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

Beggiatoa spp. mats have been reported from sulphur springs, deep water at ca 600 m, fjords, coastal marine sediments, salt marshes, organic-rich freshwater sediments, natural oil seeps and deep-sea hydrothermal vents (e.g. Spies & Davis, 1979; Hagen & Nelson, 1997). There was no information found regarding the temperature requirements of Beggiatoa, and the temperature requirements of individual strains of the bacterium are likely to vary. However, given its occurrence in the vicinity of hydrothermal vents, it is unlikely to be affected by increases in temperature at the benchmark level. In addition, Hiscock et al. (2001) suggested that increases in temperature because of global warming may result in more thermal stratification events in enclosed areas. Increased stratification will isolate deeper waters of sheltered sites and Beggiatoa spp. biotopes may occur where they did not previously exist. Therefore, resistance and resilience are probably High and the biotope is assessed as Not sensitive.

Temperature decrease (local)

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

Evidence

Beggiatoa spp. mats have been reported from sulphur springs, deep water at ca 600 m, fjords, coastal marine sediments, salt marshes, organic-rich freshwater sediments, natural oil seeps and deep-sea hydrothermal vents (e.g. Spies & Davis, 1979; Hagen & Nelson, 1997).  There was no information found regarding the temperature requirements of Beggiatoa, and the temperature requirements of individual strains of the bacterium are likely to vary.  However, its occurrence within the East Siberian Sea (OBIS, 2016) and the deep sea suggest it is unlikely to be affected by increases in temperature at the benchmark level. Therefore, resistance and resilience are probably High and the biotope is assessed as Not sensitive.

Salinity increase (local)

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

Evidence

There is no information regarding the development of Beggiatoa mats in hypersaline waters. Freshwater strains and marine strains are different so an increase in salinity in brackish water sites may remove the freshwater strains of the bacterium, e.g. freshwater strains were unable to grow in salty conditions (Williams & Unz, 1989). However, if conditions of high nutrient and low oxygen concentration remain mats may then be formed by marine strains. Therefore, a resistance of High is suggested but with low confidence. Hence, resilience is High and the biotope is assessed as Not sensitive.

Salinity decrease (local)

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

Evidence

Beggiatoa mats form in sewage waste water and in marine conditions. However, freshwater strains and marine strains are different so a decrease in salinity may remove the marine strains. For example, freshwater strains were unable to grow in salty conditions (Williams & Unz, 1989). However, if conditions of high nutrient and low oxygen concentration remain mats may then be formed by freshwater strains. Therefore, a resistance of High is suggested but with low confidence. Hence, resilience is High and the biotope is assessed as Not sensitive.

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

The biotope normally develops in areas of low water flow rate, such as sea lochs and fjords, where hypoxic or anoxic conditions are able to develop. Any further decrease in water flow is unlikely and assessed further. An increase in water flow is likely to result in increased mixing of the water column, and dispersal of any thermocline or halocline in the area, an increase in oxygenation of the water column and loss of the conditions required for growth of Beggiatoa spp.  In areas where anoxic or hypoxic conditions are caused by organic enrichment, then increased water flow is likely to mitigate and reduce the level of hypoxia. However, an increase of 0.1-0.2 m/s (the benchmark) may reduce the level of hypoxia in naturally hypoxic areas.  Therefore, a resistance of Low is suggested but with Low confidence. Resilience is likely to be High so that sensitivity is assessed as Low.

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

The pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.

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

The biotope develops in areas of very little water movement (wave sheltered to extremely wave sheltered conditions). Therefore, a further decrease in wave action is unlikely.  An increase in wave action is likely to wash the mats away and increase mixing or the water column and, hence, oxygenation. However, a 3-5% change in significant wave height is unlikely to have a significant effect, especially at depth.  Therefore, resistance and resilience are probably High and the biotope is assessed as Not sensitive.

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

In many areas around the world (e.g. see Spies & Davis, 1979) mats of Beggiatoa are associated with localized intense oil seepage and so the biotope is likely to be relatively resistant of hydrocarbons. Nevertheless, this pressure is Not assessed .

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

Jørgensen (1977) noted that Beggiatoa spp. was present in the upper few centimetres oxic sediment in Limfjorden, Denmark.  But mats of Beggiatoa are usually associated with hypoxic or anoxic conditions (Diaz & Rosenberg, 1995; Connor et al., 1997a,2004). For example, during the autumn of 1993 and 1994 when the oxygen content of the bottom water in the Koljoford on the west coast of Sweden dropped, Beggiatoa mats covered the seafloor (Gustafsson & Nordberg, 1999). In Maine coastal waters in the U.S.A, the formation of Beggiatoa mats was linked to lack of oxygen when current speed was reduced for 2 h or longer during a tidal cycle. The formation of Beggiatoa mats only occurs when oxygen supply is reduced below the threshold level required to oxidize sedimented organic matter (Findlay, 2002). In Caol Scotnish, Loch Sween, bacterial mats of Beggiatoa were reported in the immediate vicinity of salmon cages in 1987. By 1988, the bacterial mats covered most of the seabed in the basin and the sediment was close to anoxic (Atkinson, 1989; Hughes, 1998a).

Therefore, the development of the biotope is dependent on hypoxic and anoxic conditions in the sediment.  The biotope is assessed as Not sensitive  (resistance and resilience are High) to deoxygenation. However, the biotope would be destroyed and lost by increased oxygen levels.

Nutrient enrichment

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

Evidence

Mats of Beggiatoa are usually associated with and develop in the presence of high organic loadings such as found under salmon farm cages (Lumb, 1989; Davies et al., 1996, Atkinson, 1989) and coastal areas of eutrophication (Graco et al., 2001). Therefore, an increase in nutrients will encourage the development of the bacterial mats.  The biotope is probably Not sensitive (resistance and resilience are High) to nutrient enrichment. Nevertheless, the biotope is assessed as 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

Mats of Beggiatoa are usually associated with and develop in the presence of high organic loadings such as found under salmon farm cages (Lumb, 1989; Davies et al., 1996, Atkinson, 1989) and coastal areas of eutrophication (Graco et al., 2001). Therefore, an increase in nutrients will encourage the development of the bacterial mats.  The biotope is assessed as Not sensitive (resistance and resilience are High) to organic enrichment.

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 no longer be a sedimentary habitat as described under the habitat classification.  Jørgensen (1977) noted that Beggiatoa was absent from fine and medium sands in the Limfjorden, Denmark but abundant on muds. Therefore, a change to rock substratum would probably result in loss of Beggiatoa mats.

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

Beggiatoa spp. is recorded from muds and decaying plant matter (Jørgensen, 1977). Jørgensen (1977) noted that Beggiatoa was absent from fine and medium sands in the Limfjorden, Denmark but abundant on muds. Similarly, this biotope (IFiMu.Beg) is only recorded from muds (Connor et al., 2004). Therefore, a change in sediment type by one Folk class (see Long, 2006), e.g. from mud to sandy mud and sand would result in loss of the biotope. Therefore, a resistance of None is recorded. As the change is permanent, resilience is Very low and sensitivity is assessed as 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 mats of Beggiatoa spp. sit on the surface of the substratum. Extraction of sediment to 30 cm (the benchmark) could remove the bacterial mats in the affected area.  Hence, the resistance is probably None and resilience is probably High, resulting in a sensitivity of Medium.

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 bacteria produces a polysaccharide matrix that binds the bacteria together and to the substratum. But mats of Beggiatoa form on soft mud and so are likely to be broken up by abrasion or physical disturbance. Therefore, a resistance of Low is suggested with Low confidence. However, resilience is probably High so that the sensitivity is assessed as Low.

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 bacteria produces a polysaccharide matrix that binds the bacteria together and to the substratum. But mats of Beggiatoa form on soft mud and so are likely to be broken up by abrasion or physical disturbance. Therefore, a resistance of Low is suggested with Low confidence. However, resilience is probably High so that the sensitivity is assessed as Low.

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

Beggiatoa spp. has no dependency on light or detritus, and no feeding structures to clog with sediment. This biotope is recorded from sheltered areas, on fine sediments, subject to high suspended sediment loads. Therefore, resistance is probably High and, hence, resilience is also High, and the biotope is probably Not sensitive at the benchmark level.

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

Beggiatoa spp. sit at the anoxia / hypoxia interface and can ‘glide’ across the surface of the substratum. It occurs in muds in sheltered areas and is probably adapted to high sediment loads and accretion rates.  However, no information on rapid sedimentation was found. The bacterium is found within the top few centimetres of the sediment (Jørgensen, 1977) so that the bacterium itself would probably survive smothering but the mats would probably disappear temporarily.  Therefore, a resistance of Low is suggested with Low confidence but resilience is High so that the sensitivity is assessed as Low.

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

Beggiatoa spp. sit at the anoxia / hypoxia interface and can ‘glide’ across the surface of the substratum. It occurs in muds in sheltered areas and is probably adapted to high sediment loads and accretion rates.  However, no information on rapid sedimentation was found. The bacterium is found within the top few centimetres of the sediment (Jørgensen, 1977) so that the bacterium itself would probably survive smothering but the mats would probably disappear temporarily.  Therefore, a resistance of Low is suggested with Low confidence but resilience is High so that the sensitivity is assessed as Low.

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

Motile bacteria may respond to local vibration but the important characteristic species are unlikely to respond to noise as described under this pressure.
 

Introduction of light or shading

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

Evidence

Beggiatoa sp. utilize sulphides leaching from the sediment, and oxidize them to sulphate to liberate energy for growth but also require simple organic acids and alcohols for growth (Williams & Unz, 1989; Hagen & Nelson, 1997).The other organisms present (e.g. ciliates, nematodes, and euglenoid flagellates) are probably decomposers, feeding on organic matter. However, Bernhard et al. (2000) noted several species of protist contained symbiotic bacteria that were presumably chemoautotrophs. The sediment below the mats is populated by chemoautotrophic bacteria, that remineralize organic matter, producing methane, or sulphides of hydrogen (H₂S), iron or manganese and are probably very similar to microbial communities found at depth in other sediments (for a summary see Davies et al., 1996).  Therefore, the biotope has not dependency on light and resistance is assessed as High. Therefore, resilience is High and the biotope is assessed as Not sensitive.

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 - this pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit the dispersal of seed.  But seed dispersal is not considered under the pressure definition and benchmark.

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

Not relevant to seabed habitats. 

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 genetic modification, breeding, or translocation 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

No evidence 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

Beggiatoa spp. are unlikely to be targeted by commercial or recreational fisheries or other harvest. The presence of mats of Beggiatoa spp. indicate that conditions are anoxic and potentially abiotic.

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

The presence of mats of Beggiatoa spp. indicate that conditions are anoxic and potentially abiotic. Affected areas are unlikely to be targeted by commercial or recreational fisheries or other harvest.