sediment types (Henry et al., 2014) and there is evidence from other xenophyophore species that suggest rapid growth rates and short lifespans (Gooday et al., 1993; Levin, 1994).  Therefore, where resistance is 'Medium' or 'Low', resilience is probably 'High' but where the resistance is 'None' (severe loss of population) recovery may take ca five years (Hess et al., 2001) depending on the availability of recruits so resilience is assessed as 'Medium'. However, the assessments are made with 'Low' confidence due to the absence of evidence. 

Hydrological Pressures

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ResistanceResilienceSensitivity
Temperature increase (local) [Show more]

Temperature increase (local)

Benchmark. A 5°C increase in temperature for one month, or 2°C for one year. Further detail

Evidence

Benthic foraminiferal assemblages have been utilised as paleoceanographic indicators of temperature due to their sensitivity and uptake of oxygen isotopes relative to temperature (Urey, 1947). However, information on the temperature range of xenophyophores is limited. Ashford et al. (2014) found that temperature was one of the most important variables when creating predictive distribution models for Xenophyophorea and Syringammina fragilissima. Specifically, a temperature range between ca 5.3 and 7.7°C was described as the most important 'peak habitat suitability parameter' for Syringammina fragilissima. In New Zealand, the species has been found at 4-8°C (Tendal & Lewis, 1978). This may suggest that Syringammina fragilissima is sensitive to temperature changes outside this range. However, experimental work has not been carried out on this species and Ashford et al. (2014) further highlight that temperature preferences for xenophyophores are poorly understood. 

However, sea surface temperatures are not relevant to deep water species. For example, in the Rockall Trough, the deep water temperature and salinity are determined by the ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater temperature in Rockall Trough was 10°C at ca 500 m and dropped to 5°C at ca 1,500 m (in October 2006). In addition, the North East Atlantic exhibits seasonal thermoclines and winter mixing but a permanent thermocline at ca 500 m (Tyler & Young, 1998). In the Rockall Trough, the seasonal thermocline develops at ca 200 m, winter mixing occurs at about 600 m, while the permanent thermocline extends from ca 800 m to ca 1,000 m (Gage, 1986). Sherwin et al. (2012) reported that the seawater temperature of the upper 800 m of the Rockall Trough had fluctuated between ca 9.0 and 10.5°C from 1948 to 2010.

Henry et al. (2014) noted that Syringammina fragilissima was more frequent at shallower stations (above 1,500 m) than Solenosmilia on the Hebrides Terrace Seamount, in areas of higher oceanographic variability. However, the 'higher variability' zone at 1,200 to 1,500 m exhibited a mean temperature of 5.3+/-0.93°C and a mean salinity of 35.07+/-0.08 (Henry et al., 2014). Syringammina fragilissima from the North Atlantic was found at 600 to 1,300 m, at 4 to 8°C in a salinity range between 34.4%-34.6%, characteristic of Antarctic Intermediate Water formed by cool, low salinity surface waters (Tendal, 1972; Tendal & Lewis, 1978). Hughes & Gooday (2004) collected Syringammina fragilissima from the Darwin Mounds area at ca 600 to 1000 m, in an area overlaid by the Eastern North Atlantic Water with a salinity of 35.4 to 35 and a temperature of 2 to 4°C. Tenday & Gooday (1981) reported Syringammina sp. from 1,000 m and 3,000 m of the Mauretania, west Africa. Syringammina fragilissima has also been recorded from <1,550 m on the Nazare Canyon along the Portuguese margin of the NE Atlantic shelf (Gooday et al., 2011).  

Sensitivity assessment.  At the depths this species occurs (below 600 m), and especially below the permanent thermocline, temperatures are likely to be stable and organisms are unlikely to be exposed to the range of temperatures and, in particular, the rapidity of temperature change experienced at the sea surface. As deep-water species, they may be less adapted to rapid changes in temperature. Hence, while natural temperature changes are unlikely, exposure to localised thermal effluents at the benchmark level (e.g. from deep-sea installations or operations, however unlikely) may be detrimental. Therefore, resistance is assessed as 'Medium' on the presumption that localised thermal effluent has a limited dispersal range, affects a limited area, and that xenophyophores have limited mobility. Hence, Resilience is assessed as 'High' and sensitivity as 'Low' but with 'Low' confidence as direct evidence is limited. 

Medium
Low
NR
NR
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High
Low
NR
NR
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Low
Low
NR
NR
Help
Temperature decrease (local) [Show more]

Temperature decrease (local)

Benchmark. A 5°C decrease in temperature for one month, or 2°C for one year. Further detail

Evidence

Benthic foraminiferal assemblages have been utilised as paleoceanographic indicators of temperature due to their sensitivity and uptake of oxygen isotopes relative to temperature (Urey, 1947). However, information on the temperature range of xenophyophores is limited. Ashford et al. (2014) found that temperature was one of the most important variables when creating predictive distribution models for Xenophyophorea and Syringammina fragilissima. Specifically, a temperature range between ca 5.3 and 7.7°C was described as the most important 'peak habitat suitability parameter' for Syringammina fragilissima. In New Zealand, the species has been found at 4-8°C (Tendal & Lewis, 1978). This may suggest that Syringammina fragilissima is sensitive to temperature changes outside this range. However, experimental work has not been carried out on this species and Ashford et al. (2014) further highlight that temperature preferences for xenophyophores are poorly understood. 

However, sea surface temperatures are not relevant to deep water species. For example, in the Rockall Trough, the deep water temperature and salinity are determined by the ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater temperature in Rockall Trough was 10°C at ca 500 m and dropped to 5°C at ca 1,500 m (in October 2006). In addition, the North East Atlantic exhibits seasonal thermoclines and winter mixing but a permanent thermocline at ca 500 m (Tyler & Young, 1998). In the Rockall Trough, the seasonal thermocline develops at ca 200 m, winter mixing occurs at about 600 m, while the permanent thermocline extends from ca 800 m to ca 1,000 m (Gage, 1986). Sherwin et al. (2012) reported that the seawater temperature of the upper 800 m of the Rockall Trough had fluctuated between ca 9.0 and 10.5°C from 1948 to 2010.

Henry et al. (2014) noted that Syringammina fragilissima was more frequent at shallower stations (above 1,500 m) than Solenosmilia on the Hebrides Terrace Seamount, in areas of higher oceanographic variability. However, the 'higher variability' zone at 1,200 to 1,500 m exhibited a mean temperature of 5.3+/-0.93°C and a mean salinity of 35.07+/-0.08 (Henry et al., 2014). Syringammina fragilissima from the North Atlantic was found at 600 to 1,300 m, at 4 to 8°C in a salinity range between 34.4%-34.6%, characteristic of Antarctic Intermediate Water formed by cool, low salinity surface waters (Tendal, 1972; Tendal & Lewis, 1978). Hughes & Gooday (2004) collected Syringammina fragilissima from the Darwin Mounds area at ca 600 to 1000 m, in an area overlaid by the Eastern North Atlantic Water with a salinity of 35.4 to 35 and a temperature of 2 to 4°C. Tenday & Gooday (1981) reported Syringammina sp. from 1,000 m and 3,000 m of the Mauretania, west Africa. Syringammina fragilissima has also been recorded from <1,550 m on the Nazare Canyon along the Portuguese margin of the NE Atlantic shelf (Gooday et al., 2011).  

Sensitivity assessment.  At the depths this species occurs (below 600 m), and especially below the permanent thermocline, temperatures are likely to be stable. Hence, organisms are unlikely to be exposed to the range of temperatures and the rapidity of temperature change experienced at the sea surface. As deep-water species, they may be less adapted to rapid changes in temperature. Hence, while natural temperature changes are unlikely, exposure to localised thermal effluents at the benchmark level (e.g. from deep-sea installations or operations, however unlikely) may be detrimental. Therefore, resistance is assessed as 'Medium' on the presumption that localised thermal effluent has a limited dispersal range, affects a limited area, and that xenophyophores have limited mobility. Hence, Resilience is assessed as 'High' and sensitivity as 'Low' but with 'Low' confidence as direct evidence is limited. 

Medium
Low
NR
NR
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High
Low
NR
NR
Help
Low
Low
NR
NR
Help
Salinity increase (local) [Show more]

Salinity increase (local)

Benchmark. A increase in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

Seawater salinity in the deep sea is more stable than in inshore waters. For example, in the Rockall Trough, the deep water temperature and salinity are determined by ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater salinity of the upper 800 m of the Rockall Trough had fluctuated between ca 35.25 and 35.45 from 1948 to 2010. Sherwin et al. (2012) reported that the salinity of the seawater in Rockall Trough was 35.4 at ca 500 m and dropped to 35.15 at ca 1,500 m (in October 2006). 

Ashford et al. (2014) suggested that the significance of depth on the distribution of xenophyophores corresponded to changes in a range of environmental factors including salinity. Syringammina fragilissima from the North Atlantic was found at 600 to 1,300 m, at 4 to 8°C in a salinity range between 34.4%-34.6%, characteristic of Antarctic Intermediate Water formed by cool, low salinity surface waters (Tendal, 1972; Tendal & Lewis, 1978). Hughes & Gooday (2004) collected Syringammina fragilissima from the Darwin Mounds area at ca 600 to 1000 m, in an area overlaid by the Eastern North Atlantic Water with a salinity of 35.4 to 35 and a temperature of 2 to 4°C. Henry et al. (2014) noted that Syringammina fragilissima was more frequent at shallower stations (above 1,500 m) than Solenosmilia on the Hebrides Terrace Seamount, in areas of higher oceanographic variability. However, the 'higher variability' zone at 1,200 to 1,500 m exhibited a mean temperature of 5.3+/-0.93°C and a mean salinity of 35.07+/-0.08 (Henry et al., 2014).

Sensitivity assessment. The xenophyophores that dominate this biotope are probably adapted to stable salinity conditions and have limited tolerance to salinity change. Changes in salinity would probably make the xenophyophore expand or contract. An increase in salinity from full to >40 psu is probably detrimental to the important characteristic xenophyophore species of the biotope. However, it is unlikely this biotope would be exposed to hypersaline conditions (or effluent) unless from a newly opened brine seep or an unknown deep-sea operation. In addition, there is no direct evidence of the effects of hypersaline water on the characteristic species. Therefore, there is 'Insufficient evidence' on which to base an assessment. Further evidence is required. 

Insufficient evidence (IEv)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
Help
Salinity decrease (local) [Show more]

Salinity decrease (local)

Benchmark. A decrease in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

Evidence

Seawater salinity in the deep sea is more stable than in inshore waters. For example, in the Rockall Trough, the deep water temperature and salinity are determined by ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater salinity of the upper 800 m of the Rockall Trough had fluctuated between ca 35.25 and 35.45 from 1948 to 2010. Sherwin et al. (2012) reported that the salinity of the seawater in Rockall Trough was 35.4 at ca 500 m and dropped to 35.15 at ca 1,500 m (in October 2006). 

Ashford et al. (2014) suggested that the significance of depth on the distribution of xenophyophores corresponded to changes in a range of environmental factors including salinity. Syringammina fragilissima from the North Atlantic was found at 600 to 1,300 m, at 4 to 8°C in a salinity range between 34.4%-34.6%, characteristic of Antarctic Intermediate Water formed by cool, low salinity surface waters (Tendal, 1972; Tendal & Lewis, 1978). Hughes & Gooday (2004) collected Syringammina fragilissima from the Darwin Mounds area at ca 600 to 1000 m, in an area overlaid by the Eastern North Atlantic Water with a salinity of 35.4 to 35 and a temperature of 2 to 4°C. Henry et al. (2014) noted that Syringammina fragilissima was more frequent at shallower stations (above 1,500 m) than Solenosmilia on the Hebrides Terrace Seamount, in areas of higher oceanographic variability. However, the 'higher variability' zone at 1,200 to 1,500 m exhibited a mean temperature of 5.3+/-0.93°C and a mean salinity of 35.07+/-0.08 (Henry et al., 2014).

Sensitivity assessment. The xenophyophores that dominate this biotope are probably adapted to stable salinity conditions and have limited tolerance to salinity change. Changes in salinity would probably make the xenophyophore expand or contract. A decrease in salinity from full to reduced (18-30 psu) is probably detrimental to the important characteristic xenophyophore species of the biotope. However, it is unlikely this biotope would be exposed to hyposaline conditions (or effluent) unless from a newly opened freshwater seep or an unknown deep-sea operation. In addition, there is no direct evidence of the effects of hypersaline water on the characteristic species. Therefore, there is 'Insufficient evidence' on which to base an assessment. Further evidence is required. 

Insufficient evidence (IEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
Help
Water flow (tidal current) changes (local) [Show more]

Water flow (tidal current) changes (local)

Benchmark. A change in peak mean spring bed flow velocity of between 0.1 m/s to 0.2 m/s for more than one year. Further detail

Evidence

Xenophyophores reach high densities in areas of high surface productivity and high particle flux on topographical features such as seamounts, canyons, troughs, ridges and continental slopes (Tendal, 1972; Levin & Thomas, 1988; Roberts et al., 2000; Levin & Nittrouer, 2013; Henry et al., 2014). Levin & Thomas (1988) suggested that their aggregation on raised seafloor features or on continental slopes where water flow was adequate to transport particulates or the concentration of suspended sediment supported suspension feeding. Levin & Thomas (1988) also noted their abundance declined where water flow was high enough to mobilise the sediment or form ripples on the seabed. Most xenophyophores, including Syringammina fragilissima, are epifaunal and sessile living in the top few centimetres of the sediment (Tendal, 1972; Tendal & Lewis, 1978; Henry et al., 2014). Tendal & Lewis (1978) suggested that Syringammina species were suspension feeders using a network of pseudopodia (arm-like projections) within the test cavity to filter passing particulates. Direct evidence for feeding is limited but Laureillard et al. (2004) concluded that Syringammina corbicula were selective suspension feeders that accumulated bacteria in their 'stercomare' as a possible food reserve. The species has been documented on various sediment types and grain sizes (Henry et al., 2014). Tendal & Lewis (1978) found that a New Zealand species Syringammina tasmanesis was unselective with grain type, constructing their test with the same sediment (in terms of grain size and composition) it was living on. Tendal & Lewis (1978) suggested that current velocities reached up to 0.35 m/s in areas colonized by Syringammina tasmanensis in New Zealand. However, Ashford et al. (2004) concluded that hydrographic parameters were the least important in their habitat suitability model for xenophyophores. 

Sensitivity assessment. A decrease at the benchmark level (0.1-0.2 m/s) is unlikely to have a significant effect on the normal high flow rates that this biotope experiences, and as some xenophyophores are known to occur in areas of higher flow rates (Tendal & Lewis, 1978) then an increase is unlikely to be detrimental. For example, water flow in the Rockall Trough is probably dominated by mass water transport due to oceanic currents, for example, the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012), except near Feni Ridge or Anthon Dohrn seamount which are also influenced by tidal oscillation (as above). However, no information on water flow rates in examples of this biotope was available Therefore, there is 'Insufficient evidence' on which to base an assessment. Further evidence is required. 

Insufficient evidence (IEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
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Emergence regime changes [Show more]

Emergence regime changes

Benchmark.  1) A change in the time covered or not covered by the sea for a period of ≥1 year or 2) an increase in relative sea level or decrease in high water level for ≥1 year. Further detail

Evidence

XenCom.SyrFra biotopes are found at middle and lower bathyal depths and will not be affected by changes in the emergence regime.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Wave exposure changes (local) [Show more]

Wave exposure changes (local)

Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail

Evidence

XenCom.SyrFra biotopes are found at middle and lower bathyal depths and will not be affected by changes in nearshore wave exposure.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help

Chemical Pressures

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ResistanceResilienceSensitivity
Transition elements & organo-metal contamination [Show more]

Transition elements & organo-metal contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

The cytoplasm of xenophyophores characteristically contains barite crystals (barium sulphate) called 'granellae' (Tenday, 1972, 1996; Levin & Thomas, 1988). Voltski et al. (2018) noted that xenophyophores can accumulate other metals such as mercury, lead and uranium (see radionuclides below). Voltski et al. (2018) reported that the granellae of Syringammina limosa were composed of silicon, aluminium, and iron salts or barite depending on the specimen and that the different types of crystal had different shapes. The roles of granellae remain unknown (Tenday, 1972; Levin & Thomas, 1988; Voltski et al., 2018).  However, no evidence of adverse effects of metals on xenophyophores was found. 

Insufficient evidence (IEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
Help
Hydrocarbon & PAH contamination [Show more]

Hydrocarbon & PAH contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

No evidence could be found for the effects of hydrocarbon contaminants on Syringammina fragilissima.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
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No evidence (NEv)
NR
NR
NR
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Synthetic compound contamination [Show more]

Synthetic compound contamination

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

No evidence could be found for the effects of synthetic compound contaminants on Syringammina fragilissima.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
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Radionuclide contamination [Show more]

Radionuclide contamination

Benchmark. An increase in 10µGy/h above background levels. Further detail

Evidence

Domanov et al. (2018) demonstrated that the abundance of non-calcareous benthic foraminifera was associated with higher natural abundances of radionuclides (238U, 232Th and 226Ra) in the sediment of the Sea of Okhotsk. Swinbanks & Shirayama (1986) also reported that the xenophyophore Occultammina profunda accumulated naturally occurring radioactive lead (210Pb) in its test, together with radium (226Ra) in its granellae crystals due to its association with barite. Swinbanks & Shirayama (1986)  suggested that the high radioactivity burden was likely to which is likely to cause genetic mutations. However, the association and incorporation of radionuclides in Syringammina fragilissima has not been reported and no evidence of adverse effects in xenophyophores was found. 

Insufficient evidence (IEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
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Introduction of other substances [Show more]

Introduction of other substances

Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

Evidence

No evidence could be found for the effects of 'other' contaminants on Syringammina fragilissima.

No evidence (NEv)
NR
NR
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Not relevant (NR)
NR
NR
NR
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No evidence (NEv)
NR
NR
NR
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De-oxygenation [Show more]

De-oxygenation

Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail

Evidence

Ashford et al. (2004) concluded that depth, oxygen parameters, carbon chemistry, nitrate concentration and temperature were the most important parameters affecting xenophyophore distribution while hydrographic parameters were the least important in their habitat suitability model. Ashford et al. (2014) noted that high habitat suitability for xenophyophores as a group occurred at nitrate concentrations of ca 12.5 to 29.2 μmol/l and above 38.0 μmol/l, and oxygen saturations between 6.6% and 42.6%, between 69.2% and 74.3% and between 82.1% and 90.0%; the different peaks due to the range of species included in the model. However, oxygen saturation did not contribute to the peak habitat suitability parameters for Syringammina fragilissima, which were a depth between ca 870 and 1180 m, a calcite saturation state of between ca 2.6 and 3.4, and a temperature of between 5.3 and 7.7°C.

Henry et al. (2014) reported that Syringammina fragilissima was more frequent on the slopes of the Hebrides Terrace Seamount in areas shallower (1,000 to 1,500 m) areas with a higher oceanographic variability, where oxygen saturation was 74.56+/-3.63% (ca 6.2 mg/l) than in deeper waters (>1,550 m) at 77.8+/-1.35% (ca 6.4 mg/l). The lowest oxygen saturation in their study was 68% (ca 5.6 mg/l) recorded at 1,000 m. However, oxygen concentration was not the only variable determining its abundance. 

Sensitivity assessment. In the deep sea, the oxygen concentration is probably determined by the mass water transport such as the Eastern North Atlantic Water and Wyville Thomas Ridge Overflow Water which demarks the oxygen range documented by Henry et al. (2014). However, Ashford et al.'s model (2014) suggests that oxygen saturation is not a significant determinant of habitat suitability in Syringammina fragilissima as in other xenophyphores. No evidence of the effects of hypoxia (<=2 mg/l or ca 24% oxygen saturation) on Syringammina fragilissima was found. 

Insufficient evidence (IEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Insufficient evidence (IEv)
NR
NR
NR
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Nutrient enrichment [Show more]

Nutrient enrichment

Benchmark. Compliance with WFD criteria for good status. Further detail

Evidence

Ashford et al. (2004) concluded that depth, oxygen parameters, carbon chemistry, nitrate concentration and temperature were the most important parameters affecting xenophyophore distribution while hydrographic parameters were the least important in their habitat suitability model. Ashford et al. (2014) noted that high habitat suitability for xenophyophores occurred at relatively high nitrate concentrations of ca 12.5 to 29.2 μmol/l and above 38.0 μmol/l.  However, nitrate concentration did not contribute to the peak habitat suitability parameters for Syringammina fragilissima. These nitrate concentrations correspond with the 'good' to 'poor' nutrient status for 'clear' waters under the Water Framework Directive criteria (2015) (*see benchmark) but are lower than those for 'turbid' waters. 

Sensitivity assessment. In the deep sea, the nitrate concentration is probably determined by the mass water transport such as the Eastern North Atlantic Water and Wyville Thomas Ridge Overflow Water documented by Henry et al. (2014) together with the resuspension of particulates and deposition of phytobenthos (marine snow). The range of nitrate concentrations considered suitable for xenophyophores sits within the upper and lower range of the benchmark. Hence, the community is probably 'Not sensitive' at the benchmark level, but with 'Low' confidence based on the lack of evidence on the effects of nutrient enrichment. 

High
Low
NR
NR
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High
High
High
High
Help
Not sensitive
Low
NR
NR
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Organic enrichment [Show more]

Organic enrichment

Benchmark. A deposit of 100 gC/m2/yr. Further detail

Evidence

Xenophyophores reach high densities in areas of high surface productivity and high particle flux on topographical features such as seamounts, canyons, troughs, ridges and continental slopes (Tendal, 1972; Levin & Thomas, 1988; Roberts et al., 2000; Levin & Nittrouer, 2013; Henry et al., 2014). Levin & Thomas (1988) suggested that their aggregation on raised seafloor features or on continental slopes where water flow was adequate to transport particulates or the concentration of suspended sediment supported suspension feeding. Most xenophyophores, including Syringammina fragilissima, are epifaunal and sessile living in the top few centimetres of the sediment (Tendal, 1972; Tendal & Lewis, 1978; Henry et al., 2014). Tendal & Lewis (1978) suggested that Syringammina species were suspension feeders using a network of pseudopodia (arm-like projections) within the test cavity to filter passing particulates. Direct evidence for feeding is limited but Laureillard et al. (2004) concluded that Syringammina corbicula were selective suspension feeders that accumulated bacteria in their 'stercomare' as a possible food reserve. 

Sensitivity assessment. Their abundance in areas of high surface productivity and high particle flux suggests they require a constant supply of organic matter. They may benefit from organic enrichment through upwelling and the seasonal deposition of phytobenthos. However, no quantitative values were available for comparison with the benchmark. Therefore, resistance is assessed as 'High', resilience as 'High' and sensitivity assessed as 'Not sensitive' but with 'Low' confidence. 

High
Low
NR
NR
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High
High
High
High
Help
Not sensitive
Low
NR
NR
Help

Physical Pressures

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ResistanceResilienceSensitivity
Physical loss (to land or freshwater habitat) [Show more]

Physical loss (to land or freshwater habitat)

Benchmark. A permanent loss of existing saline habitat within the site. Further detail

Evidence

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of available habitat (resilience is ‘Very low’). The squat lobster assemblage biotopes are therefore considered to have ‘High’ sensitivity to this pressure.

None
High
High
High
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Very Low
High
High
High
Help
High
High
High
High
Help
Physical change (to another seabed type) [Show more]

Physical change (to another seabed type)

Benchmark. Permanent change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa. Further detail

Evidence

Change from sedimentary to hard substrata would cause loss of the biotope. In addition, the mechanical process of changing to a hard substratum would destroy any characterizing organisms present and ultimately result in the loss and reclassification of the biotope. Therefore, resistance is assessed as 'None'. Therefore, as this pressure is considered a permanent change, resilience is assessed as 'Very Low', and sensitivity is assessed as 'High'.

None
High
High
High
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Very Low
High
High
High
Help
High
High
High
High
Help
Physical change (to another sediment type) [Show more]

Physical change (to another sediment type)

Benchmark. Permanent change in one Folk class (based on UK SeaMap simplified classification). Further detail

Evidence

Xenophyophores reach high densities in areas of high surface productivity and high particle flux on topographical features such as seamounts, canyons, troughs, ridges and continental slopes (Tendal, 1972; Levin & Thomas, 1988; Roberts et al., 2000; Levin & Nittrouer, 2013; Henry et al., 2014). Levin & Thomas (1988) suggested that their aggregation on raised seafloor features or on continental slopes where water flow was adequate to transport particulates or the concentration of suspended sediment supported suspension feeding. Syringammina fragilissima has been reported from various substrata, for example, detrital sandy mud (Tendal, 1972; Tendal & Lewis, 1978); muddy sediments (Roberts et al., 2000); quartz sand overlying glacigenic mud (Hughes & Gooday, 2004) and, cobbles and sands (Henry et al., 2014).

Sensitivity assessment. Syringammina fragilissima is recorded from various sediment types in areas of high particulate flux. The XenCom.SyrFra group of biotopes are characterized by muds, coarse, and mixed substrata and, therefore, cover the full range of the Folk classification (Long, 2006).  For example, the permanent change in the substratum from mud to coarse sediment would result in the reclassification of the Mu.XenCom.SyrFra biotope as a Co.XenCom.SyrFra biotope but would probably not affect the xenophyophore dominated community.  Hence, resistance is probably 'High', resilience 'High' and sensitivity to this pressure in this group of XenCom.SyrFra biotopes is assessed as 'Not sensitive'. 

 

High
High
High
High
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High
High
High
High
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Not sensitive
High
High
High
Help
Habitat structure changes - removal of substratum (extraction) [Show more]

Habitat structure changes - removal of substratum (extraction)

Benchmark. The extraction of substratum to 30 cm (where substratum includes sediments and soft rock but excludes hard bedrock). Further detail

Evidence

Syringammina fragilissima is an epibenthic species living on the surface of the sediment.  Therefore, substratum removal at the benchmark level would destroy the biotope within the affected area. Therefore, sensitivity is assessed as 'None', resilience as 'Medium' and sensitivity as 'Medium'. 

None
Low
NR
NR
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Medium
Low
NR
NR
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Medium
Low
NR
NR
Help
Abrasion / disturbance of the surface of the substratum or seabed [Show more]

Abrasion / disturbance of the surface of the substratum or seabed

Benchmark. Damage to surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

Agglutinated xenophyophore tests are extremely fragile and break up in a trawl or dredge (Roberts et al.,  2000). They are composed of materials from the surrounding sediment, e.g. fine sediment particles and dead foraminifera tests (Tendal, 1972, 1979; Hughes & Gooday, 2004). Hughes & Gooday (2004) collected four empty (dead) Syringammina fragilissima tests from the Darwin Mounds that ranged from 3 to 5 cm across. They noted that the largest recorded specimen was 10 cm in diameter but that this specimen was probably trimmed by the core tube (Lamont, 1998, cited in Hughes & Gooday, 2004). Hughes & Gooday (2004) described the test as friable, slightly eroded, with substantial amounts of mud trapped between the branches. Brady (1883) described the test as fragile, composed of fine sand, without sufficient strength to bear handling without injury. In addition, corers and trawls used to recover xenophyophores have broken tests beyond recognition, or blown them into fragments from the pressure wave at the front of the camera sledge (Hughes & Gooday, 2004; Henry et al., 2014).

Sensitivity assessment. The fragility of xenophyophore tests suggests that they are likely to be removed and damaged by surface abrasion due to passing fishing gear.  However, no information on the survival of the host plasmodium inside the test was found but their tissue may well be damaged or destroyed in the process. Therefore, resistance within the affected area is assessed as 'None', resilience as 'Medium' and sensitivity assessed as 'Medium', albeit with 'Low' confidence due to the lack of direct evidence. 

None
Low
NR
NR
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Medium
Low
NR
NR
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Medium
Low
NR
NR
Help
Penetration or disturbance of the substratum subsurface [Show more]

Penetration or disturbance of the substratum subsurface

Benchmark. Damage to sub-surface features (e.g. species and physical structures within the habitat). Further detail

Evidence

Agglutinated xenophyophore tests are extremely fragile and break up in a trawl or dredge (Roberts et al.,  2000). They are composed of materials from the surrounding sediment, e.g. fine sediment particles and dead foraminifera tests (Tendal, 1972, 1979; Hughes & Gooday, 2004). Hughes & Gooday (2004) collected four empty (dead) Syringammina fragilissima tests from the Darwin Mounds that ranged from 3 to 5 cm across. They noted that the largest recorded specimen was 10 cm in diameter but that this specimen was probably trimmed by the core tube (Lamont, 1998, cited in Hughes & Gooday, 2004). Hughes & Gooday (2004) described the test as friable, slightly eroded, with substantial amounts of mud trapped between the branches. Brady (1883) described the test as fragile, composed of fine sand, without sufficient strength to bear handling without injury. In addition, corers and trawls used to recover xenophyophores have broken tests beyond recognition, or blown them into fragments from the pressure wave at the front of the camera sledge (Hughes & Gooday, 2004; Henry et al., 2014).

Sensitivity assessment. The fragility of xenophyophore tests suggests that they are likely to be removed and damaged by passing fishing gear.  However, no information on the survival of the host plasmodium inside the test was found but their tissue may well be damaged or destroyed in the process. Therefore, resistance within the affected area is assessed as 'None', resilience as 'Medium' and sensitivity assessed as 'Medium', albeit with 'Low' confidence due to the lack of direct evidence. 

None
Low
NR
NR
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Medium
Low
NR
NR
Help
Medium
Low
NR
NR
Help
Changes in suspended solids (water clarity) [Show more]

Changes in suspended solids (water clarity)

Benchmark. A change in one rank on the WFD (Water Framework Directive) scale e.g. from clear to intermediate for one year. Further detail

Evidence

Xenophyophores reach high densities in areas of high surface productivity and high particle flux on topographical features such as seamounts, canyons, troughs, ridges and continental slopes (Tendal, 1972; Levin & Thomas, 1988; Roberts et al., 2000; Levin & Nittrouer, 2013; Henry et al., 2014). Levin & Thomas (1988) suggested that their aggregation on raised seafloor features or on continental slopes where water flow was adequate to transport particulates or the concentration of suspended sediment supported suspension feeding. Levin & Thomas (1988) also noted their abundance declined where water flow was high enough to mobilise the sediment or form ripples on the seabed. Henry et al. (2014) suggested that the enhanced frequency of Syringammina fragilissima in oceanographically variable flanks of the Hebrides Terrace Seamount, at 1,000-1,500 m, was probably due to the greater range of particulate attenuation coefficients (0.14+/-0.06 /m at 1,200 to 1,500 m; a measure of turbidity) than in deeper waters. 

Most xenophyophores, including Syringammina fragilissima, are epifaunal and sessile living in the top few centimetres of the sediment (Tendal, 1972; Tendal & Lewis, 1978; Henry et al., 2014). Tendal & Lewis (1978) suggested that Syringammina species were suspension feeders using a network of pseudopodia (arm-like projections) within the test cavity to filter passing particulates. 

Sensitivity assessment. The abundance of Syringammina fragilissima is probably dependent on the availability of suspended particulates for feeding and growth. Therefore, a decrease in suspended sediments may reduce the growth and density of the population. Hence, resistance is assessed as 'Low', resilience as 'High' and sensitivity as 'Low', albeit with 'Low' confidence due to the lack of direct evidence to compare against the benchmark. 

Low
Low
NR
NR
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High
Low
NR
NR
Help
Low
Low
NR
NR
Help
Smothering and siltation rate changes (light) [Show more]

Smothering and siltation rate changes (light)

Benchmark. ‘Light’ deposition of up to 5 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

The eruption of Mt Pinatubo in June 1991 deposited an 8 to 9 cm layer of ash across the deep seafloor of the South China Sea (Hess & Kuhnt, 1996; Hess et al., 2001). The ash layer caused the mass mortality of benthic foraminifera in the affected area, which has not recovered three years after the eruption (Hees & Kuhnt, 1996). Hess et al. (2001) reported that xenophyophores (possibly Syringammina (?) fragilissima) were absent from the benthos in 1994 after the June 1991 Mt Pinatubo ashfall, were rare by June 1996 but were important recolonizers and occurred in large numbers in December 1996 and summer 1998, ca. five years after deposition. However, it is unclear if they were part of the benthic foraminifera community before the ashfall. The mass mortality of benthic forams suggests that xenophyophores could be similarly affected. Therefore, resistance to the sudden deposition of 5 cm of fine sediment (see benchmark) is assessed as 'Low', resilience as 'High' and sensitivity as 'Low' but with 'Low' confidence due to the lack of direct evidence of mortality in the characteristic species. 

Low
Low
NR
NR
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High
Low
NR
NR
Help
Low
Low
NR
NR
Help
Smothering and siltation rate changes (heavy) [Show more]

Smothering and siltation rate changes (heavy)

Benchmark. ‘Heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Further detail

Evidence

The eruption of Mt Pinatubo in June 1991 deposited an 8 to 9 cm layer of ash across the deep seafloor of the South China Sea (Hess & Kuhnt, 1996; Hess et al., 2001). The ash layer caused the mass mortality of benthic foraminifera in the affected area, which has not recovered three years after the eruption (Hees & Kuhnt, 1996). Hess et al. (2001) reported that xenophyophores (possibly Syringammina (?) fragilissima) were absent from the benthos in 1994 after the June 1991 Mt Pinatubo ashfall, were rare by June 1996 but were important recolonizers and occurred in large numbers in December 1996 and summer 1998, ca. five years after deposition. However, it is unclear if they were part of the benthic foraminifera community before the ashfall. The mass mortality of benthic forams suggests that xenophyophores could be similarly affected. Therefore, resistance to the sudden deposition of 30 cm of fine sediment (see benchmark) is assessed as 'Low', resilience as 'High' and sensitivity as 'Low' but with 'Low' confidence due to the lack of direct evidence of mortality in the characteristic species. 

Low
Low
NR
NR
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High
Low
NR
NR
Help
Low
Low
NR
NR
Help
Litter [Show more]

Litter

Benchmark. The introduction of man-made objects able to cause physical harm (surface, water column, seafloor or strandline). Further detail

Evidence

Not assessed. 

Not Assessed (NA)
NR
NR
NR
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Not assessed (NA)
NR
NR
NR
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Not assessed (NA)
NR
NR
NR
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Electromagnetic changes [Show more]

Electromagnetic changes

Benchmark. A local electric field of 1 V/m or a local magnetic field of 10 µT. Further detail

Evidence

No evidence was found on the effects of electromagnetic changes on Syringammina fragilissima.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
Underwater noise changes [Show more]

Underwater noise changes

Benchmark. MSFD indicator levels (SEL or peak SPL) exceeded for 20% of days in a calendar year. Further detail

Evidence

No direct evidence could be found for the effects of noise on Syringammina fragilissima. However, pressure waves caused by scientific camera sledges can blow xenophyophores into fragments (Tendal & Gooday, 1981), which suggests that Syringammina fragilissima may be damaged by intense vibration. 

No evidence (NEv)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
Introduction of light or shading [Show more]

Introduction of light or shading

Benchmark. A change in incident light via anthropogenic means. Further detail

Evidence

No evidence could be found for the effects of anthropogenic light changes on Syringammina fragilissima. These biotopes are characterized by xenophyophores with limited ability to detect light and are aphotic.  

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Barrier to species movement [Show more]

Barrier to species movement

Benchmark. A permanent or temporary barrier to species movement over ≥50% of water body width or a 10% change in tidal excursion. Further detail

Evidence

The mobility of xenophyophores is unknown but probably limited and dispersal is probably dependent on their flagellate gametes. Physical and hydrographic barriers may limit the dispersal of larvae but larval dispersal is not considered under the pressure definition and benchmark.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Death or injury by collision [Show more]

Death or injury by collision

Benchmark. Injury or mortality from collisions of biota with both static or moving structures due to 0.1% of tidal volume on an average tide, passing through an artificial structure. Further detail

Evidence

The XenCom.SyrFra group of biotopes are characterized by xenophyophores that are not at risk of collision with artificial structures. The biotopes might be adversely affected by large falling marine debris such as barrels, containers, and even shipwrecks but the effects are probably addressed under 'abrasion' above. 

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
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Visual disturbance [Show more]

Visual disturbance

Benchmark. The daily duration of transient visual cues exceeds 10% of the period of site occupancy by the feature. Further detail

Evidence

No evidence could be found for the effects of visual disturbance changes on Syringammina fragilissima. These biotopes are characterized by xenophyophores with no visual organelles and are aphotic.  

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
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Biological Pressures

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ResistanceResilienceSensitivity
Genetic modification & translocation of indigenous species [Show more]

Genetic modification & translocation of indigenous species

Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail

Evidence

Xenophyophores occur below 500 m in the deep sea are unlikely to be subject to translocation or genetic modification. 

Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Introduction or spread of invasive non-indigenous species [Show more]

Introduction or spread of invasive non-indigenous species

Benchmark. The introduction of one or more invasive non-indigenous species (INIS). Further detail

Evidence

No evidence could be found for the effects of Introduction or spread of non-indigenous species on Syringammina fragilissima.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
Introduction of microbial pathogens [Show more]

Introduction of microbial pathogens

Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail

Evidence

No evidence could be found for the effects of microbial pathogen introduction on Syringammina fragilissima.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
Removal of target species [Show more]

Removal of target species

Benchmark. Removal of species targeted by fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Syringammina fragilissima is not a commercially or recreationally targeted species.

Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
Removal of non-target species [Show more]

Removal of non-target species

Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

Evidence

Agglutinated xenophyophore tests are extremely fragile and break up in a trawl or dredge (Roberts et al.,  2000). They are composed of materials from the surrounding sediment, e.g. fine sediment particles and dead foraminifera tests (Tendal, 1972, 1979; Hughes & Gooday, 2004). Hughes & Gooday (2004) collected four empty (dead) Syringammina fragilissima tests from the Darwin Mounds that ranged from 3 to 5 cm across. They noted that the largest recorded specimen was 10 cm in diameter but that this specimen was probably trimmed by the core tube (Lamont, 1998, cited in Hughes & Gooday, 2004). Hughes & Gooday (2004) described the test as friable, slightly eroded, with substantial amounts of mud trapped between the branches. Brady (1883) described the test as fragile, composed of fine sand, without sufficient strength to bear handling without injury. In addition, corers and trawls used to recover xenophyophores have broken tests beyond recognition, or blown them into fragments from the pressure wave at the front of the camera sledge (Hughes & Gooday, 2004; Henry et al., 2014).

Sensitivity assessment. The fragility of xenophyophore tests suggests that they are likely to be removed and damaged by trawls or other fishing gear designed to remove or capture other seabed species. However, no information on the survival of the host plasmodium inside the test was found but their tissue may well be damaged or destroyed in the process. Gooday et al. (2017) also noted that xenophyophores were an important part of the abyssal megafauna on the Pacific Clarion-Clipperton Zone targeted by seabed mining for polymetallic nodules, especially species that attach to the nodules. Therefore, resistance within the affected area is assessed as 'Low', resilience as 'High' and sensitivity assessed as 'Low', albeit with 'Low' confidence due to the lack of direct evidence. 

Low
Low
NR
NR
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High
Low
NR
NR
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Low
Low
NR
NR
Help

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Citation

This review can be cited as:

Bull, G., & Tyler-Walters, H., 2024. Syringammina fragilissima field on Atlantic lower bathyal mud. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 22-06-2024]. Available from: https://www.marlin.ac.uk/habitat/detail/1283

Last Updated: 04/04/2024