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A correction notice to the article, "Comparative omics analysis of a deep-sea barnacle species (Cirripedia, Scalpellomorpha) and shallow-water barnacle species provides insights into deep-sea adaptation," published in the previous issue of the periodical.

Barnacles have demonstrated adaptability to a range of habitats, spanning from shallow water to the deep sea. Given the harsh conditions present in hydrothermal vents, hydrothermal vent barnacles serve as the model organism for investigating the interplay between evolution and adaptability. In order to gain insights into barnacle adaptive characteristics, particularly within hydrothermal vents, we conducted a comprehensive analysis of the mitogenomes and transcriptome in a deep-sea barnacle (Neolepas marisindica), in comparison to its shallow-water related species. The mitogenomes with the same genetic skews and the non-synonymous/synonymous mutation ratios (Ka/Ks) of the mitogenomes indicate that the protein-coding genes (COIII, ND2, and ND6) of N. marisindica are under positive selection. Meanwhile, the functional annotation shows that distinctly positive selected orthologs in N. marisindica are predominately related to neural signal transduction, immunity, antiapoptotic, and energy metabolism. These results indicate that the mitogenomes and key genes found in transcriptomic analysis are under high-temperature and highpressure conditions, and which may contribute N. marisindica to have evolved to adapt to the extreme hydrothermal vent environments. The findings shed light on the mitogenome and transcriptome of N. marisindica, which lays a foundation for the in-depth understanding of the adaptation mechanism of sessile invertebrates to the deep-sea environment. [ABSTRACT FROM AUTHOR]

With the ongoing climate and oceanographic change, an increasing number of studies are reporting dramatic population losses caused by thermal extremes in intertidal habitats. Under moderate warming, however, populations can fare better in places where species normally experienced suboptimal temperatures. This article reports the massive recruitment of the barnacle Semibalanus balanoides on the Gulf of St. Lawrence coast of Nova Scotia (Canada) in 2024. As recruits appear mostly during May in this region, coastal sea surface temperature (SST) in April is critical for the ecological performance of larvae, as they are pelagic and live in the water column for weeks before intertidal settlement. Thus, a study that spanned 12 years (2005 to 2016) on this coast found that annual barnacle recruitment was positively correlated to April SST. In April 2024, coastal SST was 116% higher than for the same month averaged over those 12 years (4.1 vs. 1.9 °C). This SST spike was followed by an elevated recruitment that was 111% higher than the average for those 12 years (1,278 vs. 607 recruits dm−2). Overall for the studied years, the amount of variation in annual barnacle recruitment statistically explained by April SST was 51%. While the southern distribution limit of S. balanoides has moved northwards in recent decades due to lethal warming, our results support the notion of improving reproductive success with seawater warming on colder northern shores. [ABSTRACT FROM AUTHOR]

Hydrogels are promising materials for wound protection, but in wet, or underwater environments, the hydration layer and swelling of hydrogels can seriously reduce adhesion and limit their application. In this study, inspired by the structural characteristics of strong barnacle wet adhesion and combined with solvent exchange, a robust wet adhesive hydrogel (CP-Gel) based on chitosan and 2-phenoxyethyl acrylate was obtained by breaking the hydration layer and resisting swelling. As a result, CP-Gel exhibited strong wet adhesion to various interfaces even underwater, adapted to joint movement and skin twisting, resisted sustained rushing water, and sealed damaged organs. More importantly, on-demand detachment and controllable adhesion were achieved by promoting swelling. In addition, CP-Gel with good biosafety significantly promotes seawater-immersed wound healing and is promising for use in water-contact wound care, organ sealing, and marine emergency rescue.

Background: Plastic pollution is a significant issue on the East Coast of Surabaya, emphasizing the need to develop microplastic monitoring programs. Barnacles became one of the potential microplastic bioindicator species on the East Coast of Surabaya. This study aimed to characterize the visual and polymers of microplastics found in barnacles and assess their potential as a bioindicator species for microplastic pollution on the East Coast of Surabaya. Methods: Microplastic polymer analysis was performed using ATR-FTIR. Results: A total of 196 microplastic particles were found in barnacles, water, and sediment. The size of microplastics in barnacles, water, and sediment varied, with the size in barnacles dominated by class 1 (1–10 µm), in water by class 2 (10–50 µm), and in sediments by class 3 (50–100 µm). Fragments dominated the shape of microplastics in barnacles, while water and sediment were dominated by fiber. The microplastic color in barnacles, water, and sediment was dominated by blue, and the microplastic polymer composition on barnacles, water, and sediments was dominated by cellophane (36%). Amphibalanus amphitrite was found to be predominant and identified as a potential microplastic bioindicator because it is a cosmopolitan species. Its population was found to correlate positively with cellophane (CP) accumulation. The Pearson's correlation test between barnacle length and microplastic length at a = 0.05 was inversely proportional to r = − 0.411 (p < 0.05), categorized as a strong enough correlation. These findings are essential in developing monitoring programs and mitigating the impact of microplastics on the marine environment. [ABSTRACT FROM AUTHOR]

With the ongoing climate and oceanographic change, an increasing number of studies are reporting dramatic population losses caused by thermal extremes in intertidal habitats. Under moderate warming, however, populations can fare better in places where species normally experienced suboptimal temperatures. This article reports the massive recruitment of the barnacle Semibalanus balanoides on the Gulf of St. Lawrence coast of Nova Scotia (Canada) in 2024. As recruits appear mostly during May in this region, coastal sea surface temperature (SST) in April is critical for the ecological performance of larvae, as they are pelagic and live in the water column for weeks before intertidal settlement. Thus, a study that spanned 12 years (2005 to 2016) on this coast found that annual barnacle recruitment was positively correlated to April SST. In April 2024, coastal SST was 116% higher than for the same month averaged over those 12 years (4.1 vs. 1.9 °C). This SST spike was followed by an elevated recruitment that was 111% higher than the average for those 12 years (1,278 vs. 607 recruits dm−2). Overall for the studied years, the amount of variation in annual barnacle recruitment statistically explained by April SST was 51%. While the southern distribution limit of S. balanoides has moved northwards in recent decades due to lethal warming, our results support the notion of improving reproductive success with seawater warming on colder northern shores.

Polychlorinated Biphenyls (PCBs) are mutagenic, carcinogenic, and persistent organic pollutants of the marine and coastal environment. No previous research has precisely used barnacles as potential PCBs bioindicators in the Caspian sea. The present survey was done to add the PCBs concentrations amongst the barnacle and sediment samples collected from 5 important Iranian ports besides the Caspian sea. Barnacle and sediment samples were collected from Astara, Anzali, Caspian, Kiashahr, and Chamkhaleh ports. Samples were transferred to the laboratory and analyzed for the presence and concentration of PCBs using GC-MS. Eighty different types of PCB were detected in the examined samples. PCBs concentration ranged from 02.00±00.10 to 53.00±00.60 ng/g. PCB-77 (53.00±00.60 ng/g in Chamkhaleh, 53.00±01.20 ng/g in Caspian, 53.00±02.40 ng/g in Anzali, and 53.00±2.7 ng/g in Astara ports) had the highest concentration in barnacle samples. PCB-52 (53.00±00.70 ng/g in Chamkhaleh port) had the highest concentration in sediment samples. PCB-114 had the lowest concentration amongst the barnacle (02.00±00.10 ng/g in Astara port) and sediment (03.00±00.20 ng/g in Anzali port) samples. This study is the first report evaluating the presence and concentration of PCBs in barnacle in the Caspian Sea. The role of barnacles and sediments as biomonitors of PCBs was determined. It seems necessary to set strict rules to prevent pollutants from entering the Caspian Sea. [ABSTRACT FROM AUTHOR]

Background Plastic pollution is a significant issue on the East Coast of Surabaya, emphasizing the need to develop microplastic monitoring programs. Barnacles became one of the potential microplastic bioindicator species on the East Coast of Surabaya. This study aimed to characterize the visual and polymers of microplastics found in barnacles and assess their potential as a bioindicator species for microplastic pollution on the East Coast of Surabaya. Methods Microplastic polymer analysis was performed using ATR-FTIR. Results A total of 196 microplastic particles were found in barnacles, water, and sediment. The size of microplastics in barnacles, water, and sediment varied, with the size in barnacles dominated by class 1 (1–10 µm), in water by class 2 (10–50 µm), and in sediments by class 3 (50–100 µm). Fragments dominated the shape of microplastics in barnacles, while water and sediment were dominated by fiber. The microplastic color in barnacles, water, and sediment was dominated by blue, and the microplastic polymer composition on barnacles, water, and sediments was dominated by cellophane (36%). Amphibalanus amphitrite was found to be predominant and identified as a potential microplastic bioindicator because it is a cosmopolitan species. Its population was found to correlate positively with cellophane (CP) accumulation. The Pearson’s correlation test between barnacle length and microplastic length at a = 0.05 was inversely proportional to r = − 0.411 (p

Barnacles have demonstrated adaptability to a range of habitats, spanning from shallow water to the deep sea. Given the harsh conditions present in hydrothermal vents, hydrothermal vent barnacles serve as the model organism for investigating the interplay between evolution and adaptability. In order to gain insights into barnacle adaptive characteristics, particularly within hydrothermal vents, we conducted a comprehensive analysis of the mitogenomes and transcriptome in a deep-sea barnacle (Vulcanolepas fijiensis), in comparison to its shallow-water related species. The mitogenomes with the same genetic skews and the non-synonymous/synonymous mutation ratios (Ka/Ks) of the mitogenomes indicate that the protein-coding genes (COIII, ND2, and ND6) of V. fijiensis are under positive selection. Meanwhile, the functional annotation shows that distinctly positive selected orthologs in V. fijiensis are predominately related to neural signal transduction, immunity, antiapoptotic, and energy metabolism. These results indicate that the mitogenomes and key genes found in transcriptomic analysis are under high-temperature and high-pressure conditions, and which may contribute V. fijiensis to have evolved to adapt to the extreme hydrothermal vent environments. The findings shed light on the mitogenome and transcriptome of V. fijiensis, which lays a foundation for the indepth understanding of the adaptation mechanism of sessile invertebrates to the deep-sea environment. [ABSTRACT FROM AUTHOR]

Coastal seagrass habitats are critical foraging grounds for endangered green turtles (Chelonia mydas). However, these habitats are vulnerable to anthropogenic effects, potentially leading to their degradation with consequent impacts on the health status of foraging green turtles.Two foraging habitats of green turtles in Tun Mustapha Park, Sabah, Malaysia were surveyed: Kudat Mainland and Balambangan Island, by capturing green turtles and evaluating their physical body condition as well as assessing seagrass cover.Despite having similar genetic compositions, the Kudat Mainland aggregation had significantly higher body size (curved carapace length: 61.7 ± 14.5 cm, body weight: 30.0 ± 22.2 kg), Fulton's body condition index (BCI: 1.49 ± 0.13), barnacle (Chelonibia testudinaria) occurrence (78.8%) and barnacle abundance (5.46 ± 9.90 barnacles/turtle) than the Balambangan Island aggregation (curved carapace length: 51.6 ± 8.1 cm, body weight: 17.3 ± 7.7 kg, BCI: 1.40 ± 0.09, barnacle occurrence: 31.0%, barnacle abundance: 0.50 ± 0.92 barnacles/turtle). The differences in BCI between the nearby aggregations could not be attributed to size and barnacle occurrence differences, suggesting the foraging habitat is the primary factor affecting the body condition of green turtles.Seagrass cover at Kudat Mainland was only slightly higher than at Balambangan Island. These findings suggest that the body condition of green turtles is potentially sensitive to the quality of foraging habitats such as nutrients and water quality.It is crucial to monitor the health of foraging habitats and their impact on the body condition of turtles. It is recommended that habitat‐turtle dynamics are given conservation priority, in parallel to water quality monitoring – with action taken to reduce pollution if necessary. A holistic approach to turtle conservation is therefore required. [ABSTRACT FROM AUTHOR]

Due to the adverse environmental impacts of toxic heavy metal–based antifoulants, the screening of environmentally friendly antifoulants has become important for the development of marine antifouling technology. Compared with the traditional lengthy and costly screening method, computer-aided drug design (CADD) offers a promising and efficient solution that can accelerate the screening process of green antifoulants. In this study, we selected barnacle chitin synthase (CHS, an important enzyme for barnacle settlement and development) as the target protein for docking screening. Three CHS genes were identified in the barnacle Amphibalanus amphitrite, and their encoded proteins were found to share a conserved glycosyltransferase domain. Molecular docking of 31,561 marine natural products with AaCHSs revealed that zoanthamine alkaloids had the best binding affinity (−11.8 to −12.6 kcal/mol) to AaCHSs. Considering that the low abundance of zoanthamine alkaloids in marine organisms would limit their application as antifoulants, a marine fungal–derived natural product, mycoepoxydiene (MED), which has a similar chemical structure to zoanthamine alkaloids and the potential for large-scale production by fermentation, was selected and validated for stable binding to AaCHS2L2 using molecular docking and molecular dynamics simulations. Finally, the efficacy of MED in inhibiting cyprid settlement of A. amphitrite was confirmed by a bioassay that demonstrated an EC50 of 1.97 μg/mL, suggesting its potential as an antifoulant candidate. Our research confirmed the reliability of using AaCHSs as antifouling targets and has provided insights for the efficient discovery of green antifoulants by CADD.

Case studies reporting crustaceans acting as basibionts for a wide range of encrusting invertebrates are widely observed in the literature. For swimming crabs of the genus Callinectes, these commensal interactions are commonly observed in estuaries and coastal zones worldwide. Despite the broad distribution of Callinectes bocourti A. Milne-Edwards, 1879 in Amazon province, the occurrence of epibiosis for this species in the area is rarely reported. Herein, we report the double occurrence of epibiont groups: the mollusks Ostrea puelchana d’Orbigny, 1842 and Sphenia fragilis (H. Adams & A. Adams, 1854) and the barnacles Amphibalanus improvisus (Darwin, 1854) and Chelonibia testudinaria (Linnaeus, 1758) from the new host C. bocourti, collected from the Amazon province, Brazil. The specimens of C. bocourti showing epibionts were collected manually in low tide, with a baited trap called “puçá”, in the region of Curuçá River mouth, state of Pará (0°40’3,705”S, 047°54”43,405”W). We observed five specimens of C. bocourti showing double cases of epibiosis, composed by mollusks and crustaceans sharing the same area. In addition, here, we expand the range extension of the mollusk O. puelchana and we register the presence of the invasive species barnacle A. improvisus from the state of Pará, being this last species, reported as parasite adhered in carapace and branchial chambers of the host.

Barnacles have demonstrated adaptability to a range of habitats, spanning from shallow water to the deep sea. Given the harsh conditions present in hydrothermal vents, hydrothermal vent barnacles serve as the model organism for investigating the interplay between evolution and adaptability. In order to gain insights into barnacle adaptive characteristics, particularly within hydrothermal vents, we conducted a comprehensive analysis of the mitogenomes and transcriptome in a deep-sea barnacle (Neolepas marisindica), in comparison to its shallow-water related species. The mitogenomes with the same genetic skews and the non-synonymous/synonymous mutation ratios (Ka/Ks) of the mitogenomes indicate that the protein-coding genes (COIII, ND2, and ND6) of N. marisindica are under positive selection. Meanwhile, the functional annotation shows that distinctly positive selected orthologs in N. marisindica are predominately related to neural signal transduction, immunity, antiapoptotic, and energy metabolism. These results indicate that the mitogenomes and key genes found in transcriptomic analysis are under high-temperature and high-pressure conditions, and which may contribute N. marisindica to have evolved to adapt to the extreme hydrothermal vent environments. The findings shed light on the mitogenome and transcriptome of N. marisindica, which lays a foundation for the in-depth understanding of the adaptation mechanism of sessile invertebrates to the deep-sea environment.

This study investigated the molecular phylogeny, prevalence, and intensity of infestation by symbiotic barnacle, Chelonibia genus, occurring on blue crab, P. segnis, from the Persian Gulf. More than 237 individual crabs were collected for analysis. Two molecular markers (28S rRNA and COI mtDNA) were applied for species delineation. Two species, Chelonibia patula, and Chelonibia testudinaria, were the first records for both host and location. Female crabs showed higher intensity of infestation with barnacles than the males (p < 0.05). There was a positive correlation between host size and epibiont abundance (p < 0.05), thus the barnacles infested a higher proportion of larger hosts. The results indicate that prevalence of infestation was very severe for C. patula and severe for C. testudinaria. Ovigerous female crabs were the most suitable hosts for barnacles. The molecular taxonomy of the ectosymbiotic crustaceans was confirmed based on sequence similarity and phylogenetic analyses. Based on COI mtDNA topology, C. testudinaria/C. patula from the present study have a sister clade with C. patula, C. testudinaria, C. manati, and C. ceratta from coasts of Japan, Mexico, Taiwan, Southern China, Florida, and Malaysia. [ABSTRACT FROM AUTHOR]

We investigated the influences of oceanographic variables on recruitment patterns of the acorn barnacle Chthamalus malayensis and the rock oyster Saccostrea cuccullata, key space occupiers on tropical intertidal rocky shores. Recruitment data and nearshore environmental variables were obtained at spatial (regional and local) and temporal (monthly) scales on the west coast of Thailand. The relationship between the recruitment of each species and combinations of environmental variables was modeled. The climate of the study sites is influenced by the southwest and northeast monsoons of the Indochinese monsoon system. Observations showed that recruitment of both species and oceanographic variables exhibited differences at either local scale or monthly scale or both. Recruitment of both species was positively related to temperature, while barnacle recruitment was negatively related to salinity, but oyster recruitment was positively related to salinity. Barnacles showed a greater rate of recruitment when south-westerly onshore winds predominated during the southwest monsoon season, while the influence of wind patterns on rock oyster recruitment was not clear. Differential larval delivery regulated by monsoon-driven currents is, therefore, a potential determinant of barnacle recruitment. Our study highlights the roles of monsoon-influenced oceanographic processes as predictors of recruitment patterns of intertidal species in a tropical system. [ABSTRACT FROM AUTHOR]

In this study, Soda Lime Glass (SLG) and Stainless Steel (SS316L) substrata coated with Titanium oxide (TiOx) were tested for their efficacy in the laboratory microcosms and in field against micro- and macrofouling. Laboratory microcosm studies were conducted for five days using natural biofilms, single-species diatom (Navicula sp.), and bacterial biofilms, whereas field observations were conducted for 30 days. The TiOx-coating induced change in the mean contact angle of the substratum and rendered SS316L more hydrophilic and SLG hydrophobic, which influenced the Navicula sp. biofilm, and bacterial community structure of the biofilm. Overall, the TiOx-coated SS316L showed minimal microfouling, whereas non-coated SLG exhibited greater efficacy in deterring/preventing macrofouling organisms. Moreover, the reduction in macrofouling could be attributed to high abundance of Actinobacteria. Unraveling the mechanism of action needs future studies emphasizing biochemical processes and pathways. [ABSTRACT FROM AUTHOR]

In this research, an Underwater Biofouling Panel (UWBFP) system was erected for the qualitative and quantitative estimation of macro fouling organisms in the Gulf of Mannar. Forty-four biofoulers were identified from four types of selected test panels. Among these biofoulers, Amphibalanus amphitrite (Darwin, 1854) was the dominant one. The concrete panel encouraged the highest barnacle density compared to the other panels. Three series of test panels were used to assess the seasonal density of biofouling communities. The overall variation in barnacle count in the seaward and shoreward sides of all these three series were tested. They were found to be significantly different from each other. The greater variations in the barnacle density observed in this study in A-series of test panels could be due to the lack of or absence of other foulers to compete within the fortnight. The Shannon-Wiener species diversity index showed the highest diversity in wood substratum among the three series with greater accumulation of different types of fouling organisms. Multivariate analyses were also performed to understand the seasonal variation as well as the settlement pattern on the different directions of test panels based on validated data. PCA showed a strong variability (PC1 between 70.8% and 98.6% variance) between the directions of the panels in connection with barnacle density. The shade plot and CAP analysis segregated the short-term A-series test panels from the long-term (B- and C-series) test panels. Hence, the output was helpful in understanding the recruitment status of various faunal resources involved in the biofouling processes. [ABSTRACT FROM AUTHOR]

Migration is an integral feature of modern mysticete whale ecology, and the demands of migration may have played a key role in shaping mysticete evolutionary history. Constraining when migration became established and assessing how it has changed through time may yield valuable insight into the evolution of mysticete whales and the oceans in which they lived. However, there are currently few data which directly assess prehistoric mysticete migrations. Here we show that calcite δ18O profiles of two species of modern whale barnacles (coronulids) accurately reflect the known migration routes of their host whales. We then analyze well-preserved fossil coronulids from three different locations along the eastern Pacific coast, finding that δ18O profiles from these fossils exhibit trends and ranges similar to modern specimens. Our results demonstrate that migration is an ancient behavior within the humpback and gray whale lineages and that multiple Pleistocene populations were undertaking migrations of an extent similar to those of the present day.

Some morphometric and biological characteristics of a European spider crab, Maja squinado (Herbst, 1788) caught off Aksaz region, (Biga, Çanakkale, Türkiye) were investigated. In addition, an epizoic species infesting this M. squinado specimen has been identified. The crab specimen was caught by a commercial fisherman using trammel nets. Carapace length, carapace width and weight of the crab were 15.9 cm, 14.5 cm, and 1109 g respectively. The specimen was an ovigerous female with a calculated fecundity of 3.48x104 eggs. Eggs were in stage 4th of development and covered the whole carapace region. Additionaly, it was observed that the specimen was infested with the epixoic barnacle Octolasmis angulata (Aurivillius, 1894). A total of 46 O. angulata individuals were observed; 32 from the gill lamellae, and 14 from the carapace. This study reports the existence of the epizoic O. angulata on Maja squinado for the first time in Türkiye.

Barnacle exhibits high adhesion strength underwater for its glue with coupled adhesion mechanisms, including hydrogen bonding, electrostatic force, and hydrophobic interaction. Inspired by such adhesion mechanism, we designed and constructed a hydrophobic phase separation hydrogel induced by the electrostatic and hydrogen bond interaction assembly of PEI and PMAA. By coupling the effect of hydrogen bond, electrostatic force and hydrophobic interaction, our gel materials show an ultrahigh mechanical strength, which is up to 2.66 ± 0.18 MPa. Also, benefit from the coupled adhesion forces, as well as the ability to destroy the interface water layer, the adhesion strength on the polar materials can be up to 1.99 ± 0.11 MPa underwater, while that of the adhesion strength is about 2.70 ± 0.21 MPa under silicon oil. This work provides a deeper understanding of the underwater adhesion principle of barnacle glue. Furthermore, our bioinspired strategy would provide an inspiration for the fabrication of high mechanical gel materials, and the rapid strong adhesive used in both water and organic solvents.

Adhesives play an important role in the areas of biomedicine and engineering manufacture. Barnacle cement is a polyprotein complex secreted by barnacle, which can bind with various kinds of underwater substances; therefore, becoming a hotspot of new bionic adhesive materials because of its superior adhesion. The low solubility and complicated secretion process of barnacle cement hinder current understanding of its components, physicochemical properties, synthetic process, and so forth. This review mainly summarizes the latest research advances and applicable potentials of barnacle cement characterized by rapid adhesion, uneasy degradation, polymerized curing in an underwater environment, and so forth, and provides reference for both research and development of bioinspired synthetic wet adhesives. [ABSTRACT FROM AUTHOR]

Noting that 43 days is the minimum drifting time of the kelp rafts, the simulations confirmed that possible regions of origin could have been northern Tasmania (i.e., which have the nearest known populations of giant kelp), Wilsons Promontory, or somewhere along the pathway of the simulated particles. Keywords: barnacle; dispersal; Lepas; Macrocystis; wrack EN barnacle dispersal Lepas Macrocystis wrack 1 6 6 10/06/22 20221001 NES 221001 On 9 August 2020, two local marine naturalists (authors W. Marshall-Grey and J. Rankin) on the south coast of New South Wales, Australia noticed a significant amount of a large unfamiliar kelp washed up on a local beach. Giant kelp rafts wash ashore 450 km from the nearest populations and against the dominant ocean current Based on a general trajectory from northern Tasmanian to southern New South Wales, the maximum putative distance covered by the kelp rafts was ~600 km, which over 43 days equates to a drift speed of ~0.16 m/s. This is similar to other drift speed estimates for floating kelp rafts (~0.20 m/s, Fraser et al., 2010). [Extracted from the article]

Understanding the processes that guide carnivores in finding and selecting prey is a fundamental, unresolved challenge in sensory biology. To our knowledge, no published work has yet revealed the complete structural identities of compounds that cue preferences by generalist predators for different prey species. With this research imperative in mind, we determined the chemistry driving consumer preferences for live intact prey using two generalist predatory species (sea stars, Pisaster ochraceus; whelks, Acanthinucella spirata), along with two foundation prey species (mussels, Mytilus californianus; barnacles, Balanus glandula), inhabiting rocky, wave-swept shores. Each prey species is known to secrete either a 29.6 kDa (named 'KEYSTONEin') or a 199.6 kDa (named 'MULTIFUNCin') glycoprotein as a contact-chemical cue. Here, experimental manipulations utilized faux prey consisting of cleaned barnacle or mussel shells infused with KEYSTONEin, MULTIFUNCin or seawater (control) gels. Whelks exhibited a strong penchant for MULTIFUNCin over KEYSTONEin, irrespective of shell type. In contrast, sea stars generally preferred KEYSTONEin over MULTIFUNCin, but this preference shifted depending on the experimental context in which they encountered physical (shell) and chemical (glycoprotein) stimuli. This study ultimately demonstrates clear and contrasting chemical preferences between sea stars and whelks. It highlights the importance of experimental setting in determining chemical preferences. Finally, it shows that prey preferences by these predators hinge only on one or two contact-protein cues, without the need for quality coding via fluid-borne compounds, low-molecular-weight substances or mixture blends., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Abstract Background Barnacles are sessile crustaceans that attach to underwater surfaces using barnacle cement proteins. Barnacles have a calcareous or chitinous membranous base, and their substratum varies from biotic (e.g. corals/sponges) to abiotic surfaces. In this study, we tested the hypothesis that the cement protein (CP) composition and chemical properties of different species vary according to the attachment substrate and/or the basal structure. We examined the histological structure of cement glands and explored the variations in cement protein homologs of 12 barnacle species with different attachment habitats and base materials. Results Cement gland cells in the rocky shore barnacles Tetraclita japonica formosana and Amphibalanus amphitrite are eosinophilic, while others are basophilic. Transcriptome analyses recovered CP homologs from all species except the scleractinian coral barnacle Galkinia sp. A phylogenomic analysis based on sequences of CP homologs did not reflect a clear phylogenetic pattern in attachment substrates. In some species, certain CPs have a remarkable number of paralogous sequences, suggesting that major duplication events occurred in CP genes. The examined CPs across taxa show consistent bias toward particular sets of amino acid. However, the predicted isoelectric point (pI) and hydropathy are highly divergent. In some species, conserved regions are highly repetitive. Conclusions Instead of developing specific cement proteins for different attachment substrata, barnacles attached to different substrata rely on a highly duplicated cementation genetic toolkit to generate paralogous CP sequences with diverse chemical and biochemical properties. This general CP cocktail might be the key genetic feature enabling barnacles to adapt to a wide variety of substrata.

Larval settlement drives population and community dynamics and evolution of marine invertebrates. While it is well known that larvae sense a variety of biological and environmental factors, there is limited information on how they react to specific factors so as to locate settlement sites. Proteinaceous Waterborne Settlement Pheromone (WSP) was purified from adult barnacles, Amphibalanus amphitrite, in a previous study, but it is unclear how WSP guides barnacle cyprids to the source. Here, a series of settlement assays were conducted to investigate the concentration dependence of recombinant WSP. We report that low concentrations of barnacle WSP decrease the probability of settlement of conspecific cyprids, whereas high concentrations have the opposite effect. We suggest that this is because weak WSP informs cyprids that suitable settlement sites with adult barnacles are distant, inducing them to extend the larval phase. The present study clearly shows that larvae use WSP concentration, rather than presence/absence information. In barnacles, several other conspecific chemical/visual cues also attract larvae. This study opens the door to future research to determine how these cues influence larval behavior in nature.

Thoracican barnacles represent a unique group that has evolved in parallel identical somatotype s (sessile, stalked and asymmetric) in both normal and chemosynthetic environments. Hydrothermal vents and methane seeps are typical extreme deep-sea chemosynthetic habitats for marine macrobenthos. Characterizing the evolutionary history and adaptive strategy of barnacles is fundamentally important for understanding their origin, speciation, and diversification. Herein, we performed a series of phylogenetic analyses focusing on the mitochondrial genomes of the main extant barnacle lineages. Phylogenetic inferences and topology tests contradict the view of the sister relationship between verrucomorphs and balanomorphs, instead revealing that pollicipedids, calanticids and balanomorphs share common ancestor. Selective pressure analyses indicate that the two barnacle lineages of chemosynthetic ecosystems exhibit similar patterns in their evolution of adaptive characters, but have diverse and specific positive substitution sites of mitogenomes. Divergence times suggest that chemosynthetic barnacles originated in the Cenozoic, coinciding with the origins of other metazoan animals in chemosynthetic habitats as well as the Paleogene mass extinction and oceanic anoxic events. It is reasonable to suppose that ecological niche vacancy, sitotaxis, gene specificity in adaptive stress responses, and the subdivision of the ecological niche contributed to the origin and diversification of barnacles in chemosynthetic ecosystems.

As heavy metals are easy to accumulate and have strong biological toxicity, they pose a potential threat to human health by entering the human body through the cumulative effect of marine life. Land-based input is an important source of heavy metals in the ocean, which has a great influence on coastal water quality. In this study, the spatial distribution characteristics of heavy metals (Zn, Cu, Cd, Pb, Cr, As) in the coastal waters of the desulfurization process outlet of a power plant in Zhanjiang Bay were investigated, and the enrichment behavior of heavy metals by organisms (oysters and barnacles) were also studied. The results showed that, before the seawater desulfurization system was closed, there were high concentrations of heavy metals (Cu, Zn, Cd, Pb and Cr) in the surface seawater near the drainage outlet. The concentrations of these heavy metals in the surface seawater were higher than those in the bottom seawater within 100 m of the drainage outlet. After the seawater desulfurization system was closed, the average concentrations of Cu, Cr and As in seawater at each station decreased by 17.04%, 37.52% and 29.53%, respectively, while the average concentrations of Zn, Cd and Pb increased by 17.05%, 32.87% and 48.77%, respectively. Single factor pollution index (SFI) and bio-concentration factor (BCF) showed that there was a potential high accumulation risk of Zn in oysters and barnacles near the drainage outlet of desulfurization wastewater (0.5 < SFI < 1 and BCF > 1000). The SFI and BCF of each metal in oysters and barnacles decreased with the increase in distance from the drainage outlet. Generally, the coastal water quality of desulfurization process drainage area in Zhanjiang Bay were below the class Ⅱof the "Seawater quality standard" (GB 3097-1997) of China. However, the heavy metals content in seawater and organisms near the drainage outlet is slightly higher. This suggested that if the seawater desulfurization process runs for a long time, it will have a negative impact on the coastal water and organisms. [ABSTRACT FROM AUTHOR]

Crustaceans comprise an ecologically and morphologically diverse taxonomic group. They are typically considered resilient to many environmental perturbations found in marine and coastal environments, due to effective physiological regulation of ions and hemolymph pH, and a robust exoskeleton. Ocean acidification can affect the ability of marine calcifying organisms to build and maintain mineralized tissue and poses a threat for all marine calcifying taxa. Currently, there is no consensus on how ocean acidification will alter the ecologically relevant exoskeletal properties of crustaceans. Here, we present a systematic review and meta‐analysis on the effects of ocean acidification on the crustacean exoskeleton, assessing both exoskeletal ion content (calcium and magnesium) and functional properties (biomechanical resistance and cuticle thickness). Our results suggest that the effect of ocean acidification on crustacean exoskeletal properties varies based upon seawater pCO2 and species identity, with significant levels of heterogeneity for all analyses. Calcium and magnesium content was significantly lower in animals held at pCO2 levels of 1500–1999 µatm as compared with those under ambient pCO2. At lower pCO2 levels, however, statistically significant relationships between changes in calcium and magnesium content within the same experiment were observed as follows: a negative relationship between calcium and magnesium content at pCO2 of 500–999 µatm and a positive relationship at 1000–1499 µatm. Exoskeleton biomechanics, such as resistance to deformation (microhardness) and shell strength, also significantly decreased under pCO2 regimes of 500–999 µatm and 1500–1999 µatm, indicating functional exoskeletal change coincident with decreases in calcification. Overall, these results suggest that the crustacean exoskeleton can be susceptible to ocean acidification at the biomechanical level, potentially predicated by changes in ion content, when exposed to high influxes of CO2. Future studies need to accommodate the high variability of crustacean responses to ocean acidification, and ecologically relevant ranges of pCO2 conditions, when designing experiments with conservation‐level endpoints. [ABSTRACT FROM AUTHOR]

The purpose of this study was to further clarify marine tardigrade ecology; in particular, the monthly density fluctuations of Echiniscoides sigismundi and Styraconyx haploceros inhabiting the barnacle Fistulobalanus albicostatus in the intertidal zone. Both species were observed in all months, and the monthly body length distributions did not show a clear pattern, indicating these species breed throughout the year. However, the density of both species was higher in fall/winter than in spring/summer. The two species showed different prevalence and density distributions in the upper and lower parts of a barnacle bedrock in the intertidal zone. S. haploceros was found only in the lower part, where it dominated over E. sigismundi in most months. E. sigismundi was found in both parts, but its occurrence rate and density were higher in the lower part of the intertidal zone. The density of both species was significantly higher on the external surface of the barnacles than internally. No significant differences in tardigrade density were detected among different sizes of barnacles, living or dead, except for a significant difference in the density of E. sigismundi between dead and large live barnacles. Our findings suggest that E. sigismundi and S. haploceros are well adapted to inhabiting intertidal barnacles, and the fall/winter season is more favorable than spring/summer for marine tardigrades in temperate regions. E. sigismundi appears to tolerate the upper part of the barnacle bedrock in the intertidal zone, which may be an extremely harsh environment, better than S. haploceros. [ABSTRACT FROM AUTHOR]

Abstract Crustaceans comprise an ecologically and morphologically diverse taxonomic group. They are typically considered resilient to many environmental perturbations found in marine and coastal environments, due to effective physiological regulation of ions and hemolymph pH, and a robust exoskeleton. Ocean acidification can affect the ability of marine calcifying organisms to build and maintain mineralized tissue and poses a threat for all marine calcifying taxa. Currently, there is no consensus on how ocean acidification will alter the ecologically relevant exoskeletal properties of crustaceans. Here, we present a systematic review and meta‐analysis on the effects of ocean acidification on the crustacean exoskeleton, assessing both exoskeletal ion content (calcium and magnesium) and functional properties (biomechanical resistance and cuticle thickness). Our results suggest that the effect of ocean acidification on crustacean exoskeletal properties varies based upon seawater pCO2 and species identity, with significant levels of heterogeneity for all analyses. Calcium and magnesium content was significantly lower in animals held at pCO2 levels of 1500–1999 µatm as compared with those under ambient pCO2. At lower pCO2 levels, however, statistically significant relationships between changes in calcium and magnesium content within the same experiment were observed as follows: a negative relationship between calcium and magnesium content at pCO2 of 500–999 µatm and a positive relationship at 1000–1499 µatm. Exoskeleton biomechanics, such as resistance to deformation (microhardness) and shell strength, also significantly decreased under pCO2 regimes of 500–999 µatm and 1500–1999 µatm, indicating functional exoskeletal change coincident with decreases in calcification. Overall, these results suggest that the crustacean exoskeleton can be susceptible to ocean acidification at the biomechanical level, potentially predicated by changes in ion content, when exposed to high influxes of CO2. Future studies need to accommodate the high variability of crustacean responses to ocean acidification, and ecologically relevant ranges of pCO2 conditions, when designing experiments with conservation‐level endpoints.

The cathodic protection efficiency and hydrogen permeation behaviour of high-strength steel with barnacle adhesion in the tidal zone were studied using field exposure and laboratory simulation tests for 2 years. Because of the shielding effect, barnacles can lead to an uneven calcareous deposition, a flatter morphology and a higher protection efficiency of steel. By contrast, because of the higher hydrogen permeation current at the edge of the barnacle adhesion area (caused by a higher hydrogen evolution rate), barnacle adhesion can promote hydrogen permeation. A mechanism was proposed to explain the observed phenomenon, and its effect on service safety was analysed. • 2-year field exposure tests were conducted. • Barnacle adhesion can increase the cathodic protection current of steel at the edge of adhesion area. • Barnacle adhesion can increase the hydrogen permeation current density of steel. • High hydrogen permeation current of steel at the edge of adhesion area was confirmed by direct test. [ABSTRACT FROM AUTHOR]

The acorn barnacle (Cirripedia: Balanomorpha) is a sessile crustacean arthropod, distributing around the intertidal areas of tropical and temperate regions worldwide. Current practices for taxonomic identification are based on shell morphology and light microscopy, together with the use of scanning electron microscopy for arthropodal characters, which the latter technique requires complicated procedures. Through the recent technology of confocal light-sheet microscopy, here we demonstrate a clear description of Caudoeuraphia caudata (Pilsbry, 1916), a new record of its presence in eastern Thailand. This type of microscopy enables the high acquisition of fluorescent imaging of a whole barnacle’s body and arthropodal structures, including cirri and mouthpart imaging in three dimensions, with simple procedures for sample preparation and through harboring autofluorescence of their own barnacle structures. Hence, this technology could potentially be an alternative way for identifying acorn barnacles at the species-level and visualizing the diversity of these marine arthropods.

In the tourist zone of the Puerto Arista Sanctuary and 70 meters inside the beach line, on the coast of the state of Chiapas, Mexico, what is known as epibionts of a colony of the barnacle Conchoderma virgatum (Spengler, 1790) was found attached to the caudal section of a live pelagic sea snake, Hydrophis platurus (Linnaeus, 1766). Twenty-three epibionts were counted, each with an average length of 1.2 cm; the snake measured 61.97 cm in length and was subsequently relocated. The record is a novelty for the sanctuary area and unusual to find it in the terrestrial environment. [ABSTRACT FROM AUTHOR]

Background The barnacles are a group of >2,000 species that have fascinated biologists, including Darwin, for centuries. Their lifestyles are extremely diverse, from free-swimming larvae to sessile adults, and even root-like endoparasites. Barnacles also cause hundreds of millions of dollars of losses annually due to biofouling. However, genomic resources for crustaceans, and barnacles in particular, are lacking. Results Using 62× Pacific Biosciences coverage, 189× Illumina whole-genome sequencing coverage, 203× HiC coverage, and 69× CHi-C coverage, we produced a chromosome-level genome assembly of the gooseneck barnacle Pollicipes pollicipes. The P. pollicipes genome is 770 Mb long and its assembly is one of the most contiguous and complete crustacean genomes available, with a scaffold N50 of 47 Mb and 90.5% of the BUSCO Arthropoda gene set. Using the genome annotation produced here along with transcriptomes of 13 other barnacle species, we completed phylogenomic analyses on a nearly 2 million amino acid alignment. Contrary to previous studies, our phylogenies suggest that the Pollicipedomorpha is monophyletic and sister to the Balanomorpha, which alters our understanding of barnacle larval evolution and suggests homoplasy in a number of naupliar characters. We also compared transcriptomes of P. pollicipes nauplius larvae and adults and found that nearly one-half of the genes in the genome are differentially expressed, highlighting the vastly different transcriptomes of larvae and adult gooseneck barnacles. Annotation of the genes with KEGG and GO terms reveals that these stages exhibit many differences including cuticle binding, chitin binding, microtubule motor activity, and membrane adhesion. Conclusion This study provides high-quality genomic resources for a key group of crustaceans. This is especially valuable given the roles P. pollicipes plays in European fisheries, as a sentinel species for coastal ecosystems, and as a model for studying barnacle adhesion as well as its key position in the barnacle tree of life. A combination of genomic, phylogenetic, and transcriptomic analyses here provides valuable insights into the evolution and development of barnacles. [ABSTRACT FROM AUTHOR]

Barnacle adhesion is a focus for fouling-control technologies as well as the development of bioinspired adhesives, although the mechanisms remain very poorly understood. The barnacle cypris larva is responsible for surface colonisation. Cyprids release cement from paired glands that contain proteins, carbohydrates and lipids, although further compositional details are scant. Several genes coding for cement gland-specific proteins were identified, but only one of these showed database homology. This was a lysyl oxidase-like protein (lcp_LOX). LOX-like enzymes have been previously identified in the proteome of adult barnacle cement secretory tissue. We attempted to produce recombinant LOX in E. coli, in order to identify its role in cyprid cement polymerisation. We also produced two other cement gland proteins (lcp3_36k_3B8 and lcp2_57k_2F5). lcp2_57k_2F5 contained 56 lysine residues and constituted a plausible substrate for LOX. While significant quantities of soluble lcp3_36k_3B8 and lcp2_57k_2F5 were produced in E. coli, production of stably soluble lcp_LOX failed. A commercially sourced human LOX catalysed the crosslinking of lcp2_57k_2F5 into putative dimers and trimers, and this reaction was inhibited by lcp3_36k_3B8. Inhibition of the lcp_LOX:lcp2_57k_2F5 reaction by lcp3_36k_3B8 appeared to be substrate specific, with no inhibitory effect on the oxidation of cadaverine by LOX. The results demonstrate a possible curing mechanism for barnacle cyprid cement and, thus, provide a basis for a more complete understanding of larval adhesion for targeted control of marine biofouling and adhesives for niche applications. [ABSTRACT FROM AUTHOR]

The condition of coral reefs in Damas Beach is included in the bad category because there are many fragments of coral reefs (rubble) caused by fishing nets caught in the reef. Based on the problem of coral reefs contained in the waters of Damas Beach, there are innovations to sink artificial reefs. The condition of artificial reefs that have been derived in the waters of Damas Beach within 2.5 years needs to be monitored to find out the macroinvertebrates that stick to the artificial reefs. Retrieval of macroinvertebrate data using the underwater photo transect method with the help of underwater cameras to produce observational data. The results found 10 types of macroinvertebrates with a total of 9,293 individuals. The composition of attached macroinvertebrates is dominated by barnacles by 66% and the density of macroinvertebrates is dominated by barnacles by 4.50 ind / m² out of a total density of 6.88 ind / m².

Abstract Sex allocation theory predicts that the optimal sexual resource allocation of simultaneous hermaphrodites is affected by mating group size (MGS). Although the original concept assumes that the MGS does not differ between male and female functions, the MGS in the male function (MGSm; i.e., the number of sperm recipients the focal individual can deliver its sperm to plus one) and that in the female function (MGSf; the number of sperm donors plus one) do not always coincide and may differently affect the optimal sex allocation. Moreover, reproductive costs can be split into “variable” (e.g., sperm and eggs) and “fixed” (e.g., genitalia) costs, but these have been seldom distinguished in empirical studies. We examined the effects of MGSm and MGSf on the fixed and variable reproductive investments in the sessilian barnacle Balanus rostratus. The results showed that MGSm had a positive effect on sex allocation, whereas MGSf had a nearly significant negative effect. Moreover, the “fixed” cost varied with body size and both aspects of MGS. We argue that the two aspects of MGS should be distinguished for organisms with unilateral mating.

Abstract Background Barnacles are specialized marine organisms that differ from other crustaceans in possession of a calcareous shell, which is attached to submerged surfaces. Barnacles have a wide distribution, mostly in the intertidal zone and shallow waters, but a few species inhabit the deep-sea floor. It is of interest to investigate how such sessile crustaceans became adapted to extreme deep-sea environments. We sequenced the transcriptomes of a deep-sea barnacle, Glyptelasma gigas collected at a depth of 731 m from the northern area of the Zhongjiannan Basin, and a shallow-water coordinal relative, Octolasmis warwicki. The purpose of this study was to provide genetic resources for investigating adaptation mechanisms of deep-sea barnacles. Results Totals of 62,470 and 51,585 unigenes were assembled for G. gigas and O. warwicki, respectively, and functional annotation of these unigenes was made using public databases. Comparison of the protein-coding genes between the deep- and shallow-water barnacles, and with those of four other shallow-water crustaceans, revealed 26 gene families that had experienced significant expansion in G. gigas. Functional annotation showed that these expanded genes were predominately related to DNA repair, signal transduction and carbohydrate metabolism. Base substitution analysis on the 11,611 single-copy orthologs between G. gigas and O. warwicki indicated that 25 of them were distinctly positive selected in the deep-sea barnacle, including genes related to transcription, DNA repair, ligand binding, ion channels and energy metabolism, potentially indicating their importance for survival of G. gigas in the deep-sea environment. Conclusions The barnacle G. gigas has adopted strategies of expansion of specific gene families and of positive selection of key genes to counteract the negative effects of high hydrostatic pressure, hypoxia, low temperature and food limitation on the deep-sea floor. These expanded gene families and genes under positive selection would tend to enhance the capacities of G. gigas for signal transduction, genetic information processing and energy metabolism, and facilitate networks for perceiving and responding physiologically to the environmental conditions in deep-sea habitats. In short, our results provide genomic evidence relating to deep-sea adaptation of G. gigas, which provide a basis for further biological studies of sessile crustaceans in the deep sea.

Hydrogels are promising materials for wound protection, but in wet, or underwater environments, the hydration layer and swelling of hydrogels can seriously reduce adhesion and limit their application. In this study, inspired by the structural characteristics of strong barnacle wet adhesion and combined with solvent exchange, a robust wet adhesive hydrogel (CP-Gel) based on chitosan and 2-phenoxyethyl acrylate was obtained by breaking the hydration layer and resisting swelling. As a result, CP-Gel exhibited strong wet adhesion to various interfaces even underwater, adapted to joint movement and skin twisting, resisted sustained rushing water, and sealed damaged organs. More importantly, on-demand detachment and controllable adhesion were achieved by promoting swelling. In addition, CP-Gel with good biosafety significantly promotes seawater-immersed wound healing and is promising for use in water-contact wound care, organ sealing, and marine emergency rescue., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Most organisms experience ontogenescence (high and decreasing mortality from conception to the age of maturity) in spite of the clear evolutionary disadvantage of dying prior to reproducing. One hypothesis that may help to explain the prevalence and persistence of ontogenescence is the Transitional Timing Hypothesis, which states that developmental transitions are dangerous and concentrated in the earliest phases of life (e.g., hatching or birth). This study's goal was to examine the transitional dangers of early development and hatching in the barnacle Chthamalus fragilis. Barnacle egg lamellae were monitored for 2 weeks after extraction from their parents, and all hatching events were recorded along with whether each hatched larva was a successful swimmer or not. The total number of eggs that failed to hatch from each egg lamella was also determined. Results showed significant brood mortality prior to hatching as well as a large proportion of newly-hatched larvae that were unable to swim well. There was also a clear pattern in the timing of hatching events from egg lamellae. However, there was no effect of delayed hatching on either hatching success or swimming ability of larvae. The high proportion of non-hatching and poor-swimming larvae lend support to the Transitional Timing Hypothesis, suggesting that early developmental stages and hatching in barnacles (and probably other organisms, too) are potentially dangerous transitional events that cannot be avoided and should be taken into account when studying the population ecology of these species. [ABSTRACT FROM AUTHOR]

Jombodin, T.; Songkai, P.; Wichachucherd, B., and Rodcharoen, E., 2021. The relationship between salinity and benthic fauna diversity and abundance at Songkhla Port, Thailand. Journal of Coastal Research, 37(6), 1173–1180. Coconut Creek (Florida), ISSN 0749-0208. Benthic fauna plays an important role in marine ecosystems as the primary food for other aquatic animals, and this animal group helps reduce sediment nutrients by filter feeding. The aim of this study was to evaluate and explain the diversity and abundance of the benthic fauna community at the Songkhla port, where both human activities and environmental fluctuations affect this community. Benthic fauna and water samples were collected at 2-month intervals from January to November 2017. The results show that most physical parameters had wide ranges and varied by month. The benthic fauna in the Songkhla lagoon was observed in this study. The results showed a higher number of taxa compared with a previous study. Three phyla, namely, Annelida, Arthropoda, and Mollusca, had 25 taxa recorded in this study. Crustaceans were the most diverse (nine taxa) and abundant (2981 ± 313 ind/m2) group, followed by polychaetes (eight families, 2350 ± 288 ind/m2) and mollusks (eight taxa, 633 ± 200 ind/m2). Barnacles were the dominant group of crustaceans (2153 ± 758 ind/m2), whereas Serpulidae (1864 ± 647 ind/m2) and Mytilidae (447 ± 367 ind/m2) were the dominant families of polychaetes and mollusks, respectively. Cluster analysis showed that the distribution of benthic fauna and physicochemical water quality varied with similar patterns. Clustering gave two groups: for rainy season from November to January and for dry season from May to November. According to canonical correspondence analysis, salinity and transparency were the main environmental factors associated with the distribution pattern of benthic fauna in the area. In conclusion, the activities at the Songkhla port have not yet created problems for marine benthic fauna; instead, seasonal changes appear to drive changes in benthic fauna. However, future construction developments can affect the geographical area, complementing stresses from parameter changes at local scales. [ABSTRACT FROM AUTHOR]

In previous papers, the nanosecond laser has been proven to be an effective tool for removing the settlement of soft-fouling microorganisms (biofilm, microbial film, and microbiofoulings). This work is a continued study on laser cleaning of marine biofouling. The authors attempt to develop a hybrid laser treatment method to control the hard-shelled barnacles attached to Al alloys. Morphologies of the laser-cleaned surfaces were evaluated by a digital camera, 3D optical microscopy, and scanning electron microscopy. Furthermore, a high-speed camera and fiber optic spectrometer were used to capture the specific laser cleaning dynamic behaviors and characterize the chemical compositions of laser-induced plasma, respectively. The shell structures of the barnacles cannot be removed by a nanosecond fiber laser but continuous CO2 laser, while for the base plates of the barnacles the result is the opposite. Hence, a step-by-step CO2/nanosecond hybrid laser cleaning process is proposed to conquer the attached barnacles fouling. The cleaning strategy follows a top-down principle of the barnacles' structures. In the first step, the CO2 laser is utilized to heat the external shell; thus, the upper parietal shell and the main body are entirely peeled off. In the second step, the nanosecond laser is employed to remove the lower remaining base plate, cement layer, and biofilm. Laser cleaning mechanisms of barnacles included heating, stripping, and ablation. [ABSTRACT FROM AUTHOR]