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Lobose sponge and stylasterid assemblage on Atlantic upper bathyal rock and other hard substrata

Distribution MapBIO Map Legend

Summary

UK and Ireland classification

Description

This biotope has been found on bedrock and boulders on the shallow flanks of Rockall Bank and is characterized by large yellow lobose sponges and Stylasterid corals. It has only been observed on Rockall Bank most likely due to the shallow depth range over which it occurs; the summits of many of the features are too deep. 

Depth range

300-600 m

Additional information

-

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

The main characterizing taxa of this biotope are lobose sponges and Stylasterids. This biotope has largely been identified through the analysis of images (Parry et al., 2015). Sponges are notoriously difficult to identify from imagery. Therefore, Porifera are often identified based upon their morphology features, namely shape and colour (Howell et al., 2017; Howell et al., 2019). Therefore, ‘lobose sponge’ offers little taxonomic information on the characteristic species. OBIS records of demosponge occurrence on Rockall Bank and the Marine Species ID Portal, Sponges of the NE Atlantic (Van Soest, 2022) were reviewed and several taxa with similar descriptions (lobose, yellow) were identified to help guide and narrow the literature review. As a result, the literature review for ‘lobose sponge’ focused on Mycale lingua and Mycale spp. However, where necessary the literature review looked at other sponge taxa, such as Geodia spp. Similarly, little taxonomic resolution was given in the description as to characterizing Stylasterid (hydrocoral) species. However, where possible, evidence has been compiled for species in the genus Stylaster. Other species or taxa that may be present in this biotope include Anomidae, serpulid polychaetes, Munida, Porifera (encrusting), Ophiactis, Brachiopoda, Cidaris cidaris, Caryophyllia, and Pandalus borealis.

Resilience and recovery rates of habitat

Brooke & Stone (2007) studied the reproduction of the deepwater Stylaster spp. that occur in the Aleutian Islands, Alaska. All the species studied in the region were gonochoristic brooders. Male colonies release sperm from gonophores that fertilize eggs internally held by female colonies. Fertilized eggs are brooded, growing into mature embryos and eventually planulae. Planulae are then released from the gonophores of female colonies, probably over several weeks, rather than a single synchronized event (Brooke & Stone, 2007). The planulae released are highly developed and can settle quickly after release (Hoarau et al., 2021). If local currents are slow, dispersal is low and planulae settle close to their parental colony (Gnecco Polanía, 2016). Hoarau et al. (2021) suggest that the short pelagic larval duration (PLD) and non-dispersive nature of Stylaster larvae explain their “high regional endemicity”, and the “limited distribution of Stylasterid species worldwide”. The short PLD will likely have implications for Stylasterid recovery after a disturbance event. Brooke & Stone (2007) suggested that, where the disturbance was intense and Stylasterid colonies are destroyed/removed/killed, recolonization would be very slow; particularly if the disturbance occurred over a large spatial scale because of Stylasterid's low dispersal potential. However, hydrocorals are known to recover from injury. Ostarello (1973) observed that new tissue had grown over wounds (cut branch) of Allopora californica within one week, with upward growth resuming 4-5 months later. Therefore, Brooke & Stone (2007) suggested that, where disturbances were “light” (injury rather than destroyed/killed), habitat recovery may be shorter because of hydrocorals ability to repair and regrow. Information on the growth rates of Stylasterid colonies is limited to one study. Aranha (2010) calculated the average annual growth rates of Stylaster campylecus to be 1.4 ± 0.1 mm/yr radial and 17.3 ± 1.1 mm/yr axial.

There are limited studies available for the recoverability of Stylasteridae. Althaus et al. (2009) described the impacts of trawling of deep-sea ecosystems on Tasmanian (Australia) seamounts. The seamounts investigated had experienced different levels of fishing.  They were either never trawled, actively trawled, or previously trawled but activity had ceased in the last decade. Stylaster sp. contributed most to the overall dissimilarity between never trawled and actively trawled seamount. The abundance of Stylaster sp. on actively trawled sites (0.37 indv./m2) was less than never trawled (2.71 indv./m2). On seamounts where trawling had ceased a decade before, Stylaster sp. abundance was 1.13 indv./m2; a sign of partial recovery.

Corriero et al. (1998) studied the reproductive strategies of the lobose sponge Mycale contarenii over two years in the Mediterranean (southwestern Apulia). Mycale contarenii is dioecious and viviparous, although no males were found this is likely due to the very short period of spermatogenesis. It undergoes both sexual and asexual reproduction. Asexual reproduction occurred in Mycale contarenii during autumn and winter, seeming to be related to a decrease in temperature. Buds are described as ‘small, well-organized sponges’. The high organizational level of buds suggests that recently detached buds are likely to behave as fully functioning organisms. The highly developed nature of these buds means they likely settle and attach to the substratum quickly, remaining close to their parental sponge. The rate of bud production increased throughout autumn and winter. Sexual reproduction occurs during spring and summer but there is overlap between the two modes. Corriero et al. (1998) concluded that asexual reproduction was likely to play a critical role in maintaining Mycale contarenii populations. Huang et al. (2016) studied the sexual reproduction of Mycale phyllophila in Dongshan Bay, China. Mycale phyllophila is viviparous but in contrast to Mycale contarenii, is hermaphroditic. Sexual reproduction lasted for 5-6 months and peaked when the temperature was above 25°C.

Short dispersal capabilities are also seen in Geodia. Geodia barrette is oviparous, dioecious, and an annual spawner, with one or two periods of gamete release each year (Spetland et al., 2007). Individuals are thought to reproduce simultaneously within the same local population, within a restricted period (Spetland et al., 2007). Asexual reproduction is not thought to be possible in Geodia barretti and it is noted that hermaphroditism is very rare in Astrophoridian sponges (Scalera Liaci & Sciscioli, 1970). Geodia spp. larvae, like the majority of other sponge larvae, are non-feeding and short-lived and remain in the water column for only a few hours (Maldonado & Bergquist, 2002), and they settle in the vicinity of parental populations (Mariani et al., 2003). Knudby et al. (2013) have shown that there is low connectivity between different areas of Geodia spp. (>1500 km apart), due to short-range larval dispersal and high larval retention. It is, therefore, possible that populations are highly inbred and potentially locally adapted (Knudby et al., 2013).

Evidence of recoverability in Mycale sponges is limited, but they are deemed sensitive to disturbance (Robinson et al., 2021). Quick recovery (<1 year) was not observed by Kefalas et al. (2003), stating the effects from disturbance would be the ‘long term’. Malecha & Heifetz (2017) studied the effects of trawling on the abundance and incidence of damage (torn, necrotic, missing tissue) on large sponges (>20 cm) in the Gulf of Alaska. The study compared trawled and un-trawled (reference) transects, 13 years after a single trawling event to monitor the long-term effects. After 13 years, the average abundance of Mycale loveni in trawled transects was 0.71 per 100 m2, compared to 0.83 per 100 m2 in reference areas. Although the difference in density was not large, the proportion of sponges injured in trawled areas was far greater than in reference areas. The mean percentage of damage among Mycale loveni was six times higher within trawled transects (37.0%) than in reference transects (5.7%). Of the seven species analysed, Mycale loveni (3.5%) had the highest mean percentage of necrotic tissue. Furthermore, the average density after 13 years in trawls areas of Poecillastra tenuilaminaris (re-identified from Geodia sp. but of the same sub-order Astrophorina) was 0.53 per 100 m2 compared to 0.59 per 100 m2 in untrawled areas.  Within the trawled areas, Poecillastra tenuilaminaris had the highest mean percentage of missing tissue (7.7%).

There is limited data available on the growth rates of deep-sea sponges. Hoffmann et al. (2003) reported that there was no measurable change in the size or shape of a specimen of Geodia barretti over two years in a Norwegian fjord (personal observation). Klitgaard & Tendal (2004) further suggested that Geodia spp. are likely to be slow-growing, taking at least several decades to reach their large sizes. Deep-sea Hexactinellid sponges, for example, have been calculated to have a linear extension rate of around 2.9 mm/yr for some species (Fallon et al., 2010), whilst others have an average growth rate of 1.98 cm/yr (Leys & Lauzon, 1998). In the characterizing species Geodia barretti, Hoffmann et al. (2003) found that fragments on the inner lining (choanosomal) were able to regenerate body tissue (cortex), and after one year of cultivation in the field, the sponges had increased in weight by 40%. Kutti et al. (2015) also cultivated Geodia barretti using open sea aquaculture in the field, followed by two months of adaptation in a laboratory (the same method as Hoffmann et al., 2003). Beginning from sponge tissue of 4 x 4 x 4 cm in size, within eight months of cultivation, the sponge explants were pumping and had respiration rates similar to that of full-grown individuals, showing cortex regeneration had taken place (Kutti et al., 2015). The survival rate during cultivation in the field was 50% (Kutti et al., 2015).

Sensitivity assessment. Where resistance is ‘None’ and a high degree of habitat recovery is required (>75%), resilience is assessed as ‘Very low’ (>25 years). This is because of the low dispersal capabilities of the taxa that characterize this biotope, which limits the potential to recolonize disturbed areas, combined with slow growth rates. However, where resistance is ‘Low’ or ‘Medium’, resilience is assessed as ‘Low’ (10-25 years). This is because less recovery is required (<75%) and, if viable individuals remain, survivorship and recovery from injuries has been reported. Remaining viable individuals from the characterizing taxa have short dispersal capabilities that may, in turn, increase self-recruitment, thus aiding recovery in the local area.

Hydrological Pressures

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

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 ‘Lobose sponge and Stylasterid assemblages occurring at Rockall Bank’ as 8.4 to 9.2°C. Although this biotope is classed as a ‘deep-sea’ biotope, it is distributed at shallower depths (387 - 685 m; JNCC, 2015) than the permanent thermocline (600-1000 m; White & Dorshel, 2010), and will, therefore, experience some seasonal temperature variations. Unlike most deep-sea biotopes that occur below the permanent thermocline.

No directly relevant evidence was also found on the characterizing taxa. The Stylasterids studied by Brooke & Stone (2007) of the Aleutian Islands occupied a wider thermal niche, -3.5 to 5.5°C (50-300 m deep). Auscavitch et al. (2020) reported the temperature and bathymetric ranges that Stylasterids were found occupying in the Caribbean basin: Stylaster sp. 1, 22.1-22.5°C (166-174 m), Stylaster cf. duchassaingi 13.8-22.1°C (181-408 m), Stylasteridae spp. 6.7-10.9°C (525-838 m).

Direct evidence for the sponges at the benchmark is limited. Vicente et al. (2016) measured the effects of increasing temperature and acidity (+3°C above ambient, pH 7.8) on Mycale grandis over 26 days. They observed no effect on the survival or growth of Mycale grandis, however, the benchmark is +5°C over one month. Mass mortality of Geodia barretti in 2006 and 2008 at the Tisler reef, Norway was concurrent with ~4°C bottom temperature increases over 24 hr periods, for up to two weeks (Guihen et al., 2012). However, in vitro experiments were carried out to replicate this event and no visible signs of stress were found (Strand et al., 2017). Although increased respiration rate was noted, the sponge’s microbiome remained stable, no mortality was observed and respiration rates returned to normal on return to control temperatures (Strand et al., 2017). This could suggest that Geodia barretti is resistant to a temperature increase at benchmark level and that other factors must have been complicit in the mass mortality seen at the Tisler reef (Strand et al., 2017). However, the confidence in the degree of concordance for this assessment has been recorded as ‘Low’ to reflect this uncertainty.  

The study by Strand et al. (2017) is not alone in suggesting that temperature, along with other stressors, may create an additive effect that may be more deleterious to the characterizing species. Scanes et al. (2018) found that the multiple stressors of increased temperature (+5°C) and suspended sediment (simulated inert mine tailings, at 10 mg/l) on Geodia atlantica interacted to cause an increase in the release of nitrogen, indicating a higher energy demand. The temperature increase itself also caused increased respiration and a greater percentage of unstable lysosomes (reduced cellular health), which may also be a result of an increase in energetic demand, as well as stress (Scanes et al., 2018). Furthermore, an increase in silicate uptake (used for biomineralization to produce their skeletons) was observed with elevated temperature (13°C) after 33 days (Scanes et al., 2018). However, this is opposite to previous and subsequent observations.  For example, Strand et al. (2017) found no effect on silicate uptake with warming.  The result of the multiple stressors (warming and suspended sediments) must be interpreted carefully. The authors found that there were complex interactive effects on the species under study. Unpicking these relationships to evaluate temperature change effects is complex.

Sensitivity assessment. The biotopes are associated with a range of bottom water temperatures, however increasing temperature may affect the taxa that characterize this biotope, particularly when in combination with other stressors. Therefore, resistance is assessed as ‘Medium’, resilience as ‘Low’ and sensitivity is assessed as ‘Medium’.

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

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 Lobose sponge and Stylasterid assemblages occurring at Rockall Bank as 8.4 to 9.2°C. Although this biotope is classed as a ‘deep-sea’ biotope, it is distributed at shallower depths (387 - 685 m; JNCC, 2015) than the permanent thermocline (600-1000 m; White & Dorshel, 2010), and will, therefore, experience some seasonal temperature variations. Unlike most deep-sea biotopes that occur below the permanent thermocline. This distribution may also indicate that this biotope’s bathymetric range (387 - 685 m; JNCC, 2015) is limited by minimum temperature. Below the permanent thermocline, the temperature is more stable but is colder.

No directly relevant evidence was also found on the characterizing taxa. The Stylasterids studied by Brooke & Stone (2007) of the Aleutian Islands occupied a wider thermal niche, -3.5 to 5.5°C (50-300 m deep). Auscavitch et al. (2020) reported the temperature and bathymetric ranges that Stylasterids were found occupying in the Caribbean basin: Stylaster sp. 1, 22.1-22.5°C (166-174 m), Stylaster cf. duchassaingi 13.8-22.1°C (181-408 m), Stylasteridae spp. 6.7-10.9°C (525-838 m).

Direct evidence for the sponges at the benchmark is limited. Vincente et al. (2015) measured the effects of increasing temperature and acidity (+3°C above ambient, pH 7.8) on Mycale grandis over 26 days. They observed no effect on the survival or growth of Mycale grandis, however, the benchmark is +5°C over one month. Mass mortality of Geodia barretti in 2006 and 2008 at the Tisler reef, Norway was concurrent with ~4°C bottom temperature increases over 24 hr periods, for up to two weeks (Guihen et al., 2012). However, in vitro experiments were carried out to replicate this event and no visible signs of stress were found (Strand et al., 2017). Although increased respiration rate was noted, the sponge’s microbiome remained stable, no mortality was observed and respiration rates returned to normal on return to control temperatures (Strand et al., 2017). This could suggest that Geodia barretti is resistant to a temperature increase at benchmark level and that other factors must have been complicit in the mass mortality seen at the Tisler reef (Strand et al., 2017). However, the confidence in the degree of concordance for this assessment has been recorded as ‘Low’ to reflect this uncertainty.  

The study by Strand et al. (2017) is not alone in suggesting that temperature, along with other stressors, may create an additive effect that may be more deleterious to the characterizing species. Scanes et al. (2018) found that the multiple stressors of increased temperature (+5°C) and suspended sediment (simulated inert mine tailings, at 10 mg/l) on Geodia atlantica interacted to cause an increase in the release of nitrogen, indicating a higher energy demand. The temperature increase itself also caused increased respiration and a greater percentage of unstable lysosomes (reduced cellular health), which may also be a result of an increase in energetic demand, as well as stress (Scanes et al., 2018). Furthermore, an increase in silicate uptake (used for biomineralization to produce their skeletons) was observed with elevated temperature (13°C) after 33 days (Scanes et al., 2018). However, this is opposite to previous and subsequent observations.  For example, Strand et al. (2017) found no effect on silicate uptake with warming.  The result of the multiple stressors (warming and suspended sediments) must be interpreted carefully. The authors found that there were complex interactive effects on the species under study. Unpicking these relationships to evaluate temperature change effects is complex.

Sensitivity assessment. The biotopes are associated with a range of bottom water temperatures, however increasing temperature may affect the taxa that characterize this biotope, particularly when in combination with other stressors. Therefore, resistance is assessed as ‘Medium’, resilience as ‘Low’ and sensitivity is assessed as ‘Medium’.

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

Sensitivity assessment. Due to the relatively stable salinity conditions in the deep-sea that this biotope occurs in; a change in salinity due to human activities may cause mortality in the characterizing species/taxa. Therefore, resistance is assessed as ‘Low’, resilience as ‘Low’ and overall sensitivity assessed as ‘High’.

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

Sensitivity assessment. Due to the relatively stable salinity conditions in the deep-sea that this biotope occurs in; a change in salinity due to human activities may cause mortality in the characterizing species/taxa. Therefore, resistance is assessed as ‘Low’, resilience as ‘Low’ and overall sensitivity assessed as ‘High’.

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

Water flow is critical to characterizing taxa as they are filter feeders, reliant on currents to transport food to them. An increase in water flow could therefore increase food availability, but also cause the resuspension of sediment that can damage feeding appendages. Conversely, a decrease in current flow could result in a decrease in food availability.

Waller et al. (2011) reported that two seamount sites and the Shackleton Fracture Zone in Drakes Passage showed high numbers of Stylasterids, occurring in 96% of images at one station (Sars Seamount, 610 m). The Drake Passage region, particularly the seamounts, is a highly dynamic environment, characterized by ‘strong bottom currents’ (Waller et al., 2011). Foubert et al. (2005) also suggest that the presence of Stylasterids (Pliobothrus sp.) are an indicator of stronger currents. De Clippele et al. (2018) investigated the role of hydrodynamics in shaping the habitat distribution and coral morphology on Tisler Reef (Norway). The study found that Tisler Reef is a dynamic environment with average high current speeds of 10-50 cm/s (0.1-0.5 m/s) and peak current speeds of 74 cm/s (0.74 m/s). Tisler Reef is dominated by live Lophelia pertusa colonies, framework and rubble, but is associated with Mycale lingua and Geodia sp. and, in particular, Mycale lingua that has a high percentage cover.

Sensitivity assessment. The characterizing taxa of this biotope are known to occur in current speeds that exceed the change at the benchmark level and are considered to be indicators of high current/energy environments. Therefore, this biotope is unlikely to be adversely affected by a change in current flow at the benchmark level. As a result, resistance is characterized as ‘High’, resilience as ‘High’ and overall sensitivity as ‘Not sensitive’

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

‘Lobose sponge and Stylasterid assemblages’ are found at upper bathyal depths; therefore, they will not be impacted by a change in emergence. As a result, 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

‘Lobose sponge and Stylasterid assemblages’ are found at upper bathyal depths. Therefore, they will not be affected by changes in nearshore wave exposure and this pressure is 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.

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

There is no direct evidence available to assess the tolerance of Stylasterids to de-oxygenation. Auscavitch et al. (2020) reported that four species of Stylasterid (Stylaster sp. 1, Crypthelia sp., Stylaster cf. duchassaingi, Stylasteridae spp.) in the Caribbean basin occurred in dissolved oxygenation concentrations from 2.41-7.22 mg/l. Lunden et al. (2014) also studied the effect of decreasing oxygen concentration of Lophelia collected from the Gulf of Mexico.  Oxygen concentrations within the Gulf of Mexico are lower than those recorded in the North East Atlantic, with records ranging from 1.5 - 3.2 ml/l (2.14 – 4.57 mg/l) (Lunden et al., 2014) and, therefore, have a higher tolerance through local adaptation to lower dissolved oxygen concentrations compared to North East Atlantic populations. Laboratory experiments exposed Lophelia to different oxygen concentrations for seven days. The Lophelia samples survived (100%) exposure to 5.3 and 2.9 ml/l, but experienced 100% mortality at 1.57 ml/l (2.24 mg/l) after seven days. 

There is some evidence for Geodia barretti of behavioural adaptations (reduced pumping and respiration rates) that allow the sponges to restrict oxygen consumption as a protective mechanism when exposed to increased sediment load, which can cause short-term depletion of oxygen (Kutti et al., 2015; Schoenberg, 2016; Tjensvoll et al., 2013). There is also evidence of natural hypoxia and suboxia in some Demospongiae taxa, related to internal microbial conditions (Lavy et al., 2016). However, Leys et al. (2018) suggested that changes in oxygenation may negatively affect Geodia barretti.  Leys et al. (2004) found that Hexactinellida (glass sponges) were rare (fewer than eight live sponges per 10 m2) in regions of fjords in British Columbia where dissolved oxygen levels fell below 2 ml/l. It may be possible that Demosponges share a similar pattern, however, no evidence for this class could be found.

As there is no direct evidence on the resistance or resilience of the characterizing taxa in a reduced oxygen scenario at benchmark pressure, 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

Nutrient availability will be important to this biotope (M.AtUB.Ro.DeeSpo.SpoSty), 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 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.SpoSty) 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.SpoSty) is characterized by hard rock (bedrock and boulders) substrata (JNCC, 2015) and is required for the successful settlement of the characterizing species/taxa. If the hard rock (bedrock and boulders) were replaced by a soft rock or 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.SpoSty) is characterized by hard rock (bedrock and boulders). A change in seabed type to anything but cobble, pebble, and gravel 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

As the characterizing taxa of this biotope 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’.

None Very Low High
Q: High
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 biotope are from bottom fishing (e.g. beam trawls), deep-sea mining activity (e.g. mining vehicles) and from anchoring or positioning of offshore structures. There is evidence that Stylasterids are readily caught in bottom trawls (Rooper et al., 2011; Probert et al., 1998). Probert et al. (1998) characterized the bycatch of bottom trawling fisheries on Chatham Rise, New Zealand. The study found that Stylasteridea (Errina chathamensis) was the second-largest bycatch on sloped fishing grounds (hills, opposed to flats). Probert et al. (1998) suggest that Errina chathamensis susceptibility to trawl gear types is a result of its rough texture and spiny morphology, causing it to snag in trawl mesh.

Kefalas et al. (2003) assessed the recovery after scallop dredging on sponge grounds after one year (1998-1999), investigating the degree of recoverability between scallop dredging seasons. All four species of Mycale present pre-dredging was either absent or greatly reduced the following year. The abundance (individuals per 40 m2) for each species were: Mycale rotalis, 1998 = 0.50, 1999 = 0.33; Mycale contarenii, 1998 = 7.67, 1999 = 0.50; Mycale macillenta, 1998 = 0.33, 1999 = 0.00; Mycale massa, 1998 = 21.33, 1999 = 2.67. Therefore, Kefalas et al. (2003)  concluded that recovery was not possible between scallop dredging seasons. Iceberg scour is also a source of abrasion in Antarctica. Robinson et al. (2021) suggested that because it is a ‘disturbance-sensitive’ species, they would expect Mycale acerata to be removed by ice scour. Furthermore, under increasing iceberg scour induced by global warming, a smaller window for recovery would be available and, therefore, it would be removed entirely from the affected areas because of its slow growth and reproductive rates.

Malecha & Heifetz (2017) studied the effects of trawling on the abundance and incidence of damage (torn, necrotic, missing tissue) on large sponges (>20 cm) in the Gulf of Alaska. The study compares trawled and un-trawled (reference) transects 13 years after a single trawling event to monitor the long-term effects. After 13 years, the average abundance of Mycale loveni in trawled transects was 0.71 per 100 m2, compared to 0.83 per 100 m2 in reference areas. Although the difference in density was not vast, the proportion of sponges injured in trawled areas was far greater than in reference areas. The mean percentage of damage among Mycale loveni was six times higher within trawled transects (37.0%) than in reference transects (5.7%). Of the seven species analysed, Mycale loveni (3.5%) had the highest mean percentage of necrotic tissue. Furthermore,  the average density of Poecillastra tenuilaminaris (re-identified from Geodia sp. but of the same sub-order Astrophorina) after 13 years in trawls areas was 0.53 per 100 m2 compared to 0.59 per 100 m2 in untrawled areas.  Within the trawled areas, Poecillastra tenuilaminaris had the highest mean percentage of missing tissue (7.7%). This study not only demonstrated the susceptibility of Mycale loveni and Poecillastra tenuilaminaris to removal by trawling activity, but the long-lasting injuries inflicted on remaining individuals.

Sensitivity assessment. The characterizing species are highly susceptible to injury from abrasion. The impacts of this are likely to be severe and long-lasting because of the slow-growing and low dispersal nature of the characterizing taxa, which reduces their ability to recolonize the affected area. As a result, resistance is assessed as ‘None’, resilience as ‘Very low’, resulting in an overall sensitivity score of ‘High’.

None Very Low High
Q: High
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 ‘None’, resilience assessed as ‘Very low’, and overall sensitivity of ‘High’.

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

Suspended solids are important to characterizing taxa of this biotope because they are filter feeders. As a result, these taxa are reliant upon currents transporting food items 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 available to assess the resistance of Stylasterids to this pressure at the benchmark level. However, Cairns (1992) suggested that, globally, Stylasterids are only found in low turbidity regions. In addition, Horta-Puga & Carricart-Ganivet (1989) only observed Stylaster roseus in low turbidity environments when studying tropical coral reefs in the Gulf of Mexico. The turbidity over Rockall Bank, where this biotope occurs, fluctuates between 5 and 48 OBS (optical backscatter), following the same pattern as temperature and fluorescence (Duineveld et al., 2007). It is, therefore, likely that the source of suspended particulates is biologically derived from early spring and late summer plankton blooms. It is, therefore, also likely that this biotope experiences natural fluctuations (seasonal) in turbidity.

Direct evidence for Mycale is limited to one source, where Gerrodette & Flechsig (1979) note the reduction in the pumping activity of Mycale sp. was observed which coincided with increased turbidity due to storms. However, more evidence is available for Geodia. Laboratory studies have shown severe reductions in respiration rates of Geodia barretti when subjected to high levels of suspended sediments for four hours (Tjensvoll et al., 2013). The study found decreases of 52% (at 50 mg/l), 86% (at 100 mg/l) and 67% (at 500 mg/l). However, specimens returned to a baseline metabolic rate four hours after exposure (Tjensvoll et al., 2013). In the higher sediment loads, sponges were noted to be actively pumping one hour after the exposure period ended. In another study of four-hour exposure to suspended crushed rock particles at 500 mg/l, Kutti et al. (2015) similarly found that the oxygen consumption of Geodia barretti decreased significantly (50%) from pre-exposure consumption. However, all sponges recovered within the 30-minute flushing cycle, and oxygen consumption did not differ significantly from the pre-exposure rates.

In long-term exposure (50 days) of Geodia barretti to high (50 mg/l) and low (10 mg/l) concentrations, oxygen consumption was 50% lower in sponges exposed to crushed rock compared to those exposed to natural bottom sediments (Kutti et al., 2015). However, after 29 days of cyclic exposure, the sponges’ respiration rates did not return to that of unexposed sponges and were reduced by >60% during the daily 12-hour recovery interval (Kutti et al., 2015). This suggested that a recovery time of more than 12 hours is required. The reductions in oxygen consumption were a result of a decrease or arrest in pumping, which was a response to high suspended solid concentrations (Tjensvoll et al., 2013). Bell et al. (2015) also suggested that the suppression of oxygen consumption may be a defence mechanism to prevent the internal sponge tissue from being exposed to sediment. These studies, therefore, indicate that Geodia barretti has well-developed responses to cope with short periods of elevated concentrations of suspended natural bottom sediments. Tjensvoll et al. (2013) also found that exposure of Geodia barretti to low sediment concentrations of 10 mg/l had little or no effect, although there were some variations in respiration rate during the recovery period.

Fang et al. (2018) investigated the effects of suspended natural sediment (and barite and bentonite) on Geodia barretti and Stryphnus fortis (similar to the characterizing species Stryphnus ponderosus). No sponge mortality was observed over the 33-day exposure periods, at concentrations of ≤15.2 mg/l, however, the sponges were covered by deposited particles. Reduced tissue oxygenation occurred in Stryphnus fortis on exposure to suspended natural sediments and this was likely to be caused by reduced pumping (Bell et al., 2015; Fang et al., 2018). Exposure to fine particles caused reduced oxygen consumption. It is suggested that finer particles (<63 µm) may have greater effects than larger particles (Kutti et al., 2015) on the metabolism in Geodia barretti, even at 10 mg/l (Fang et al., 2018), but Stryphnus fortis samples were less sensitive. However, Geodia barretti recovered its oxygen-nitrogen metabolism (to control levels) following abatement of suspended natural sediment after 33 days. However, net ammonium flux displayed strong delayed responses during the recovery period in Stryphnus fortis, which indicates possible long-term damage from suspended natural sediment.

In a further study, exposure of Geodia barretti to suspended natural (reference) sediment up to a total suspended solids concentration of 100 mg/l for 12 hours caused no significant change to lysosomal membrane stability (LMS) (an indication of cellular stress) (Edge et al., 2016). Furthermore, there was no significant difference in LMS in sponges exposed to seawater compared to suspended reference sediments at 10, 50 or 100 mg/l for 12 hours. Over a slightly longer exposure, sponges exposed to reference sediment at 30 mg/l after six days did show lower LMS and lower total organic energy than those exposed to seawater, but at 14 days there were no significant differences. The increase in lysosomal stability with the length of exposure suggested possible acclimatisation in Geodia barretti at <30 mg/l (Edge et al., 2016). A decrease in respiration levels was also recorded when Geodia atlantica was exposed to suspended sediments at 10 mg/l over 40 days (Scanes et al., 2018). Furthermore, lower silicate uptake (used for biomineralization to produce their skeletons) occurred after 33 and 40 days of exposure to suspended sediments (Scanes et al., 2018). After 26 days of exposure, lysosomal membrane instability was increased in comparison to the control, but this effect was not observed again at 33 or 40 days, which again suggested that Geodia atlantica could acclimatise after 26 days of exposure to low levels of suspended sediment (Scanes et al., 2018).

Sensitivity assessment. At the benchmark level of change in one rank on the WFD scale for one year (i.e. from 10 to 100 mg/l), suspended solids may reduce the survivability of the characterizing species in the long term, despite there being some evidence of acclimatisation by the typical sponge species (e.g. Geodia) (Scanes et al., 2018). The effects also vary with the type and particle size of the suspended sediment. Higher levels of sediment exposure are likely to also increase the recovery period (Pineda et al., 2017b). However, the characteristic Stylastrids are only found in low turbidity areas (Cairns, 1992) so an increase in turbidity may result in their loss from the biotope. Therefore, resistance is assessed as ‘Low’, resilience as ‘Low’ and overall sensitivity is assessed as ‘High’.

Medium 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 to assess the effect of suspended sediment on Stylasterids at the benchmark level. However, there is consensus that Stylasterids are not present in regions of increased sedimentation (Cairns, 1992). Stylasterids are often found colonizing rock walls or cliffs, such as Errina novaezelandiae and Errina dendyi (Bax, 2014). Furthermore, Ostarello (1973) stated that the preferred habitat for stylasterid planulae settlement is on vertical surfaces, thus avoiding the effects of any sedimentation. Roberts et al. (2008) observed that the Stylasterid Pliobothrus characterized cobble and exposed rock macro-habitats. They note that Pliobothrus was not seen colonizing any coral framework or rubble. Roberts et al. (2008) suggested this supported Cairns’ (1992) suggestion that scleractinian corals, which have better sediment-shedding abilities and larger polyps than Stylasterids, may outcompete Stylasterids on horizontal surfaces subject to sedimentation.

There is little direct evidence available to assess Mycale against the benchmark. Carbalo (2006) investigated the response of tropical sponge communities to natural variations in the deposition of sand along the Pacific Mexican coast from February 2001 to June 2002. Carbalo (2006) concluded that a reduction in sponge diversity, losses, the substitution of species and a shift from a relatively mature and stable community to an unstable one was the result of a mass sedimentation event. Mycale sp., and other massive and branching species, were present only before the deposition event. A change in dominant wind direction during the transition from the drought to the rainy season provoked an increase in sedimentation (up to 13 kg m2 per day). Throughout spring, large volumes of sediment were deposited with a change in weather. During this period, the average monthly abundance (ind. per 24 m2) of Mycale sp. was reduced from 11.25 (February) to 0.00 (May), where Mycale sp. remained absent until October. From October 2001 to June 2002, the average monthly abundance of Mycale sp. continually fluctuated but never exceeded 1.60. Carbalo (2006) found a shift in the dominant sponge species in the area. Previously, the sponge community was dominated by massive or branching sponges but was now dominated by encrusting and boring sponges. For example, in February 2001 average density of Microciona sp. was 34.0, increasing to a maximum of 102.7 during the complete absence of Mycale sp.

Fang et al. (2018) observed that Geodia barretti was covered by deposited particles following 33-day exposure to suspended solids (≤15.2 mg/l). Spicule protrusion, one mechanism to reduce smothering by sediment, was observed for Geodia barretti.  However, it was not effective in the intensive sediment deposition the sponges were subject to in the study.  Another mechanism to reduce smothering by sediment in sponges is to reduce pumping and, therefore, reduce tissue oxygenation. Reduced pumping was observed in Stryphnus fortis on exposure to suspended natural sediments (Bell et al., 2015; Fang et al., 2018). In another experiment on Geodia barretti, images of the sponges before and after the exposure to suspended particles showed ‘light’ deposition of sediment on the sponge surface (Kutti et al., 2015).

Schoenberg (2016), who suggested that resistance might be influenced by the nature of the deposited sediment and duration of burial, in general, discussed the effects of burial on sponges. It was hypothesised that coarse material may reduce the amount of deoxygenation that the sponge experiences from burial. It is also expected that sponges may be able to survive temporary burial (Hoffmann et al., 2008) but would commonly die if left buried (Schoenberg, 2016). Resistance may vary by species and be dependent on the morphology and where individuals survive, there is likely to be a large metabolic cost in clearing the sponge’s respiratory channels (Schoenberg, 2016). In addition, Schoenberg (2016) reported a range of concerns surrounding siltation on sponges in general, including behavioural adaptations, mucus production, and phagocytosis of ingested material.

Sensitivity assessment. Mortality is likely to occur in lobose sponges and Stylasterids at this benchmark level (5 cm), however, mass mortality is probably unlikely. The consensus is that Stylasterids do not occur in areas of high sedimentation, However, the pressure benchmark is one single small incidence of sedimentation and is not persistent. The evidence also suggests that the characterizing sponges can tolerate some sedimentation over short periods. The characteristic taxa are larger than 5 cm and therefore should not be completely buried, particularly if occurring on cobbles or boulders where their position is elevated from the seafloor. Therefore, resistance is assessed as ‘Medium’, resilience is assessed as ‘Low’, and overall sensitivity as ‘Medium’

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

No direct evidence was found to assess Stylasterids at the benchmark level. However, there is consensus that Stylasterids are not present in regions of increased sedimentation (Cairns, 1992). Stylasterids are often found colonizing rock walls or cliffs, such as Errina novaezelandiae and Errina dendyi (Bax, 2014). Furthermore, Ostarello (1973) stated that the preferred habitat for stylasterid planulae settlement is on vertical surfaces, thus avoiding the effects of any sedimentation. Roberts et al. (2008) observed that the Stylasterid Pliobothrus characterized cobble and exposed rock macro-habitats. They note that Pliobothrus was not seen colonizing any coral framework or rubble. Roberts et al. (2008) suggested this supported Cairns’ (1992) suggestion that scleractinian corals, which have better sediment-shedding abilities and larger polyps than Stylasterids, may outcompete Stylasterids on horizontal surfaces subject to sedimentation.

There is little direct evidence available to assess Mycale against the benchmark. Carbalo (2006) investigated the response of tropical sponge communities to natural variations in the deposition of sand along the Pacific Mexican coast from February 2001 to June 2002. Carbalo (2006) concluded that a reduction in sponge diversity, losses, the substitution of species and a shift from a relatively mature and stable community to an unstable one was the result of a mass sedimentation event. Mycale sp., and other massive and branching species, were present only before the deposition event. A change in dominant wind direction during the transition from the drought to the rainy season provoked an increase in sedimentation (up to 13 kg m2 per day). Throughout spring, large volumes of sediment were deposited with a change in weather. During this period, the average monthly abundance (ind. per 24 m2) of Mycale sp. was reduced from 11.25 (February) to 0.00 (May), where Mycale sp. remained absent until October. From October 2001 to June 2002, the average monthly abundance of Mycale sp. continually fluctuated but never exceeded 1.60. Carbalo (2006) found a shift in the dominant sponge species in the area. Previously, the sponge community was dominated by massive or branching sponges but was now dominated by encrusting and boring sponges. For example, in February 2001 average density of Microciona sp. was 34.0, increasing to a maximum of 102.7 during the complete absence of Mycale sp.

Fang et al. (2018) observed that Geodia barretti was covered by deposited particles following 33-day exposure to suspended solids (≤15.2 mg/l). Spicule protrusion, one mechanism to reduce smothering by sediment, was observed for Geodia barretti, however, it was not effective to the intensive sediment deposition the sponges were subject to in the study.  Another mechanism to reduce smothering by sediment in sponges is to reduce pumping and, therefore, reduce tissue oxygenation. Reduced pumping was observed in Stryphnus fortis on exposure to suspended natural sediments (Bell et al., 2015; Fang et al., 2018). In another experiment on Geodia barretti, images of the sponges before and after the exposure to suspended particles showed ‘light’ deposition of sediment on the sponge surface (Kutti et al., 2015).

Schoenberg (2016), who suggested that resistance might be influenced by the nature of the deposited sediment and duration of burial, in general, discussed the effects of burial on sponges. It was hypothesised that coarse material may reduce the amount of deoxygenation that the sponge experiences from burial. It is also expected that sponges may be able to survive temporary burial (Hoffmann et al., 2008) but would commonly die if left buried (Schoenberg, 2016). Resistance may vary by species and be dependent on the morphology and where individuals survive, there is likely to be a large metabolic cost in clearing the sponge’s respiratory channels (Schoenberg, 2016). In addition, Schoenberg (2016) reported a range of concerns surrounding siltation on sponges in general, including behavioural adaptations, mucus production, and phagocytosis of ingested material.

Sensitivity assessment. Neither Stylasterids nor Mycale are tolerant to high levels of sedimentation. At the benchmark (30 cm), the characterizing taxa are likely to be completely buried and it will take a while for sediment to be removed by currents. Therefore, resistance is assessed as ‘None’ as this could result in mass mortality, and given that the characterizing taxa are largely self-recruiting with low dispersal potential, recolonization of the affected area is likely to be slow. Hence, resilience is assessed as ‘Very low’, and overall sensitivity as ‘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 lobose sponges and Stylasterids 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 lobose sponges and Stylasterids, 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.SpoSty) 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.SpoSty) 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 Low High
Q: High
A: High
C: Medium
Q: Medium
A: Medium
C: Medium
Q: Medium
A: Medium
C: Medium

There is evidence that Stylasterids are readily caught in bottom trawls (Rooper et al., 2011; Probert et al., 1998). Probert et al. (1998) characterized the bycatch of bottom trawling fisheries on Chatham Rise, New Zealand. The study found that Stylasteridea (Errina chathamensis) was the second-largest bycatch on sloped fishing grounds (hills, opposed to flats). Probert et al. (1998) suggest that Errina chathamensis susceptibility to trawl gear types was a result of its rough texture and spiny morphology, causing it to snag in trawl mesh.

Kefalas et al. (2003) assessed the recovery after scallop dredging on sponge grounds after one year (1998-1999), investigating the degree of recoverability between scallop dredging seasons. All four species of Mycale present pre-dredging was either absent or greatly reduced the following year. The abundance (individuals per 40 m2) for each species were: Mycale rotalis, 1998 = 0.50, 1999 = 0.33; Mycale contarenii, 1998 = 7.67, 1999 = 0.50; Mycale macillenta, 1998 = 0.33, 1999 = 0.00; Mycale massa, 1998 = 21.33, 1999 = 2.67. Therefore, Kefalas et al. (2003)  concluded that recovery was not possible between scallop dredging seasons. Iceberg scour is also a source of abrasion in Antarctica. Robinson et al. (2021) suggested that because it is a ‘disturbance-sensitive’ species, they would expect Mycale acerata to be removed by ice scour. Furthermore, under increasing iceberg scour induced by global warming, a smaller window for recovery would be available and, therefore, Mycale acerata would be removed entirely from the affected areas because of its slow growth and reproductive rates,

Malecha & Heifetz (2017) studied the effects of trawling on the abundance and incidence of damage (torn, necrotic, missing tissue) on large sponges (>20 cm) in the Gulf of Alaska. The study compared trawled and un-trawled (reference) transects 13 years after a single trawling event to monitor the long-term effects. After 13 years, the average abundance of Mycale loveni in trawled transects was 0.71 per 100 m2, compared to 0.83 per 100 m2 in reference areas. Although the difference in density was not large, the proportion of sponges injured in trawled areas was far greater than in reference areas. The mean percentage of damage among Mycale loveni was six times higher within trawled transects (37.0%) than in reference transects (5.7%). Of the seven species analysed, Mycale loveni (3.5%) had the highest mean percentage of necrotic tissue. Furthermore, the average density of Poecillastra tenuilaminaris (re-identified from Geodia sp. but of the same sub-order Astrophorina) after 13 years in trawls areas was 0.53 per 100 m2 compared to 0.59 per 100 m2 in untrawled areas.  Within the trawled areas, Poecillastra tenuilaminaris had the highest mean percentage of missing tissue (7.7%). This study not only demonstrated the susceptibility of Mycale loveni and Poecillastra tenuilaminaris to removal by trawling activity, but the long-lasting injuries inflicted on remaining individuals.

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

Bibliography

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  9. Corriero, G., Scalera Liaci, L., Nonnis Marzano, C. & Gaino, E., 1998. Reproductive strategies of Mycale contarenii (Porifera: Demospongiae). Marine Biology, 131 (2), 319-327. DOI https://doi.org/10.1007/s002270050325

  10. De Clippele, L. H., Huvenne, V. A. I., Orejas, C., Lundälv, T., Fox, A., Hennige, S. J. & Roberts, J. M., 2018. The effect of local hydrodynamics on the spatial extent and morphology of cold-water coral habitats at Tisler Reef, Norway. Coral Reefs, 37 (1), 253-266. DOI https://doi.org/10.1007/s00338-017-1653-y

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Citation

This review can be cited as:

Graves, K.P., 2022. Lobose sponge and stylasterid assemblage 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/1241

Last Updated: 15/03/2022