Offshore Marine Environment Research Articles

Intrasediment gypsum in subtidal offshore carbonates as a witness of basin-wide evaporitic precipitation. The case of the southern Variscan foreland basin (mid-Carboniferous)

Widespread calcite and quartz pseudomorphs, interpreted as originally gypsum crystals, occur within hemipelagic calci-mudstone accumulated in subtidal offshore environments in the broad marine foreland basin developed on the southern flank of the Ouachita–Alleghanian–Variscan Orogen during mid-Carboniferous times, which acted as a marine corridor connecting the Panthalassa and Palaeo-Tethys Oceans during the Mississippian, and progressively narrowed during the assembly of Pangea. In this study, 67 outcrops of radiolaria-bearing calci-mudstone deposits that contain calcite and quartz pseudomorphs located in northern Spain and southern France were studied to constrain the gypsum spatial distribution and sedimentological features. The recognised microfacies indicate intrasediment gypsum precipitation, accompanied by less abundant bottom-grown precipitates and gypsum cumulates, in extensive offshore, probably several ten to a few hundred metres deep, basinal environments. Gypsum precipitation took place during a short-lived temporal episode during the early Bashkirian time (Voznesenkian), which can be correlated, on the basis of benthic foraminifera, with the coastal (inter- to supratidal) gypsum evaporites identified in NW Africa (Tindouf and Reggan successions in Morocco and Algeria) that would represent the shallow-water counterparts. The occurrence of gypsum precipitates both in offshore hemipelagic calci-mudstones of the Variscan foreland basin and in inter- to supratidal environments of the epeiric Sahara Platform indicates that hypersaline conditions affected vast marine areas, roughly coinciding with the estimated age of closure of the Panthalassa and Palaeo-Tethys marine connection. Therefore, the studied succession represents the trace of a basin-wide evaporitic episode extending for hundreds of kilometres driven by foreland basin restriction, mid-Carboniferous sea-level fall and arid climate. This study provides new insights for the interpretation of gypsum precipitates in offshore marine environments encountered in the Phanerozoic and whose genesis is poorly understood.

Assessing Benthic Recovery Below the United Kingdom’s First Large‐Scale, Offshore, Longline Mussel Farm

The recent expansion of the aquaculture industry into the offshore marine environment is perceived to have a comparatively low environmental impact coupled with a high growth potential as a sustainable, large‐scale source of healthy protein. This study assessed changes in sediment characteristics and infauna assemblages following the development of the first large‐scale offshore longline mussel farm in the United Kingdom. By evaluating the effects of the farm on the sediment ecosystem and by studying infaunal sediment environmental parameters along a distance gradient away from the farm, the first before–after control–impact (BACI) study of an offshore shellfish farm is presented. Sediment grabs from the farm and control sites were analysed for sediment parameters (organic matter content (OM), particle size (PS), oxidation–reduction or redox potential (ORP) and trace elements) and infauna assemblages. There was no difference in sediment organic matter levels between the farm and control sites. Within the farm, the mean sediment grain size and ORP increased over time. Trace element concentrations were the lowest within farm sites compared to outside; concentrations increased with increasing distance from the farm. A total of 76 benthic macrofauna taxa were identified, with polychaetes being the dominant class. Over time, the number of taxa significantly increased within the farm while remaining relatively constant in control samples. Biodiversity metrics, including abundance and Shannon and Pielou’s index, were all greater within the farm compared to control areas. Overall, measures of assemblage health were higher within the farm than outside. This study demonstrates the long‐term aquaculture–environment interactions that offshore shellfish farming can have on the seabed and its significance in terms of ecosystem services.

Environmental and vegetation dynamics through the Oligocene to Early Miocene of North Africa (Egypt)

This study documents palynomorph assemblages from the Oligocene through the Early Miocene, across the significant Warm-house to Cool-house transition, using a subsurface section from the AG-5 well, north Western Desert of Egypt. Although the Paleogene and Neogene strata occupied a large area of the land, little about vegetation and ecosystem processes that shaped the climate and biodiversity during this time window is known. Here, based on a comprehensive palynological analysis of the Oligocene to Early Miocene Dabaa and Moghra formations encountered in the AG-5 well, we show that the studied area was characterized by a humid tropical to subtropical climate during the Oligocene-Miocene time interval. The obtained results provide clear evidence of the poorly known Paleogene-Neogene ecosystem in North Africa. In terms of palynostratigraphical framework, three palynozones covering the late Oligocene-Early Miocene interval are recognized. Moreover, the recovered palynomorphs inferred a deposition of the Dabaa Formation under a normal marine, inner shelf to littoral environment. However, for the basal part of the Moghra Formation, a deposition in an offshore marine environment, outer shelf (high sea level, 100–200 m depth) is assumed, whereas a deposition in shallow coastal lagoons, estuary, or delta environment (low sea level) is presumed for its uppermost part.

Interactive effects of multiple stressors with significant wave height exposure on farmed Atlantic salmon (Salmo salar) welfare along an inshore-offshore gradient

Fish farming is the fastest growing food production sector worldwide and now accounts for most human fish consumption. Expansion of finfish aquaculture to exposed offshore marine environments is appealing where additional sheltered areas are unavailable. While more energetic environments may reduce waste accumulation and parasite exposure, effects on fish health and wellbeing are largely speculative. The multiple stressors faced by fish on offshore farms may interact synergistically and increase their cumulative impact. We used 20 months of health and welfare data from eight Atlantic salmon (Salmo salar) sea pen farms in Scotland along a wave exposure gradient to assess the effects of, and interactions between, environmental variables and management treatments on fish mortality and parasite loads. While farms showed high variability in mortality rate and sea lice infections, multi-level Bayesian modelling indicated that wave exposure primarily modulated effects of other variables. Higher exposure farms showed steeper increases in mortality with time and with extreme temperatures. Similarly, sea lice infections tended to increase with time, with higher exposure farms seeing steeper increases at higher Amoebic Gill Disease (AGD) scores and at high temperatures. The effect of AGD was greater at slow water speeds. Treatments against parasites were more frequent at low exposure farms, leading to uncertainty in their impact on welfare across farms. The support for interactive effects of wave exposure with other variables rather than strong direct effects suggests an accumulation of chronic and acute stressors. Expansion of aquaculture to more energetic offshore environments may have negative impacts on fish health in some circumstances, requiring adaptation of practices. In particular, the stronger increase in mortality over time may have implications for cycle length in different environments, and the more dramatic impacts of the warmest temperatures at high exposure farms call for consideration of the change in water temperature both inshore and offshore.

Variation of mercury in 4 major estuaries in the Gulf of Thailand during wet season

The Mae Klong River (MK), Tha Chin River (TC), Chao Phraya River (CP), and Bang Pakong River (BPK) are recognized as critical conveyors of terrestrial substances, including pollutants, into the Inner Gulf of Thailand (Inner GOT). This study sought to explore the presence of mercury (Hg), a highly toxic and bioavailable pollutant, in both water and surface sediment at the mouths of the four rivers in pre- and post-wet season (WS). The results revealed that the total mercury (T-Hg) concentrations in the water ranged from 10 ng/L (TC) to 125 ng/L (CP) in pre-WS and 17 ng/L (MK) to 1011 ng/L (TC) in post-WS. Notably, the post-WS concentrations of T-Hg were relatively higher than the pre-WS, with an average concentration of particulate Hg (P–Hg) increasing by approximately 3–5 times. Consequently, the average P–Hg proportion to T-Hg of each estuary in the post-WS was comprised of greater than 67%. Moreover, a correlation was observed among salinity, total suspended solid (TSS) and particulate Hg (P–Hg). Similarly, the estuarine sediment, excluding MK, exhibited a higher average concentration of T-Hg during the post-WS period. The average T-Hg concentration in sediment ranged from 17 (BPK) to 119 (MK) μg/kg in pre-WS and 15 (MK) to 140 (CP) μg/kg in post-WS. The presence of organic matter (total organic carbon or TOC content), and clay-sized particles were identified as potential factors influencing the concentration of T-Hg in the sediment. In addition, a higher positive correlation was observed between T-Hg and silt-sized particles in BPK. In this study, both T-Hg in the water column and T-Hg in sediment increased during the post-WS period, suggesting that Hg transportation from sources to river mouths during WS were intensified. Furthermore, the correlation between T-Hg and fine-grained particle, as well as the greater T-Hg levels in the estuarine sediment, indicates that Hg may be transported from rivers to the offshore marine environment via the fine-grained fraction.

Occurrence and accumulation of microplastics in commercial fish in the coastal waters of the Lvsi fishing ground in China

In recent years, there has been an exponential increase in the research popularity of microplastics (MPs) in offshore marine environments. However, there is still a gap in the research on the accumulation of MPs in different tissues of aquatic organisms and the trophic transfer of MPs between aquatic organisms. The common occurrence of MPs in the gills and guts of 11 species of commercial fishes was examined in the coastal waters of the Lvsi fishing ground (LSFG). The obtained results showed that >85 % of MPs existed in the gills and guts of these fish, and the abundance was 2.39 ± 1.38 pieces/fish and 2.56 ± 1.42 pieces/fish, respectively. Fibrous and blue are the most common colors and shapes of MPs, and PET is the main polymer type. At the species level, the abundance of MPs in the gills and guts of a few fishes (e.g., Larimichthys polyactis, Setipinna tenuifilis, Collichthys lucidus) decreased with increasing body length and body weight (P < 0.05). At the community level, this situation was not significant (P > 0.05). With increasing trophic level (TL), MPs tended to decrease in the gills (trophic magnification factor, TMF = 0.86) but did not significantly vary in the gut. We believe that MPs are multidimensional pollutants, and their accumulation in tissues/organs of organisms has not been accurately and qualitatively determined. To establish the relationship of MP transport and trophic transfer among water, sediments and organisms, we suggest that more efforts should be made to investigate MPs in aquatic organisms in the coastal waters of LSFG and to increase the examination of MPs in the water column and sediments. This study will help us improve our understanding of MPs pollution, and provide a good reference and basis for the management, monitoring and implementation of pollutants in marine organism of coastal water.

Paleontology and stratigraphic implications of a late Paleocene elasmobranch assemblage in Talcahuano, southcentral Chile

Late Paleocene elasmobranch findings are reported, along with reinterpretations of some previous taxonomic identifications in two main outcrops around Talcahuano area (Biobío region, Chile), and also delimiting the exposed lithostratigraphic units. Reviewed fossils are among 15 genera, comprising the species Paraorthacodus clarkii, Squalus minor, Squalus orpiensis, Centrophorus sp., Squatina prima, Anomotodon novus, Striatolamia striata, Carcharias spp., Sylvestrilamia teretidens, Odontaspis winkleri, Palaeohypotodus speyeri, Palaeohypotodus rutoti, Isurolamna inflata, Premontreia gilberti, Physogaleus secundus, Palaeogaleus vincenti and Hypolophodon sylvestris. The main elasmobranch assemblage, collected from the San Martín outcrop, indicates deposition in a shallow lower shoreface-uppermost offshore marine environment and warm-temperate water. Moreover, this elasmobranch assemblage constrains the age of Pilpilco Formation into the middle-late Thanetian, which implies a latest Thanetian-early Ypresian age for the overlying Curanilahue Formation and a Danian-early Thanetian hiatus with the underlying Quiriquina Formation.

New insights into the influence of turbines on the behaviour of migrant birds: implications for predicting impacts of offshore wind developments on wildlife

Knowledge of the movement and behaviour of birds and bats around turbines in the offshore marine environment is critical for assessing the environmental impacts of offshore wind developments in the eastern USA. To address the problem of gathering high-quality, long-term data on these species in this remote environment, we designed a multi-sensor system that was recently deployed for 6 months in 2021 and 2022. Two Acoustic and Thermographic Offshore Monitoring (ATOM™) systems were deployed on wind turbines 23 nautical miles off the coast of Virginia, USA. The systems were operational during the day and night and recorded 1,581 detections of birds and bats, with 99% of detections occurring in the fall. Most detections were of birds, including 5 shorebird species, 3 gull species, 1 tern species, 3 raptor species, 1 woodpecker species, and 18 passerine species. Skuas, corvids, and swallows were also observed. There were 521 detections of bats. Differences between species detected and identified in each sensor confirms that a multi-sensor approach for monitoring is beneficial. There were no observed collisions; two individuals (1 bird and 1 bat) suffered air displacement, causing them to fall, but they recovered and continued flying. ATOM also collected novel data on insects, tracking over 7,000 insects around the turbine rotor swept zone and revealed foraging behaviour in 596 of the 1,581 bird and bat detections. Offshore wind turbines thus provide potential sites for perching and foraging. Although these turbine sites provide a new opportunity to feed, which may be beneficial for insectivores and omnivores in enabling them to reach migration destinations in better condition, the consequences of a potentially delayed arrival are unknown (positive, negative, or neutral). Overall, our approach produced the first detailed insights into terrestrial land bird and bat activity around offshore turbines, providing novel information on changes in behaviour when turbine blades are moving and during higher wind speeds. Moreover, our data show that foraging activity appears to be conducted with an awareness of the moving blades and in safe zones close but parallel to blade movements. We recorded 113 observations of activity within 10 m of the moving blades and 70 observations where interactions with moving turbine blades were within 1 m; we call these latter avoidance measures nanoavoidance. No collisions were observed.

Failure Envelopes for Circular Foundations on Two-Layered Clay under Combined Loading

This study numerically investigates the undrained bearing capacity of circular foundations founded on a two-layered clay under combined loading of vertical, horizontal, and moment loads using three-dimensional finite-element analysis. Each clay layer has different thicknesses and shear strengths, and two types of foundation–subsoil interface are considered: an interface with (a) zero tensile capacity or (b) nonzero tensile capacity. Analysis results are presented in the form of normalized failure envelopes for a wide range of layer thicknesses and shear strength ratios. The presented normalized failure envelopes under combined loads with or without the interface tension can be considered as graphical solutions for circular foundations on a two-layered clay in offshore marine environments. Failure mechanisms under various combined loads provide further insights into foundation-layered soil interactions.

Methods of joint processing of complex radar interferograms and multispectral optical images under temporal decorrelation

This article substantiates the relevance of the study, the characteristics of the joint use of optical multispectral survey, radar interferometry and partial polarimetry, identifies the scope of interpretation of the radar-optical composite built by optical and radar data, and provides a mathematical model for image processing of the water surface area. The quantitative assessment of these automated or semi-automated methods is not inferior to the accuracy of traditional methods for assessing the state of the offshore marine environment. It was shown that the most efficient approach is the direct use of the ResNet-10 deep learning algorithm on scenes when combined with complex (amplitude and phase) centimeter-range radar images and multispectral optical images of Sentinel platforms. This approach made it possible to detect 86.72% of all spots in the scenes and had an average accuracy of 75.35%. The approach has also showed a significantly reduced ability to detect patches when the local wind speed was below 2 m/s or above 12 m/s.

Middle Devonian brachiopod-hosted sclerobiont assemblage from the northern shelf of Gondwana (Mader Basin, Morocco): Diversity, colonization patterns and relation to coeval palaeocommunities

Middle Devonian (Eifelian/Givetian transition) brachiopod-hosted sclerobiont assemblage from Gondwana (Morocco, eastern Anti-Atlas, Mader Basin) has been studied for the first time. The analysis of hundreds of brachiopod shells revealed at least 26 sclerobiont taxa, making the studied palaeoecommunity one of the most diverse Middle Devonian sclerobiont assemblage reported to date. The palaeocommunity is dominated by encrusting organisms, in particular bryozoans, foraminifers, ascodictyids and microconchids, whereas bioeroders are represented by Clionolithes and Oichnus ichnospecies. As supported by microfacies, fossil preservation and the presence of encrusting Rothpletzella algae, the sclerobionts developed in a calm, euphotic, offshore marine environment situated below normal wave base. Prevalence of articulated shells without signs of either extensive mineral staining, or taphonomic alteration resulting from hydrodynamic processes, as well as preservation of some delicate encrusters ( Vinella , Rothpletzella ), indicate that the palaeocommunity did not undergo extensive time-averaging. The hosts were colonized syn vivo , as evidenced by the epibiont growth near the commissure margin, the presence of shell malformations and even embedded auloporid corals and cornulitid tubeworms. Competition for space among sclerobionts was apparently limited, as suggested by the very low number of overgrowth interactions, indicating that the shelly substrate available for colonization was abundant. The presence of the same dominant groups of sclerobionts on different host taxa indicates a lack of species-selectivity by these colonizing sclerobionts. It also suggests that the sclerobiont species pool in the environment was generally similar throughout the deposition of the sampled rock interval. As testified by the host brachiopod and bryozoan species, the sclerobiont assemblage from this locality of northern Gondwana had strong affinities with those from the southern margin of Laurussia, most likely reflecting strong connectivity between these regions provided by the South Equatorial – North Gondwana current system during the late Eifelian Kačák transgressive episode. • Diverse sclerobionts colonizing Middle Devonian brachiopods from Morocco are reported. • The assemblage is dominated by bryozoans, foraminifers, ascodictyids and microconchids. • The sclerobionts developed in a calm, euphotic, offshore environment below normal wave base. • The sclerobionts had strong affinities with assemblages inhabiting southern margin of Laurussia. • Their dispersion was enhanced during the late Eifelian Kačák transgressive episode.

The effect of laser surface textures on the corrosion resistance of epoxy coated steel exposed to aggressive environments for offshore applications

Organic coatings are commonly applied to protect metallic structures exposed to highly corrosive environments such as those found in offshore marine scenarios. In general, steel surfaces are prepared by grit blasting prior to being coated. However, this method is associated with some negative issues such as adverse environmental impacts, and safety concerns. In this context, laser surface texturing technology is gaining attention and has been used for metal surface preparation (micromachining, drilling and functionalization) in various applications. This method offers several benefits, notably ease of automation and scalability. This paper reports an investigation on the resistance to corrosion propagation of epoxy-coated laser-textured AISI A-36 surfaces, when compared to surfaces subjected to the conventional bead and grit blasting treatments (references). Nanosecond laser surface texturing was used to create groove-like and grid-like surface patterns at the microscale level. After running accelerated corrosion tests (ISO 12944-9 standard), the performance of the epoxy coating on the laser-textured surfaces was significantly improved, indicating that the laser treatment reduces the coating delamination rate, as well as its damaged area. The surface tortuosity factor plays an important role in the effectiveness of the coatings. The results also suggest that the geometrical aspects of the groove structure (presence of recast material and V-shape) promote phenomena such as mechanical interlock and mechanical hooking of the coating. Therefore, nanosecond laser surface texturing appears to be a suitable procedure for the preparation of steel surfaces installed in offshore marine environments.

Changes in flight paths of large-bodied birds after construction of large terrestrial wind turbines

The proliferation of ever-larger wind turbines poses risks to wildlife, especially from avian collision, yet avoidance behaviour of large-bodied, long-lived bird species in relation to wind turbines remains little studied away from collision “black spots” and offshore marine environments. Here, three-dimensional flight trajectory data are reported from a laser range-finder study of local movements of large-bodied birds (e.g. swans, geese, gulls, cormorants, raptors and cranes, whose populations are relatively more demographically sensitive to collision mortality) in relation to seven terrestrial 150-222 m high (mean 182 m) wind turbines constructed in Denmark in a N-S line. Comparisons of two-dimensional flight passages between turbines pre- (n = 287) and post-construction (n = 1210) showed significant (P < 0.0001) reductions from 48% to 35% within 150 m of each turbine, with corresponding increase 200-300 m from turbines. Results also showed a significant (P < 0.001) 50% reduction in the percentage of avian passages (from 21% to 10%) through the maximum turbine sweep area after construction and that the proportion of birds that passed between turbines at heights below (0-45 m) and above the turbine sweep area (> 182 m) were significantly greater (P < 0.0001) post-construction than prior to construction. These are the first results from tracking large-bodied bird flight trajectories to show the magnitude of their vertical and horizontal adjustments to the presence of turbines, which have implications for assumptions of even flight densities made by collision risk models currently used to predict avian turbine collision rates.

Autonomous Marine Robot Based on AI Recognition for Permanent Surveillance in Marine Protected Areas.

The world’s oceans are one of the most valuable sources of biodiversity and resources on the planet, although there are areas where the marine ecosystem is threatened by human activities. Marine protected areas (MPAs) are distinctive spaces protected by law due to their unique characteristics, such as being the habitat of endangered marine species. Even with this protection, there are still illegal activities such as poaching or anchoring that threaten the survival of different marine species. In this context, we propose an autonomous surface vehicle (ASV) model system for the surveillance of marine areas by detecting and recognizing vessels through artificial intelligence (AI)-based image recognition services, in search of those carrying out illegal activities. Cloud and edge AI computing technologies were used for computer vision. These technologies have proven to be accurate and reliable in detecting shapes and objects for which they have been trained. Azure edge and cloud vision services offer the best option in terms of accuracy for this task. Due to the lack of 4G and 5G coverage in offshore marine environments, it is necessary to use radio links with a coastal base station to ensure communications, which may result in a high response time due to the high latency involved. The analysis of on-board images may not be sufficiently accurate; therefore, we proposed a smart algorithm for autonomy optimization by selecting the proper AI technology according to the current scenario (SAAO) capable of selecting the best AI source for the current scenario in real time, according to the required recognition accuracy or low latency. The SAAO optimizes the execution, efficiency, risk reduction, and results of each stage of the surveillance mission, taking appropriate decisions by selecting either cloud or edge vision models without human intervention.

Discussion on the relationship between power generation output of intermittent offshore energy and Marine Climate and Environment -- Taking wave energy and solar energy as examples

In recent years, with the continuous promotion of China’s marine power strategy, the comprehensive development and application of marine resources in many aspects and in depth has become a trend. China’s South China Sea is vast and rich in resources, which has important national defense, economic and environmental significance for its comprehensive development and construction. The South China Sea is a vast sea area with abundant wave energy and solar energy. The pilot development and application of natural energy in this area is of great strategic and environmental significance for the decentralized power supply of deep-sea islands. Therefore, based on the actual application of the wave energy-solar power generation platform on YX Island, a comprehensive analysis is carried out based on the characteristics of the marine climate and environmental elements of the South China Sea, exploring the apparent efficiency of intermittent energy such as wave energy and solar energy under specific environmental conditions and putting forward relevant suggestions. The forecast will provide relevant theoretical basis and data support for the subsequent in-depth development, application and system optimization of renewable energy in the South my country Sea.

Analysis of Trends in Marine Water Quality Using Environmental Impact Assessment Monitoring Data: A Case Study of Busan New Port

Lee, S.M.; Lee, E.J.; Yoo, H.S., and Lee, M.J., 2020. Analysis of trends in marine water quality using environmental impact assessment monitoring data: a case study of Busan new port. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 39-46. Coconut Creek (Florida), ISSN 0749-0208.Various development projects, including harbor construction, are carried out in coastal areas. In South Korea, the performance of environmental impact assessment (EIA) is legally required for development projects in marine areas to monitor the impacts of these projects on offshore marine environments. National Marine Environmental Measurement Network (NMEMN) data can be used to examine the overall status of the marine environment prior to a development project, but these data are very limited. In contrast, EIA data are collected from a large number of locations over various periods. The purpose of this study was to analyze trends in the coastal marine environment using NMEMN and EIA data collected in 2010–2011 for Busan New Port, where multiple development projects are underway. Use of the combined dataset enabled more effective analysis of trends in marine water quality, including those in dissolved oxygen, the chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), than did the use of NMEMN data alone. Values increased in the bottom layer, especially in the summer, after port operation had begun. For example, average summer ranges for COD, TN, and TP in the bottom layer in 2000–2005 were 1.41–2.2 mg/L, 0–0 µg/L, and 0–17.62 µg/L, respectively, and those in 2006–2011 were 1.53–3.2 mg/L, 0–281 µg/L, and 8.09–49.35 µg/L, respectively. In the future, data from various sources should be integrated into EIAs to identify not only the impacts of a single project, but also the overall impacts of multiple changes in an area. This method also could be used to provide basic data for continuous management of the marine environment.

Reservoir characterization utilizing pre-stack inversion and artificial neural network techniques, Offshore Nile Delta, Egypt

Abstract The Nile Delta has become a prolific hydrocarbon province, especially for gas. After initial discoveries onshore, the focus has switched to the offshore marine environment. Pre-stack seismic techniques have proven to be highly effective in characterizing the gas-sandstone reservoirs. We apply pre-stack inversion followed by a probabilistic neural network approach in order to generate estimates of saturation and porosity for the Simian Field.

Phylogenetic response of naraoiid arthropods to early–middle Cambrian environmental change

AbstractThe Cambrian Period, primarily known for animal life diversifying, experienced global extinctions. Pulses of extinction in Cambrian Series 2 are exemplified by the disappearance of archaeocyath sponges and olenelline and redlichiid trilobites. However, the effect of such extinctions on outer shelf organisms, as typify Burgess Shale‐type (BST) deposits, remains relatively unknown. The phylogeny of naraoiid arthropods, represented in BST deposits globally, has consequently been reconstructed from either side of the Series 2 – Miaolingian extinction event to evaluate the response of offshore marine organisms to Cambrian environmental perturbation. As soft anatomy is known for only a subset of naraoiid species, exoskeletal morphology has proven important. Misszhouia and Naraoia (Naraoia) are distinguished morphometrically by posterior shield length/width and anterior shield length/posterior shield length. Morphometry has also been used to strengthen the identification of some cryptic naraoiid species and revise stratigraphic ranges. A revised naraoiid phylogeny reveals Misszhouia as a monophyletic subgenus, the former genus Pseudonaraoia nests within Naraoia and is placed in synonymy, and the systematic position and status of the Subfamily Liwiinae are sensitive to character weighting. Ten species of Naraoiidae range across the Series 2 – Miaolingian boundary, all naraoiid lineages originating during the main BST window. The persistence of outer shelf naraoiids throughout the Series 2 extinctions suggests that deeper offshore marine environments were resilient to extinction during periods of environmental stress. This study provides novel empirical support for the asylum of BST communities, which may contribute to the taxonomic longevity and widespread geographic distribution of taxa in these biotas.

Niche Partitioning between Coastal and Offshore Shelf Waters Results in Differential Expression of Alkane and Polycyclic Aromatic Hydrocarbon Catabolic Pathways.

Marine oil spills can impact both coastal and offshore marine environments, but little information is available on how the microbial response to oil and dispersants might differ between these biomes. Here, we describe the compositional and functional response of microbial communities to different concentrations of oil and chemically dispersed oil in coastal and offshore surface waters from the Texas-Louisiana continental shelf. Using a combination of analytical chemistry and 16S rRNA amplicon and metatranscriptomic sequencing, we provide a broad, comparative overview of the ecological response of hydrocarbon-degrading bacteria and their expression of hydrocarbon-degrading genes in marine surface waters over time between two oceanic biomes. We found evidence for the existence of different ecotypes of several commonly described hydrocarbon-degrading bacterial taxa which behaved differentially in coastal and offshore shelf waters despite being exposed to similar concentrations of oil, dispersants, and nutrients. This resulted in the differential expression of catabolic pathways for n-alkanes and polycyclic aromatic hydrocarbons (PAHs)-the two major categories of compounds found in crude oil-with preferential expression of n-alkane degradation genes in coastal waters while offshore microbial communities trended more toward the expression of PAH degradation genes. This was unexpected as it contrasts with the generally held view that n-alkanes, being more labile, are attacked before the more refractory PAHs. Collectively, our results provide new insights into the existence and potential consequences of niche partitioning of hydrocarbon-degrading taxa between neighboring marine environments.IMPORTANCE In the wake of the Deepwater Horizon oil spill, the taxonomic response of marine microbial communities to oil and dispersants has been extensively studied. However, relatively few studies on the functional response of these microbial communities have been reported, especially in a longitudinal fashion. Moreover, despite the fact that marine oil spills typically impact thousands of square kilometers of both coastal and offshore marine environments, little information is available on how the microbial response to oil and dispersants might differ between these biomes. The results of this study help fill this critical knowledge gap and provide valuable insight into how oil spill response efforts, such as chemically dispersing oil, may have differing effects in neighboring coastal and offshore marine environments.

Surface ocean nitrate-limitation in the aftermath of Marinoan snowball Earth: Evidence from the Ediacaran Doushantuo Formation in the western margin of the Yangtze Block, South China

Geochemical and paleontological studies suggest that a rapid rise in atmospheric O2 level in the termination of the Marinoan global glaciation (635 Ma) might have triggered the diversification of eukaryotes and caused the deep ocean oxygenation. It is proposed that the Earth’s surface redox condition was directly linked to the marine primary productivity, which represented the only major O2 source before the evolution of land plants. The marine primary productivity was mainly controlled by the bioavailability of macronutrients, phosphorus (P) and nitrogen (N). Thus, reconstruction of ancient P and N cycles can provide direct constraints on marine organic matter production and the redox landscape of the ocean. Previous studies of the Ediacaran Doushantuo Formation in the Yangtze Block, South China, suggested that the Ediacaran marine N cycle was highly dynamic and was characterized by dramatic fluctuations in the intensity of denitrification. However, these studies were mainly focused on sections deposited in the offshore marine environment, and little is known about the N cycle in the nearshore regions. In this study, we report high-resolution organic carbon (δ13Corg) and nitrogen (δ15NTN) isotopes of the Doushantuo Formation at the E-Shan section in the western margin of the Yangtze Block. The Doushantuo Formation at the E-Shan section is composed of alternating deposition of thin bedded sandstone and mudstone, and was deposited in a nearshore delta environment. The δ13Corg profile displays two prominent negative excursions, which are coincident with two positive excursions in δ15NTN. The positive excursion in δ15NTN implies the enhanced denitrification, resulting in the loss of N (nitrate and ammonium). In addition, there are negative correlations between δ15NTN and TOC content and between δ15NTN and δ13Corg. Such relationships suggest that the reduction of N supply would lower primary productivity and accordingly decrease the carbon isotope of dissolved inorganic carbon (δ13CDIC) in the surface ocean. In addition, this interpretation also implies that N-fixation was not active in the nearshore region. We speculate that the muted N-fixation in the nearshore regions could be attributed to the Fe limitation in oxic shallow seawater and general Mo deficiency of the Ediacaran ocean. Thus, our study indicates that the surface ocean productivity and marine redox landscape were coupled in the Ediacaran ocean.