Offshore Surface Waters Research Articles

Distinct responses to warming within picoplankton communities across an environmental gradient.

Picophytoplankton are a ubiquitous component of marine plankton communities and are expected to be favored by global increases in seawater temperature and stratification associated with climate change. Eukaryotic and prokaryotic picophytoplankton have distinct ecology, and global models predict that the two groups will respond differently to future climate scenarios. At a nearshore observatory on the Northeast US Shelf, however, decades of year-round monitoring have shown these two groups to be highly synchronized in their responses to environmental variability. To reconcile the differences between regional and global predictions for picophytoplankton dynamics, we here investigate the picophytoplankton community across the continental shelf gradient from the nearshore observatory to the continental slope. We analyze flow cytometry data from 22 research cruises, comparing the response of picoeukaryote and Synechococcus communities to environmental variability across time and space. We find that the mechanisms controlling picophytoplankton abundance differ across taxa, season, and distance from shore. Like the prokaryote, Synechococcus, picoeukaryote division rates are limited nearshore by low temperatures in winter and spring, and higher temperatures offshore lead to an earlier spring bloom. Unlike Synechococcus, picoeukaryote concentration in summer decreases dramatically in offshore surface waters and exhibits deeper subsurface maxima. The offshore picoeukaryote community appears to be nutrient limited in the summer and subject to much greater loss rates than Synechococcus. This work both produces and demonstrates the necessity of taxon- and site-specific knowledge for accurately predicting the responses of picophytoplankton to ongoing environmental change.

Microplastics in the Inshore and Offshore Surface Water in the Andaman Sea

Microplastics in the Inshore and Offshore Surface Water in the Andaman Sea

A stable and moderate nitrate pool in largely anoxic Mesoproterozoic oceans and implications for eukaryote evolution

The Mesoproterozoic (1.6–1.0 Ga) is a particularly important interval in Earth history that witnessed the initial radiation of eukaryotic life. Ocean anoxia and nutrient limitation has been invoked to explain the delayed expansion of more complex, multicellular eukaryotes during the Mesoproterozoic. However, pulsed oxygenation events and elevated nitrate availability have been identified in shallow marine settings. In deeper waters, however, nitrate availability and potential links to eukaryotic evolution remain poorly constrained. Here, we report an integrated geochemical study based on multiple proxies conducted on two new drill-core sections from the ∼1460 Ma Hongshuizhuang Formation and the ∼1380 Ma Xiamaling Formation, North China. Iron speciation and redox-sensitive trace element systematics suggest dominantly ferruginous to weakly euxinic water column conditions during deposition of both units. Our data are consistent with previous inferences of persistently anoxic deep water conditions in Mesoproterozoic oceans. Exclusively positive δ15N (+3.1 ± 0.8 ‰) values reveal the operation of partial denitrification in the water column, implying a relatively stable and moderate nitrate pool in offshore surface waters. Furthermore, a compilation of the Mesoproterozoic sedimentary δ15N record suggests a global nearshore to offshore oceanic nitrate gradient, with minimal but still bioavailable nitrate in offshore environments. The overall size of the nitrate pool was therefore apparently smaller than that of eukaryote-dominated modern oceans. Coupling Mesoproterozoic sedimentary δ15N data with fossil and biomarker records, we propose that this moderate level of nitrate may have been able to sustain a relatively low abundance of eukaryotic primary producers in the marine ecosystem, but was still not sufficient to trigger eukaryotic diversification and the rise of eukaryotes to ecological dominance.

Can microplastics in offshore waters reflect plastic emissions from coastal regions?

Marine microplastic pollution is a major environmental challenge that threatens marine ecosystems and human health. Several models have been used to calculate and predict the theoretical amount of plastic waste discharged into the sea by coastal countries. Unlike earlier theoretical models of source discharge, we used the method of data normalisation to focus on the actual distribution of microplastics and their potential ecological risk in offshore surface waters. Our findings indicate that the average normalised abundance of microplastics in near-shore region of Bohai Sea was greater than the average normalised abundance of microplastics in the seas near the Yangtze River Delta urban agglomeration and the Pearl River Delta urban agglomeration. Moreover, the average amount of plastic waste discharged from terrestrial sources to the ocean per kilometre exhibited the following order: Bohai Rim urban agglomeration (150.90) (tonnes km−1) < the Pearl River Delta urban agglomeration (274.30) (tonnes km−1) < Yangtze River Delta urban agglomeration (577.44) (tonnes km−1). Further, the average microplastics abundance in offshore areas of different countries and the amount of plastic discharged per kilometre of the coastline were significantly negatively correlated, implying that microplastics were not necessarily abundant in coastal areas where large amounts of plastic are discharged into the sea. Hydrodynamic conditions had the greatest influence on the distribution of microplastics in offshore surface waters. The transport of nutrient salts from terrestrial areas to offshore waters was also influenced by hydrodynamics, with enrichment patterns in offshore areas exhibiting similar to those of microplastics. Therefore, when the offshore microplastic accumulation area overlapped with the nutrient salt enrichment zone, the health risk associated with the consumption of edible fish from offshore communities increased. In view of these findings, coastal countries must implement policies to reduce marine plastic waste emissions and develop management strategies based on their local pollution levels.

Comprehensive analysis of spatial distribution of microplastics in Rawal Lake, Pakistan using trawl net and sieve sampling methods

Occurrence of microplastics (MPs) in freshwater environments, particularly reservoir and lakes, is an emerging concern. There are limited studies in Pakistan on microplastic pollution in the lacustrine environments and those that exist do not provide sufficient information on the spatial distribution of MPs in offshore surface water. The aims of this study were to determine microplastic abundance in Rawal Lake, Pakistan and to ascertain if sampling methodology influences microplastic counts. Surface water samples were collected from 10 sites; 5 tributaries, 2 human settlement and 3 fishing and boating areas using two different sampling techniques: 100 μm mesh trawl and 20 L sample through a 45 μm mesh sieve. A significant difference was observed in the abundance of MPs across two methods with the sieve method yielding 2.8 ± 1.44 particles/L and trawl yielding 0.025 ± 0.024 particles/L. Tributaries and boating/fishing area had higher microplastic abundance than the residential area regardless of sampling method. Filaments were the dominant shape of MPs in both type of samples followed by fragments in trawl samples and films in sieved samples. Microbeads were only detected in trawl samples. MPs within size range 0.1–0.9 mm were mostly fragments (82%). MPs were diverse in colors with white/transparent and black MPs common. Polypropylene was the main type of microplastic in Rawal Lake (40–74%). Scanning Electron Microscopy (SEM) of MPs showed cracks, roughness and striations on the particles. Energy Dispersive Spectroscopy (EDS) detected heavy metals (Fe, Cu, Ni, Pb, Zn, Co and Cr) in MPs. Findings suggest that microplastic pollution in Rawal Lake may pose great risk to aquatic and human life through leaching of inherent/adsorbed heavy metals and therefore requires future investigation.

Temperature variations in the northern Gulf of Alaska across synoptic to century-long time scales

Surface and subsurface moored buoy, ship-based, remotely sensed, and reanalysis datasets are used to investigate thermal variability of northern Gulf of Alaska (NGA) nearshore, coastal, and offshore waters over synoptic to century-long time scales. NGA sea surface temperature (SST) showed a larger positive trend of 0.22 ± 0.10 °C per decade over 1970–2021 compared to 0.10 ± 0.03 °C per decade over 1900–2021. Over synoptic time scales, SST covariance between two stations is small (<10%) when separation exceeds 100 km, while stations separated by 500 km retain 50% of their co-variability for seasonal and longer fluctuations. Relative to in situ sensor data, remotely sensed SST data has limited accuracy in some NGA settings, capturing 60–70% of the daily SST anomaly in coastal and offshore waters, but often <25% nearshore. North Pacific and NGA leading modes of SST variability leave 25–50% of monthly variance unresolved. Analysis of the 2014–2016 Pacific marine heatwave shows that NGA coastal surface temperatures warmed contemporaneously with offshore waters through 2013, but deep inner shelf waters (200–250 m) exhibited delayed warming. Offshore surface waters cooled from 2014 to 2016, while shelf waters continued to warm from the combined effects of local air-sea and advective heat fluxes. We find that annually averaged Sitka air temperature is a leading predictor (r2 = 0.37, p < 0.05) for following-year NGA coastal water column temperature. Our results can inform future environmental monitoring designs, assist forward-looking projections of marine conditions, and show the importance of in situ measurements for nearshore studies that require knowledge of thermal conditions over time scales of days and weeks.

Contrasting responses of phytoplankton productivity between coastal and offshore surface waters in the Taiwan Strait and the South China Sea to short-term seawater acidification

Abstract. Seawater acidification (SA) has been documented to either inhibit, enhance, or result in no effect on marine primary productivity (PP). In order to examine the effects of SA in changing environments, we investigated the influences of SA (a decrease of 0.4 pHtotal units with corresponding CO2 concentrations in the range of 22.0–39.7 µM) on PP through deck-incubation experiments at 101 stations in the Taiwan Strait and the South China Sea, including the continental shelf and slope, as well as the deep-water basin. The daily primary productivities in surface seawater under incident solar radiation ranged from 17–306 µg C (µg Chl a)−1 d−1, with the responses of PP to SA being region-dependent and the SA-induced changes varying from −88 % (inhibition) to 57 % (enhancement). The SA treatment stimulated PP in surface waters of coastal, estuarine, and shelf waters but suppressed it in the South China Sea basin. Such SA-induced changes in PP were significantly related to in situ pH and solar radiation in surface seawater but negatively related to salinity changes. Our results indicate that phytoplankton cells are more vulnerable to a pH drop in oligotrophic waters. Contrasting responses of phytoplankton productivity in different areas suggest that SA impacts on marine primary productivity are region-dependent and regulated by local environments.

Retraction Note: Voice-assisted translation of English vocabulary for offshore surface water temperature and trade

Retraction Note: Voice-assisted translation of English vocabulary for offshore surface water temperature and trade

Retraction Note to: Change of offshore surface water temperature characteristics based on Bayesian regression and physical recovery of sports training

In this paper, a simple Bayesian distribution regression learning framework based on probability multi-scale kernel (RMK-BDR) is proposed to study the variation of offshore surface water temperature characteristics and the physical recovery of sports training based on Bayesian regression, which can solve the distribution regression problem of complex data. In the first stage of distributed regression learning, the average embedded estimator of the limited dimension of the same dimension is introduced. Through this method, the number of optimal center points can be adaptively selected according to the sample set, so as to avoid the influence on the sample size of inconsistent regression modeling. Climate change is the most important environmental problem in today’s society. The East China Sea and its adjacent Northwest Pacific have a very important impact on China’s climate. In recent years, it has gradually evolved into an area of international concern. The ocean can transport the heat storage to the atmosphere through the heat exchange between the ocean and the air, promote the movement of the atmosphere through the heat change, and affect the atmospheric cycle. Therefore, it is very important to study the annual and decades’ temporal and spatial variation of sea water temperature around China. At the same time, with the rapid development of basketball, the physical requirements of athletes are also higher and higher. There are many ways to improve the physical strength of basketball players. In addition to scientific training, nutritional support is also an important part. However, for a long time, the lack of understanding of nutritional support and the lack of relevant theoretical support have made nutritional support not fully applied in the basketball field.

Barrier Effect of the Pearl River Estuarine Plume on Wind‐Induced Coastal Upwelling of Nutrients

AbstractCoastal upwelling caused by winds seasonally occurs in summer in the Northern South China Sea. The alongshore prevailing southwest winds, induced by East Asia Summer Monsoon, exert a uniform Coriolis force to drive the surface water offshore, which in turn pushes the deeper coastal water upward. The common view is that coastal upwelling brings up nutrients from deep water. The presence of a buoyance layer such as the riverine or estuarine plumes damps the Ekman effect and hence upwelling. However, the semi‐quantitative analysis of reduced upwelled nitrate amount due to plume (barrier) effect during this interactive process is rare. To examine the dynamics of water masses and nutrient upward transport process in the coastal waters in summer, vertical profiles of temperature, salinity, and nitrate were taken along the transects from the Pearl River estuary to 150 km offshore in July cruise of 2002 in the northern South China Sea. The results show a three‐layer structure resulting from the three water masses under the impact of a large buoyant plume: high‐nutrient plume water in the surface layer, undetectable‐nutrient offshore surface water in the middle layer, and low‐nutrient deep water in the bottom layer. This structure indicates that this middle layer was the offshore surface water entrained underneath the estuarine plume and hence, weakened the intensity of upwelling. Upwelled nitrate amount is reduced by ∼30%–35% from the deep water to the surface layer due to the middle layer based on our estimate. The finding suggests that the presence of estuarine plumes plays an important role as a barrier to weaken upwelling of deep water and subsequently reduce the upward transport of nutrients by wind‐induced coastal upwelling and therefore, such the barrier effect should be considered in estimating budgets of nutrients and subsequent carbon fixation in coastal waters.

RETRACTED ARTICLE: Change of offshore surface water temperature characteristics based on Bayesian regression and physical recovery of sports training

RETRACTED ARTICLE: Change of offshore surface water temperature characteristics based on Bayesian regression and physical recovery of sports training

RETRACTED ARTICLE: Voice-assisted translation of English vocabulary for offshore surface water temperature and trade

RETRACTED ARTICLE: Voice-assisted translation of English vocabulary for offshore surface water temperature and trade

Limnological changes in Lake Victoria since the mid‐20th century

Abstract Lake Victoria experienced a strong degradation of water quality between the 1960s and the 1990s and, as a consequence of eutrophication, the dominant phytoplankton group changed from diatoms to N2‐fixing cyanobacteria and there was a 2‐ to 10‐fold increase in chlorophyll‐a. The goal of this study is to determine whether the 2018–2019 physical (light, stratification) and ecological (nutrient, chlorophyll‐a, phytoplankton composition) conditions in Lake Victoria changed from the 1990s. Samples were collected in 2018–2019 in nearshore and offshore waters (Uganda), during three contrasting seasons: heavy rains (March), low rains (October), and dry (June), which corresponded to distinct water column mixing regimes, respectively, late‐stratified, early‐stratified, and mixed regimes. At each station (48 nearshore and 25 offshore), we measured vertical profiles of temperature, oxygen, phytoplankton biomass and composition, inorganic nutrients, and particulate organic carbon, particulate nitrogen (N), and phosphorus (P). Chlorophyll‐a concentrations in 2018–2019 were 10.3 ± 7.1 and 2.8 ± 1.1 µg/L in the nearshore and offshore surface waters, respectively, close to those measured in the 1960s before eutrophication, but distinctly lower than those measured in the 1990s (71 ± 100 and 14 ± 6 µg/L). The phytoplankton of Lake Victoria in 2018–2019 still appears dominated by diatoms and cyanobacteria. However, we observed more non‐heterocystous filamentous and coccal/colonial cyanobacteria taxa that are better adapted to mixing conditions than gas‐vacuolated heterocystous taxa, which were dominant in the 1990s. Particulate N was significantly lower in 2018–2019 than in the 1990s, indicative of less efficient N fixation. The dissolved silica concentrations in 2018–2019 were significantly higher with the concomitant reappearance of Aulacoseira spp., which was not observed in the 1990s, presumably due to low dissolved silica concentrations. As data from long‐term monitoring are absent, the reasons for the lower chlorophyll‐a concentrations in 2018–2019 compared to the 1990s are unclear. However, climatic controls (El Niño/La Niña conditions) may be an important factor influencing the historical trend in chlorophyll‐a. Higher wind in 2018–2019 promoted vertical mixing, resulting in a deeper thermocline and surface mixed layers, which eventually lowered phytoplankton production in comparison to the 1990s. In contrast, the thermocline and surface mixed layers in the 1990s were shallower, enabling phytoplankton to stay suspended in the upper well illuminated water, allowing greater productivity. The lake in 2018–2019 is still P saturated, suggesting that another episode of high chlorophyll‐a concentrations could develop if less windy conditions occur in future, or if continued warming of surface waters eventually overcomes the mixing from present windy conditions. This study gives insights about the present ecological functioning of Lake Victoria and emphasises the impacts of variations in climate on lake physics that changes the light environment for phytoplankton. A possible less windy period in the future resulting from a new El Niño phase or from climate change, will probably lead to another episode of eutrophication in Lake Victoria. As in 2018–2019 the lake was still saturated by nutrients, there is need to reduce the nutrient concentrations (especially P) to prevent future destructive eutrophic periods caused by reduced mixing.

Microplastic pollution in inshore and offshore surface waters of the southern Caspian Sea

In this study, as the first comprehensive monitoring, the occurrence of microplastics (MPs) in inshore and offshore surface waters of the southern Caspian Sea was investigated. Our data indicated that MPs, which were detected in all the samples, were widely distributed in the thirteen studied stations. Non-normally distribution of the MPs was observed among the studied stations (p<0.05). The average concentration of microplastics in the selected stations was 0.246 ± 0.020 MP/m3. In most of the transects, negative gradients of MPs from coastal waters to deeper waters were observed. The dominant size and color of MPs in the inshore and offshore water samples was 1000–5000 μm and white-transparent, respectively. Films and fibers constituted about 50% and 40% of the total number of MPs of the water samples, respectively. Also, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were the three main polymer types of microplastics in the inshore and offshore surface waters. Our data provide valuable evidence for the comparative assessing of future data regarding decreases or increases of MPs in the southern Caspian Sea.

A Shelf Water Cascading Event near Cape Hatteras

AbstractCarbon-rich Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB) shelf waters typically converge on the continental shelf near Cape Hatteras. Both are often exported to the adjacent open ocean in this region. During a survey of the region in mid-January 2018, there was no sign of shelf water export at the surface. Instead, a subsurface layer of shelf water with high chlorophyll and dissolved oxygen was observed at the edge of the Gulf Stream east of Cape Hatteras. Strong cooling over the MAB and SAB shelves in early January led to shelf waters being denser than offshore surface waters. Driven by the density gradient, the denser shelf waters cascaded beneath the Gulf Stream and were subsequently entrained into the Gulf Stream, as they were advected northeastward. Underwater glider observations 80 km downstream of the export location captured 0.44 Sv of shelf waters transported along the edge of the Gulf Stream in January 2018. In total, as much as 7×106 kg of carbon was exported from the continental shelf to a greater depth in the open ocean during this 5-day-long cascading event. Earlier observations of near-bottom temperature and salinity at a depth of 230 m captured several multiday episodes of shelf water at a location that was otherwise dominated by Gulf Stream water, indicating that the January 2018 cascading event was not unique. Cascading is an important, yet little-studied pathway of carbon export and sequestration at Cape Hatteras.

Pollution by anthropogenic microfibers in North-West Mediterranean Sea and efficiency of microfiber removal by a wastewater treatment plant

The widespread pollution from the release of microfibers is an emerging concern as they are a potential threat to the environment. Their identification in samples in terms of quantity and pathways remain a challenge as contamination can be a major source of error. A systematic study of synthetic microfibers (MFs) has been carried out in different environmental compartments of an urban area and in the surface waters of the northwestern Mediterranean.The quantity, size and type of polymer of MFs were recorded in air, in waste water from a domestic washing machine, at the inlet and outlet of the Haliotis urban wastewater treatment plant (WWTP) in Nice (Provence Alpes Côte-d'Azur, France) and in a variety of coastal and offshore areas. The results showed that MFs released by clothes during washing (on average of 13 × 106 MFs per m3) are an important emitter of microplastics. Despite its high removal efficiency (87.5% to 98.5%) by Haliotis, a large number of MFs, estimated at 4.3 billion, enter the marine environment daily from the treatment plant. The attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterization of the raw materials showed that 14 to 50% of fibers are synthetic, mostly polyester and polyamide, the remaining 35 to 72% being natural polymers (cotton, wool) or manufactured by processing natural polymers (especially cellulose). MFs were found in all environmental compartments studied and appear to be widespread in coastal and offshore surface waters with concentrations varying from 2.6 × 103 to 3.70 × 104 m−3. The sources of MFs in the marine environment are multiple, with laundry fibers discharges from WWTP and the atmospheric transport of urban fibers are among the main pathways.

Spatial and temporal variability of trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, Pb), iron and copper speciation, and electroactive Fe-binding humic substances in surface waters of the eastern Gulf of Mexico

The concentrations of bioactive trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, and Pb), Fe-and Cu-binding organic ligands, and electroactive Fe-binding humic substances were measured in surface waters across the West Florida Shelf in the eastern Gulf of Mexico in June 2015 and in February-March 2018. Seasonal differences in dust deposition were associated with increased concentrations of Fe, Mn and Pb in offshore surface waters in June 2015 compared to Feb-Mar 2018. Total concentrations of Fe-binding ligands offshore were similar between seasons, and this ambient ligand pool acted to stabilize a portion of Fe delivered via dust deposition within the dissolved fraction. Apparent photoreduction of Cu-binding organic ligands in offshore summer surface waters led to bioavailable Cu2+ concentrations that could potentially inhibit the growth of some cyanobacteria species. The concentrations of Fe-binding humic-like ligands were better correlated with Cu-binding ligands than Fe-binding ligands, suggesting that terrestrially derived photoactive ligands may have a significant influence on the cycling of Cu-binding ligands across the West Florida Shelf. Intrusion of the Loop Current into the study region was observed in June 2015 and appeared to entrain bands of low salinity water from the northern Gulf of Mexico. This process brought elevated trace metals and Fe-binding humic-like ligands to the outer West Florida Shelf, which may then be delivered to the North Atlantic via the Loop Current-Florida Current-Gulf Stream system.

Seasonal dynamics of prokaryotes and their associations with diatoms in the Southern Ocean as revealed by an autonomous sampler.

The Southern Ocean remains one of the least explored marine environments. The investigation of temporal microbial dynamics has thus far been hampered by the limited access to this remote ocean. We present here high-resolution seasonal observations of the prokaryotic community composition during phytoplankton blooms induced by natural iron fertilization. A total of 18 seawater samples were collected by a moored remote autonomous sampler over 4 months at 5-11 day intervals in offshore surface waters (central Kerguelen Plateau). Illumina sequencing of the 16S rRNA gene revealed that among the most abundant amplicon sequence variants, SAR92 and Aurantivirga were the first bloom responders, Pseudomonadaceae, Nitrincolaceae and Polaribacter had successive peaks during the spring bloom decline, and Amylibacter increased in relative abundance later in the season. SAR11 and SUP05 were abundant prior to and after the blooms. Using network analysis, we identified two groups of diatoms representative of the spring and summer bloom that had opposite correlation patterns with prokaryotic taxa. Our study provides the first seasonal picture of microbial community dynamics in the open Southern Ocean and thereby offers biological insights to the cycling of carbon and iron, and to an important puzzling issue that is the modest nitrate decrease associated to iron fertilization.

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.

Comparison of bacterial community structure in coastal and offshore waters of the Bay of Bengal, India

Bacterial community structure was analysed from the coastal and offshore surface waters of the Bay of Bengal (BoB) using of Next Generation Sequencing (NGS) approach. Taxonomic richness was high in the offshore waters compared to the coastal waters. Analysis of sequence data revealed that both the offshore and coastal waters in our study were dominated by Proteobacteria (67.14% and 61.91%, respectively). The most dominant genera in the coastal waters were Synechococcus, Erythrobacter, Psychrobacter while Prochlorococcus, and Vibrio were dominant in the offshore waters. Interestingly, the distribution of minor phyla was distinctly different in coastal and offshore environments. Fusobacteria, Synergistetes, Fibrobacteres, Spirochaetes, Gemmatimonadetes, Chlorobi, Chlamydiae, and Armatimonadetes were the minor phyla (6.84%) present in offshore waters. The metabolic predictions of the bacterial communities revealed distinctly different activities in the coastal and offshore water samples, which could be attributed to the differences in the physico-chemical conditions and substrate availability. Major functions included sulfate reduction, oxalic acid degradation, dehalogenation, nitrite reduction, ammonia oxidation, nitrogen fixation, xylan degradation, and aromatic hydrocarbons degradation.