Mya Arenaria Research Articles

A health status survey of clams, Mya arenaria and Ensis siliqua, in the Irish Sea

The soft shell clam, Mya arenaria, and the razor clam, Ensis siliqua, are widely distributed in Irish waters. Though the reproductive biology and other aspects of the physiology of these species has been previously investigated, little or no data are currently available on their health status. As this knowledge is essential for correct management of a species, M. arenaria and E. siliqua were examined to assess their current health status using histological and molecular methods, over a period of sixteen months. No pathogens or disease were observed in M. arenaria, and low incidences of Prokaryote inclusions, trematode parasites, Nematopsis spp. and eosinophilic bodies were recorded in razor clams for the first time in Northern European waters.

Finding of the pea crab Pinnaxodes mutuensis Sakai, 1939 (Crustacea: Decapoda: Pinnotheridae) in an unusual host in Busse Lagoon, southern Sakhalin

The symbiotic crab Pinnaxodes mutuensis Sakai, 1939 was found in the mantle cavity of the mud-burrowing bivalve Mya arenaria Linnaeus, 1758 (the family Myidae) in Busse Lagoon at southern Sakhalin Island. Along the Russian coasts, this species has been previously found in the mantle cavity of epifaunal bivalves of the family Mytilidae [Modiolus difficilis (Deshayes in Maillard, 1863), Modiolus modiolus (Linnaeus, 1758), Mytilus edulis Linnaeus, 1758, Crenomytilus grayanus (Dunker, 1853)] and the family Ostreidae [Crassostrea gigas (Thunberg, 1793)]. New data on the morphology and ecology of this crab are presented.

Interactions between the invasive European green crab, Carcinus maenas (L.), and juveniles of the soft-shell clam, Mya arenaria L., in eastern Maine, USA

Invasive species pose a threat to biodiversity in numerous marine ecosystems, and may have severe economic effects on commercially important species. The European green crab, Carcinus maenas, is one of the most common invaders of marine ecosystems globally. Since its invasion into eastern Maine, USA, during the early 1950's, populations of the soft-shell clam, Mya arenaria, have declined greatly. This has triggered the establishment of shellfish hatcheries and the development of aquaculture techniques to enhance the wild fishery. This study investigated interactions between C. maenas and cultured juveniles of M. arenaria both in the field and laboratory. In the field (Holmes Bay, Cutler, Maine), clam (initial mean shell length [SL] ±95% CI: 15.8±0.5mm; n=30) survival was: 1) 7× higher in predator deterrent treatments compared to open controls; 2) not improved by using rigid vs. flexible netting; and, 3) not improved by raising and supporting deterrent netting 5cm above the sediment surface. Wild clam recruitment was 4x greater in protected vs. open experimental units. In laboratory trials using similar sized juvenile clams, green crabs consumed clams protected by predator deterrent netting, and in one case did so without leaving visible signs of chipping, crushing, or disarticulating the valves. Physical evidence, other than crushing, may be used to differentiate between clam death due to predation vs. suffocation, disease, or other sources of mortality.

Phenology of abundance of bivalve spat and of their epibenthic predators: limited evidence for mismatches after cold winters

Annual recruitment of bivalves in the Wadden Sea is usually more successful in summers after cold than after mild winters. The new generation (0-group) of the main predators (shrimps and shore crabs) of early benthic stages of bivalves appear later in spring on tidal flats after colder winters. If these predators were more retarded by low water temperatures than their prey, the bivalve post-larvae would profit from a head start, enabling them to outgrow most predators and generate a strong new year-class. To test this hypothesis, we present a data series on bivalve post-larval density and 0-group shrimp and shore crab biomass in April to July of 10 to 30 yr in a tidal flat of the western Wadden Sea. With lower preceding winter water temperature, post-larvae of the bivalves Macoma balthica, Cerastoderma edule, and Mya arenaria and members of 0-group shrimp Crangon crangon and shore crab Carcinus maenas arrived later in spring, but only crabs responded much stronger to water temperatures than their prey did. Among the bivalves, post-larvae of M. balthica were the first to arrive and C. edule the last. Among the 0-group predators, shrimps arrived in April/May and shore crabs in June/July. Shrimp were present simultaneously with tiny just-settled bivalve post-larvae after cold and mild winters, whereas juvenile crabs were usually too late to seriously affect the abundance of the earliest bivalve prey. For most of spring, predation by crabs was limited to prey consumption by older crabs. Late-summer recruit numbers could be predicted within 1 or 2 mo after the start of their settlement, indicating that critical interactions occurred when they were very small. We conclude that there is limited evidence for possible mismatches in timing of interactions between just-settled bivalve post-larvae and their epibenthic predators as an explanation for the generally higher recruitment success in bivalves after severe winters.

Variability in predator abundance links winter temperatures and bivalve recruitment: correlative evidence from long-term data in a tidal flat

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 513:1-15 (2014) - DOI: https://doi.org/10.3354/meps10978 FEATURE ARTICLE Variability in predator abundance links winter temperatures and bivalve recruitment: correlative evidence from long-term data in a tidal flat J. J. Beukema*, R. Dekker** Royal Netherlands Institute for Sea Research, PO Box 59, 1790AB Den Burg, Texel, The Netherlands *Corresponding author: jan.beukema@nioz.nl**Raw data available upon request to rob.dekker@nioz.nl ABSTRACT: In the Wadden Sea, annual recruitment in the major bivalve species is mostly successful in summers following severe winters, whereas it usually fails after mild winters. On the basis of a 40 yr data series, we corroborated this relationship between winter temperatures and subsequent summer abundance of recruits in 3 bivalves: Macoma balthica, Cerastoderma edule, and Mytilus edulis. A 30 yr data series showed that annual abundance of their main epibenthic predators (0-group shrimp Crangon crangon and 0- and 1-group shore crabs Carcinus maenas) was higher in springs after mild winters compared to cold ones. Summer recruit numbers in 4 bivalve species (the above and Mya arenaria) were higher when predator biomass had been lower in the preceding spring. We argue that the latter relationship was probably of a causal nature and might explain not only the relationship between winter temperatures and bivalve recruitment success, but also the observed synchronies of annual recruitment success between bivalve species and between distant parts of the Wadden Sea. Shrimp abundance in May showed a significantly increasing long-term trend that might partly explain the declining trends in recruitment success, biomass, and annual production observed in the western Wadden Sea in M. balthica and M. edulis. We conclude that top-down effects by predation on early bottom stages of bivalves strongly affect biomass and production of some of the most important members of the benthic community of the Wadden Sea, keeping this system well below its carrying capacity for bivalves in nearly all years. KEY WORDS: Crangon crangon · Carcinus maenas · Temperature rise · Tidal flats · Wadden Sea · Macoma balthica · Cerastoderma edule · Mytilus edulis · Mya arenaria Full text in pdf format Information about this Feature Article NextCite this article as: Beukema JJ, Dekker R (2014) Variability in predator abundance links winter temperatures and bivalve recruitment: correlative evidence from long-term data in a tidal flat. Mar Ecol Prog Ser 513:1-15. https://doi.org/10.3354/meps10978 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 513. Online publication date: October 22, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Activation of transcription and retrotransposition of a novel retroelement, Steamer, in neoplastic hemocytes of the mollusk Mya arenaria.

Bivalve mollusks of the North Atlantic, most prominently the soft shell clam Mya arenaria, are afflicted with an epidemic transmissible disease of the circulatory system closely resembling leukemia. The disease is characterized by a dramatic expansion of blast-like cells in the hemolymph with high mitotic index. Examination of hemolymph of diseased clams revealed high levels of reverse transcriptase activity, the hallmark of retroviruses and retroelements. By deep sequencing of RNAs from hemolymph, we identified transcripts of a novel retroelement, here named Steamer. The DNA of the element is marked by long terminal repeats and encodes a single large protein with similarity to mammalian retroviral Gag-Pol proteins. Steamer mRNA levels were specifically elevated in diseased hemocytes, and high expression was correlated with disease status. DNA copy number per genome was present at enormously high levels in diseased hemocytes, indicative of extensive reverse transcription and retrotransposition. Steamer activation in M. arenaria is an example of a catastrophic induction of genetic instability that may initiate or advance the course of leukemia.

Predation of Sea Scallops and Other Indigenous Bivalves by Invasive Green Crab,Carcinus maenas, from Newfoundland, Canada

ABSTRACT Populations of green crab (Carcinus maenas) have expanded within Newfoundland, and this has raised concern from fish harvesters and scientists regarding bivalve predation in coastal areas on species such as juvenile sea scallops (Placopecten magellanicus). We used 2 microcosm experiments to determine (1) the effects of water temperature (5°C and 12°C) on scallop predation; (2) scallop size selection in small and large green crabs and a large indigenous predator, the rock crab (Cancer irroratus); and (3) bivalve prey selection in large green crabs between softshell clams (Mya arenaria), blue mussels (Mytilus edulis), and sea scallops. Overall, green and rock crabs captured 4 times more scallops in warm water (12°C) than cold (5°C). Large green (60–70 mm) and rock (75–90 mm) crabs captured similar numbers of scallops, selected medium-size (30–40 mm) scallops, and avoided small (10–20 mm) scallops. Small green crabs (40–50 mm) captured only small scallops. Large green crabs selected softshell clams ...

Comparative study of ecophysiological and biochemical variation between the Baltic and North Sea populations of the invasive soft shell clam Mya arenaria (L. 1758)

Abstract Seasonal variations of environmental factors, such as temperature and salinity, require metabolic acclimatization in sedentary benthic fauna distributed over a wide geographical range. The soft-shell clam Mya arenaria inhabits the coastal waters of the North Atlantic including North America and Europe. In Europe, M. arenaria populations are distributed from Iceland to the Mediterranean Sea, including the North Sea, the Baltic Sea and the Black Sea. Seasonal changes in physiological parameters (gonad index, condition index, biochemical composition and respiration rate) of M. arenaria from the Baltic Sea (the Gulf of Gdańsk, Poland), and the North Sea (Versee Meer, the Netherlands) were studied. The sex ratio of both populations did not differ from 1:1 and the seasonal gonad index was higher in the Baltic population. The average condition index changed seasonally at both studied sites, and was also higher in the Baltic population (except the autumn) compared to the North Sea. In both studied populations, the content of proteins, lipids and carbohydrates in the soft tissue followed the seasonal variations, and it was higher in the Baltic population. The respiration rate was lower in the Baltic population, and seasonal changes in the respiration rate seem to be correlated with changes in the water temperature. Based on the results obtained in the present study, we suggest that Mya arenaria is characterized by a large phenotypic plasticity and differences in the observed physiological traits are due to acclimatization to ambient environmental conditions.

Reproductive phenology of coastal marine bivalves in a seasonal environment

Environmental conditions during the larval phase (food concentration and temperature) impact recruitment success of marine bivalves by affecting growth and survival. We analysed the seasonal match between environmental conditions and larval presence of six coastal bivalve species over eight consecutive years (2006–2013) in the western Wadden Sea, taking species-specific physiological responses to these conditions into account. The larval occurrence of four species overlapped with their optimum in environmental conditions as calculated following the Dynamic Energy Budget theory: the occurrence of larvae of Cerastoderma edule, Mya arenaria and Mytilus edulis matched with their optimum food conditions, while larvae of Crassostrea gigas were mainly found during the temperature optimum of this species. Larvae of Ensis directus and Macoma balthica, however, only occurred months after their most favourable food conditions. The first group probably uses the energy immediately after uptake for the production and release of gametes (‘income breeders’), whereas the second group accumulates and stores energy reserves for later reproduction (‘capital breeders’). Larvae of C. gigas and M. balthica were observed much earlier in the year than expected from previous occurrences and from formerly know threshold temperatures for spawning. These apparent changes in timing of spawning suggest that Pacific oysters and Baltic tellins have recently acclimated to new environmental conditions.

A genetic technique to identify the diet of cownose rays, Rhinoptera bonasus: analysis of shellfish prey items from North Carolina and Virginia

Cownose rays are implicated in the consumption of commercially important shellfish on the U.S. East Coast. We tested this assumption by developing a molecular technique for species identification from cownose ray gut contents. Digestive tracts sampled from 33 rays in Pamlico Sound, NC and Chesapeake Bay, VA contained pieces of partially-digested tissue, well-digested tissue, fluid, and minute shell fragments which made visual identification to the species level nearly impossible. We sequenced the cytochrome oxidase subunit I (COI) for seven locally acquired bivalve species, chosen for their commercial and ecological importance in NC and VA. Sequences were used to design species-specific primers for each bivalve species to amplify polymerase chain reaction (PCR) products. We designed primers such that PCR products were sufficiently different in size to be distinguishable from one another when resolved on an agarose gel, and multiplexing of several species in one reaction was possible. Digestive tract sample testing revealed that cownose rays in Chesapeake Bay ate stout tagelus and soft shell clams. There was no evidence of the rays in the study consuming commercially important oysters, hard clams, and bay scallops. Further sampling over an extended period of time and additional locations is required to confirm these results. Our diagnostic tests could easily be expanded to elucidate the impact of cownose ray predation on prey populations.

Mechanisms used by the inhabitants of a sand flat in the White Sea to colonize aggregates of Mytilus edulis Linnaeus, 1758 (Bivalvia: Mytilidae)

The colonization of artificially created aggregates of the mussel Mytilus edulis by organisms that inhabit an intertidal sand and mud flat was studied in a field experiment. The sediment of 40 experimental plots was cleared of macrofauna. Thirty of these plots were covered with fishing nets, on which either live mussels (ten plots, type M) or mussel dummies (ten plots, type D) were placed; on ten plots, the nets were left empty (type Z). The remaining ten plots without nets but with a cleared surface (type E) were the control. For comparison, samples were taken from the ambient intact community. After 16 days of exposure, the community on the plots differed from the ambient one. In the E-Z-D-M series, only 7 out of 29 taxa that were found in the samples differed significantly in abundance. Chironomid larvae, adults, and spat of M. edulis and Mya arenaria were most abundant on the plots with a hard substrate (Z, D, M). Adult Jaera sp., Oligochaeta, Littorina saxatilis, and Nemertea were more abundant on the type M plots. The abundance of spat of Macoma balthica and Hydrobia ulvae did not differ significantly. The results indicate that the biological activity of mussels M. edulis in dense assemblages facilitated immigration of adult animals of other species. The M. edulis aggregates either had no influence on the spat of mollusks or they attracted it as a hard substrate for settlement.

Disseminated neoplasia in the soft-shell clam Mya arenaria: membrane lipid composition and functional parameters of circulating cells.

In a previous study we compared lipid composition and functional parameters of circulating cells from Cerastoderma edule affected or not by disseminated neoplasia (neoplastic cells vs hemocytes) (Le Grand et al. Chem Phys Lipids 167:9-20 2013). Neoplastic cells presented morpho-functional modifications concomitant to striking membrane lipid alterations: the proportion of particular plasmalogen molecular species was drastically decreased. We wanted to test whether this pattern was representative of bivalve neoplastic cells. For the purpose, a similar study was conducted on another bivalve species affected by disseminated neoplasia, the soft-shell clam (Mya arenaria). Although total reactive oxygen species production was unaffected, M. arenaria neoplastic cells presented some functional alterations: phagocytosis activity was reduced by 33%. However, lipid compositions were not drastically altered. Particularly, sterol and plasmalogen levels did not differ between both cell types (about 43% of membrane lipids and 35% of phospholipids, respectively in hemocytes and neoplastic cells). This could be related to the fact that disseminated neoplasia was not related to hemolymph cell proliferation in M. arenaria (0.9±0.2 10(6)cellmL(-1), considering both healthy and neoplastic clams, n=6). Nevertheless this study highlighted minor but specific alterations of membrane lipid composition in M. arenaria neoplastic cells. The only phospholipid subclass in which the fatty acid profile strongly differed between both cell types was serine plasmalogen (PlsSer), with neoplastic cells presenting lower specific enrichment of 20:1n-11 in PlsSer. Such specific alteration of membrane lipid composition strengthened the assumption of an implication of key plasmalogen molecular species in this leukemia-like disease in bivalves.

Benthic non-indigenous species among indigenous species and their habitat preferences in Puck Bay (southern Baltic Sea)

To date 11 non-indigenous benthic taxa have been reported in Puck Bay (southern Baltic Sea). Five of the 34 taxa forming the soft bottom communities are regarded as non-indigenous to this area. They are Marenzelleria spp., Mya arenaria, Potamopyrgus antipodarum, Gammarus tigrinus and Amphibalanus improvisus. Non-indigenous species comprised up to 33% of the total number of identified macrofaunal taxa (mean 17%). The average proportion of aliens was 6% (max 46%) in the total abundance of macrofauna, and 10% (max 65%) in the biomass. A significant positive relationship was found between the numbers of native and non-indigenous taxa. The number of native taxa was significantly higher on a sea bed covered with vascular plants than on an unvegetated one, but no such relationship was found for their abundance. No significant differences were found in the number and abundance of non-indigenous species between sea beds devoid of vegetation and those covered with vascular plants, Chara spp. or mats of filamentous algae. G. tigrinus preferred a sea bed with vegetation, whereas Marenzelleria spp. decidedly preferred one without vegetation.

Influence of substratum on non-native clam recruitment in Willapa Bay, Washington, USA

Two non-native clam species (Manila clams, Ruditapes philippinarum, and Eastern soft-shell clams, Mya arenaria) vary in density throughout intertidal habitats in Willapa Bay, Washington, USA. We used these species to test a fundamental ecological question, long addressed in marine systems, of whether the observed patterns were due to settlement choice or post-settlement mortality. A series of four experiments revealed habitat-specific mortality of young clams to be the dominant driver of distributions for both species. In contrast, settlement, which occurred over an extended reproductive period (June–Sept), appeared insensitive to substrate modification through additions of rock or shell (Expt 1–3). In Expt 2 and 3, sampled after winter when clams had reached ~1cm shell length, densities were lower in soft sediments characterizing much of the bay, and higher with rock or shell addition, especially with mesh bag protection. In Expt 4, which involved a crossed design of vegetation removal and substrate addition, one-year-old R. philippinarum densities increased with substrate addition more often than M. arenaria, and neither changed in response to removal of vegetation alone. In the case of one substratum, round rock, both vegetation removal and substrate addition were required to raise clam densities. Netting and gravel addition are standard practices in clam aquaculture to protect plantings of larger clams (e.g. >1cm), but in our study substrate modification reduced losses of smaller (<1mm) newly-settled clams. Overall, top-down control appears to be more important than settlement choice in determining local densities of Willapa Bay's non-native clams. Our findings open the possibility of improved aquaculture yields across all substrate types via natural settlement combined with interventions to reduce early losses due to predation.

Benthic non-indigenous species among indigenous species and their habitat preferences in Puck Bay (southern Baltic Sea)

Abstract To date 11 non-indigenous benthic taxa have been reported in Puck Bay (southern Baltic Sea). Five of the 34 taxa forming the soft bottom communities are regarded as non-indigenous to this area. They are Marenzelleria spp., Mya arenaria , Potamopyrgus antipodarum , Gammarus tigrinus and Amphibalanus improvisus . Non-indigenous species comprised up to 33% of the total number of identified macrofaunal taxa (mean 17%). The average proportion of aliens was 6% (max 46%) in the total abundance of macrofauna, and 10% (max 65%) in the biomass. A significant positive relationship was found between the numbers of native and non-indigenous taxa. The number of native taxa was significantly higher on a sea bed covered with vascular plants than on an unvegetated one, but no such relationship was found for their abundance. No significant differences were found in the number and abundance of non-indigenous species between sea beds devoid of vegetation and those covered with vascular plants, Chara spp. or mats of filamentous algae. G. tigrinus preferred a sea bed with vegetation, whereas Marenzelleria spp. decidedly preferred one without vegetation.

Effect of emersion on soft-shell clam,Mya arenariaand the mussel,Mytilus edulisseeds in relation to development of vitality indices

Blue mussels (Mytilus edulis ) and soft-shell clams (Mya arenaria ) are both aquaculture species in east coast of Canada and US shellfish farmers take advantage of the byssal threads production of mussels for suspension culture and the burrowing behaviour of soft-shell clams for enhancement practices. It is important that these animals attach and burrow efficiently to minimize losses during rearing. The aim of this work was to study two potential vitality indices on mussels (23.6 ± 0.1 mm) and clams (22.6 ± 0.1 mm) seeds following various periods of emersion: attachment strength of Mytilus edulis and burrowing ability of Mya arenaria. The effect of emersion on energy content (proteins, lipids, glycogen) was also examined. We observed no significant decrease in the attachment strength of mussels after air exposure for 78 h or in the burrowing efficiency of soft-shell clams after 54 h. Air exposure had no effect on different lipid classes, proteins, or glycogen content in either mussel or clam tissues. The stressful emersion event induced in our study may not have been high enough to induce detectable behavioural responses. This can be explained by the bivalves’ ability to adapt their metabolism to minimize activity during air exposure. In doing so, they do not consume their energy reserves, which are then still available when specimens are reimmersed. Thus mussels are able to efficiently produce byssal threads and clams to burrow into sediments as soon as they are back in the water.

Detecting hot-spots of bivalve biomass in the south-western Baltic Sea

Bivalves are among the most important taxonomic groups in marine benthic communities in nutrient cycling via benthic–pelagic coupling and as food source for higher trophic levels. Additionally, bivalve species combine several autecological features with potential value for assessment and management purposes. Therefore, the demand for quantitative distribution maps of bivalves is high both in research with focus on functional ecology of marine benthos and in policy.In our study, we modelled and mapped the distribution of biomass of soft- and hard-bottom bivalves in the south-western Baltic Sea using Random Forest algorithms. Models were achieved for ten of the most frequent of overall 29 identified species. The distribution of bivalve biomass was mainly influenced by the abiotic parameters salinity, water depths, sediment characteristics and the amount of detritus as a proxy for food availability. Three hot-spots of bivalve biomass dominated by different species were detected: the oxygen-rich deeper parts of the Kiel Bay dominated by Arctica islandica, the shallow areas close to the mouth of the river Oder dominated by Mya arenaria and the hard-substrates around Rügen Island and the shallow Adlergrund dominated by Mytilus spp. The attained maps provide a good basis for further functional and applied analysis.

Soft Shell Clams (Mya arenaria) Contribute to Macroalgal Blooms in a Partially-restored Gulf of Maine Back-barrier Lagoon

Rachel K. Thiet⇑ corresponding author, Department of Environmental Studies, Antioch University New England, Keene, NH, USA 03431, rthiet{at}antioch.edu.

Molluscan Community Recovery in a New England Back‐Barrier Salt Marsh Lagoon 10 Years after Partial Restoration

AbstractLike many Eastern U.S. salt marshes, East Harbor salt marsh lagoon on Cape Cod was isolated from tidal flow in the 1800s, resulting in near‐freshwater conditions and loss of native salt marsh species. After its partial restoration in 2002, a variety of marine and estuarine fauna recolonized East Harbor, and soft shell clam (Mya arenaria) recolonization was particularly prolific. The goal of our study was to evaluate molluscan community composition, density, and distribution at regular intervals for 10 years following restoration, and to relate molluscan community recovery to various physical properties at the site. In 2007, 2008, and 2011, we sampled mollusks at several points across East Harbor, and we also recorded water salinity and temperature, particle size distribution, and submerged aquatic vegetation density. In 2007 and 2008, we encountered 12 and 11 mollusk species, respectively; M. arenaria was the most abundant species in 2007 and the second most abundant species in 2008. In 2011, we encountered eight mollusk species and M. arenaria was the most abundant species. Mollusk species richness declined from 12 to 8 species between 2008 and 2011. Our results show that mollusk species richness and density have declined significantly since the first few years following restoration; related studies attribute this to high summer water temperatures in the Main Lagoon and severe macroalgal blooms during 2005–2006. This suggests that East Harbor is still equilibrating to baseline conditions and that full tidal restoration may be necessary to sustain a diverse mollusk community at East Harbor.

Influence of sediment acidification and water flow on sediment acceptance and dispersal of juvenile soft-shell clams (Mya arenaria L.)

Although ocean acidification is expected to reduce carbonate saturation and yield negative impacts on open-ocean calcifying organisms in the near future, acidification in coastal ecosystems may already be affecting these organisms. Few studies have addressed the effects of sedimentary saturation state on benthic invertebrates. Here, we investigate whether sedimentary aragonite saturation (Ωaragonite) and proton concentration ([H+]) affect burrowing and dispersal rates of juvenile soft-shell clams (Mya arenaria) in a laboratory flume experiment. Two size classes of juvenile clams (0.5–1.5mm and 1.51–2.5mm) were subjected to a range of sediment Ωaragonite and [H+] conditions within the range of typical estuarine sediments (Ωaragonite 0.21–1.87; pH6.8–7.8; [H+] 1.58×10−8–1.51×10-7) by the addition of varying amounts of CO2, while overlying water pH was kept constant ~7.8 (Ωaragonite ~1.97). There was a significant positive relationship between the percent of juvenile clams burrowed in still water and Ωaragonite and a significant negative relationship between burrowing and [H+]. Clams were subsequently exposed to one of two different flow conditions (flume; 11cms−1 and 23cms−1) and there was a significant negative relationship between Ωaragonite and dispersal, regardless of clam size class and flow speed. No apparent relationship was evident between dispersal and [H+]. The results of this study suggest that sediment acidification may play an important role in soft-shell clam recruitment and dispersal. When assessing the impacts of open-ocean and coastal acidification on infaunal organisms, future studies should address the effects of sediment acidification to adequately understand how calcifying organisms may be affected by shifting pH conditions.