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Estuaries worldwide are grappling with deteriorating water quality and benthic conditions that coincide with the rising detection of pathogenic and potentially pathogenic microbes (PPM). Both indigenous PPM and those that enter estuaries through urban and agricultural runoff are funneled through suspension-feeding organisms and deposited onto the benthos, where they can be moved through food webs. This study explored PPM communities in the Indian River Lagoon system, a biodiverse but urbanized estuary in east central Florida (USA). PPM were surveyed in estuary water, at stormwater outfalls, and in biodeposits of a key suspension feeder, the eastern oyster Crassostrea virginica. A total of 52 microbial exact sequence variants, with per-sample relative abundances up to 61.4%, were identified as PPM. The biodeposits contained relatively more abundant and diverse PPM than the water samples. PPM community composition also differed between seasons and between biodeposits and water. The community differences were driven primarily by Vibrio and Pseudoalteromonas spp. This investigation provides evidence that, through biodeposition, oyster reefs in the IRL estuary are a reservoir for PPM, and it documents some taxa of concern that should be conclusively identified and investigated for their pathogenicity and potential to pervade food webs and fisheries. [ABSTRACT FROM AUTHOR]

This study provides a follow-up to prior measurements of the impact of mussel Mytilus galloprovincialis farming on benthic macrofauna and biogeochemistry and includes the first measurements of the effect of oyster Crassostrea gigas farming in Saldanha Bay, South Africa. The Shannon–Wiener index was significantly lower for farm than for control sites, indicating reduced diversity at farm sites. The lowest values of the Warwick statistic were recorded at the established farm site (R-old). Nested PERMANOVA showed no significant difference in community composition between farm and control sites. Suspension feeders (the mudprawn Upogebia capensis, clam Venerupis corrugata, and holothurian Thyone aurea) dominated at control sites and were important contributors to dissimilarity. Deposit feeders and predatory/scavenging gastropods tended to be more abundant at the farm sites. nMDS ordination showed a clear separation of the more exposed Big Bay stations. The proportions of mud and very coarse sand were moderately associated with community structure. Biogeochemical fluxes showed insignificant differences in sediment oxygen demand between the farm and control sites. Ammonium (NH4) regeneration dominated nitrogen (N) fluxes and was greater at the farm (313 µmol N m−2 h−1) than at the control (187 µmol N m−2 h−1) sites, and maximum rates were restricted to the established mussel raft (R-old) during winter. In contrast, fluxes of oxidised N were less at farm sites relative to the controls. There was no significant difference in phosphate (PO4) regeneration at farm and control stations, leading to higher inorganic N to PO4 regeneration ratios at farm sites. [ABSTRACT FROM AUTHOR]

By filtering large volumes of water and releasing nutrient-rich biodeposits (feces and pseudofeces), oysters can locally enhance sediment biogeochemical cycling. An active Crassostrea virginica restoration program in Mosquito Lagoon, FL (USA), was leveraged to assess the immediate (first-year) effects of restoration on sediment nutrients. Measurements included extractable and total carbon, nitrogen, and phosphorus on dead, natural, and restored reefs using a before-after-control-impact design. To investigate an observed "age-nutrient paradox" in sediment nutrient concentrations, a laboratory experiment compared feeding rates and biodeposit nutrient content between juvenile and older oysters. The field study documented a 136% increase in ammonium, 78% increase in total nitrogen, 46% increase in total phosphorus, and 75% increase in organic matter concentrations 12 months post-restoration, with extractable nutrients responding more rapidly to restoration than total nutrients. Sediment nutrient increases were positively correlated with oyster density, shell length, and reef height. Moreover, the laboratory study indicated juvenile oysters had higher rates of chlorophyll-a removal and ammonium efflux and produced biodeposits with higher concentrations of dissolved organic carbon, nitrate, and ammonium than older oysters. Overall, this study documented increases in sediment nutrients on intertidal reefs within the first year of restoration, which may be explained by a greater filtration rate and more nutrient-enriched biodeposits contributed by young oysters as compared to older oysters. Sediment total nitrogen and ammonium content may be the most robust monitoring metrics for documenting the ecosystem service of enhanced biogeochemical cycling on restored oyster reefs. [ABSTRACT FROM AUTHOR]

Freshwater bivalves can influence water quality by reducing phytoplankton levels through filter-feeding and altering nutrient levels through excretion and biodeposition. In northeast Australia, native freshwater bivalves (Corbicula australis) may help restore the water quality of coastal wetlands that receive high nutrient loads in runoff from nearby agricultural activity. We investigated the biofiltration and biodeposition capacity of C. australis and discuss their potential to provide an ecosystem service benefit of improved water quality to the Great Barrier Reef (GBR). The filtration and biodeposition rates of C. australis were measured in natural and artificial wetlands across: (1) the population’s size range; and (2) the temperature range of the wetlands they inhabit. High frequency water temperature loggers were deployed in wetlands throughout the year to determine water column temperature seasonality, population densities were measured to scale from individuals to ecosystem service provisioning potential. Bivalve filtration and biodeposition were quantified by measuring the rates of chlorophyll a removal and nutrient biodeposition, respectively. Biofiltration rates did not increase with size or differ between natural and artificial wetlands. In contrast, size was positively related to phosphorus (P) and nitrogen (N) biodepsoition rates, and N biodeposition rates differed between natural and artificial wetlands. Our results also suggest that biofiltration and biodeposition capacity of C. australis may be limited in high water temperatures only experienced in summer months. Overall, we demonstrate the importance of size, population density, and environmental context (i.e. wetland type and season) for the filtering capacity and biodeposition rate of C. australis. Larger individuals and denser populations mean that filtration and biodeposition rates are likely to be higher in artificial wetlands and may lead to greater processing of nutrient rich water. [ABSTRACT FROM AUTHOR]

Bivalves serve an important ecosystem function in delivering organic matter from pelagic to benthic zones and are important in mediating eutrophication. However, the fate of this organic matter (i.e., biodeposits) is an important consideration when assessing the ecological roles of these organisms in coastal ecosystems. In addition to environmental conditions, the processing of biodeposits is dependent on its composition and the metabolic capacity of the associated microbial community. The objectives of this study were to compare the biological reactivity, potential denitrification rates, and microbial communities of biodeposits sourced from different bivalve species: hard clam (Mercenaria mercenaria), eastern oyster (Crassostrea virginica), and ribbed mussel (Geukensia demissa). To our knowledge, this is the first study to investigate and compare the microbiome of bivalve biodeposits using high-throughput sequencing and provide important insight into the mechanisms by which bivalves may alter sediment microbial communities and benthic biogeochemical cycles. We show that clam biodeposits had significantly higher bioreactivity compared to mussel and oyster biodeposits, as reflected in higher dissolved inorganic carbon and ammonium production rates in controlled incubations. Potential denitrification rates were also significantly higher for clam biodeposits compared to oyster and mussel biodeposits. The microbial communities associated with the biodeposits were significantly different across bivalve species, with significantly greater abundances of Alteromonadales, Chitinophagales, Rhodobacterales, and Thiotrichales associated with the clam biodeposits. These bioreactivity and microbial differences across bivalve species are likely due to differences in bivalve physiology and feeding behavior and should be considered when evaluating the effects of bivalves on water quality and ecosystem function. [ABSTRACT FROM AUTHOR]

Purpose: Zebra mussels (Dreissena polymorpha) alter the transport dynamics and fate of particulate matter in aquatic systems by intercepting, retaining, and recycling suspended materials. This study examines the effect of particle processing by dressenids on the nature (grain size distribution, settling velocity, porosity  and density) and transport properties (critical shear stress for erosion, erosion rates, and bed stability) of suspended particulate matter in lakes.Materials and methods: The bed stability, erosion rate, and critical shear stress for erosion of dreissenid biodeposits were measured in an annular flume. The particle size distribution, settling rate, density, and porosity were measured to characterize the physical nature of the biodeposits. Materials studied in the flume include (1) a combination of biodeposits and surface sediments collected from dreissenid beds and (2) biodeposits harvested in a weir box populated with dreissenids.Results and discussion: The settling rates of both biodeposit/sediment mixtures and pure biodeposits were lower than natural sediment in lacustrine environments. Erosion characteristics and transport properties of biodeposits were strongly influenced by bed age and the presence of mussels. Bed stability increased after 7 days, with a τcrit of 0.26 Pa compared to the 2- and 14-day consolidation periods (τcrit = 0.13 and 0.15 Pa), respectively. The observed changes in bed stability with bed age will modify the transfer of particulate materials to the offshore profundal zone as well as the rates and magnitudes of sediment-associated nutrients in the near shore zone.Conclusions: Biostabilization of surficial lake-bottom sediments impacted by mussel biodeposits may increase bed stability and reduce the export of particulate matter to the offshore environment. Further, well-developed communities of dreissedid mussels have an armoring effect on deposited sediment, which reduces remobilization of sediment and biodeposits. However, once eroded, the dreissedid modified deposits will likely be transported further due to their low-settling velocity. [ABSTRACT FROM AUTHOR]

The pattern of elements accumulation in biodeposits formed by living organisms and extracellular products of their metabolism (biofouling, primary soils) on different bedrocks (of the monuments of Historical necropoleis in Saint Petersburg) were studied by a complex of biological and mineralogical methods (optical microscopy, SEM, EDX, XRD, ICP MS, XRFS). The content of 46 elements in biodeposits with various communities of microorganisms is determined. The model recreating the picture of the input and selective accumulation of elements in biodeposits on the stone surface in outdoor conditions is assumed. It is shown that the main contribution to the elemental composition of biodeposits is made by the environment and the composition of the microbial community. The contribution of leaching under the action of microbial metabolites of mineral grains, entering biodeposits from the environment, is significantly greater than that of the underlying rock.

Consumers contribute to nutrient cycling in aquatic ecosystems by nutrient retention in tissues, metabolic transformations and excretion, and promoting microbial processes that remove nutrients (i.e., nitrogen (N) loss via denitrification). Freshwater mussels (Unionidae) form dense assemblages in rivers, and affect nutrient transformations through feeding, biodeposition, and bioturbation. However, the effects of Unionid mussels on N and phosphorus (P) retention are not commonly measured. We quantified rates of filtration, retention, and biodeposition of carbon (C), N, and P for two Unionid species: Lasmigona complanata and Pyganodon grandis. We used continuous-flow cores with N tracers to measure denitrification in sediments alone and with a single individual of each species. We conducted measurements in an urban river near Chicago, IL, USA that is a target for Unionid restoration. Both Unionid species showed high rates of P-specific feeding and retention, but low N-specific rates. This was in agreement with high N:P ratio in the water column. Each species significantly increased denitrification relative to sediment alone. N tracers suggested direct denitrification of nitrate increased denitrification, although enhanced coupled nitrification-denitrification likely also contributed to denitrification. Finally, denitrification rates with and without mussels were used to estimate the value of N loss under different scenarios for mussel restoration at the river scale. Overall, restored Unionid populations may enhance P retention in soft tissues and shells and N loss via denitrification. Ecosystem managers may find greater support for restoration of Unionid populations with careful calculations of their ecosystem role in nutrient retention and removal. [ABSTRACT FROM AUTHOR]

Silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) are poised to invade the Laurentian Great Lakes. Zebra mussels (Dreissena polymorpha) and quagga mussels (D. rostriformis bugensis) have shifted nutrient pathways towards the benthos, partly through deposition of feces and rejected food particles called biodeposits. When biodeposit material was fed to bighead and silver carp, they fed on the material, but on average lost weight. Energy density between fed and unfed fish did not differ, but a few individual fish did gain weight on the biodeposits diet. Our results demonstrate that biodeposits might be considered a supplemental food for bigheaded carps. [ABSTRACT FROM AUTHOR]

The goal of this paper is to find out whether suspended mussel culture affects the vertical fluxes of biogenic particles in the Ría de Vigo on a seasonal scale. With this aim, vertical fluxes of particulate organic carbon (POC) and the magnitude and composition of vertical export of phytoplankton carbon (Cphyto) collected in sediment traps were examined by comparing data obtained inside a mussel farming area (RaS) with those found at a reference station (ReS) not affected by mussels. Our results indicate that mussel farming has a strong impact on sedimentation fluxes under the rafts, not only increasing POC flux but also altering the magnitude and composition of Cphyto fluxes. Average POC flux at RaS (2564 ± 1936 mg m day) was four times higher than at ReS (731 ± 276 mg m day), and much of this increase was due to biodeposit fluxes (Cbiodep) which accounted for large proportion of POC flux (35-60 %). Indeed, because of this high Cbiodep flux, only a small proportion of the POC flux was due to Cphyto flux (3-12 %). At the same time, we observed an increased sedimentation of phytoplankton cells at RaS that could be explained by a combination of mechanisms: less energetic hydrodynamic conditions under mussel rafts, ballast effect by sinking mussel feces, and diatom aggregates. Moreover, mussel farming also altered the quality of the Cphyto flux by removing part of the predatory pressure of zooplankton and thus matching diatom composition in water column and sediment traps. [ABSTRACT FROM AUTHOR]

The influence of oysters on nitrogen (N) cycling has received increased research attention. Previous work focused on fluxes of N solutes and gases, but the effects on microbes responsible for N transformations are unknown. In May 2010, we deployed eastern oysters ( Crassostrea virginica) in mesh cages above sand-filled boxes at four sites across a nutrient gradient in Jamaica Bay, New York City. In fall and winter, we used quantitative PCR to measure abundance of 16S rRNA and nitrite reductase genes for denitrification ( nirS and nirK) and dissimilatory nitrate reduction to ammonium ( nrfA) in sediment. We measured water column nutrients and chlorophyll a, sediment C:N and organic matter (OM), exchangeable ammonium (NH), ammonification, nitrification, and denitrification potential (DNP). Oysters did not affect gene abundance in fall, when we predicted that their influence would be strongest, or in winter. However, gene abundance was significantly different among sites and seasons. Factors which explained 16S rRNA, nirS, and nirK gene abundance included sediment OM, water column N, and chlorophyll a, similar to previous research. Abundance of nrfA was lower than that of nir genes and positively related to sediment C:N, suggesting OM lability may drive the balance between nir and nrfA. Finally, nirS and nirK abundance was unrelated to DNP, which is consistent with variable results from the literature. More studies that combine molecular techniques with N transformation rates in the context of oyster reefs are needed. Results will advance models which predict the ecosystem effects of reef conservation and restoration under variable environmental conditions. [ABSTRACT FROM AUTHOR]

Benthic deposition of carbon (C) and nitrogen (N)-rich oyster biodeposits may increase denitrification, or anaerobic respiration of nitrate (NO) to di-nitrogen gas (N). However, environmental drivers of C and N dynamics in oyster biodeposits and reef-adjacent sediments require clarification. In July 2012, we collected intact sediment cores adjacent to and 15-20 m away from two oyster reefs ( Crassostrea virginica) in Great Bay, New Hampshire, USA: one reference site and one site with cultural eutrophication. We also measured seston, chlorophyll a, and in situ oyster feeding and biodeposition. Cores were incubated in continuous-flow chambers where inflow water received N-ammonium (NH), NO, or no isotopes (control). We quantified fluxes of dissolved nutrients and gasses (oxygen, N, N, N, and argon) after 24 h. Finally, we measured size-fractionated sediment organic matter. At the eutrophic site, abundant phytoplankton in the 5-28 µm size range was correlated with enhanced oyster feeding rates and biodeposit quality (lower C:N). This site had greater denitrification rates in reef-adjacent cores relative to distal cores. Low production of N in NH amended cores suggested water column or biodeposit NH were unlikely to be converted to N. At both sites, reef-adjacent cores had more shell and higher N production with NO addition relative to distal cores, suggesting direct denitrification enhancement near reefs. Oysters likely increased sediment N production via high quality biodeposits (eutrophic site), and NO diffusion via structural complexity of reef-adjacent sediment (both sites). Overall, results suggest oyster-mediated ecosystems services may be expected to vary with environmental conditions. [ABSTRACT FROM AUTHOR]

Downward fluxes of organically rich biodeposits under suspended mussel lines can cause benthic impacts such as changes in benthic community structure or microbial mat production. Quantifying sediment erosion in these coastal ecosystems is important for understanding how fluxes of organic matter and mussel biodeposits contribute to benthic–pelagic coupling. Critical shear velocity (u* crit ), erosion rates and particle size distributions of resuspended sediment were measured at four stations distributed along a transect perpendicular to a mussel farm in Lagune de la Grande Entrée, Îles-de-la-Madeleine (Quebec, Canada). Stations were selected underneath the outer-most mussel line (0 m) and at distances of 15, 30 m and at a reference station (500 m) further along the transect. Shear velocity was measured using a calibrated portable Particle Erosion Simulator, also referred to as the BEAST (Benthic Environmental Assessment Sediment Tool). Undisturbed sediment cores obtained by divers were exposed to shear stress to compare differences between stations. Erosion sequences indicated no significant differences in u* crit between stations, but there were significant differences in erosion rates beneath mussel lines compared to other stations. Erosion rates were the highest in cores from beneath mussel lines, but paradoxically had the lowest u* crit . Mean erosion rates at u* crit varied between 25 and 47 g m − 2 min − 1 and critical erosion thresholds varied between 1.58 and 1.73 cm s − 1 , which compare with intensive mussel culture sites elsewhere in eastern Canada. Significant differences existed in biotic and abiotic properties of sediments which could explain variation in maximum erosion rates within and between stations. Particle sizes measured by videography of resuspended sediment at different shear velocities ranged from 0.2 to 3.0 mm. Quantifying sediment erosion from intact marine sediments helps to improve our mechanistic understanding of these processes, and the BEAST further contributes to predictive capability in benthic–pelagic coupling modeling. [ABSTRACT FROM AUTHOR]

The Australasian sea cucumber (Australostichopus mollis) has attracted commercial attention for aquaculture development, partly due to its potential for co-culture with shellfish and finfish species. However, minimal attention has been given to the possibility of co-culturing this species with oysters. In this study we evaluated the growth of juvenile sea cucumbers (36.7 ± 0.9 g, wet weight) caged underneath Pacific oyster farms in northern New Zealand. Co-culture started at the end of the summer, and after 304 days the juveniles had doubled in size (79.8 ± 3.3 g, wet weight), but their subsequent growth appeared to be constrained by overstocking of the cages and summer water temperatures, reaching a carrying capacity of 720 g m−2. Overall, the results of this study indicate that the co-culture of juvenile sea cucumbers with Pacific oysters is feasible, if sea cucumber losses are reduced (between 33% and 52% lost in this study) and careful attention is given to stocking rates and the water temperature regimes of oyster farms in order to maintain adequate growth rates. [ABSTRACT FROM AUTHOR]

Oyster reefs have declined globally. Interest in their restoration has motivated research into oyster-mediated ecosystem services including effects on biodiversity, filtration, and nitrogen (N) cycling. Recent evidence suggests oysters may promote denitrification, or anaerobic respiration of nitrate (NO3-) into di-nitrogen gas, via benthic deposition of carbon (C) and N-rich biodeposits. However, the mechanisms whereby biodeposits promote N transformations prerequisite to denitrification (e.g., mineralization and nitrification) are unclear. Previous research has also not measured oysters' influence on N cycling in urbanized areas. In May 2010 we deployed eastern oysters (Crassostrea virginica) in mesh cages above sand-filled boxes at four sites across a nutrient gradient in Jamaica Bay, New York City (New York, USA). Oysters were arranged at four densities: 0, 40, 85, and 150 oysters/m². For 17 months we measured water-column nutrients and chlorophyll a, every two weeks to monthly. Every two months we measured sediment ash-free dry mass (AFDM), exchangeable ammonium (NH4+), ammonification, nitrification, denitrification potential (DNP), and NO3- and C limitation of DNP. Oysters increased sediment AFDM at three of four sites, with the greatest increase at high density. Oysters did not affect any N pools or transformations. However, variation among sites and dates illustrated environmental drivers of C and N biogeochemistry in this urban estuary. Overall, nitrification was positively related to net ammonification, water column NH4+, and sediment NH4+, but was not correlated with DNP. Denitrification was consistently and strongly NO3- limited, while C was not limiting or secondarily limiting. Therefore, the oyster-mediated increase in AFDM did not affect DNP because C was not its primary driver. Also, because DNP was unrelated to nitrification, it is unlikely that biodeposit N was converted to NO3- for use as a denitrification substrate. Predicting times or sites where denitrification is driven by the C and N species originating from oyster biodeposits remains a challenge under eutrophic conditions. Towards this goal, we synthesized our conclusions with literature predictions in a conceptual model for pathways whereby oysters might influence C and N dynamics differently in oligotrophic relative to eutrophic ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: The interactions of mussel aquaculture with physico-chemical properties and the biogenic elemental composition of the surface sediment were studied at a long-line farm, located in a 12 km2 area, which included the farm (4 km2) characterized by relevant freshwater inputs along the North-Western Adriatic coastline. Negative redox potentials were detected at two stations directly affected by the farm. Total phosphorus content reached the highest concentration at stations located beneath the farm. OC/TP and TN/TP showed similar patterns, which was characterized by average values underneath the farm (respectively 45.5 and 4.5) that were significantly lower than those measured at the control stations. Our hypothesis, that these patterns could be related to organic matter enrichment of the surface sediment underneath the farm, due to intense mussel biodeposition, was confirmed by the mass accumulation rates, estimated to be respectively 23, 2.3, 0.94 and 0.26 g m−2 y-1 for organic carbon, total nitrogen, total and organic phosphorus. Data concerning the sediment chemistry were normalized with respect to the pelite fraction thus increasing the capability of detecting the environmental impact of the farm under variable background sedimentary fluxes. [Copyright &y& Elsevier]

Abstract: The feeding biology and ecology of juveniles of the Australasian sea cucumber, Australostichopus mollis are not well understood. A better understanding may provide useful information for the development of the aquaculture of this species. Currently, A. mollis is being co-cultured beneath mussel farms and it is not clear if it can effectively use the wide natural variation in the food availability typically found under mussel farms. In this study the feeding and growth of juvenile A. mollis, was examined on feeds containing different levels of mussel, Perna canaliculus, biodeposits, resulting in different levels of total organic matter (TOM) (1, 4, 12, and 20%) covering a range similar to that found beneath a typical mussel farm in New Zealand. As the TOM content increased in the food from 4% to 20%, the ingestion rate of sea cucumbers decreased and both the apparent assimilation and food conversion efficiencies increased. There was no significant growth of sea cucumbers in the 1% TOM feed treatment, while sea cucumbers in the remaining treatments had similar final wet weights with a combined mean daily specific growth rate of 0.6% d−1. These results demonstrate the ability of this species to use different levels of TOM to generate similar growth rates mainly by changes in their feeding behaviour and digestive physiology. These changes in their feeding biology together with the spatial and temporal variation of food availability in the sediments impacted by the mussel farm need to be taken into account when selecting suitable mussel farms for co-culture, as well as when defining the initial stocking biomass of sea cucumbers. [Copyright &y& Elsevier]

Abstract: Azaspiracids (AZAs) are a group of lipophilic polyether compounds first detected in Ireland which have been implicated in shellfish poisoning incidents around Europe. These toxins regularly effect shellfish mariculture operations including protracted closures of shellfish harvesting areas for human consumption. The armoured dinoflagellate Azadinium spinosum Elbrächter et Tillmann gen. et sp. nov. (Dinophyceae) has been described as the de novo azaspiracid toxin producer; nonetheless the link between this organism and AZA toxin accumulation in shellfish has not yet been established. In August 2009, shellfish samples of blue mussel (Mytilus edulis) from the Southwest of Ireland were analysed using liquid chromatography–tandem-mass spectrometry (LC–MS/MS) and were found to be above the regulatory limit (0.16μgg−1 AZA-equiv.) for AZAs. Water samples from this area were collected and one algal isolate was identified as A. spinosum and was shown to produce azaspiracid toxins. This is the first strain of A. spinosum isolated from Irish waters. The Irish A. spinosum is identical with the other two available A. spinosum strains from Scotland (3D9) and from Denmark (UTHE2) in its sequence of the D1–D2 regions of the LSU rDNA. A 24h feeding trial of blue mussels (M. edulis) using an algal suspension of the Irish A. spinosum culture at different cell densities demonstrated that A. spinosum is filtered, consumed and digested directly by mussels. Also, LC–MS/MS analysis had shown that AZAs were accumulating in the shellfish hepatopancreas. The toxins AZA1 and -2 were detected in the shellfish together with the AZA analogues AZA3, AZA6, AZA17 and -19 suggesting that AZA1 and -2 are metabolised in the shellfish within the first 24h after ingestion of the algae. The levels of AZA17 detected in the shellfish hepatopancreas (HP) were equivalent to the levels of AZA1 but in the remainder tissues the levels of AZA17 were four to five times higher than that of AZA1, only small quantities of AZA3 and -19 were present with negligible amounts of AZA6 detected after the 24h period. This could have implications in the future monitoring of these toxins given that at present according to EU legislation only AZA1–AZA3 is regulated for. This is the first report of blue mussels’ (M. edulis) feeding on the azaspiracid producing algae A. spinosum from Irish waters. [Copyright &y& Elsevier]

Abstract: An understanding of the feeding and digestive capabilities of juvenile sea cucumbers is an important step for their aquaculture development. The feeding behaviour, food selectivity, digestion and absorption of total organic matter (TOM) were determined for juveniles (35–40g wet weight) of the Australasian brown sea cucumber, Australostichopus mollis, kept in circular plastic tanks (9l; 6 replicate tanks per feed treatment). Sea cucumbers were fed with feeds containing different levels of TOM (1, 4, 12 and 20%) prepared from sand mixed with the biodeposits of aquacultured green-lipped mussel, Perna canaliculus. No significant diurnal patterns in digestion were detected in all feed treatments. As the TOM level in the feed increased, the selection of organic particles decreased and most importantly overall nutrient absorption increased, which is likely to lead to improved growth rates. However, absorption efficiency declined as organic matter content of the feed increased. This study suggests that palatable-artificial diets rich in organic matter can be used to increase nutrient uptake and potentially facilitate increased stocking densities of sea cucumbers under controlled conditions. [Copyright &y& Elsevier]

Abstract: Bivalve filter feeders that have been suspension-cultured intensively produce significant amounts of particulate biodeposits (feces and pseudofeces) and dissolved metabolic wastes (mainly ammonia and phosphate) that may negatively impact the aquaculture environment. In this study, monthly biodeposition rates, as well as ammonia and phosphate excretion rates, of three-age-cohort Japanese scallops (Patinopecten yessoensis) cultured in the Changhai sea area, Northern Yellow Sea of China were investigated in situ using a sediment trap and a closed respirator, respectively, to evaluate self-pollutant loading in this system. Results showed an age effect and obvious seasonality in these rates for P. yessoensis. The biodeposition rates for 1, 2, and 3-yr-old P. yessoensis ranged from 0.01–0.66, 0.09–1.28, and 0.18–2.25gdrymaterialind−1 d−1, respectively. Manifested lower values in the biodeposition rates occurred in summer and winter, while higher values appeared in spring and autumn, which were mainly attributable to the effects of water temperature and seston concentration. The Japanese scallops released considerable amounts of ammonia, ranging from 0.02–0.86, 0.05–1.69, and 0.05–3.96mgind−1 d−1 for 1, 2, and 3-yr-old specimens, respectively. Excretion rates for PO4–P ranged from 0.03–0.39, 0.09–1.18, and 0.18–2.65mgind−1 d−1 for 1, 2, and 3-yr-old scallops, respectively. An extrapolation of the results showed that annual biodeposit production could reach as high as 1.42×106 t dry matter, or 1.30×105 t POM, 3.48×104 t POC, and 4.83×10 3 t PON, with an annual NH4 +–N production of 1.50×103 t and PO4 3−–P production of 1.07×103 t by all current suspension-cultivated scallop populations in the Changhai sea area. Results of our study suggest that the potential impact of self-pollutants by filter-feeding bivalves on the environment should not be neglected given the large scale and high density of bivalve culture in the Changhai sea area and in the coasts of China. However, the type and extent of environmental impact generated by self-pollutant loading in this area remain unknown because of the lack of hydrographic conditions. [Copyright &y& Elsevier]

Abstract: The effects of increased biodeposition within mussel (Mytilus edulis) farms on the benthic environment were investigated using surface sediment samples collected from 11 coastal embayments in Prince Edward Island (PEI), Canada. The degree of organic enrichment, determined using geochemical indicators (total free sulfides (S), redox potentials (EhNHE), water content (WC) and organic matter (OM)), was significantly greater in mussel leases compared to reference sites located both outside lease boundaries and in inlets not used to culture mussel (MANOVA, p <0.001). Post-hoc tests showed that mean WC and OM, EhNHE potentials and S concentration were all significantly different between lease and reference sites (p ≤0.009). Temporal changes in organic enrichment conditions were detected by comparing our 2001 data to those previously reported from a 1997 survey of the same sampling sites (MANOVA, p <0.001). This multivariate effect resulted primarily from a 39% increase in mean S concentration between 1997 and 2001 (p =0.029). Surface sediment variables at reference sites were similar between years. Benthic conditions were discriminated along an oxic–anoxic enrichment gradient using multidimensional scaling analysis. Mussel lease sites sampled in 1997 were clustered within predefined oxic sediment classifications along with the majority of reference sites, but were grouped farther along the enrichment gradient in 2001. The significant increase in hypoxic and sulfidic sediments within mussel farms between 1997 and 2001 is consistent with the 43% increase in PEI mussel production—a classic response to excessive organic biodeposition in shallow coastal inlets with relatively low dispersive capacity. [Copyright &y& Elsevier]

Abstract: The intensive mussel culture carried out in the past 40years in the Rias of Vigo and Arousa (Galicia-NW Spain) has led to substantial changes in the ecology and geochemistry of the seabed in these areas. Organic C enrichment of the seabed has generated strongly reducing conditions that directly affect the geochemistry of Fe and S. In the present study a total of six sediment cores were collected from the seabed under mussel rafts, and two different layers were distinguished: the biodeposit generated by the mussels, and the sediment situated immediately below this. Samples of each were analyzed to determine the pH, redox potential, sulphate and chloride in the interstitial water, as well as total percentage of organic C (TOC), N and S. Sequential extraction of the samples differentiated six fractions of Fe: exchangeable, carbonate, ferrihydrite, lepidocrocite, goethite and pyrite. The contents of total Fe, Fe associated with silicates, Fe soluble in 1M HCl and AVS-Fe were also determined. In general, both the biodeposit and the sediment were anoxic (Eh<100mV) and there were no significant differences between the two in the total Fe or in the Fe associated with silicates, which appears to indicate that the input of Fe to the system did not vary greatly. However, there were significant differences between the sediment and the biodeposit in terms of the forms of Fe in each layer. The concentrations of pyrite in the biodeposit (0.37±0.25μmol g−1) were high but significantly lower than in the sediment (1.10±0.20μmol g−1), and there remained large quantities of reactive-Fe that were susceptible to pyritisation. In contrast, in the sediment, the reactive-Fe was intensively pyritised, and judging from the ratio of TOC–DOP, it limited synthesis of pyrite. Furthermore, a plot of the concentration of pyrite-S against TOC revealed an excess of ∼15% of pyrite-S, which is explained by the partial decoupling of pyrite formation from organic matter accumulation, caused by the formation of pyrite from the H2S generated by the anaerobic oxidation of methane. The latter process also appears to favour, although to a lesser extent, the precipitation of Ca carbonate, with incorporation of Fe. [Copyright &y& Elsevier]

Abstract: Blue mussels and eelgrass have been found to coexist in many locations. However, knowledge of the interactions between these species is limited. Two experiments were conducted in the laboratory, a “Deposit” and an “Epiphyte” experiment. The Deposit experiment examined possible effects of increasing load of blue mussel (Mytilus edulis) biodeposits on sediment biogeochemistry and eelgrass (Zostera marina) performance. Z. marina mesocosms received normal or high loads of mussel biodeposits (Normal and High), while no biodeposits were added to the Control. High dosage had overall negative effects on Z. marina, which was reflected as lower leaf numbers and biomass and accumulation of elemental sulphur in rhizomes. The sediment biogeochemical conditions were altered, as the mussel biodeposits enhanced sulphate reduction rates and increased sulphide concentrations in the porewater, which may result in sulphide invasion and reduced growth of Z. marina. In the Epiphyte experiment effects of mussel excretion, with particular emphasis on ammonium, on the growth of Z. marina and their epiphytes were examined. A thick cover of epiphytes developed on Z. marina growing together with M. edulis, and the relative growth rate was reduced with 20% compared to plants from control without mussels. Overall the experiments showed negative effects on Z. marina growing together with M. edulis, thereby supporting a preceding field study by Vinther et al. [Vinther, H.F., Laursen, J.S., Holmer, M. 2008. Negative effects of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds in Flensborg fjord, Denmark. Est. Coast Shelf. Sci. 77, 91-103.]. [Copyright &y& Elsevier]

Abstract: Growth and production of California sea cucumbers (Parastichopus californicus Stimpson), co-cultured with suspended Pacific oysters (Crassostrea gigas Thunberg), were investigated in a 12-month (January 2004–January 2005) study conducted at two sites of deep-water, suspended oyster culture in British Columbia, Canada. Rates of oyster biodeposition (faeces and pseudofaeces) and the utilization of this particulate material as a food source by P. californicus were also examined. Peaks in sedimentation rates through 8.5 m water depth, below the oyster rafts, were observed in April (93.6 g dry wt m− 2 d− 1) and July (91.9 g dry wt m− 2 d− 1) 2004. At the two study sites, maximum mean total organic carbon deposition rate at 8.5 m depth occurred in July 2004 and amounted to 3123 and 3830 mg dry wt C m− 2 d− 1. Maximum mean total nitrogen deposition rate at the two sites was 524 and 568 mg dry wt N m− 2 d− 1 which occurred in November and July 2004, respectively. Mean C/N ratios of particulate material in the sediment trap samples collected at the two sites between January and November 2004 ranged between 5.9 and 12.4 and may be considered to be of high nutritional value. Growth and survivorship of sea cucumbers held in experimental trays below the suspended oysters were measured, growth being assessed using split weight as well as muscle and skin wet weights. There were no sea cucumber mortalities in any of the trays deployed at either site during the study. Sea cucumbers grown in trays at both sites successfully utilized biodeposits from the cultured oysters and showed a mean weight increase of 42.9 g in approximately 12 months (average growth rates at both sites ranged from 0.061 to 0.158 g d− 1). Overall growth was affected by the absence of visceral organs and the cessation of feeding activity observed in the November 2004 sampling period. Overall mean values (for the two study sites) for organic content were significantly higher in the foregut of the sea cucumbers (24.7 % or 224.6 mg g− 1 dry sediment) than in the sediment (5.9% or 51.6 mg g− 1 dry sediment) or in the hindgut (14.5% or 157.9 mg g− 1 dry sediment), showing both active selection of organic material from the sediments and digestion/assimilation of these organics in the gut. Organic material deposited in the trays was assimilated by P. californicus at the two study sites with an average efficiency of 40.4%. The successful utilization of the naturally-available biodeposits from the cultured Pacific oysters by California sea cucumbers suggests the feasibility of developing a commercial-scale co-culture system that would both reduce the amount of organic deposition underneath shellfish farms and produce a secondary cash crop. [Copyright &y& Elsevier]

Abstract: The main objectives of this study were: 1) to determine the influence of water currents on the suspension feeding rate of cockles (Cerastoderma edule); 2) to quantify the interaction between cockle feeding and flow on algal cell depletion in the overlying water column, and 3) to measure the effect of flow on resuspension of their pseudofaeces and faeces. Flume experiments demonstrated that suspension feeding rate (i.e. clearance rate) of C. edule was not significantly affected by increasing current speed, at least between 5 and 35 cm s−1. Measurement of vertical profiles in algal cell concentrations within the water column showed a marked depletion above the bed, and the size of this was inversely related to currents'' speeds below 5 cm s−1. At 2 cm s−1 the algal cell depletion was maximum immediately above the bed. However, below currents of 1 cm s−1 the maximum depletion was at 10 cm above the bed. This was a result of the exhalent jet of the cockle pumping filtered water (i.e. algal free) vertically into the water column and above the intake level of the inhalant siphon. Such stratification of the water column would appear to be beneficial to the cockle because it reduces the degree of re-filtration of algal cell depleted water at times of low flow, when there is poor mixing and thus poor replenishment of phytoplankton to the boundary layer. Critical erosion thresholds for cockle biodeposits, produced from a diet of silt and unicellular algae, were recorded at current velocities of 15 and 25 cm s−1, or shear velocities of 0.6 and 1.0 cm s−1, for pseudofaeces and faeces respectively. [Copyright &y& Elsevier]

Abstract: Forty four core samples were analyzed to determine sediment particle size, total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen and total sulphur. Sequential extraction of S was also carried out, differentiating AVS (acid volatile sulphide), elemental S, organic S and pyrite S. The results obtained show that the presence of mussel rafts causes intense changes in the physicochemical composition and properties of the sea floor in the Rı́a de Arousa. The percentage of silt and clay, TOC, TIC and total N were significantly higher in the biodeposit than in the sediment. In contrast, there were no differences between the biodeposit and the sediment in terms of pH (8.0–8.7) and redox potential. The sediment and biodeposit were always anoxic, with values of redox potentials below −100mV. In accordance with these conditions, the dominant fraction of S was pyrite S (FeS2). The AVS fraction and elemental S were present at low concentrations, except in the uppermost part of each core. Pyrite was relatively stable when the biodeposit and sediment were maintained in suspension for 8 days in oxic sea water; unlike the AVS fraction, which disappeared within a few hours. [Copyright &y& Elsevier]

Dreissenid mussels (Dreissena polymorpha and D. bugensis) biodeposit large quantities of filtered materials (i.e., feces and pseudofeces) directly on bottom substrates. These biodeposits have the potential to increase oxygen demand in sediments and overlying waters and thus contribute to hypolimnetic anoxia in Lake Erie. We hypothesized that higher potential oxygen demand of sediments would occur in areas near shore than in offshore hypolimnetic waters as a result of biodeposits carried by currents from littoral water where mussels, available foods, and biodeposits may be most abundant. To address this hypothesis, we measured potential oxygen demand (mg O2/L/120 h incubation) at six sites near shore and six sites offshore monthly June to September 2002 and August 2003. In addition, we compared, in post priori hypothesis, seven sites with and five sites without dreissenid mussels. Contrary to our hypotheses, potential oxygen demand was not significantly higher in bottles containing nearshore sediments than offshore sediments. Similarly, potential oxygen demand was not significantly higher at sites with dreissenid mussels than at sites without mussels. Data are consistent with pre-dreissenid studies which show oxygen demand and percent ash-free dry weights of sediments were higher offshore than near shore and ash-free dry weight of sediments decreased June to September. Therefore, the present study provides no evidence that dreissenid mussels have contributed directly—via biodeposition—to increased anoxia observed in Lake Erie in the mid to late 1990s. [ABSTRACT FROM AUTHOR]

Abstract: Current meter data, biodeposit settling velocity, turbulent diffusivity and water depth were combined to model the initial depositional distribution of faecal and pseudofaecal pellets at three aquaculture farm sites in sheltered to exposed environments in the Marlborough Sounds. Model results were compared with seabed sediment samples collected at each site. At the sheltered sites, comparison of the modelled dispersal pattern and seabed identification of mussel biodeposits using sedimentological data indicated a very close association. Both were found to reduce to natural levels approximately 30–50m from the farm site. Such similarity between the model and observed distribution of the mussel biodeposits suggested that, once deposited on the seabed, the biodeposits remain immobile due to the low hydrodynamic energy of the two sites. In contrast, the exposed site had only a poor correlation between the dispersal model and identification of mussel biodeposits on the seabed. The dispersal model indicates that the majority of mussel biodeposits initially accumulate within 50m of the farm. However, observations found no sign of any mussel biodeposits in sediment beneath or up to 200m from the farm boundary. This lack of biodeposits indicates that there is at times sufficient energy to re-suspend mussel biodeposits and to disperse these deposits over a wide enough area thereby leaving little impact on the natural sediment. [Copyright &y& Elsevier]

Abstract: The trace elements present at highest concentrations were Cr and Zn, which probably originated from the dumping of effluent from a tanning factory. High proportions of these two elements were associated with the residual fraction. Biodeposits and sediments showed high concentrations of Cd and Pb in the reactive fraction, with a high proportion of the concentration in the reactive fraction being associated with carbonates. Nickel showed a higher degree of pyritization than the previous elements, although most of the Ni was associated with the residual and reactive fractions. Arsenic, Hg and Cu showed high degrees of pyritization, particularly below a depth of 5 cm. The results demonstrate that those elements with a high degree of pyritization may be released into the water through oxidation of the metal sulphides that they form when in suspension in oxic sea water, with the subsequent risk of increased bioavailability to benthic fauna. [Copyright &y& Elsevier]

The present study examined for differences in macroinvertebrate assemblage composition inside and outside of mussel farm sites experiencing different hydrodynamic regimes. Multivariate analysis revealed that there were significant differences in macroinvertebrate assemblage composition (averaged across seasons) between samples taken inside and outside of the two relatively low energy sites, whilst no such difference was observed for the relatively high energy site. Taxa that best disciminated between the dissimilarities observed in macroinvertebrate assemblage composition inside and outside farms were principally polychaetes (more abundant inside) and ophiuroids (more abundant outside). Sediment total organic matter and number of mussel shells were the parameters that best explained the difference in macroinvertebrate assemblage observed at the two relatively sheltered farm study sites. No taxa or environmental variables were particularly good at discriminating or explaining differences observed inside and outside the relatively high energy farm site. The present study indicates there is a relationship between the hydrodynamic regime of a farm site, organic enrichment of seabed sediments by mussel biodeposits, and a subsequent modification of the macroinverebrate assemblages. This finding has implications for the siting of mussel farms in coastal environments. [Copyright &y& Elsevier]

Seasonal patterns of Chl a in water samples, sedimentation rates (total dry weight per area per day) and content of total carbon, total nitrogen, and total phosphorus in sediment trap samples, as well as in sediment samples, were measured at several stations in Ofunato estuary, Japan. High rates of sedimentation to the bottom were observed in March and September, corresponding to elevated concentrations of Chl a. In the middle part of the estuary, the peaks of sedimentation rate and fluxes of chemical elements through the 20-m deep layer in September amounted to 23 g m−2d−1, 2200 mg C m−2d−1, 290 mg N m−2d−1, and 28 mg P m−2d−1, coinciding with oxygen depletion in deeper layers. Seasonal changes in sedimentation can be explained by marked increases in biodeposits from oysters cultured in the surface layers. However, no marked seasonal changes in chemical elements were found within the sediment, suggesting high degradation rates of biodeposits at the sediment-water interface. Biodeposits from culture rafts were estimated using a population dynamic model for the Japanese oyster. This model gave predictions in agreement with observed seasonal changes in biodeposition fluxes through the 20-m layer in September, with a minimum estimation of 5.1 g m−2d−1 with uniform seawater dispersion, and a maximum estimation of 390 g m−2d−1 without dispersion. [ABSTRACT FROM PUBLISHER]

The pattern of elements accumulation in biodeposits formed by living organisms and extracellular products of their metabolism (biofouling, primary soils) on different bedrocks (of the monuments of Historical necropoleis in Saint Petersburg) were studied by a complex of biological and mineralogical methods (optical microscopy, SEM, EDX, XRD, ICP MS, XRFS). The content of 46 elements in biodeposits with various communities of microorganisms is determined. The model recreating the picture of the input and selective accumulation of elements in biodeposits on the stone surface in outdoor conditions is assumed. It is shown that the main contribution to the elemental composition of biodeposits is made by the environment and the composition of the microbial community. The contribution of leaching under the action of microbial metabolites of mineral grains, entering biodeposits from the environment, is significantly greater than that of the underlying rock. [ABSTRACT FROM AUTHOR]

Microplastics (MP) are omnipresent contaminants in the oceans, however little is known about the MP transfer between marine compartments and species. Three connected laboratory experiments using the filter-feeding mussel Mytilus galloprovincialis and the omnivorous polichaete Hediste diversicolor were conducted to evaluate whether the filtering action by mussels affects the vertical transfer of MP of different sizes (MP SMALL = 41 μm; MP LARGE = 129 μm) and densities (polyamide = 1.15 g cm−3; polypropylene = 0.92 g cm−3) across compartments and species with different feeding modes. Mussels significantly removed MP from the water column by incorporating them into biodeposits. This effect was particularly evident for the MP SMALL , whose deposition from the water column to the bottom was enhanced (about 15%) by the action of mussels. The incorporation of MP into faecal pellets increased the particles' sinking velocity by about 3–4 orders of magnitude. Conversely, the MP presence significantly decreased the depositional velocities of faecal pellets, and the magnitude of this effect was greater with increasing MP size and decreasing density. The MP incorporation into mussels' biodeposits also more than doubled the amount of MP uptake by H. diversicolor. We conclude that detrital pathways could be a transfer route of MP across marine compartments and food webs, potentially affecting the distribution of MP in sediments and creating hot-spots of bioavailable MP. Image 1 • Mussels removed MP from the water column incorporating them into biodeposits. • Mussels accelerated the vertical fluxes of MP from the water column to the bottom. • The presence of MP decelerated the sinking velocity of faecal pellets. • The incorporation of MP into biodeposits facilitated their uptake by polychaetes. Mussels' biodeposits facilitate MP transfer from the water column to benthic detritus-feeding polychaetes. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the presence and potential toxic effects of plastic fragments (<400 μm) of polyethylene and polypropylene on the Pacific oyster Crassostrea gigas. Oysters were exposed to environmentally relevant concentrations (0, 0.008, 10, 100 μg of particles/L) during 10 days, followed by a depuration period of 10 days in clean seawater. Effects of microplastics were evaluated on the clearance rate of organisms, tissue alteration, antioxidant defense, immune alteration and DNA damage. Detection and quantification of microplastics in oyster's tissues (digestive gland, gills and other tissues) and biodeposits using infrared microscopy were also conducted. Microplastics were detected in oyster's biodeposits following exposure to all tested concentrations: 0.003, 0.006 and 0.05 particles/mg of biodeposits in oysters exposed to 0.008, 10 and 100 μg of particles/L, respectively. No significant modulation of biological markers was measured in organisms exposed to microplastics in environmentally relevant conditions. • No detection of microplastics in oysters' tissues. • Identification of microplastics in biodeposits of oysters. • No effects of microplastics on oxidative stress, DNA damage or immune marker. • No effects of microplastics on oyster physiology and tissue integrity. [ABSTRACT FROM AUTHOR]

The pattern of elements accumulation in biodeposits formed by living organisms and extracellular products of their metabolism (biofouling, primary soils) on different bedrocks (of the monuments of Historical necropoleis in Saint Petersburg) were studied by a complex of biological and mineralogical methods (optical microscopy, SEM, EDX, XRD, ICP MS, XRFS). The content of 46 elements in biodeposits with various communities of microorganisms is determined. The model recreating the picture of the input and selective accumulation of elements in biodeposits on the stone surface in outdoor conditions is assumed. It is shown that the main contribution to the elemental composition of biodeposits is made by the environment and the composition of the microbial community. The contribution of leaching under the action of microbial metabolites of mineral grains, entering biodeposits from the environment, is significantly greater than that of the underlying rock.