Mussel Clumps Research Articles

Habitat engineering by the invasive zebra mussel Dreissena polymorpha (Pallas) in a boreal coastal lagoon: impact on biodiversity

Habitat engineering role of the invasive zebra mussel Dreissena polymorpha (Pallas) was studied in the Curonian lagoon, a shallow water body in the SE Baltic. Impacts of live zebra mussel clumps and its shell deposits on benthic biodiversity were differentiated and referred to unmodified (bare) sediments. Zebra mussel bed was distinguished from other habitat types by higher benthic invertebrate biomass, abundance, and species richness. The impact of live mussels on biodiversity was more pronounced than the effect of shell deposits. The structure of macrofaunal community in the habitats with >103 g/m2 of shell deposits devoid of live mussels was similar to that found within the zebra mussel bed. There was a continuous shift in species composition and abundance along the gradient ‘bare sediments—shell deposits—zebra mussel bed’. The engineering impact of zebra mussel on the benthic community became apparent both in individual patches and landscape-level analyses.

Coral-inhabiting swimming crabs (Crustacea, Decapoda, Portunidae) of the Sudanese Red Sea

Brachyuran crabs show high species richness and constitute one of the most diverse biotic groups in coral reef communities. The present study examines the taxonomy and ecology (occurrence in particular coral habitats) of swimming crabs from the Sanganeb Atoll (Sudan) known for its high diversity of hermatypic corals. During two expeditions in the years 1991 and 1992, eleven species were collected directly from coral colonies or in baited traps in coral habitats: Carupa tenuipes Dana, 1852; Caphyra fulva Stephenson & Campbell, 1960; Portunus aff. iranjae Crosnier, 1962; Gonioinfradens paucidentata (A. Milne-Edwards, 1861); Thalamitoides quadridens A. Milne-Edwards, 1869; Thalamitoides spinigera Nobili, 1905; Thalamita cf. iranica Stephensen, 1945; Thalamita murinae Zarenkov, 1971; Thalamita prymna (Herbst, 1803); Thalamita quadrilobata Miers, 1884; and Thalamita savignyi A. Milne-Edwards, 1861. Thalamita murinae, had been recorded only once before and incompletely described; it is redescribed from the holotype. Together with Thalamita longifrons (A. Milne-Edwards, 1869) from the Pacific, it forms a distinct group of species living in complex coral habitats. This Th. longifrons group is revised; Th. spinimera Stephenson & Rees, 1967 and Th. yoronensis Sakai, 1969 are considered as new junior synonyms of Th. longifrons. The distribution of swimming crabs across the range of sampled habitats showed a characteristic pattern that did not simply reflect the sampling effort. Thalamitoides spinigera, a species endemic to the Red Sea and the Gulf of Aden, clearly preferred dead Stylophora habitats. Several hypotheses explaining preferences of particular species for Stylophora colonies are discussed. Inhabiting various coral habitats (which for many species can be substituted by rock, rubble or mussel clumps) is characteristic for the subfamilies Carupinae and Thalamitinae, whereas Portuninae are found there occasionally only.

Small-scale variation within a Modiolus modiolus (Mollusca: Bivalvia) reef in the Irish Sea. II. Epifauna recorded by divers and cameras

The spatial heterogeneity of epifauna on a Modiolus modiolus reef off north-west Wales was investigated using divers. The community associated with these horse mussels was similar to that described previously from Loch Creran and the north basin of Strangford Lough. Some differences in epifauna may be attributable to the less sheltered nature of the site. Modiolus modiolus numbers and the associated epifaunal community were significantly different between ridge and trough sub-habitats. Troughs can be considered ‘reduced’ ridge communities whereas ridges have high densities of horse mussels and certain sessile taxa were correlated with their abundance. Modiolus modiolus aggregation as a competitive response to the feeding environment, enhanced food availability on ridges and sediment deposition amongst mussel clumps may start to explain the undulating bed-form. Patchiness in community composition and periodic cover by ophuroids has implications when considering the monitoring of the horse mussel community. Stratified, in situ recording of the highly populated ridges could improve the statistical sensitivity of monitoring horse mussel reefs whilst simultaneously focusing on the more sensitive indicators of fishing threats.

Investigation of the effects of current velocity on mussel feeding and mussel bed stability using an annular flume

An annular flume was used to measure the effect of increasing current velocity on mussel (Mytilus edulis) feeding rate and the stability of mussel beds sampled from the mouth of the Exe estuary (SW England). It was found that, in contrast to earlier flume studies, the feeding rates of mussels from open coast sites were unaffected by current velocities up to 0.8 m s–1. Algal cell depletion in the water column above mussels was a function of current velocity, increasing with declining currents below 0.05 m s–1. The erodability/stability of the mussel bed, measured in terms of critical erosion velocity, sediment mass eroded and mean erosion rate, was found to be a function of the nature of the substrate and the density of the mussels. Erosion of mussel beds on sandy substrate showed a non-linear relationship with mussel bed density. In comparison with the sand (0% mussel cover), sediment resuspension was about five and four times higher for 25% and 50% cover, respectively. This was due to the increased turbulence and scouring around the clumps of mussels in low-density parts of the bed, and this resulted in some mussels detaching from the bed. At ~100% mussel cover, the sandy bed was more protected by the dense surface layer of mussels, and none became detached during erosion due to the high number of byssal attachments between individuals. The sediment resuspension from the 100% mussel cover was about three times lower than the 0% cover. Erosion of the bed with 50% cover resulted in burial of a large proportion of the mussels, with a 6 cm increase in sediment level. However, the mussels returned to the surface and recovered in 1–2 days, due to a combination of migration upwards and substrate settlement. Channels on the edge of the main Exmouth mussel bed were characterised by a more stable substrate comprising pebbles and sand with varying mussel densities. At these sites, where mussels experience high current velocities on spring tides (up to 0.9 m s–1), there was no difference between the erodability of pebble/sand substrate with 0% and 100% mussel cover. The sediment erosion was also lower than the 100% mussel cover on the sandy substrate, particularly at currents >0.4 m s–1. Sampling of different parts of the mussel bed at Exmouth showed mussels at low densities were made up of smaller clumps with a lower mass ratio of mussels to attached substrate (pebbles/sand), thus providing a greater degree of anchorage.

The Marine Mites Hyadesia sp. and Copidognathus sp. Associated with the Mussel Mytilus galloprovincialis

Two species of marine mites belonging to the families Hyadesiidae and Halacaridae, Hyadesia sp. and Copidognathus sp., respectively, were found associated with the mussel Mytilus galloprovincialis from Baja California in NW México. The first species was found inside the mussel gut with an intensity ranging from one to six mites per mussel and their prevalence was from 20.0 to 46.7%; this species was also found living free in the sediment at a density of 0.7 mite/100 ml. The second species was found on the mantle and gills of the host with an intensity ranging from one to three mites per host and their prevalence was from 3.3 to 6.7%; this species was abundant (4.5 mites/100 ml) and living free in the sediment around mussel clumps. Hyadesia sp. was found alive and attached in the gut of the mussel. A histological analysis revealed this species in the lumen of intestine surrounded by mucus and attached to the epithelial cells of the intestine, where some disorder of epithelial cells was associated. Moreover, this mite may be encapsulated by hemocytes inside the digestive diverticulum, the reproductive follicle, or the connective tissue surrounding the diverticulum. No damages to branches or gills resulting from the presence of Copidognathus sp. were observed. The results suggest that these mites are occasional invaders of mussels; however, as a result of this infestation, Hyadesia sp. may produce damage in the host's tissues. This is the first record of marine mites inside the gut, reproductive follicles, branches, and mantle of a marine bivalve.

Effects of sewage effluent on the population structure of Brachidontes rostratus (Mytilidae) on a temperate intertidal rocky shore

A single polluted site at Boags Rocks, south-eastern Australia, and four control sites were used to evaluate the effect of secondary-treated sewage effluent on the population structure, recruitment, growth and mortality of the mussel Brachidontes rostratus. B. rostratus recruited in greater numbers to mussel clumps at the outfall site than at control sites, regardless of the origin of the mussel clumps. The effects of pollution on the soft tissue mass and shell growth of juveniles depended on the origin of the mussels; shell growth of mussels local to Boags Rocks was smaller than the average shell growth recorded in mussels at the control sites, and individuals transplanted into Boags Rocks had higher soft tissue mass than those at the control sites. Mortality was greater at the polluted site than the control sites, regardless of mussel origin. Changes in the population structure of B. rostratus as a result of the discharge of sewage effluent have implications for intertidal fauna that use the habitat created within mussel clumps.

Mussels and mussel beds ( Mytilus edulis ) as stabilizers of sedimentary environments in the intertidal zone

Abstract Coastal zone protection of the intertidal zone is of great importance in view of the threats of sea level rise around the globe. Environmentally-friendly methods involving biological control may offer a solution. This paper studies mussels ( Mytilus edulis ) as stabilizers of the intertidal zone because they form beds that armour some intertidal sediments, hence reducing erosion. In field experiments we seeded high energy lower intertidal and low energy upper intertidal environments with isolated mussels and preformed clumps of mussels. More animals were lost from the higher energy site. Those that remained were transported landward for significant distances. Clumping protected animal loss at the low energy but not at the high energy site. Gravel placed under mussels improved their stability because mussels attached threads to them. Laboratory experiments show that mussels form clumps by attaching to other mussels, and when available to gravel which has to be at the sediment surface. Flume studies show single mussels decrease the critical erosion velocity of sediment near them. Similar effects are seen in the field at the edge of small mussel beds.

Relationships between the bivalves Mytilus edulis L. and Cerastoderma edule (L.) in a soft bottom environment: an example of interaction at small spatial scale

On the Neuharlingersieler Nacken tidal flat in the east Frisian Wadden Sea, Mytilus edulis spat settle and develop on Cerastoderma edule shells, thereby establishing mussel clumps or proper beds. Frequency of occurrence of individual C. edule bound in M. edulis clumps represented 0–22% of total conspecifics and was particularly high at the low shore distribution limit of C. edule. Postulated small scale interactions between M. edulis and C. edule were investigated in experimental cages in the field. Shell growth of C. edule was slower in the presence of M. edulis. In contrast, effects on survival were not detected during the 6 months experimental period. Slower cockle growth may be explained by a combination of mechanisms involving both exploitative competition for food, interference competition via byssal attachment and smothering by biodeposits.

Vertical Changes in Density, Size Structure and Shell Shape of the Bivalve Lasaea Undulata Within Intertidal Mussel Beds

Vertical changes in density, size structure and shell shape of Lasaea undulata (Bivalvia: Galeommatoidea) inhabiting intertidal mussel beds were studied at Wakayama Prefecture, Japan. At the study site, where two mytilids Septifer virgatus and Hormomya mutabilis formed vertically contiguous mussel beds, Lasaea density decreased downshore within the S. virgatus bed of the upper and mid zones. Few individuals were found within the H. mutabilis bed of the lower zone. Multiple linear regression analysis revealed that shore height was the only factor which showed a significant, positive correlation with density. Size structure differed between the upper and lower parts of the S. virgatus bed, suggesting that reproductive periods or growth rates of L. undulata differed with shore height. Prodissoconch length and shell shape were also different among shore heights. Number, size and shell shape of juveniles brooded within parents indicated that this species releases its young as non-planktotrophic, crawl-away juveniles. There was no significant difference in density of recruits between artificial mussel clumps of S. virgatus and H. mutabilis within enclosure cages, and no specific association was detected between L. undulata and either of the two mussel species.

Factors delimiting the boundary between vertically contiguous mussel beds of Septifer virgatus (Wiegmann) and Hormomya mutabilis (Gould)

AbstractOn moderately wave‐exposed rocky shores in middle Japan, the upper interidal mytilid, Septifer virgatus, and lower intertidal mytilid, Hormomya mutabilis, occur together, forming vertically contiguous mussed beds. Factors limiting the lower distribution limit of Septifer and the upper limit of Hormomya were investigated by collections of natural mussel clumps and single‐ and mixed‐species transplantation experiments. Newly settled juvenile Septifer (<5 mm shell length) were significantly fewer in the natural and artificial Hormomya clumps than in the Septifer clumps. Both natural and artificial Hormomya clumps accumulated a much greater amount of sediment than did the Septifer clumps. Hormomya clumps inhibited the recruitment of Septifer, presumably through accumulation of sediment, which resulted in setting the lower limit of the Septifer zone. Survivorship of small (5–10 mm) and large (>15 mm)Hormomya was much lower in Hormomya clumps transplanted upwards into the Septifer zone than it was in Hormomya clumps in the Hormomya zone. In mixed‐species clumps in the Septifer zone, however, survivorship of small Hormomya was not significantly different from that in mixed‐species clumps in the Hormomya zone. Septifer had a positive effect on the survival of small Hormomya and increased the upper limit of Hormomya, presumably by providing shelter and thus protecting them from desiccation. The upper limit of Hormomya zone was thus considered to be set by desiccation exceeding the physiological tolerance of the species.

Storm effects on eelgrass ( Zostera marina L.) and blue mussel ( Mytilus edulis L.) beds

The effects of storms on stands of blue mussels Mytilus edulis L. and eelgrass Zostera marina L. at a shallow subtidal site in the Western Baltic were examined. In mixed Zostera/Mytilus stands, the experimental removal of the eelgrass canopy strongly increased the risk of mussel dislodgement during a moderate storm with a median return time of 6.5 months. In contrast, no protection of mussels by eelgrass was found during a series of three intense storms, each of which had a median return time of > 11.5 yr. Also, mussel presence had no effect on the persistence of eelgrass patches (assessed as shoot density) during the moderate storm. The eelgrass meadow had a strong impact on dispersal of mussel clumps under non-storm conditions (wind velocities < 10 m/s). A transplantation experiment with small M. edulis patches showed that drifting mussel aggregates had a tendency to come to rest within eelgrass meadows and may initiate new mussel beds. The results partly explain the preference of blue mussel M. edulis beds for eelgrass Z. marina habitats at shallow subtidal sites of the Western Baltic.

Comparison of mussel bed community between two intertidal mytilids Septifier virgatus and Hormomya mutabilis

Mussel bed community structure of two intertidal mytilids, Septifer virgatus (Wiegmann) and Hormomya mutabilis (Gould), whose beds were contiguous vertically on a rocky intertidal shore (Wakayama Prefecture, Japan), was compared between 1982 and 1983. In the upper S. virgatus bed, crustaceans and bivalves were dominant in terms of both number of individuals and biomass. There were three barnacle species representative of the epizoans, two isopods and one amphipod as mobile fauna, and two bivalves as infauna. The lower H. mutabilis bed supported virtually no epizoans or mobile fauna. Infaunal free-ranging polychaetes and sipunculids were dominant in terms of both number of individuals and biomass. The H. mutabilis bed contained a much greater amount of sediment than did the S. virgatus bed, and the interstices among individual H. mutabilis and among their byssal threads were filled with sediment. The biomass of six of nine species dominant in the S. virgatus bed was negatively correlated with the amount of sediment. Recruitment of these faunal assemblages into artificial mussel clumps was examined in mussel enclosure experiments, and a negative sediment effect in H. mutabilis clumps was detected for one isopod and one limpet species. Factors causing the differences between two mussel bed communities are discussed, focusing on the effects of sediment.

Recruitment of the brown mussel Perna perna onto natural substrata: a refutation of the primary/secondary settlement hypothesis

The pattern of recruitment of the brown mussel Perna perna on an exposed rocky shore on the southeast coast of South Africa between March 1991 and March 1992 is reported. The densities and population size structures of plantigrades associated with 2 natural substrata, filamentous algae and established mussel clumps, are contrasted. Mussels of c500 pm shell length were present throughout the study period, but peaked in abundance dunng the winter months (June to September). Although the density of these early plantigrades vaned with both samphng date and site, type of substratum had no effect. Late plantigrades, mussels of >0.5 to 3.5 mm shell length, reached peak abundance amidst mussel clumps in winter as opposed to spring/early summer on algal turf. Sampling date, site and type of substratum all influenced the dens~ty of late plantigrades. The size distributions of the recruits found in association with the 2 substrata dlffered s~gn~ficantly on 4 of the 11 sampling dates. The recruitment pattern of P perna does not, therefore, conform with the generally accepted primary/secondary settlement hypothesis. The observed pattern lndlcates direct settlement of larvae from the plankton onto adult beds in addition to temporary attachment on filamentous algae. The relatively low intensities of recruitment observed, compared with those of other mytilids, may explain such anomalous attributes of P. perna as its lack of competitive dominance and low resilience to disturbance.

Recruitment of shore crabsCarcinus maenas on tidal flats: Mussel clumps as an important refuge for juveniles

During the late summer and early fall, juvenile shore crabs (Carcinus maenas L.) occurred in high abundances in mussel clumps scattered on tidal flats of the Wadden Sea. Abundances were much lower on bare tidal flats without mussel clumps and decreased substantially from July to November, whereas numbers in mussel clumps remained high. Large crabs left the tidal flats in early fall, whereas juveniles undertook tidal migrations only in the late fall. In March very few shore crabs were found in the intertidal area. The size of juvenile shore crabs living between mussels did not increase significantly during fall. On the bare tidal flats surrounding the mussels, a size increase was observed. Mussel beds and mussel clumps serve as a spatial refuge for the early benthic phases of juvenile shore crabs. Between mussels they can hide effectively from their epibenthic predators. Juvenile shore crabs do not leave the intertidal area and the mussel habitats before their major predators have left the area. Mussel clumps scattered over the tidal flats may be a critical refuge for juvenile shore crabs settling on tidal flats. Intensified efforts in mussel culturing in the European Wadden Sea during recent decades may have caused an increased abundance of mussel clumps on tidal flats, thus enhancing habitat availability for some mussel-clump inhabitants.

Effects ofFucus vesiculosus covering intertidal mussel beds in the Wadden Sea

The brown algaFucus vesiculosus formamytili (Nienburg) Nienhuis covered about 70% of mussel bed (Mytilus edulis) surface area in the lower intertidal zone of Königshafen, a sheltered sandy bay near the island of Sylt in the North Sea. Mean biomass in dense patches was 584 g ash-free dry weight m−2 in summer. On experimental mussel beds, fucoid cover enhanced mud accumulation and decreased mussel density. The position of mussels underneath algal canopy was mainly endobenthic (87% of mussels with >1/3 of shell sunk into mud). In the absence of fucoids, mussels generated epibenthic garlands (81% of mussels with <1/3 of shell buried in mud). Mussel density underneath fucoid cover was 40 to 73% of mussel density without algae. On natural beds, barnacles (Balanidae), periwinkles (Littorina littorea) and crabs (particularly juveniles ofCarcinus maenas) were significantly less abundant in the presence of fucoids, presumably because most of the mussels were covered with sediment, whereas in the absence of fucoids, epibenthic mussel clumps provided substratum as well as interstitial hiding places. The endobenthic macrofauna showed little difference between covered and uncovered mussel beds. On the other hand, grazing herbivores — the flat periwinkleLittorina mariae, the isopodJaera albifrons and the amphipodsGammarus spp. — were more abundant at equivalent sites with fucoid cover. The patchy growth ofFucus vesiculosus on mussel beds in the intertidal Wadden Sea affects mussels and their epibionts negatively, but supports various herbivores and increases overall benthic diversity.

Temporal variation in species‐area curves for invertebrates in clumps of an intertidal mussel

We examined the temporal variation in the relationships between the number of invertebrate species, and of total individuals inhabiting clumps of the intertidal mussel Brachidontes rostratus and the area of the clumps We collected clumps in four seasons ‐ autumn, winter, spring and summer ‐ from a rocky shore in south‐eastern Australia Positive curvilinear relationships between species number and area were recorded for all seasons but fewer species for a given area were found in autumn and summer compared with winter and spring These species‐area relationships were different from those predicted from a passive sampling model (Random Placement Model) Positive relationships between number of individuals and area were also recorded but these did not vary between seasons There was no short‐term difference (i e between phases of tide and day) in species or individual number in clumps Seasonal variation, and small‐scale spatial unpredictability in recruitment patterns are potentially important determinants of species numbers in this system The seasonal differences we have recorded for mussel clumps suggest that future studies on island systems particularly in marine habitats should consider temporal variation in species‐area relationships and that conclusions from previous comparisons of species‐area curves based on one‐off sampling must only be tentative

Mud crab predation on ribbed mussels in salt marshes

Mud crab (Panopeus herbstii H. Milne Edwards) predation on Atlantic ribbed mussels (Geukensia demissa Dillwyn) was studied by a series of laboratory and field experiments at two sites at Morehead City, North Carolina, USA from 1987 to 1989. Tidal elevation had no effect on predation intensity, although mud crabs were active only when they were submerged. Horizontal distance from the water-marsh edge significantly affected mussel mortality in one of two winter experiments, despite the occurrence of virtually all the crabs at the marsh edge. Of the juvenile mussels attached to adult mussels, those totally buried in the sediment suffered mortality from mud crab predation at a rate not detectably different from those exposed above the surface. Juveniles attached to adult conspecifics, however, experienced significantly less mortality than those attached to oysters. Interestingly, the two groups of mussels (those attached to conspecifics and those attached to oysters) display shell morphological dimorphism. The more oblate shells of the mussels attached to oysters as compared to those attached to conspecifics might be induced by the higher predation rate. Alternatively, slimmer shells from individuals attached to conspecifics may be the result of living within physically compact mussel clumps.

Barnacle walls as mediators of intertidal mussel recruitment:effects of patch size on the utilization of space

Recruitment of the competitively dominant mussel Perumytilus purpuratus to the mid rocky intertidal zone in central Chile depends upon the presence of recruitment-mediators such as mussel clumps, filamentous algae or barnacle shells. The relationship between the lateral walls of adult barnacles and the recruitment of P. purpuratus was investigated in a semi-sheltered rocky habitat at Las Cruces, central Chile. Changes in number of individuals and percent cover of sessile species were recorded for 8 mo (January to September 1988) in different sized patches of bare rock. All patches were surrounded by barnacle beds. Throughout the study, P. purpuratus recruited only on the walls of adult barnacles that formed the patch borders, and never on bare rock. Conversely, barnacles recruited directly on the bare surface of cleared patches. Regressions of numbers of individuals in relation to patch area showed that mussel recruits outnumbered those of barnacles in patches smaller than 35.5 cm2. Above this critical patch area, the number of barnacle recruits was progressively larger than that of mussels. The area of barnacle walls suitable for mussel recruitment increases linearly with increasing patch perimeter, while the area suitable for barnacle recruitment is a function of patch area. The number of recruits was related to the substratum availability in different patch sizes, suggesting that recruitment of barnacles and mussels is not limited by larval abundance. The probability of mussels monopolizing the patches was higher in small than in large patches; the chance for barnacles to monopolize large patches increased with increasing size of patch. Consequently a barnacle-dominated substratum may change to a mussel-dominated one depending upon the relative abundances of small and large patches. A barnacle bed disrupted in several small patches will provide more substratum for mussel recruitment than if only few large patches are produced. Possible effects of patch and predator sizes on intertidal community structure are discussed.

Importance of location in the salt marsh and clump size on growth of ribbed mussels

Growth rates of suspension-feeding ribbed mussels were studied by putting out two sizes of identically constituted mussel clumps as well as single mussels at different locations in the salt marsh. Growth rates of mussels among singletons and two clump sizes were similar, suggesting that food concentration was not a limiting factor. At one of the two marshes studied, the magnitude of differences in growth rates of mussels from low to high tidal elevations is larger than would be predicted by the differences in time of submergence. At similar tidal elevations, mussels from the interior of the marsh grew at similar rates to those from the marsh edge. At the other marsh, however, individuals from the interior grew substantially faster than their counterparts from the edge at similar tidal elevations. I hypothesize that mussels from the interior of the marsh had an additional food source because Spartina detritus can contribute to food supplies in the interior.

Influence of location in a salt marsh on survivorship of ribbed mussels

To assess how predation on ribbed mussels Geukensia dernissa varied with tidal elevation and distance into the salt marsh, identical mussel clumps were introduced into locations differing in elevation and distance from open water in salt marshes at 2 geographically separate areas. Mussel mortality was greater at lower tidal elevations. At similar tidal elevations, mussels on the marsh interior showed less mortality than those on the marsh edge. Mortality was most likely due to predahon by blue crabs Callinectes sapidus. Blue crabs and other aquatic predators forage in the salt marsh only during periods of tidal inundation and thus their feeding time decreases from low to high levels. At similar tidal elevations, their access to the marsh intenor may be impeded by dense marsh grasses.