Release characteristics of arsenic from sediments and its source or sink competition with phosphorus: A case of a great lake with grass-algae alternation.

The arsenic (As) release from sediments in great lakes is affected by various factors. In this study, the characteristics of As release from sediments was investigated, and the As sources and sinks with the strengths in sediments from different areas (grass-type, algae-type, and grass-algae alternation areas) in great shallow lakes (Taihu Lake, China) were analyzed, and the influence of P competition in the process of As release was also studied. The results showed that changing trend of the values of equilibrium As concentration in sediments were consistent with the regional changes (0 to 28.12 µg/L), and the sediments from algae-type areas had the higher values. The sediments from western lake and northwest lake bay were a strong As and a weak P source, and the north lake bay had the opposite trend of these two regions. Intense P source competition with As from the sediments occurred in algae-type areas. The grass-type areas had strong As and P retention capacities, indicating a sink role of sediment with high As and P sorption capacities. The degree of As and P saturation had similar trend in sediments, and the grass-type areas had the higher values, 18.3%-21.4% and 15.31%-20.34%, respectively. Contribution analysis results showed that most of As release contribution was from the bottom (30-50 cm) sediments, and the surface (0-10 cm) sediments from algae-type areas contributed more to the overlying water than other region.

Efficiency and mechanism of controlling phosphorus release from sediment using a biological aluminum-based P-inactivation agent.

Eutrophication is a significant challenge for surface water, with sediment phosphorus (P) release being a key contributor. Although biological aluminum-based P-inactivation agent (BA-PIA) has shown effectiveness in controlling P release from sediment, the efficiency and mechanism by BA-PIA capping is still not fully understood. This study explored the efficiency and mechanism of using BA-PIA capping controlling P release from sediment. The main mechanisms controlling P release from sediment via BA-PIA capping involved transforming mobile and less stable fractions into stable ones, passivating DGT-labile P and establishing a 13 mm 'P static layer' within the sediment. Additionally, BA-PIA's impact on Fe redox processes significantly influenced P release from the sediment. After BA-PIA capping, notable reductions were observed in total P, soluble reactive P (SRP), and diffusive gradient in thin-films (DGT)-measured labile P (DGT-labile P) concentration in the overlying water, with reduction rates of 95.6%, 92.7%, and 96.5%, respectively. After BA-PIA capping, the diffusion flux of SRP across the sediment-water interface and the apparent P diffusion flux decreased by 91.3% and 97.8%, respectively. Additionally, BA-PIA capping led to reduced concentrations of SRP, DGT-labile P, and DGT-measured labile Fe(II) in the sediment interstitial water. Notably, BA-PIA capping significantly reduced P content and facilitated transformation in the 0∼30 mm sediment layers but not in the 30∼45 mm and 45∼60 mm sediment layers for NaOH-extractable inorganic P and HCl-extracted P. These findings offer a theoretical basis and technical support for the practical application of BA-PIA capping to control P release from sediment.

How sediment dredging alters phosphorus dynamics in a lowland rural river?

China's lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus (P) from anthropogenic activities. However, quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas. A P dynamic model (River-P) was specifically designed for lowland rural rivers to address this challenge. This model was coupled with the Environmental Fluid Dynamics Code (EFDC) and the Phosphorus Dynamic Model for lowland Polder systems (PDP) to characterize P dynamics under the impact of dredging in a lowland rural river. Based on a two-year (2020-2021) dataset from a representative lowland rural river in the Lake Taihu Basin, China, the coupled model was calibrated and achieved a model performance (R2>0.59, RMSE<0.04 mg/L) for total P (TP) concentrations. Our research in the study river revealed that (1) the time scale for the effectiveness of sediment dredging for P control was ∼300 days, with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23% after dredging. (2) Dredging significantly reduced P release from sediment by 98%, while increased P resuspension and settling capacities by 16% and 46%, respectively. (3) The sediment-water interface (SWI) plays a critical role in P transfer within the river, as resuspension accounts for 16% of TP imports, and settling accounts for 47% of TP exports. Given the large P retention capacity of lowland rural rivers, drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity. Our study provides valuable insights for local environmental departments, allowing a comprehensive understanding of P dynamics in lowland rural rivers. This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures.

Polychlorinated biphenyls (PCBs) in the Persian Gulf and Gulf of Oman: baseline report on occurrence, distribution, and ecological risk assessment.

In the present study, 18 polychlorinated biphenyl (PCB) compounds were measured in marine sediments collected from 49 offshore stations in the Persian Gulf and the Gulf of Oman in 2019. After the last oceanographic cruise in 2006, no study has been performed on the offshore sediments of this region, and this is the first study on the PCBs in this area. The total amount of PCB compounds in the sediment samples ranged from 74.38 ng kg-1 (near Abu Musa Island) to 1212.98 ng kg-1 (near Siri and Kish Island). The maximum and minimum values of the individual detected PCB compounds were 175.88 ng kg-1 (PCB52) and 2.09 ng kg-1 (PCB156), respectively. The levels of total PCBs detected in sediments were lower than the Canadian interim sediment quality guideline value of 21500 ng kg-1 for marine sediments. The sedimentary mass inventories for Σ18PCBs were 0.6 and 0.2 mt for the Persian Gulf and Gulf of Oman, respectively.

Human and environmental risk assessment and plausible sources of toxic heavy metals at beach placers in southeast Sri Lanka.

Beach placers are typically rich in heavy minerals, which are crucial for a wide range of industrial applications. This study investigates the human and environmental risks posed by toxic heavy metals (As, Pb, Zn, Cu, Cr, Fe, V and Mn) in beach placers of southeastern Sri Lanka using 42 X-ray fluorescence data. Risk indicators (EF, Igeo, CF and PLI) indicate the polluted nature of the placers. Correlation analysis (correlation matrix and HCA) identified pollution sources as heavy mineral-rich rocks, agricultural fertilizers, pesticides and municipal wastes. The environmental impact caused by toxic metals is less in placers. The highest non-carcinogenic risks (HI) resulted by Cr (1.69E+00), V (4.29E+00) and Fe (2.06E+00) to children. The total cancer risk of As and Cr in placers is unacceptable (children: 2.60E-04, 2.48E-03, and adults: 3.14E-05, 2.87E-04, respectively). Different strategies are introduced to mitigate the identified risks in source areas and the coastal environment.

Plastic pollution on beaches in an Antillean manatee conservation area, Brazil.

The presence of plastic debris along shorelines is a widespread problem, and plastic debris can interact directly with marine wildlife. In northeast Brazil, the Antillean manatees are the most common marine mammals and use estuarine waters mainly as their home range. We aimed to investigate the characteristics of plastic debris on the estuarine-oceanic continuum and the accumulation density of plastic on beaches. The density of plastic debris on beaches located in transitional areas was 7-10-fold greater than that on beaches in estuarine and oceanic areas. Fragments were considered the most abundant form of plastic debris on all the beaches. Our findings could lead to improved pollution management in this marine protected area, principally due to the risks of remobilizing small plastic particles through tides and wind effects that scatter them in resting and feeding manatees areas.

Occurrence and spatial distribution of microplastics in water and sediments of Hatiya Island, Bangladesh and their risk assessment.

This research has evaluated the MPs distribution, characteristics, and potential threats of MPs in surface water and sediments from Hatiya Island. The results showed that the abundance of MPs was 139 ± 44 items/m3 in surface water and 493 ± 80 items/kg dw in sediments, indicating higher levels of MPs contamination in sediment samples. Fibers were the predominant kind of microplastics, and microscopic sizes (0.3-1.5 mm) MPs were generally more frequent and largely present in both the surface water and sediments. Fourier-transform infrared spectroscopy (FTIR) confirmed that polyethylene terephthalate was the major polymer component of microplastics in surface water, whereas polyethylene was the most abundant polymer in sediments. MPs contamination risk was examined based on multiple risk assessment models. Nemerow pollution index (NPI) and pollutant load index (PLI) show minimal pollution levels of MPs. But potential hazard index (PHI), potential ecological risk factor (Er), and potential ecological risk index (RI), indicate severe MPs contamination due to the presence of polyurethane, polycarbonate, polyvinyl chloride, epoxy that were hazardous MPs and exhibited a critical concern for MPs risk. These statistics will help to understand the environmental difficulties generated by MPs and which hazard is waiting for mankind in the future.

Source-risk and uncertainty assessment of trace metals in surface sediments of a human-dominated seaward catchment in eastern China.

Current total concentration-based methods for source attribution and risk assessment often overestimate metal risks, thereby impeding the formulation of effective risk management strategies. This study aims to develop a framework for source-specific risk assessment based on metal bioavailability in surface river sediments from a human-dominated seaward catchment in eastern China. Metal bioavailability was quantified using chemical fractionation results, and source apportionment was conducted using the positive matrix factorization (PMF) model. Risk assessment integrated these findings using two indices: the Potential Ecological Risk Index (PERI) and the Mean Probable Effect Concentration Quotient (mPEC-Q), with uncertainty addressed via Monte Carlo simulations. Results indicated that average total concentrations of Cu, Pb, Zn, Cr, Hg, Cd, and As exceeded their respective background levels by 1.63 to 15.00 times. The residual fraction constituted the majority, accounting for 53.84 % to 77.79 % of total concentrations, suggesting significant natural origins. However, source apportionment revealed a predominant contribution from anthropogenic activities, including industrial smelting, agricultural practices, and atmospheric deposition. The contributions were found to vary between 5.35 % and 40.03 % when the total concentration was adjusted to bioavailable content. Total concentration-based PERI/mPEC-Q assessments indicated high/moderate risk levels, decreasing to considerable/low risk levels with bioavailability adjustment. Hg and Cd were identified as priority metals. Further incorporating source appointment parameters into the risk assessment, industrial smelting was identified as the primary contributor, accounting for 66.06 % of total risk by total concentration and 65.63 % by bioavailability. This underscores the role of bioavailability in mitigating risk overestimation. Monte Carlo simulations validated industrial smelting as a major risk contributor. This study emphasizes the importance of considering bioavailability in the source-risk assessment of sediment-metals, crucial for targeted risk management in urbanized catchment areas.

Mitigating harmful cyanobacterial blooms in drinking water reservoirs through in-situ sediment resuspension.

Mitigating harmful cyanobacterial blooms is a global challenge, particularly crucial for safeguarding source water. Given the limitations of current technologies for application in drinking water reservoirs, we propose an innovative strategy based on in-situ sediment resuspension (SR). This method's effectiveness in cyanobacterial control and its potential impacts on water quality were assessed through laboratory culture experiments and further validated via field applications in five drinking water reservoirs. The results revealed that SR could significantly mitigate cyanobacterial growth, evidenced by the treated sets (removal rate: 3.82×106 cells L-1d-1) compared to the control set (growth rate: 2.22×107 cells L-1d-1) according to the laboratory experiments. The underlying mechanisms identified included underwater light reduction (2.38× increase in extinction coefficient) and flocculation and entrainment of cells by resuspended particles (30 % reduction per operation). Additional contributions were noted in the reduction of bioavailable phosphate and remediation of anaerobic sediment characterized by increased redox potential. This facilitated the oxidation of iron, which in turn promoted the co-precipitation of phosphate (removal rate: 46 µg L-1d-1) and inhibited its release from the sediment. The SR operation, devoid of importing extra substances, represents a safe and economical technology for controlling harmful cyanobacteria in drinking water reservoirs.

Stand age-related effects of mangrove on archaeal methanogenesis in sediments: Community assembly and co-occurrence patterns.

Mangrove sediment is a key source of methane emissions; however, archaea community structure dynamics and methanogenesis activities during long-term mangrove restoration remain unclear. In this study, microcosm incubations revealed a substantial reduction in microbial-mediated methane production potential from mangrove sediments with increasing stand age; methane production rates decreased from 0.42 ng g-1 d-1 in 6-year-old stands to 0.23 ng g-1 d-1 in 64-year-old stands. High-throughput sequencing revealed a reduction in community diversity because of specific microorganism colonization and species loss, notably a decline in the relative abundance of Bathyarchaeia in sediments of 64-year-old stands. In addition, mangrove sediments, especially those in older stands (20- and 64-year-old), had more complex and stable co-occurrence microbial networks than mudflats. Furthermore, archaea community assembly in older stands was dominated by stochastic processes wherein dispersal limitation was prominent, and that in younger stands (6- and 12-year-old) was driven by deterministic processes. The proportion of dispersal limitation of Bathyarchaeia and traditional methanogens in sediment decreased with an increase in stand age. Quantitative polymerase chain reaction analysis confirmed a decrease in Bathyarchaeia (from 3.50 to 0.54 copies g-1) and mcrA gene (from 3.83 to 0.25 copies g-1) abundance in mangrove sediments with an increase in stand age. These findings demonstrate the critical role of Bathyarchaeia in methanogenesis; the decline in microbial interactions and abundance, and the reduced proportion of dispersal limitation of Bathyarchaeia and traditional methanogens collectively contributed to the mitigation of microbial-mediated methane production potential in older mangrove stands.

Quantifying the sediment sorption of organic ultraviolet filter chemicals using solvophobic theory.

Hydrophobic organic chemicals (HOCs) that enter the aquatic environment often negatively impact organisms, endangering aquatic biodiversity. Understanding sediment sorption equilibria for these chemicals can properly direct mitigation efforts. In addition, many HOCs of environmental concern lack sufficient environmental fate data to adequately assess their risk to ecosystems and humans. In this study, a sorption method addressing solvophobic effects was used to quantify the sorption of an HOC of current environmental concern, OD-PABA (padimate O, 2-ethylhexyl-4-(dimethylamino)benzoate), to a variety of sediments. OD-PABA is an organic ultraviolet filter chemical used in commercial sun protection products; it has been shown to exhibit cytotoxic effects and is known to photochemically transform under natural sunlight conditions. Given its commercial use, it enters the aquatic environment via recreational use and wastewater treatment plant effluent. OD-PABA is strongly hydrophobic; to mitigate the adsorption of OD-PABA to the container walls during sorption experiments, a precise concentration of methanol was used to avoid solvophobic effects. This sorption method was used to determine the sorption capacities for OD-PABA of four sediment samples, each with unique geochemical characteristics. Sediment-water distribution coefficients (Kd) were quantified and were normalized to various sediment characteristics to assess the main driving force(s) for sorption of OD-PABA. Organic carbon content was found to be a main driving force, with organic carbon-normalized distribution coefficients (log Koc) ranging from 4.4 to 4.6 for sediments with total organic carbon (TOC) > 10%); the clay fraction was also found to be important, especially for sediments with low TOC. The sorption of para-aminobenzoic acid (PABA), a water-soluble analog of OD-PABA was also investigated to assess the experimental approach, yielding a log Koc of 2.1 for the sediment with the greatest TOC.

Artificial water regulation and natural flood processes control heavy metal concentrations and transport in the Yellow River, China.

Based on heavy metals daily observation at the Lijin station during water-sediment regulation (WSR) event and three natural floods in 2020, we examined the effects of different flood events on heavy metal in lower Yellow River, China. The results revealed that due to different water and sediment sources and processes influencing heavy metals dynamics, the dissolved Cr, Zn As and particulate heavy metals during natural flood events were higher than those during WSR event. Dissolved heavy metals increased during water regulation and decreased during sediment regulation. Using positive matrix factorization (PMF) model, we found that sources of dissolved heavy metals during WSR event were mainly from agricultural practices, rock and soil weathering, and industrial pollution. During flood events, particulate heavy metals' concentrations varied due to dilution, human activities, and reservoir influences, with industrial and agricultural sources significantly impacting Cu, Zn, As, and Pb levels.

Pollution level assessment, source apportionment, and health hazards of heavy metals and rare earth elements in the sediment core from the coast of Karachi, Pakistan.

Evaluating the elemental composition of sediment cores is essential for understanding environmental changes, including depositional variations, soil formation processes, and human influences. Such investigations offer insights into the biological, geochemical, and industrial impacts on sediment quality and the health of marine ecosystems. This study evaluates the pollution levels and their sources along the coast of Karachi, Pakistan, as well as the effects of pollution on human and ecological health. The core sediment's elemental composition was determined by Neutron Activation Analysis. The mean values in mg/kg of the elements are Al (34800), As (11.15), Ba (371), Br (18.40), Ca (118850), Ce (41.43), Co (10.29), Cr (62.41), Cs (5.27), Eu (0.80), Fe (22855), Hf (2.43), K (11210), La (20.84), Lu (0.26), Mg (21750), Mn (416), Na (8350), Nd (18.92), Rb (66.35), Sb (1.04), Sc (8.31), Se (8.23), Sm (3.88), Sn (17.05), Ta (0.77), Th (7.17), U (3.96), V (71.80), Yb (1.28) and Zn (581). Various pollution indices were used to assess the pollution level of these elements in the sediment core. Statistical tools like Pearson's correlation matrix and Factor analysis were utilized for source apportionment of these elements. Source apportionment showed the sources of heavy metals and rare earth elements are Ship breaking facilities, different types of refuse effluents carried by the Malir river into the sea and the geology of the area. Carcinogenic and non-carcinogenic health hazards associated with exposure to toxic metals were also calculated. The ecological risk factor and sediment quality index showed As and Zn may harm the marine environment. In conclusion, this study found that the sediment of Karachi's coast is polluted with high levels of As, Br, Ca, Cr, Sn, and Zn; with As, Cr and Zn posing a threat to the marine ecology as well as human health.

Potentially toxic elements in surface sediments of the Beibu Gulf, South Sea, China: Occurrence, bioavailability and probabilistic risk assessment.

At present, pollution of gulf sediments with potentially toxic elements (PTEs) has become a prominent marine environmental problem. This study thoroughly investigated the occurrence, bioavailability, and probabilistic risk of PTEs in the surface sediments of the Beibu Gulf. The average total concentrations (mg/kg) were 8.03 for As, 0.06 for Cd, 52.73 for Cr, 9.86 for Cu, 0.04 for Hg, 18.70 for Ni, 27.77 for Pb and 59.80 for Zn, respectively. The positive matrix factorization model revealed that the PTE enrichment was primarily due to composite sources from aquaculture and fisheries activities, industrial and agricultural sources. Risk assessment code and correlation analysis indicated that Cd had the highest bioavailability, influenced by TOC and TP. The probabilistic risk assessment model estimated a 60.83 % probability that the mixed PTEs in the Beibu Gulf's surface sediments could have toxic effects on aquatic life. These findings underscore the impact of intensive human activities on PTE pollution and highlight the need for further research on PTE ecotoxicology and pollution control strategies.

Effect-directed analysis and nontarget screening for identifying AhR-active substances in sediments of Gamcheon Harbor, South Korea.

Gamcheon Harbor in Busan, the largest port city in South Korea, is contaminated with persistent toxic substances, including polycyclic aromatic hydrocarbons (92 to 1700 ng g-1 dry mass (dm)) and styrene oligomers (17 to 520 ng g-1 dm). This study applied effect-directed analysis and nontarget screening (NTS) to identify aryl hydrocarbon receptor (AhR)-active substances in Gamcheon harbor sediments. Relatively great AhR-mediated potencies were found in RP-HPLC fractions, F2.7-F2.8 (mid-polar, log KOW 6-8) and F3.6-F3.7 (polar, log KOW 5-7). Target AhR agonists comprised up to 43% of total AhR-mediated potencies. NTS using GC-QTOFMS and LC-QTOFMS identified daphnoretin and isorhamnetin as significant AhR agonists, with relative potency values of 0.4 × 10-3 and 6.5 × 10-5, respectively, compared to benzo[a]pyrene. The major AhR agonists in the coastal sediments of Korea appeared to be region-specific. This approach is useful for identifying and managing key toxic substances in coastal ecosystems.

Ecophysiological responses of mangrove Kandelia obovata seedlings to bed-cleaning sludge from coastline shrimp ponds.

Cumulative effect of bed-cleaning sludge (BCS) from shrimp ponds on the physiology of Kandelia obovata seedling were investigated. Based on the accumulation rate of BCS discharged from shrimp ponds in mangrove forests, four types of sediment coverage thicknesses (SCT) of 0, 2, 4, and 8 cm were set up. With the increases in SCTs, photosynthetic rate, stomatal conductance, transpiration rates were lowest in SCT8; intercellular CO2 concentrations were lowest in SCT4. Leaf superoxide dismutase and peroxidase activities rose and then fell with the increases in SCTs, and Leaf malonaldehyde contents significantly increased. However, contents of leaf free proline, soluble protein and soluble sugar were lowest for SCT4. Root activity was highest for SCT4. Leaves had high N contents, while roots had high P contents. Overall, as for physiological parameters of K. obovata seedlings, SCTs <4 cm were suitable and the values up to 8 cm formed some stresses.

Hydrodynamics- and remote sensing-based model for estimating the effects of cohesive sediment transport on lagoon siltation in Southwestern Taiwan.

This study investigates localized siltation in the Cigu Lagoon, Southwestern Taiwan, using an integrated approach of hydrodynamic modeling and remote sensing. In regions where in situ data is scarce, remote sensing provides critical complementary data inputs for our sediment model. We employed a multilayered mud sediment model, incorporating initial suspended sediment concentration (SSC) data derived from Landsat imagery, to identify the morphological changes taking place in the lagoon. Over the past few decades, sandbar migration and sedimentation have led to a significant shrinkage of the Cigu Lagoon, which is now at risk of disappearing if a full understanding of the underlying factors is not reached. The loss of the lagoon would have severe implications for the local ecosystem and habitat, as well as for the fishermen who rely on the lagoon for their livelihoods. Our results showed that sedimentation in the Cigu Lagoon is a compounded consequence of the action of the tidal cycle and of waves. Throughout the simulation period, the SSC in the Cigu Lagoon ranged from 1 g m -3 to 50 g m -3. The annual siltation rate of the lagoon due to cohesive sediment transport was 0.82 cm. The simulation results showed that the siltation mainly occurred during the winter, with the dominant factor being the frequent strong waves at this time of year. This study suggests that a management plan for the Cigu Lagoon must be devised and implemented, and that remote sensing and hydrodynamic modeling are valuable tools in communicating about the complex processes involved in a sedimentary system and informing relevant decision-making at the stage of management.

A method for evaluating sediment-induced macroinvertebrate community composition changes in Idaho streams.

Human activities can increase sediment delivery to streams, changing the composition, distribution, and abundance of stream aquatic life. Few U.S. states have numeric water quality standards for streambed sediment under the Clean Water Act, so managers often need to develop local application-specific benchmarks. This study developed stream surface fine sediment <2 mm (sand and fines, SF) and macroinvertebrate fine sediment biotic index (FSBI) benchmarks and an application framework to test for sediment-induced macroinvertebrate community composition changes in 1st-4th order Idaho streams. FSBI reference benchmarks were calculated as the 25th percentile FSBI value among reference sites within three ecoregion-based site classes. Two approaches were used to develop SF benchmarks. Quantile regression was used to define reach-specific SF benchmarks representing an upper bound value expected under reference conditions. In addition, logistic regression was used to predict SF values with 50% and 75% probability that FSBI is worse than reference within each stream order and site class. The strength of association between SF benchmarks and macroinvertebrate community condition was evaluated by calculating relative risk using multiple datasets and examining responses of multiple macroinvertebrate indicators to SF benchmark status. SF reference benchmarks generally had stronger associations with poor macroinvertebrate condition than SF stressor-response benchmarks. Across datasets and macroinvertebrate indicators, poor macroinvertebrate condition was 1.8-3 times more likely when SF reference benchmarks were exceeded than when achieved. We propose rating the strength of evidence for a surface fine sediment-induced macroinvertebrate community composition change at the sample event scale as 'unlikely' if both SF and FSBI reference benchmarks are achieved, having 'mixed evidence' if only one reference benchmark is achieved, and 'likely' if both reference benchmarks are not achieved. We recommend combining ratings with other relevant data in a weight-of-evidence approach to assess if sediment impairs aquatic life.

Atlas of pacific sand lance (Ammodytes personatus) benthic habitat - Application of multibeam acoustics and directed sampling to identify viable subtidal substrates.

Defining and delineating species distribution and habitat is critical to informed management and conservation. This process is complicated in marine environments, where detection of marine taxa and characterization of marine habitat is more difficult. Small pelagic fishes and forage fishes are particularly challenging, though insights may be more accessible in species highly dependent on particular habitat. Pacific sand lance (Ammodytes personatus) is a common and ecologically-important pelagic fish that relies on specific benthic sediments for rest and refuge from predation. We applied multibeam echosounder (MBES) bathymetric data to develop high-definition benthic habitat maps and implemented multiyear sampling to assess potential habitat for sand lance via in situ sampling of sediments. We also applied acoustic Doppler current profilers (ADCP) data and tidally-driven volume-based ocean models to measure current strength and to visualize currents. We leveraged this data to further define and describe habitat for this important forage species. Sediment transport processes were mapped and areas of dispersal, embedment, and accumulation were evaluated. Dynamic bedform habitats, banner banks and glacial banks were identified as potential habitat and sampled for fish presence, density and sediment composition. In the central Salish Sea, approximately 25% of benthic substrates represent potential sand lance habitat. Sand lance prevalence and density correlated with substrate type and sediment coarseness. Densities were highest in areas of coarse grain sediments and presence was limited by fine particulates, such as silt and mud. Tidal currents appear important. Presence and densities of sand lance were correlated with current velocity and distance from current flow path. Nearly all viable sites were located on the immediate margins of high flow (<0.16 km from tidal currents with max speed of 1.72-2.58 m/s). While both flood and ebb were important, processes related to flood were dominant. Viable habitat was not constrained by depth. These results inform a developing atlas for sand lance in the central Salish Sea, provide new insights to subtidal sand lance habitat, characterize conditions that create and maintain subtidal benthic habitat, and provide a template for mapping habitat for this species in the coastal Pacific Ocean.

Interactive effects of aridity and local environmental factors on the functional trait composition and diversity of macroinvertebrate assemblages in dryland rivers.

Drought and local habitat alteration are major environmental stressors shaping the aquatic biota in dryland rivers. However, the combined effects of these factors on aquatic biodiversity remain poorly understood. We collected macroinvertebrate data from Central Asian dryland rivers in Xinjiang, China, from 2012 to 2022, to investigate the individual and interactive effects of drought (as indicated by increasing values of Aridity, AI) and local habitat conditions (fine sediments, velocity and pH) on aquatic macroinvertebrate functional trait composition and diversity. We found that interactions of the selected environmental stressors exhibited more frequent additive than synergistic or antagonistic effects, leading to shifts in macroinvertebrate functional trait composition and diversity accordingly. Interaction of AI and fine sediments showed more pronounced synergistic effects (positive or negative) compared to others and had positive influences on traits like small body size, ovoviviparity, etc. Functional diversity metrics responded differently to stressor interactions, with FRic and FDis being negatively affected, whereas FEve was positively correlated to stressor interaction, suggesting the complementary roles of functional diversity metrics to diagnose impacts of stressor interactions. Overall, our study provides new insights into macroinvertebrate assemblage-stressor relationships in dryland rivers and can help better assess, predict and manage aquatic biodiversity in these rivers under ongoing environmental change.