Adjacent Waters Research Articles

ВЛИЯНИЕ ПРИЛИВА НА ВОДООБМЕН ЧЕРЕЗ ПРОЛИВ ЛАПЕРУЗА

Based on the analysis of oceanographic survey materials on the standard section S1 and satellite information, important features of the influence of tidal currents on the formation of hydrological conditions in the La Perouse Strait and adjacent waters have been identified. It was revealed that in the warm season, when the seasonal flow is directed from the Sea of Japan to the Sea of Okhotsk (Soya Warm Current), at the high tide in the northern part of S1 section the cold water with low salinity is observed in the surface layer (the temperature may differ from the southern stations by 3 times, and the salinity by 2 psu). At low tide in the northern part of S1 the water is also cold, but with high salinity, which indicates the inflow of water from the West Sakhalin current into the Sea of Okhotsk. The temperature contrasts between the northern and southern parts of the Strait are also confirmed by satellite observations. During the cold season in the northern part of the strait, there is a flow of colder and less salty Okhotsk Sea water into the southeastern part of the Tatar Strait. It is wider and more developed in depth compared to the summer season. At low tide, when the tidal current is directed to the east, this flow narrows noticeably.

Multivariate Environmental Factors and Seasonal Spatial Dynamics Affecting the Phytoplankton Community in Yazhou Bay, South China Sea

This study investigated phytoplankton and water environmental factors in Yazhou Bay, South China Sea, during the winter, spring, and summer of 2023. It examined phytoplankton community structure, subgroup heterogeneity, and key environmental drivers. Phytoplankton abundance ranged from 0.08 to 14.30 × 10⁴ cells·L−1, with high concentrations in estuary and nearshore zones. In summer, currents carry phytoplankton offshore, with stratification leading to high sedimentation in southern offshore waters. RDA results indicated that in winter and spring, inorganic nitrogen mainly influences phytoplankton distribution, while silicate is the primary factor in summer. Although seasonal differences in total phytoplankton abundance are minimal, significant horizontal and vertical distribution variations exist. Diverse preferences of different phytoplankton species for temperature, salinity, nitrogen, and phosphorus result in high species diversity. The Shannon–Wiener diversity index (H′) averages 3.96 ± 0.09, and the Pielou evenness index (J) averages 0.82 ± 0.01. Dominant species include Pseudo-nitzschia pungens, Skeletonema costatum, and Rhizosolenia sinica. Influenced by external oceanic water masses, estuary input, and islands, phytoplankton subgroups show regional and seasonal variations. Despite recorded harmful algal blooms (HABs) in adjacent waters, Yazhou Bay’s high biodiversity and low cell density suggest a low HAB risk, though future risks due to climate change and human activities remain.

Dissolved PAHs in the Beibu Gulf and adjacent waters of the South China Sea: Physical and biochemical processes-driven distributional variations

Polycyclic aromatic hydrocarbons (PAHs) in semi-enclosed gulfs are influenced by physical and biochemical processes, which haven’t been well understood. This study aims to investigate the spatial distribution and vertical profiles of dissolved PAHs in the Beibu Gulf and adjacent waters of the South China Sea, along with hydrological, meteorological, and biochemical variables. Particularly relevant are the effects of atmospheric pressure, salinity, ammonium, chlorophyll-a, as well as riverine inputs (RI), sea currents, and upwelling. In surface seawater, the total concentrations of eight dissolved PAHs (∑8PAHs) were 7.76 ± 2.16ng/L, with a distribution pattern of western Guangdong waters (WGWs) > BG > Qiongzhou Strait (QS). ∑8PAHs in the northern BG (9.10 ± 2.00ng/L) was significantly higher than that in the southern BG (6.65 ± 1.54ng/L) (p < 0.01), suggesting that local anthropogenic activities and unique environmental characteristics significantly influenced PAHs distribution. In water column, PAHs in BG displayed enrichment in surface and bottom but decreased in medium water, while those in WGWs and QS decreased with increasing depth. Source apportionment concluded that PAHs in QS and WGWs were primarily from petroleum sources, and PAHs in BG were mainly from coal combustion. RI, combined with circulation, coastal current, and intrusion of SCS water influenced the surface PAHs distribution in BG, with eddy impacts observed. Specifically, regarding the surface PAHs distribution, differences in atmospheric pressure may influence the air-sea exchange of PAHs, especially positively affecting 4-ring PAHs. Salinity factors further corroborated the contribution of RI to 3-ring PAHs, followed by the regulation of PAHs through biological pumps (ammonia and chlorophyll-a). Moreover, upwelling-induced biodegradation and resuspension affected the vertical distribution of PAHs. While most PAHs posed a negligible risk, coking-generated fluorene posed a moderate risk to ecosystems due to changes in the energy structure, warranting further investigation into its toxicological impacts.

Skerki Bank (Strait of Sicily) is a hotspot of molluscan biodiversity: multiple new records for Tunisian waters and description of three new species

Sea bottom sampling of the Skerki Bank in the Strait of Sicily updates the census of marine molluscs inhabiting a biogeographically key sector of the Mediterranean Basin. One single dredge haul at 112-m depth yielded 110 molluscan species belonging to Gastropoda, Bivalvia, and Scaphopoda, of which 41 are new records for Tunisian jurisdictional waters, including three gastropod species new to science. Nearly all the species are shared with the fauna inhabiting the adjacent Italian waters, and most of them are reported also from Malta. We stress that sites characterized by a relevant species richness, diagnosed by hosting more than 100 species, inclusive of rare taxa, are important areas for conservation in need of adequate management.

Benthic diatom community response to the sudden rewetting of a coastal peatland

The coastline of the shallow southern Baltic Sea is a highly dynamic system of spits, lagoonal systems and subtidal flats. On the land side, coastal peatlands are common. Intact peatlands provide important ecosystem services, however, many peatlands have been severely degraded due to human activities. Many coastal peatlands are also separated from the Baltic Sea by artificial dunes or dykes in order to facilitate drainage and costal protection measures. Due to their potential to act as carbon sinks, as well as buffer zones against sea level rise and flooding events, there is an increasing interest in the restoration and rewetting of coastal peatlands. Microphytobenthic communities are important primary producers in coastal systems and peatlands and diatoms are often the dominant microphytobenthic group in temperate regions. In November 2019, the removal of the dyke that separated the Polder Drammendorf (a drained, oligohaline peatland), from the adjacent Baltic Sea lagoon Kubitzer Bodden represented a unique chance to study the sudden rewetting of a degraded coastal peatland with brackish water and its effect on the microphytobenthos. The aims of this study were to investigate the poorly known diatom community composition of coastal peatlands, to determine the effects of flooding events on diatom composition and biomass in coastal peatlands as well as the effects of nutrient and substance release from the peatlands on the diatom communities of adjacent coastal waters. We investigated and documented the impact of this sudden rewetting on the benthic diatom communities of the peatland and the adjacent lagoon over the course of one year, applying the latest taxonomy and measuring key environmental factors. The results deepen the understanding of diatom community composition, taxonomy and ecology and explore the influence of land-sea exchange processes on the benthic diatoms of the Baltic Sea coast.

Effects of Climate Change on the Distribution of Scomber japonicus and Konosirus punctatus in China’s Coastal and Adjacent Waters

Climate change has increasingly impacted the marine environment, with various marine environmental factors interacting to influence fish distribution. Assessing the impact of climate change on the future distribution of fish depends on understanding how biological responses interact with environmental conditions. Enhancing our understanding of the potential impacts of climate change is crucial for the sustainable development of marine fisheries. In this study, we analyzed the habitat suitability of Scomber japonicus and Konosirus punctatus in the coastal waters of China (17°–41° N, 107°–130° E) using marine environmental data, including, as follows: sea surface temperature (SST); sea surface salinity (SSS); pH; and biological occurrence data from 2000 to 2010. A maximum entropy (MaxEnt) model was employed to predict the future distribution of these two species based on the shared socioeconomic pathway (SSP) scenarios for 2040–2050 and 2090–2100. The results indicate that climate change will significantly affect the future habitat distribution of S. japonicus and K. punctatus, leading to a decrease in suitable habitat areas offshore China and a gradual shift northeastward in the center of these habitats. These findings are essential for understanding the impacts of climate change on the distribution of S. japonicus and K. punctatus, with significant implications for fisheries resource assessment and management.

Unveiling the structuring effects of eutrophication on macrobenthic biological traits in Hangzhou Bay and adjacent waters

Unveiling the structuring effects of eutrophication on macrobenthic biological traits in Hangzhou Bay and adjacent waters

Aggregation and transport of microplastics by a cold-core ring in the southern recirculation of the Kuroshio Extension: the role of mesoscale eddies on plastic debris distribution

Mesoscale eddies – ocean vortices with spatial scales of tens to hundreds of kilometers and time scales of months to years – are among the most energetic forms of flow in the ocean, and may act as significant transporters of floating microplastics. Yet, shipboard observation has thus far not clarified the abundance and transport of microplastics in mesoscale eddies. We conducted floating microplastic surveys in an intense cyclonic mesoscale eddy with a large sea surface height depression (approximately 0.8 m), a so-called cold-core ring, in the Kuroshio Extension recirculation gyre (KERG) southeast of Japan. The concentration of microplastics within the eddy (460 × 104 pieces/km2) was one or two orders of magnitude higher than in the adjacent oceanic waters, likely due to the acquisition of microplastics from the microplastic-rich Kuroshio Extension (KE) when detaching, as well as the horizontal entrainment of particles by the eddy. Our examination by using an assimilation product showed that most particles captured by the eddy remained within for several months while the eddy moved clockwise in the KERG. These results suggest that mesoscale eddies are of importance in the transportation and redistribution of microplastics on the ocean surface.

The characteristics of nutrient distribution and influencing factors in the Chukchi Plateau and adjacent waters

The Arctic is one of the regions under the most dramatic climate change. Global warming has led to elevated freshwater inflow into the western Arctic Ocean and significantly altered nutrient structure and biogeochemical cycling. In this work, inorganic dissolved nutrients in the Chukchi Plateau (CP) and adjacent regions were investigated to further understand their characteristics and influencing factors. Results showed that relatively high nutrient concentrations occurred in the water masses with salinity &amp;gt;32 psu, especially there was a nutrient-rich layer influenced by Winter Pacific Water in the water column (15.10±1.96, 2.23±0.26, and 23.46±6.64 µmol/L for DIN, PO43– and Si(OH)4, respectively). Contrarily, lower nutrient concentrations occurred in the mixing water of the upper layer (1.76±1.04, 1.15±0.16 and 3.76±2.29 µmol/L for DIN, PO43– and Si(OH)4, respectively) with a low DIN/P ratio (1.44±0.59), suggesting DIN has become the potentially biological limiting factor. Furthermore, the freshening and deepening of the upper layer driven by the Beaufort Gyre has hindered the nutrient transport from underlying layer into the upper layer. A maximum chla was observed at 36‒75 m water depth, and the phytoplankton biomass decreased from the western to the eastern CP, accompanied by a decreased contribution of micro-sized chla but an increased contribution of small-sized chla (74.0±0.1%). The phytoplankton resource use efficiency for DIN was estimated as (3.2±4.6)×10-3, which was primarily influenced by the physicochemical parameters of water and also largely regulated by the size structure of phytoplankton.

Distribution, community structure and assembly patterns of phytoplankton in the northern South China Sea.

A cruise was conducted in the summer of 2023 from the Pearl River Estuary (PRE) to the adjacent waters of the Xisha Islands in the northern South China Sea (NSCS) to investigate the distribution, community structure, and assembly patterns of eukaryotic and prokaryotic phytoplankton using high-throughput sequencing (HTS) and microscopic observation. Dinophyta were the most abundant phylum in the eukaryotic phytoplankton community based on HTS, accounting for 92.17% of the total amplicon sequence variants (ASVs). Syndiniales was the most abundant order among eukaryotic phytoplankton, whereas Prochlorococcus was the most abundant genus within cyanobacteria. The alpha diversity showed the lowest values in the PRE area and decreased gradually with depth, while cyanobacteria exhibited higher alpha diversity indices in the PRE and at depths ranging from 75 m to 750 m. The morphological results were different from the data based on HTS. Diatoms (37 species) dominated the phytoplankton community, with an average abundance of 3.01 × 104 cells L-1, but only six species of dinoflagellate were observed. Spearman correlation analysis and redundancy analysis (RDA) showed that the distribution and community structure of phytoplankton were largely influenced by geographical location and environmental parameters in the NSCS. The neutral community model (NCM) and null model indicated that deterministic processes played a significant role in the assembly of eukaryotic phytoplankton, with heterogeneous selection and homogeneous selection accounting for 47.27 and 29.95%, respectively. However, stochastic processes (over 60%) dominated the assembly of cyanobacteria and undominated processes accounted for 63.44%. In summary, the formation of eukaryotic phytoplankton was mainly influenced by environmental factors and geographic location, but the assembly of cyanobacteria was shaped by both stochastic processes, which accounted for over 60%, and environmental selection in the NSCS.

Ecosystem risk from human use of ocean space and resources: A case study from the Norwegian coast

Coastal and adjacent shelf waters are generally highly productive ecosystems harboring important ecological processes and exposed to a range of anthropogenic pressures from land-based and marine sectors. Ensuring that the cumulative pressures from human activities do not cause unacceptable, permanent harm to the ecosystem is challenging but crucial for sustainable management of these regions. Linkage frameworks and ecological risk assessments have proven to be useful tools for holistic evaluations of cumulative human pressures as a guide to managers and policy makers for prioritization of risk factors. Here, we present the first holistic assessment of ecosystem risk from human activities along the Norwegian coast. Pressures from coastal sectors are identified and weighted by the exposure to and potential impact on ecosystem components following the ODEMM (Options for Delivering Ecosystem-based Marine Management) framework. We focus on four coastal regions with contrasting scales of human activities. Two southern regions with multiple anthropogenic activities are associated with higher cumulative risk of negative impacts compared to northern areas where less extensive activities have a lower potential of harming the coastal ecosystems. Despite latitudinal differences in human use of the coastline, the pressures and ecosystem components associated with the greatest risk of cumulative impacts are relatively similar between the regions. Contaminants and underwater noise stand out as high-risk pressures, associated with multiple sectors with a high spatiotemporal footprint and with the potential to negatively impact a range of ecosystem components. Nevertheless, a confidence assessment also highlights the need for more in-depth analysis on the input, spread and effect of these pressures on coastal ecosystems. We discuss strengths and weaknesses of the risk assessment framework and suggest new directions which may enhance the utility and uptake of such assessments for sustainable management of coastal ecosystems.

Impact of engineering measures on water exchange and water quality in semi-closed bay: A model study in Zhelin Bay

Coastal aquatic environments are increasingly polluted due to human activities such as engineering, fishing, and agriculture. Semi-enclosed bays are particularly vulnerable to this issue due to weaker tidal currents and water circulation than open coastal areas. Although engineering measures, such as tidal channel dredging, have been implemented, their impact on semi-enclosed bays remains inadequately quantified. This study aimed to investigate the water exchange and water quality of Zhelin Bay, a semi-enclosed bay, after the implementation of two engineering measures: dredging the LG (Ligang) Channel and upgrading the SBM (Sanbaimen) Gate. The finite element model TELEMAC was used to simulate hydrodynamic processes before and after these two measures. The LG Channel dredging project increased flow velocity and tracer discharge during ebbing tides. The watergate project significantly reduced the semi-exchange time of adjacent waters. The combined two measures could enhance water exchange by up to 15 %. Furthermore, the projects slightly impacted spatial distribution of COD, while TP and TN levels near the SBM Gate decreased over by 80 %. This study represents the first effort to evaluate the water exchange improvement strategy of Zhelin Bay, a semi-enclosed bay with multiple tidal channels, and provides valuable insights for future research in marine ecology protection.

Distribution and bioaccumulation status of polycyclic aromatic hydrocarbons (PAHs) in Veraval coastal waters using copepods as bio-indicators.

The study investigates the pollution characteristics of 16 priority PAHs, accumulated in copepods from a major fishing harbour and its adjacent coastal waters of Veraval, west coast of India. The total PAH accumulation is in the range of 922.16-27,807.49ngg-1 dw, with the mean concentration of 5776.59ngg-1 dw. High concentrations of PAHs were present in the copepod samples from inside the harbour. Notably, there was no significant correlation between the lipid content of copepods and the accumulation of PAHs. The molecular diagnostic ratio method (MDR) indicates that the PAH sources are petrogenic in origin, while principal component analysis (PCA) points to petroleum, coal combustion and vehicular emission sources. Total cancerous PAHs (C-PAHs) in the study area dominate by 40% of the total PAHs identified; moreover, the bioaccumulation factor (BAF) is very high in the offshore area, which is also a fishing ground. The global relevance and magnitude of the present study in the Veraval, one of the prime seafood exporting hubs in India, should be dealt with utmost avidity as the accumulation status of PAHs in the zooplankton has never been explored in the Indian coastal waters. Moreover, the current study gives the foremost data on the bioaccumulation status of PAHs in copepods from the tropical waters of India.

Insights on long-term ecosystem changes from stable isotopes in historical squid beaks

BackgroundAssessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023.ResultsWe detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii’s trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century.ConclusionsOur results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids’ increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

Leveraging the genetic diversity of trout in the rivers of the British Isles and northern France to understand the movements of sea trout (Salmo trutta L.) around the English Channel.

Populations of anadromous brown trout, also known as sea trout, have suffered recent marked declines in abundance due to multiple factors, including climate change and human activities. While much is known about their freshwater phase, less is known about the species' marine feeding migrations. This situation is hindering the effective management and conservation of anadromous trout in the marine environment. Using a panel of 95 single nucleotide polymorphism markers we developed a genetic baseline, which demonstrated strong regional structuring of genetic diversity in trout populations around the English Channel and adjacent waters. Extensive baseline testing showed this structuring allowed high-confidence assignment of known-origin individuals to region of origin. This study presents new data on the movements of anadromous trout in the English Channel and southern North Sea. Assignment of anadromous trout sampled from 12 marine and estuarine localities highlighted contrasting results for these areas. The majority of these fisheries are composed predominately of stocks local to the sampling location. However, there were multiple cases of long-distance movements of anadromous trout, with several individuals originating from rivers in northeast England being caught in the English Channel and southern North Sea, in some cases more than 1000 km from their natal region. These results have implications for the management of sea trout in inshore waters around the English Channel and southern North Sea.

Characterization of Adverse Outcomes from Legacy-Contaminated Groundwater Exposure to Early Life Stages of Fathead Minnow.

Complex mixtures of chemicals present in groundwater at legacy-contaminated industrial sites can pose significant risks to adjacent surface waters. The combination of short-term molecular and chronic apical effect assessments is a promising approach to characterize the potential hazard of such complex mixtures. The objectives of this study were to: (1) assess the apical effects (survival, growth, development, and liver histopathology) after chronic exposure of early life stages (ELSs) of fathead minnows (FHM; Pimephales promelas) to contaminated groundwater from a legacy-contaminated pesticide manufacturing and packaging plant, and (2) identify possible molecular mechanisms responsible for these effects by comparing results to mechanistic outcomes previously determined by a short-term reduced transcriptome assay (EcoToxChips). This study revealed a significant increase in mortality and prevalence of spinal curvatures, as well as a significant reduction in the length of FHMs exposed to the groundwater mixtures in a concentration-dependent manner. There was an increasing trend in the prevalence of edema in FHMs, though not significantly different from controls. Additionally, no histopathological effects were observed in the liver of FHMs exposed to the groundwater mixtures. Short-term molecular outcomes determined in a parallel study were found to be informative of chronic apical outcomes, including cardiotoxicity, spinal deformities, and liver toxicity. Overall, the results observed in this study demonstrated that short-term transcriptomics analyses could support the hazard assessment of complex contaminated sites.

Remote-Sensing Estimation of Upwelling-Frequent Areas in the Adjacent Waters of Zhoushan (China)

Remote-Sensing Estimation of Upwelling-Frequent Areas in the Adjacent Waters of Zhoushan (China)

Urbanisation on the coastline of the most populous and developed state of Brazil: the extent of coastal hardening and occupations in low-elevation zones

Worldwide, coastlines have been replaced and altered by hard infrastructures to protect cities and accommodate human activities. In addition, human settlements are common and increasing in lowland areas threatened by coastal risk hazards. These urbanisation processes cause severe socioeconomic and ecological losses which demand policy reforms towards better coastal management and climate resilience. A first step in that direction is to comprehend the status of coastal hardening and occupation of vulnerable areas. Here, we mapped the coastline of the most populous and developed state of Brazil: São Paulo (SP). Our goal was to quantify the linear extent of natural habitats, artificial structures (AS), and occupations in low-elevation coastal zones (≤ 5 m) within 100 m from marine environments (LECZ100m) along the coastline and within estuaries. SP coast has a total extent of 244 km of AS, of which 125 and 119 km correspond to AS running along the coastline (e.g., seawalls, breakwaters) and extending from the shoreline into adjacent waters (e.g., jetties, pontoons, groynes), respectively. 63% of the total extent of AS is located in the most urbanised region. Breakwalls were the most common infrastructure (108 km), followed by jetties and wharves (~40 km each), and aquaculture and fishing apparatus (~24 km). Over 300 km of the SP coastline has inland occupations in LECZ100m: 235 and 67 km are adjacent to sandy beaches and estuarine/river margins, respectively. Coastal hardening is advanced in the central region of SP resulting from intense port activities and armoured shorelines. In other regions, much of coastal urbanisation seems to be driven by secondary usage of the cities, such as real estate development for beach houses and tourism. Our findings suggest that coastal urbanisation poses a major but often neglected source of environmental impact and risk hazards in SP and Brazil.

Variability in oceanographic conditions affecting Mesophotic Ecosystems along the South Eastern Pacific: Latitudinal trends and potential for climate refugia

Oceans have been changing at the fastest pace since the beginning of the Holocene. The South Eastern Pacific (SEP), including the Humboldt Upwelling Ecosystem (HUE) is subject to changes in upwelling winds, temperature, El Niño, and the ever-increasing local anthropogenic stressors, all of which have been documented for surface coastal waters where in-situ and remote observations are readily available. Temporal and spatial changes in the adjacent deeper waters where diverse Mesophotic Ecosystems are found have been scarcely documented. These marine ecosystems have been the focus of ecological studies for less than two decades. Here we provide an overview of the thermal variability at mesophotic depths and assess their potential as climatic refugia along all SEP ecoregions. We analyzed a time series of temperature and salinity from a 19 yr reanalysis based on remote and in-situ observations (CTD, ARGO, XBTs, moorings) to quantify variability in the Tropical (0–5°S), Northern Warm Temperate (5–30°S); Southern Warm Temperate (30–39.5°S) and Magellanic subregions (39.5–45°S), at two mesophotic depth strata (50 and 100 m), and a reference surface (5 m) depth. We assessed variability in the seasonal, interannual (El Niño) and ‘long-term’ (ca. 20 yr) scales, and the relationship with wind velocities. The thermal depth gradient between surface and mesophotic depths did not change smoothly with latitude but peaked within the northern portion of the warm temperate subregion, decreasing towards lower and higher latitudes. Seasonal variation in temperature was also largest in the north and south temperate subregions and minimal in the Magellanic subregion. Depth dampening of seasonal temperature variation was also strengthened at intermediate latitudes and much reduced in the tropics, where seasonal variation at mesophotic depths was similar to that at the surface. The strong interannual El Niño events were identified at all depths in tropical and temperate subregions, with stronger standardized effects at mesophotic layers than at the surface. Long-term (ca. two decades) temperature trends were significant and changed direction from warming to cooling along the SEP but were generally patchier at mesophotic layers. Spatial temperature gradients have remained relatively stable over the past two decades and were stronger at the surface than at mesophotic depths, and stronger within the tropics than in all other subregions. Surprisingly, the velocity of climate change was patchier and generally faster at mesophotic layers than at the surface. We conclude that, judging solely by physical environmental conditions, mesophotic ecosystems may be used by species with very different temperature affinities in temperate subregions, while in the tropics, more overlap in temperature affinities of component species may be found. Importantly, while the seasonal amplitude is reduced at mesophotic depth in most subregions, except the tropics, interannual disturbances affect mesophotic depths at least as strongly as they do surface waters and climate change velocities are faster at mesophotic depths than at surface. Thus, these ecosystems are not sheltered from inter-annual and longer-term forcing and their biotas might be more vulnerable to climate change than shallow coastal ecosystems.

Decoding the resistome, virulome and mobilome of clinical versus aquatic Acinetobacter baumannii in southern Romania

Acinetobacter baumannii, a notorious opportunistic pathogen, presents a formidable challenge in both clinical and environmental fields due to its resilience and ability to acquire resistance. This study undertook a comprehensive analysis of 183 A. baumannii isolates collected between 2019 and 2022 from intra-hospital infections (IHI), hospital sewages (Hs), wastewater treatment plants (WWTP), and adjacent river waters from two Southern cities, focusing on their resistome, virulome, and mobilome through isolation on chromogenic media, identification by MALDI-TOF-MS and antibiotic susceptibility testing by disk diffusion) followed by genotypic characterization [Whole Genome Sequencing (WGS), 3rd generation sequencing through the MinION (ONT) platform, pangenome description, and respectively horizontal gene transfer through conjugation assays]. Our findings reveal significant genomic plasticity and the prevalence of high-risk international clones, underlining the potential of these isolates to act as reservoirs for antibiotic resistance genes (ARGs) that could be dynamically exchanged between clinical and environmental settings through mobile genetic elements (MGEs) such as the pMAL1 plasmids and the critical role of WWTPs in the persistence and spread of A. baumannii. Moreover, our study presents the first report of the co-occurrence of blaOXA-23 and blaOXA-72 in A. baumannii ST2 clone. Thus, our research underscores the necessity for integrated surveillance and targeted interventions across healthcare and environmental sectors to mitigate the risk posed by this adaptable pathogen.