Mussel Settlement Research Articles

Antifouling activity and ecotoxicological profile of the cyanobacterial oxadiazine nocuolin A

Pursuing effective and biocompatible natural compounds to supplant current biocidal antifouling (AF) technologies remains crucial and challenging. Among natural products hosts, cyanobacteria are recognized as producers of bioactive secondary metabolites that are underexplored in terms of anti-biofilm and AF potential. Nocuolin A, a natural oxadiazine previously isolated and known to be produced by different cyanobacterial strains, has demonstrated bioactive potential, particularly against tumor cell lines. Considering this potential and its exquisite chemical structure, here nocuolin A was investigated as a potential natural AF agent through an integrative approach including AF bioactivity testing across distinct levels of biological organization, mode of action assessment, ecotoxicity evaluation, and ecological risk predictions. Nocuolin A was found to inhibit the settlement of mussel (Mytilus galloprovincialis) plantigrades (EC50 = 3.905 μM) while showing no toxicity to this biofouling species (LC50 > 100 μM). Additionally, while exhibiting no inhibitory activity against the growth of five marine biofilm-forming bacterial strains, it significantly suppressed the growth of the marine biofilm-forming diatom Navicula sp. (EC50 = 1.561 μM), and had a lethal effect on this diatom species (>3.1 μM). The AF targets of nocuolin A on mussel plantigrades revealed no correlation with acetylcholinesterase and tyrosinase metabolic processes; however, proteins involved in oxidative stress, muscle regulation, and energy production were highlighted. The results also provide insights into the ecological risk of nocuolin A, including its ecotoxicity against Artemia salina nauplii (LC50 = 2.480 μM), Amphibalanus amphitrite nauplii (LC50 = 0.0162 μM), and Danio rerio embryos (LC50 = 0.0584 μM). When matching these results with simulated environmental values, nocuolin A was deemed a considerable threat to the ecosystems. While this research highlights the AF activity of nocuolin A, it also emphasizes the potential adverse environmental impact when applied in preventive coatings.

Ecosystem engineers enhance the multifunctionality of an urban novel ecosystem: Population persistence and ecosystem resilience since the 1980s

In degraded urban habitats, nature-based solutions aim to enhance ecosystem functioning and service provision. Bivalves are increasingly reintroduced to urban environments to enhance water quality through biofiltration, yet their long-term sustainability remains uncertain. Following the restoration of the disused South Docks in Liverpool in the 1980s, natural colonization of mussels rapidly improved dock-basin water quality and supported diverse taxa, including other filter feeders. While the initial colonization phase has been well documented, there has been limited published research since the mid-1990s, despite ongoing routine water quality monitoring. Here, we assessed the long-term persistence of mussel populations, their associated biodiversity, and physico-chemical parameters of the water in Queens and Albert Docks by comparing historical (1980s to 1990s) and contemporary data from follow-up surveys (2012,2022). Following an initial period of poor water quality (high contamination and turbidity, low oxygen), the natural colonization of mussels from Albert Dock in 1988 extended throughout the South Docks. By the mid-1990s, the environment of the South Docks and its mussel populations had stabilized. The dock walls were dominated by mussels which provided important complex secondary substrate for invertebrates and macroalgae. Surveys conducted in 2012 and 2022 confirmed the continued dominance of mussels and estimates of mussel biofiltration rates confirm that mussels are continuing to contribute to maintaining water quality. A decline in salinity was observed in both docks in 2022, with evidence of recovery. While these ecosystems appear relatively stable, careful management of the hydrological regime is crucial to ensuring the persistence of mussels and resilient ecosystem service provision through biofiltration.

Efficiency of different collectors for spat settlement of Mediterranean mussel (Mytilus galloprovincialis) in the southeastern Marmara Sea, Türkiye

ABSTRACT Mediterranean mussel have spread almost throughout Turkish seas. The objective of this study was to set up longline systems to determine spat efficiency by two different systems (buoy and pipe) consisting of three different materials, new rope, used rope and used net, in Erdek Bay. The second objective was to identify whether waste materials could be used in mussel culture. Sea water temperature, salinity, dissolved oxygen, chlorophyll-a, total suspended, inorganic and organic matter were measured at monthly intervals. Results revealed that the highest settlement (4196 spat) was observed in the collectors made of used nets in the pipe system (October 2016). In contrast, the lowest value (2 spat) was recorded from the collectors made of new ropes in the buoy system (August 2016). Waste materials presented relatively better results on settlement than the new ropes. The optimum production was observed in the mussel farm with 1239 spat in the buoy and 1607 spat in the pipe systems, which were commissioned in April 2016. It is concluded that the spat performance was affected by collectors and materials. Therefore, we propose the use of used ropes and used nets, which will allow more effective attachment surfaces to achieve higher spacing settlement.

Seasonal and synoptic spatio-temporal variability on larval delivery mechanisms inferred from mussel settlement patterns in the Portuguese coast

Demographic connectivity is the process by which population persistence and growth are affected by the dispersal of individuals. In sessile marine species that disperse by planktonic larvae and form metapopulations, the interaction between oceanographic forcing and larval biology drives the spatial extent and magnitude of larval delivery to suitable habitat patches. The present study investigates the supply of Mytilus galloprovincialis larvae to rocky intertidal habitats located within and around two marine protected areas (MPA) in central Portugal, one located on the exposed coast and the other one in a sheltered bay, using time series of settlement intensity and oceanographic variables. The results indicate that larval delivery at short time scales (days) is strongly dependent on the interaction of upwelling circulation with coastline topography. In the exposed MPA, located on a coastal island, the magnitude of mussel larval delivery is limited by the dynamics of an upwelling front and filament that intercepts the island as upwelling increases and decreases. In the sheltered bay, under an upwelling shadow, the upwelling front promotes recirculation of the water mass, intensifying larval retention and settlement. The results are also consistent with larval transport distances of tens of kilometres and ongoing connectivity between the two MPA. This study highlights the relevance of coastal topography and its interaction with mesoscale hydrodynamics in the modulation of larval delivery, crucial for the persistence of populations and communities and in systematic conservation planning.

Assessing Zebra Mussels’ Impact on Fishway Efficiency: McNary Lock and Dam Case Study

The Columbia River Basin faces a threat from the potential invasion of zebra mussels (Dreissena polymorpha), notorious for their ability to attach to various substrates, including concrete, which is common in fishway construction. Extensive mussel colonization within fishways may affect fish passage by altering flow patterns or creating physical barriers, leading to increased travel times, or potentially preventing passage altogether. Many factors affect mussel habitat suitability including vectors of dispersal, water parameters, and various hydrodynamic quantities, such as water depth, velocity, and turbulence. The objective of this study is to assess the potential for zebra mussels to attach to fishway surfaces and form colonies in the McNary Lock and Dam Oregon-shore fishway and evaluate the potential impact of this infestation on the fishway’s efficiency. A computational fluid dynamics (CFD) model of the McNary Oregon-shore fishway was developed using the open-source code OpenFOAM, with the two-phase solver interFoam. Mesh quality is critical to obtain a reliable solution, so the numerical mesh was refined near the free surface and all solid surfaces to properly capture the complex flow patterns and free surface location. The simulation results for the 6-year average flow rate showed good agreement with the measured water column depth over each weir. Regions susceptible to mussel infestation were identified, and an analysis was performed to determine the mussel’s preference to colonize as a function of the depth-averaged velocity, water depth, and wall shear stress. Habitat suitability criteria were applied to the output of the hydraulic variables from the CFD solution and provided insight into the potential impact on the fishway efficiency. Details on the mesh construction, model setup, and numerical results are presented and discussed.

Inhibition of mussel settlement by calcined mussel shell powder through altering biofilms and bacterial community

Sustainability-driven innovations with non-toxic coating developing is essential. Here, we utilized the waste mussel shells as an alternative antifouling coating to test the potential impacts on biofilm formation and then Mytilus coruscus settlement. Compared with Natural Mussel Shell Powder (NMSP), the bacterial density of biofilm on 10 mg/mL Calcined Mussel Shell Powder (CMSP) coating was 63.09%, lowered significantly (p < 0.05). Further analysis of X-ray diffraction test showed the phase transformation appeared in the CMSP in comparison to NMSP. The biofilm bioassays showed that in 28-day-old natural biofilm, compared with Glass and PDMS, the bacterial density in 10 mg/mL CMSP decreased by 46.58 % and 34.60 %, respectively, and the diatom density decreased by 71.07 % and 42.99 %, respectively. Compared to Glass and PDMS, the relative abundance of Psychrobacter and Loktanella in the 28-day-old biofilms on CMSP coating was reduced, but that of Erythrobacter increased. Simultaneously, settlement on 10 mg/mL CMSP was reduced by 65.31 % and 72.13 %, respectively, compared to PDMS and Glass in the case of 28-day-old biofilms. These results demonstrate the viability of CMSP as a coating and provide a sustainable solution to against marine biofouling.

Sulfated phenolic polymers as non-toxic antifouling agents

Nature-inspired highly sulfated bioactive polyphenols are recently emerging as antifouling agents with low or non-toxic effects to the environment representing a valuable alternative to the most used harmful biocides. In this frame, we report herein the preparation of sulfated derivatives of two phenolic polymers of tyrosol and gallic acid previously obtained via a convenient horseradish peroxidase/H2O2-catalyzed oxidation process. A mild sulfation procedure based on the use of sulfur trioxide triethylamine complex under microwave irradiation afforded the corresponding sulfated polymers OligoTyrS and OligoGallS in good yields (90–95 % w/w). Elemental analysis, FT-IR and MALDI-MS investigation provided evidence for an almost complete sulfation of the –OH groups. In line with a high degree of sulfation, OligoTyrS and OligoGallS exhibited lower antioxidant properties compared to the non-sulfated polymers as evaluated by the 2,2-diphenyl-1-picrylhydrazyl and ferric reducing/antioxidant power assays. In contrast to the non-sulfated polymers, OligoTyrS and OligoGallS showed a significant inhibitory effect against the settlement of mussel (Mytilus galloprovincialis) plantigrade without lethality effects and without affecting the selected biofilm-forming organisms like five marine bacteria and a diatom. Both sulfated polymers were also found to be non-toxic to the non-target species Artemia salina. The overall results presented herein put forward the potential of non-natural sulfated phenolic polymers as new non-toxic antifouling agents.

Western Lake Erie Quagga Mussel growth estimates and evidence of barriers to local population growth

Abstract Invasive Quagga Mussels (Dreissena rostriformis bugensis) and Zebra Mussels (D. polymorpha) have been present in the Great Lakes for almost four decades and have caused substantial economic and environmental impacts. Factors that influence dreissenid mussel growth and population dynamics warrant more study, particularly for Quagga Mussels. We conducted a five-month field experiment in western Lake Erie to measure multiple growth metrics for Quagga Mussels at two sites with different conditions using mussels contained in cages on instrumented moorings. We also quantified dreissenid mussels that colonized into the cages and surveyed dreissenid mussels in the sediments at each site. By multiple measures of growth except for one, growth rates were similar between the two sites despite different chlorophyll a and turbidity levels as well as notable differences in the density and size distribution of mussels found in the sediments at these sites. The growth rates were approximately 0.03 mm d-1 for 12-mm Quagga Mussels and these rates declined with increasing initial shell length. Specific growth rate did not differ between shell and tissue measures or between sites, but both shell and tissue specific growth rates were much higher for smaller mussels. Site WE2, which is closer to Maumee River, had very few dreissenid mussels present in the sediments surrounding the mooring despite having a potential for growth comparable to that at WE4. The high level of colonization on the mooring at WE2 indicated that conditions at the sediment surface inhibit mussel settlement; adjacent benthic surveys indicated that very few mussels survive beyond the juvenile stage. Ultimately, the results from this study provide useful mussel growth parameters and indicate substrate or other limitations for dreissenid mussel populations in western Lake Erie.

Transparent amphiphilic silicone-based fouling-release coatings: Analyzing the effect on coating-fouling interfacial behavior

The amphiphilic antifouling coatings are effective for inhibiting fouling adhesion. Herein, the amphiphilic coatings were prepared by introducing polyether-modified polydimethylsiloxane (PE-PDMS). Uniform morphology, high transmittance, low surface roughness and amphiphilic property were obtained. PE-PDMS appearing as interspersed chains endowed the coating with amphiphilic characteristic. The artificial seawater promoted the migration of polyether to the surface. The protein adhesion force and quality were significantly reduced according to AFM-based colloidal probe technique and Quartz Crystal Microbalance with Dissipation, respectively. The coating exhibited antibacterial activity against Pseudoalteromonas xiamenensis (84.0%), Escherichia coli (69.2%) and Staphylococcus aureus (63.0%), respectively. 63.1% Halamphora. sp and 75.8% Nitzschia closterium f. had been inhibited, while the coatings possessed outstanding fouling release property with above 76.1% diatom detached after water exposure, proving that the amphiphilic parts weakened the adhesion of fouling. The mussel settlement assay confirmed that less adhesive plaques existed over the amphiphilic coatings. In addition, the expression for mussel adhesion proteins (mfp-5 and mfp-6) were significantly increased, demonstrating that amphiphilic polymers interfered with the adhesion response of the mussels. The effect on the interfacial behavior between fouling and coating is explored, providing a meaningful issue for the development of environmentally friendly antifouling coatings.

Temporal and small-scale spatial variation in spatfall of the mussel Mytilus edulis platensis: Basis for culture management at San Jorge Gulf, Patagonia Argentina

Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success.

Settlement of the Tropical Box Mussel, Septifer bilocularis: Effects of Site, Position, and Substratum

The box tropical mussel Septifer bilocularis lives attached to a hard substratum, forming a dense aggregation or patch. The aggregation occurs at the time of larvae settlement in response to different cues. Larvae may have a positive response whereas larvae may settle and attach to the substratum, while in a negative response, postpone settling occurs. Byssus threads are produced and attached to the substratum, and for some reason, they are affected by many variables. We studied whether the attachment was affected by sites, position in the patch, and substratum. Large and small patches of mussel beds were selected arbitrarily, each in 3 replicates. Substrata of palm, coconut, polypropylene fibres, and mussel shells with byssus threads, each in 4 replicates, were distributed randomly into a PVC plate with 16 holes. The PVC plates with experimental substrata were placed along the edge and in the middle of large and small patches. A three-factorial ANOVA was then performed on samples of sites, position in patches, and substratum as main effects. A significant effect of sites, position within patches, and substratum as well were found. A significantly high number of new settlers in small patches than in other positions within patches occurred. The larger number of new settlers was found on coconut, palm, and polypropylene fibres, while low numbers on the mussel shells with byssus threads were found. The new settlers of S. bilocularis (&lt;1 mm) with transparent shells were observed attached to coconut, palm, and polypropylene fibres. In contrast, the new settlers ranged from &gt;1 mm to 3 mm with dark green shells attached to mussel shells with byssus threads. This study suggests that early settlement occurs when mussels’ larvae first settle and attach to coconut, palm, and polypropylene fibres before reattaching to adult shells with byssus threads.

Veliger density and environmental conditions control quagga mussel colonization rates in two perialpine lakes

Quagga and zebra mussels (Dreissena bugensis and D. polymorpha) are spreading across lakes in Europe and North America. In particular, quagga mussels colonize lakes to great depths (>200 m). To better understand the colonization pattern of quagga mussels in deep lakes, we studied the settlement of quagga mussels along a depth gradient on colonization plates at multiple depths (1–140 m) in the pelagic zone of two recently invaded perialpine lakes, Lake Constance and Lake Geneva. We measured colonization rates every three months over one year on colonization plates deployed in both lakes at defined depths. We also assessed long-term population dynamics from abundance and size distribution using repeated photogrammetry of colonization plates. Highest colonization rates and largest mussel sizes occurred above 8 m depth, and almost no zebra mussels were found. Colonization rates decreased to almost zero below 30 m. Colonization rates on plates were associated with variation in environmental conditions as well as veliger densities in the plankton across season and depth. Temperature was the most important environmental parameter that influenced colonization. Our results will help to better understand the seasonal colonization patterns of invasive quagga mussels in deep lakes.

3,4-Dioxygenated xanthones as antifouling additives for marine coatings: in silico studies, seawater solubility, degradability, leaching, and antifouling performance

Marine biofouling pollution is a process that impacts ecosystems and the global economy. On the other hand, traditional antifouling (AF) marine coatings release persistent and toxic biocides that accumulate in sediments and aquatic organisms. To understand the putative impact on marine ecosystems of recently described and patented AF xanthones (xanthones 1 and 2), able to inhibit mussel settlement without acting as biocides, several in silico environmental fate predictions (bioaccumulation, biodegradation, and soil absorption) were calculated in this work. Subsequently, a degradation assay using treated seawater at different temperatures and light exposures was conducted for a period of 2 months to calculate their half-life (DT50). Xanthone 2 was found to be non-persistent (DT50 < 60 days) at 50 μM, contrary to xanthone 1 (DT50 > 60 days). To evaluate the efficacy of both xanthones as AF agents, they were blended into four polymeric-based coating systems: polyurethane- and polydimethylsiloxane (PDMS)-based marine paints, as well as room-temperature-vulcanizing PDMS- and acrylic-based coatings. Despite their low water solubility, xanthones 1 and 2 demonstrated suitable leaching behaviors after 45 days. Overall, the generated xanthone-based coatings were able to decrease the attachment of the Mytilus galloprovincialis larvae after 40 h. This proof-of-concept and environmental impact evaluation will contribute to the search for truly environmental-friendly AF alternatives.

Outer membrane vesicles induce the mussel plantigrade settlement via regulation of c-di-GMP

Despite the importance of outer membrane vesicles (OMVs) in benthic animal settlement, the underlying molecular mechanism remains elusive. Here, the impact of OMVs and OMVs synthesis-related tolB gene in Mytilus coruscus plantigrade settlement was tested. The OMVs were extracted from Pseudoalteromonas marina through density gradient centrifugation, and a tolB knockout strain, achieved by homologous recombination, was utilized for the investigation. Our results demonstrated that OMVs could significantly enhance M. coruscus plantigrades settlement. Deleting the tolB resulted in downregulation of c-di-GMP, accompanied by a reduction of OMV production, a decline in bacterial motility and increasing biofilm-forming ability. Enzyme treatment resulted in a 61.11% reduction in OMV-inducing activity and a 94.87% reduction in LPS content. Thus, OMVs regulate mussel settlement via LPS, and c-di-GMP is responsible for the OMV-inducing capacity. These findings provide new insights into the interactions between bacteria and mussels.

Two-Component System Response Regulator ompR Regulates Mussel Settlement through Exopolysaccharides.

The outer membrane protein (OMP) is a kind of biofilm matrix component that widely exists in Gram-negative bacteria. However, the mechanism of OMP involved in the settlement of molluscs is still unclear. In this study, the mussel Mytilus coruscus was selected as a model to explore the function of ompR, a two-component system response regulator, on Pseudoalteromonas marina biofilm-forming capacity and the mussel settlement. The motility of the ΔompR strain was increased, the biofilm-forming capacity was decreased, and the inducing activity of the ΔompR biofilms in plantigrades decreased significantly (p < 0.05). The extracellular α-polysaccharide and β-polysaccharide of the ΔompR strain decreased by 57.27% and 62.63%, respectively. The inactivation of the ompR gene decreased the ompW gene expression and had no impact on envZ expression or c-di-GMP levels. Adding recombinant OmpW protein caused the recovery of biofilm-inducing activities, accompanied by the upregulation of exopolysaccharides. The findings deepen the understanding of the regulatory mechanism of bacterial two-component systems and the settlement of benthic animals.

Mussel settlement mediated by bacterial VgrG proteins via extracellular outer membrane vesicles

T6SS plays an important role in biofilm formation, but how bacterial T6SS regulates biofilm formation and its effect on marine invertebrate settlement is still unclear. Here, the role of T6SS spike protein VgrG and VgrG protein synthesis gene on biofilm formation and Mytilus coruscus settlement was examined. Deletion of the core gene vgrG of T6SS resulted in a decrease in the growth capability of Leisingera aquaemixtae and inhibition of the ability of biofilm formation. The OMV content and inducing activity of ΔvgrG biofilms were decreased respectively by 20.72% and 59.70% compared with the wild-type biofilms. OMVs induced the settlement of M. coruscus, while VgrG proteins did not induce mussel settlement directly. Addition of VgrG proteins resulted in the upregulation of OMVs in the ΔvgrG biofilms. Adding OMVs caused no increasing inducing activity of ΔvgrG biofilms. Interestingly, the inducing activity of ΔvgrG biofilms both by adding VgrG proteins alone, and by adding VgrG proteins and OMVs in combination increased significantly, and restored to the inducing capability of wild-type biofilms. Thus, bacterial T6SS spike protein VgrG could mediate mussel settlement by increasing the OMV content of biofilms. The present findings shed new light on the interaction between T6SS and marine invertebrate settlement.

TRPM7-Mediated Ca2+ Regulates Mussel Settlement through the CaMKKβ-AMPK-SGF1 Pathway.

Many marine invertebrates have planktonic larval and benthic juvenile/adult stages. When the planktonic larvae are fully developed, they must find a favorable site to settle and metamorphose into benthic juveniles. This transition from a planktonic to a benthic mode of life is a complex behavioral process involving substrate searching and exploration. Although the mechanosensitive receptor in the tactile sensor has been implicated in sensing and responding to surfaces of the substrates, few have been unambiguously identified. Recently, we identified that the mechanosensitive transient receptor potential melastatin-subfamily member 7 (TRPM7) channel, highly expressed in the larval foot of the mussel Mytilospsis sallei, was involved in substrate exploration for settlement. Here, we show that the TRPM7-mediated Ca2+ signal was involved in triggering the larval settlement of M. sallei through the calmodulin-dependent protein kinase kinase β/AMP-activated protein kinase/silk gland factor 1 (CaMKKβ-AMPK-SGF1) pathway. It was found that M. sallei larvae preferred the stiff surfaces for settlement, on which TRPM7, CaMKKβ, AMPK, and SGF1 were highly expressed. These findings will help us to better understand the molecular mechanisms of larval settlement in marine invertebrates, and will provide insights into the potential targets for developing environmentally friendly antifouling coatings for fouling organisms.

Larval settlement and metamorphosis of Mytilus coruscus in response to varying bacterial capsular polysaccharide

Marine invertebrates are the backbone of marine biodiversity and play a pivotal role in the marine ecosystem. The life cycle of most marine invertebrates includes the settlement and metamorphosis stage, which is induced by marine biofilms, but the mechanism is still enigmatic. In the present study, we constructed the capsular polysaccharide (CPS) synthesis gene capC-deleted mutant of Pseudoalteromonas marina by gene knockout and then compared the phenotype, the biofilm-forming ability, the effect on settlement and metamorphosis of Mytilus coruscus, and the exopolysaccharide and CPS levels between the mutant and the wild-type strains to explicate the relationship between bacteria and mussels. The study presented that the phenotype and biofilm-forming ability between the wild-type and ΔcapC strains had no significant difference, but the inducing activity of ΔcapC biofilms on larval settlement and metamorphosis decreased significantly (p &amp;lt; 0.05). Compared with the wild-type, the CPS content of ΔcapC strain significantly decreased by 38.07%, accompanied by the increase of c-di-GMP. Meanwhile, the biomass of α-polysaccharides and β-polysaccharides on ΔcapC biofilms decreased significantly (p &amp;lt; 0.05). Thus, the CPS synthesis gene could modulate c-di-GMP, which regulates bacterial polysaccharide secretion, and then impact larval settlement and metamorphosis of mussels. This work brings an entry point to deeply understand the interaction between bacterial polysaccharide and larval recruitment.

Constructing micro-dynamic surface of boron-polyurethane with endurable anti-fouling properties

Self-polishing coatings (SPC) with renewable surfaces are widely used in the shipping industry and offshore installations to prevent unexpected costs and safety concerns from marine biofouling. However, self-polishing coatings still suffer from uncontrollable release of antifouling biocides which is called “initial burst and final decay” and poor mechanical properties. Herein, a series of controlled-release boron-polyurethane antifouling coatings (DBIT) were prepared with good mechanical properties and micro-dynamic surface. 2, 2-bis(hydroxymethyl)propionic acid (DMPA) and pyridine-diphenylborane (PDB) were used as reaction sites and antifouling functional side chain groups, respectively, which endowing the coatings with the controlled release ability and good performance. The results showed that the DBIT coatings had certain mechanical properties, up to an ultimate stress of 14.8 MPa. The DBIT75 coating could reduce 90.6 % settlement of Halamphora sp., 92.7 % settlement of Nitzschia closterium, and repel the settlement of mussels. More importantly, DBITx coatings displayed excellent antifouling performance for at least 4 months in the field test, which shows that the controlled-release polyurethane coatings provide a new choice for marine antifouling applications.

Impact of golden mussel (Limnoperna fortunei) colonization on bacterial communities and potential risk to water quality

Mussel colonization can affect the water quality through restructuring nearby bacterial communities. In this study, we conducted an experiment to detect the bacterial alteration associated with live and dead golden mussel colonies, and used a high-throughput sequencing method based on 16S rRNA genes to reveal the changes in bacterial communities. It is revealed that these bacterial assemblages consumed nutrients and/or tissues of the mussels and produced metabolites, resulting in poor water quality and low bacterial alpha-diversities, particularly in dead mussel groups. The dissimilarity of bacterial community among the live and dead mussel groups was more significant than that among the different initial water qualities, indicating that mussel colonization and living status dominates the bacterial community. Co-occurrence network analysis revealed that the bacterial community associated with live mussel colonies exhibited more intensive interactions compared to that associated with dead ones. Furthermore, phenotype prediction indicated that mussel colonies, especially the dead mussel colonies, promoted the growth of pathogenic bacteria. Amino acid metabolism and carbohydrate metabolism were dominant pathways relevant to metabolism, leading to off-odors and the production of toxic compounds. The effect of these processes on water quality suggests that mussels that might be killed in water diversion projects should be removed promptly to avoid impacts on water quality.