Marine Benthos Research Articles

The effect of the Tethyan seaway closure on the Oligo−Miocene marine benthic diversity and distribution around Eurasia

The Cenozoic evolution of the Tethyan seaway significantly shaped marine and terrestrial biota around Eurasia. The Tethys Ocean connected the Atlantic and the Pacific during the early Cenozoic, allowing marine faunal exchange. However, during the early Miocene, the ‘ Gomphotherium Landbridge’ developed, restricting the marine connection between the proto-Mediterranean in the west and the provinces of the eastern Tethys Ocean. In contrast to the well-documented phenomena of terrestrial mammalian exchange through the land connection brought about by the closure, little is known about its impact on the marine fauna. To assess the overall effect of this separation on the distribution and diversity of marine organisms, we studied the Oligo−Miocene fossil record of marine benthos including Cnidaria, Echinodermata, Foraminifera and Mollusca. We compiled 15 894 reported occurrences from the early Oligocene to late Miocene comprising 1477 genera, 404 families and 85 orders from four faunal provinces and evaluated their palaeobiogeographic patterns. Our study demonstrates that the proportion of genera shared between the eastern and western provinces decreased after the early Miocene. The majority of the non-shared families developed during or after the early Miocene. High faunal diversity during the early Miocene and increasing endemicity among the eastern provinces are consistent with the development of a shallow seaway that supported speciation and reduced biotic exchange. The considerable variation in the magnitude and timing of the response across taxonomic groups reflects the combined effects of preservation bias and the differential responses of fauna. Our study supports an early Miocene initiation of the Tethyan seaway closure, followed by intermittent connectivity before the complete closure. This closure and its climatic consequences influenced the evolution of the Eurasian biota. Future studies should use a multidisciplinary approach combining the fossil record, genetic divergence and climate proxies to fully understand the effects of environmental changes and the seaway closure on marine benthos diversity dynamics.

A comparative analysis of crustacean exoskeletons: structural, microstructural, morphological, and UV absorption studies

This study aims to investigate the structural, thermal, and spectral characteristics, along with the ultra-violet (UV) absorption of various marine benthos exoskeletons, such as various species of crabs (Portunus sanguinolentus, Portunus pelagicus, Charybdis feriata) and mantis shrimp (Oratosquilla oratoria). Their unique properties and ability to survive in harsh oceanic environments make them interesting research subjects. This research utilized powder x-ray diffraction (XRD) analysis to determine the crystal structure of the benthic varieties. The sample surface was analyzed using high-resolution micrographs obtained from field-emission scanning electron microscopy (FESEM), which identified the presence of chitin and calcite in the marine benthos. This was further confirmed by differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The optical characteristics were investigated using UV-visible spectroscopy. The proximate analysis revealed high protein content in the mantis shrimp exoskeleton compared to other crab species, highlighting its excellent UV absorption characteristics. Overall, this research has the potential to broaden our understanding of marine organisms, which can have potential applications in biotechnology and materials science to develop nature-inspired innovative materials sustainably.

Nonspecific immune, histology and accumulation of marine worm, Urechis unicinctus in response to bisphenol A (BPA)

Bisphenol A (BPA) is one of the environmental endocrine disruptors, due to its chemical stability it exists in abundant concentrations in water and soil consequently accumulating in the food chain and causing many endocrine-related health problems. So far, studies on the effects of BPA on marine invertebrates have focused on acute toxicity, endocrine regulation, reproduction, and development. However, fewer studies have been conducted on marine benthos. The current study aimed to detect the accumulation of BPA and its impact on tissue structure, antioxidant capacity, and immune indexes in marine worm, Urechis unicinctus. U. unicinctus, as a common marine benthic animal, were exposed to different concentrations of BPA. Blood cells and intestinal tract were taken for tissue structure inspection, and supernatant of the coelomic fluid was collected for oxidative and antioxidant biomarkers. Results showed that the accumulation of BPA in muscles of U. unicinctus tended to increase with exposure time. BPA induced a rise in H2O2 and MDA content, and altered the activities of CAT, T-SOD, GST, LSZ and ACP, weaken the immune system functions. Moreover, pathological observation showed that BPA caused severe histopathology in the respiratory intestine, stomach, and midgut. These results will be helpful to understand the response mechanism of U. unicinctus under BPA exposure and provide a reference for controlling the aquaculture conditions and marine water quality of U. unicinctus.

Functional structure and diversity of marine benthos reflect food availability and quality, as evidenced by isotopic diversity

AbstractOrganic matter (OM) resources shape not only the trophic diversity of benthic communities but also the diversity of benthic functional traits. The resulting community structure has a direct effect on many ecosystem processes and functions. Still, the relationship between functional diversity of marine benthos and its trophic diversity in response to the variability of food remains poorly investigated. To explore this relationship we focused on the assessment of various facets of macrobenthic diversity in two temperate coastal areas (southern Baltic Sea) characterized by similar species pool and habitat properties but different OM sources and supplies. We also identified spatio‐temporal patterns of functional structure and assessed, which OM properties had the strongest influence on benthic communities. In our study, functional space dispersion followed isotopic space dispersion, reflecting the positive relationship between food variability and ecological functions of benthic communities. Moreover, functional structure in shallow areas was more location‐specific in comparison to deeper areas, and this was significantly related to OM parameters. Higher OM variability close to the river mouth prevented the community from becoming dominated by one specialized species, whereas limited OM supply at shallow open coast lowered the diversity by enabling stronger competitor to dominate the community. In more offshore areas, local OM variability ceased and hence, communities tended to reflect similar trophic and functional patterns. Our study demonstrates that functional and isotopic diversity approaches can be effectively combined to better understand mechanisms driving benthic community structure and confirm that greater variability in OM supply increases diversity of benthic communities.

Metazoan diversity and community assemblages in sediments across a Western Pacific Trench-Arc-Basin system: insights from eDNA metabarcoding

Trench-arc-basin (TAB) systems are widely distributed in the deep sea, yet our understanding of their biodiversity patterns and community assemblages remains limited. In this study, we collected sediment samples from 22 stations across a Western Pacific TAB system and identified 85 families of marine benthos from 15 phyla by using eDNA metabarcoding with the 18S rRNA gene V4 region. Nematodes were the most dominant metazoan taxa followed by echinoderms, arthropods, and annelids. The highest biodiversity and species specificity were observed at stations located near seamounts. The community assemblages were highly heterogeneous in this TAB system, likely induced by the large geographic barriers and the high habitat heterogeneity. Furthermore, the total organic carbon content and median grain size of the sediment drive the overall community composition, and the water depth exerts a significant influence on species richness and abundance. Our results provide insight into benthos diversity and distribution across a TAB system and data for further comparisons and modeling studies.

Environmental heterogeneity of cold seep by biological trait analysis of marine nematodes at Site F cold seep in South China Sea

Cold seeps provide high environmental heterogeneity for marine benthos. Site F is one of the active cold seeps in the South China Sea. In this study, free-living marine nematode communities were investigated at Site F and the adjacent deep-sea area. A total of 67 genera and 32 families were identified. The mean density at cold seep sites ranged from 13.6 to 181.8 ind./10 cm2, and that at the adjacent deep-sea sites ranged from 36.9 to 301.4 ind./10 cm2. At cold seep sites, the most dominant nematode genera were Desmoscolex, Pierrickia, Sabatieria, Halalaimus, and Dorylaimopsis while at deep-sea sites, the most dominant genera were Retrotheristus, Thalassomonhystera, Desmoscolex, Cobbia, and Halalaimus. Deposit feeders of nematodes were dominant at all sites. Results of biological trait analysis showed that there was high environmental heterogeneity for nematodes at Site F. Water depth, sediment organic matter content, and sand proportion had important influences on nematode communities.

Effects of oxygen availability on mycobenthic communities of marine coastal sediments

In coastal marine sediments, oxygen availability varies greatly, and anoxic conditions can develop quickly over low spatial resolution. Although benthic fungi are important players in the marine carbon cycle, little is known about their adaptation to fluctuating availability of oxygen as terminal electron acceptor. Here, we study which part of a mycobenthic community from oxic coastal sediments can thrive under temporarily anoxic conditions. We test whether phylogeny or certain fungal traits promote plasticity in respect to changes in oxygen availability. Therefore, we incubated mycobenthos under oxic and anoxic conditions, performed ITS2 Illumina tag-sequencing and an additional meta-analysis on a literature survey. Half of all OTUs showed a plasticity towards changing oxygen availability and exhibited different strategies towards anoxic conditions, with rapid response within hours or a delayed one after several days. The strategy of dimorphism and facultative yeasts were significantly linked to OTU occurrence in anoxic conditions, while phylogeny and other traits had less effect. Our results suggest that different fungal niches are formed over the duration of prolonged anoxic conditions. The taxon-specific proliferation seems to be regulated by the fine-tuning of various traits and factors. It is essential to take these results into account when conducting conceptual work on the functionality of the marine benthos.

EFP-YOLO: A quantitative detection algorithm for marine benthic organisms

Underwater object detection technologies are widely applied in the field of marine scientific research. In real underwater environments, a large number of dense, blurred, and small-sized objects appear. It is difficult for current general-purpose object detectors to detect these samples. To solve these problems, this paper proposes a quantitative detection algorithm EFP-YOLO (Enhance the Ability of Feature Extraction and Perception Ability of YOLOX) for marine benthic organisms that improved on YOLOX. Firstly, IGACSP (Cross Stage Partial Module with Interactive Global Attention) is embedded in the backbone to enhance the ability for extracting features of small-sized and blurred objects, which fuses local and global information in a parallel interactive way. To improve the capacity for detecting multiscale objects, EPPM (Efficient Pyramid Pooling Module) fuses feature maps from different scales that provide sufficient contextual information. Secondly, FSM (Feature Selection Module) and FAM (Feature Alignment Module) are introduced into the feature fusion part for spatial feature extraction and feature alignment, respectively. The modules provide accurate boundary localization information for the detection of dense objects. Finally, ATFhead (Asymmetric Task Focused head) is proposed to increase the scale perception, spatial perception, and task perception of the detection head. It improves the classification and localization abilities of the model, thus achieving accurate counting of marine benthic organisms. The experimental results show that compared with YOLOX-S, mAP0.5:0.95 is improved from 59.7% to 64.6% on the DUO dataset. EFP-YOLO demonstrates superior performance in the quantitative detection of marine benthos compared to other object detection algorithms. This can effectively advance marine scientific research and promote biological conservation efforts. To show the generality of EFP-YOLO, we use a generic object detection dataset for experiments. You can access the code for EFP-YOLO publicly on https://github.com/llllllvv/EFP-YOLO.

DSE-FCOS: dilated and SE block-reinforced FCOS for detection of marine benthos

DSE-FCOS: dilated and SE block-reinforced FCOS for detection of marine benthos

Substrate- and life habit-induced morphological convergence and divergence in Recent marine bivalve communities

Abstract The morphological disparity of the marine benthos, through the Phanerozoic, is shaped by multiple abiotic and biotic factors, among which substrate and ecology are key contributors. However, the relationship among substrate, ecology, and morphology is not straightforward—a substrate can be occupied by phylogenetically unrelated families with different life habits, influencing morphological convergence. In contrast, related taxa may differ in substrate and life habits, indicating morphological divergence. Here we evaluate the effect of substrate and ecology on the community-level morphological disparity of 398 Recent marine bivalve species from coastal India, using geometric morphometrics. We further evaluate whether the observed patterns are decoupled from taxonomic identities, i.e., phylogenetic (in)dependence. We find that the Recent marine bivalve assemblages show significant morphological differences while living in different substrates or having different life habit traits. However, while sharing a specific substrate or life habit trait (tiering/motility), different families do not show shape convergence, i.e., families maintain their mean shape, except for families living in soft sediments, for which they show strong substrate-driven morphological convergence. These instances of morphological divergence and convergence suggest that the association among sediment preference, ecology, and shape can be rather complex, and can often transgress phylogenetic boundaries in bivalves.

A relict Triassic brittle star (Echinodermata, Ophiuroidea) in Lower Jurassic strata of Asturias, north-west Spain

Ophiuroids, also known as brittle stars, are an important component of modern marine benthos, yet their fossil record is still poorly understood. Here, we describe new finds of ophiuroids from the upper Sinemurian (Lower Jurassic) of Asturias, north-west Spain. The material consists of several articulated specimens that show all relevant anatomical details to allow for an exhaustive description of a new species, Arenorbis santameraensis sp. nov., which adds a Jurassic member to the genus Arenorbis previously known exclusively from the Middle Triassic of central Europe. We demonstrate that Arenorbis has characters that are typically found in the suborder Ophiodermatina. The new Jurassic record of Arenorbis shows remarkable parallels with its Middle Triassic equivalents in terms of sedimentological and taphonomic context, suggesting niche conservatism in this genus. In contrast to its wide geographical distribution during the Middle Triassic, the new species is currently only known from a restricted area, which suggests that it represents a Jurassic relict of a formerly widespread Triassic lineage.

Culture-Independent Single-Cell PacBio Sequencing Reveals Epibiotic Variovorax and Nucleus Associated Mycoplasma in the Microbiome of the Marine Benthic Protist Geleia sp. YT (Ciliophora, Karyorelictea).

Microbes in marine sediments constitute up to five-sixths of the planet's total biomass, but their diversity is little explored, especially for those forming associations with unicellular protists. Heterotrophic ciliates are among the most dominant and diversified marine benthic protists and comprise hotspot niches of bacterial colonization. To date, studies using culture-independent single-cell approaches to explore microbiomes of marine benthic ciliates in nature are almost absent, even for the most ubiquitous species. Here, we characterize the major bacterial groups associated with a representative marine benthic ciliate, Geleia sp. YT, collected directly from the coastal zone of Yantai, China. PacBio sequencing of the nearly full-length 16Sr RNA genes was performed on single cells of Geleia. Fluorescence in situ hybridization (FISH) analysis with genus-specific probes was further applied to locate the dominant bacterial groups. We identified a Variovorax-like bacterium as the major epibiotic symbiont residing in the kineties of the ciliate host. We provide evidence of a nucleus-associated bacterium related to the human pathogen Mycoplasma, which appeared prevalently in the local populations of Geleia sp. YT for 4 months. The most abundant bacterial taxa associated with Geleia sp. YT likely represent its core microbiome, hinting at the important roles of the ciliate-bacteria consortium in the marine benthos. Overall, this work has contributed to the knowledge of the diversity of life in the enigmatic marine benthic ciliate and its symbioses.

Indications of marine benthos occurrence from multi-spectral multi-beam backscatter data: a case study in the North Sea

To facilitate the conservation of seafloor habitats and planning of offshore activities, there is a growing need for mapping marine benthos in an effective and efficient way. Acoustic data acquired by multi-beam echosounders (MBES) have been extensively used for large-scale and high-resolution seafloor characterization. A deeper understanding of the relationship between backscatter data and sediment compositions can help to identify the benthos occurrence from the MBES data. With two multi-spectral MBES datasets collected near the western Wadden Sea islands in the North Sea, we investigated the potential of mapping marine benthos through backscatter classification. Two unsupervised classification methods, i.e., Bayesian classification, which mainly exploits the backscatter strength from incident angles larger than 20°, and hierarchical clustering of the backscatter strength at different angular ranges, were employed and the results were compared. The classification results from both methods showed a good correspondence with sediment properties such as the median grain size. Moreover, based on a principal component analysis of bottom sample properties, the hierarchical clustering results indicated a better distinction between contributions from the gravel content and benthos occurrence, e.g., sand mason worm density, than Bayesian classification, through involving the backscatter angular variations. Classification for multiple frequencies, on the other hand, showed little difference regarding the relationship with bottom sample properties. Although the backscatter difference between frequencies was also found to positively correlate with certain sample properties, using multi-spectral features for acoustic classification in this study did not reveal additional information compared to single-frequency classification results.

Impacts of Ocean Deoxygenation on Marine Benthos in the Gulf of Mexico

Ocean deoxygenation is a growing concern globally. Oxygen is less soluble in warm water, and warming temperatures also result in the slowdown of ocean circulation which limits oxygen delivery to deeper waters. Anthropogenic eutrophication has also contributed to the development of hypoxic conditions in many coastal areas. Here we investigate biodiversity structure along an environmental gradient in the Gulf of Mexico to see how patterns of spatiotemporal turnover can inform future biotic response of benthos to ocean deoxygenation. Live and dead assemblages of bivalve mollusks were collected at 15 stations offshore Louisiana, Alabama, and Florida. Abundance and body size data were collected, and specimens were classified functionally using information about feeding, attachment, life position, and body size. Environmental conditions were characterized using multi-decadal mean sea surface temperature (SST), dissolved oxygen (DO), and net primary productivity (NPP), and grain size data from our field samples. Stations in the north-central Gulf affected by Mississippi River discharge are characterized by higher NPP, lower DO, and higher percentages of silt and clay than stations in the northeastern Gulf. Both taxonomic and functional diversity significantly covary with this environmental gradient, with the lowest diversities observed at stations in the core of Louisiana’s “dead zone.” Analyses of spatiotemporal turnover patterns reveal shifts in the dominant feeding mode, with hypoxic environments containing a greater abundance of deposit and mixed feeders, compared with more oxygenated environments that host an abundance of suspension feeders and are characterized by a greater variety of feeding ecologies. Live-dead analyses reveal a shift in taxonomic and functional diversity in coastal Louisiana, that appears to coincide with the onset of anthropogenic eutrophication in these coastal settings.

MAD-YOLO: A quantitative detection algorithm for dense small-scale marine benthos

Marine biological resources are abundant, and the reasonable development, research and protection of marine biological resources are of great significance to marine ecological health and economic development. At present, underwater object quantitative detection plays a very important role in marine biological science research, marine species richness survey, and rare species conservation. However, the problems of a large amount of noise in the underwater environment, small object scale, dense biological distribution, and occlusion all increase the detection difficulty. In this paper, a detection algorithm MAD-YOLO (Multiscale Feature Extraction and Attention Feature Fusion Reinforced YOLO for Marine Benthos Detection) is proposed, which is based on improved YOLOv5 is proposed to solve the above problems. To improve the adaptability of the network to the underwater environment, VOVDarkNet is designed as the feature extraction backbone. It uses the intermediate features with different receptive fields to reinforce the ability to extract feature. AFC-PAN is proposed as the feature fusion network so that the network can learn correct feature information and location information of objects at various scales, improving the network's ability to perceive small objects. Label assignment strategy SimOTA and decoupled head are introduced to help the model better handles occlusion and dense distribution problems. Experiments show the MAD-YOLO algorithm increases mAP0.5:0.95 on the URPC2020 dataset from 49.8% to 53.4% compared to the original YOLOv5. Moreover, the advantages of the model are visualized and analyzed by the method of controlling variables in the experimental part. The experiments show that MAD-YOLO is suitable for detecting blurred, dense, and small-scale objects. The model performs well in marine benthos detection tasks and can effectively promote marine life science research and marine engineering implementation. The source code is publicly available at https://github.com/JoeNan1/MAD-YOLO.

Diversity and structure of bacterial and archaeal communities associated with the vulnerable sponge Halichondria cebimarensis.

Sponges are essential components of the marine benthos and well known for their complex and abundant associated microbial communities. There are five endemic species of the genus Halichondria on the Brazilian coast and H. cebimarensis is one of the least studied. This sponge has a very limited geographic distribution and is classified as vulnerable. In order to understand the bacterial and archaeal communities associated with this sponge, samples of H. cebimarensis were collected from the southwestern Atlantic coast (Brazil, São Paulo state). Choanosome samples were separated and processed to be (i) inoculated in three different culture media; (ii) investigated by transmission electron microscopy; (iii) submitted to 16S rRNA metabarcoding. Forty isolates were obtained and 12 were identified as belonging to the Bacilli class. The culture-dependent approaches allowed us to access unique members of the microbial community. Our analyses revealed that this animal belongs to the Low Microbial Abundance group of sponges. Culture-independent approaches showed that the H. cebimarensis microbiome is dominated by the heterotrophic Gammaproteobacteria AqS2 ("Ca. Amphirhobacter heronislandensis"). This is the first study to reveal details of the microbiome of this vulnerable sponge and is an important step in understanding how this sponge functions, its biotechnological potential and a contribution to conservation efforts.

Assessing sea floor functional biodiversity and vulnerability

The marine benthos has been largely studied through the use of response traits that characterise species vulnerability to disturbance. More limited has been the specific use of effect traits that represent other species descriptors and that express ecosystem functions. On the sea floor, the benthos is a key ecosystem-engineering component for which functions can be relevantly derived from effect traits. This study provides a typology of sea floor functions based on an extensive data compilation of effect traits. We classified 812 benthic invertebrate species from the northeast Atlantic by 15 effect traits expressing substratum alteration and habitat creation. Cluster analysis identified 15 species groups that represented various epi- or endobenthic functions. Beyond function-habitat specificity, we show that soft sediment species exhibited broader functional niches in the trait space that increase multi-functionality, and were endowed with rare combinations of traits that expanded the functional extent of the species assemblage. As a consequence, soft sediments can host a higher functional diversity than hard substrata because a wider range of above- and below-substratum activities are possible in soft bottoms. Based on response traits documented for the same species and used to express vulnerability to natural or human-induced disturbance, we then show that vulnerability within sea floor functions can be considerably variable. This can be a consequence of the independence between the evolutionary nature of response traits and the contingent engineering abilities of benthic species through effect traits. The paper provides theoretical and utilitarian clarifications on this trait dichotomy.

Soft-walled monothalamid foraminifera from the intertidal zones of the Lorn area, north-west Scotland

Abstract Recent advances in molecular phylogeny and increasing numbers of studies carried out worldwide in subtidal and deep-water marine sites have confirmed that monothalamid foraminifera represent a significant component of the marine benthos. Fewer studies have been carried out on monothalamids in littoral zones, and here I describe more than 13 novel morphotypes of soft-walled monothalamids found at several intertidal sites in the Lorn area of north-west Scotland. Samples of sediment were collected from these areas and monothalamid tests were removed from the mud by direct manipulation with brushes, by coverslip-capture, by capture with a magnet for those with magnetic particles or by extraction from mud balls. Attached forms of tests from the same sites were isolated from collected seaweed blades, pebbles and decaying shells. Monothalamids were observed live and photographed in their natural colours, followed by examination after preservation in alcohol and embedding in glycerol. The greatest diversity of species was found to be at estuaries near to the mouths of the sea lochs, and the abundance of some of the species varied with the time of the year, being different for each species. The observed taxa included a Vellaria sp. and Psammophaga sp., two allogromiids, three saccamminids and six undetermined species; each assemblage of specimens may have contained more than one species not readily discernible by morphological characteristics alone. Taxonomic parallels between the described specimens and those in reports for other parts of the world and in deeper waters in western Scotland are discussed.

Quaternary coral, coralline algal and vermetid assemblages as sea-level indicators: a review

Corals, coralline algae and vermetid gastropods are indirect (marine limiting) relative sea-level (RSL) indicators. The precision in sea-level reconstruction based on fossils of those organisms depends on the probable palaeodepth in which they grew. Constraining such palaeodepth depends, in turn, on the available information about the habitats of their living counterparts. Diverse genera, species and species assemblages of corals, coralline algae and vermetid gastropods have historically been proposed as reliable indicators of narrow, shallow depth ranges. However, the increased information on depth distribution of marine benthos in the last two decades has challenged some early assumptions about depth ranges of taxa considered diagnostic of precise palaeodepths. Here, the authors test the reliability of coral, coralline algal and vermetid assemblages that have been extensively used in RSL reconstructions in the light of data from Ocean Biogeographical Information System (OBIS) and other recently published data. In the Indo-Pacific province, these data support the use of the robust-branching and the shallow, high-energy encrusting coral assemblages with a 0 to 10 m uncertainty. In both cases many component species have unimodal distributions and both median and average water depths are shallower than 10 m. The reliability of these coral assemblages as indicative of shallow water depths is strengthened when corals are encrusted by thick plants of the coralline alga Porolithon gr. onkodes. According to OBIS data, coralline algae of this species group in the Indo-Pacific are restricted to very shallow waters (95% probability of occurrence shallower than 0.2 m and in 99.6% of records shallower than 6 m). However, such a narrow depth range and the overall scarce data on coralline algal species in the OBIS database are questionable due to difficulties of coralline algal species identification with the naked eye. A comprehensive survey of the modern distribution of coralline algae at One Tree Reef (southern Great Barrier Reef) indicates that P. gr. onkodes has a log-normal distribution with median depth of less than 5 m and 95% of occurrence probability of thick crusts (> 0.2 mm) shallower than 8.8 m. Data on modern distribution of vermetids are scarce. In the OBIS database, vermetid species are reported from relatively wide depth ranges. However, relatively high densities (> 10 individuals per m2) on coral and coralline algal surfaces only occur from above mean low tide to some 6 m depth. In the Western Atlantic-Caribbean province Acropora palmata is the most precise RSL marker and no additional components of fossil assemblages improve its palaeodepth information. The confident use of coralgal and vermetid assemblages as RSL indicators relies on the identification of fossil corals and coralline algae at the species or species-group level. The scarcity of available data highlights the need for further studies on distribution of coralline algal species and vermetid in modern coral reefs from a variety of oceans and reef settings.

YoloXT: A object detection algorithm for marine benthos

In recent years, the marine economy has developed rapidly, and human demand for marine resources has increased greatly. At present, target detection technology has a wide range of applications and prospects in seabed observation and ocean engineering. However, the accuracy and robustness of existing target detection methods are low due to the complex underwater environment, poor lighting, and poor quality of undersea images and videos. To solve these problems, this paper proposes YoloXT, a new quantitative identification method for marine benthos. YoloXT introduces the DECA (Deformable Coordinate Attention) module, which expands the spatial awareness in feature extraction and can learn image features more effectively. Meanwhile FPST-PAN (Feature Pyramid S2win Transformer, Improved Path Aggregation Network) was proposed to deal with the problem of marine benthic target diversity. It further integrates deep and shallow features through multi-scale skip-connection and Transformer and improves the model's ability to deal with complex and changeable marine environments. Finally, the positive and negative sample assignment strategy OAA (Optimal Anchor Assignment) applied to the detection head is proposed. It effectively avoids the problem of unbalanced distribution of positive and negative samples caused by traditional sample assignment methods and marine benthos image noise. Experiments on the IOC-URPC dataset show that the mAP of YoloXT is 3.9% higher than that of YoloX, reaching 70.9%. YoloXT has demonstrated excellent performance in quantitative identification task of marine organisms, which can effectively contribute to the exploitation and conservation of marine resources. The source code is publicly available at https://github.com/F1veZhang/YOLOXT.