Marine Habitats Research Articles

Morphological, molecular and 3D synchrotron X-ray tomographic characterizations of Helicascus satunensis sp. nov., a novel mangrove fungus

A new species of Helicascus satunensis sp. nov. was collected on mature dead fruits of the Nypa palm in Satun Province, southern Thailand. Its morphological characteristics are similar to those of the genus Helicascus. Recently, a genus Helicascus with three species from marine habitats worldwide was studied. The morphology of this fungus was investigated and combined with multigene sequence analyzes of small subunit (SSU), large subunit (LSU), internal transcribed spacer (ITS) ribosomal DNA, translation elongation factor 1-alpha (TEF-1α) and RNA polymerase II (RPB2) genes. Morphologically, H. satunensis sp. nov. is characterized by semi-immersed, lenticular ascomata, multilocules, a bitunicate ascus and smooth, obovoid, dark brown ascospores that are one-septate and unequally two-celled. In addition, 3D visualization using synchrotron X-ray tomography was performed to investigate the interaction between fruiting body and substrata. Molecular phylogeny with multigene revealed that H. satunensis sp. nov. belongs to the family Morosphaeriaceae, order Pleosporales, class Dothideomycetes. Furthermore, H. satunensis sp. nov. forms a well-supported clade with Helicascus species described from marine habitats. Based on the unique morphological and molecular evidence, we propose this fungus, H. satunensis sp. nov., as a new species for Helicascus.

Migration patterns, habitat use and genetic origins of sea trout (Salmo trutta) in Norfolk chalk streams: implications for management of a mixed stock fishery

Sea trout, the anadromous ecotype of the species Salmo trutta, are subject to multiple threats, including exploitation and aquaculture impacts in the marine environment, habitat fragmentation and pollution in freshwaters, loss of genetic resilience due to interbreeding with hatchery strains and environmental change. Small streams contribute relatively little biomass to European sea trout stocks but are thought to be important in maintaining genetic diversity and therefore wider population resilience. The current study combined data from acoustic telemetry, stable isotopes, genetics and scalimetry to assess the current status of sea trout in the rivers Stiffkey and Glaven, two locally important chalkstreams in East Anglia, UK, to provide an evidence base for future management. The incidence of anadromy was low, and most sea trout were near migrants, residing in the lower reaches of rivers and close to the tidal outfalls. A small number migrated to the North Sea where they were vulnerable to exploitation in the coastal fishery, which comprises a mixed stock. Straying between the two rivers was recorded among 10% of sea trout, leading to apparent high gene flow. Nonetheless, genetic data also demonstrated structuring of River Glaven trout into two distinct groups. Quantification of patterns of freshwater and estuarine habitat use, and of passage at cross-channel obstructions, was used to identify where remedial measures such as habitat restoration would be most effectively targeted. Findings are discussed in the context of local supplementary stocking and the potential impact of the nearshore fishery on limited and vulnerable small stream anadromous trout populations.

Rapid, detrimental response of estuarine benthic macrofauna communities to pollution by littered cigarette filters and e-liquid

Cigarette butts are amongst the most littered single-use plastics on coasts, yet their impacts on marine ecosystems, especially on a community level, are not well understood. Recently, e-cigarettes have become popular and are a novel litter item in marine habitats. Preliminary research indicates that e-liquid can harm individual organisms, but few studies have been done and none on a community level. In a mesocosm experiment, we tested the impacts of cigarette butts (0.25, 1 butt L−1) or e-liquid (1 mL L−1) on infaunal invertebrate communities using intact sediment cores. After two weeks, the abundance of polychaetes, bivalves, and gastropods was significantly reduced in mesocosms with 1 cigarette butt L−1 compared with controls. Exposure to e-liquid resulted in severe oxygen depletion (<1 mg L−1) and almost complete mortality of sediment infauna after just four days. As litter, cigarette butts and disposable e-cigarettes both pose a threat to estuarine biodiversity.

Effects of Oceanographic Conditions on Fishery Distribution: A Case Study of Chub Mackerel (Scomber japonicus) in Northeastern Taiwan

Changes in oceanographic conditions can affect species distribution in marine habitats. Global climate change may negatively influence the oceanographic factor–species distribution relationship. Here, we assessed the influence of oceanographic conditions on chub mackerel (Scomber japonicus) distribution in northeastern Taiwan by constructing and using a habitat ensemble model incorporating chub mackerel fishery, climatic oscillation, and oceanography data. Our results indicated that the chub mackerel catch was mainly influenced by the Western Pacific Oscillation. Moreover, sea-surface height and mixed-layer depth exerted the most and least significant effects on chub mackerel distribution, respectively. The chub mackerel catch rate peaked in the study area with a sea-surface temperature of 29°C, sea-surface chlorophyll of 0.25 mg/m3, sea-surface salinity of 33.7 psu, and SSH of 0.575 m. Chub mackerel was the most widely distributed in the area between 25°N, 120.5°E and 26.2°N, 121.5°E. Our findings can be used to develop critical adaptation plans for managing chub mackerel fisheries in the northeastern waters of Taiwan. Considering changing climate conditions globally, the incorporation of this knowledge into managerial strategies may aid decision-makers in protecting not only other ocean fisheries but also individuals dependent on them.

Resource selection by a megaomnivore in a marine foraging habitat

AbstractHabitat‐based approaches to animal conservation are bolstered by an understanding of resource selection, that is, use of resources (i.e., habitat features) relative to their availability in the environment. Quantifying resource selection is especially valuable when data characterizing animal space use are limited, as is often the case with mobile and/or cryptic species. Documenting associations with habitat features can better inform management in space in time, while also revealing key insight into movement ecology and behavior. Here, we evaluate resource selection by a megaomnivore whose highly mobile nature within marine habitats has resulted in an incomplete understanding of drivers of space use. We used satellite telemetry to track 29 green turtles (Chelonia mydas) from an eastern Pacific foraging aggregation in San Diego Bay, California, USA during 2013–2023. Tracking produced 5023 Fastloc‐GPS points which we used to model selection for local environmental resources relative to their availability. We employed logistic models to evaluate associations with seagrass, bathymetry, and water temperatures, implementing a framework that additionally allowed us to explore the roles of season, diel period, and turtle body size. Our methods demonstrate an approach for down‐weighting observations according to assumed telemetry error and autocorrelation. Results from fine‐scale resource selection models provide evidence that green turtles in San Diego Bay select for eelgrass meadows (Zostera marina), particularly during the warmest months of the year, but the strength of this selection changes from day to night. We additionally found day–night shifts in depth and temperature selection that changed with turtle body size and season. We discuss these findings in the context of diel patterns in resting and foraging behavior in addition to seasonal changes in thermally sensitive metabolic rates. Our study documents resource associations and provides quantitative information for the management of sea turtle foraging populations and their habitats. We offer key insight into habitat use by green turtles in the eastern Pacific at a pivotal time when multiple indicators point to population growth and expansion within the region.

Atlas of Pacific sand lance (Ammodytes personatus) benthic habitat – application of multibeam acoustics and directed sampling to identify viable subtidal substrates

Defining and delineating species distribution and critical habitat is critical to informed management and conservation. This process is complicated in marine environments, where detection of marine taxa and characterization of marine habitat is more difficult. Small pelagic fishes and forage fishes are particularly challenging, though insights may be more accessible in species highly dependent on particular habitat. Pacific sand lance (Ammodytes personatus) is a common and ecologically-important pelagic fish that relies on specific benthic sediments for rest and refuge from predation. We applied multibeam echosounder (MBES) bathymetric data to develop high-definition benthic habitat maps and implemented multiyear sampling to assess potential habitat for sand lance via in situ sampling of sediments. We also applied acoustic Doppler current profilers (ADCP) data and tidally-driven volume-based ocean models to measure current strength and to visualize currents. We leveraged this data to further define and describe habitat for this important forage species. Sediment transport processes were mapped and areas of dispersal, embedment, and accumulation were evaluated. Dynamic bedform habitats, banner banks and glacial banks were identified as potential habitat and sampled for fish presence, density and sediment composition. In the central Salish Sea, approximately 25% of benthic substrates represent potential sand lance habitat. Sand lance prevalence and density correlated with substrate type and sediment coarseness. Densities were highest in areas of coarse grain sediments and presence was limited by fine particulates, such as silt and mud. Tidal currents appear important. Presence and densities of sand lance were correlated with current velocity and distance from current flow path. Nearly all viable sites were located on the immediate margins of high flow (< 0.16 km from tidal currents with max speed of 1.72-2.58 m/s). While both flood and ebb were important, processes related to flood were dominant. Viable habitat was not constrained by depth. These results inform a developing atlas for sand lance in the central Salish Sea, provide new insights to subtidal sand lance habitat, characterize conditions that create and maintain subtidal benthic habitat, and provide a template for mapping habitat for this species in the coastal Pacific Ocean.

Kelp forests versus urchin barrens: a comparison of ecosystem functions and services provided by two alternative stable marine habitats.

Kelp forests and urchin barrens are two stable states in rocky reef ecosystems, each providing unique ecosystem functions like habitat for marine species and primary production. While studies frequently show that kelp forests support higher levels of some ecosystem functions than urchin barren habitats, no research has yet compared average differences. To address this gap, we first conducted a meta-analysis of studies that directly compared the ecosystem functions, services and general attributes provided by each habitat. We also compiled individual studies on ecosystem properties from both habitats and qualitatively assessed the benefits provided. The meta-analysis included 388 observations from 55 studies across 14 countries. We found that kelp forests consistently delivered higher levels of ecosystem properties such as biodiversity, species richness, abalone abundance and sea urchin roe quality. Urchin barrens supported higher urchin density and crustose coralline algae cover. The qualitative review further supported these findings, showing that kelp forests ranked higher in 11 out of 15 ecosystem properties. These findings can help guide decisions on managing rocky reef habitats and demonstrate the benefits of preserving or expanding kelp forests.

Ecological processes shaping highly connected bacterial communities along strong environmental gradients.

Along the river-sea continuum, microorganisms are directionally dispersed by water flow while being exposed to strong environmental gradients. To compare the two assembly mechanisms that may strongly and differently influence metacommunity dynamics, namely homogenizing dispersal and heterogeneous selection, we characterized the total (16S rRNA gene) and putatively active (16S rRNA transcript) bacterial communities in the Pearl River-South China Sea Continuum, during the wet (summer) and dry (winter) seasons using high-throughput sequencing. Moreover, well-defined sampling was conducted by including freshwater, oligohaline, mesohaline, polyhaline, and marine habitats. We found that heterogeneous selection exceeded homogenizing dispersal in both the total and active fractions of bacterial communities in two seasons. However, homogeneous selection was prevalent (the dominant except in active bacterial communities during summer), which was primarily due to the bacterial communities' tremendous diversity (associated with high rarity) and our specific sampling design. In either summer or winter seasons, homogeneous and heterogeneous selection showed higher relative importance in total and active communities, respectively, implying that the active bacteria were more responsive to environmental gradients than were the total bacteria. In summary, our findings provide insight into the assembly of bacterial communities in natural ecosystems with high spatial connectivity and environmental heterogeneity.

An overview on the production, management and impact of microplastic contamination on marine species and marine environments: A review

The purpose of this paper is to review and evaluate published literature on the production, management and impact of microplastic contamination on marine species and marine environments. A systematic method was utilized to access research works of literature on “production, management and impact of microplastic contamination on marine species and marine environments”. A total of Sixty-two (62) research papers published between the years 1972 to 2022 was accumulated and used for this review. A subjective approach was used to select the topics: production, management and impact of microplastic contamination. In this paper, four (4) effects of microplastics on organisms and the environment was assessed. Additionally, the formation and classification of microplastics were evaluated. Subsequently, the paper delves into the production and the management of global plastic production as well as the sources of contamination. Further, this review assessed the quantity of microplastics in the gastrointestinal tract and edible muscles of various fish species. A mini checklist of sixty-one (61) fish species from thirty (30) families dwelling in nine (9) different marine habitats, all contaminated by microplastics was also presented in this review. Moreover, possible solutions to overcome the impact of microplastics on organisms and aquatic environments were also mentioned in this article. The published works of literature established that the global plastic production is constantly increasing with a growing world population thus leading to mismanagement of plastic resources and introducing them to the environment. Microplastics can cause serious complications in humans, marine organisms such as fishes, crustaceans, marine mammals and sea birds and even contribute to the degradation of mangrove forests and the coastal environment. This review highlights the fact that more extensive studies on the impact of microplastic contamination in organisms and the environment should be done in neotropical countries since there is a dearth and gaps of such information on research and published data in these biodiversity rich regions.

Assessing microplastic abundances in freshwater fishes in a subtropical African reservoir

Microplastics are emerging pollutants of global concern, and their presence in the aquatic environment poses a serious risk for aquatic biota. While many studies have been conducted on the presence of microplastics in marine habitats, little research has been done in freshwater African reservoirs on microplastic pollution and their impacts on fish within the subtropical regions. To bridge this gap, the current study investigated microplastic abundances and distribution in freshwater fish within Nandoni reservoir, South Africa, across two seasons (i.e., hot–wet, cool–dry). Fish were randomly sampled using seine and gill nets from seven sites within the reservoir. In the laboratory, fish were then sorted according to taxa before dissecting them to remove the gills and the gastrointestinal tract (GIT). The organs were digested using hot hydrochloric acid and hydrogen peroxide, and the microplastics were classified according to their colours and shapes. Among the 94 fishes (i.e., 8 species) examined, microplastics were detected in 86.6% of the eight species caught. Microplastics were dominant in the gills and GIT during the cool–dry and hot–wet seasons, respectively. High microplastic abundances were found in the gills of Micropterus salmoides and the GIT of Coptodon rendalli, where fibres and the transparent colour were the most dominant. The results further showed high microplastic abundances in benthopelagic feeders highlighting that habitat influences fish consumption of microplastics whether directly or indirectly. Significant differences were observed in the feeding zone and season for all microplastic types. Microplastic sources in the reservoirs could be due to anthropogenic activities such as illegal dumping, fishing, and agriculture. Thus, there is a need for further investigation into the relation of fish weight, fish sex and body in relation to microplastic pollution. The highlighted ecological factors should be taken into consideration for future research and management actions aimed at mitigating and protecting the negative impacts of microplastic pollution on environmental and human health.

An appropriate artificial intelligence technique for plastic materials recycling using bipolar dual hesitant fuzzy set

Plastic recycling has become more important than ever as the globe struggles with growing environmental issues. This research explores the significant environmental impact of recycling plastic and its growing relevance. The pervasive material known as plastic presents a complex risk to both human health and ecosystems in contemporary life. It exacerbates problems including marine pollution, habitat damage, and wildlife entanglement because of its persistence in landfills and seas, which leads to serious ecological deterioration. In addition, producing plastic uses a lot of energy and produces a lot of greenhouse gas emissions, which exacerbate climate change. Through the use of multi-criteria decision making (MCDM), this study emphasizes how vital it is to support recycling activities in order to protect the environment and promote a sustainable future. The elimination and choice ex-pressing reality (ELECTRE) approach is used to rank the alternatives in this proposed research study that employs bipolar dual hesitant fuzzy sets (BDHFs). The most efficient and versatile outranking method for making decisions is the BDHF-ELECTRE approach. The weights of environment, economic, social, technical, and finally safety is computed using the entropy distance metric. The economic factor received the highest score of 0.2945 among the other factors since economic considerations are crucial in choosing the most efficient plastic recycling method, as they ensure sustainability, cost-effectiveness, resource allocation, and overall feasibility in managing plastic waste. The decision-makers determined that the mechanical recycling approach ought to be prioritized over all others for the efficient recycling of plastic waste. The robustness of the system is examined in the sensitive and comparative analyses. The proposed MCDM technique thus presents a viable solution, mitigating the adverse effects of plastic waste by conserving resources, reducing energy consumption, and curbing pollution.

Optical Remote Sensing Methods for Floating Marine Debris Detection – Review and Bibliography Analysis

In the last several decades, the disposal and accumulation of debris in the marine and coastal environment has been one of the biggest and fastest-growing threats to the health of the world's oceans. Marine debris is present in all marine habitats and represents a great danger to global environmental and human health. Therefore, this paper aims to support efforts to achieve Good Environmental Status with respect to marine debris in all oceans and seas. The application of optical remote sensing methods for floating marine debris detection was briefly reviewed and the bibliometric analysis of the professional and scientific literature elaborated upon. In the overview part, previously used marine debris detection methods have been listed. The WoSCC (Web of Science Core Collection) and Scopus databases were considered, and the R Studio Bibliometrix and Biblioshiny software tools used for bibliometric analysis. 209 documents that can be classified into 43 research fields were identified in the two databases. Approximately 20% of the documents were published in two journals: the Marine Pollution Bulletin and Remote Sensing. Marine debris research was mainly published in the USA, Portugal, Italy, the United Kingdom, Germany, and China. A total of 54 countries participated in the publication of documents and it should be emphasized that all countries have shown great interest in international cooperation during the scientific research on marine debris. Scientific research on marine debris was found to have increased significantly since 2017, which is highly important for the protection of the environment and human health.

Effects of Offshore Wind Farms: Environmental and Social Perspectives from Uruguay

The installation of offshore wind farms is rising, driven by the goal of changing the global energy matrix. However, many of their possible impacts are still unknown. Increased noise levels, disruptions to food chains, pollution due to traffic, and impacts on fishing communities and tourism are all potential effects to consider. Marine habitats are essential carbon dioxide sinks. Therefore, losing marine biodiversity due to offshore wind farms can be counterproductive in mitigating climate change. Balancing biodiversity conservation, wind potential, and political interests is challenging. Today, Uruguay has significantly decreased the fossil share in its electricity generation, incorporating electricity generation from wind, solar, and biomass energy alongside hydroelectricity. In line with this, the country’s Hydrogen Roadmap highlights green hydrogen as relevant, potentially serving as a fuel for both domestic and export transportation. Combining the country’s strong base of wind energy production experience with its sustainable policy, it plans to implement offshore wind farms to produce green hydrogen, making studies of its impacts crucial. This paper reviews the current social and environmental information on the Uruguayan coastal habitat, analyzes onshore wind farms’ ecological studies, and examines offshore wind farms’ global environmental and social impacts. Finally, it proposes studies for environmental approval of offshore wind farms.

Hydromechanical properties of metachronal swimming in polychaetes

Free-swimming polychaetes are common in marine habitats and exhibit a unique form of swimming whereby a metachronal wave occurs simultaneously with a bending body wave. This body wave is unusual among swimming animals because it travels in the same direction as the animal’s swimming direction. However, we currently lack a mechanistic understanding of this unusual form of locomotion. In this study we use a combination of high-speed, high-resolution video and particle image velocimetry (PIV) to quantify kinematics and fluid dynamics for three species of swimming polychaetes, spanning two orders of magnitude in size. We find that in all species, flows generated by metachronal waves of parapodia dominate while typical flows associated with body bending is absent. However, the parapodia are less flexible than propulsive structures in other metachronal swimmers. This creates a localized, but substantial upstream flow during the recovery stroke. Using body bending, the recovery stroke can occur mostly beneath the bulk flow from the power strokes, resulting in minimal inference while the subsequent power stroke can benefit from the pressure field generated during recovery. These results may have implications for future vehicle designs that incorporate metachronal locomotion.

Insights into PFAS contaminants before and after sewage discharges into a marine protected harbour

Per and polyfluoroalkyl substances (PFAS) and their degradation products are a concern to human and ecosystem health. Wastewater treatment plants are not efficient at removing PFAS compounds and are thought to be a major source of these compounds to marine environments. The sewerage infrastructure in the UK, has over 20,000 combined stormwater overflows (CSOs). These CSOs are relief values whereby untreated wastewater can discharge under permit from the Environment Agency with exceptional rain/snowfall conditions. CSOs discharged 3.6 million monitored hours of untreated wastewater into English rivers and coasts in 2023. Concerns have been raised about the proximity of these CSO discharges to highly protected marine habitats. This study is the first to determine that PFAS concentrations are elevated in a highly protected marine bay (Langstone Harbour, England) following recent sewage releases compared to an extended period without discharge. Analysis was carried out into a suite of 54 PFAS compounds of which only one (PFHpA) was detectable above LOD prior to discharges but 8 afterwards. These included banned PFOS (Linear and Branched 8.6 ng/L ∓ 0.90) and PFOA (2.9 ng/L ∓ 0.29) which were above annual average EQS for inland and ‘other’ surface waters. Most of the PFAS compounds detected doubled in concentration above LODs. These two-fold increases we discuss are likely conservative estimates based on the use of LODs and tidal conditions. Additional Oysters (Crassostrea gigas) and Seaweed (Fucus vesiculosus) were taken revealing high concentrations of the shorter chain PFBA (6.99μg/kg ∓ 2.42 ww) in seaweed samples. These seaweeds were calculated to have conservative bioaccumulation factors (BAF) > 6000 for PFBA indicating these algae might be an important reservoir of some PFAS contamination. We discuss these results in the context of the largescale discharges of untreated wastewater nationally and globally, and call upon a need for a better understanding of the transfer of PFAS contaminants into marine food chains.

Coastal marine habitats deterioration according to users’ perception: the case of Cap de Creus Marine Protected Area (NE Spain)

Assessing how different users of a Marine Protected Area perceive environmental changes can contribute to design management strategies. We assess how locals and tourists perceive environmental changes in the Cap de Creus protected area (NW Mediterranean, Spain). To identify locally perceived changes, we first conducted semi-structured interviews with locals (n = 38). Reported environmental changes were then used to construct a survey applied to locals and tourists (n = 427). In semi-structured interviews, environmental changes were the least reported changes compared to economic and social changes; reports of negative environmental changes dominated over reports of positive environmental changes. Overall, all survey participants reported a decline of the health status of the local environment, with locals displaying higher levels of agreement with statements referring to coastal environmental deterioration than tourists. The predominance of responses reporting economic versus environmental changes can be explained by the recent radical transformation of the area towards tourism. Reports of coastal marine area deterioration are in line with available instrumental data. Higher levels of agreement with statements referring to environmental deterioration among locals than among tourists highlight the importance of people’s connection with nature to assess change. Considering that Cap de Creus has been protected for more than two decades, our findings raise concerns regarding its ongoing deterioration and underscore the importance of monitoring the effectiveness of marine protection to modulate management strategies.

The marine environmental microbiome mediates physiological outcomes in host nematodes.

Nematodes are the most abundant metazoans in marine sediments, many of which are bacterivores; however, how habitat bacteria affect physiological outcomes in marine nematodes remains largely unknown. RESULTS: Here, we used a Litoditis marina inbred line to assess how native bacteria modulate host nematode physiology. We characterized seasonal dynamic bacterial compositions in L. marina habitats and examined the impacts of 448 habitat bacteria isolates on L. marina development, then focused on HQbiome with 73 native bacteria, of which we generated 72 whole genomes sequences. Unexpectedly, we found that the effects of marine native bacteria on the development of L. marina and its terrestrial relative Caenorhabditis elegans were significantly positively correlated. Next, we reconstructed bacterial metabolic networks and identified several bacterial metabolic pathways positively correlated with L. marina development (e.g., ubiquinol and heme b biosynthesis), while pyridoxal 5'-phosphate biosynthesis pathway was negatively associated. Through single metabolite supplementation, we verified CoQ10, heme b, acetyl-CoA, and acetaldehyde promoted L. marina development, while vitamin B6 attenuated growth. Notably, we found that only four development correlated metabolic pathways were shared between L. marina and C. elegans. Furthermore, we identified two bacterial metabolic pathways correlated with L. marina lifespan, while a distinct one in C. elegans. Strikingly, we found that glycerol supplementation significantly extended L. marina but not C. elegans longevity. Moreover, we comparatively demonstrated the distinct gut microbiota characteristics and their effects on L. marina and C. elegans physiology. Given that both bacteria and marine nematodes are dominant taxa in sedimentary ecosystems, the resource presented here will provide novel insights to identify mechanisms underpinning how habitat bacteria affect nematode biology in a more natural context. Our integrative approach will provide a microbe-nematodes framework for microbiome mediated effects on host animal fitness.

How marine are Marine Stramenopiles (MAST)? A cross-system evaluation.

Marine Stramenopiles (MAST) were first described two decades ago through ribosomal RNA gene (rRNA gene) sequences from marine surveys of microbial eukaryotes. MAST comprise several independent lineages at the base of the Stramenopiles. Despite their prevalence in the ocean, the majority of MAST diversity remains uncultured. Previous studies, mainly in marine environments, have explored MAST's cell morphology, distribution, trophic strategies, and genomics using culturing-independent methods. In comparison, less is known about their presence outside marine habitats. Here, we analyze the extensive EukBank dataset to assess the extent to which MAST can be considered marine protists. Additionally, by incorporating newly available rRNA gene sequences, we update Stramenopiles phylogeny, identifying three novel MAST lineages. Our results indicate that MAST are primarily marine with notable exceptions within MAST-2 and MAST-12, where certain subclades are prevalent in freshwater and soil habitats. In the marine water column, only a few MAST species, particularly within clades -1, -3, -4 and -7, dominate and exhibit clear latitudinal distribution patterns. Overall, the massive sequencing dataset analyzed in our study confirms and partially expands the previously described diversity of MASTs groups and underscores the predominantly marine nature of most of these uncultured lineages.

How SATURN is studying the impact of ship noise on the behaviour, health, energetics, and populations of aquatic organisms

The EU-funded SATURN project contributes to improve our understanding of the effects of ship noise on aquatic animals through several studies. Assessing the effects of underwater noise on aquatic animals is complex due to the diversity of taxa involved, each with their own sound sensitivity in terms of spectral and temporal aspects, as well as behavioural and physiological sensitivity to acoustic disturbances. To conduct exposure experiments on fish and invertebrates that are sensitive to the particle motion component of sound, we have developed innovative laboratory setups. Invertebrates are studied in an AQUAVIB exposure chamber, while migratory fish species are studied in a MIGRADOME swimming tunnel. The project also focuses on three marine mammal species: porpoises, pilot whales, and harbour seals. These species provide broad biological coverage of acoustic specialisations and relevant European habitats. Field data were collected using tags deployed on wild animals and dose-response relationships of marine mammal behaviour and energetics were established as a function of real-world exposure to ship noise. The effects on porpoise population are assessed using the updated DEPONS model. The results of SATURN will be transferred to stakeholders to inform management actions for the mitigation of the effects of acoustic pollution in marine habitats.

Seabed classification in Bahía de Navidad in the Mexican Central Pacific using a single-beam echosounder

This study proposes a methodology for characterizing subtidal habitats along rocky coastlines and adjacent seabeds in the epipelagic zone using a 120 kHz single-beam echo sounder (SBES). The data collected at depths of 15 to 80 m in Bahía de Navidad on the Mexican Central Pacific coast were postprocessed and classified using QTC Impact™ software to obtain three acoustic classes.Using the classified data and ArcMap™ software, a bathymetric map was built for the selection of 19 sampling points for ground truthing and granulometric analysis to create a matrix further subjected to two ordination analyses: principal component analysis (PCA) and nonmetric multivariate scaling analysis (MDS). Additionally, the matrix was adapted into a dummy matrix, which was subsequently used to conduct a Pearson correlation coefficient test.The analyses revealed a strong correlation between the medium-deep-zone acoustic class (20 m to 50 m) and the medium-grain-size sand substrate, as well as a high correlation between the deep-zone acoustic class (50 to 80 m) and finer sand substrates. This study demonstrated the potential of using affordable echosounders as a reliable and feasible alternative for characterizing marine habitats, especially for research institutions in developing countries with limited financial resources.