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Current knowledge of the vertical distribution of Triturus macedonicus places the species at altitudes up to 2140 m. Herein, we report its presence in the alpine lake Gistova at 2360 m on Mt. Grammos, Greece, thus extending the highest altitudinal point for the species, as well as for the Triturus genus. This record showcases the adaptive capacity of the Macedonian newt, which allows it to occupy markedly different environments. More populations may exist at similar or even higher altitudes and their discovery could positively impact conservation efforts. [ABSTRACT FROM AUTHOR]

In this study we present an approach that uses polarimetric variables from a scanning polarimetric cloud radar MIRA-35 in the 45° slanted linear depolarization (SLDR) configuration, to derive the vertical distribution of particle shape (VDPS) between top and base of mixed-phase cloud systems. The polarimetric parameter SLDR was selected for this study due to its strong sensitivity to shape and low sensitivity to the wobbling effect of particles at different antenna elevation angles. For the VDPS method, elevation scans from 90° to 30° elevation angle were deployed to estimate the vertical profile of the particle shape by means of the polarizability ratio, which is a measure of the density-weighted axis ratio. Results were obtained by retrieving the best fit between observed SLDR-vs-elevation dependencies and respective values simulated with a spheroid scattering model. The applicability of the new method is demonstrated by means of three case studies of isometric, columnar and oblate hydrometeor shapes, respectively, which were obtained from measurements at the Mediterranean site of Limassol, Cyprus. The identified hydrometeor shapes are demonstrated to fit well to the cloud and thermodynamic conditions which prevailed at the times of observations. Some observations reveal that in mixed-phased clouds ice particle shapes tend to evolve from a pristine columnar or dendritic state at cloud top toward a more isometric shape at cloud base. Either aggregation or riming processes contribute to this vertical change of microphysical properties. The new height-resolved identification of hydrometeor shape and the potential of the VDPS method to derive its vertical distribution are helpful tools to understand complex processes such as riming or aggregation, which occur particularly in mixed-phase clouds. [ABSTRACT FROM AUTHOR]

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Effects of aquaculture on hydrodynamics and associated nutrient supply in a typical aquaculture area of the coastal Yellow Sea are investigated with high‐resolution model experiments and in situ data. The results show a significant reduction in nutrient supply, which is associated with alternations of three hydrodynamic conditions: the onshore current across the outer‐boundary of aquaculture area, upwelling within the offshore (depth >10 m) aquaculture area, and water exchange in the near‐coastal (depth <10 m) aquaculture area. First, the onshore current in the bottom layer of the aquaculture boundary, which transports high‐concentration nutrients from the major nutrient source of offshore bottom water, is significantly weakened by suspended aquaculture. As a result, nutrient supply from offshore sources is reduced by 50%−60%. Second, the upwelling velocities in the offshore aquaculture area are reduced by 2–6 × 10−3 cm/s, which leads to an approximately 25% reduction in nutrient supply to the euphotic layer. Third, the water exchange in the near‐coastal aquaculture area remains approximately unchanged because the weakened onshore currents within the aquaculture layers (0–4 m) are compensated by the enhanced onshore currents in the lower layers. As a result, the nutrient supply in the near‐coastal aquaculture area does not significantly change, whereas the nutrient supply in the offshore aquaculture area has been reduced by approximately 60%. Plain Language Summary: Coastal aquaculture has become the largest source of seafood for human consumption in many countries, and China contributes 60% of global aquaculture production. As the largest contributor to Chinese aquaculture production, the coastal aquaculture sites in the Yellow Sea have expanded to depths between 20 and 30 m in recent years, while excessive aquaculture results in nutrient deficiency that has been associated with weakened hydrodynamics. Through nutrient observations and high‐resolution simulations at a typical aquaculture site, we investigated the impact of suspended aquaculture on hydrodynamics and the associated nutrient supply in the coastal aquaculture area of the Yellow Sea (China). Our results show that a significant reduction in nutrient supply, which is associated with alterations in onshore currents across the aquaculture boundary, upwelling within the offshore (>10 m) aquaculture area, and water exchange in the near‐coastal (<10 m) aquaculture area. Specifically, suspended aquaculture weakens the onshore current near the aquaculture boundary and upwelling within the offshore aquaculture area and changes the vertical distribution of the onshore currents near the bay boundary. As a result, approximately 60% of the high‐nutrient water in the offshore aquaculture area is reduced. Key Points: Suspended aquaculture weakens the onshore current near the aquaculture boundary, resulting in a reduction of 50%−60% in nutrient supplyNutrient supply to the euphotic layer is further reduced by approximately 25% owing to weakened upwelling in the offshore aquaculture areaNutrient supply in near‐coastal area does not significantly change mainly because onshore current remains unchanged [ABSTRACT FROM AUTHOR]

The present work aimed to evaluate the influence of Stylosanthes spp. (Campo Grande© styles) and Brachiaria brizantha cv. Marandu in the vertical migration of Haemonchus spp. infective larvae, in the region of Uberlândia, Minas Gerais. Seeds of Stylosanthes spp. and Brachiaria brizantha cv. Marandu were planted in 50 pots of five liters (20 cm diameter) evenly disposed in an area of the Capim Branco Experimental Farm, Federal University of Uberlândia. When both species reached the minimum height of 20 cm, the pots were experimentally contaminated with sheep feces coprocultures. Samplings were performed, with complete removal of the vegetal material contained in the pots, on days one, three, six, 10 and 14 after contamination. Nematoids were recovered from the plant samples by thermo and hydrotropism, counted under an optical microscope and identified. For statistical analysis, the data were analyzed in a completely randomized design (DIC) in a 2X5 factorial scheme (two fodder species X 5 collection dates). No effect of the forage species was observed on the number of L3 of Haemonchus sp. recovered in the feces (p = 0.7790), upper stratum (p = 0.1755) or lower stratum (p = 0.7883) of the forage, however, there was a significant decrease in the number of L3 found with the passing of the days. When comparing the mean L3 recovered in the upper (0.06±0.31 L3) and lower (2.94±0.39) strata, a higher number of larvae was observed in the lower stratum (p < 0.0001). Therefore, in both forage species studied, the upper stratum of the plants, preferably pastured by the animals, remained with less contamination of infective larvae and the contamination tended to decrease over the days. [ABSTRACT FROM AUTHOR]

Trait structure is increasingly used in plankton ecology to understand diversity and biogeography. However, our knowledge of microzooplankton (e.g. planktonic ciliates) trait structure and its variation with hydrography is limited. In this study, we analyzed planktonic ciliate trait structure in waters with different hydrography and deep Chlorophyll a maximum (DCM) layers over three seamounts: Yap, Mariana, and Caroline seamounts. Mariana seamount had a lower surface temperature than the Yap and Caroline seamounts. DCM layers over Mariana and Caroline seamounts were deeper than Yap seamount. There was a weak upwelling in upper 50 m around top of Mariana seamount. The ciliate distribution showed bimodal pattern (high abundance appeared in the surface and DCM layers) over three seamounts. At surface layer, the large size-fraction (>30 µm) abundance proportion to aloricate ciliate over Yap seamount (44.4%) was higher than Mariana (32.8%) and Caroline (36.1%) seamounts. For tintinnid abundance proportion to total ciliate, Mariana (12.0%) and Caroline (11.5%) seamounts at about 100-m depth were higher than that of Yap seamount (6.4%). Vertically, tintinnid could be divided into 4 groups over the three seamounts. At 30-m depth, group I (species occurring from surface to 100 m only) was dominant component over Yap and Caroline seamounts, while group IV (species occurring at every depth) changed into dominant component over Mariana seamount, the weak upwelling might be the reason. Salpingella faurei was the top dominant species, which corresponded to deeper DCM layers over Mariana and Caroline seamounts. Our results showed that the upwelling and the deeper DCM could influence the planktonic ciliate trait structure. [ABSTRACT FROM AUTHOR]

Investigations on meteor trail decay time and its evolution in the mesosphere and lower thermosphere are very important to estimate the temperature in this region. The present study focuses on the vertical distribution of meteor decay times at three different latitudes to understand the mechanism responsible for the deviation of meteor decay time from the theoretical estimations below 90 km of altitude. The present study is based on measurements from three identical meteor radars located at equatorial (Kototabang: 0.2° S, 100.3° E), low (Thumba: 8.5° N, 76.9° E) and polar latitudes (Eureka: 80.0° N, 85.8° W). The results reveal a pronounced seasonal variation of vertical distribution of meteor decay time turning altitude (inflection point) over polar latitudes as compared to that over equatorial and low latitudes. Apart from direct estimations from meteor radar observations, the meteor decay time is estimated using temperature and pressure measurements from the SABER/TIMED. Above 90 km of altitude, decay times estimated from both methods are in good agreement. However, below 90 km of altitude, these estimations start deviating and it has been noted that the deviation increases with decreasing altitude. Further, observed meteor decay times correlated with ozone concentration at three representative altitude bins. The correlation analysis reveals a significant negative correlation at 80 - 90 km of altitude over the three latitudes indicating that an increase in ozone concentration results in decrease in meteor decay time. The significance of the present results lies in analyzing the vertical distribution of meteor decay time simultaneously from three radar locations representing equatorial, low and polar latitudes and evaluating the relation between ozone concentration and meteor decay time, quantitatively. [ABSTRACT FROM AUTHOR]

As zooplanktivorous predators, bowhead whales (Balaena mysticetus) must routinely locate patches of prey that are energy-rich enough to meet their metabolic needs. However, little is known about how the quality and quantity of prey might influence their feeding behaviours. We addressed this question using a new approach that included: (1) multi-scale biologging and unmanned aerial system observations of bowhead whales in Cumberland Sound, Nunavut (Canada), and (2) an optical plankton counter (OPC) and net collections to identify and enumerate copepod prey species through the water column. The OPC data revealed two prey layers comprised almost exclusively of lipid-rich calanoid copepods. The deep layer contained fewer, but larger, particles (10% greater overall biomass) than the shallow prey layer. Dive data indicated that the whales conducted long deep Square-shaped dives (80% of dives; averaging depth of 260.4 m) and short shallow Square-shaped dives (16%; averaging depth of 22.5 m) to feed. The whales tended to dive proportionally more to the greater biomass of zooplankton that occurred at depth. Combining behavioural recordings with prey sampling showed a more complex feeding ecology than previously understood, and provides a means to evaluate the energetic balance of individuals under current environmental conditions. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosols influence precipitation through a range of processes. The climate response to the presence of BC is however highly dependent on its vertical distribution. Here, we analyze the changes in the energy budget and precipitation impacts of adding a layer of BC at a range of altitudes in two independent global climate models. The models are run with atmosphere‐only and slab ocean model setup to analyze both fast and slow responses, respectively. Globally, precipitation changes are tightly coupled to the energy budget. We decompose the precipitation change into contributions from absorption of solar radiation, atmospheric longwave radiative cooling, and sensible heat flux at the surface. We find that for atmosphere‐only simulations, BC rapidly suppresses precipitation, independent of altitude, mainly because of strong atmospheric absorption. This reduction is offset by increased atmospheric radiative longwave cooling and reduced sensible heat flux at the surface, but not of sufficient magnitude to prevent reduced precipitation. On longer timescales, when the surface temperature is allowed to respond, we find that the precipitation increase associated with surface warming can compensate for the initial reduction, particularly for BC in the lower atmosphere. Even though the underlying processes are strikingly similar in the two models, the resulting change in precipitation and temperature by BC differ quite substantially. Plain Language Summary: Soot particles change precipitation by absorbing solar radiation and heating the surrounding air. The atmosphere rapidly adjusts to this added warming by changing relative humidity, clouds, and precipitation. We use two climate models to investigate these rapid adjustments in the atmosphere caused by soot particles. We insert soot particles in different vertical layers in the models and find that soot particles quickly warm the atmosphere and reduce precipitation. Soot particles at higher altitudes stabilize the atmosphere and increase cloud cover located below. Given all the processes soot particles influence in the atmosphere, the similarities in underlying processes by the two climate models are striking. The resulting change in precipitation and temperature differ quite substantially. Key Points: The strong atmospheric shortwave absorption by black carbon suppresses precipitationRapid adjustments decrease the direct radiative effect of black carbon in two independent modelsEven though the underlying processes are strikingly similar in the models, the resulting change in precipitation by black carbon differs [ABSTRACT FROM AUTHOR]

Mesopelagic fish and squid occupy ocean depths extending below the photic zone and their vertical migrations represent a massive pathway moving energy and carbon through the water column. Their spatio-temporal distribution is however, difficult to map across remote regions particularly the vast Southern Ocean. This represents a key gap in understanding biogeochemical processes, marine ecosystem structure, and how changing ocean conditions will affect marine predators, which depend upon mesopelagic prey. We infer mesopelagic prey vertical distribution and relative abundance in the Indian sector of the Southern Ocean (20° to 130°E) with a novel approach using predator-derived indices. Fourteen years of southern elephant seal tracking and dive data, from the open ocean between the Antarctic Polar Front and the southern Antarctic Circumpolar Current front, clearly show that the vertical distribution of mesopelagic prey is influenced by the physical hydrographic processes that structure their habitat. Mesopelagic prey have a more restricted vertical migration and higher relative abundance closer to the surface where Circumpolar Deep Water rises to shallower depths. Combining these observations with a future projection of Southern Ocean conditions we show that changes in the coupling of surface and deep waters will potentially redistribute mesopelagic prey. These changes are small overall, but show important spatial variability: prey will increase in relative abundance to the east of the Kerguelen Plateau but decrease to the west. The consequences for deep-diving specialists such as elephant seals and whales over this time scale will likely be minor, but the changes in mesoscale vertical energy flow have implications for predators that forage within the mesopelagic zone as well as the broader pelagic ecosystem. [ABSTRACT FROM AUTHOR]

Abstract In past decades, China has experienced substantial economic growth and industrialization. However, the effects of vast development of China on Hg input to the nearby oceans are still unclear. In this study, four representative 210Pb-dated sediment cores were collected in the central and southern part of Bohai sea to investigate vertical changes of Hg contents and explore the relationship between the Hg deposition and pollution history in this region utilizing a large amount of information available. The results indicated that Hg median concentrations of sediment core B62, B66, JQ17 and HZ24 were 0.043 mg/kg, 0.054 mg/kg, 0.033 mg/kg and 0.018 mg/kg respectively, among which, B66 in Yellow river estuary and B62 in central part of Bohai Sea had higher concentrations and HZ24 in Bohai Strait had a lower concentration. 210Pb profile appeared as a three segments model in the core B62, but as many steps of decay with depth in B66. For HZ24, 210Pb activity only fluctuated with depth without any discernible trend. Sedimentary rates of these cores decreased as follows: B66＞B62＞JQ17＞HZ24. Vertical distributions of Hg concentrations in sediment cores were totally different from each other. Hg concentrations in sediment core B62 experienced an initial fluctuation followed by a decreasing trend, while sediment core HZ24 almost showed the uniform decreasing trends from the surface to the bottom. There were three segments of variation in sediment cores JQ17: initial fluctuation followed by an obviously decreasing tendency and then a converted variation from surface to bottom. Hg contents changes in core B62 might reflect the additive effects from atmospheric deposition at a larger scale and the river-delivered sediment accumulation, while Hg vertical changes in B66 mainly had a close relationship with the input of Yellow river. The converted variation at the bottom section in sediment cores JQ17 was inferred to have some relationship with the Chengbei platform construction in the corresponding periods. Highlights • Hg median content in each sediment core was 0.043, 0.054, 0.033 and 0.018 mg/kg. • Hg vertical distribution in B66 had relationships with input of Yellow river. • Hg change in B62 reflected additive effect of atmospheric deposition ＆river input. • Hg profile showed uniform rising trends in HZ24 from bottom to surface. • Inversion of Hg distribution in Q17 was related with platform construction. [ABSTRACT FROM AUTHOR]

Abstract Black-odor phenomenon in highly urbanized river is increasingly recognized as a global ecological risk. Biotransformation associated with sulfur cycle is a major contributor to the blank-odor phenomenon. The vertical geochemical gradient in black-odor rivers is likely to alter microbial community assemblages and functions in the sulfur cycle. However, the interactions between geochemical gradients and microbial communities, as well as the changes in the process of sulfur biotransformation under different environmental conditions remain largely unknown. The vertical community assembly patterns and the impacts of microbial communities and genes on the biotransformation in the sulfur cycle were revealed in our study for the first time in a typical urban black-odor river, Jinchuan River, in China. Vertical beta-diversity patterns of microbial communities mainly resulted from species replacement that was largely driven by spatial turnover (β SIM = 0.43) but also influenced by nestedness (β NES = 0.08). MiSeq sequencing and GeoChip 5.0 microarray chip approaches were applied and identify 41 bacterial genera, 8 archaeal genera, and 26 genes involved in the sulfur cycle in Jinchuan River. The vertical beta-diversity patterns of microbial profile mainly resulted from species replacement. Those sulfur-related bacterial and archaeal genera, accounting for 23.15% and 42.65% of the total bacteria and archaea respectively in analysed samples, were mainly responsible for sulfur reduction. According to redundancy analysis, oxidation-reduction potential (r = −0.8662, P < 0.05), S2− concentration (r = −0.6288, P < 0.05), and total nitrogen concentration (r = −0.6782, P < 0.05) were identified as factors that significantly affect sulfur-related microbial communities. The highest reaction potential was detected in the dissimilated sulfate reduction action and experienced an increase with depth increasing in the river system. The results indicated that the sulfur biotransformation in a deeper layer in river sediment could make more contribution to the black-odor phenomenon in urban rivers. Graphical abstract Image 1 Highlights • Vertical structured microbial communities in an urban river were detected. • Functions of microbial community on sulfur biotransformation were detected. • Remarkable micro-scale differentiations were found in different depths of rivers. • Vertical microbial beta-diversity patterns were largely driven by spatial turnover. • Sulfur biotransformation in deeper sediment contributes more to river pollution. [ABSTRACT FROM AUTHOR]

Abstract The ability to emigrate from estuarine nursery areas to spawning grounds is essential for the persistence of estuarine dependent species such as Red Drum, (Sciaenops ocellatus). Typically in this region, tidal inlets are the only mechanism for this transfer. Cedar Bayou, a natural tidal inlet, was deliberately closed in 1979 but was recently dredged and reopened. The inlet allows for direct water exchange between the Gulf of Mexico and Mesquite Bay, Texas, USA, and represents a unique opportunity to study estuarine dependent species' migration processes. Adult Red Drum were implanted with acoustic transmitters that allowed us to track their movement patterns before and after the reopening of Cedar Bayou. The goals of this study were to: 1) determine if Red Drum choose migration routes opportunistically in Texas waters; and 2) elucidate general movement patterns and residency estimates for Red Drum in Texas bays. Red Drum showed relatively little movement during the pre-opening period and summer, even after the inlet was restored. Once open, fish actively traversed through Cedar Bayou during the months commonly associated with spawning migrations and coincident with a drop in water temperature. These results demonstrate that Red Drum choose migration corridors opportunistically, thus opening tidal inlets such as Cedar Bayou can provide maturing Red Drum with greater connectivity between estuaries and spawning grounds in the open Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Foraminifera are numerically abundant components of the benthic fauna; thus, they are very important compounds in glaciomarine environments. However, ongoing oceanographic changes may influence their distribution, abundances and diversity differently at different times of the year. In the present study, we aimed to assess seasonal environmental changes in an Arctic fjord (Adventfjorden, W Spitsbergen) and the structure and distribution of benthic foraminiferal assemblages during four seasons (January, May, August, November). The study revealed that the benthic foraminiferal assemblages in Adventfjorden are susceptible to environmental changes related to enhanced inflow of shelf-transformed water (STW). We distinguished three zones in the fjord: (1) the deeper outer part influenced by STW, with living specimens staying in the few uppermost layers of sediment, (2) the shallower interior influenced by freshwater outflows and high sediment load, resulting in the dominance of opportunistic glaciomarine taxa constantly buried in the sediment, and (3) the central part, where the seasonal variation in the foraminifera assemblage reflects the interplay between the influence of riverine inputs and STW. Our study also revealed that the presence of STW in Adventfjorden favours an early spring appearance of juvenile foraminifera; however, the majority of the specimens are later withered and do not contribute to the summer pool of mature individuals. On the other hand, the majority of the mature specimens can survive during the winter because of sufficient organic matter stocks and year-long ice-free conditions. [ABSTRACT FROM AUTHOR]

Diurnal vertical migration (DVM) is a widespread phenomenon in the upper ocean, but it remains unclear to what degree it also involves passively transported micro- and meso-zooplankton. These organisms are difficult to monitor by in situ sensing and observations from discrete samples are often inconclusive. Prime examples of such ambiguity are planktonic foraminifera, where contradictory evidence for DVM continues to cast doubt on the stability of species vertical habitats, which introduces uncertainties in geochemical proxy interpretation. To provide a robust answer, we carried out highly replicated randomized sampling with 41 vertically resolved plankton net hauls taken within 26 hours in a confined area of 400 km2 in the tropical North Atlantic, where DVM in larger plankton occurs. Manual enumeration of planktonic foraminifera cell density consistently reveals the highest total cell concentrations in the surface mixed layer (top 50 m) and analysis of cell density in seven individual species representing different shell sizes, life strategies and presumed depth habitats reveals consistent vertical habitats not changing over the 26 hours sampling period. These observations robustly reject the existence of DVM in planktonic foraminifera in a setting where DVM occurs in other organisms. [ABSTRACT FROM AUTHOR]

It is broadly assumed that organisms inhabiting seasonally hypoxic estuaries and fjords are stressed by low dissolved oxygen (DO) conditions. However, relatively few zooplankton have shown clear avoidance of hypoxic water except when oxygen was extremely low. We investigated vertical distributions and abundance of the euphausiid Euphausia pacifica in the seasonally hypoxic Hood Canal, Washington using depth-stratified zooplankton net tows and CTD casts, monthly from June to October in 2012 and 2013 at two sites that contrasted in oxygen conditions. We separated E. pacifica into five life stages based on their ontogenetic development and swimming ability and related their density (#/m3) within each depth layer to the corresponding environmental variables using delta Generalized Linear Mixed Models (GLMMs). The models detected strong seasonal and spatial differences with no additional significant effects of DO or temperature. GLMMs showed that whole water-column abundances of calyptopes and furcilia I–III stages were more strongly related to DO and temperature than other stages. Overall, only modest effects of DO were observed, possibly because of the low temperatures and moderate DO levels compared to recent years. Combined laboratory experiments and multi-year mooring data show that conditions in other years could have resulted in direct mortality. [ABSTRACT FROM AUTHOR]

Euphausiids migrate vertically in the water column as part of their diel cycle. These migrations make them a key element in the biological pump of the pelagic environment. In order to evaluate the vertical distribution of euphausiids around Malpelo Island (3.8 - 4.2 N & 81.4 - 81.8 W), we took stratified zooplankton samples (0-50, 50-100, and 100-150 m) during the Pacífico-ERFEN campaign in September 2012. A total of 10 species belonging to four genera were identified. Euphausia diomedeae was the most abundant species in the 0-50 and 100-150 m layers, whereas E. distinguenda was the most abundant species in the 50-100 m layer. Based on quasi-Poisson generalized linear distribution models we found that abundance in the 50-100 m layer was significantly higher than in the 100-150 m layer (t= 3.05, p < 0.05). There were no significant differences associated with sampling hour (diurnal/nocturnal) (t= 0.07, p = 0.94). We calculated a vertical distribution index (VDI) based on abundance, showed that euphausiid species were concentrated in the 50-100 m layer during day and night. Calyptopis larvae dominated in abundance at all depth layers, followed by furcilia larvae, juveniles, and adults. The abundance of the latter increased gradually from the most superficial layer to the deepest layer, whereas juveniles showed the opposite pattern. This is the first study to describe the taxonomic composition, and vertical and spatial distribution of euphausiids associated with Malpelo Island, Colombian Pacific. [ABSTRACT FROM AUTHOR]

Prey and predators continuously react to each other and to their environment, adjusting their behavior to maximize their fitness. In a pelagic environment, organisms can optimize their fitness by performing diel vertical migrations. We applied a game-theoretic approach to investigate the emergent patterns of optimal habitat selection strategies in a multiple-habitat arena. Our setup allows both players to choose their position at day and at night in the water column. The model reproduces features of vertical migrations observed in nature, including residency at depth or at the surface, vertical migrations, mixed strategies, and bimodal distributions within a population. The mixed strategies appear as a consequence of frequency-dependent processes and not of any intraspecies difference between individuals. The model also reveals a curious feature where natural selection on individuals can provoke distinct regime shifts and precipitate an irreversible collapse in fitness. In the case presented here, the increasing voracity of the predator triggers a behavioral shift in the prey, reducing the fitness of all members of the predator population. [ABSTRACT FROM AUTHOR]

The deep scattering layer is an ubiquitous aggregation of zooplankton and forage fish in the ocean. It features the striking phenomenon of diel vertical migration, where animals remain in deep, dark water in daylight hours and migrate upwards at dusk. The common explanation for this is that prey avoid vulnerability to visual predators. Here, we develop a game-theoretic explanation for the deep scattering layer and its diel vertical migrations, focusing on one generic predator species and one generic prey species. The model is formulated in continuous time and space, and by neglecting the cost of locomotion, it allows fine-grained predictions of vertical distributions. The Nash equilibrium features a distinct deep scattering layer which undertakes diel vertical migrations, the range of which increases with predator abundance. Maximum feeding rates are predicted to occur at dawn and dusk. Predator interference emerges from the game dynamics in the form of a complicated functional dependency of gross encounter rates on predator abundance. In turn, the growth rate of the prey decreases monotonically with predator abundance. In addition to providing a mechanistic explanation for the striking phenomenon of diel vertical migrations, the model yields quantitative predictions of vertical distributions and diel patterns in feeding intake, which may be compared with acoustic data, observed individual behavior, or stomach data. [ABSTRACT FROM AUTHOR]

The studied succession (Lower Miocene-Early Middle Miocene) In central Iraq is distinguished by a wide range of fossils, mostly benthic foraminifera, and other fossils including bivalves, gastropods, echinoids fragments, red algae and coral are also presented. Index fossils of benthic foraminifera have been used for the purpose of determining the age of the Euphrates and Jeribe formations, because of their young age, wide geographical distribution and abundance in the selected wells. The present study involves four selected wells of Ajil oil field and in terms of the biostratigraphy of the Euphrates, Dhiban, and Jeribe formations depending on benthic foraminifera and other associated fossils. Some of these fossils have a short vertical distribution, while others have long vertical distribution. There are two biozones determined. First, in Euphrates Formation "Ammonia beccarii-Miogypsina globulina" (Assemlage zone) Second in Jeribe Formation "Borelis melo curdica" (range zone). Dhiban Formation include only small pieces of distorted fossils and dominated by anhydrite, therefore it lacks the biostratigraphic zonation. [ABSTRACT FROM AUTHOR]

It is well known that alkaline amendments could effectively decrease the bioavailability of heavy metals in soils. However, the vertical distribution of heavy metals and the nutrients enriching in amendments are little concerned during long-term field remediation. Thus, the objective of the present study was to investigate the vertical distribution and availability of Cu, Cd, Ca, and P after a 7-year field experiment. In this study, a single application of lime and apatite was conducted with the rates of 1.71-6.84 and 6.84-19.8 tons/ha, respectively. Soil pH and immobilization efficiency of Cu and Cd were both increased with increasing dosages of lime and apatite (0-50 cm). Applications of lime and apatite decreased the mobility of Cu and Cd although soil Cu and Cd in the surface soil were increased due to the input by atmospheric dry and wet deposition. Moreover, concentrations of Cu and Cd in lime- and apatite-amended soils (0-13 cm) were higher than those in the control group. However, applications of lime and apatite decreased the downward eluviations of heavy metals in soils (13-50 cm). For soil nutrients, the Ca concentrations at 0-13 and 13-30 cm were both enhanced with increasing amendment dosages, while only soil P concentration at 0-13 cm was increased in apatite-treated soils and majority of them presented in stable-P. In addition, resin-P was increased with increasing dosages of the apatite, which suggested that high eutrophication risk was induced by excessive P loss. Thus, more attention should be paid to the nutrients (phosphorus) and pollutants enriching in the amendments during in-situ remediation of heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Columnar sediment samples were collected from five representative river inflow areas of Dianchi Lake, China. The vertical distribution of each form of P were tested. Results showed that the concentration of TP in the sediments from areas A, B, C, D and E in the order of D > B > A > C > E, and the average concentration of D, B, A, C and E were 2991, 2064, 1308, 879, and 759 mg•kg−1, respectively. The concentration of Ex-P, Fe/Al-P, Ca-P and Org-P all decreased with increasing depth. The release of Ex-P was significantly related to TP whereas the Fe/Al-P was not significantly related to TP in the samples from areas polluted by domestic sewage. However, the release of Ex-P and Fe/Al-P were both significantly related to TP in the samples from areas polluted by phosphate mining and phosphate fertilizer application. The results of equilibrium P concentration (EPC0) analysis showed that P in the sediments of areas A, D and E were the source of P in Dianchi Lake, and the P in the sediments of areas B and C were in relative equilibrium with the overlying water. [ABSTRACT FROM AUTHOR]

Diel vertical migration (DVM) is a common behaviour and often relates with the diurnal feeding periodicity. Nonetheless, sprat feeding behaviour and daily ration (DR) estimation are usually based on daytime stomach contents from deeper layers. Our study provides a new approach for DR estimation, taking into consideration the DVM associated feeding periodicity. We analysed sprat DVM by hydroacoustics and collected stomach contents in the Central Baltic Sea at different depths. The main outcome is that feeding in the deep during the day represents only 16–39% of the DR. DRs were 1.4-times higher using our approach compared to the established approach. The underestimation by the established approach was mainly caused by ignoring the effect of higher temperatures from the upper layers on the gastric evacuation rate. Our results have major implications not only for DR estimates but also on the interpretation of prey selectivity. The study emphasizes the importance of adapting the sampling design to the vertical feeding dynamics to avoid a biased picture of predator prey interactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • P. akamusi and its effect on bioassessment were examined. • P. akamusi larvae present seasonally substantial vertical migration in the sediments. • Bioassessment based on grab samples may seriously overrate the water quality status. • Vertical migration of macroinvertebrates should be considered in developing bioassessment. Abstract Propsilocerus akamusi (Diptera: Chironomidae) is a dominant species in numerous eutrophic lakes and they could burrow into deep sediments (>30 cm) during summer months. However, common-used grab samplers are efficient in collecting surface-dwelling species (<20 cm), thus vertical migrations of dominant species may interfere bioassessment. Here, we monthly investigated the vertical sediment positioning of P. akamusi larvae and its influence on bioassessment. Our results indicated that, from late-April to October, most individuals aestivated at the sediment below 30 cm depth which maybe an adaptation to the thermal stress. As to other periods, the larvae were generally found in the depth of 10–30 cm. Moreover, Peterson grab samples collected only 0% and 12.6% of total P. akamusi individuals in summer and late-autumn, respectively, resulting in serious underestimation of the actual pollution status. This implied that vertical movements of dominant macroinvertebrates should be taken into account when designing of bioassessment protocols. For P. akamusi , Core-sampling for calibration were strongly encouraged, and the low-temperature period for Grab-sampling is also proposed. [ABSTRACT FROM AUTHOR]

Increasing industrial metal demands due to rapid technological developments may drive the prospection and exploration of deep-sea mineral resources such as polymetallic nodules. To date, the potential environmental consequences of mining operations in the remote deep sea are poorly known. Experimental studies are scarce, especially with regard to the effect of sediment and nodule debris depositions as a consequence of seabed mining. To elucidate the potential effects of the deposition of crushed polymetallic nodule particles on abyssal meiobenthos communities, a short (11 days) in situ experiment at the Peru Basin in the South East Pacific Ocean was conducted. We covered abyssal, soft sediment with approx. 2 cm of crushed nodule particles and sampled the sediment after eleven days of incubation at 4200 m water depth. Short-term ecological effects on the meiobenthos community were studied including changes in their composition and vertical distribution in the sediment as well as nematode genus composition. Additionally, copper burden in a few similar-sized, but randomly selected nematodes was measured by means ofμ-X-ray fluorescence. At the end of the experiment, 46 ± 1% of the total meiobenthos occurred in the added crushed nodule layer while abundances decreased in the underlying 2 cm compared to the same depth-interval in original, undisturbed sediments. Densities and community composition in the deeper 2-5 cm layers remained similar in covered and undisturbed sediments. The migratory response into the added substrate was particularly seen in polychaetes (73 ± 14%, relative abundance across all depth layers) copepods (71 ± 6%), nauplii (61 ± 9%) and nematodes (43 ± 1%). While the dominant nematode genera in the added substrate did not differ from those in underlying layers or the undisturbed sediments, feeding type proportions in this layer were altered with a 9% decrease of non-selective deposit feeders and an 8% increase in epistrate feeders. Nematode tissue copper burden did not show elevated copper toxicity resulting from burial with crushed nodule particles. The results indicate that short-term substrate burial requires special attention with regard to ecological consequences of mineral extraction in the deep-sea. [ABSTRACT FROM AUTHOR]

The stocking of juvenile eels and trap and transport programs of large yellow (American) eels (Anguilla rostrata) were initiated in Ontario to mitigate mortalities observed at hydroelectric dams and to increase escapement from the upper St. Lawrence River and Lake Ontario (Canada). A total of 380 migrating female silver eels (stocked, trapped and transported, and wild) were tagged with acoustic transmitters between 2011 and 2014. Their migration and escapement at the exit of the Gulf of St. Lawrence, the Cabot Strait, were recorded using acoustic receivers. Escapement rates varied between 8.9% and 20.0% annually (mean = 11.4%). A high proportion of stocked eels were detected (N = 27 of 43 detected at Cabot Strait), demonstrating their ability to escape the Gulf. No differences in migration speed or crossing locations at Cabot Strait were found among the three categories. Eels crossing Cabot Strait did not display diel and tidal patterns, but their estimated swimming depth indicated diel vertical migrations. The low escapement rates observed may be related to predation events and (or) the low and variable detection efficiency of the acoustic receivers' line. [ABSTRACT FROM AUTHOR]

Diel vertical migration (DVM) behaviour in swarms of Antarctic krill (Euphausia superba Dana, 1850) is notoriously variable, with swarms being found at a range of depths and in different shapes, sizes, and packing concentrations throughout the day-night cycle. Because social aggregation can potentially serve the same purpose as DVM in minimising predation risk, krill may use both strategies to varying extents. Diel variation was examined in swarm depth, length, perimeter, area, thickness, and packing concentration across 4,130 open-ocean swarms in the Scotia Sea during summer. Inter-relationships between each of the swarm descriptors were complex but multivariate analyses identified pairings in levels of similarity between area and perimeter, thickness and packing concentration, and depth and length. Second-stage analysis further identified diel cyclicity in these relationships. Swarm parameters were more variable than depth over the diel cycle, identifying swarming to be the primary diel response to which DVM is a secondary contributor. [ABSTRACT FROM AUTHOR]

Two dominant krill species Meganyctiphanes norvegica (Sars, 1857) and Thysanoessa raschii (Sars, 1864) coexist in the subarctic waters of lower St. Lawrence Estuary, Canada. Both species perform diel vertical migrations representing often large displacements of ~100–150 m through several temperature regimes. We studied the impact of temperature, a fundamental factor controlling the metabolism of ectothermic species, on the metabolic rate and swimming activity of the two species. Annular respirometers were used to quantify simultaneously oxygen consumption (Ṁ O2g–1wet mass) and the spontaneous swimming activity of individual krill over a period of 24 h at six temperatures, by intermittent-flow respirometry. Both species significantly increased their low routine and maximal metabolic rates from 0 °C to 15 °C, suggesting high thermal plasticity. The spontaneous swimming activity of M. norvegica was reduced to almost zero at 0 °C, whereas T. raschii swam 1.0 cm s–1at this temperature. Based on swimming performance, M. norvegica might avoid the cold intermediate layer (CIL, < 1 °C) in the estuary, which coincides with actual daytime distribution below the CIL in the warmer deep-water layer. Despite the rare occurrence of 15 °C in the estuary, both species still showed high metabolic and swimming performance at that temperature. High and differential thermal plasticity of both krill species might have important ecological consequences for their distribution patterns in their natural environment, as energy requirements differ in the two species. [ABSTRACT FROM AUTHOR]

Highlights • Good agreement between meso-zooplankton DVM and ADCP backscattering strength (Sv). • Zooplankton migration is highly conditioned by environmental conditions. • MLD, NPP and light (solar and lunar) influence vertical position of zooplankton. • Sv and ADCP vertical velocity highlight different types/ranges of DVM. • DVM is not mandatory behaviour but depends on food availability in deeper layers. Abstract From the eleven-year data record at the Southern Adriatic Observatory (E2M3A), we study for the first time in the Adriatic Sea the strength of the backscatter signal from an Acoustic Doppler Current Profiler (ADCP) in relation to zooplankton vertical movement. The signal represents well the general behaviour of the zooplankton to sink at dawn and to emerge at the sunset. The modulation of the signal along the year is linked in particular to the different environmental conditions and the presence of different zooplankton groups. The correlation between the backscatter signal and distinct zooplankton groups (copepods, euphausiids, ostracods, appendicularians, salps) shows that in different seasons and environmental conditions, different groups are responsible for the strength of the signal. Furthermore, the backscatter signal, interpreted in terms of the qualitative composition of the zooplankton community, provides important information on the behaviour and habits of zooplankton in the southern Adriatic. Poorly known aspects of zooplankton behaviour are described in more detail, such as: recovery of zooplankton vertical distribution after mixing events, vertical migration in conditions of increased food availability at depth due to vertical mixing, modulation of vertical migration in dependence of the lunar phase and vertical migration in relation to deep chlorophyll maximum position. In addition, the present study emphasizes the possible influence of gelatinous zooplankton at the open sea on high backscatter values during the warmer part of the year. [ABSTRACT FROM AUTHOR]

Li, C.; Fu, X.; Xiao, Q.; Pan, X., and Cao, H., 2018. Vertical distribution of sediment concentration in offshore waters. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 167–171. Coconut Creek (Florida), ISSN 0749-0208. The existing formulae of vertical distribution of sand concentration are difficult to integrate. Based on the formula of vertical distribution of the flow velocity obtained in the previous study and the suspended sediment diffusion equation in equilibrium, a formula of the distribution of suspended sediment is deduced. It can effectively avoid the phenomena that the Rouse formula equals zero at the water surface. The field measurement data of Jiangsu Sea is used to verify and analyze the deuced formula. And results show that it has a high accuracy and it solve the difficulties caused by lack of data in engineering, such as only the sediment concentration on the surface is given. [ABSTRACT FROM AUTHOR]

The Korea-United States Air Quality Study (KORUS-AQ) conducted during May-June 2016 offered the first opportunity to evaluate direct-sun observations of formaldehyde (HCHO) total column densities with improved Pandora spectrometer instruments. The measurements highlighted in this work were conducted both in the Seoul megacity area at the Olympic Park site (37.5232°N, 27.1260°E; 26ma.s.l.) and at a nearby rural site downwind of the city at the Mount Taehwa research forest site (37.3123°N, 127.3106°E; 160ma.s.l.). Evaluation of these measurements was made possible by concurrent ground-based in situ observations of HCHO at both sites as well as overflight by the NASA DC-8 research aircraft. The flights provided in situ measurements of HCHO to characterize its vertical distribution in the lower troposphere (0-5 km). Diurnal variation in HCHO total column densities followed the same pattern at both sites, with the minimum daily values typically observed between 6:00 and 7:00 local time, gradually increasing to a maximum between 13:00 and 17:00 before decreasing into the evening. Pandora vertical column densities were compared with those derived from the DC-8 HCHO in situ measured profiles augmented with in situ surface concentrations below the lowest altitude of the DC-8 in proximity to the ground sites. A comparison between 49 column densities measured by Pandora vs. aircraft-integrated in situ data showed that Pandora values were larger by 16% with a constant offset of 0.22DU (Dobson units; R²=0:68). Pandora HCHO columns were also compared with columns calculated from the surface in situ measurements over Olympic Park by assuming a wellmixed lower atmosphere up to a ceilometer-measured mixedlayer height (MLH) and various assumptions about the small residual HCHO amounts in the free troposphere up to the tropopause. The best comparison (slope=1:03±0:03; intercept=0:29±0:02 DU; and R²=0:78±0:02) was achieved assuming equal mixing within ceilometer-measured MLH combined with an exponential profile shape. These results suggest that diurnal changes in HCHO surface concentra-tions can be reasonably estimated from the Pandora total column and information on the mixed-layer height. More work is needed to understand the bias in the intercept and the slope relative to columns derived from the in situ aircraft and surface measurements. [ABSTRACT FROM AUTHOR]

Air pollution has become one of the most stubborn environmental problem in China, the traditional environmental monitoring mainly focus on the horizontal distribution of the pollutants, while it is still of great importance to have the knowledge of the vertical profiles of them. The present study, for the first time, attempted to acquire the vertical distributions of O 3 and one of its precursors, volatile organic compounds (VOCs) within 1000 m of lower troposphere by using a tethered balloon in the suburban of Shanghai, a Chinese megacity. We analyze the concentration and the ozone formation potential (OFP) at three height level of 50–350, 350–700, and 700–1000 m. According to our measurement, the total concentration of VOC decreased with the altitude increasing. In addition, the dominant species of OFP was alkene, aromatics, and alkene at height level of 50–350, 350–700 and 700–1000 m, respectively. Our results suggest that, in the morning, the fresh emission contributed a lot to the high concentration of benzene and toluene near ground. Furthermore, the regression analyzes showed toluene decreased faster than benzene in the troposphere. The VOC concentration can be used as initial values for numerical simulations of chemical reaction in the lower troposphere. [ABSTRACT FROM AUTHOR]

1. It has been widely recognized that species show extensive variation in form and function. Based on species' attributes, they can be positioned along major axes of variation, which are often defined by life-history traits, such as number of offspring, age at maturity or generation time. Less emphasis has been given in this respect to tolerance traits, especially to resistance to abiotic stress conditions, which often determine community (dis)assembly and distribution. 2. Soil fauna species distribution is governed to a large extent by environmental conditions that filter communities according to functional traits, such as abiotic stress tolerance, morphology and body size. Trait-based approaches have been successfully used to predict soil biota responses to abiotic stress. It remains unclear, though, how these traits relate to life-history traits that determine individual performance, that is, reproduction and survival. 3. Here, we analyse patterns in multidimensional trait distribution of dominant groups of soil fauna, that is, Isopoda, Gastropoda and Collembola, known to be important to the functioning of ecosystems. We compiled trait information from existing literature, trait databases and supplementary measurements. We looked for common patterns in major axes of trait variation and tested if vertical distribution of species in the soil explained trait variation based on three components of trait diversity (trait richness, evenness and divergence). 4. Our results showed that two to three axes of variation structured the trait space of life-history and tolerance traits in each of the taxonomic groups and that vertical distribution in soil explained the main axis of trait variation. We also found evidence of environmental filtering on soil fauna along the vertical soil distribution, with lower trait richness and trait divergence in soil-dwelling than in surface-living species. 5. Our study was partially limited by the lack of detailed trait measurements for the selected taxonomic groups. In this regard, there is an urgent need for standardized trait databases across invertebrate groups to improve trait-based diversity analysis and fill gaps in the mechanistic understanding behind trait distribution, trait filtering and the link with species fitness and performance. [ABSTRACT FROM AUTHOR]

It is important to determine the vertical distributions of soil total nitrogen (STN) and soil total phosphorus (STP) as well as the factors that influence them in the Earth's critical zone (CZ) in order to understand the N/P cycle in the CZ. However, few data are available regarding the vertical distributions of STN and STP in deep soil profiles in the CZ. Thus, this study investigated the vertical distributions of the STN and STP as well as related factors in a deep soil profile on the Loess Plateau, China. Soil drilling was used to collect 703 soil samples throughout the soil profile from five sites. The STN decreased initially at all of the sampling sites (except at Shenmu), before fluctuating with increasing depth throughout the profile, whereas the STP exhibited a fluctuating trend at all sites. The mean STN and STP concentrations ranged from 0.12 g kg −1 to 0.25 g kg −1 and from 0.45 g kg −1 to 0.58 g kg −1 , respectively. The adjusted r 2 values based on stepwise multiple linear regressions for STN and STP ranged from 35% to 83% and from 4% to 17%, respectively, and thus, STN was explained better by the measured soil variables compared with STP. The mean STN and STP stocks ranged from 1.87 to 3.90 mg ha −1 and from 6.75 to 9.09 mg ha −1 , respectively. The results of this study facilitate evaluations of STN and STP stocks and studies of the N/P cycle in the CZ on the Loess Plateau. [ABSTRACT FROM AUTHOR]

This study examines the occurrence of vascular epiphytic species in Central Amazonian black-water floodplain forests (igapó) and considers whether their horizontal and vertical distribution is influenced by the flood pulse, as is the case with tree species (phorophytes). Research was conducted in sixteen forest plots the Jaú National Park. In these, epiphytes on all phorophytes with DBH ≥ 10 cm were identified. We measured flood height using the watermark left by the last high-water period, then estimated the height relative to the ground of every epiphytic individual. We recorded 653 individuals in 37 species, distributed on 109 phorophytes. Igapó floodplain forests have much lower richness and abundance of vascular epiphyte species than do other Amazonian forests. This may reflect the limitation of available sites for colonization (only 24.9% of studied trees were occupied by epiphytes). Holoepiphytes predominated, and the combined presence of a flood-pulse, linked to the nutrient-poor soil poor seems to limit the occurrence of nomadic vines. Horizontal distribution of epiphytes followed the distribution of phorophytes, which in turn followed the flood-level gradient. Also flooding interacted strongly with vertical zonation to determine species richness. As already well-reported for trees, and unlike reports of epiphytes in other floodplains, flooding strongly influenced richness and distribution of vascular epiphytes in the studied igapó forests. [ABSTRACT FROM AUTHOR]

Lakes and reservoirs worldwide are increasingly experiencing depletion of dissolved oxygen (anoxia) in their bottom waters (the hypolimnion) because of climate change and eutrophication, which is altering the dynamics of many freshwater ecological communities. Hypolimnetic anoxia may substantially alter the daily migration and distribution of zooplankton, the dominant grazers of phytoplankton in aquatic food webs. In waterbodies with oxic hypolimnia, zooplankton exhibit diel vertical migration (DVM), in which they migrate to the dark hypolimnion during the day to escape fish predation or ultraviolet (UV) radiation damage in the well-lit surface waters (the epilimnion). However, due to the physiologically stressful conditions of anoxic hypolimnia, we hypothesized that zooplankton may be forced to remain in the epilimnion during daylight, trading oxic stress for increased predation risk or UV radiation damage. To examine how anoxia impacts zooplankton vertical migration, distribution, biomass, and community composition over day-night periods, we conducted multiple diel sampling campaigns on reservoirs that spanned oxic, hypoxic, and anoxic hypolimnetic conditions. In addition, we sampled the same reservoirs fortnightly during the daytime to examine the vertical position of zooplankton throughout the summer stratified season. Under anoxic conditions, most zooplankton taxa were predominantly found in the epilimnion during the day and night, did not exhibit DVM, and had lower seasonal biomass than in reservoirs with oxic hypolimnia. Only the phantom midge larva, Chaoborus spp., was consistently anoxia-tolerant. Consequently, our results suggest that hypolimnetic anoxia may alter zooplankton migration, biomass, and behavior, which may in turn exacerbate water quality degradation due to the critical role zooplankton play in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Benthic diatoms are dominant primary producers in intertidal marine sediments, which are characterized by widely fluctuating and often extreme light conditions. To cope with sudden increases in light intensity, benthic diatoms display both behavioural and physiological photoprotection mechanisms. Behavioural photoprotection is restricted to raphid pennate diatoms, which possess a raphe system that enables motility and hence positioning in sediment light gradients (e.g. via vertical migration into the sediment). The main physiological photoprotection mechanism is to dissipate excess light energy as heat, measured as Non-Photochemical Quenching (NPQ) of chlorophyll fluorescence. A trade-off between vertical migration and physiological photoprotection (NPQ) in benthic diatoms has been hypothesized before, but this has never been formally tested. We exposed five epipelic diatom species (which move in between sediment particles) and four epipsammic diatom species (which live in close association with individual sand grains) to high light conditions, and characterized both NPQ and the relative magnitude of the migratory response to high light. Our results reveal the absence of a significant downward migratory response in an araphid diatom, but also in several raphid epipsammic diatoms, while all epipelic species showed a significant migratory response upon high light exposure. In all epipsammic species the upregulation of NPQ was rapid and pronounced; NPQ relaxation in low light conditions, however, occurred faster in the araphid diatom, compared with the raphid epipsammic species. In contrast, all epipelic species lacked a strong and flexible NPQ response and showed higher susceptibility to photodamage when not able to migrate. While overall our results support the vertical migration-NPQ trade-off, the lack of strong relationships between the capacity for vertical migration and NPQ within the epipsammic and epipelic groups suggests that other factors as well, such as cell size, substrate type and photoacclimation, may influence photoprotective strategies. [ABSTRACT FROM AUTHOR]

In deep-sea cold seeps, microbial communities are shaped by geochemical components in seepage solutions. In the present study, we report the composition of microbial communities and potential metabolic activities in the surface sediment of Jiaolong cold seep at the northern South China Sea. Pyrosequencing of 16S rRNA gene amplicons revealed that a majority of the microbial inhabitants of the surface layers (0-6 cm) were sulfur oxidizer bacteria Sulfurimonas and archaeal methane consumer ANME-1, while sulfate reducer bacteria SEEP-SRB1, ANME-1 and ANME-2 dominated the bottom layers (8-14 cm). The potential ecological roles of the microorganisms were further supported by the presence of functional genes for methane oxidation, sulfur oxidation, sulfur reduction and nitrate reduction in the metagenomes. Metagenomic analysis revealed a significant correlation between coverage of 16S rRNA gene of sulfur oxidizer bacteria, functional genes involved in sulfur oxidation and nitrate reduction in different layers, indicating that sulfur oxidizing may be coupled to nitrate reducing at the surface layers of Jiaolong seeping site. This is probably related to the sulfur oxidizers of Sulfurimonas and Sulfurovum, which may be the capacity of nitrate reduction or associated with unidentified syntrophic nitrate-reducing microbes in the surface of the cold seep. [ABSTRACT FROM AUTHOR]

Tides are an important forcing factor of macrotidal sandy beaches because they are directly responsible for the local morphodynamic conditions. Macrotidal beaches may harbor different microhabitats such as sandbars and runnels. We evaluated the influence of tides on the vertical distribution of meiofaunal organisms, particularly nematodes, in these two microhabitats at De Panne Beach, on the North Sea coast of Belgium. The 11 meiofaunal groups found were Acari, Amphipoda, Copepoda, Gastrotricha, Nematoda, Oligochaeta, Ostracoda, Polychaeta, Rotifera, Tardigrada and Turbellaria. The nematodes were identified to species level; the 147 species found included 112 in the sandbar and 117 in the runnel. Only turbellarians and nematodes migrated upward during low tide in the sandbar. The response of the nematodes was species-specific; during low tide, they migrated upward in the sandbar and downward toward deeper layers of the sediment in the runnel. These migration patterns were attributed to the feeding strategies in the sandbar (i.e. possible increase of diatom biomass in the surface layer due to high solar incidence), while environmental variables best explained the migration patterns in the runnel (i.e. preferred grain size and amount of total organic carbon). These results suggest a dissimilar vertical migration of the meiofauna over the tidal cycle in the two microhabitats. We attribute the vertical distribution of nematode species and some other meiofaunal groups to active migration toward preferred sites with more food or better environmental conditions. This study also indicated that other variables such as predation and competition, rather than the commonly studied physical variables should be included in future sampling designs of sandy-beach meiofauna assessments, since the environmental variables measured here could not fully explain the vertical distributions of the major meiofaunal groups or the community as a whole. [ABSTRACT FROM AUTHOR]

Vertical distributions of total and particulate 210Po and 210Pb activities in the water column were measured at eleven stations in the North Atlantic during the GEOTRACES GA01 GEOVIDE cruise in May–June 2014. Total 210Po activity was on average 24 % lower than 210Pb activity in the upper 100 m, and was closer to unity in the mesopelagic (100–1000 m). The partitioning coefficients (Kd) along the transect suggest the preferential association of 210Po relative to 210Pb onto particles. The prominent role of small particles in sorption was confirmed by the observation that over 80 % of the particulate radionuclide activity was on small particles. To account for the observed surface water 210Po / 210Pb disequilibria, particulate radionuclide activities and export of both small (1–53 μm) and large (> 53 μm) particles must be considered. A comparison between the GEOVIDE total particulate 210Po / 210Pb activity ratios (AR) and the ratios in previous studies revealed a distinct geographic distribution, with lower particulate AR in the high-latitude North Atlantic (including this study) and Arctic in relation to all other samples. For the samples where apparent oxygen utilization (AOU) was calculated at the same depth and time as the 210Po / 210Pb AR (40 stations including this study), there was a two-phase correlation between the total particulate AR and AOU demonstrating the competing forces of remineralization and radionuclide decay from particles as they age. [ABSTRACT FROM AUTHOR]

The present study investigates the impact of tropical cyclone (TC) Nilam on the vertical distribution of carbon monoxide (CO) over Chennai in southern India. Measurements of OZone and water vapour by Airbus In‐service airCraft (MOZAIC) profiles of CO measured during October–November 2012 were analysed. The vertical profiles of CO on 15 October and 2 November were influenced by convective motions with a significant decrease in outgoing long‐wave radiation (OLR) compared to that on normal days of observations. The near‐surface mixing ratios of CO (185 ± 24 ppbv) in convectively influenced conditions were much lower than those measured during normal days (>210 ppbv). The occurrence of minimum CO values at altitudes of 4–6 km coincided with the lowest lapse rate (LR) value of 4–5 °C/km. The uplift of surface air masses led to a large increase in the CO mixing ratio in the free troposphere. The differences in CO between the lower and free troposphere were relatively small (40–50 ppbv) and large (90–100 ppbv) during convective and normal days, respectively. In the lower troposphere, elevated values of CO (>250 ppbv) were measured for lighter wind speeds from the north, while lower values (<150 ppbv) were measured for strong winds from the western sectors. The Model for OZone And Related chemical Tracers (MOZART‐4) and Chemistry Climate Model 2 (CCM2) simulations did not capture the detailed features of the CO profiles. For cyclone‐influenced measurements in the lower troposphere, MOZART‐4 underestimated the CO values by approximately 13%, but CCM2 overestimated the CO values by 70%. In the upper troposphere, MOZART‐4 and CCM2 underestimated the observations by 6–8% and 12–22%, respectively. The mixing scheme of the model and simulated concentrations seem to be the key causes of disagreements. However, the performances of both the MOZART‐4 and CCM2 simulations were better for convection‐free normal days. [ABSTRACT FROM AUTHOR]