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Reteporella and Axinellid sponges on Atlantic upper bathyal rock and other hard substrata

Distribution MapBIO Map Legend

Summary

UK and Ireland classification

Description

This biotope occurs on cobbles and pebbles on sandy seabed possibly associated with shallow iceberg plough marks. It is characterized by Axinellid and massive lobose sponges, cup sponges and the bryozoan Reteporella attached to the cobbles, with squat lobsters sheltering under the cobbles. It is similar to a deeper expression of the shallower biotope “deep sponge communities (circalittoral)". 

Depth range

200-600 m

Additional information

-

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

This biotope occurs in the Atlantic upper bathyal zone on cobbles and pebbles on top of sand. The biotope is characterized by Axinella infundibuliformis (cup-shaped sponge) and bryozoans from the genus Reteporella. Other species present in the assemblage may include Munida, encrusting Porifera, massive lobose Porifera, and Zoantharia. 

The important characterizing species are the focus for the sensitivity assessment, as the loss of these species and/or change in substrata will result in a change of biotope. Much of the information on Axinellid sponge sensitivity has been taken from the sensitivity assessment of ‘deep sponge communities’ by Readman (2018) but has been supplemented with additional (i.e. more recent) evidence where possible.

Resilience and recovery rates of habitat

In the UK, Reteporella and Axinellid sponge assemblages are only known to occur on Rockall Bank (JNCC, 2015).  Reteporella spp. sexually reproduce by consecutive embryonic incubation, producing a few large lecithotrophic larvae as opposed to numerous, small planktotrophic larvae (Ostrovsky et al., 2009). Eggs are fertilized internally and brooded until the larvae are released. Only one study was available that could be used to assess the resilience of Reteporella. Casoli et al. (2020b) recorded the re-colonization of bare coralligenous reefs impacted by Costa Concordia shipwreck, off the coast of Tuscany (Italy). After sinking in January 2012, the Costa Concordia was re-floated and removed in July 2014. This process, which occurred over two years (2013-2014) caused the dispersion of fine sediments and debris. Iron structures and grout bags (filled with cement) were also placed at 22 m and 55 m deep to stabilize the bottom of the boat. Throughout 2015 a clean-up operation was conducted, removing fine sediments, debris and man-made structures from the seabed. This included the removal of 25,000 t of grout and the cleaning of 86,000 m2 of the seabed. Two areas affected and two control areas were surveyed in 2017 and again in 2019. Reteporella colonies were not present at impacted sites in 2017 but were present in 2019. Large-sized Reteporella colonies were found exclusively at impacted sites, where settlement and growth patterns differed from the control sites. Casoli et al. (2020b) estimated that Reteporella colonies at the impacted site had a mean growth rate (in width) of 4.3 cm/year. Casoli et al. (2020b) concluded that Reteporella settlement occurred during the early phase of community development, after early pioneers but before slow-growing species.

Axinellid sponges are oviparous and gonochoric. Idan et al. (2020) was the first description of the reproduction cycle in Axinellid sponges, more specifically, shallow-water (28-32 m) and mesophotic (95-120 m) populations of Axinella polypoides off the Israeli coast. The mesophotic populations reproduced sexually year-round and showed no seasonality. In contrast, the shallow-water population reproduced sexually in a seasonal pattern, linked closely with seasonal temperature changes. The results suggested that the mesophotic population invested more in sexual reproduction than the shallow water population. Nutrient availability does not account for this difference in the different habitats. Instead, Idan et al. (2020) concluded that the stability of the mesophotic environment could provide and allow a surplus of energy to be spent on continual sexual reproduction. Asexual reproduction by fragmentation is widely observed in Porifera. Fragments of Axinella polypoides do not seem to re-attach to substrata and, therefore, it does not appear well suited to asexual reproduction (Idan et al., 2020). This may explain the strong emphasis and energy commitments on continual sexual reproduction in the mesophotic population.  Monitoring studies at Lundy (Hiscock, 1994; Hiscock, 2003; Hiscock, pers comm) suggested that growth the of Axinella dissimilis (as Axinella polypoides) was no more than about 2 mm a year (up to a height of ca 30 cm) and that all branching sponges included in photographic monitoring over four years exhibited very little or no growth over the study.  In addition, no recruitment of Axinellia dissimilis or Axinellia infundibuliformis was observed.

Resilience assessment. There is limited evidence that suggests that Reteporella colonies can recover within two years. However, given the lack of observed recovery and slow growth rates observed in some Axinellid sponges, a full recovery is unlikely to occur within 25 years (Readman, 2018). Therefore, where resistance is ‘None’, ‘Low’ or ‘Medium’, resilience is assessed as ‘Very low’, albeit it with ‘Low’ confidence. 

Hydrological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Medium Very Low Medium
Q: Medium
A: Low
C: Medium
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Low
C: Medium

No direct evidence was found on the effect of changes in local temperature at the benchmark level on the biotope. The only evidence found on the temperature range of the biotope was from Graves (in prep). This study predicted the distribution of numerous deep-sea biotopes across the UK and Irish waters using habitat suitability modelling. From their biotope distribution data, Graves (in prep) characterized the thermal niche of Reteporella and Axinellid sponge assemblages across the UK and Ireland as 9.3 to 9.5°C.

There is limited direct evidence available for Reteporella spp.. Reteporella pelecanus, Reteporella mediterranea and Reteporella victori occur around the Gazul mud volcano region in the northern Gulf of Cádiz. Reteporella spp. experience temperatures ranging from 11-17°C in this area because of the influence of the Mediterranean Upper Core and the Eastern North Atlantic Central water masses, (Ramalho et al., 2020). Pentapora fascialis (Order: Cheilostomata), a shallow water (11-80 m) species, is often used as a model organism to test the effect of environmental changes on bryozoans (Casoli et al., 2020). Zooids (modular units) of bryozoan colonies originate by asexual budding. Lombardi et al. (2006) found that the longest Pentapora fascialis zooids were budded in locations characterized by low seasonal temperature variations (3.2-7.5°C; range = 4.3°C) and low mean temperature (11°C).

There is also no direct relevant evidence for Axinellid sponges relating to the pressure at the benchmark. Long-term temperature increases may cause extension of the British Isles populations and decreases in temperature may result in population shrinkage. Goodwin et al. (2013) noted increases in the abundance of Axinella damicornis and Axinella dissimilis in Northern Ireland over twenty years and suggested the increase was due to sea temperature warming. OBIS data suggested that in the UK, Axinella infundibuliformis occurs near its most southerly limit, with a northern limit in the Norwegian Sea. The bathymetric range of Axinella infundibuliformis is from coastal waters to 500 m. Although this biotope is classed as a ‘deep-sea’ biotope, it is distributed at shallower depths than the permanent thermocline, 600-1000 m (White & Dorshel, 2010), and may, therefore, experience some seasonal temperature variations, unlike most deep-sea biotopes that occur below the permanent thermocline.

Sensitivity assessment. There is evidence to suggest that Reteporella spp. can withstand changes in large seasonal changes in temperature variability (Ramalho et al., 2020), exceeding the variability at the benchmark level. There is more limited evidence available for Axinella infundibuliformis. It occurs at its southern limit in the UK, therefore, there is the potential that some loss may occur to Axinella infundibuliformis. Therefore, resistance is assessed as ‘Medium’, and resilience as ‘Very low', resulting in an overall sensitivity of ‘Medium’

Medium Very Low Medium
Q: Medium
A: Low
C: Medium
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Low
C: Medium

No direct evidence was found on the effect of changes in local temperature at the benchmark level on the biotope. The only evidence found on the temperature range of the biotope was from Graves (in prep). This study predicted the distribution of numerous deep-sea biotopes across the UK and Irish waters using habitat suitability modelling. From their biotope distribution data, Graves (in prep) characterized the thermal niche of Reteporella and Axinellid sponge assemblages across the UK and Ireland as 9.3 to 9.5°C.

There is limited direct evidence available for Reteporella spp.. Reteporella pelecanus, Reteporella mediterranea and Reteporella victori occur around the Gazul mud volcano region in the northern Gulf of Cádiz. Reteporella spp. experience temperatures ranging from 11-17°C in this area because of the influence of the Mediterranean Upper Core and the Eastern North Atlantic Central water masses, (Ramalho et al., 2020). Pentapora fascialis (Order: Cheilostomata), a shallow water (11-80 m) species, is often used as a model organism to test the effect of environmental changes on bryozoans (Casoli et al., 2020). Zooids (modular units) of bryozoan colonies originate by asexual budding. Lombardi et al. (2006) found that the longest Pentapora fascialis zooids were budded in locations characterized by low seasonal temperature variations (3.2-7.5°C; range = 4.3°C) and low mean temperature (11°C).

There is also no direct relevant evidence for Axinellid sponges relating to the pressure at the benchmark. Long-term temperature increases may cause extension of the British Isles populations and decreases in temperature may result in population shrinkage. Goodwin et al. (2013) noted increases in the abundance of Axinella damicornis and Axinella dissimilis in Northern Ireland over twenty years and suggested the increase was due to sea temperature warming. OBIS data suggested that in the UK, Axinella infundibuliformis occurs near its most southerly limit, with a northern limit in the Norwegian Sea. The bathymetric range of Axinella infundibuliformis is from coastal waters to 500 m. Although this biotope is classed as a ‘deep-sea’ biotope, it is distributed at shallower depths than the permanent thermocline, 600-1000 m (White & Dorshel, 2010), and may, therefore, experience some seasonal temperature variations, unlike most deep-sea biotopes that occur below the permanent thermocline.

Sensitivity assessment. There is evidence to suggest that Reteporella spp. can withstand changes in large seasonal changes in temperature variability (Ramalho et al., 2020), exceeding the variability at the benchmark level. There is more limited evidence available for Axinella infundibuliformis. Axinella infundibuliformis northern limit is the Norwegian Sea at 500 m deep with approximate bottom temperatures of 7.0°C (Hassel, 2020). Its northern limit, combined with known temperature distribution (9.3 to 9.5°C) of the biotope in the UK (Graves, In prep), suggests that there is the potential that some loss may occur to Axinella infundibuliformis. Therefore, resistance is assessed as ‘Medium’ and resilience as ‘Very low’, resulting in an overall sensitivity of ‘Medium’.

Low Very Low High
Q: Low
A: NR
C: NR
Q: Medium
A: Medium
C: Medium
Q: Low
A: Low
C: Low

Sensitivity assessment.  A change in salinity due to human activities may cause mortality in the characterizing species/taxa due to the relatively stable salinity conditions in the deep sea. Therefore, resistance is assessed as ‘Low’, resilience assessed as ‘Very low’ and overall sensitivity as ‘High’.

Low Very Low High
Q: Low
A: NR
C: NR
Q: Medium
A: Medium
C: Medium
Q: Low
A: Low
C: Low

Sensitivity assessment. .  A change in salinity due to human activities may cause mortality in the characterizing species/taxa due to the relatively stable salinity conditions in the deep sea. Therefore, resistance is assessed as ‘Low’, resilience assessed as ‘Very low’ and overall sensitivity as ‘High’.

High High Not sensitive
Q: Low
A: NR
C: NR
Q: Medium
A: Medium
C: Medium
Q: Low
A: Low
C: Low

There is limited, direct evidence available to assess the sensitivity of either Reteporella colonies or Axinellid sponges at the benchmark level. The presence of sand within the biotope suggests that mean current flow cannot exceed 0.15 m/s (Earle, 2019). Furthermore, model data suggests that the bottom flow around Rockall Bank at 200 m is 0.06 m/s (Howell et al., 2009). However, Reteporella beaniana has been observed occurring on Lophelia pertusa rubble at Mingulay Reef (Kazanidis & Witte, 2016) where strong currents are present (up to 0.60 m/s) because of the presence of internal waves (Davies et al., 2009). In the case of Axinellid sponges, Axinella spp. have been recorded in biotopes that experience moderate to very weak flow (0-1.5 m/s) (Conner et al., 2004).

Sensitivity assessment. This biotope occurs in a low flow environment (<0.1 m/s) but both Reteporella spp. and Aninella spp. have been observed in environments characterized by flows that exceed that at the benchmark level. However, a decrease in flow may result in the deposition of fine sediments and the burial of the pebbles and cobbles on which the biotope depends. In addition, an increase in water flow may winnow away fine sediment (e.g. sand), increase access to cobble and pebble surfaces where present, and provide additional substratum for the bryozoans and sponges. Therefore, a decrease in water flow might result in loss of substratum and smothering of the biotope so that resistance is assessed as ‘Medium albeit with ‘Low’ confidence. Hence, resilience is assessed as ‘Very low’ and overall sensitivity as ‘Medium’

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Reteporella and Axinellid sponge assemblages are found at upper bathyal depths; therefore, they will not be impacted by a change in emergence. Hence, this pressure is assessed as ‘Not relevant’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Reteporella and Axinellid sponge assemblages are found at upper bathyal depths; therefore, they will not be affected by changes in nearshore wave exposure and the biotopes are assessed as ‘Not relevant’.

Chemical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

‘No evidence’ was found.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

Medium Very Low Medium
Q: Medium
A: Low
C: Low
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Low
C: Low

In general, respiration in most marine invertebrates does not appear to be significantly affected until extremely low concentrations are reached. For many benthic invertebrates, this concentration is about 2 ml/l (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995). Cole et al. (1999) suggested possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l.

Hiscock & Hoare (1975) reported an oxycline forming in the summer months (Jun-Sep) in a quarry lake (Abereiddy, Pembrokeshire) from close to full oxygen saturation at the surface to <5% saturation below ca 10 m. No Tethya citrina Kirchenpaueria pinnata, Hymeniacidon pereleve, Polymastia boletiformis or Ascidia mentula were recorded at depths below 10 - 11 m.  Demosponges maintained under laboratory conditions can tolerate hypoxic conditions for brief periods. Gunda & Janapala (2009) investigated the effects of variable oxygen levels on the survival of the marine sponge, Haliclona pigmentifera. Under hypoxic conditions (1.5-2.0 ppm O2), Haliclona pigmentifera with intact ectodermal layers and subtle oscula survived for 42 ± 3 days.  Sponges with prominent oscula, foreign material, and damaged pinacoderm exhibited poor survival (of 1-9 days) under similar conditions. Complete mortality of the sponges occurred within 2 days under anoxic conditions (<0.3 ppm O2).

Sensitivity assessment. Whilst some sponges have demonstrated tolerance to short-term hypoxic events, others were excluded below the oxycline at Abereiddy Quarry (Hiscock & Hoare, 1975).  Therefore, some members of the community may be lost and a precautionary resistance assessment of ‘Medium’ is suggested, albeit with ‘Low’ confidence.  Resilience is ‘Very Low’ and sensitivity is, therefore ‘Medium’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Nutrient availability will be important to this biotope (M.AtUB.Ro.DeeSpo.RetAxi), however, no evidence was found on the effect of nutrient enrichment on the biotope. Therefore, this pressure is recorded as ‘No evidence’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

As suspension feeders, particulate organic matter (POM) is a food source for the species and taxa that characterize this biotope. However, no evidence was found on the effect of organic enrichment at the level of the benchmark on the biotope. Therefore, ‘No evidence’ is recorded.

Physical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

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’). This biotope (M.AtUB.Ro.DeeSpo.RetAxi) is, therefore, considered to have ‘High’ sensitivity to this pressure.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

This biotope (M.AtUB.Ro.DeeSpo.RetAxi) is characterized by hard rock (cobbles and pebbles) substrata (JNCC, 2015) and is required for the successful settlement of the characterizing species/taxa. If the hard rock (cobbles and pebbles) were replaced by a soft rock or purely sedimentary substrata, this would represent a fundamental change to the physical characteristics of the biotope, whilst also removing suitable habitat.

Sensitivity assessment. Resistance is assessed as ‘None’, resilience as ‘Very low’ and overall sensitivity as ‘High’

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

This biotope (M.AtUB.Ro.DeeSpo.RetAxi) is characterized by hard rock (cobbles and pebbles). A change in seabed type to anything but cobble or pebble dominated coarse substrata at the benchmark level would result in the loss of hard substrata. This would permanently change the characterizing substrata and represent a loss of suitable habitat for the characterizing species to settle on. Therefore, resistance is assessed as ‘None’, resilience as ‘Very low’ and overall sensitivity assessed as ‘High’.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Reteporella spp. and Axinellid sponges are sessile species. Removal of the substratum at the benchmark level would destroy the biotope within the affected area. Therefore, resistance is assessed as ‘None’, resilience is assessed as ‘Very low’ and overall sensitivity as ‘High’

Low Very Low High
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium

The main sources of potential abrasion and disturbance relevant to Reteporella spp. and Axinellid sponges are from bottom fishing (e.g. beam trawls), deep-sea mining activity (e.g. mining vehicles) and from anchoring or positioning of offshore structures. Reteporella spp. are very fragile structures that makes them sensitive to mechanical disturbances (Casoli et al., 2020a; Casoli et al., 2020b), such as abrasion. When picking and sorting samples from Van Veen grabs, Remalho et al. (2020) removed Reteporella colonies before the sieving process as, because of their fragile structure, the process of sieving (abrasion, friction)  would severely damage the specimens. Reteporella colonies have also been recorded in scientific trawls (Figuerola et al., 2018).

Branching and cup-like Axinellid sponges are not as fragile as Reteporella. Axinella infundibuliformis is moderately firm and resilient but pieces break off if bent through 90° (Ackers et al., 1992). Axinella dissimilis is quite elastic and flexible (Moss & Ackers, 1982). However, if the sponge is bent through more than 90°, the surface will crack (Ackers et al., 1992). Axinella dissimilis is known to be susceptible to towed fishing gears (Hiscock, 2014). Hinz et al. (2011) studied the effects of scallop dredging in Lyme Bay, UK and found that the presence of Axinella dissimilis was significantly higher at non-fished sites (33% occurrence) compared to fished sites (15% occurrence). Kędra et al. (2017) also observed that Axinella infundibuliformis was absent from trawled areas but present in untrawled areas.

Sensitivity assessment. No direct experimental evidence on the effects of abrasion of Reteporella colonies and Axinellid sponges were found. However, the fragile structure of Reteporella, along with the comparative studies between trawled and untrawled areas indicate that abrasion and disturbance by bottom trawling can reduce abundance or completely remove Axinellid sponges. In addition, the characteristic species occur attached to cobbles and pebbles, which are likely to be overturned, displaced or removed by bottom trawling. For example, Picton & Goodwin (2007) noted that an area of boulders with a rich fauna of sponges and hydroids on the east coast of Rathlin Island, Northern Ireland was significantly altered since the 1980s. Scallop dredging had begun in 1989 and boulders were observed to have been turned and the gravel harrowed. Also, many of the boulders had disappeared and rare hydroid communities were greatly reduced (Picton & Goodwin, 2007). Prior records indicated the presence of large sponges, mainly Axinella infundibuliformis (Picton & Goodwin, 2007). Therefore, resistance is assessed as ‘Low’, resilience as ‘Very low’ and overall sensitivity as ‘High’

Low Very Low High
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium

Penetration and/or disturbance of the substratum would result in similar, if not identical, results as an abrasion and/or disturbance of the substratum on the surface of the seabed (see abrasion/disturbance above).  Therefore, resistance has been assessed as ‘Low’, resilience assessed as ‘Medium’, and overall sensitivity of ‘Medium’.

High High Not sensitive
Q: High
A: Medium
C: Low
Q: High
A: High
C: High
Q: High
A: Medium
C: Low

Suspended solids are important to all the characterizing species and taxa of this biotope, because they are filter feeders. As a result, these species/taxa are reliant upon currents transporting food items, e.g. nanoplankton (Kazanidis & Witte, 2016), to them for capture. An increase in suspended solids may increase the food supply to organisms. On the other hand, a decrease in suspended solids may see a reduction in available food. Too much suspended sediment may also clog feeding appendages and, if combined with high-energy environments, cause damage and injury to organisms.

No direct evidence was found to assess the pressure at the benchmark. However, long-term observations of Mesco Reef, off the Ligurian coast (Italy) recorded changes in Reteporella grimaldii cover with changes in turbidity levels. Between 1961 and 2008, the cover of Reteporella grimaldii increased despite a rise in human pressure that, in turn, increased in turbidity (Gatti et al., 2016). Coastal works (e.g. construction of embankments, groynes, breakwaters and sea walls) were probably responsible for the increase in turbidity; water transparency (Secchi disk) passed from 23.8 m (± 1.3 se) in the 1950s to 11.8 m (± 0.9 se) in the 1990s and 12.7 m (± 0.3 se) in the 2000s. An increase in turbidity was one of the key drivers of changes in community structure over this period (Gatti et al., 2015).

There is also limited direct evidence available for Axinellid sponges. Bell et al. (2015) reviewed the effects and interactions of sponges with sediment in suspension and after deposition. Whilst many sponges are disadvantaged by sedimentation, many examples exist of sponges adapting to sediment presence (Bell et al., 2015; Schönberg, 2015). Adaptations included sediment incorporation, sediment encrusting, structural modification (such as reduction in numbers of oscula, or repositioning of inhalant and exhalant openings), soft sediment anchoring using spicules, modification of spicules to shield the body from sediment, backwashing, mucus production, morphology (e.g. upright forms intercept less settling sediment) and living, at least partially, embedded within the sediment (Bell et al., 2015; Schönberg, 2015).

Schönberg (2015) found that Axinellids frequently formed external crusts and sediment interaction was observed in 5.8 ± 4.8% of observations but required rock substrata under the sediment for attachment. Ackers et al. (1992) reported that  Axinella dissimilis was mainly found on upward-facing, clean or silty rock, and preferred clean oceanic water but was tolerant of silt.

Sensitivity assessment. From the limiting evidence available, the characterizing species of this biotope are likely to tolerate a change in suspended solids at the benchmark level. Therefore, resistance is assessed as ‘High’, resilience as ‘High’, giving an overall sensitivity of ‘Not sensitive’. 

Medium Very Low Medium
Q: Low
A: NR
C: NR
Q: Medium
A: Medium
C: Medium
Q: Low
A: Low
C: Low

There is no direct evidence available to assess Reteporella at the benchmark level. Reteporella colonies in this biotope are small (Reteporella beaniana, 3 cm tall, 5 cm wide; Hayward & Ryland, 1995) so burial by sediment may prohibit feeding and respiration, and sedimentation may prevent the settlement of larvae. Partial mortality due to siltation has been recorded in Pentapora fascialis (Cocito et al., 1998a) although recovery was observed in all but one colony (which fragmented into two smaller colonies). Furthermore, Pentapora fascialis is a large bryozoan, growing up to 30 cm tall in UK waters (Hayward & Ryland, 1979); significantly larger than Reteporella.

There is also limited direct evidence available for Axinellid sponges. Bell et al. (2015) reviewed the effects and interactions of sponges with sediment in suspension and after deposition. Whilst many sponges are disadvantaged by sedimentation, many examples exist of sponges adapting to sediment presence (Bell et al., 2015; Schönberg, 2015). Adaptations included sediment incorporation, sediment encrusting, structural modification (such as reduction in numbers of oscula, or repositioning of inhalant and exhalant openings), soft sediment anchoring using spicules, modification of spicules to shield the body from sediment, backwashing, mucus production, morphology (e.g. upright forms intercept less settling sediment) and living, at least partially, embedded within the sediment (Bell et al., 2015; Schönberg, 2015).

Schönberg (2015) found that Axinellids frequently formed external crusts and sediment interaction was observed in 5.8 ± 4.8% of observations but required rock substrata under the sediment for attachment. Ackers et al. (1992) reported that  Axinella dissimilis was mainly found on upward-facing, clean or silty rock, and preferred clean oceanic water but was tolerant of silt. Axinellid sponges are taller than Reteporella colonies. Axinella dissimilis grows up to 15 cm (Jackson, 2008c) and Axinella damicornis up to 10 cm (Avant, 2006). Although no height data was found for Axinella infundibuliformis, the species can grow over 10 cm in diameter (Reeve, 2005).

Sensitivity assessment. Some mortality of the characterizing species is likely to occur at the benchmark level. Reteporella spp. are small colonies and are likely to be completely or substantially covered by deposition of 5 cm of sediment. Although Axinella infundibuliformis is larger than Reteporella spp., its wide cup shape is likely to collect significant amounts of sediment. Furthermore, the biotope occurs in a low current environment (up to 6 cm/s; Howell et al., 2009) so the removal of sediment is likely to be slow. Therefore, resistance is assessed as ‘Medium’ and resilience is assessed as ‘Very low’, resulting in an overall sensitivity of ‘Medium’

Low Very Low High
Q: Low
A: NR
C: NR
Q: Medium
A: Medium
C: Medium
Q: Low
A: Low
C: Low

There is no direct evidence available to assess Reteporella at the benchmark level. Reteporella colonies in this biotope are small (Reteporella beaniana, 3 cm tall, 5 cm wide; Hayward & Ryland, 1995) so burial by sediment may prohibit feeding and respiration, and sedimentation may prevent the settlement of larvae. Partial mortality due to siltation has been recorded in Pentapora fascialis (Cocito et al., 1998a) although recovery was observed in all but one colony (which fragmented into two smaller colonies). Furthermore, Pentapora fascialis is a large bryozoan, growing up to 30 cm tall in UK waters (Hayward & Ryland, 1979); significantly larger than Reteporella.

There is also limited direct evidence available for Axinellid sponges. Bell et al. (2015) reviewed the effects and interactions of sponges with sediment in suspension and after deposition. Whilst many sponges are disadvantaged by sedimentation, many examples exist of sponges adapting to sediment presence (Bell et al., 2015; Schönberg, 2015). Adaptations included sediment incorporation, sediment encrusting, structural modification (such as reduction in numbers of oscula, or repositioning of inhalant and exhalant openings), soft sediment anchoring using spicules, modification of spicules to shield the body from sediment, backwashing, mucus production, morphology (e.g. upright forms intercept less settling sediment) and living, at least partially, embedded within the sediment (Bell et al., 2015; Schönberg, 2015).

Schönberg (2015) found that Axinellids frequently formed external crusts and sediment interaction was observed in 5.8 ± 4.8% of observations but required rock substrata under the sediment for attachment. Ackers et al. (1992) reported that  Axinella dissimilis was mainly found on upward-facing, clean or silty rock, and preferred clean oceanic water but was tolerant of silt.

Axinellid sponges are taller than Reteporella colonies. Axinella dissimilis grows up to 15 cm (Jackson, 2008c) and Axinella damicornis up to 10 cm (Avant, 2006). Although no height data was found for Axinella infundibuliformis, the species can grow over 10 cm in diameter (Reeve, 2005).

Sensitivity assessment. Some mortality of the characterizing species is likely to occur at the benchmark level. Reteporella spp. and Axinellid sponges are likely to be completely buried by a sediment deposition of 30 cm, including the height of cobbles they occur on. Furthermore, the biotope occurs in a low current environment (up to 6 cm/s; Howell et al., 2009) so the removal of sediment is likely to be slow, with no evidence of resistance to burial found. Therefore, resistance is assessed as ‘Low’ and resilience is assessed as ‘Very low’, resulting in an overall sensitivity of ‘High’.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

‘No evidence’ was found.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Whilst no evidence could be found on the effects of noise or vibrations on the characterizing species, it is unlikely that these species would be adversely affected by noise. This pressure is assessed as ‘Not relevant’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No relevant evidence was found regarding the introduction of anthropogenic light on the Reteporella spp. or Axinellid sponges at the depth of this biotope. As such, this pressure is assessed as ‘No evidence’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

A permanent or temporary barrier to propagule dispersal could affect the larvae of Reteporella spp. and Axinellid sponges, and therefore connectivity and recruitment. However, ‘No evidence’ was available to assess this pressure.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This biotope (M.AtUB.Ro.DeeSpo.RetAxi) is characterized by sessile invertebrates and are unlikely to be affected by an increased risk of collision as defined under the pressure. This pressure is, therefore, assessed as ‘Not relevant’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This biotope (M.AtUB.Ro.DeeSpo.RetAxi) is characterized by invertebrates that are not reliant on vision, as such, the biotope will not be affected by 'Visual disturbance'. This pressure is assessed as ‘Not relevant’.

Biological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is not relevant to the characterizing species within this biotope. Therefore, an assessment of ‘Not relevant’ is recorded.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No alien or non-native species are known to compete with the characterizing species or taxa of this biotope at upper bathyal depths.  Hence, this pressure is recorded as ‘Not relevant’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence’ was found on diseases that may affect the characterizing species or taxa.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

The characterizing species and taxa associated with the biotope are not commercially targeted. Therefore, this pressure is assessed as ‘Not relevant’.

Low Very Low High
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium

There is direct evidence that suggests that Reteporella spp. and Axinellid sponges are susceptible to removal as bycatch from trawling activity. Axinella dissimilis is known to be susceptible to towed fishing gears (Hiscock, 2014).  Hinz et al. (2011) studied the effects of scallop dredging in Lyme Bay, UK and found that the presence of Axinella dissimilis was significantly higher at non-fished sites (33% occurrence) compared to fished sites (15% occurrence). Kędra et al. (2017) also observed the absence of Aninella infundibuliformis in trawled areas but its presence in untrawled areas. Reteporella colonies have also been recorded in scientific trawls (Figuerola et al., 2018).

Sensitivity assessment. The available evidence suggests that bottom-trawling activity readily removes the characterizing species of this biotope. Therefore, resistance is assessed as ‘Low’, resilience as ‘Very low’ and overall sensitivity as ‘High’.

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Citation

This review can be cited as:

Graves, K.P., 2022. Reteporella and Axinellid sponges on Atlantic upper bathyal rock and other hard substrata. 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 04-02-2023]. Available from: https://marlin.ac.uk/habitat/detail/1240

Last Updated: 14/03/2022