Upstream Control Research Articles

Gross pathology, physiological and toxicological responses in relation to metals and persistent organic pollutants (POPs) burden in tilapia species from Ogun River, Nigeria

We have investigated gross pathology, physiological (steroid precursors) and toxicological responses (oxidative stress and phase II biotransformation) in relation to tissue contaminant burden in Tilapia species along the entire length (320 km) of Ogun River, Nigeria. The Ogun River is the longest and largest river in Southwestern Nigeria located along heavily industrialized cities and receives complex mixtures of effluents. A total of 1074 tilapias were collected from three sampling points (Abeokuta, Isheri and Ikorodu) and from an upstream control point (Igboho) and evaluated for gross pathological changes, hepatic transcript levels for oxidative stress and phase II biotransformation responses. Trace metal concentrations and POPs in muscle samples were analyzed using ICP-MS and GC-MS respectively. Evaluation of gross pathological changes showed a 50-, 33-, 17 and 0% prevalence of hepatic tumors at the Ikorodu, Abeokuta, Isheri and Igboho sites, respectively. Plasma concentrations of cholesterol and pregnenolone showed apparent significant decreases at downstream sites of the control point in both male and female fish (except for pregnenolone levels of male fish at Ikorodu). Inversely, gst, ugt-1, ZuCu-sod and sod significantly increased in fish collected from downstream sites, compared with the control site and these increases paralleled the significant increase in trace metal and POPs concentrations at these sites. PCA revealed a site related association between measured toxicological responses and contaminant burden, indicating a potential cause-and-effect relationship. Thus, the possible adaptation of Ogun River Tilapia species to contaminants may have significant consequences on cellular, physiological and biochemical processes regulating metabolism, growth, development and reproduction, and also have serious human health consequences, since the Ogun River is used for fisheries and domestic water supply for surrounding neighborhoods.

Effects of wood addition on stream benthic invertebrates differed among seasons at both habitat and reach scales

Addition of large wood (LW, wood pieces longer than 1m and wider than 10cm) into stream channels is a common restoration practice aimed at enhancing habitat diversity and fish populations, as well as the abundance and diversity of benthic invertebrates. Nevertheless, there is some controversy regarding the effects of LW restoration on invertebrate assemblages, and the effects could differ depending on the season of the year as well as on the scale of observation (habitat vs reach scale). In this study we analysed the effects of a LW restoration experiment performed in 4 mountain streams following a BACI (Before-After/Control-Impact) design. We sampled benthic invertebrates in 3 main habitats (fine inorganic sediments, called gravel; coarse inorganic sediments, called cobbles; and particulate organic matter, called POM) in winter and summer before and after the addition of LW into experimental reaches, and compared the results to those obtained from upstream control reaches. LW addition promoted the retention of gravel and organic matter, resulting in an overall decrease in the areal cover of cobbles and a significant increase in the cover of organic matter in summer. Invertebrate richness was highest in cobbles and lowest in POM, whereas density and biomass were highest in POM and lowest in gravel. At the habitat scale, LW addition promoted invertebrate and shredder richness, diversity and biomass in summer, but the opposite effect was found in winter. Community composition changed significantly with wood addition, most notably as a result of increased density of elmids, limnephilids and limoniids, and decreased density of baetids. Density of limnephilids increased 20-fold and that of limoniids 5-fold. At the reach scale, LW addition enhanced the biomass of invertebrates and shredders in summer but the effects were opposite in winter. LW addition did not affect invertebrate density. The results show the effects of LW restoration on invertebrates to differ among seasons. Positive effects on biomass occur in summer, when retention by LW enhances food availability compared to unrestored reaches, whereas effects are slightly negative in winter, a period of large food availability.

Responses of skeletal muscle hypertrophy in Wistar rats to different resistance exercise models.

This study aimed to compare the effects of three different resistance exercise models on the quadriceps muscle cross-sectional area, as well as on mTOR phosphorylation and other pivotal molecules involved in the upstream regulation of mTOR. Twenty-four male Wistar rats were divided into untrained (control), endurance resistance training, strength resistance training, and hypertrophy resistance training (HRT) groups (n=6). After 12 weeks of training, the red portion of the quadriceps was removed for histological and Western blot analyses. The results showed that the quadriceps weight and cross-sectional areas in the exercised groups were higher than those of the untrained rats. However, the HRT group presented better results than the other two experimental groups. This same pattern was observed for mTOR phosphorylation and for the most pivotal molecules involved in the upstream control of mTOR (increase of PKB, 14-3-3, ERK, p38 MAPK, and 4E-BP1 phosphorylation, and reduction of tuberin, sestrin 2, REDD1, and phospho AMPK). In summary, our study showed that HRT leads to high levels of mTOR phosphorylation as well as of other proteins involved in the upstream regulation of mTOR.

Strategic Analysis of the Agency Model for Digital Goods

The introduction of digital goods in the media industry has gained a considerable amount of positive press due to superior features such as increased accessibility and portability. However, the distribution of these digital goods in conjunction with their physical analogs (i.e., printed books) has been operationally problematic for media supply chains. Specifically, the types of contracts utilized to distribute these goods such as agency models have come under fire in the press. A high profile case brought by the Department of Justice (DOJ) against Apple exemplifies this debate as the DOJ claims that the agency model utilized by Apple caused higher prices and decreased consumer surplus. We create and analyze a model of vertically differentiated goods to compare and contrast the agency model with the wholesale model. We ascertain that both (a) the revenue‐sharing structure and (b) the upstream publisher's control over the price contribute to the benefits of the agency model. We consider a variation of this model which shows that if the retailer utilizes a “fixed price” model, then he suffers from a short‐term loss in profit, possibly to garner additional market share. We also investigate an incentive alignment condition for the agency model which assures that the retailer and the publisher will together commit to selling digital goods alongside physical goods in the supply chain. Finally, we analyze an extension of the original model which incorporates horizontal differentiation in addition to vertical differentiation and shows that in most cases, the horizontal differentiation does not alter our original results that the agency model outperforms the wholesale model.

The RNA-binding protein Tristetraprolin (TTP) is a critical negative regulator of the NLRP3 inflammasome

The NLRP3 inflammasome is a central regulator of inflammation in many common diseases, including atherosclerosis and type 2 diabetes, driving the production of pro-inflammatory mediators such as IL-1β and IL-18. Due to its function as an inflammatory gatekeeper, expression and activation of NLRP3 need to be tightly regulated. In this study, we highlight novel post-transcriptional mechanisms that can modulate NLRP3 expression. We have identified the RNA-binding protein Tristetraprolin (TTP) as a negative regulator of NLRP3 in human macrophages. TTP targets AU-rich elements in the NLRP3 3'-untranslated region (UTR) and represses NLRP3 expression. Knocking down TTP in primary macrophages leads to an increased induction of NLRP3 by LPS, which is also accompanied by increased Caspase-1 and IL-1β cleavage upon NLRP3, but not AIM2 or NLRC4 inflammasome activation. Furthermore, we found that human NLRP3 can be alternatively polyadenylated, producing a short 3'-UTR isoform that excludes regulatory elements, including the TTP- and miRNA-223-binding sites. Because TTP also represses IL-1β expression, it is a dual inhibitor of the IL-1β system, regulating expression of the cytokine and the upstream controller NLRP3.

Upstream control of river anastomosis by sediment overloading, upper Columbia River, British Columbia, Canada

AbstractAnastomosing rivers, systems of multiple interconnected channels that enclose floodbasins, constitute a major category of rivers for which various sedimentary facies models have been developed. While the sedimentary products of anastomosing rivers are relatively well‐known, their genesis is still debated. A rapidly growing number of ancient alluvial successions being interpreted as of anastomosing river origin, including important hydrocarbon reservoirs, urge the development of robust models for the genesis of anastomosis, to facilitate better interpretation of ancient depositional settings and controls. The upper Columbia River, British Columbia, Canada, is the most‐studied anastomosing river and has played a key role in the development of an anastomosing river facies model. Two hypotheses for the origin of upper Columbia River anastomosis include the following: (i) downstream control by aggrading cross‐valley alluvial fans; and (ii) upstream control by excessive bedload input from tributaries. Both upstream and downstream control may force aggradation and avulsions in the upper Columbia River. In order to test both hypotheses, long‐term (millennia‐scale) floodplain sedimentation rates and avulsion frequencies are calculated using 14C‐dated deeply buried organic floodplain material from cross‐valley borehole transects. The results indicate a downstream decrease in floodplain sedimentation rate and avulsion frequency along the anastomosed reach, which is consistent with dominant upstream control by sediment overloading. The data here link recent avulsion activity to increased sediment supply during the Little Ice Age (ca 1100 to 1950 ad). This link is supported by data showing that sediment supply to the upper Columbia study reach fluctuated in response to Holocene glacial advances and retreats in the hinterland. Upstream control of anastomosis has considerable implications for the reconstruction of the setting of interpreted ancient anastomosing systems. The present research underscores that anastomosing systems typically occur in relatively proximal settings with abundant sediment supplied to low‐gradient floodplains, a situation commonly found in intermontane and foreland basins.

Variation in reach-scale bankfull discharge of the Jingjiang Reach undergoing upstream and downstream boundary controls

Remarkable channel degradation has occurred in the Jingjiang Reach of the Middle Yangtze River, since the operation of the Three Gorges Project, which has caused significant geomorphic adjustments, including the variation in bankfull discharge. Bankfull discharge is a key indicator of flood-discharge capacity in the Jingjiang Reach, which can adjust in response to the altered water and sediment conditions and local base-level changes. Therefore, it is important to investigate the variation in reach-scale bankfull discharge, because of longitudinal variability in channel geometry and bankfull discharge in the study reach. In this study, a general method to calculate the section-scale bankfull discharge using the simulated stage-discharge relation is outlined briefly, and an integrated method is then presented for estimating the reach-scale bankfull discharge. The post-flood reach-scale bankfull discharges in the study reach from 2002 to 2015 were calculated, using the proposed method, based on surveyed post-flood profiles at 171 sections and measured hydrological data at three hydrometric sections and eight water gauge sections. The calculated results indicate that: (i) the reach-scale bankfull discharge in the Jingjiang Reach ranged between 32,731 and 38,949m3/s over this period, with the average bankfull discharge in the Upper Jingjiang Reach being generally greater than the value in the Lower Jingjiang Reach; (ii) the magnitude of the reach-scale bankfull discharge responded well to the cumulative effect of incoming flow and sediment conditions at the inlet boundary, as well as the change of local base level at the outlet boundary; and (iii) the flood-discharge capacity of the reach was controlled by both the upstream and downstream boundary conditions, and the reach-scale bankfull discharge was expressed by an empirical function of the previous five-year average fluvial erosion intensity during flood seasons at Zhicheng, and the difference between the flood-season average water stages at Zhicheng (upstream) and Lianhuatang (downstream), with a relatively high correlation degree between them being obtained. This relation for the prediction of reach-scale bankfull discharge was verified using the measurements in 2014–2015.

Experimental reductions in stream flow alter litter processing and consumer subsidies in headwater streams

Summary Forested headwater streams are connected to their surrounding catchments by a reliance on terrestrial subsidies. Changes in precipitation patterns and stream flow represent a potential disruption in stream ecosystem function, as the delivery of terrestrial detritus to aquatic consumers and downstream transport are compromised. The potential effect of drying on decomposition is critical to understanding ecosystem processes in these detritus‐driven ecosystems. In this study, we experimentally altered stream connectivity to examine how altered water availability would influence litter decomposition. We used three catchments in the Coweeta Hydrologic Lab in North Carolina, U.S.A., establishing sites that were always wet, intermediately wet and completely terrestrial, while also experimentally diverting significant surface flow from downstream locations for several months. The flow manipulation significantly reduced the amount of water available to the three study reaches, leading to drastic changes in organic matter accumulation. Stream temperature and dissolved oxygen changed during the manipulation but only in response to season. Nutrient concentrations remained low or below detection during the experiment, demonstrating no response to the manipulation. Red maple and white oak demonstrated significantly different mass loss during the first few days of the experiment, but by the completion of the experiment, location was a more significant determinant of breakdown rate than leaf identity. Leaves placed in sites that were consistently wet decomposed at a higher rate than those in bank or terrestrial sites. Initially, leaf decomposition varied significantly based on site type and presence of water, which led to disruptions in microbial and macroinvertebrate colonisation and processing. High flows during large winter storms reconnected dried reaches and stimulated rates of decomposition due to colonisation by microbes and macroinvertebrates. Macroinvertebrate densities tracked microbial biomass accumulation on leaves, but were dependent upon location. Leaves in the manipulated reaches had significantly higher macroinvertebrate densities compared to the upstream control in the winter and spring in response to the delayed wetting of large standing stocks of leaves and subsequent colonisation by microbes. Our study demonstrated that even minor disruptions in stream connectivity at key times of the year have community‐ and ecosystem‐level influences that alter decomposition. The resilience of these ecosystems will depend on the frequency of disturbances and the ability of organisms to adapt to changing resource conditions.

Controls On the Geometry And Evolution of Humid-Tropical Fluvial Systems: Insights From 3D Seismic Geomorphological Analysis of the Malay Basin, Sunda Shelf, Southeast Asia

Abstract High-resolution three-dimensional (3D) seismic reflection data from the Pleistocene-to-Recent succession of the Malay Basin (Sunda Shelf, SE Asia) have been used to evaluate the geometry, dimensions, distribution, and evolution of humid-tropical fluvial channel systems. Based on their seismic expression and variations in sinuosity and depth, we identify six fluvial channel types, which occur in eight, seismically defined, 18–145-m-thick depositional units. Each unit is characterized by a consistent vertical change in channel-body geometry and dimensions as follows (bottom to top): (1) relatively large (300–3000 m wide and 15–45 m deep), straight to low-sinuosity channels and/or large incised valleys at their bases, and (2) smaller (75–250 m wide and 8–23 m deep), highly sinuous channels at their tops. This cyclical stratigraphic architecture is interpreted as a mainly climatically driven change in fluvial discharge and sediment supply, rather than by eustatically or tectonically driven changes in relative sea level based on (i) the study area was located far upstream (ca. 700 km) of the coeval shoreline, and (ii) tectonically quiescent nature of the basin during the Pleistocene to Recent. Although the upstream controls were likely the main controls on the stratigraphic organization (Units 2–4 and 6), the large incised valleys (Units 5 and 7) are interpreted to be formed due a relative sea-level fall during the Last Glacial Maximum (LGM). This study demonstrates how an improved understanding of the temporal and spatial variability of fluvial channel systems can be obtained through detailed analysis of regionally extensive, high-resolution 3D seismic reflection data. In particular, regional constraints on channel geometry, scale, and orientation can be more confidently determined than is typically permitted by deeper, lower-resolution subsurface data. Furthermore, we have provided quantitative constraints on the dimensions, geometries, and paleohydrology of humid-tropical fluvial systems, which form significant, but generally less well-imaged, hydrocarbon-bearing reservoirs, in the more deeply buried parts of the Malay Basin and in many other basins around the world.

Evaluation of TSS, BOD5, and TP in Sewage Effluent Receiving Sambul River

Proper treatment of sewage to remove suspended solids, organic matter and nutrients is necessary before the effluent is discharged into aquatic bodies. The major environmental concern at Sambul river is the potential pollution by effluent received from sewage treatment plant in Moi University. In this study, evaluation of the Sambul river was analysed using key water quality parameters, and comparisons made with those of the National Environmental Management Authority (NEMA). Purposive sampling design was used to select three sampling points; outlet where sewage effluent from STP is discharged into Sambul river, downstream of Sambul river where bio-treated sewage has mixed with river Sambul waters, and upstream (control) of Sambul river where the river water does not mix with STP effluent. A total of 72 water samples were collected for this study. At each sampling point, triplicate water samples for analysis were collected bi-weekly in sterilized plastic bottles from May to August 2015. Total suspended solids (TSS), BOD5 and total phosphorus (TP) were determined using standard laboratory methods. Results showed that levels of TSS, BOD5 and TP were within the acceptable standards of NEMA. Upstream parameters showed no significant differences with those of downstream (BOD F4,115=38965.46; p=0.9734; TSS F4,115=708.50; p=0.9999; total phosphorus F4,115=2107.17; p=0.9972), indicating that there is no change in water quality at river Sambul as a result of effluent received from STP.

The importance of controlling the upstream body wake in tandem cylinders system for noise reduction

This work numerically investigates the importance of controlling the wake of upstream body in the tandem cylinders aiming at aerodynamics noise reduction. The two-dimensional unsteady Reynolds-averaged Navier–Stokes approach with the k–ω turbulence model and Ffowcs Williams–Hawkings method are employed to simulate the flow field and the aerodynamics noise, respectively. The flow in the porous media is calculated by a volume-averaged model. Analogy to the mass-spring-damper system, one preliminary model is proposed to reveal the key role of stabilizing the upstream body wake. The simulations of different porous materials coating designs are implemented to corroborate the model and provide more details of flow modification by porous materials coating. Results indicate that the porous materials coating designed on the upstream cylinder can decrease the wake impingement on the downstream cylinder via suppressing the vortex shedding. Subsequently, not only the tonal noise but also the broadband noise level of tandem system can be reduced. It is also clarified that the effects of downstream cylinder absorption and downstream cylinder wake control by porous materials coating is not comparable with the upstream cylinder wake control. The present study gives a new idea to flow control and noise reduction of the multibody systems considering efficiency and economy.

Aire Downregulation Is Associated with Changes in the Posttranscriptional Control of Peripheral Tissue Antigens in Medullary Thymic Epithelial Cells.

Autoimmune regulator (Aire) is a transcriptional regulator of peripheral tissue antigens (PTAs) and microRNAs (miRNAs) in medullary thymic epithelial cells (mTECs). In this study, we tested the hypothesis that Aire also played a role as an upstream posttranscriptional controller in these cells and that variation in its expression might be associated with changes in the interactions between miRNAs and the mRNAs encoding PTAs. We demonstrated that downregulation of Aire in vivo in the thymuses of BALB/c mice imbalanced the large-scale expression of these two RNA species and consequently their interactions. The expression profiles of a large set of mTEC miRNAs and mRNAs isolated from the thymuses of mice subjected (or not) to small-interfering-induced Aire gene knockdown revealed that 87 miRNAs and 4,558 mRNAs were differentially expressed. The reconstruction of the miRNA–mRNA interaction networks demonstrated that interactions between these RNAs were under Aire influence and therefore changed when this gene was downregulated. Prior to Aire-knockdown, only members of the miR-let-7 family interacted with a set of PTA mRNAs. Under Aire-knockdown conditions, a larger set of miRNA families and their members established this type of interaction. Notably, no previously described Aire-dependent PTA interacted with the miRNAs, indicating that these PTAs were somehow refractory. The miRNA–mRNA interactions were validated by calculating the minimal free energy of the pairings between the miRNA seed regions and the mRNA 3′ UTRs and within the cellular milieu using the luciferase reporter gene assay. These results suggest the existence of a link between transcriptional and posttranscriptional control because Aire downregulation alters the miRNA–mRNA network controlling PTAs in mTEC cells.

Numerical investigation of flow around square cylinder with an upstream control plate at low Reynolds numbers in tandem

The study focuses on the effect of gap spacing (g) ranging g = 1–7, Reynolds numbers (Re) ranging Re = 80–200 and the size of the control plate (w) varied from 0.1d to 1d (where d is the size of the main cylinder) on the flow around a square cylinder with an upstream control plate. Two-dimensional multiple-relaxation-time lattice Boltzmann method is used to find the optimum condition, where the maximum reduction in drag force and suppression of vortex shedding occurs. It is observed that the drag is reduced significantly and the fluctuating lift is also suppressed. The detailed wake structure mechanism within gap spacing and near wake vortex structures around and behind the main square cylinder in the presence of the control plate are studied and compared with a plain square cylinder. In this study, the optimum conditions for maximum drag reduction in terms of control plate width, gap spacings and Reynolds numbers are found. The single bluff body, shear layer reattachment, critical flow, two-row single bluff body, fully developed two-row vortex shedding and quasi-steady-flow patterns are found. The time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficients, variation in force statistics and inclination angles are discussed in detail for all observed flow patterns. The maximum reductions on the drag force are 99.82, 99.8, 99.8, 99.9, 99.98, 100.4, 100.1, 100.05 and 100.1% for Re = 80, 100, 120, 140, 150, 160, 180, 190 and 200, respectively.

Fish introductions and light modulate food web fluxes in tropical streams: a whole-ecosystem experimental approach.

Decades of ecological study have demonstrated the importance of top-down and bottom-up controls on food webs, yet few studies within this context have quantified the magnitude of energy and material fluxes at the whole-ecosystem scale. We examined top-down and bottom-up effects on food web fluxes using a field experiment that manipulated the presence of a consumer, the Trinidadian guppy Poecilia reticulata, and the production of basal resources by thinning the riparian forest canopy to increase incident light. To gauge the effects of these reach-scale manipulations on food web fluxes, we used a nitrogen (15 N) stable isotope tracer to compare basal resource treatments (thinned canopy vs. control) and consumer treatments (guppy introduction vs. control). The thinned canopy stream had higher primary production than the natural canopy control, leading to increased N fluxes to invertebrates that feed on benthic biofilms (grazers), fine benthic organic matter (collector-gatherers), and organic particles suspended in the water column (filter feeders). Stream reaches with guppies also had higher primary productivity and higher N fluxes to grazers and filter feeders. In contrast, N fluxes to collector-gatherers were reduced in guppy introduction reaches relative to upstream controls. N fluxes to leaf-shredding invertebrates, predatory invertebrates, and the other fish species present (Hart's killifish, Anablepsoides hartii) did not differ across light or guppy treatments, suggesting that effects on detritus-based linkages and upper trophic levels were not as strong. Effect sizes of guppy and canopy treatments on N flux rates were similar for most taxa, though guppy effects were the strongest for filter feeding invertebrates while canopy effects were the strongest for collector-gatherer invertebrates. Combined, these results extend previous knowledge about top-down and bottom-up controls on ecosystems by providing experimental, reach-scale evidence that both pathways can act simultaneously and have equally strong influence on nutrient fluxes from inorganic pools through primary consumers.

Chromatin Kinases Act on Transcription Factors and Histone Tails in Regulation of Inducible Transcription

The inflammatory response requires coordinated activation of both transcription factors and chromatin to induce transcription for defense against pathogens and environmental insults. We sought to elucidate the connections between inflammatory signaling pathways and chromatin through genomic footprinting of kinase activity and unbiased identification of prominent histone phosphorylation events.We identified H3 serine 28 phosphorylation (H3S28ph) as the principal stimulation-dependent histone modification and observed its enrichment at induced genes in mouse macrophages stimulated with bacterial lipopolysaccharide. Using pharmacological and genetic approaches, we identified mitogen- and stress-activated protein kinases (MSKs) as primary mediators of H3S28ph in macrophages. Cell-free transcription assays demonstrated that H3S28ph directly promotes p300/CBP-dependent transcription. Further, MSKs can activate both signal-responsive transcription factors and the chromatin template with additive effects on transcription. Specific inhibition of MSKs in macrophages selectively reduced transcription of stimulation-induced genes. Our results suggest that MSKs incorporate upstream signaling inputs and control multiple downstream regulators of inducible transcription.

Bluff body drag manipulation using pulsed jets and Coanda effect

The impact of fluidic actuation on the wake and drag of a three-dimensional blunt body is investigated experimentally. Jets blowing tangentially to the main flow force the wake with variable frequency and amplitude. Depending on the forcing conditions, two flow regimes can be distinguished. First, in the case of broadband actuation with frequencies comprising the natural wake time scale, the convection of the jet structures enhances wake entrainment, shortens the length of the recirculating flow and increases drag. Secondly, at higher actuation frequencies, shear-layer deviation leads to fluidic boat tailing of the wake. It additionally lowers its turbulent kinetic energy thus reducing the entrainment of momentum towards the recirculating flow. The combination of both mechanisms produces a rise in the base pressure and reduces the drag of the model. Both actuation regimes are characterized by complementary velocity, pressure and drag measurements at several upstream conditions and control parameters. By adding curved surfaces to deviate the jets by the Coanda effect, periodic actuation is reinforced and drag reductions of approximately 20 % are achieved. The unsteady Coanda blowing not only intensifies the flow deviation and the base pressure recovery but also preserves the unsteady high-frequency forcing effect on the turbulent field. The present results encourage further development of fluidic control to improve the aerodynamics of road vehicles and provide a complementary insight into the relation between wake dynamics and drag.

Upstream control of the frontal jet regulating plankton production in the Alboran Sea (Western Mediterranean)

AbstractUsing a coupled physical‐biological model, we document that a ∼30 km wide meandering jet constitutes a major source of biological enrichment in the Alboran Sea (Western Mediterranean) even in the absence of wind forcing and tidal dynamics. The level of enrichment is shown to vary markedly during the year depending on the upstream characteristics of the jet as it exits from the Gibraltar Strait. When its intensity is sufficiently low and characterized by weaker cross‐frontal density gradients during winter‐spring, the jet is weakly nonlinear and may not fulfill the necessary conditions for frontogenesis. It then remains weakly productive. In the case of stronger jet intensity (>1.1 Sv) accompanied by stronger cross‐frontal density and velocity gradients within the Alboran Sea during summer‐autumn, the frontal jet becomes strongly nonlinear and ageostrophic with large cross‐frontal vorticity changes on the order of planetary vorticity. Under these conditions, upward vertical velocities in the range 10–50 m d−1 supply nutrients into the euphotic layer more effectively and support high‐level frontogenesis‐induced phytoplankton production on the anticyclonic side of the main jet axis. The strong eddy pumping mechanism also provides a comparable level of plankton production within strongly nonlinear elongated cyclonic eddies along the outer periphery of the frontal jet. The plankton biomass is advected partially by the jet along its trajectory and dispersed within the basin by mesoscale eddies and meanders.

Gonado-histopathological changes, intersex and endocrine disruptor responses in relation to contaminant burden in Tilapia species from Ogun River, Nigeria

In the present study, we investigated the occurrence of intersex condition, histopathological changes in the gonad and endocrine disruptor biomarker responses in Tilapia species (Tilaipia guineensis, Sarotherodon galileaus and Oreochromis niloticus) along the Ogun River, Nigeria. The study sites covered a length of 320 km and a total of 1074 tilapias were collected from three sampling sites (Abeokuta, Isheri and Ikorodu) with different degrees of anthropogenic contamination. Samples were also collected from an upstream putative control site (Igboho) along the Ogun River. Hepatic transcript levels for vitellogenin (Vtg), zona radiata (Zrp) and aromatase (cyp19a1) were analyzed using real-time PCR. Gross gonadal morphology revealed a 24% prevalence of intersex showing visible testis and ovary in phenotypic females (25.4%) or males (74.6%). The intersex condition paralleled histopathological changes (ovotestis or testis-ova) in the gonads of female and male fish, respectively. Plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), 11-ketotestosterone (11-KT) and estradiol-17β (E2) were measured using enzyme immunoassay, showing that male fish from downstream of the control site had significantly higher plasma E2, LH, and FSH concentrations compared to females. Similarly, Vtg, Zrp and cyp19a1 mRNA was significantly higher in males, compared to females. Analysis of contaminants showed the presence of 15 PCB congeners, lindane and dieldrin, and 4-iso-nonylphenol (4-iso-NP) and 4-tert-octylphenol (4-tert-OP) in fish muscle and sediment samples from Ogun River. Principal component analysis (PCA) revealed site and sex relationships between measured biological responses to groups of environmental contaminants, showing that the endocrine disruptive responses in fish were associated with biota and sediment contaminant burden. In addition, strong positive correlations were observed between male fish and Zrp, cyp19a1, E2, LH, FSH, PCBs, 4-iso-NP and 4-tert-OP, suggesting possible feminization effects of these contaminants on the male. In female fish, PCBs, 4-iso-NP and 4-tert-OP showed positive relationships with 11-KT and gonadosomatic index (GSI), suggesting masculinization effects by these contaminants. Overall, our findings demonstrate a causal relationship between endocrine disruption and contaminants burden in Tilapias species from Ogun River.

Wathershed disturbance effects on total suspended solids and substrate stability in a headwater stream.

Freshwater ecosystems are known to be impaired by disturbances within their watersheds.These disturbances may result from multiple sources ranging from resource extraction to development (e.g. urban, residential, industrial, and commercial). Even low level disturbances have been shown to result in impairment to stream biota within the watershed. However when very low levels of disturbance occur, the mechanisms, resulting in impairment to the biological integrity of the freshwater ecosystem, are not known. The objective of this study is to examine the immediate effects of an anthropogenic disturbance of less than 1% of the watershed area. Baseline conditions were established and total suspended solids (TSS) and substrate mobility, were monitored and compared between pre and post disturbance conditions. Disturbance was created by timbering a 0.24 acre area in the 89 acre watershed. The stream was separated into three different reaches: Site 1 (the downstream recovery reach), Site 2B (immediately downstream of disturbance) reach), and Site 3 (the upstream control reach). The data shows variation, at the sites, in suspended and settled sediment as indicated by TSS and substrate mobility. Sites downstream of the disturbance, Site 2B and Site 1, increased in substrate mobility compared to the up gradient site (Site 3). Suspended sediment increased at all three sites post-disturbance.

Hospital Effluents Are One of Several Sources of Metal, Antibiotic Resistance Genes, and Bacterial Markers Disseminated in Sub-Saharan Urban Rivers

Data concerning the occurrence of emerging biological contaminants such as antibiotic resistance genes (ARGs) and fecal indicator bacteria (FIB) in aquatic environments in Sub-Saharan African countries is limited. On the other hand, antibiotic resistance remains a worldwide problem which may pose serious potential risks to human and animal health. Consequently, there is a growing number of reports concerning the prevalence and dissemination of these contaminants into various environmental compartments. Sediments provide the opportunity to reconstruct the pollution history and evaluate impacts so this study investigates the abundance and distribution of toxic metals, FIB, and ARGs released from hospital effluent wastewaters and their presence in river sediments receiving systems. ARGs (blaTEM, blaCTX-M, blaSHV, and aadA), total bacterial load, and selected bacterial species FIB [Escherichia coli, Enterococcus (ENT)] and species (Psd) were quantified by targeting species specific genes using quantitative PCR (qPCR) in total DNA extracted from the sediments recovered from 4 hospital outlet pipes (HOP) and their river receiving systems in the City of Kinshasa in the Democratic Republic of the Congo. The results highlight the great concentration of toxic metals in HOP, reaching the values (in mg kg−1) of 47.9 (Cr), 213.6 (Cu), 1434.4 (Zn), 2.6 (Cd), 281.5 (Pb), and 13.6 (Hg). The results also highlight the highest (P < 0.05) values of 16S rRNA, FIB, and ARGs copy numbers in all sampling sites including upstream (control site), discharge point, and downstream of receiving rivers, indicating that the hospital effluent water is not an exclusive source of the biological contaminants entering the urban rivers. Significant correlation were observed between (i) all analyzed ARGs and total bacterial load (16S rRNA) 0.51 to 0.72 (p < 0.001, n = 65); (ii) ARGs (except blaTEM) and FIB and Psd 0.57 < r < 0.82 (p < 0.001, n = 65); and (iii) ARGs (except blaTEM) and toxic metals (Cd, Cr, Cu, and Zn) 0.44 to 0.72, (p < 0.001, n = 65). These findings demonstrate that several sources including hospital and urban wastewaters contribute to the spread of toxic metals and biological emerging contaminants in aquatic ecosystems.