Documenting large-scale patterns of animals in the ocean and determining the drivers of these patterns is needed for conservation efforts given the unprecedented rates of change occurring within marine ecosystems. We used existing datasets from two global expeditions, Tara Oceans and Malaspina, that circumnavigated the oceans and sampled down to 4000 m to assess metazoans from environmental DNA (eDNA) extracted from seawater. We describe patterns of taxonomic richness within metazoan phyla and orders based on metabarcoding and infer the relative abundance of phyla using metagenome datasets, and relate these data to environmental variables. Arthropods had the greatest taxonomic richness of metazoan phyla at the surface, while cnidarians had the greatest richness in pelagic zones. Half of the marine metazoan eDNA from metagenome datasets was from arthropods, followed by cnidarians and nematodes. We found that mean surface temperature and primary productivity were positively related to metazoan taxonomic richness. Our findings concur with existing knowledge that temperature and primary productivity are important drivers of taxonomic richness for specific taxa at the ocean\'s surface, but these correlations are less evident in the deep ocean. Massive sequencing of eDNA can improve understanding of animal distributions, particularly for the deep ocean where sampling is challenging.

Four new compounds, including one drimane sesquiterpene lactone (1), one isocoumarin (2), one coumarin (3), and a new natural product (4), as well as fourteen known compounds were obtained from a deep-sea derived Cladosporium sp. SCSIO 41318. The structures of the new compounds were determined using extensive NMR and HRESIMS spectroscopic analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction measurements. Biological assays showed that compounds (1, 6, 7, 9-12, 14, 15, 17, 18) exhibited varying degrees of antimicrobial activity against the tested human pathogenic bacteria and plant pathogenic fungi. Besides, penicitrinone A (11) and penicitrinol A (12) displayed weak antitumor activities against the 22Rv1 cell line.

In the deep-sea environment, the volume available for an in-situ gene sequencer is severely limited. In addition, optical imaging systems are subject to real-time, large-scale defocusing problems caused by ambient temperature fluctuations and vibrational perturbations. To address these challenges, we propose an edge detection algorithm for defocused images based on grayscale gradients and establish a defocus state detection model with nanometer resolution capabilities by relying on the inherent critical illumination light field. The model has been applied to a prototype deep-sea gene sequencing microscope with a 20× objective. It has demonstrated the ability to focus within a dynamic range of ±40 μm with an accuracy of 200 nm by a single iteration within 160 ms. By increasing the number of iterations and exposures, the focusing accuracy can be refined to 78 nm within a dynamic range of ±100 μm within 1.2 s. Notably, unlike conventional photoelectric hill-climbing, this method requires no additional hardware and meets the wide dynamic range, speed, and high-accuracy autofocusing requirements of deep-sea gene sequencing in a compact form factor.

Sciadonus alphacrucis Melo, Gomes, Møller & Nielsen, 2022 is a rare deep-sea species, previously known from only two specimens collected off São Paulo State, southeastern Brazil, in the western South Atlantic. Herein, we report a new specimen of S. alphacrucis collected on the continental slope off Santa Catarina State, southern Brazil, thereby extending its known distribution by 420 km. Additionally, we provide the new meristic and morphometric data, the molecular identification using sequences of the cytochrome c oxidase subunit I (COI), an updated distribution map, and a discussion of troglomorphic traits.

With 289 known species in 51 genera, the ophidiiform family Ophidiidae together with their relatives from the Carapidae (36 species in eight genera) of the same suborder Ophidioidei dominate the deep sea, but some occur also in shallow water habitats. Despite their high species diversity in the deep sea and wide bathymetric distributions, their phylogenetic relationships and evolution remain unexplored due in part to sampling difficulties. Thanks to the biodiversity exploratory program entitled \"Tropical Deep-Sea Benthos\" and joint efforts between Taiwan and French teams for sampling from different localities across the Indo-West Pacific over the last two decades, we are able to compile comprehensive datasets for investigations. In this study, 59 samples representing 36 of 59 known ophidioid genera are selected and used to construct a multi-gene dataset to infer the phylogenetic relationships of ophidioid fishes and their relatives. Our results reveal that the Ophidiidae forms a paraphyletic group with respect to the Carapidae. The four main clades of Ophidioidei resolved are the (1) clade comprising species from the subfamily Brotulinae; (2) clade that includes species in the genera Acanthonus and Xyelacyba; (3) clade grouping Hypopleuron caninum with species from the family Carapidae; and (4) clade containing the species in the subfamily Brotulotaenilinae, Neobythitinae (in part), and Ophidiinae. Accordingly, we suggest the following new revisions based on our results and proposed morphological diagnoses. The subfamily Brotulinae should be elevated to the family level. The genera Xyelacyba and probably Tauredophidium (unsampled in this study) should be included in the newly established family Acanthonidae with Acanthonus. The families Carapidae and Ophidiidae are re-defined. Our time-calibrated phylogenetic and ancestral depth reconstructions enable us to clarify the evolutionary history of ophidiiform fishes and infer past patterns of species distributions at different depths. While Ophidiiformes is inferred to have originated in shallow waters around 96.25 million years ago (Mya), the common ancestor to the Ophidioidei is inferred to have invaded the deep sea around 90.22 Mya, the dates coinciding with the global anoxic event of the OAE2. The observed bathymetric distribution patterns in Ophidioidei most likely point to the mesopelagic zone as the center of origin and diversification. This was followed by multiple events of depth transitions or range expansions towards either shallower waters or greater depth zones, which were likely triggered by past climate changes during the Paleogene-Neogene.

From sea shores to the abysses of the deep ocean, marine ecosystems have provided humanity with valuable medicinal resources. The use of marine organisms is discussed in ancient pharmacopoeias of different times and geographic regions and is still deeply rooted in traditional medicine. Thanks to present-day, large-scale bioprospecting and rigorous screening for bioactive metabolites, the ocean is coming back as an untapped resource of natural compounds with therapeutic potential. This renewed interest in marine drugs is propelled by a burgeoning research field investigating the molecular mechanisms by which newly identified compounds intervene in the pathophysiology of human diseases. Of great clinical relevance are molecules endowed with anti-inflammatory and immunomodulatory properties with emerging applications in the management of chronic inflammatory disorders, autoimmune diseases, and cancer. Here, we review the historical development of marine pharmacology in the Eastern and Western worlds and describe the status of marine drug discovery. Finally, we discuss the importance of conducting sustainable exploitation of marine resources through biotechnology.

The hadopelagic environment remains highly understudied due to the inherent difficulties in sampling at these depths. The use of sediment environmental DNA (eDNA) can overcome some of these restrictions as settled and preserved DNA represent an archive of the biological communities. We use sediment eDNA to assess changes in the community within one of the world\'s most productive open-ocean ecosystems: the Atacama Trench. The ecosystems around the Atacama Trench have been intensively fished and are affected by climate oscillations, but the understanding of potential impacts on the marine community is limited. We sampled five sites using sediment cores at water depths from 2400 to ~8000 m. The chronologies of the sedimentary record were determined using 210Pbex. Environmental DNA was extracted from core slices and metabarcoding was used to identify the eukaryote community using two separate primer pairs for different sections of the 18S rRNA gene (V9 and V7) effectively targeting pelagic taxa. The reconstructed communities were similar among markers and mainly composed of chordates and members of the Chromista kingdom. Alpha diversity was estimated for all sites in intervals of 15 years (from 1842 to 2018), showing a severe drop in biodiversity from 1970 to 1985 that aligns with one of the strongest known El Niño events and extensive fishing efforts during the time. We find a direct impact of sea surface temperature on the community composition over time. Fish and cnidarian read abundance was examined separately to determine whether fishing had a direct impact, but no direct relation was found. These results demonstrate that sediment eDNA can be a valuable emerging tool providing insight in historical perspectives on ecosystem developments. This study constitutes an important step toward an improved understanding of the importance of environmental and anthropogenic drivers in affecting open and deep ocean communities.

In light of the low dissolved oxygen concentration in the deep sea, the corrosion mechanisms of the high entropy alloy (HEA) AlCoCrFeNi in artificial seawater with varying oxygen concentrations (2.0, 4.0, 7.0 mg/L) were studied. As the oxygen concentration decreases, the alloy\'s free corrosion potential decreases, and at 2.0 mg/L, the corrosion rate is 421 times higher than that at 7.0 mg/L. The corrosion form transforms from pitting to uniform corrosion. The primary reasons for this are the passivation film is thin under low oxygen concentration conditions, as well as the preferential dissolution of the alloy elements Al and Ni due to their high activity and \"local acidizing\" properties, respectively. In designing a super corrosion-resistant high entropy alloy for use in the deep sea, it is advisable to avoid the use of element Al and to add Ni with caution.

The determination of metal(loid) (As, Fe, Al, Sr, Zn, Pb, Mn, Cu, Cr, and Cd) levels in the muscle tissue of 23 different deep-sea bony fish sampled off Mersin Bay (NE Levantine Basin) and the assessment of health risks for human consumption were aimed. Tissue metal(loid) concentrations were determined as dry weight and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The tissue metal(loid) concentrations (µg g dw) were converted to wet weight prior to health risk assessment calculations. Standard mathematical formulas were used to determine the health risk assessment. There was a statistically significant difference between the fish species in terms of tissue metal(loid) levels (p < 0.05). The highest metal(loid) level was found in C. sloani among other species. As and Fe had the highest and Cd the lowest tissue concentrations in the examined species (p < 0.05). The relationships between the metal(loid)s analyzed in the tissue were significant (p < 0.01;0.05). Fe had an antagonistic effect with Cd, while other metal(loid)s had a synergetic effect with each other. Risk assessment analyses were performed for the consumable species, and it was found that the estimated daily and weekly intakes were below the tolerable limits established by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). The target hazard quotient (THQ) values exceeded the threshold of 1 (THQ > 1) only for As. The target cancer risk (TCR) was below the tolerable limits (> 10-5) except for As, Cd, and Al.

Lucinid clams are one of the most diverse and widespread symbiont-bearing animal groups in both shallow and deep-sea chemosynthetic habitats. Lucinids harbor Ca. Thiodiazotropha symbionts that can oxidize inorganic and organic substrates such as hydrogen sulfide and formate to gain energy. The interplay between these key metabolic functions, nutrient uptake and biotic interactions in Ca. Thiodiazotropha is not fully understood. We collected Lucinoma kazani individuals from next to a deep-sea brine pool in the eastern Mediterranean Sea, at a depth of 1150 m and used Oxford Nanopore and Illumina sequencing to obtain high-quality genomes of their Ca. Thiodiazotropha gloverae symbiont. The genomes served as the basis for transcriptomic and proteomic analyses to characterize the in situ gene expression, metabolism and physiology of the symbionts. We found genes needed for N2 fixation in the deep-sea symbiont\'s genome, which, to date, were only found in shallow-water Ca. Thiodiazotropha. However, we did not detect the expression of these genes and thus the potential role of nitrogen fixation in this symbiosis remains to be determined. We also found the high expression of carbon fixation and sulfur oxidation genes, which indicate chemolithoautotrophy as the key physiology of Ca. Thiodiazotropha. However, we also detected the expression of pathways for using methanol and formate as energy sources. Our findings highlight the key traits these microbes maintain to support the nutrition of their hosts and interact with them.