Nephtys hombergii and Macoma balthica in infralittoral sandy mud

04-09-2007
Researched byGeorgina Budd Refereed byThis information is not refereed.
EUNIS CodeA5.331 EUNIS NameNephtys hombergii and Macoma balthica in infralittoral sandy mud

Summary

UK and Ireland classification

EUNIS 2008A5.331Nephtys hombergii and Macoma balthica in infralittoral sandy mud
EUNIS 2006A5.331Nephtys hombergii and Macoma balthica in infralittoral sandy mud
JNCC 2004SS.SMu.ISaMu.NhomMacNephtys hombergii and Macoma balthica in infralittoral sandy mud
1997 BiotopeSS.IMS.FaMS.MacAbrMacoma balthica and Abra alba in infralittoral muddy sand or mud

Description

Near-shore shallow muddy sands and muds, and sometimes mixed sediments, may be characterized by the presence of the bivalve Macoma balthica and Abra alba. Lagis koreni and Donax vittatus may also be significant components although they may not necessarily all occur simultaneously. Fabulina fabula, Nephtys cirrosa, Echinocardium cordatum and Crangon crangon may also be present. The community is especially stable (Dewarumez et al., 1992). The substratum is typically rich in organic content and the community may occur in small patches or swathes in shallow waters parallel to the shore (Jones, 1950; Cabioch & Glaçon, 1975). This biotope is known to occur in patches between Denmark and the western English Channel. This community has been included in the 'Boreal Offshore Muddy Sand Association' of Jones (1950) and is also described by several other authors (Petersen, 1918; Cabioch & Glaçon, 1975). A similar community may occur in deep water in the Baltic (Thorson, 1957). This biotope may occur in slightly reduced salinity estuarine conditions where Mya sp. may become a significant member of the community (Thorson, 1957). Sites with IMS.MacAbr may give over to neighbouring Amphiura biotopes with time (E.I.S. Rees pers. comm. 1996). (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Recorded distribution in Britain and Ireland

The IMS.MacAbr biotope is present in coastal inlets of south west Britain, patches through northern Irish Sea and patches throughout. Also present in the Southern Bight, North Sea and in the English Channel.

Depth range

-

Additional information

No text entered.

Listed By

Further information sources

Search on:

JNCC

Habitat review

Ecology

Ecological and functional relationships

  • Predation in the biotope can be an important structuring force. Predators in the biotope may include small fish (Pomatoschistus microps and Pomatoschistus minutus) and juvenile flatfish (Platichthys flesus) in addition to the burrowing polychaete Nephtys hombergii, and the shrimp Crangon crangon.
  • The brown shrimp Crangon crangon is one of the most important epibenthic predators on shallow sandy bottom communities. Mattila et al., (1990) found that Crangon crangon had a great potential to affect many infaunal species. For instance, the presence of Crangon crangon in experimental studies affected both the densities and size frequencies of Macoma balthica. At times when the shrimp is most abundant it may have some importance as a regulating predator on shallow soft substratum communities (Mattila et al., 1990).
  • However, surface and sub-surface deposit feeders are particularly characteristic of this biotope. Bivalve molluscs that inhabit muddy low energy environments tend to deposit feed, although several species including Macoma balthica and Abra alba may also suspension feed. For instance, switching between the modes of feeding in Macoma balthica was directly affected by food availability in the over-lying water (Lin & Hines, 1994). When deposit feeding, bivalves remove phytoplankton, microzooplankton, organic and inorganic particles, and microbes including bacteria, fungi and microalgae. They also probably absorb dissolved organic materials in much the same manner as when filter feeding (Dame, 1996). Deposit feeding bivalves adopt two approaches to feeding; bulk feeding and particle sorting. Some may ingest large amounts of sediment in a relatively nonselective manner, or may sort particles before they are ingested and reject the majority as pseudofaeces. Deposit feeding bivalves may process up to 20 times their body weight in sediments per hour with as much as 90 % of the sediment egested as pseudofaeces (Lopez & Levinton, 1987). Consequently, the resultant bioturbation is likely to alter the characteristics of the substratum and possibly the associated infaunal community. Furthermore, as a result of feeding and metabolism, bivalve molluscs excrete both particulate and dissolved materials that may be utilized by the benthos and plankton. Thus bivalves play an important role in the cycling of nutrients in such systems (Dame, 1996).
  • When suspension feeding, bivalves pump large volumes of water and concentrate many chemicals by several orders of magnitude greater in their body tissues than are found in surrounding seawater (Dame, 1996).
  • Macoma balthica is not normally considered to be toxic but may transfer toxicants through the food chain to predators. Macoma balthica was implicated in the Mersey bird kill in the late 1970's, owing to bioconcentration of alklyC-lead residues (Bull et al., 1983).

Seasonal and longer term change

Seasonal changes are likely to occur in the abundance of fauna in the biotope due to seasonal recruitment processes and variations in recruitment success. For example, in the case of Macoma balthica, Bonsdorff et al. (1995) reported juvenile density in the Baltic Sea following settlement in late summer to be 300,000/m decreasing to a stable adult density of 1,000/m, and Ratcliffe et al. (1981) reported adult densities in the Humber Estuary, UK, to be between 5,000/m and 40,000/m depending on time since a successful spatfall. Furthermore, Macoma balthica may make seasonal migrations in response to environmental conditions. Beukema & De Vlas (1979) reported that 30% of the Macoma balthica population migrated into the subtidal during winter apparently in response to low temperatures. Migration was achieved by burrowing (Bonsdorff, 1984; Guenther, 1991) and/or floating (Sörlin, 1988).
One of the key factors affecting benthic habitats is disturbance which, in shallow subtidal habitats, may increase in winter due to adverse weather conditions. Storms may cause dramatic changes in distribution of infauna by washing out dominant species, opening the sediment to recolonization by adults and/or available spat/larvae (Eagle, 1975; Rees et al., 1977; Hall, 1994) and by reducing success of recruitment by newly settled spat or larvae (see Hall, 1994 for review).

Habitat structure and complexity

  • The muddy sand / mud substratum of the biotope has little structural diversity provided by either physiographic features or the biota. Some 3-dimensional structure is provided by the burrows of infauna e.g. Nephtys hombergii, whilst Lagis koreni builds itself a rigid tube of sand grains which lies either diagonally or nearly upright in the sediment (Fish & Fish, 1996). Most species living within the sediment are limited to the area above the anoxic layer, the depth of which will vary depending on sediment particle size and organic content. However, the presence of burrows allows a larger surface area of sediment to become oxygenated, and thus enhances the survival of a considerable variety of small species (Pearson & Rosenberg, 1978).

  • Reworking of sediments by deposit feeders increases bioturbation and potentially causes a change in the substratum characteristics and the associated community (e.g. Rhoads & Young, 1970). For example, Widdows et al. (1998) reported that typical abundances (ca 100 - 1000 per m²) of Macoma balthica increased sediment re-suspension and/or erodability four fold and that there was a significant positive correlation between density of the species and sediment resuspension.

    Productivity

    Macroalgae are absent from IMS.MacAbr and consequently productivity is mostly secondary derived from detritus and organic material, although shallower sites may develop an extensive growth of benthic diatoms in the summer. Allochthonous organic material may be derived from anthropogenic activity (e.g. sewerage) and natural sources (e.g. plankton, detritus). Autochthonous organic material is formed by benthic microalgae (microphytobenthos e.g. diatoms and euglenoids) and heterotrophic micro-organism production. Organic material is degraded by micro-organisms and the nutrients recycled. The high surface area of fine particles provides substratum for the microflora.

    Recruitment processes

    Bivalve molluscs:
    • The bivalves which characterize the biotope are capable of high recruitment and rapid recovery. For example, adult Macoma balthica spawn at least once a year and are highly fecund (Caddy, 1967). There is a planktotrophic larval phase which lasts up to 2 months (Fish & Fish, 1996) and so dispersal over long distances is potentially possible given a suitable hydrographic regime. Following settlement, development is rapid and sexual maturity is attained within 2 years (Gilbert, 1978; Harvey & Vincent, 1989). The exact time at which maturity was attained depended upon the size of the individual, but it seemed that a minimum shell length of between 7-9 mm was typical (Nott, 1980). Normally, for Abra alba there two distinct spawning periods, in July and September and according to the season of settlement, individuals differ in terms of growth and potential life span (Dauvin & Gentil, 1989). Autumn settled individuals from the Bay of Morlaix, France, initially showed no significant growth; they were not collected on a 1 mm mesh sieve until April, 5 to 7 months after settlement. Such individuals were expected to have a maximum life span of 21 months and could produce two spawnings. In contrast, veliger larvae that settled during the summer grew very rapidly and were collected on a 1 mm mesh sieve just one month after settlement. They lived about one year and spawned only once (Dauvin & Gentil, 1989).
    • Recruitment in bivalve molluscs is influenced by larval and post-settlement mortality. Typically bivalves are fecund and egg production increases with female size, however, the high potential population increase is offset by high larval and juvenile mortality, but, juvenile mortality rapidly decreases with age (Brousseau, 1978b; Strasser, 1999). Larval mortality results from predation during pelagic stages, predation from suspension feeding macrofauna (including conspecific adults) during settlement and from deposition in unsuitable habitats. Mortality of the juveniles of marine benthic invertebrates can exceed 30% in the first day, and several studies report 90% mortality (Gosselin & Qian, 1997). In addition to larval dispersal, dispersal of juveniles and adults occurs via burrowing (Bonsdorff, 1984; Guenther, 1991), floating (Sörlin, 1988) and probably via bedload transport (Emerson & Grant, 1991). It is expected therefore that recruitment can occur from both local and distant populations.
      For specific information concerning the reproduction and longevity of Macoma balthica, Abra alba, Fabulina fabula and Mya arenaria, refer to MarLIN reviews for these species.

    Polychaete worms:
    • Lagis koreni has separate sexes and breeding occurs during spring and summer. The larvae have a planktonic life of about one month and total length of life is thought to be about one year. The worms breed once then die (Fish & Fish, 1996).
    • Nephtys hombergii matures between two and three years of age and breeds during April and May. The worms remain in situ within the sediment during spawning and eggs and sperm are released on to the surface of the sediment, fertilization occurs when gametes are mixed by the incoming tide or by water currents. Larval development occurs within the plankton. Nephtys hombergii may live for up to six years (Fish & Fish, 1996).
    Crustaceans:
    • The brown shrimp, Crangon crangon, reaches maturity after 1-2 years and the sexes are believed to be separate, although there are suggestions that the species is a protandrous hermaphrodite. Once hatched the larval life lasts for five weeks. A typical life span is three years and during that time a female may produce over 30,000 eggs (Fish & Fish, 1996).
    Echinoderms:
    • Subtidal populations of Echinocardium cordatum are reported to reproduce sporadically. One population recruited in only three years over a ten year period (Buchanan, 1966). The species is fecund (> 1, 000, 000 eggs), breeds between spring and summer, with a life span of between 10 and 20 years.

    Time for community to reach maturity

    The life history characteristics of the species which characterize the biotope suggest that the biotope would recover from major perturbations and be recognisable as the biotope within 5 years. For instance, Abra alba and Macoma balthica demonstrate an 'r' type life-cycle strategy and are able to rapidly exploit any new or disturbed substratum available for colonization through larval recruitment, secondary settlement of post-metamorphosis juveniles or re-distribution of adults. Bonsdorff (1984) studied the recovery of a Macoma balthica population in a shallow, brackish bay in SW Finland following removal of the substratum by dredging in the summer of 1976. Recolonization of the dredged area by Macoma balthica began immediately after the disturbance to the sediment and by November 1976 the Macoma balthica population had recovered to 51 individuals/m. One year later there was no detectable difference in the Macoma balthica population between the recently dredged area and a reference area elsewhere in the bay. In 1976, 2 generations could be detected in the newly established population indicating that active immigration of adults was occurring in parallel to larval settlement. In 1977, up to 6 generations were identified, giving further evidence of active immigration to the dredged area. Abra alba recovered to former densities following loss of a population from Keil Bay owing to deoxygenation within 1.5 years, as did Lagis koreni, taking only one year (Arntz & Rumohr, 1986). Such evidence suggests that recoverability of the key functional and important characterizing species of the IMS.MacAbr biotope would be typically be high. However, the recovery of Echinocardium cordatum may take longer owing to recruitment that is frequently unsuccessful (Rees & Dare, 1993).

    Additional information

    No text entered.

Preferences & Distribution

Recorded distribution in Britain and IrelandThe IMS.MacAbr biotope is present in coastal inlets of south west Britain, patches through northern Irish Sea and patches throughout. Also present in the Southern Bight, North Sea and in the English Channel.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients
Salinity
Physiographic
Biological Zone
Substratum
Tidal
Wave
Other preferences

Additional Information

No text entered.

Species composition

Species found especially in this biotope

    Rare or scarce species associated with this biotope

    -

    Additional information

    No text entered

    Sensitivity reviewHow is sensitivity assessed?

    Explanation

    The bivalves Macoma balthica and Abra alba are particularly characteristic of the biotope but owing to their deposit feeding activity and the densities at which they may occur (> 1000 per m²) these species have been given key functional status. The manner in which such bivalves intensively rework the uppermost few centimetres of the sediment produces a fluid faecal-rich layer, the physical instability of which tends to inhibit the development of a benthic suspension feeding community or relatively sessile epifauna (see review by Rhoads & Young, 1970). Consequently, the feeding activity of the bivalves maintains community structure and function. Other infaunal burrowing species such as Echinocardium cordatum are considered to be important functional species because their deeper burrows enhance the oxygenation of the substratum and enhance the survival of a variety of small species (Pearson & Rosenberg, 1978). The presence of the polychaete Lagis koreni is considered important for the classification of the biotope. The brown shrimp, Crangon crangon is an important other species, whilst it may not be highly faithful to the biotope, its presence does however affect the sensitivity of the biotope as it is the target of a commercial fishery.

    Species indicative of sensitivity

    Community ImportanceSpecies nameCommon Name
    Key functionalAbra albaA bivalve mollusc
    Important otherCrangon crangonBrown shrimp
    Important functionalEchinocardium cordatumSea potato
    Important characterizingLagis koreniA bristleworm
    Key functionalMacoma balthicaBaltic tellin
    Important characterizingNephtys hombergiiA catworm

    Physical Pressures

     IntoleranceRecoverabilitySensitivitySpecies RichnessEvidence/Confidence
    High High Moderate Major decline High
    Muddy sand communities are highly intolerant of substratum loss because most species are infaunal and so will be removed. A few mobile demersal species like the shrimp Crangon crangon may be able to avoid the factor. However, owing to the loss of the characterizing and important functional infaunal species the biotope would not be recognized so intolerance has been assessed to be high. Recoverability has been assessed to be high (see additional information below).
    Tolerant Not relevant Not relevant Not relevant Low
    The biotope is characterized by mostly burrowing bivalve species, polychaete worms and macrofauna such as the heart urchin Echinocardium cordatum and brown shrimp, Crangon crangon. The biotope has been assessed to be not sensitive to smothering by 5 cm of additional sediment as the infauna should be able to burrow upwards (Schafer, 1972; Rees & Dare, 1993) or are sufficiently mobile to avoid the factor. However, a higher intolerance would be expected following smothering by other materials that are very viscous or impermeable.
    Tolerant* Not relevant Not sensitive* Rise Moderate
    Deposit feeders are the dominant trophic group in this biotope and therefore are not directly reliant on suspended matter as a food resource, although Macoma balthica, Abra alba and Fabulina fabula are also facultative filter feeders and may switch to suspension feeding should the food supply become more profitable (Lin & Hines, 1994; Salzwedel, 1979). An increase in suspended sediment will increase the rate of siltation at the sediment surface, potentially enhancing the food supply for all deposit feeders in the biotope. The community of the biotope has been assessed to be not sensitive* with the potential for growth and reproduction to be enhanced by the enhanced food supply.
    Low Very high Moderate Minor decline Low
    Deposit feeders are the dominant trophic group in this biotope and therefore are not directly reliant on suspended matter as a food resource. However a decrease in siltation may result in a decreased rate of deposition on the substratum surface and therefore a reduction in food availability for deposit feeders. This would be likely to impair growth and reproduction. The benchmark states that this change would occur for one month and therefore would be unlikely to cause mortality. An intolerance of low is therefore recorded. As soon as suspended sediment levels increase, feeding activity would return to normal and hence recovery is recorded as very high.
    Not relevant Not relevant Not relevant Not relevant Not relevant
    The biotope occurs in the shallow sublittoral where it is continually immersed.
    Not relevant Not relevant Not relevant Not relevant Not relevant
    The biotope occurs in the shallow sublittoral where it is continually immersed.
    Not sensitive* Not relevant
    The biotope occurs in the shallow sublittoral where it is continually immersed so that a decrease in emergence would not have an effect.
    High High Moderate Decline Moderate
    The intensive working of the uppermost few centimetres of the sediment by the largely deposit feeding community, especially bivalves, produces a fluid faecal-rich surface that is easily re-suspended by even low velocity tidal currents (Rhoads & Young, 1970). The biotope is found in locations of weak (< 0.5 m/sec) water flow, so the benchmark increase would expose the biotope to strong currents (1.5 -3 m/sec). Over the period of one year loss of the muddy sand surface substratum is likely along with much of the organic matter which the infaunal deposit feeders consume. Whilst infaunal species buried relatively deeply, such as Echinocardium cordatum are unlikely to be washed out, smaller bivalves buried at shallower depths may be periodically displaced. The intolerance of the biotope has been assessed to be high owing to the fact that the biotope may begin to change to another and that benthic food deposits may become limiting. Recoverability has been assessed to be high as a result of recruitment and probable migration from surrounding areas (see additional information below).
    Tolerant Not sensitive* No change Low
    The IMS.MacAbr biotope occurs in areas of weak water flow so the benchmark decrease in water flow rate will expose the community to conditions of almost negligible water flow. Whilst a decreased water flow would favour the deposition of particulate organic matter from suspension, the additional food resource is unlikely to be of any particular significance in this already organically enriched environment. More importantly, a decreased water flow rate may limit the dispersion of planktonic larvae, to the extent that larvae settle back into the parent population where larvae in the earliest stages are likely to be preyed upon by deposit feeders, including their parents. An intolerance assessment of low has been made owing to the reduced viability of the population that may result from poor larval recruitment. Recovery has been assessed to be very high as the adults of the important characterizing species will remain and produce again, with the exception of Lagis koreni, which, produces once then dies. However, larval plankton of this species are likely to be transported into the biotope from other locations and re-colonization of the substrata may also occur through re-distribution of adults.
    Low Immediate Not sensitive No change Moderate
    The key functional species Macoma balthica and Abra alba have a geographical distribution that extends to the south of the British Isles, so it is probable that the species would be tolerant of higher temperatures than experienced around Britain and Ireland. Macoma balthica proved to be very tolerant of higher temperatures, for instance it was maintained for six hours at 37.5 °C without death (Ratcliffe et al., 1981) and tolerated temperatures up to 49 °C before thermal numbing of the gill cilia occurred presumably caused death (Oertzen, 1969). The growth of Fabulina fabula (studied as Tellina fabula) correlated positively with water temperature increases up to 16 °C after which temperature increase inhibited growth (Salzwedel, 1979), a similar pattern might be inferred for Abra alba as it is a closely related species. Considering that maximum sea surface temperatures around the British Isles rarely exceed 20 °C (Hiscock, 1998), it is unlikely that the species of this biotope would suffer any mortality as a result of the benchmark increase in temperature. Elevated temperatures may initially enhance growth but later inhibit it as a result of energetic cost associated with sub-optimal metabolic function, therefore intolerance has been assessed to be low. Metabolic activity should return to normal within a few days or weeks at lower temperatures so recoverability has been assessed to be immediate.
    Intermediate High Low Decline Moderate
    Macoma balthica was apparently unaffected by the severe winter 1962/3 which decimated populations of other bivalves. Arntz & Rumohr (1986) noted the intolerance of Abra alba to extreme low temperatures in Kiel Bay with recovery to former densities taking some two years. Significant mortality of coastal populations of Echinocardium cordatum was reported from around the British Isles and in the German Bight during the severe winter of 1962/63 (Crisp, 1964; Ziegelmeier, 1978). Arntz & Rumohr (1986) reported Lagis koreni to be intolerant of extremely low bottom temperatures. Intolerance has been assessed to be intermediate as the populations of a key/important functional and important characterizing species may be partially destroyed by the factor. Recoverability has been assessed to be high (see additional information below).
    Low Very high Very Low No change Low
    Primary production in the biotope is not significant. An increase in turbidity is therefore not likely to have a significant effect on the biotope directly. The benthic fauna rely on nutrient input from pelagic and coastal fringe production (Barnes & Hughes, 1992). Increased turbidity in these areas may reduce primary production and consequently reduce the food supply to the benthos. The fauna in the IMS.MacAbr biotope may therefore suffer decreased growth and reproduction. However, the nutrient input to the biotope originates from a very wide area and the decrease in food supply is not likely to cause mortality over a year so the biotope intolerance is assessed as low. Primary production would be stimulated as turbidity decreased so recoverability has been assessed to be very high.
    Tolerant Not sensitive* No change Moderate
    A decrease in turbidity will mean more light is available for photosynthesis by phytoplankton in the water column and microphytobenthos on the sediment surface. This would increase primary production and may mean greater food availability for facultative suspension feeders and eventually deposit feeders. However, primary production is not a major source of production in the biotope so the turbidity decrease is not likely to have a significant effect. The benthos is probably supported predominantly by detrital materials emanating from the coastal fringe and by pelagic production (Barnes & Hughes, 1992). The biotope has been assessed to be not sensitive to this factor.
    Intermediate High Low Decline Moderate
    Where the biotope occurs in the shallow sublittoral e.g. in the organically rich inshore sediments off estuary mouths, the community may be vulnerable to wave-induced bottom disturbance. Increased wave action is likely to affect the community in several ways, for instance, erosion of muddy sand sediments is probable resulting in the reduction of the available habitat. Wave action is likely to cause bivalve species to withdraw their siphons, resulting in loss of feeding opportunities and compromised growth. The infauna may be dislodged. For instance, Rees et al (1977) recorded strandings of Lagis koreni and mass stranding of Echinocardium cordatum following storms on the North Wales coast. Intolerance has been assessed to be intermediate as populations within the biotope are likely to be reduced by the factor and that the habitat may be partially destroyed. Recoverability has been assessed to be high (see additional information below).
    Tolerant Not sensitive* No change Low
    The biotope occurs in locations sheltered from wave exposure so is likely to be intolerant of a further decrease this factor.
    Tolerant Not relevant Not relevant Not relevant Moderate
    Macoma balthica was able to detect shear-wave vibrations that propagate along the sediment surface in the frequency range 50-200 Hz. Its response consisted of frequent and intense digging attempts (Franzen, 1995). However, no other information concerning noise detection amongst other species of this biotope was found. Macoma balthica is likely to remain buried or take immediate avoidance action in response to this factor, probably without detectable effect upon its viability. Therefore the biotope has been assessed to be not sensitive to this factor.
    Tolerant Not relevant Not relevant Not relevant Low
    The majority of the species particularly characteristic of this biotope are infaunal and have little or no visual acuity. Epibenthic predators such as Crangon crangon and fish have visual acuity and may be temporarily scared away or cease hunting in response to the visual presence of objects not normally found in the marine environment (see benchmark). However, the biotope is unlikely to be affected as the infauna will remain in situ. Therefore an assessment of not sensitive has been made.
    Intermediate High Low Decline Moderate
    The relatively delicate shells of the bivalves that characterize this biotope are vulnerable to physical damage. The biotope community may be subjected to more intense abrasive / physical disturbance from otter and beam trawls used to capture the brown shrimp, Crangon crangon.

    Bergman & van Santbrink (2000) suggested that the megafauna such as Echinocardium cordatum, Corystes cassivelaunus, and bivalves such as Phaxas pellucidus, Dosinia lupinus, Mactra corallina, Abra alba, Spisula solida and Spisula subtruncata were amongst the species most vulnerable to direct mortality due to bottom trawling in sandy sediments. Bivalves such as Ensis spp.,
    Corbula gibba and Chamelea gallina together with starfish were relatively resistant (Bergman & van Santbrink, 2000). Bradshaw et al. (2000) suggested that fragile species such a urchins (e.g. Spatangus purpureus and Echinus esculentus), the brittlestar Ophiocomina nigra, starfish Anseropoda placenta and the edible crab Cancer pagurus suffered badly from impact with a passing scallop dredge. More robust bodied or thick shells species were less sensitive. Overall, species with brittle, hard tests are regarded to be sensitive to impact with scallop dredges (Kaiser & Spencer, 1995; Bradshaw et al., 2000). However, the small size of Macoma balthica and Abra alba relative to the gear and meshes of commercial trawls may ensure survival of at least a moderate proportion of disturbed individuals which pass through.

    Abra alba and Macoma balthica demonstrate an 'r' type life-cycle strategy and are able to rapidly exploit any new or disturbed substratum available for colonization through larval recruitment, secondary settlement of post-metamorphosis juveniles or re-distribution of adults. Bonsdorff (1984) studied the recovery of a Macoma balthica population in a shallow, brackish bay in SW Finland following removal of the substratum by dredging in the summer of 1976. Recolonization of the dredged area by Macoma balthica began immediately after the disturbance to the sediment and by November 1976 the Macoma balthica population had recovered to 51 individuals/m². One year later, there was no detectable difference in the Macoma balthica population between the recently dredged area and a reference area elsewhere in the bay. In 1976, 2 generations could be detected in the newly established population indicating that active immigration of adults was occurring in parallel to larval settlement. In 1977, up to 6 generations were identified, giving further evidence of active immigration to the dredged area. Abra alba recovered to former densities following loss of a population from Keil Bay owing to deoxygenation within 1.5 years (Arntz & Rumohr, 1986).

    Effects on other infauna would depend upon the depth penetration of the gear, relative to the distribution of animals in the sediments but significant trawl-induced mortality has been reported for Echinocardium cordatum (De Groot & Apeldoorn 1971; Rauck, 1988). Furthermore, Lagis koreni is incapable of reconstructing its delicate sand-tube once removed from it (Schafer, 1972), and hence mortality following physical disturbance would be expected to be high for this species in particular. Therefore, an overall biotope intolerance of intermediate has been recorded. Recoverability has been assessed to be high (see additional information below).

    Intermediate Immediate Very Low Minor decline Low
    The bivalve species of this biotope are likely to be tolerant of displacement owing to their burrowing ability. For example, Macoma balthica is able to rebury itself within 17 minutes when placed on the surface of a suitable substratum (McGreer, 1979), the other bivalves would be expected to behave in a similar manner, as would Echinocardium cordatum. However, the polychaete Lagis koreni is incapable of reconstructing its delicate sand-tube once removed from it (Schafer, 1972), and hence mortality following displacement would be expected to be high for this species in particular. The intolerance of this biotope has been assessed to be intermediate owing to mortality of an important characterizing species and the fact that normally infaunal species displaced to the surface will be prone to predation by fish and the shrimp Crangon crangon. On balance recoverability is likely to be immediate as the species would seek protection and any that were lost to predators would be replaced by new recruits within the year.

    Chemical Pressures

     IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
    High High Moderate Decline Moderate
    Deposit feeding may be a particularly important route for exposure to toxins within this biotope. Beaumont et al. (1989) concluded that bivalves were particularly sensitive to tri-butyl tin (TBT), the toxic component of many antifouling paints. For example, when exposed to 1-3 µg TBT/l, Cerastoderma edule and Scrobicularia plana suffered 100% mortality after 2 weeks and 10 weeks respectively. There is also evidence that TBT caused recruitment failure in bivalves, either due to reproductive failure or larval mortality (Bryan & Gibbs, 1991). Abra alba failed to burrow into sediment contaminated with pesticides (6000 ppm parathion, 200 ppm methyl parathion and 200 ppm malathion) (Møhlenberg & Kiørboe, 1983), such behaviour would make it prone to predation.
    Detergents used to disperse oil from the Torrey Canyon oil spill caused mass mortalities of Echinocardium cordatum (Smith, 1968) and its intolerance to TBT was similar to that of other benthic organisms with LC50 values of 222 ng Sn/l in pore water and 1594 ng Sn/g dry weight of sediment (Stronkhorst et al., 1999). Owing to evidence of mortalities, recruitment failure and disrupted behaviour experienced by key and important functional species of the biotope, intolerance has been assessed to be high. Recovery would be expected following degradation of the contaminants and recoverability has been assessed to be high (see additional information below).
    Heavy metal contamination
    Intermediate High Low Decline Moderate
    There is evidence of both lethal and sub-lethal effects upon Macoma balthica as a result of exposure to heavy metal pollution (McGreer, 1979; Luoma et al., 1983; Boisson et al., 1998). Other bivalves in the biotope are also likely to be intolerant of heavy metal pollution as bivalves tend to accumulate heavy metals in their tissues far in excess of environmental levels. Reactions to sub-lethal levels of heavy metal stressors include siphon retraction, valve closure, inhibition of byssal thread production, disruption of burrowing behaviour, inhibition of respiration, inhibition of filtration rate, inhibition of protein synthesis and suppressed growth (see review by Aberkali & Trueman, 1985). Bryan (1984) stated that Hg was the most toxic metal to bivalve molluscs while Cu, Cd and Zn seemed to be most problematic in the field. In bivalve molluscs Hg was reported to have the highest toxicity, mortalities occurring above 0.1-1 µg/l after 4-14 days exposure (Crompton, 1997), toxicity decreasing from Hg > Cu and Cd > Zn > Pb and As > Cr ( in bivalve larvae, Hg and Cu > Zn > Cd, Pb, As, and Ni > to Cr). Owing to evidence in the literature of sub-lethal effects and mortality of bivalves, the intolerance of the characteristic bivalve community inhabiting this biotope to heavy metal contamination has been assessed to be intermediate and species richness is expected to decline. In the absence the biotope may begin to change to another. Furthermore, echinoderms are also regarded as being intolerant of heavy metals (e.g. Bryan, 1984; Kinne, 1984) while polychaetes are often more tolerant (Bryan, 1984). Recovery is likely to be high but would be dependent on the removal of the contaminant.
    Hydrocarbon contamination
    High High Moderate Major decline High
    Stekoll et al. (1980) reported a range of behavioural, physical, physiological and biochemical changes prior to death following exposure to Prudhoe Bay crude oil at varying concentrations (0.03; 0.3 and 3.0 mg /l). Effects included inhibition of growth, reabsorption and abnormalities of the gonads, emergence from the substratum and poor orientation in addition to increased mortality at the highest concentration. Stekoll et al. (1980) concluded that chronic exposure of Macoma balthica to oil-in-seawater concentrations even as low as 0.03 mg/l would in time lead to population decreases. The specimens used by Stekoll et al., (1980) were not subjected to any of the stresses that normally occur in their natural environments so intolerance would be expected to be higher in field conditions. Macoma balthica was considered to be a key functional species of this biotope and is also characteristic. If Macoma balthica was lost from the biotope as a result of hydrocarbon pollution, the biotope would not be recognized so intolerance has been assessed to be high. Recoverability has been assessed to be high assuming contamination is removed (see additional information below).
    Radionuclide contamination
    No information Not relevant No information Not relevant Not relevant
    There is insufficient information concerning the biological effects of radionuclide contamination to assess the intolerance of this biotope.
    Changes in nutrient levels
    Tolerant* Not relevant Not sensitive* No change Moderate
    Macoma balthica and Abra alba are reported to favour organic enrichment. Madsen & Jensen (1987) reported increased shell growth, productivity : biomass radio and improvement in 'condition index' of Macoma balthica in organically enriched areas of the Dutch Wadden Sea, which was presumably due to the increased food supply. Furthermore, as Macoma balthica is relatively tolerant to periodic deoxygenation (an associated consequence of nutrient enrichment) it is likely that it will benefit from nutrient enrichment at the benchmark level. Abra alba increased its reproductive output to three spawning as opposed to its normally occurring twice yearly recruitment, as an adaptive response to eutrophic conditions that followed the Amoco Cadiz oil spill (Dauvin & Gentil, 1989). Lagis koreni may favour moderate organic enrichment, but it is displaced in anoxic sediments (Pearson & Rosenberg, 1978). Growth levels of Echinocardium cordatum have been observed to be lower in sediments with high organic content although it is suggested that this may be due to higher levels of intraspecific competition (Duineveld and Jenness, 1984). Owing to the evidence of improved condition, growth and reproductive output in the bivalve species that are key functional species, the biotope has been assessed to be not sensitive* to nutrient enrichment at the benchmark level.
    Not relevant Not relevant Not relevant Not relevant Not relevant
    The IMS.MacAbr biotope occurs in 'full' salinity conditions (Connor et al., 1997a) and therefore an increase in salinity was considered not to be a relevant factor.
    Low Very high Moderate Minor decline Low
    IMS.MacAbr occurs in 'full' salinity conditions (Connor et al., 1997a) and therefore is likely to be intolerant of salinity decreases in some way. The benchmark decrease in salinity would place the biotope in areas of variable salinity for one year or reduced salinity for one week. Biotope intolerance is dependent on the intolerance of the characterizing species. For example, although Macoma balthica is found in brackish and fully saline waters (Clay, 1967b) survival times of Macoma balthica declined with decreasing salinity (McLusky & Allan, 1976). Abra alba and Fabulina fabula are typically found in full salinity conditions and are therefore likely to be intolerant of reductions in salinity in some way. Salzwedel (1979) reported Fabulina fabula to occur in variable salinity conditions (down to 20 psu) but that growth was inhibited. Echinoderms are considered to be stenohaline animals that lack the ability to osmo- and ion-regulate (Stickle & Diehl, 1987). However, Echinocardium cordatum was recorded from brackish waters in the Delta region of the Netherlands to about the 15 psu isohaline (Wolff, 1968), so may be able to tolerate the stress for the given time period. Decreased salinity is likely to cause inhibition of growth and reproduction and hence reduce viability therefore intolerance has been assessed to be low. Recoverability has been assessed to be high as on return to prior conditions growth and reproduction would probably return rapidly to normal and recruitment would compensate for any vulnerable individuals lost.
    Low High Low Decline High
    Jorgensen (1980) observed the response of macrofauna to reduced dissolved oxygen levels of 0.2 to 1 mg/l for a period of 3 to 4 weeks in an estuarine/marine area in Sweden by diving. The shrimp Crangon crangon was amongst the first to die from lack of oxygen. Polychaetes were observed to come to the surface, small specimens first. Lagis koreni was observed limp and motionless on the surface but could be revived in 30 minutes by placing in oxygenated water. Nichols (1977) reported high mortality of Lagis koreni in association with periodic oxygen deficiency of the bottom waters of Kiel Bay, however it was capable of reaching former densities within a year following larval recruitment. During periods of hypoxia, burrowing bivalves were first observed to extend their siphons further into the water column but, as oxygen depletion continued, they emerged and laid on the sediment surface. For instance, Macoma balthica lay upon its side with the foot and siphons retracted but with valves gaping slightly allowing the mantle edge to be brought into full contact with more oxygenated water (Brafield & Newell, 1961). Furthermore, Macoma balthica proved to be resistant to anoxia for periods of up to 70 days at 5 °C and 11 days at 20 °C (Dries & Theede, 1984). Abra alba became inefficient in its use of available organic matter over a period of prolonged hypoxia (93 days) in an experiment to examine the interaction between eutrophication and oxygen deficiency (Hylland et al., 1996). Abra alba was also reported to be intolerant of lowered oxygen concentrations arising from eutrophication off the Swedish west coast (Rosenberg & Loo, 1988), whilst lethal effects were noted by Weigelt & Rumohr (1986) and Arntz & Rumohr (1986) in the western Baltic Sea. However, the benchmark assesses intolerance to hypoxia for one week whilst evidence of significantly reduced viability or death are reported after much longer periods. Therefore intolerance at the benchmark level has been assessed to be low. However, as the evidence suggests, prolonged exposure to oxygen concentrations below 2 mg O2 /l may severely impact upon species growth and survival and intolerance would be reported to be higher.

    Biological Pressures

     IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
    Intermediate No information High Decline Low
    More than 20 viruses have been described for marine bivalves (Sinderman, 1990). Bacterial diseases are more significant in the larval stages and protozoans are the most common cause of epizootic outbreaks that may result in mass mortalities of bivalve populations. Parasitic worms, trematodes, cestodes and nematodes can reduce growth and fecundity within bivalves and may in some instances cause death (Dame, 1996). Therefore mortality of some of the bivalves that characterize the biotope is likely following the introduction of pathogens or parasites and intolerance has been assessed to be intermediate. Recovery of the population is probable
    No information Not relevant No information Not relevant Not relevant
    No particular non-native species was identified as posing a current threat to this biotope.
    Intermediate High Low Decline Low
    The brown shrimp, Crangon crangon, one of the species indicative of sensitivity, is the target of a commercial fishery. Aside from the effects on the shrimp, however, the otter and/or beam trawls used to capture Crangon crangon tend to disrupt the habitat and dislodge inhabitants from the substratum.

    Bergman & van Santbrink (2000) suggested that the megafauna including Echinocardium cordatum and Abra alba were amongst the species most vulnerable to direct mortality due to bottom trawling in sandy sediments. Bivalves such as Ensis spp.,
    Corbula gibba and Chamelea gallina together with starfish were relatively resistant (Bergman & van Santbrink, 2000). Bradshaw et al. (2000) suggested that fragile species such a urchins (e.g. Spatangus purpureus and Echinus esculentus), the brittlestar Ophiocomina nigra, starfish Anseropoda placenta and the edible crab Cancer pagurus suffered badly from impact with a passing scallop dredge. More robust bodied or thick shells species were less sensitive. Overall, species with brittle, hard tests are regarded to be sensitive to impact with scallop dredges (Kaiser & Spencer, 1995; Bradshaw et al., 2000). However, the small size of Macoma balthica and Abra alba relative to the gear and meshes of commercial trawls may ensure survival of at least a moderate proportion of disturbed individuals which pass through.

    Abra alba and Macoma balthica demonstrate an 'r' type life-cycle strategy and are able to rapidly exploit any new or disturbed substratum available for colonization through larval recruitment, secondary settlement of post-metamorphosis juveniles or re-distribution of adults. Bonsdorff (1984) studied the recovery of a Macoma balthica population in a shallow, brackish bay in SW Finland following removal of the substratum by dredging in the summer of 1976. Recolonization of the dredged area by Macoma balthica began immediately after the disturbance to the sediment and by November 1976 the Macoma balthica population had recovered to 51 individuals/m². One year later, there was no detectable difference in the Macoma balthica population between the recently dredged area and a reference area elsewhere in the bay. In 1976, 2 generations could be detected in the newly established population indicating that active immigration of adults was occurring in parallel to larval settlement. In 1977, up to 6 generations were identified, giving further evidence of active immigration to the dredged area. Abra alba recovered to former densities following loss of a population from Keil Bay owing to deoxygenation within 1.5 years (Arntz & Rumohr, 1986).

    Effects on other infauna would depend upon the depth penetration of the gear, relative to the distribution of animals in the sediments but significant trawl-induced mortality has been reported for Echinocardium cordatum (De Groot & Apeldoorn 1971; Rauck, 1988). Furthermore, Lagis koreni is incapable of reconstructing its delicate sand-tube once removed from it (Schafer, 1972), and hence mortality following physical disturbance would be expected to be high for this species in particular. Therefore, an overall biotope intolerance of intermediate has been recorded. Recoverability has been assessed to be high (see additional information below).

    Not relevant Not relevant Not relevant Not relevant Not relevant

    Additional information

    Recoverability
    The life history characteristics of the species which characterize the biotope suggest that the biotope would recover from major perturbations within 5 years. For instance, Abra alba and Macoma balthica demonstrate an 'r' type life-cycle strategy and are able to rapidly exploit any new or disturbed substratum available for colonization through larval recruitment, secondary settlement of post-metamorphosis juveniles or re-distribution of adults. Bonsdorff (1984) studied the recovery of a Macoma balthica population in a shallow, brackish bay in SW Finland following removal of the substratum by dredging in the summer of 1976. Recolonization of the dredged area by Macoma balthica began immediately after the disturbance to the sediment and by November 1976 the Macoma balthica population had recovered to 51 individuals/m². One year later there was no detectable difference in the Macoma balthica population between the recently dredged area and a reference area elsewhere in the bay. In 1976, 2 generations could be detected in the newly established population indicating that active immigration of adults was occurring in parallel to larval settlement. In 1977, up to 6 generations were identified, giving further evidence of active immigration to the dredged area. Abra alba recovered to former densities following loss of a population from Keil Bay owing to deoxygenation within 1.5 years as did Lagis koreni, taking only one year (Arntz & Rumohr, 1986). Such evidence suggests that recoverability of the key functional and important characterizing species of the IMS.MacAbr biotope would be typically be high. However, the recovery of Echinocardium cordatum may take longer owing to recruitment that is frequently unsuccessful (Rees & Dare, 1993).

    Importance review

    Policy/Legislation

    - no data -

    Exploitation

    The brown shrimp Crangon crangon which may be present in the IMS.MacAbr biotope, is a commercially targeted species and is caught using various designs of beam and otter trawls.

    Additional information

    Subtidal mud / sandflats are important in supporting predator communities such as mobile macrofauna, demersal fishes and sea birds (Elliott et al., 1998)

    Bibliography

    1. Aberkali, H.B. & Trueman, E.R., 1985. Effects of environmental stress on marine bivalve molluscs. Advances in Marine Biology, 22, 101-198.
    2. Ambrose, W.G. Jr., 1993. Effects of predation and disturbance by ophiuroids on soft-bottom community structure in Oslofjord: results of a mesocosm study. Marine Ecology Progress Series, 97, 225-236.
    3. Arntz, W.E. & Rumohr, H., 1986. Fluctuations of benthic macrofauna during succession and in an established community. Meeresforschung, 31, 97-114.
    4. Barnes, R.S.K. & Hughes, R.N., 1992. An introduction to marine ecology. Oxford: Blackwell Scientific Publications.
    5. Beaumont, A.R., Newman, P.B., Mills, D.K., Waldock, M.J., Miller, D. & Waite, M.E., 1989. Sandy-substrate microcosm studies on tributyl tin (TBT) toxicity to marine organisms. Scientia Marina, 53, 737-743.
    6. Bergman, M.J.N. & van Santbrink, J.W., 2000. Fishing mortality of populations of megafauna in sandy sediments. In The effects of fishing on non-target species and habitats (ed. M.J. Kaiser & S.J de Groot), 49-68. Oxford: Blackwell Science.
    7. Beukema, J.J. & de Vlas, J., 1979. Population parameters of the lugworm, Arenicola marina, living on tidal flats in the Dutch Wadden Sea. Netherlands Journal of Sea Research, 13, 331-353.
    8. Boisson, F., Hartl, M.G.J., Fowler, S.W. & Amiard-triquet, C., 1998. Influence of chronic exposure to silver and mercury in the field on the bioaccumulation potential of the bivalve Macoma balthica. Marine Environmental Research, 45, 325-340.
    9. Bonsdorff, E., 1984. Establishment, growth and dynamics of a Macoma balthica (L.) population. Limnologica (Berlin), 15, 403-405.
    10. Bonsdorff, E., Norrko, A. & Boström, C., 1995. Recruitment and population maintenance of the bivalve Macoma balthica (L.) - factors affecting settling success and early survival on shallow sandy bottoms. In Proceedings of the 28th European Marine Biology Symposium. Biology and ecology of shallow coastal waters (ed. A. Eleftheriou, A.D. Ansell and C.J. Smith). Olsen and Olsen.
    11. Bradshaw, C., Veale, L.O., Hill, A.S. & Brand, A.R., 2000. The effects of scallop dredging on gravelly seabed communities. In: Effects of fishing on non-target species and habitats (ed. M.J. Kaiser & de S.J. Groot), pp. 83-104. Oxford: Blackwell Science.
    12. Brafield, A.E. & Newell, G.E., 1961. The behaviour of Macoma balthica (L.). Journal of the Marine Biological Association of the United Kingdom, 41, 81-87.
    13. Brousseau, D.J., 1978b. Population dynamics of the soft-shell clam Mya arenaria. Marine Biology, 50, 67-71.
    14. Bryan, G.W. & Gibbs, P.E., 1991. Impact of low concentrations of tributyltin (TBT) on marine organisms: a review. In: Metal ecotoxicology: concepts and applications (ed. M.C. Newman & A.W. McIntosh), pp. 323-361. Boston: Lewis Publishers Inc.
    15. Bryan, G.W., 1984. Pollution due to heavy metals and their compounds. In Marine Ecology: A Comprehensive, Integrated Treatise on Life in the Oceans and Coastal Waters, vol. 5. Ocean Management, part 3, (ed. O. Kinne), pp.1289-1431. New York: John Wiley & Sons.
    16. Buchanan, J.B., 1966. The biology of Echinocardium cordatum (Echinodermata: Spatangoidea) from different habitats. Journal of the Marine Biological Association of the United Kingdom, 46, 97-114.
    17. Bull, K.R., Every, W.J., Freestone, P., Hall, J.R. & Osborn, D., 1983. Alkyl lead pollution and bird mortalities on the Mersey Estuary, UK. Environmental Pollution (A), 31, 239-259.
    18. Cabioch, L. & Glaçon, R., 1975. Distribution des peuplements benthiques en Manche orientale, de la baie de Some au Pas-de-Calais. Compte Rendu Hebdomadaire des Seances de l'Academie des Sciences. Paris, 280, 491-494.
    19. Caddy, J.F., 1967. Maturation of gametes and spawning in Macoma balthica (L.). Canadian Journal of Zoology, 45, 955-965.
    20. Connor, D.W., Dalkin, M.J., Hill, T.O., Holt, R.H.F. & Sanderson, W.G., 1997a. Marine biotope classification for Britain and Ireland. Vol. 2. Sublittoral biotopes. Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06., Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06.
    21. Crisp, D.J. (ed.), 1964. The effects of the severe winter of 1962-63 on marine life in Britain. Journal of Animal Ecology, 33, 165-210.
    22. Crompton, T.R., 1997. Toxicants in the aqueous ecosystem. New York: John Wiley & Sons.
    23. Dauvin, J-C. & Gentil, F., 1989. Long-term changes in populations of subtidal bivalves (Abra alba and Abra prismatica) from the Bay of Morlaix (Western English Channel). Marine Biology, 103, 63-73.
    24. Davies, C.E. & Moss, D., 1998. European Union Nature Information System (EUNIS) Habitat Classification. Report to European Topic Centre on Nature Conservation from the Institute of Terrestrial Ecology, Monks Wood, Cambridgeshire. [Final draft with further revisions to marine habitats.], Brussels: European Environment Agency.
    25. de Groot, S.J. & Apeldoorn, J., 1971. Some experiments on the influence of the beam trawl on the bottom fauna. International Council for the Exploration of the Sea (CM Papers and Reports) CM 1971/B:2, 5 pp. (mimeo).
    26. Dewarumez, J-M., Davoult, D., Anorve, L.E.S. & Frontier, S., 1992. is the 'muddy heterogenous sediment assemblage' an ecotone between the pebbles community and the Abra alba community in the Southern Bight of the north Sea? Netherlands Journal of Sea Research, 30, 229-238.
    27. Dries, R.R. & Theede, H., 1974. Sauerstoffmangelresistenz mariner Bodenvertebraten aus der West-lichen Ostsee. Marine Biology, 25, 327-233.
    28. Duineveld, G.C.A. & Jenness, M.I., 1984. Differences in growth rates of the sea urchin Echinocardium cordatum as estimated by the parameters of the von Bertalanffy equation applied to skeletal rings. Marine Ecology Progress Series, 19, 64-72.
    29. Elliot, M., Nedwell, S., Jones, N.V., Read, S.J., Cutts, N.D. & Hemingway, K.L., 1998. Intertidal sand and mudflats & subtidal mobile sandbanks (Vol. II). An overview of dynamic and sensitivity for conservation management of marine SACs. Prepared by the Scottish Association for Marine Science for the UK Marine SACs Project.
    30. Emerson, C.W. & Grant, J., 1991. The control of soft-shell clam (Mya arenaria) recruitment on intertidal sandflats by bedload sediment transport. Limnology and Oceanography, 36, 1288-1300.
    31. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

    32. Franzen, N.C.M., 1995. Shear wave detection by Macoma balthica.
    33. Gilbert, M.A., 1978. Aspects of the reproductive cycle in Macoma balthica (Bivalvia). The Nautilus, 29, 21-24.
    34. Gosselin, L.A. & Qian, P., 1997. Juvenile mortality in benthic marine invertebrates. Marine Ecology Progress Series, 146, 265-282.
    35. Guenther, C.P., 1991. Settlement of Macoma balthica on an intertidal sandflat in the Wadden Sea. Marine Ecology Progress Series, 76, 73-79.
    36. Hall, S.J., 1994. Physical disturbance and marine benthic communities: life in unconsolidated sediments. Oceanography and Marine Biology: an Annual Review, 32, 179-239.
    37. Harvey, M. & Vincent, B., 1989. Spatial and temporal variations of the reproduction cycle and energy allocation of the bivalve Macoma balthica (L.) on a tidal flat. Journal of Experimental Marine Biology and Ecology, 129, 199-217.
    38. Hylland, K., Sköld, M., Gunnarsson, J.S. & Skei, J., 1996. Interactions between eutrophication and contaminants. IV. Effects on sediment-dwelling organisms. Marine Pollution Bulletin, 33, 90-99.
    39. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid,
    40. Jones, N.S., 1950. Marine bottom communities. Biological Reviews, 25, 283-313.
    41. Jorgensen, B.B., 1980. Seasonal oxygen depletion in the bottom waters of a Danish fjord and its effect on the benthic community. Oikos, 32, 68-76.
    42. Kaiser, M.J. & Spencer, B.E., 1995. Survival of by-catch from a beam trawl. Marine Ecology Progress Series, 126, 31-38.
    43. Lin, J. & Hines, A.H., 1994. Effects of suspended food availability on the feeding mode and burial depth of the Baltic clam, Macoma balthica. Oikos, 69, 28-36.
    44. Lopez, G.R. & Levinton, J.S., 1987. Ecology of deposit-feeding animals in marine sediments. Quarterly Review of Biology, 62, 235-260.
    45. Luoma, S.N., Cain, D.J., Ho, K. & Hutchinson, A., 1983. Variable tolerance to copper in two species from San Francisco Bay. Marine Environmental Research, 10, 209-222.
    46. Møhlenberg, F. and Kiørboe, T. 1983. Burrowing and Avoidance Behaviour in Marine Organisms Exposed to Pesticide Contaminated Sediments. Marine Pollution Bulletin,14, 57 - 60.

    47. Mackie, A.S.Y., Oliver, P.G. & Rees, E.I.S., 1995. Benthic biodiversity in the southern Irish Sea. Studies in Marine Biodiversity and Systematics from the National Museum of Wales. BIOMOR Reports, no. 1.
    48. Mattila, J., 'Olafsson E.B. & Johansson A., 1990. Predation effects of Crangon on benthic infauna on shallow sandy bottoms - an experimental study from southern Sweden. In Trophic relationships in the marine environment. Proceedings of the 24th European Marine Biological Symposium, (ed. M. Barnes & R.N. Gibson), pp 503-516. Aberdeen: Aberdeen University Press.
    49. McGreer, E.R., 1979. Sublethal effects of heavy metal contaminated sediments on the bivalve Macoma balthica(L.). Marine Pollution Bulletin, 10, 259-262.
    50. Nichols, F.H., 1977. Dynamics and production of Pectinaria koreni (Malmgren) in Kiel Bay, West Germany. In Biology of benthic organisms, (eds. B.F. Keegan, P. O'Ceidigh & P.J.S. Boaden), pp. 453-463.
    51. Nicolaidou, A., 1983. Life history and productivity of Pectinaria koreni Malmgren (Polychaeta). Estuarine, Coastal and Shelf Science, 17, 31-43.
    52. Nicolaidou, A., 1988. Notes on the behaviour of Pectinaria koreni. Journal of the Marine Biological Association of the United Kingdom, 68, 55-59.
    53. Nott, P.L., 1980. Reproduction in Abra alba (Wood) and Abra tenuis (Montagu) (Tellinacea: Scrobiculariidae) Journal of the Marine Biological Association of the United Kingdom, 60, 465-479.
    54. Oertzen, J.A. Von., 1969. Erste Ergebrisse zur experimentellen ökologie von postglazialen Relikten (Bivalvia) der Ostsee. Limnologica (Berlin), 7, 129-137.
    55. Pearson, T.H. & Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology: an Annual Review, 16, 229-311.
    56. Petersen, C.G.J., 1918. The sea bottom and its production of fish food. A survey of the work done in connection with valuation of the Denmark waters from 1883-1917. Report of the Danish Biological Station, 25, 1-62.
    57. Ratcliffe, P.J., Jones, N.V. & Walters, N.J., 1981. The survival of Macoma balthica (L.) in mobile sediments. In Feeding and survival strategies of estuarine organisms (ed. N.V. Jones and W.J. Wolff), pp. 91-108. Plenum Press.
    58. Rauck, G., 1988. What influence have bottom trawls on the seafloor and bottom fauna? Informationen fur die Fischwirtschaft, Hamberg, 35, 104-106.
    59. Rees, E.I.S., Nicholaidou, A. & Laskaridou, P., 1977. The effects of storms on the dynamics of shallow water benthic associations. In Proceedings of the 11th European Symposium on Marine Biology, Galway, Ireland, October 5-11, 1976. Biology of Benthic Organisms, (ed. B.F. Keegan, P.O Ceidigh & P.J.S. Boaden), pp. 465-474.
    60. Rees, H.L. & Dare, P.J., 1993. Sources of mortality and associated life-cycle traits of selected benthic species: a review. MAFF Fisheries Research Data Report, no. 33., Lowestoft: MAFF Directorate of Fisheries Research.
    61. Rhoads, D.C. & Young, D.K., 1970. The influence of deposit-feeding organisms on sediment stability and community trophic structure. Journal of Marine Research, 28, 150-178.
    62. Rosenberg, R. & Loo, L., 1988. Marine eutrophication induced oxygen deficiency: effects on soft bottom fauna, western Sweden. Ophelia, 29, 213-225.
    63. Salzwedel, H., 1979. Reproduction, growth, mortality and variations in abundance and biomass of Tellina fabula (Bivalvia) in the German Bight in 1975/1976. Veroffentlichungen des Instituts fur Meeresforschung in Bremerhaven, 18, 111-202.
    64. Smith, J.E. (ed.), 1968. 'Torrey Canyon'. Pollution and marine life. Cambridge: Cambridge University Press.
    65. Sörlin, T., 1988. Floating behaviour in the tellinid bivalve Macoma balthica (L.). Oecologia, 77, 273-277.
    66. Stickle, W.B. & Diehl, W.J., 1987. Effects of salinity on echinoderms. In Echinoderm Studies, Vol. 2 (ed. M. Jangoux & J.M. Lawrence), pp. 235-285. A.A. Balkema: Rotterdam.

    67. Strasser, M., 1999. Mya arenaria - an ancient invader of the North Sea coast. Helgoländer Meeresuntersuchungen, 52, 309-324.
    68. Stronkhorst, J., Hattum van, B. & Bowmer, T., 1999. Bioaccumulation and toxicity of tributyltin to a burrowing heart urchin and an amphipod in spiked, silty marine sediments. Environmental Toxicology and Chemistry, 18, 2343-2351.
    69. Tait, R.V. & Dipper, R.A., 1998. Elements of Marine Ecology. Reed Elsevier.
    70. Thorson, G., 1957. Bottom communities (sublittoral or shallow shelf). Memoirs of the Geological Society of America, 67, 461-534.
    71. Thrush, S.F., 1986. Community structure on the floor of a sea-lough: are large epibenthic predators important? Journal of Experimental Marine Biology and Ecology, 104, 171-183.
    72. Warwick, R.M. & Uncles, R.J., 1980. Distribution of benthic macrofauna associations in the Bristol Channel in relation to tidal stress. Marine Biology Progress Series, 3, 97-103.
    73. Weigelt, M. & Rumohr, H., 1986. Effects of wide range oxygen depletion on benthic fauna and demersal fish in Kiel Bay. Meeresforschung, 31, 124-136.
    74. Widdows, J., Brinsley, M.D., Salkeld, P.N. & Elliott, M., 1998. Use of annular flumes to determine the influence of current velocity and bivalves on material flux at the sediment-water interface. Estuaries, 21, 552-559.
    75. Wilson, W.H., 1991. Competition and predation in marine soft sediment communities. Annual Review of Ecology and Systematics, 21, 221-241.
    76. Wolff, W.J., 1968. The Echinodermata of the estuarine region of the rivers Rhine, Meuse and Scheldt, with a list of species occurring in the coastal waters of the Netherlands. The Netherlands Journal of Sea Research, 4, 59-85.
    77. Ziegelmeier, E., 1978. Macrobenthos investigations in the eastern part of the German Bight from 1950 to 1974. Rapports et Proces-verbaux des Reunions. Commission Internationale pour l'Exploration Scientifique de la Mer Mediterranee. Paris, 172, 432-444.

    Citation

    This review can be cited as:

    Budd, G.C. 2007. Nephtys hombergii and Macoma balthica in infralittoral sandy mud. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/habitat/detail/173

    Last Updated: 04/09/2007