Marine Organisms Research Articles

Chemical profiling, cytotoxicity and mode of action of sea urchin Echinometra mathaei exoskeleton extract in HepG2 cancer cell line

Marine organisms contain several secondary metabolites with potent biological and pharma­cological activities. This research aimed to study the cytotoxicity and mechanism of action of methanol (MeOH) extract from the exoskeleton (shell and spines) of the sea urchin Echinometra Mathaei on human liver cancer cell line (HepG2). E. mathaei was collected from the intertidal zone of the Red Sea, Al-Ain Al-Sokhna, Egypt. HepG2 cells were treated with the MeOH extract for 24 and 48 hours to assess the cytotoxic activity and the potential molecular mechanisms. The expression levels of apoptosis-, autophagy-, and cell proliferation-related genes and/or proteins were measured. In addition, metabolomic profiling of the extract was performed by gas chromatography-mass spectrometry (GC-MS) analysis. The extract displayed cytotoxic activity on the liver cancer cells (IC50 29.47 and 14.97 µg/ml at 24 and 48 hours, respectively). It induced apoptosis, autophagy and inhibited cell proliferation of HepG2 cells. The metabolomic profiling showed that the extract is rich in fatty acids. These results demonstrated that the exoskeleton MeOH extract of E. mathaei induced apoptosis in HepG2 cells, confirming its cytotoxic effect. Therefore, a thorough investigation of its molecular target and structure is necessary to develop novel anticancer therapeutics from marine Sea urchins.

Potential of Marine Sponge Metabolites against Prions: Bromotyrosine Derivatives, a Family of Interest.

The screening of 166 extracts from tropical marine organisms (invertebrates, macroalgae) and 3 cyclolipopeptides from microorganisms against yeast prions highlighted the potential of Verongiida sponges to prevent the propagation of prions. We isolated the known compounds purealidin Q (1), aplysamine-2 (2), pseudoceratinine A (3), aerophobin-2 (4), aplysamine-1 (5), and pseudoceratinine B (6) for the first time from the Wallisian sponge Suberea laboutei. We then tested compounds 1-6 and sixteen other bromotyrosine and bromophenol derivatives previously isolated from Verongiida sponges against yeast prions, demonstrating the potential of 1-3, 5, 6, aplyzanzine C (7), purealidin A (10), psammaplysenes D (11) and F (12), anomoian F (14), and N,N-dimethyldibromotyramine (15). Following biological tests on mammalian cells, we report here the identification of the hitherto unknown ability of the six bromotyrosine derivatives 1, 2, 5, 7, 11, and 14 of marine origin to reduce the spread of the PrPSc prion and the ability of compounds 1 and 2 to reduce endoplasmic reticulum stress. These two biological activities of these bromotyrosine derivatives are, to our knowledge, described here for the first time, offering a new therapeutic perspective for patients suffering from prion diseases that are presently untreatable and consequently fatal.

Experimental and numerical study on dynamic responses of a TLP-type modular floating structure system

This paper explores a proposed TLP-type modular floating structure system, incorporating both central TLP modules and peripheral floating artificial reef modules. The outermost floating artificial reef module can function as a floating breakwater, and also serving as a habitat for surrounding marine organisms. To assess the system's multi-body coupling dynamics under various wave conditions, both scale model tests (1:80) and time-domain numerical simulations were performed. The simulations accounted for hydrodynamic interactions among the bodies and the mechanical coupling effects. During the scale model test, a survival strategy has been proposed to prevent collision risks between reef modules and adjacent TLP modules, which involving a hinge connector with additional linear spring. A preliminary stiffness recommendation was suggested by a trade-off between the pitch of the reef module and the spring force. Numerical and experimental results have been widely compared and discussed, including the multi-body motion responses and the tension leg loads. A good agreement has been achieved, although responses are slightly overestimated by numerical simulation due to the neglect of the viscous damping effect. In addition, the responses of the proposed system, connected with and without the outermost floating artificial reef module, have been compared and analyzed. The results suggest that the connection of the reef module can significantly reduce the system's surge response and enhance its survivability under severe sea conditions. The validated numerical model can serve as a valuable reference for subsequent system optimization and further engineering applications.

The impact of marine traffic radiated underwater noise on the in the Baltic Sea

Continuous anthropogenic noise, generated by commercial shipping, is considered to exert a considerable pressure on the marine environment. Noise emitted by ships is mainly due to their propellers whose energy is predominantly at low frequencies and can interfere with the communication of marine animals. The EU Marine Strategy Framework Directive (MSFD), has set the objective of achieving good environmental status of Europe's seas. In particular, anthropogenic underwater sound should be at a level that does not harm the marine environment. Here we present the first implementation of the new framework for assessing the environmental status of low frequency continuous noise on a basin scale, carried out in the frames of the EU-funded HELCOM BLUES project. The assessment was based on modeled levels in two 125 and 500 Hz decidecade bands deemed relevant for the indicator fish and marine mammals respectively. Sound propagation modelling, calibrated against underwater ambient noise monitoring data, results in statistical sound maps in species-specific frequency bands. The application of spatial thresholds allows the environmental status of marine areas to be determined. Factors affecting the reliability of results are discussed.

Underwater radiated noise explained from ship characteristics and operating conditions - Model obtained from the MARS database

Understanding how ship characteristics and operating conditions impact underwater radiated noise (URN) is key to identifying essential avenues for noise reduction and predict associated risks for the marine life. Previous studies have revealed that current models could only explain up to 50% of the observed variability in URN levels. In this study, we used a unique dataset, collected within the Marine Acoustic Research Station (MARS) project (www.projet-mars. ca/en). The dataset is consisting of ~1000 acoustic signatures from vessels in the St. Lawrence shipping lane (eastern Canada), and 174 high-quality signatures from partner vessels following an optimized measurement protocol and considering design parameters, meteorological, and oceanographic data. Applying functional regression, as described by MacGillivray et al. (2022), we quantified the relationship between vessel characteristics, operation conditions and URN. Our findings quantify the direct effect of the speed, size, and draft on URN across a frequency range of 10-500 Hz. Using these relationships, we propose a tailored URN predictive model representative of the St. Lawrence fleet. We then compare its performance to previously published models and asses the gains linked to the active collaboration of ship owners, contributing to the wide range of available operation conditions available in our dataset.

Bioactive Potential of Algae and Algae-Derived Compounds: Focus on Anti-Inflammatory, Antimicrobial, and Antioxidant Effects.

Algae, both micro- and macroalgae, are recognized for their rich repository of bioactive compounds with potential therapeutic applications. These marine organisms produce a variety of secondary metabolites that exhibit significant anti-inflammatory, antioxidant, and antimicrobial properties, offering promising avenues for the development of new drugs and nutraceuticals. Algae-derived compounds, including polyphenols, carotenoids, lipids, and polysaccharides, have demonstrated efficacy in modulating key inflammatory pathways, reducing oxidative stress, and inhibiting microbial growth. At the molecular level, these compounds influence macrophage activity, suppress the production of pro-inflammatory cytokines, and regulate apoptotic processes. Studies have shown that algae extracts can inhibit inflammatory signaling pathways such as NF-κB and MAPK, reduce oxidative damage by activating Nrf2, and offer an alternative to traditional antibiotics by combatting bacterial infections. Furthermore, algae's therapeutic potential extends to addressing diseases such as cardiovascular disorders, neurodegenerative conditions, and cancer, with ongoing research exploring their efficacy in preclinical animal models. The pig model, due to its physiological similarities to humans, is highlighted as particularly suitable for validating the bioactivities of algal compounds in vivo. This review underscores the need for further investigation into the specific mechanisms of action and clinical applications of algae-derived biomolecules.

Mesoscale ocean eddies determine dispersal and connectivity of corals at the RMS Titanic wreck site

The sinking of the RMS Titanic on 15 April 1912 remains one of most iconic maritime disasters in history. Today, the wreck site lies in waters 3800 m deep approximately 690 km south southeast of Newfoundland, Atlantic Canada. The wreck and debris field have been colonized by many marine organisms including the octocoral Chrysogorgia agassizii. Because of the rapid deterioration of the Titanic and the vulnerability of natural deep-sea coral populations to environmental changes, it is vital to understand the role the Titanic as well as other such structures could play in connecting ecosystems along the North American slope. Based on Lagrangian experiments with more than one million virtual particles and different scenarios for larval behavior, given the uncertainties around the biology of chrysogorgiids, the dispersal of larvae spawned at the Titanic wreck is studied in a high-resolution numerical ocean model. While the large-scale bathymetry shields the Titanic from a strong mean flow, mesoscale ocean eddies can considerably affect the deep circulation and cause a significant speed up, or also a reversal, of the circulation. As a consequence, the position of upper and mid-ocean eddies in the model largely controls the direction and distance of larval dispersal, with the impact of eddies outweighing the importance of active larval swimming in our experiments. Although dependent on larval buoyancy and longevity, we find that the Titanic could be reached by larvae spawned on the upper slope east of the Grand Banks. Therefore, the Titanic could act as a stepping stone connecting the upper to the deep continental slope off Newfoundland. From the Titanic, larvae then spread into deep Canadian waters and areas beyond national jurisdiction.

Characteristics and drivers of marine heatwaves in the western South Atlantic

Marine heatwaves are events of extreme warming in the ocean and have devastating consequences for marine life. Here we used a K-mean clustering analysis to detect different types of marine heatwaves along the South American coast from 10°S to 45°S and identify their remote drivers. In the central part of the domain, marine heatwaves are associated with atmospheric blocking caused by wave trains triggered by the Madden-Julian Oscillation. On the other hand, marine heatwaves occurring along the northern and southern coast of South America are associated with El Niño and La Niña events, respectively. The intensity and duration of these marine heatwaves are modulated by the development phase and intensity of the Niño and Niña events. By identifying the climatic modes of variability leading to each type of marine heatwaves, our study can help develop adaptation strategies, such as early warning systems, to prevent the devastating effects of marine heatwaves.

A comparative study on the toxic effects of lead pollution and nanoplastic-lead mixed pollution on red drum and their detoxification strategies

Nanoplastics and heavy metals pose various adverse effects on marine organisms. However, the combined toxicity of nanoplastics and lead pollution to marine fish is not fully understood. This study investigates the toxic effects and detoxification strategies of lead pollution (p07) compared to nanoplastic-lead mixed pollution (m07) in red drum during exposure and recovery phases. Under m07 pollution, the maximum lead content in muscle was 22.61 mg/kg, which was significantly higher than the 15.82 mg/kg observed under p07 pollution. This finding demonstrated that nanoplastics significantly enhance lead accumulation, leading to more severe toxic effects on red drum. Histological analyses revealed that lipid droplets in the liver and epithelial lifting in the gills were the primary lesion types. During the exposure periods, red drum primarily detoxified lead through cellular renewal and the removal of damaged proteins under p07 pollution. Conversely, under m07 pollution, detoxification relied on cellular senescence, apoptosis, endocytosis, and the removal of damaged proteins. In the recovery phases, red drum predominantly recovered through cell proliferation and antioxidant responses under p07 pollution. Under m07 pollution, the focus shifted to functional protein synthesis, apoptosis, endocytosis, and lipid metabolism. This study offers valuable insights into the monitoring and management of combined environmental pollution.

LITERATUR STUDI MENGENAI ADSORBEN LIMBAH CANGKANG HEWAN LAUT DALAM BERBAGAI KEILMUAN

The utilization of marine animal waste as a base material for adsorbents has become an increasingly popular research topic across various scientific fields, including chemistry, environmental science, and materials science. Waste from marine animals, such as crab shells, oyster shell, seashell, and shrimp shell, possesses high potential to be processed into adsorbents due to their abundant calcium carbonate, chitosan, and protein content. The use of this waste as adsorbents not only provides a solution to environmental issues related to the accumulation of organic waste but also offers cheaper and eco-friendly alternative for water treatment, air purification, and contaminated soil remediation. Research has shown that marine animal waste-based adsorbents are effective in removing various pollutants, including heavy metals, textile dyes, and hazardous organic compounds. With specific modification techniques, the performance of these adsorbents can be enhanced, making them competitive with commercial adsorbents. Overall, the use of marine animal waste as adsorbents represents an innovative approach that contributes to waste reduction and the enhancement of environmental sustainability.

Identifying toxic elements in water, sediments, and roots of mangrove forest (Avicennia marina) in Chabahar Bay, Sea of Oman

Mangroves play a crucial role in filtering pollutants from water and sediments. However, excessive accumulation of potentially toxic elements (PTEs) has harmful effects on marine organisms. This article investigates the concentration and distribution of PTEs in water, sediment, and the roots of endangered mangrove species in Chabahar Bay, a subtropical coastal wetland. The relationship between PTE absorption and accumulation rates with flow rate, mangrove extent, and sedimentation was also explored. Water, sediments, and aerial roots samples were taken at four stations along the wetland from upstream fresh water toward outfall. According to the results, Cd had more distribution in sediment and water samples and plants did not play as adsorbent in the study area. The lowest and highest PTEs concentrations were detected in water and sediment media, respectively. The average concentrations of PTEs in the sediments in the Chabahar Bay were Fe > Cr > Zn > Ni > Cu > Pb > Co > As > Cd while in aerial roots of the mangroves were Fe > Zn > Ni > Cr > Cu > Co > As > Pb > Cd. Except Zn, As, and Cd, there was a good correlation between increasing PTEs content in the sediments with decreasing flow velocity and increasing vegetation density along stations 3 to 4. In addition, the amount of PTEs uptake by the mangroves was less than that of global wetlands. The results also demonstrated a greater uptake in aerial roots in saline water for Cr, Ni and Co. Since the absorption rate of PTEs by the aerial roots of pneumatophores is slower than that in sediments, elevated concentrations of PTEs in the sediment can disrupt the entire ecosystem, leading to a potential decline in biodiversity. These toxins can enter the food chain, affecting not only organisms directly interacting with the sediment but also higher trophic levels, such as fish and birds.

Urban estuary serves as a critical nexus for the land-sea transfer of the terrestrial pathogen Toxoplasma gondii

Terrestrial runoff is a key pathway for the transmission of the terrestrial pathogen Toxoplasma gondii from land to sea, posing a significant threat to marine ecosystems. Understanding the mechanisms by which T. gondii is transported from terrestrial to marine environment is crucial for developing effective prevention and control strategies for toxoplasmosis in marine organisms. This study investigates the transport of T. gondii through terrestrial runoff in the Sow River, a representative watershed in Weihai, China. Surface water, bottom water, and sediment samples were collected and analyzed for T. gondii DNA using PCR methods. Out of 1776 samples, the prevalence of T. gondii was found to be 8.61 % in surface water, 9.80 % in bottom water, and 16.61 % in sediment, with sediment identified as a significant reservoir. Additionally, estuarine zones showed a higher prevalence of T. gondii (16.80 %) compared to riverine areas (9.00 %). The study further revealed that seasonal climate variations, such as temperature and precipitation, had no significant impact on the distribution of T. gondii. However, there was significant spatial variability, with estuarine conditions facilitating increased pathogen transmission. These findings highlight the importance of estuaries and sediments as key conduits for T. gondii entry in marine food webs. The results provide a theoretical basis for designing infection prevention and control strategies aimed at protecting marine ecosystems.

When the Going Gets Tough, the Females Get Going: Sex-Specific Physiological Responses to Simultaneous Exposure to Hypoxia and Marine Heatwave Events in a Ubiquitous Copepod.

The existence of sex-specific differences in phenotypic traits is widely recognized. Yet they are often ignored in studies looking at the impact of global changes on marine organisms, particularly within the context of combined drivers that are known to elicit complex interactions. We tested sex-specific physiological responses of the cosmopolitan and ecologically important marine copepod Acartia tonsa exposed to combined hypoxia and marine heatwave (MHW) conditions, both of which individually strongly affect marine ectotherms. Females and males were acutely exposed for 5 days to a combination of either control (18°C) or a high temperature mimicking a MHW (25°C), and normoxia (100% O2 sat.) or mild hypoxia (35% O2 sat.). Life-history traits, as well as sex-specific survival and physiological traits, were measured. Females had overall higher thermal tolerance levels and responded differently than males when exposed to the combined global change drivers investigated. Females also showed lower metabolic thermal sensitivity when compared to males. Additionally, the MHW exerted a dominant effect on the traits investigated, causing a lower survival and higher metabolic rate at 25°C. However, egg production rates appeared unaffected by hypoxia and MHW conditions. Our results showed that MHWs could strongly affect copepods' survival, that combined exposure to hypoxia and MHW exerted an interactive effect only on CTmax, and that sex-specific vulnerability to these global change drivers could have major implications for population dynamics. Our results highlight the importance of considering the differences in the responses of females and males to rapid environmental changes to improve the implementation of climate-smart conservation approaches.

Multigenerational effects of combined exposure of triphenyltin and micro/nanoplastics on marine medaka (Oryzias melastigma): From molecular levels to behavioral response

In natural environments, micro/nanoplastics (MNP) inevitably coexist with various pollutants, making it essential to examine their combined toxicity and intergenerational effects on marine organisms. This study investigated the combined toxicity and intergenerational effects of exposure to triphenyltin (T), microplastics (M), nanoplastics (N), a combination of microplastics and triphenyltin (MT), and a combination of nanoplastics and triphenyltin (NT) on marine medaka. The results showed that all treatments had adverse and intergenerational effects on marine medaka. Regarding oxidative stress and energy metabolism, smaller sized plastic particles caused more significant damage to the organisms. However, MT inflicted greater gonadal system damage than NT, leading to imbalanced sex hormone levels. Additionally, T induced hyperactivity in fish, whereas MNP tended to induce behavioral depression. Notably, large plastic particles in the F0 generation had a more pronounced impact on depressive behaviors compared to smaller particles. These findings suggest that both individual and combined exposures to TPT and MNP can detrimentally affect marine medaka from the molecular to behavioral levels, posing risks to population sustainability. This study provided a robust theoretical foundation and deeper insights into the ecotoxicological impacts and risk assessments of coexisting pollutants.

The trophodynamics of polycyclic aromatic hydrocarbons in marine food webs: The importance of trophic level span from insights into Liaodong Bay (China).

The occurrence and trophic transfer of polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystems is vital to assess ecological risks. PAHs concentrations were analyzed in seawater, sediment, plankton, and marine species (15 fish species, 8 invertebrate species, 3 marine mammals), collected from Liaodong Bay (China). Bioaccumulation and biomagnification were calculated to demonstrate the biotransfer pattern of PAHs from the environmental matrix to high-level predators through the food web. Total PAHs concentrations ranged from 81.2 to 197.6 ng/L in seawater, 51.4 to 304.8 ng/g (dw) in sediment, and 65.3 to 28,885 ng/g (lw) in all biota samples. Three- and four-ring PAHs constituted major components (> 81% in each case) of PAH congener profiles. Lower biota-sediment accumulation factors (BSAFs) and bioaccumulation factors (BAFs) values indicated limited bioaccumulation of PAHs within marine organisms. Also, 77% of biomagnification factors (BMFTL) values of PAHs in spotted seal and finless porpoise were >1, whereas opposite transfer patterns of PAHs were observed in food webs with trophic values of 1.5-3.5 and 3.0-4.0; that is, trophic dilution (trophic magnification factor (TMF) <1) and trophic magnification (TMF >1), respectively. This study provides novel insights into the importance of TL span for trophodynamics of PAHs within food webs.

Petrographic and geochemical signatures of the Upper Permian Gondwana coals: Newcastle Coal Measures, Northern Sydney Basin, Australia

This research presents an integrated approach to organic petrographical and geochemical characteristics of the Upper Permian Newcastle Coal Measures outcropping in the northern Sydney Basin, southeast Australia. Twenty-seven coal, coaly mudstone and mudstone samples were collected and analyzed by using organic petrography (maceral composition and vitrinite reflectance) techniques, Rock–Eval pyrolysis, bitumen extraction and gas chromatography - mass spectrometry (GC–MS). The obtained results indicate that the samples exhibit promising gas-prone source rock potential and contain a predominantly terrestrial in origin organic matter, with limited contribution by marine organisms. The prevalence of terrestrial organic matter is inferred by the presence of collotelinite and sporinite macerals in most of the samples and the ternary plot of C27, C28 and C29 regular steranes. Further, the low C27/C29 ratio, the cross-plots of C27/(C27 + C29) regular steranes vs. Pr/Ph ratio, the C27/C29 vs. Pr/Ph and the C24 tetracyclic/C26 tricyclic terpane ratio point also to the terrestrial origin of the organic matter. The obtained values of vitrinite reflectance, Tmax, OEP27–31 and CPI25–33, along the cross plots of 20S/(20S + 20R) versus ββ/(ββ + αα) suggest that the samples are immature and were subjected to a low burial depth. The examined samples indicate accumulation in a delta-plain environment of deposition, under fluctuating oxic/anoxic conditions, in a humid climatic zone that is characterized by dry periods, interrupting the longer-termed humid climatic regime. This research adds knowledge on the source rock potential in the northern Sydney Basin and on the environmental and climatic setting of a time interval just prior to the major Permian - Triassic climatic crisis.

Metabolic responses of sea anemone and jellyfish to temperature and UV bleaching: Insights into stress adaptation using LCMS-based metabolomics, molecular networking and chemometrics

IntroductionClimate change poses various threats to marine life, particularly in shallow tropical waters. Objective: The impact of increased temperature and ultraviolet (UV) exposure on two photosymbiotic Cnidarians, a common bubble-tip anemone and an upside-down jellyfish, was investigated. MethodsTo illustrate the response of aquatic organisms, the metabolomes of unstressed Entacmaea quadricolor and Cassiopea andromeda were compared for detailed metabolite profiling. UHPLC-MS coupled with chemometrics and GNPS molecular networking was employed for sample classification and identification of markers unique to stress responses in each organism. ResultsSeveral compounds with bioactive functions, including peptides and terpenoids, were reported for the first time in both organisms, viz. cyclic tetraglutamate, campestriene, and ceramide aminoethyl phosphonate (CEAP d18:2/16:0). Both anemone and jellyfish were subjected to either elevated UV-B light intensity up to 6.6 KJ m−2 or increased temperatures (28 °C, 30 °C, 32 °C, and 34 °C) over 4 days. Phospholipids, steroids, and ceramides emerged as chief markers of both types of stress, as revealed by the multivariate data analysis. Lysophosphatidylcholine (LPC 16:0), LPC (18:0/0:0), and echinoclasterol sulfate appeared as markers in both UV and thermal stress models of the anemone, whereas methyl/propyl cholestane-hexa-ol were discriminatory in the UV stress model only. In the case of jellyfish, nonpolar glycosyl ceramide GlcCer (d14:1/28:6) served as a marker for UV stress, whereas polar peptides were elevated in the thermal stress model. Interestingly, both models of jellyfish share a phospholipid, lysophosphatidylethanolamine (LPE 20:4), as a distinctive marker for stress, reported to be associated indirectly with the activity of innate immune response within other photosymbiotic Cnidaria such as corals and appears to be a fundamental stress response in marine organisms. ConclusionThis study presents several bioinformatic tools for the first time in two cnidarian organisms to provide not only a broader coverage of their metabolome but also broader insights into cnidarian bleaching in response to different stressors, i.e., heat and UV light, by comparing their effects in anemone versus jellyfish.

3-Acetyl Indole in the Synthesis of Natural Bioactive Compounds

Natural products, with their various sources from plants, marine organisms, and microorganisms, are considered a key source and inspiration for medicines and continue to be so. Indole alkaloids are a class of alkaloids and represent a large subunit of natural prod-ucts. Indole alkaloids of biological importance are numerous and cover a wide range of phar-maceutical applications, including anticancer, antiviral, antimicrobial, anti-inflammatory, and antioxidant. Obtaining natural, biologically active indole compounds involves isolating them from their natural sources or preparing them synthetically. 3-Substituted indoles repre-sent an emerging structural class of marine alkaloids based on their high degree of biological activity. 3-Acetyl indole is an important core used as a starting material for synthesizing many bioactive indole alkaloids. (5-Indole)oxazole alkaloids, β-carboline alkaloids, bis-in-dole alkaloids, chuangxinmycin, meridianine, and (±) indolemycin are the most important indole alkaloids that are prepared starting from 3-acety indole. The present review provides comprehensive information on the structures and the synthesis of bioactive indole alkaloids utilizing 3-acetyl indole and its derivatives as starting compounds. Additionally, it also spot-lights the diverse biological activities of these compounds.

Persistent tissue-specific resident microbiota in oysters across a broad geographical range.

Marine animals often harbour complex microbial communities that influence their physiology. However, strong evidence for resident microbiomes in marine bivalves is lacking, despite their contribution to estuarine habitats and coastal economies. We investigated whether marine bivalves harbour stable, resident microorganisms in specific tissues or if their microbiomes primarily consist of transient members reflecting the environmental microbial pool. Conducting a latitudinal study of wild eastern oysters (Crassostrea virginica) along the East Coast of the United States, we aimed to identify resident microorganisms that persist across a wide geographical range. Our results revealed that microbial communities in seawater and sediment samples followed latitudinal diversity patterns driven by geographic location. In contrast, oyster-associated microbiomes were distinct from their surrounding environments and exhibited tissue-specific compositions. Notably, oyster microbiomes showed greater similarity within the same tissue type across different geographic locations than among different tissue types within the same location. This indicates the presence of tissue-specific resident microbes that persist across large geographical ranges. We identified a persistent set of resident microbiome members for each tissue type, with key microbial members consistent across all locations. These findings underscore the oyster host's role in selecting its microbiome and highlight the importance of tissue-specific microbial communities in understanding bivalve-associated microbiomes.

Speed dependence, sources, and directivity of small vessel underwater noise.

Small vessels (<10 m) radiate underwater noise in sensitive coastal environments, but there is insufficient knowledge of their noise radiation. Through detailed measurements of seven small boats and a jet ski in a shallow water environment on the Swedish west coast, this study presents results on the speed dependence of small vessel underwater noise, its sources, and its directivity. For vessels with planing hulls, broadband source levels increase with speed until planing is attained. When planing, source level dependence on speed is weak. A detailed noise source analysis of one vessel showed that at low speed, tonals from the engine dominate the noise radiation, whereas at higher speeds, propeller tonals and broadband noise dominate. Noise radiation into different horizontal angles shows little angle dependence, and noise levels relative to the closest point of approach show a similar pattern across all investigated vessels. Received noise levels at approximately 100 m range are not high enough to cause hearing impairment in marine animals, but fast-moving small vessels may cause behavioural reactions or stress responses across several marine animal groups.