Mussel Larvae Research Articles

Density of Limnoperna fortunei larval stages in a cascade of subtropical reservoirs: spatiotemporal variation and environmental influences.

The golden mussel (Limnoperna fortunei) is an invasive bivalve that has established itself in several South American river systems, impacting ecosystem functioning. Reservoir cascades provide their larvae with the means of rapid dispersal, but the relationship between environmental variables and larval stage structure remains unclear. In this study, the density of three L. fortunei larval stages and quantitative detection using DNA are analyzed in a cascade of five reservoirs in the upper Uruguay River Basin and associated with spatiotemporal variation in environmental parameters. The analysis of L. fortunei eDNA presence and absence in freshwater systems appears to be a valuable mapping tool; however, no significant link was found between the eDNA magnitude and the overall larval density. The increase in larval density was related to the fluctuation of environmental parameters over a year, with the highest average larval densities observed in the CN and ITA reservoirs, though no significant difference was observed between the five reservoirs, where D-shaped larvae predominated. During winter, larval density decreased significantly, however, other variables also contribute to species activity and development in the upper Uruguay River Basin reservoirs and may be considered limiting factors. The relationships between environmental parameters were evaluated using a multivariate model. The interaction between reservoir area and precipitation, water temperature, electrical conductivity, and dissolved oxygen had a significant effect on larval density but showed specific influences on each larval stage. Any increase in density was regulated by dissolved oxygen and electrical conductivity content at all larval stages. Furthermore, total phosphorus affected the density of F1 and F3 larvae. The interaction between reservoir area and precipitation, nitrate content, phosphate concentrations, and water temperature had the most influence on the density of F2 and F3 larval stages; the F1 stage was mainly affected by calcium concentrations. The isolated effect of precipitation also contributed to the density of F2 and F3 larvae. Our findings shed light on the interaction between different phases of golden mussel larvae and the main nutrients found in reservoirs, which may be a determining factor in the rise in density of the non-native species in these systems.

Reciprocal transplant experiments demonstrate a dynamic coevolutionary relationship between parasitic mussel larvae and bitterling fishes

Abstract The coevolutionary dynamic of host–parasite associations varies from strictly local adaptations to diffuse guild coevolution. How innate and acquired immune responses modulate host resistance to parasitism and how host specificity and geographic scaling affect the efficacy of host response have consequences for range dynamics and biological invasions. Using reciprocal transplant experiments, we tested whether local or diffuse coevolution shapes host response to parasitism in the host–parasite association between bitterling fishes and larval stages (glochidia) of freshwater mussels from Europe and East Asia. We found that glochidia initially indiscriminately attached to all study host species, but immune responses elicited significant differences in host responses within 24 h of infection, which intensified during glochidial development. European bitterlings were more resistant to European glochidia and Asian bitterlings to Asian glochidia, with the strongest geographic bias in resistance in the Asian bitterling hosts. This finding suggests a strong effect of local adaptation but also indicates the non‐negligible role of coevolutionary hotspots. Low natural glochidia load on bitterling species overall hence arise from competent immune response rather than glochidia avoidance behaviour. Bitterling immune response is primarily innate and not acquired. Overall, our data demonstrate the complex outcome of parasite pressure on the evolution of host resistance, and important role of geographically structured coevolution in shaping host response.

Interactive impact of residual pyrethroid compounds used in the Chilean salmon farming industry and coastal acidification conditions on the feeding performance of farmed mussels in northern Patagonia

The use of pyrethroids in aquaculture has been an important component of achieving a thriving salmon farming industry in Chile. While the residual presence of such substances is known to depend on environmental conditions, most ecotoxicological studies to date have not considered environmental context. Here, we conducted oceanographic monitoring combined with experiments aiming to estimate the effects of two pyrethroids on the feeding rates of larvae of farmed mussels, Mytilus chilensis. In additional experiments, mussel spats were exposed to both pyrethroids, but under contrasting temperature/pH so as to mimic winter and summer conditions. Experiments mimicking spring conditions revealed that both pyrethroid substances affected the feeding of mussel larvae as a function of concentration. Conversely, significant impact of pyrethroids on adults were not observed with regard to temperature and pH, but a significant impact of low temperature/low pH condition on ingestion rates was confirmed. Given the current status of increasing ocean acidification, the results of this study are expected to provide useful information with regard to achieving sustainable mussel aquaculture, especially considering both activities occur in similar geographic areas, and the expansion of salmon farming areas is ongoing in Chile.

Morphometric features of larvae of the mussel Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia: Mytilidae) in ontogenesis

Sequentially appearing in ontogenesis, the morphometric features of mussel Mytilus galloprovincialis larvae can serve as a basis for their species identification among the pool of larvae of other bivalve mollusc species found in the Black Sea plankton. The study presents the photographs of live mussel larvae and scanning electron microscope (SEM) images of the larvae hinge at different developmental stages: D-veliger, veliger, veliconcha and pediveliger. There was shown the sequence of morphological changes in provinculum, as well as the shell’s size and shape changes, from the earliest straight-hinge stage of veliger up to metamorphosis. The correlation between shell width (C, µm) and shell length (L, µm) [ ; R2 = 0.9879], as well as the correlation between hinge edge length (l, µm) and shell length (L, µm) [ ; R2 = 0.9872] were determined for mussel larvae ranging in size from 98 to 350 µm. By employing energy dispersive X-ray spectroscopy EDS(x), the elemental composition of the larvae shell’s hinge edge at the stages of veliger, veliconcha and pediveliger was determined; and it showed the presence of calcium, carbon, oxygen, sodium and chlorine. Magnesium was detected in pediveligers’ hinge edge only.

Differential effects of antidepressant sertraline in glochidia-fish interactions involving drug transfer from parasite to host

This study examined the impact of sertraline, an antidepressant common in treated wastewater, on the host-parasite dynamics between parasitic freshwater mussel (Unio tumidus, Unionidae) larvae (glochidia) and their host fish (Squalius cephalus, Cyprinidae). Employing a full-factorial design, both fish and glochidia were subjected to sertraline at the combinations of 0 µg L−1 (control), 0.2 µg L−1 (environmentally relevant concentration), and 4 µg L−1 (elevated concentration, short-term exposure of the parasite). The results showed that long-term host exposure (involving intensive sertraline accumulation in the fish brain) marginally increased subsequent glochidia attachment success by 2 %, while parasite exposure at the same environmentally relevant concentrations had no detectable effect. There was also no effect of exposure of glochidia to 0.2 µg L−1 of sertraline on their viability and encapsulation success during the initial parasitic stage. However, a significant alteration in attachment behavior, marked by a 3.3 % increase in attachment success and changes in the glochidia spatial distribution on the host body, was noted after 24 h of glochidia exposure to 4 µg L−1 of sertraline. Importantly, this study provides the first evidence of sertraline transfer from exposed glochidia to nonexposed host fish, as indicated by elevated levels of sertraline (12.8 ng g−1) in the brain tissue of nonexposed hosts. These findings highlight the subtle yet significant effects of pharmaceutical pollutants on freshwater ecosystems but also underscore the importance of understanding the unexpected dynamics of such contamination to predict and address future ecological changes.

Bacterial c-di-GMP triggers metamorphosis of mussel larvae through a STING receptor

Bacteria induced metamorphosis observed in nearly all marine invertebrates. However, the mechanism of bacteria regulating the larvae-juvenile metamorphosis remains unknown. Here, we test the hypothesis that c-di-GMP, a ubiquitous bacterial second-messenger molecule, directly triggers the mollusc Mytilus coruscus larval metamorphosis via the stimulator of interferon genes (STING) receptor. We determined that the deletion of c-di-GMP synthesis genes resulted in reduced c-di-GMP levels and biofilm-inducing activity on larval metamorphosis, accompanied by alterations in extracellular polymeric substances. Additionally, c-di-GMP extracted from tested varying marine bacteria all exhibited inducing activity on larval metamorphosis. Simultaneously, through pharmacological and molecular experiments, we demonstrated that M. coruscus STING (McSTING) participates in larval metamorphosis by binding with c-di-GMP. Our findings reveal that new role of bacterial c-di-GMP that triggers mussel larval metamorphosis transition, and extend knowledge in the interaction of bacteria and host development in marine ecosystems.

Novel Algorithm to Detect, Classify, and Count Mussel Larvae in Seawater Samples Using Computer Vision

The European Union’s mussel production industry is dependent on obtaining mussel larvae as seed for cultivation, a process traditionally monitored through labor-intensive manual sampling and microscopic counting prone to human error and time-consuming procedures. To address these challenges, our research presents a computer vision-based methodology for accurately identifying, classifying, and quantifying mussel larvae individuals across various developmental stages from microscopic images of water samples. Utilizing a neural network architecture derived from the YOLO method, our approach integrates convolutional, pooling, and fully connected layers to automate detection, classification, and accounting tasks. Through training with manually labeled samples and employing data augmentation techniques, we established a robust framework capable of processing diverse larval specimens effectively. Our research not only streamlines mussel larvae monitoring processes but also underscores the potential of computer vision techniques to enhance efficiency and accuracy in aquaculture industries.

The mussel larvae microbiome changes in response to a temperature rise

Ocean warming caused by global climate change influences the function, diversity, and community dynamics of commensal microorganisms, including the hemolymph and the gut microbiota in mussels. However, the microbiota in hard-shelled mussel (Mytilus coruscus) larvae and the effect of temperature on the microbial community structure have yet to be studied. Herein, we investigated the core microbiota of M. coruscus larvae and the impact of acute (4 h) and gradual (4 days) exposure to a rise in seawater temperature from 21 to 25 °C. Eleven core genera were identified in M. coruscus larvae by 16S rDNA gene sequencing: Alteromonas, Brevundimonas, Delftia, Microbacterium, Neptuniibacter, Neptunomonas, Pseudoalteromonas, Rhodococcus, Stenotrophomonas, Tenacibaculum, and Thalassotalea. The microbiota of larvae in the short exposure treatment was similar to the control. However, the abundance of Delftia, Neptunomonas, Pseudoalteromonadaceae, Rhodococcus, and Stenotrophomonas decreased significantly in the long-exposure larvae. In contrast, at the genus level, the abundance of Tenacibaculum increased significantly. Diversity and multivariate analyses confirmed that the microbiota patterns were linked to seawater warming over the long term. Microbiota diversity did not change significantly, regardless of whether the seawater temperature increased quickly or slowly; however, we observed a significant increase in the microbiota species abundance at higher temperatures. Among the altered bacterial genera, Delftia, Neptunomonas, and Rhodococcus function in the degradation of organic compounds; Pseudoalteromonas is closely associated with mussel attachment and metamorphosis, and Tenacibaculum is an opportunistic pathogen that can cause marine mollusk death. The results suggest that marine heat waves caused by climate change may reduce the ability of symbiotic bacteria to degrade environmental toxins, will affect mussel larvae metamorphosis, and increase the abundance of opportunistic pathogens, thereby increasing the risk of disease and death of mussel larvae.

First record of mussel larvae occurring in the mantle cavity of littoral-dwelling Mytilus spp. in Svalbard, Arctic

First record of mussel larvae occurring in the mantle cavity of littoral-dwelling Mytilus spp. in Svalbard, Arctic

Flatworm Transcriptomes Reveal Widespread Parasitism by Histophagous Ciliates.

Unicellular ciliates like Tetrahymena are best known as free-living bacteriovores, but many species are facultative or obligate parasites. These "histophages" feed on the tissues of hosts ranging from planarian flatworms to commercially important fish and the larvae of imperiled freshwater mussels. Here, we developed a novel bioinformatics pipeline incorporating the nonstandard ciliate genetic code and used it to search for Ciliophora sequences in 34 publicly available Platyhelminthes EST libraries. From 2,615,036 screened ESTs, we identified nearly 6,000 high-confidence ciliate transcripts, supporting parasitism of seven additional flatworm species. We also cultured and identified Tetrahymena from nine terrestrial and freshwater planarians, including invasive earthworm predators from the genus Bipalium and the widely studied regeneration models Dugesia japonica and Schmidtea mediterranea. A co-phylogenetic reconstruction provides strong evidence for the coevolution of histophagous Ciliophora with their Platyhelminthes hosts. We further report the antiprotozoal aminoglycoside paromomycin expels Tetrahymena from S. mediterranea, providing new opportunities to investigate the effects of this relationship on planarian biology. Together, our findings raise the possibility that invasive flatworms constitute a novel dispersal mechanism for Tetrahymena parasites and position the Platyhelminthes as an ideal model phylum for studying the ecology and evolution of histophagous ciliates.

Sustainable oyster shell incorporated artificial reef concrete for living shorelines

An innovative pervious concrete containing recycled oyster shells for artificial reef structures has been developed. The new artificial reef concrete incorporating oyster shells contained higher amounts of supplementary cementitious material and sea sand instead of river sand. Investigations on homogeneity, strength characteristics, pH levels and mussel larvae (Mytilus galloprovincialis) settlement were performed to verify the effectiveness of different constituents. The proposed concrete mixes have the potential for use in artificial reef construction representing improved characteristics with regards to weight, cost, environmental sustainability, carbon footprint and attachment of shellfish larvae to the reef, enabling nature-based coastal protection solutions, or ‘living shorelines.

A sensitivity analysis of mussel larvae dispersal in a Danish estuary based on a biophysical model

Larval dispersal is dependent on multiple physical and biotic factors and is a key driver of population connectivity. Connectivity is believed to be important in determining how species will cope in a changing climate by allowing species’ ranges to expand or constrict in response to environmental shifts. In the following study, we couple a 3D physical model system with an individual-based model to answer whether climate change effects on mussel larvae will affect the dispersal and the structure of the demographic connectivity in the Limfjorden. The Limfjorden in Denmark supports a large mussel fishery of the species Mytilus edulis and extensive mussel farming, which may be impacted by changes in larval supply under climate change. We produced scenarios changing the pelagic larval duration, spawning time, and presence of spawning mussels after events of hypoxia, and analysed the changes in potential larval recruitment. The results showed that only the 6-day and 36-day pelagic larval duration scenarios are significantly different from the reference scenario. There was no significant event on changes in spawning time. We described the hydrography of the basins to explain the connectivity results and concluded that severe events of hypoxia could potentially lead to the isolation of the fjord. Overall, this well-connected system is very stable to the changes addressed in this study. It is important to continue the research in this area since the adaptation and evolution of species in a changing ocean will bring discoveries that will be useful for future management and conservation decisions.

The biocide triclosan as a potential developmental disruptor in Mytilus early larvae

The broadly utilized biocide triclosan (TCS) is continuously discharged in water compartments worldwide, where it is detected at concentrations of ng-µg/L. Given its lipophilicity and bioaccumulation, TCS is considered potentially harmful to human and environmental health and also as a potential endocrine disruptor (ED) in different species. In aquatic organisms, TCS can induce a variety of effects: however, little information is available on its possible impact on invertebrate development. Early larval stages of the marine bivalve Mytilus galloprovincialis have been shown to be sensitive to environmental concentrations of a number of emerging contaminants, including EDs. In this work, the effects of TCS were first evaluated in the 48 h larval assay in a wide concentration range (0.001–1,000 μg/L). TCS significantly affected normal development of D-veligers (LOEC = 0.1 μg/L; EC50 = 236.1 μg/L). At selected concentrations, the mechanism of action of TCS was investigated. TCS modulated transcription of different genes involved in shell mineralization, endocrine signaling, ceramide metabolism, and biotransformation, depending on larval stage (24 and 48 h post-fertilization-hpf) and concentration (1 and 10 μg/L). At 48 hpf and 10 μg/L TCS, calcein staining revealed alterations in CaCO3 deposition, and polarized light microscopy showed the absence of shell birefringence due to the mineralized phase. Observations by scanning electron microscopy highlighted a variety of defects in shell formation from concentrations as low as 0.1 μg/L. The results indicate that TCS, at environmental exposure levels, can act as a developmental disruptor in early mussel larvae mainly by interfering with the processes of biomineralization.

Optimization of experimental conditions for exposure of larval mussels (Mytilus californianus) to microplastic particles

Inputs of plastic pollution in marine environments continue to increase, making it essential to understand potential impacts on commercially important marine and estuarine species. Bivalve larvae have been shown to take up micro- and nano-sized plastics; however, exposures detailed in the literature often do not account for particle dynamics, such as eco-corona formation, agglomeration, or settlement. There is clearly a need to define and maintain suspended particle concentrations during exposure periods, while using culture systems that support the growth and survival of the test organism. Therefore, experiments were designed to optimize the components of an exposure system for both particle suspension, as well as larval mussel growth and survival. The suspension and clumping of 2 μm ultra-pure latex beads were assessed to determine the influence of flask shape, agitation, and dispersant type. These results were paired with an assessment of the effects of antibiotics, flask shape, flask rotation, and dispersant type on mussel larvae growth and survival. The combination of these experiments revealed that the optimum system for exposure of bivalve larvae to micro-sized plastics was in rotating, dimple-bottom flasks with additions of 2.5 mg.L−1 methyl cellulose and 2 mg.L−1 chloramphenicol in natural, 1 μm filtered seawater. This optimized system was used to assess the impacts of 2 μm ultra-pure latex beads on the survival and growth of Mytilus californianus larvae. First, a dose-response experiment was carried out to assess the impacts of a two-week exposure of larval mussels to microplastics concentrations that were 0%, 20%, 33.3%, 42.9%, and 50% of total cell volume of the algal ration. For these experiments the algal rations were all kept at 100%. Subsequently, a second experiment was carried out to assess impacts of a two-week exposure of larval mussels to microplastics where both the percent by volume of the algal (0–100%) ration and beads (0–100%) varied so that the total particle volume in the exposures remained constant (100% total). When algal food rations were held constant, a dose-dependent decrease in growth was observed with increasing concentrations of beads. When algal rations decreased, growth and survival decreased to a greater extent when microplastic beads were present. These results indicate that both concentrations of microplastic particles and volumetric ratios of algae rations to microplastic particles determine responses of mussel larvae, with microplastics having a greater effect on larval survival when added to low algal rations.

Assessing the Impact of Microplastic Filaments Contaminated with PAHs on Mytilus coruscus Larvae through Surface Contact.

In recent years, microplastics have been of great concern in environmental and health research. In field surgeries and laboratory investigations, research interests were focused on the retention of microplastics inside of animals by ingestion and the series of negative effects after that. However, such large plastic debris and filaments are hardly eaten by small animals, like zooplankton, planktonic larvae, etc. In this study, the surface contact between plastic filaments contaminated with polycyclic aromatic hydrocarbons (PAHs) and mussel pediveliger larvae has been investigated to figure out the effects of "non-digestive tract route of exposure" on subject animals. In a 1600 mL artificial seawater medium, high mortalities of mussel larvae were recorded after being exposed to two PAHs-contaminated (benzo[α]pyrene (BaP) and phenanthrene (Phe)) filaments for 5 days, 68.63% for BaP and 56.45% for Phe on average. We suggest that the surface contact was the dominant pathway to transfer PAHs from contaminated filaments to larvae and that the risk of contaminated plastic ropes transferring hydrophobic organic compounds (HOCs) to larvae in mussel aquaculture should be taken seriously.

Exposure to Alexandrium spp. impairs the development of Green-lipped mussel (Perna canaliculus) embryos and larvae

The green-lipped mussel (GLM) Perna canaliculus is an economically, ecologically, and culturally important species in Aotearoa New Zealand. Since 2011, harmful algal blooms (HABs) of Alexandrium spp. have occurred annually in the Marlborough Sounds, the largest GLM aquaculture region in New Zealand. Across a similar timeframe, there has been a severe reduction in wild spat (juvenile mussel) catch. This research investigated the effects of Alexandrium pacificum (which produces paralytic shellfish toxins; PSTs) and A. minutum (a non-producer of PSTs) on the development of four GLM larval life stages (gametes, embryos, D-stage and settlement).Early life stages of GLM were exposed to environmentally relevant concentrations of Alexandrium spp. as whole cell, lysate and filtrate treatments. A 48-h exposure of embryos to whole A. pacificum cells at 500 cells mL−1 caused lysis of embryos, severe abnormalities, and reduced development through to veliger (D-stage) larvae by 85%. GLM growth was impaired at cell concentrations as low as 250 cells mL−1 during a 4-day exposure of D-stage larvae to both Alexandrium spp. Exposure of GLM to both whole and lysed treatments of Alexandrium spp. at 500 cells mL−1 resulted in halved larval growth rates (2.00 µm day−1 vs 4.48 µm day−1 in the control) and growth remained impeded during a 4-day recovery period.Both A. pacificum and A. minutum were found to negatively impact D-larvae. Both whole-cell and lysed-cell treatments of A. pacificum had similar negative effects, suggesting that Alexandrium spp. toxicity to D-larvae is independent of PSTs. Additionally, cell membrane-free treatments of A. pacificum had no negative effects on embryo development, indicating that cell surface-associated bioactive compounds may be responsible for the observed negative effects during this early life stage.Conversely, non-PST-producing A. minutum was toxic to D-stage larvae but not to embryos; larval growth was reduced following a brief 1 h exposure of sperm to cell membrane-free treatments of A. pacificum. No effects were recorded in GLM larvae exposed during settlement, highlighting the potential for differences in susceptibility of early life stages to Alexandrium spp. exposure and the influence of exposure durations.In the wild, blooms of Alexandrium spp. can persist for several months, reaching cell densities higher than those investigated in the present study, and as such may be detrimental to the vulnerable early life stages of GLM.

Plasticity, Paralogy, and Pseudogenization: Rhabdoviruses of Freshwater Mussels Elucidate Mechanisms of Viral Genome Diversification and the Evolution of the Finfish-Infecting Rhabdoviral Genera.

Viruses in the family Rhabdoviridae display remarkable genomic variation and ecological diversity. This plasticity occurs despite the fact that, as negative sense RNA viruses, rhabdoviruses rarely if ever recombine. Here, we describe nonrecombinatorial evolutionary processes leading to genomic diversification in the Rhabdoviridae inferred from two novel rhabdoviruses of freshwater mussels (Mollusca: Bivalvia: Unionida). Killamcar virus 1 (KILLV-1) from a plain pocketbook (Lampsilis cardium) is closely related phylogenetically and transcriptionally to finfish-infecting viruses in the subfamily Alpharhabdovirinae. KILLV-1 offers a novel example of glycoprotein gene duplication, differing from previous examples in that the paralogs overlap. Evolutionary analyses reveal a clear pattern of relaxed selection due to subfunctionalization in rhabdoviral glycoprotein paralogs, which has not previously been described in RNA viruses. Chemarfal virus 1 (CHMFV-1) from a western pearlshell (Margaritifera falcata) is closely related phylogenetically and transcriptionally to viruses in the genus Novirhabdovirus, the sole recognized genus in the subfamily Gammarhabdovirinae, representing the first known gammarhabdovirus of a host other than finfish. The CHMFV-1 G-L noncoding region contains a nontranscribed remnant gene of precisely the same length as the NV gene of most novirhabdoviruses, offering a compelling example of pseudogenization. The unique reproductive strategy of freshwater mussels involves an obligate parasitic stage in which larvae encyst in the tissues of finfish, offering a plausible ecological mechanism for viral host-switching. IMPORTANCE Viruses in the family Rhabdoviridae infect a variety of hosts, including vertebrates, invertebrates, plants and fungi, with important consequences for health and agriculture. This study describes two newly discovered viruses of freshwater mussels from the United States. One virus from a plain pocketbook (Lampsilis cardium) is closely related to fish-infecting viruses in the subfamily Alpharhabdovirinae. The other virus from a western pearlshell (Margaritifera falcata) is closely related to viruses in the subfamily Gammarhabdovirinae, which until now were only known to infect finfish. Genome features of both viruses provide new evidence of how rhabdoviruses evolved their extraordinary variability. Freshwater mussel larvae attach to fish and feed on tissues and blood, which may explain how rhabdoviruses originally jumped between mussels and fish. The significance of this research is that it improves our understanding of rhabdovirus ecology and evolution, shedding new light on these important viruses and the diseases they cause.

Impact of anthropogenic sounds (pile driving, drilling and vessels) on the development of model species involved in marine biofouling

The uncontrolled colonization of benthic organisms on submerged surfaces, also called biofouling, causes severe damage in the shipping and aquaculture industries. Biofouling starts with a benthic biofilm composed of a complex assemblage of microbes, bacteria and benthic diatoms, called microfouling, on which macrofouling invertebrate species settle and grow. Invertebrate larvae may use natural soundscapes to orientate inshore and choose their optimal habitat. Recent studies have demonstrated that ship sounds enhance the larval settlement and growth of several invertebrate species, such as mussels, associated with biofouling. Among invertebrates, effects of sound generated by offshore human activities are still poorly studied. This study aims to assess the effect of pile driving, drilling and vessel sounds on model species associated with micro and macrofouling. First, the biofilm development of Navicula pelliculosa and Amphora coffeaeformis was assessed, then, the larval development of the blue mussel (Mytilus edulis) was evaluated from the D-veliger to the postlarval stage. Mussel larvae and microalgae were exposed 12 h each day in tanks (Larvosonic) adapted to sound experiments under controlled conditions. All anthropogenic sounds induced a thinner N. pelliculosa biofilm coupled with a lower microalgae concentration. The drilling sound had a stronger effect on the biofilm thickness. The drilling sound significantly reduced the pediveliger settlement and the postlarvae clearance rate by 70.4% and tended to diminish settler sizes compared to control sound. Contrary to our expectation, pile driving tended to enhance larval recruitment by 22% (P=0.077) and the boat sound did not stimulate larval settlements or recruitment. Drilling sound generated a stressful acoustic environment for pediveliger settlements and postlarvae seem to maintain their shell valves closed to preserve energy. We identify potential causes and mechanisms involved in these impacts of anthropophony on larval ecology and microfouling dynamics.

Analysis of the Elemental Composition of Gonads, Gametes and Larvae of the Mussel <i>Mytilus galloprovincialis</i> in the Spawning Period

In this work, we studied the elemental composition of gonads, eggs, sperm and larvae of the mussel Mytilus galloprovincialis during spawning, when the contents of biologically active compounds and minerals are maximal. A comparative analysis of the contents showed that the elements are involved in the mussel gametogenesis in different pathways. There were significant differences in the contents of Li, B, Mg, Si, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Zn, Ge, As, Se, Br, Rb, Sr, Mo, Pd, Sn, I, Ba and Ce in male and female gonads before and after spawning, gametes and larvae of mussels. It is likely that some of the listed elements are not only passively accumulated in the mollusk body, but are also essential, being directly involved in the reproduction process. Most of significant differences in the element contents were found between eggs and larvae and between male gonads before spawning and sperm. By spawning, mussel gonads accumulated mainly p- and d-elements, apparently due to the ability of their ions to form complexes and, consequently, to be included in the structure of enzymes. The contents of B, Mg, Si, P, K, Ca, Cr, Mn, Fe, Cu, Zn, As, Se, Br, Sr and Ba in male and female gonads, gametes and larvae were an order or several orders of magnitude higher than those of other elements. The contents of Ca, Fe, Sr, Sn and I in mussel larvae were significantly higher than in gonads and gametes. Sn is a technological hydropollutant, and thus, larvae can serve as a bioindicator of the aquatic environment pollution with this element. The data obtained are of practical interest for improving the biotechnology of reproduction of marine hydrobionts and obtaining functional products based on them, which is important for the optimization of aquaculture management and for addressing human health-related issues.

Integrated ozonation as a strategy for enhancing treatment of municipal wastewater in facultative sewage lagoons

Facultative sewage lagoons are widely used to treat domestic wastewater in small and remote communities, but the wastewater discharged is often out of compliance. Novel, affordable and scalable methods are needed to improve the quality of effluent. Ozonation of wastewater in these lagoons to enhance natural treatment may be an effective method. In facultative sewage lagoons operating in two Indigenous communities, we injected ozone into wastewater pumped from the lagoons to treat approximately 15% of the volume and monitored wastewater quality. In the first study, there were significant reductions in total ammonia, cBOD and cBOD/COD. Based on Vibrio fischeri, the toxicity declined post-ozonation, but there was no evidence of a similar decline in toxicity to freshwater mussel (Lampsilis fasciola) larvae (i.e., glochidia). Among 14 contaminants of emerging concern monitored, the concentrations of most compounds declined but the concentrations of others, especially 17a-ethinylestradiol remained stable. In the second study, significant decreases were observed post-ozonation in cBOD, cBOD/COD, total and unionized ammonia, but in this case, the toxicity to V. fischeri did not decline. The parameters in this lagoon were below the regulatory limit for cBOD by 4 weeks after ozonation and below the regulatory limit for unionized ammonia after 6 weeks, which is earlier then the historical dates for reaching compliance in this lagoon. Overall, the results in operational facultative lagoons, for which no comparable data are available at that scale, indicate that ozonation of small volumes of wastewater in lagoons may be an effective method for improving wastewater quality.