The Marine Life Information Network

Temperature increase (local)

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

Evidence

Breeman et al. (1988) reported that gametophytes and tetrasporophytes survived between 0°C and 25°C but that 30°C was lethal after 2-6 weeks. Tetrasporophytes grew faster than gametophytes at 20-25°C in culture. The maximum growth of tetrasporophytes was between at 15-25°C.  Gametophytes exhibited maximum growth at 15°C but growth deformities at 25°C. Nash et al. (2005) also reported maximum biomass production of the tetrasporophyte (Trailliella phase) at 15-20°C, long day length (16:8 hrs L:D) in culture.

Temperature and day length regulate reproduction (Breeman et al., 1988, Breeman & Guiry, 1989). In Galway Bay, Ireland, tetrasporophytes reproduced (formed tetrasporangia) in short day lengths (<12 hrs) when temperatures were between 11 and 18°C.  Tetrasporangia were recorded between September 1985 and February 1986 but were most abundant in early autumn (October to November) (Breeman et al., 1988). Gametophytes developed from tetraspores released between September and February. Gametophytes became fertile between 5 and 20°C but not at 0°C or 25°C.  Spermatangia were observed in young male gametophytes between mid-December and February and in adult gametophytes from late March to the end of May. Spermatangia were absent in mid-winter when temperatures of less than 2°C inhibited their formation. Carpogonia were observed on female gametophytes at the end of April when seawater temperature had risen to above 10°C. Carpogonia developed between 10 and 20°C mainly in long days (>12 hrs) but in short days were only abundant above 15°C.

Breeman & Guiry (1989) noted that the 'effective' day length and temperatures required for initiation of tetrasporangia were influenced by tides. For example, high water springs at the beginning and end of the day reduced the effective day length and caused the early onset of reproduction. In addition, low water spring tides in the middle of the day exposed the plants to higher air temperatures when the seawater temperatures were otherwise below those required to induce tetrasporangia.

In Japan, mature female gametophytes are seen regularly, and sexual reproduction is synchronised. Gametophytes develop in winter when temperatures are optimal for reproduction and growth (15°C) but disappear by mid-June when temperatures reach lethal values of around 25°C (Breeman et al., 1988).  Van Hoek (1982; cited in Lüning, 1990) reported that the southern distribution of the tetrasporophyte ( the Trailliella phase) in the North Atlantic was limited by the 25°C isotherm while its northern distribution was limited by the 10°C summer isotherm.

Sensitivity assessment. An increase in temperature is likely to interfere with reproduction depending on the time of year.  A long-term increase of 2°C may help to synchronise sexual reproduction and improve growth rates. A short-term increase of 5°C for a month may be lethal to gametophytes and tetrasporophytes in summer but may trigger tetrasporophyte reproduction in winter.  Therefore, a resistance of Low is suggested to represent potential mortality in the summer months.  Resilience is probably High so that sensitivity is assessed as Low.

Temperature decrease (local)

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

Evidence

Breeman et al. (1988) reported that gametophytes and tetrasporophytes survived between 0°C and 25°C but that 30°C was lethal after 2-6 weeks. Tetrasporophytes grew faster than gametophytes at 20-25°C in culture. The maximum growth of tetrasporophytes was between at 15-25°C.  Gametophytes exhibited maximum growth at 15°C but growth deformities at 25°C. Nash et al. (2005) also reported maximum biomass production of the tetrasporophyte (Trailliella phase) at 15-20°C, long day length (16:8 hrs L:D) in culture.

Temperature and day length regulate reproduction (Breeman et al., 1988, Breeman & Guiry, 1989). In Galway Bay, Ireland, tetrasporophytes reproduced (formed tetrasporangia) in short day lengths (<12 hrs) when temperatures were between 11 and 18°C.  Tetrasporangia were recorded between September 1985 and February 1986 but were most abundant in early autumn (October to November) (Breeman et al., 1988). Gametophytes developed from tetraspores released between September and February. Gametophytes became fertile between 5 and 20°C but not at 0°C or 25°C.  Spermatangia were observed in young male gametophytes between mid-December and February and in adult gametophytes from late March to the end of May. Spermatangia were absent in mid-winter when temperatures of less than 2°C inhibited their formation. Carpogonia were observed on female gametophytes at the end of April when seawater temperature had risen to above 10°C. Carpogonia developed between 10 and 20°C mainly in long days (>12 hrs) but in short days were only abundant above 15°C.

Breeman & Guiry (1989) noted that the induction of tetrasporangia was limited to a brief period in autumn when short days coincide with temperatures above 11°C because in winter and early spring the temperature is too low for induction, such as on the coasts of America and northern Europe. This is the case on the American (west Atlantic) coasts where the autumnal fall in seawater temperatures is steeper than on east Atlantic coasts. Van Hoek (1982; cited in Lüning, 1990) reported that the southern distribution of the tetrasporophyte ( the Trailliella phase) in the North Atlantic was limited by the 25°C isotherm while its northern distribution was limited by the 10°C summer isotherm.

Sensitivity assessment. A long-term decrease in temperature (e.g. 2°C) may prevent the induction of tetrasporangia and reduce reproductive output. A short-term 5°C change may, however, result in some mortality of both tetrasporophytes in the winter months. Therefore, a resistance of Low is suggested.  Resilience is probably High so that sensitivity is assessed as Low.

Salinity increase (local)

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

Evidence

Bonnemaisonia hamifera is recorded from lower shore tidal pools and the subtidal (Guiry & Guiry, 2015). Leidenburger et al. (2015) reported that Bonnemaisonia hamifera was found at sea surface salinities of between 14.26 and 37.55 psu (based on satellite data and distribution).  This biotope (SMp.KSwSS.Tra) occurs in lagoons, sea lochs and voes, in full and variable salinity (Connor et al., 2004). However, no further information on salinity tolerance was found.

Sensitivity assessment.  An increase in salinity from full or variable conditions would result in hypersaline conditions (>40 psu). But no evidence was found on which to base an assessment.

Salinity decrease (local)

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

Evidence

Bonnemaisonia hamifera is recorded from lower shore tidal pools and the subtidal (Guiry & Guiry, 2015). Leidenburger et al. (2015) reported that Bonnemaisonia hamifera was found at sea surface salinities of between 14.26 and 37.55 psu (based on satellite data and distribution).  This biotope (SMp.KSwSS.Tra) occurs in lagoons, sea lochs and voes, in full and variable salinity (Connor et al., 2004). However, no further information on salinity tolerance was found.

Sensitivity assessment.  A decrease in salinity from full or variable conditions would result in reduced salinity conditions (18-30 psu).  If the biotope can survive variation in salinity to e.g. 18 psu and Bonnemaisonia hamifera is recorded from sites as low as 14.26 psu, then it may be able to survive reduced conditions for a year.  However, the species diversity of the faunal component of the biotope is likely to be reduced.  Therefore, a tentative resistance of Medium is suggested. Resilience is probably High so that the sensitivity is assessed as Low at the benchmark level but at Low confidence.

Water flow (tidal current) changes (local)

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

Evidence

This biotope (SMp.KSwSS.Tra) occurs in weak (<0.5 m/s) to very weak (negligible) flow in wave sheltered environments such as lagoons, sea lochs and voes (Connor et al., 2004).  The tetrasporophytes (Trailliella phase ) is attached to the substratum by unicellular rhizoids or multicellular haptera formed at intervals (Dixon & Irvine, 1977). Dixon & Irvine (1977) noted that the Trailliella phase is usually epiphytic.  But in this biotope, it forms mats on shallow muddy sediments in the sublittoral (Connor et al., 2004).  It is presumably anchored loosely to larger fragments of substrata, stones etc.  It is known to fragment and both the Trailliella phase and gametophytes are known to drift.  While fragmentation and drift may be advantageous to the spread of the species, it may make the mats of Trailliella susceptible to damage from water flow and wave action, especially as the density or abundance of the mats is a key descriptor for the biotope.  

Sensitivity assessment.  The biotope is recorded from weak to very weak tidal flow so that a further decrease is not relevant.  However, an increase in water flow as low a 0.1-0.2 m/s (the benchmark), especially in the winter months, may result in loss of a proportion of the Trailliella mats and loss of the biotope. Therefore, a resistance of Low is suggested. Resilience is probably High so that the sensitivity is assessed as Low at the benchmark level but at Low confidence.

Emergence regime changes

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

Evidence

Trailliella is recorded from the subtidal and low water tidepools (Dixon & Irvine, 1977) or low water (Breeman & Guiry, 1989).  An increase in emergence is only relevant to the shallowest examples of the biotope. The species appears to be restricted to low water, low water tide pools and the subtidal. In addition, Breeman & Guiry (1989) noted that the timing of high and low tides, day length and temperature, affected the induction of reproduction in the tetrasporophyte (Trailliella).  Therefore, it may not survive an increase in emergence or may be out-competed and overgrown by other species.  A resistance of None is suggested. Resilience is probably Medium so that sensitivity is assessed as Medium but with Low confidence.  

Wave exposure changes (local)

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

Evidence

This biotope (SMp.KSwSS.Tra) occurs in weak (<0.5 m/s) to very weak (negligible) flow in wave sheltered (sheltered to extremely wave sheltered) environments such as lagoons, sea lochs and voes (Connor et al., 2004).  The tetrasporophytes (Trailliella phase) is attached to the substratum by unicellular rhizoids or multicellular haptera formed at intervals (Dixon & Irvine, 1977). Dixon & Irvine (1977) noted that the Trailliella phase is usually epiphytic.  But in this biotope, it forms mats on shallow muddy sediments in the sublittoral (Connor et al., 2004).  It is presumably anchored loosely to larger fragments of substrata, stones etc.  It is known to fragment and both the Trailliella phase and gametophytes are known to drift.  While fragmentation and drift may be advantageous to the spread of the species, it may make the mats of Trailliella susceptible to damage from water flow and wave action, especially as the density or abundance of the mats is a key descriptor for the biotope.  

Sensitivity assessment.  The biotope is recorded from wave sheltered to extremely wave sheltered environments so that a further decrease is not relevant.  However, an increase in wave action is likely to remove the mats from the substratum and the biotope is likely to be lost. A change in significant wave height of only 3-5% (the benchmark) represents a minor change in wave action but may still remove a proportion of the mats in shallow example of the biotopes as the Trailliella phase is probably only loosely attached to the muddy sediment on which this biotope is found.  Therefore, a resistance of Low is suggested. Resilience is probably High so that the sensitivity is assessed as Low at the benchmark level but at Low confidence.

Transition elements & organo-metal contamination

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

Evidence

This pressure is Not assessed but evidence is presented where available.

Hydrocarbon & PAH contamination

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

Evidence

This pressure is Not assessed but evidence is presented where available.

Synthetic compound contamination

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

Evidence

This pressure is Not assessed but evidence is presented where available.

Radionuclide contamination

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

Evidence

No evidence was found

Introduction of other substances

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

Evidence

This pressure is Not assessed.

De-oxygenation

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

Evidence

Nash et al. (2005) noted that aeration improved growth in culture. However, no other evidence on the effect of hypoxia on Trailliella was found.

Nutrient enrichment

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

Evidence

No information on the effects of nutrient enrichment on Trailliella was found. Nevertheless, this biotope is considered to be 'Not sensitive' at the pressure benchmark that assumes compliance with good status as defined by the WFD.

Organic enrichment

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

Evidence

No information on the effects of nutrient enrichment on Trailliella was found.

Physical loss (to land or freshwater habitat)

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

Evidence

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’).  Sensitivity within the direct spatial footprint of this pressure is, therefore ‘High’.  Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

Physical change (to another seabed type)

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

Evidence

If sedimentary substrata were replaced with rock substrata the biotope would be lost, as it would not longer be a sedimentary habitat.

Sensitivity assessment. Resistance to the pressure is considered ’None‘, and resilience ’Very low‘ or ‘None’ (as the pressure represents a permanent change) and the sensitivity of this biotope is assessed as ’High’.

Physical change (to another sediment type)

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

Evidence

This biotope is recorded from sandy gravelly muds (Connor et al., 2004, sediment matrix). Bonnemaisonia hamifera and Trailliella are found on other substrata, including rock and other seaweeds.  The low energy environment of the biotope, i.e. low water flow and wave sheltered conditions,  determines the nature of the sediment.  The muddy sediment is probably inhospitable to most other macroalgae so that Trailliella can become abundant.  However, it would probably grow on other sedimentary substrata under the same conditions.  Therefore, the biotope is probably Not sensitive (resistance and resilience are High).

Habitat structure changes - removal of substratum (extraction)

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

Evidence

The biotope is an epifloral mat sitting on the surface of the sediment. Extraction of the sediment to any depth would result in removal of the Trailliella mat from the affected area.  Therefore, a resistance of None is suggested. Resilience is probably Medium and sensitivity is assessed as Medium but with Low confidence due to the lack of any direct evidence.

Abrasion / disturbance of the surface of the substratum or seabed

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

Evidence

The biotope is an epifloral mat sitting on the surface of the sediment. Bonnemaisonia hamifera and Trailliella are known to fragment and disperse by drifting (Breeman et al., 1988).  Any passing bottom gear is liable to remove the mat of Trailliella. Similarly, as the Trailliella is delicate and filamentous it may also be easy to damage by trampling in the shallow subtidal and in rock pools.  Therefore, a resistance of Low is suggested. Resilience is probably High so that the sensitivity is assessed as Low at the benchmark level but with Low confidence due to the lack of any direct evidence.

Penetration or disturbance of the substratum subsurface

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

Evidence

The biotope is an epifloral mat sitting on the surface of the sediment. Bonnemaisonia hamifera and Trailliella are known to fragment and disperse by drifting (Breeman et al., 1988).  Any passing bottom gear or another activity that penetrates the surface of the sediment is liable to remove the mat of Trailliella.  Therefore, a resistance of Low is suggested. Resilience is probably High so that the sensitivity is assessed as Low at the benchmark level but with Low confidence due to the lack of any direct evidence.

Changes in suspended solids (water clarity)

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

Evidence

An increase in suspended sediment and, hence turbidity, will reduce the light available to macroalgae for photosynthesis and growth.  Nash et al. (2005) noted that Trailliella occurred in “more or less shaded” habitats, which explained its high growth potential in low photon irradiance in culture.  Breeman et al. (1988) showed that the Trailliella phase grew faster at 20 and 40 µmol/m²/s than at 10 µmol/m²/s  at 15-25°C.  Breenman & Guiry (1989) estimated that photo irradiances of about 10 µmol/m²/s were perceived as light but that 1-5 µmol/m2/s were perceived as darkness. They noted that about 10 µmol/m²/s could be reached at the sea surface at sunrise or sunset on bright days.  Breeman & Guiry (1989) reported that a change in the timing of high and low tide could affect the timing of reproduction in the tetrasporophyte (Trailliella), and Breeman et al. (1988) demonstrated that day length and temperature were important cues for reproduction in Bonnemaisonia hamifera.  Therefore, an increase in suspended sediment and the resultant decrease in light could affect reproduction and growth in Bonnemaisonia hamifera, especially in the deeper examples of the biotope. No information on the effects of scour was found.  Therefore, a resistance of Low is suggested with Low confidence. Resilience is probably High so that sensitivity is assessed as Low. 

Smothering and siltation rate changes (light)

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

Evidence

Bonnemaisonia hamifera gametophytes grow up to 35 cm in length but the tetrasporophyte Trailliella grows in dense cotton-wool-like tufts of up to 2.5 cm in diameter (Guiry & Guiry, 2015). Therefore, a deposit of 5 cm will completely smother a mat of Trailliella. The biotope is found in low energy habitats so that the deposited sediment is likely to remain and the mat is likely to die beneath the sediment.  Therefore, a resistance of None is suggested. Resilience is likely to be Medium and sensitivity is assessed as Medium but with Low confidence due to the lack of any direct evidence.

Smothering and siltation rate changes (heavy)

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

Evidence

Bonnemaisonia hamifera gametophytes grow up to 35 cm in length but the tetrasporophyte Trailliella grows in dense cotton-wool-like tufts of up to 2.5 cm in diameter (Guiry & Guiry, 2015). Therefore, a deposit of 30 cm will completely smother a mat of Trailliella. The biotope is found in low energy habitats so that the deposited sediment is likely to remain and the mat is likely to die beneath the sediment.  Therefore, a resistance of None is suggested. Resilience is likely to be Medium and sensitivity is assessed as Medium but with Low confidence due to the lack of any direct evidence.

Litter

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

Evidence

Not assessed.

Electromagnetic changes

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

Evidence

No evidence was found. 

Underwater noise changes

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

Evidence

Not relevant

Introduction of light or shading

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

Evidence

Nash et al. (2005) noted that Trailliella occurred in “more or less shaded” habitats, which explained its high growth potential in low photon irradiance in culture. Breeman et al. (1988) showed that the Trailliella phase grew faster at 20 and 40 µmol/m²/s than at 10 µmol/m²/s  at 15-25°C.  Breenman & Guiry (1989) estimated that photo irradiances of about 10 µmol/m²/s were perceived as light but that 1-5 µmol/m2/s were perceived as darkness. They noted that about 10 µmol/m²/s could be reached at the sea surface at sunrise or sunset on bright days.  Breeman & Guiry (1989) reported that a change in the timing of high and low tide could affect the timing of reproduction in the tetrasporophyte (Trailliella), and Breeman et al. (1988) demonstrated that day length and temperature were important cues for reproduction in Bonnemaisonia hamifera.  Therefore, an change in artificial light might change the timing of reproduction in both gametophytes and tetraporophytes and, as tetrasporogenesis is triggered by short days, might prevent the induction of reproduction in tetrasporophytes.  But growth of Trailliella might be increased in summer as Nash et al. (2005) found that  maximum biomass production of the (Trailliella phase) at 15-20°C, occurred in long day length (16:8 hrs L:D) in culture. Conversely, shading may reduce growth, or result in loss of the biotope if intense and permanent. Therefore, a resistance of Low is suggested with Low confidence. Resilience is probably High so that sensitivity is assessed as Low but with Low confidence due to the lack of any direct evidence.

Barrier to species movement

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

Evidence

Not relevant

Death or injury by collision

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

Evidence

The pressure definition is not directly applicable to seabed biotopes so Not relevant has been recorded.  Collision via ship groundings or terrestrial vehicles is possible but the effects are probably similar to those of abrasion above.

Visual disturbance

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

Evidence

Not relevant

Genetic modification & translocation of indigenous species

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

Evidence

No evidence of the translocation, breeding or species hybridization in 'Trailliella' phase of Bonnemaisonia hamifera was found.

Introduction or spread of invasive non-indigenous species

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

Evidence

Bonnemaisonia hamifera (and the Trailliella-phase) is a non-native species introduced to the British Isles from Japan and first recorded in 1890 (Dixon & Irvine, 1977; Maggs & Stegenga, 1998; Gollasch, 2006).  It is thought to have been introduced by shipping or with shellfish and to have dispersed by drifting on water currents (Gollasch, 2006).  Bonnemaisonia hamifera (and the Trailliella-phase) has spread around the British Isles and Europe, into the Mediterranean and the Canary Isles and north to the Orkneys and the Norwegian coast (Lüning, 1990, Maggs & Stegenga, 1998; Gollasch, 2006).  

No evidence of the effects of Bonnemaisonia hamifera on native flora or fauna was found.  And no evidence of the effects of other non-natives on Bonnemaisonia hamifera was found.

Introduction of microbial pathogens

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

Evidence

No evidence was found

Removal of target species

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

Evidence

Bonnemaisonia hamifera is unlikely to be targetted by any commercial or recreational fishery or harvest.

Removal of non-target species

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

Evidence

Accidental physical disturbance due to access (e.g. trampling), grounding, or passing fishing gear is examined under abrasion above. However, the accidental removal of the Trailliella mat would result in a significant change in the biological character of, and loss of,  the biotope. Therefore, a resistance of None is suggested. Resilience is probably Medium so that sensitivity is assessed as Medium but with 'Low' confidence.