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In light of rapid shifts in biodiversity associated with human impacts, there is an urgent need to understand how changing patterns in biodiversity impact ecosystem function. Functional redundancy is hypothesized to promote ecological resilience and stability, as ecosystem function of communities with more redundant species (those that perform similar functions) should be buffered against the loss of individual species. While functional redundancy is being increasingly quantified, few studies have linked differences in redundancy across communities to ecological outcomes. We conducted a review and meta‐analysis to determine whether empirical evidence supports the asserted link between functional redundancy and ecosystem stability and resilience. We reviewed 423 research articles and assembled a data set of 32 studies from 15 articles across aquatic and terrestrial ecosystems. Overall, the mean correlation between functional redundancy and ecological stability/resilience was positive. The mean positive effect of functional redundancy was greater for studies in which redundancy was measured as species richness within functional groups (vs. metrics independent of species richness), but species richness itself was not correlated with effect size. The results of this meta‐analysis indicate that functional redundancy may positively affect community stability and resilience to disturbance, but more empirical work is needed including more experimental studies, partitioning of richness and redundancy effects, and links to ecosystem functions.

Effects of nitrogen pollution on bacterial community shifts in river sediments remain barely understood. Here, we investigated the bacterial communities in sediments of urban and suburban rivers in a highly urbanized city, Shanghai. Sediment nitrate (NO3−) and ammonia (NH4+) were highly accumulated in urban river. Operation Taxonomic Units (OTUs), Abundance-based Coverage Estimators (ACEs) and Chao 1 estimator in urban rivers were slightly lower than those in suburban rivers, while Shannon and Simpson indices were higher in urban rivers than those in suburban rivers. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant bacterial phylum communities, accounting for 68.5–84.9% of all communities. In particular, the relative abundances of Firmicutes and Nitrospirae were significantly higher in suburban rivers than in urban rivers, while relative abundances of Bacteroidetes, Verrucomicrobia, and Spirochaetes were significantly lower in suburban rivers than in urban rivers. NH4+ was significantly and negatively correlated with abundances of Firmicutes, Nitrospirae, and Actinobacteria. Importantly, the significant and negative effects of sediment NH4+ on bacterial richness and diversity suggested that nitrogen pollution likely contribute to the decrease in the bacterial richness and diversity. The results highlight that nitrogen enrichment could drive the shifts of bacterial abundance and diversity in the urban river sediments where are strongly influenced by human activities under the rapid urbanization stress.

Riverine dissolved organic matter (DOM) is a major source of reduced carbon exported from land to marine environments, and the inflow of riverine organic matter greatly affects biogeochemical cycling in estuaries and bays. Thus, any change in DOM composition, such as changes caused by flood waters as a result of storms and hurricanes, can subsequently affect estuarine environments. To investigate the impact of high flow events on riverine DOM, multidimensional molecular level information of DOM from four south Texas Rivers (Aransas, Lavaca, Mission, and Nueces Rivers) was acquired using high-resolution Ion Mobility Quadrupole Time of Flight Liquid Chromatography Mass Spectrometry (IM Q-TOF LCMS). Base-flow samples were collected in May, July and October of 2016, June of 2017, and March of 2018, while high-flow samples were collected in September of 2017, and June and September of 2018. Based on the molecular formula assigned from IM Q-TOF LCMS, H/C ratio decreased during high-flow event (1.52 to 1.51 in ESI+; 1.19 to 1.07 in ESI-), while O/C ratio increased (0.31 to 0.33 in ESI-). Furthermore, DOM shifted from a protein-like and lipid-like dominated community at base flow condition, to a lignin, tannin and condensed aromatic structure dominated one during high flow event based on MS and tandem MS data. These changes in high-flow riverine DOM indicate an increase of terrestrial signal, which likely is a result of mobilization of terrestrial organic matter from the watersheds by flooding. These mobilized DOM, though refractory at high-flow condition in rivers, could be reactive in coastal regions when condition changes, and thus potentially fuel microbial activities downstream. In addition, about 3.76 – 21.8% of DOM molecules contain structural isomers among different flow conditions. This low number of isomer percentages suggests that as the products of various enzymatic biochemical reactions, the number of isomers in DOM is constrained. Taken together, our study provides insights into structural changes of riverine DOM in response to extreme climate events in subtropical regions and have implications in understanding biogeochemical changes in estuaries under a changing climate.

Stretch bending is a popular forming technique aiming at forming the long product’s axis into a desired curvature with the cross-section remaining constant. The most efficient and convenient method to prevent the defects in stretch bending such as axial springback and cross-sectional distortion is the optimization of forming path. In this work, a function of stretch length and bending angle is utilized to represent the forming path, and two new variables, total stretch length and distribution ratio, are proposed to better describe the effect of forming path on forming quality. Based on the data obtained from finite element simulation, a machine learning model is established to rapidly predict forming quality of the rail with a hat-shaped section. The forming path is optimized by multi-objective optimization method based on NSGA-II algorithm. The results show that the stretch bending quality is mainly determined by the total stretch, while the stretch distribution in three forming steps (e.g., pre-stretch, bend stretch and post-stretch) is a minor factor in controlling stretch bending quality with a few exceptions. With total stretch’s increment, the forming angle firstly increases dramatically and tends to a steady state at last, while the cross-sectional distortion increases constantly. The optimal forming path obtained indicates that the stretch of optimal forming process is an equal-ratio combination of the post-stretch and bending stretch.

Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread organic contaminants in the environment, and anthropogenic activities can produce PAHs through a variety of pyrogenic or petrogenic means. Knowing the concentrations and sources of PAHs helps evaluate ecosystem health and manage natural resources. In this study, 16 US Environmental Protection Agency priority PAHs were analyzed in water and sediment samples collected from September 2021 to September 2023 in four bay systems along the south and central Texas coast, which are a hotpot of crude oil transportation in the United States. Our results indicated that the total concentration of PAHs ranged from 1.9 to 8.3 ng/mL in surface waters (< 0.5 m) and from 520 to 1257 ng/g in surface sediments (top 5 cm). Grain size analysis revealed that the sediment was dominated by silt (4 - 63 μm), followed by clay (< 4 μm) and sand (> 63 μm) fractions. Both organic carbon and clay content were shown to play a significant role in controlling the PAH content in sediments. Diagnostic ratios indicated that PAHs were primarily sourced via pyrolytic processes, such as the combustion of fossil fuels. Additional sampling at Port Bay, a shallow, secondary bay in the Mission-Aransas National Estuarine Research Reserve, implicated a strong role of resuspension in the distribution and composition of PAHs in the bay systems studied. Overall, these data offer insights into the concentration levels and sources of PAHs in this key region housing oil production and transportation in the United States.

The ocean microbe‐metabolite network involves thousands of individual metabolites that encompass a breadth of chemical diversity and biological functions. These microbial metabolites mediate biogeochemical cycles, facilitate ecological relationships, and impact ecosystem health. While analytical advancements have begun to illuminate such roles, a challenge in navigating the deluge of marine metabolomics information is to identify a subset of metabolites that have the greatest ecosystem impact. Here, we present an ecological framework to distill knowledge of fundamental metabolites that underpin marine ecosystems. We borrow terms from macroecology that describe important species, namely “dominant,” “keystone,” and “indicator” species, and apply these designations to metabolites within the ocean microbial metabolome. These selected metabolites may shape marine community structure, function, and health and provide focal points for enhanced study of microbe‐metabolite networks. Applying ecological concepts to marine metabolites provides a path to leverage metabolomics data to better describe and predict marine microbial ecosystems.

The effect of photomineralization on the carbon cycle in a eutrophic, semiarid estuary (Baffin Bay, Texas) was investigated using closed‐system incubations. Photochemical production rate of dissolved inorganic carbon ranged from 0.16 to 0.68 μM hr−1, with a daily removal of 0.3∼1.5% of the standing stock of dissolved organic carbon (DOC). The photomineralization rate was negatively correlated with chlorophyll a concentration, suggesting that plankton‐derived DOC was less photoreactive to solar radiation. The stable carbon isotope composition (δ13C∼ −18.6‰) of degraded DOC, as calculated using the DIC “Keeling” plot, further indicated high photochemical lability of 13C‐enriched DOC in this semiarid environment. Our finding showed that photomineralization of 13C‐enriched DOC is an important component of carbon cycle in this system, and this process does not necessarily remove 13C‐depleted organic carbon as observed in other coastal systems.

Major hurricanes can greatly affect sediment biogeochemical processes in coastal bays and estuaries through strong storm surges and resuspension, yet the impacts on sediment geochemistry have rarely been evaluated. Here, the sediment geochemistry of the Mission Aransas Estuary, Texas, was systematically evaluated prior to and after Hurricane Harvey, a Category 4 storm. The median grain size of the surface sediments in the estuary significantly increased, but the bulk sediment total organic carbon content (TOC%) remained relatively constant. The concentration and composition of several organic chemical classes in the sediment were altered in distinctly different patterns. Accessory pigments showed that cyanobacterial materials in surface sediments increased immediately after Harvey, but returned to pre-Harvey levels 5 months post-hurricane. Pheophorbide decreased significantly after Harvey, but also recovered within 7 months, suggesting resilience of the benthic community. In contrast, polycyclic aromatic hydrocarbons (PAHs) and n -alkanes decreased (5–10 folds) 5 months after Hurricane Harvey and remained low 1 year later. The loss of PAHs and n -alkanes from the sediment might be related to increased solubility due to decreased salinity and strong resuspension during the storm surge. Overall, the strong storm surge and resuspension of sediment by Hurricane Harvey presented a major disturbance to the geochemistry of surface sediment in the MAE, but the impact on individual organic chemical classes depended on their sources, chemical properties, and/or association with fine clay minerals.

As a gradual deformation process like roll forming, chain-die forming is attractive to manufacturing advanced high-strength steel (AHSS) channels. The gradual forming mode induces complex and longitudinally discrepant springback and brings additional difficulty to the die design of AHSS forming. In this work, a new chain-die design method by adopting a multi-cross-section compensation strategy is proposed to compensate for the longitudinally discrepant springback and bow. A hat geometry with six design variables is adopted to ensure an undercut-free and smooth optimized die surface. The sectional springback compensation is taken as a multi-objective optimization problem, and the non-dominated sorting genetic algorithm-II is used to minimize the deviation between calculated sectional springback profiles and desired geometry. In addition, the longitudinal bow is also taken into account with an optimal counterpart arc on the web. The optimal results indicate that the non-uniform springback in chain-die forming exhibits a linear variation along the longitudinal direction for the constant hat channel. Chain-die forming experiments of constant and variable AHSS channels are carried out for verification, and both the springback and longitudinal bow are reduced by using the proposed die design method.

Abstract Sheet metal channels with variable sections or local features have been widely used in automobile and construction industries, and novel forming techniques, such as flexible roll forming process, flexibly reconfigurable roll forming process, Deakin’s flexible forming facility, and chain-die forming recently have been developed to manufacture those channels. In this paper, the feasibility of chain-die forming technique to manufacture channels with variable sections is systematically investigated through experiment and finite element simulation by taking 6 types of channel products as demonstration, including three variable-width and three variable-depth profiles. The forming process of the channels shows a combination of roll forming and stamping, and this roll-stamp mode has great potential in manufacturing a wide variety of channels with variable cross-sections. The formability for roll-stamp forming variable-depth channels is evaluated through finite element simulation and forming limit diagram. The roll-stamp mode can be discomposed into roll forming longitudinally and stamping vertically, and can achieve a reduction in forming load by the maximum of 33.9% compared with the conventional stamping in forming the flange step product. The forming direction sensitivity of the variable-width feature is discussed from the aspect of web arch height development.