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.

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.

Distribution of total mercury in coastal sediments of Honda Bay, Palawan Island, the Philippines.

Honda Bay is considered as one of the mercury hotspots in the world due to its proximity to the abandoned Palawan Quicksilver Mine. In this study, a detailed sediment sampling conducted in between 2021 and 2022 where a total of 166 sediment samples were collected along the coast and analyzed for total mercury (THg) concentration. The study assessed mercury toxicity using the geoaccumulation index and compared Hg levels to sediment quality guidelines. The findings revealed a wide range of THg concentrations, from 0.0040 to 11.4702 mg/kg, with hotspots identified at the Honda Bay wharf and Tagburos River mouth. Mercury spreads to a large coastal area brought by tidal currents and the wave energy actions. The geoaccumulation index indicated moderate to strong Hg contamination in the vicinity of the hotspots and around 24.7-36.1 % of samples exceeded the sediment quality guidelines suggesting adverse biological effects in aquatic biota will frequently occur.

Analysis of heavy metals in sediments with different particle sizes and influencing factors in a mining area in Hunan Province.

Heavy metals mainly exist on the surface of sediment particles and are transported using particulate matter as carriers. Therefore, the particle size of sediment particles can affect the adsorption, release, and migration of heavy metals. This study aim to investigate the distribution characteristics and chemical fraction of Cd, Pb, and As contents in sediments of different particle sizes using the BCR method, and to determine the key factors affecting the distribution of heavy metals through mineralogical methods such as XRD and EDS. The results revealed that the overall content of various forms of heavy metals increases with the decrease of particle size, mainly presents in fine particles. The mineralogical analysis results indicated that fine particles predominantly contained clay minerals such as chlorite and illite and coarse particles mainly include primary minerals. Due to the mining areas in the middle-upstream, Cd, Pb and As were primarily associated with galena, sphalerite and pyrite, respectively. The distribution of heavy metals is jointly influenced by sediment particle size and sediment material composition.

Distribution characteristics, sources and risk assessment of heavy metals in the surface sediments from the largest tributary of the Lancang River in the Tibet Plateau, China.

Angqu, positioned in the eastern expanse of the Tibet Plateau, claims the title of the largest tributary to the Lancang River. In October and December of 2018, in the sediment of Angqu, a comprehensive investigation was conducted on nine heavy metals-arsenic (As), manganese (Mn), chromium (Cr), cadmium (Cd), lead (Pb), mercury (Hg), copper (Cu), zinc (Zn), and nickel (Ni). This investigation aimed to scrutinize the spatial and temporal distribution patterns of these metals, assess the pollution status and ecological risks associated with the sediments, and delve into the sources contributing to their presence. The research results indicate that the average concentrations of As, Hg, and Cd in Angqu sediments exceed the soil background values of Tibet, while the concentrations of other heavy metals are below the soil background values of Tibet. Notably, arsenic poses potential ecological risks. In Angqu sediments, the concentrations of Mn, Cu, Ni, and Pb are generally higher in the wet season, but the seasonal variations of heavy metals in Angqu sediments are not significant. The sediments in the Angqu Basin are predominantly affected by mercury Hg, Cd, and As, with varying degrees of pollution at different sampling points. In the main stream of Angqu (City section), Hg pollution has reached above a moderate level, whereas As pollution near the tributary is only slightly polluted. The analysis of heavy metal sources reveals that there are five primary contributors to heavy metals in surface sediments of Angqu: parent material, agricultural activities, groundwater, atmospheric deposition, and other unidentified sources. Mn, Cr, Pb, and Ni are mainly derived from soil parent material, accounting for more than 50%. About 60.82% of As comes primarily from groundwater. Zn and Cd are mainly sourced from agricultural activities, accounting for 41.25% and 34.33%, respectively. Additionally, 20.6% of Hg originates from atmospheric deposition.

Synergetic effects of chlorinated paraffins and microplastics on microbial communities and nitrogen cycling in deep-sea cold seep sediments.

Chlorinated paraffins (CPs) and microplastics (MPs) are commonly found in deep-sea cold seep sediments, where nitrogen cycling processes frequently occur. However, little is known about their combined effects on sedimentary microbial communities and nitrogen cycling in these environments. This study aimed to investigate the synergistic impacts of CPs and MPs on microbial communities and nitrogen cycling in deep-sea cold seep sediments through microcosm experiments. Our results demonstrated that the presence of CPs and MPs induced significant alterations in microbial community composition, promoting the growth of Halomonas. Furthermore, CPs and MPs were found to enhance nitrification, denitrification and anammox processes, which was evidenced by the higher abundance of genes associated with nitrification and denitrification, as well as increased activity of denitrification and anammox in the CPs and MPs-treatment groups compared to the control group. Additionally, the enhanced influence of CPs and MPs on denitrification was expected to promote nitrate-dependent and sulfate-dependent anaerobic oxidation of methane, thereby resulting in less methane released into the environment. These findings shed light on the potential consequences of simultaneous exposure to CPs and MPs on biogeochemical nitrogen cycling in deep-sea cold seep sediments.

Arctic threads: Microplastic fibres in Chukchi and Beaufort sea sediments.

The influx of microplastics (MPs) into the Arctic Ocean poses a collective risk, particularly with pronounced sea ice depletion due to global warming. A total of 73 replicate sediment samples were collected at different depths (38 to 79 m) from Chukchi and the Beaufort Seas at 8 stations in the Arctic region during the R/V Mirai cruise (MR22-06C) from August to September 2022. The average concentration of MPs is 79.25 ± 31.08 items/kg d.w. Fibrous MPs of 0-1 mm size range are predominant, with blue being the most prevalent colour. Polymer characterization identified polyethylene (PE) as the predominant polymer. Arctic Ocean regions face heightened health risks from the coexistence of MPs and harmful additives, amplifying concerns over plastic pollution. The alarming surge in MPs within Arctic sediment underscores the urgent need for a proactive, collaborative approach to mitigate this environmental threat and its far-reaching impacts.

Interactions of multiple stressors on the Bombay-duck Harpadon nehereus populations in a complex estuarine ecosystem.

In an era marked by unprecedented anthropogenic change, marine systems are increasingly subjected to interconnected and dynamic external stressors, which profoundly reshape the behavior and resilience of marine ecological components. Nevertheless, despite widespread recognition of the significance of stressor interactions, there persist notable knowledge deficits in quantifying their interactions and the specific biological consequences that result. To bridge this crucial gap, this research detected and examined the causal relationships between five key exogenous stressors in a complex estuarine ecosystem. Furthermore, a Bayesian Hierarchical Spatio-temporal modeling framework was proposed to quantitatively evaluate the distinct, interactive, and globally sensitive effects of multiple stressors on the population dynamics of a crucial fish species: Harpadon nehereus. The results showed that interactions were detected between fisheries pressure (FP), the Pacific Decadal Oscillation index (PDO), runoff volume (RV), and sediment load (SL), with five of these interactions producing significant synergistic effects on H. nehereus biomass. The SL*PDO and RV*PDO interactions had positive synergistic effects, albeit through differing mechanisms. The former interaction amplified the individual effects of each stressor, while the latter reversed the direction of the original impact. Indeed overall, the synergistic effect of multiple stressors was not favorable, with FP in particular posing the greatest threat to H. nehereus population. This threat was more pronounced at high SL or negative PDO phases. Therefore, local management efforts aimed at addressing multiple stressors and protecting resources should consider the findings. Additionally, although the velocity of climate change (VoCC) failed to produce significant interactions, changes in this stressor had the most sensitive impacts on the response of H. nehereus population. This research strives to enhance the dimensionality, generalizability, and flexibility of the quantification framework for marine multi-stressor interactions, aiming to foster broader research collaboration and jointly tackle the intricate pressures facing marine ecosystems.

Assessment of sediment yield and accumulation in reservoir: The case of Gibe One Reservoir, Southwestern Ethiopia.

Soil erosion and sediment buildup are the factors that speed up the decline in capacity and function of reservoirs, agricultural products, and water resources. In order to simulate sediment and runoff and map high sediment-yielding sub-basins in the Gibe Gojeb catchment in southwest Ethiopia, this study used the Soil and Water Assessment Tool (SWAT) model. Using data on sediment and river flow, calibration and validation were carried out. Between 2003 and 2016, the catchment produced an average annual sediment loading of 62.5 tons ha-1 yr-1, with loading fluctuations ranging from 0.2 to 108.4 tons ha-1 yr-1. The acceptable sediment yield threshold value ranges from 12.3 to 108.4 tons ha-1 yr-1 for 56 sub-basins, and from 0.2 to 10 tons ha-1 yr-1 for 5 sub-basins. The most significant sub-basins with very high to extremely severe sediment yields were sub-basins 1 to 30, 32 to 44, 47, 48, 50, 51, and 53 to 61. After thirteen years of operation, the yearly amount of 58,802 tons of sediment transferred from the catchment and deposited into Gibe One reservoir has decreased the capacity by 5.7 %. The accumulation of sediment in a reservoir has an impact on its functionality, power production, and capacity, affecting the safety of dams and the environment. The study's findings enhanced our comprehension of sediment accumulation in reservoirs and furnished us with the necessary information regarding reservoir safety, integrated soil, and water management.

Presence of pesticide-tolerant microorganisms in high-altitude pristine lakes within Singalila Ridge of the Himalayas.

This is the first report on high pesticide tolerance displayed by the microbiota isolated from the sediments of two high-altitude lakes, located in the Singalila National Park, Singalila Ridge of the Himalayas. Given the remote location of these lakes, direct exposure to chemical pesticides is highly unlikely. However, the high tolerance to commonly used pesticides exhibited, i.e. up to 250 mg/ml, suggests repeated exposure and contamination of the lakes. Microbial growth in the presence of varying concentrations of the pesticides, namely, emamectin benzoate, thiamethoxam, quinalphos, deltamethrin, spiromesifen, flubendiamide, monocrotophos, fipronil, fenazaquin and phorate, was tested. Results showed resistance to all pesticides except fenazaquin and fipronil, up to 250 mg/ml. For the latter two, tolerance was displayed up to a concentration of 40 mg/ml. Tolerance may potentially result from the transport and deposition of pesticides from nearby locations, particularly the tea plantations of Darjeeling and Eastern Nepal. This may create great ecological risks as these lakes are an important water source for endemic wildlife of this protected area. They also hold great significance to the religious sentiment of the local tribes who worship these lakes as sacred. The study highlights the need for monitoring pesticide contamination in such pristine high-altitude environments and the mechanisms of long-range pollutant transport.

Assessing the fate, toxicity, and ecological risk of mixtures of di(2-ethylhexyl)phthalate and di-n-butylphthalate using aquatic and terrestrial microcosms.

Di(2-ethylhexyl)phthalate (DEHP) and di-n-butylphthalate (DBP) frequently coexist in different environmental compartments. Thus, in this study, model aquatic and terrestrial microcosms were prepared to analyze the combined effect of DEHP and DBP on their fate, toxicity, and ecological risk. In the aquatic microcosms, with the addition of the same amount of DEHP and DBP, a higher total amount of DEHP was detected in water, suspended particles, and sediment than DBP due to the higher Kow and half-life of DEHP than DBP. Sediment was the major sink of both phthalates, as the highest percentages of DEHP (90.0 % âˆ¼ 95.6 %) and DBP (68.7 % âˆ¼ 78.1 %) were found in the sediment. The results of the whole sediment toxicity test showed that DBP (LC50/LC10: 6.75/1.171 µg/g dw) was more toxic than DEHP (LC50/LC10: 158.75/27.25 µg/g dw) to the tubificid oligochaete Monopylephorus limosus, with a synergistic toxic effect of the mixture of DEHP and DBP (LC50/LC10: 100.3/4.6 µg/g dw). The mobility of DEHP and DBP in soil was low during irrigation, with the release of 0.054 % âˆ¼ 2.29 % DEHP and 0.097 % âˆ¼ 1.86 % DBP. The bioconcentration factors/biota-sediment accumulation factors for DEHP (70.8-145 L/kg/0.093-0.359) in the muscle of the fish Carassius auratus were lower than those for DBP (82.2-300 L/kg/0.514-1.625). The bioaccumulation factors of DEHP and DBP for earthworms were 0.373 and 0.682, respectively. The levels of DEHP and DBP in the water and sediment of aquatic systems and in the soil of terrestrial systems might pose high ecological risks to some fish species, M. limosus and earthworms, according to the risk quotient values. These data provide valuable insights for the development of government control strategies to minimize the ecological risks of DEHP and DBP.

Responses of soil antibiotic resistance genes to the decrease in grain size of sediment discharged into Dongting Lake, China.

Sediment or soil in wetlands is regarded as an important sink of antibiotic resistance genes (ARGs). However, there are no studies on the effects of sediment changes (which caused changes in soil texture) on soil ARGs in wetland. Here, we collected topsoil samples from 12 study sites that were deposited in early (prior to the 1970s) or recent years to reveal the responses of soil ARGs to the decrease in grain size of sediment discharged into Dongting Lake. The results indicated that it caused significant increases in clay content, soil organic matter (SOM), moisture, and bacterial abundance. The absolute abundance of 38 % ARG subtypes, 62 % ARG types, and the total ARG concentrations showed a significant increase. The composition of ARG profiles also showed significant changes. For mobile genetic elements (MGEs), the levels of plasmid, insertional, and transposase were significantly elevated. Notably, clay content, moisture, SOM, and bacterial abundance presented very strong positive correlation with most ARG and total ARG abundance. The contributions of physicochemical characteristics and bacterial abundance to ARG variations were ranked as follows: 16S rRNA > SOM > moisture > pH > soil texture (clay, sand and silt) > nitrate nitrogen > ammonium nitrogen. Bacterial abundance, SOM, moisture, and soil texture were the primary environmental parameters contributing to the soil ARG variations in this research. These changes of ARGs may pose risks to ecosystems and public health.

Dynamics of sediment-associated nitrogen export from intermittent streams in subtropical forests of southeast China.

The significance of intermittent streams in nutrient loss within forest ecosystems is becoming increasingly critical due to changes in precipitation patterns associated with global climate change. However, few studies have focused on nutrient export from intermittent streams. We conducted continuous sediment collection from intermittent streams from March 2022 to February 2023 to investigate the export pattern and mechanism of sediment-associated nitrogen (N) from intermittent streams of different forest types (composed forest of Castanopsis carlesii (Cas. carlesii) and Cunninghamia lanceolata (C. lanceolata) forests, compared to Cas. carlesii forests). We measured the N concentrations and calculated the export amounts of four common forms of N associated with sediments: total N (TN), dissolved N (DN), nitrate, and ammonia. Our results showed that (1) the annual average exports of TN, DN, nitrate, and ammonia associated with sediments from intermittent streams from both forest types were 273, 1.62, 0.26, and 0.84 kg ha-1, respectively; (2) N export was significantly higher in composite forests of Cas. carlesii and C. lanceolata, compared to Cas. carlesii forests; (3) stream sediment export amount positively affected N export both in composite forests and Cas. carlesii forests; and (4) N export was also controlled by rainfall amount and stream characteristics. Our study quantified sediment-associated N export from intermittent streams among different subtropical forest types, which will enhance our understanding of N dynamics associated with stream hydrological processes in subtropical forests.

Two-year assessment of the effects of controlled sediment flushing on stream habitats and biota at reach scale.

Controlled sediment flushing operations (CSFOs) allow to recover reservoirs storage loss while rebalancing the sediment flux interrupted by dams but, at the same time, may cause unacceptable ecological impact. In this study, we investigated the responses of the food web of an upland stream to a CSFO, focusing on the effects of fine sediment deposition detected in three different mesohabitats, i.e., a pool, a riffle, and a step-pool. The field campaign lasted two years and included repeated measurements of fine sediment deposits, and sampling of periphyton, benthic macroinvertebrates and fishes. A moderate and patchy deposition occurred due to the CSFO with short and medium-term ecological impact on the lower trophic levels of the food web, which may affect the whole ecosystem functioning. The monitoring of all available mesohabitats in the investigated stream allowed to detect variations in the ecological response to CSFO, providing a more adequate assessment of the impact. As expected, sedimentation was larger in the pool but, in contrast to our hypotheses, the impact was lower and the recovery was longer for the benthic organisms inhabiting the riffle. In the case of fishes, no lethal impact of both brown trout and bullhead was recorded in the short term but the occurrence of longer lasting effects could not be excluded. To date, this is one of the few studies dealing with a detailed integrative assessment of the downstream impact of sediment management from reservoir on both abiotic and biotic components of stream ecosystem.

Microalgae realizes self N-doped biochar for heavy metal polluted sediment remediation.

Heavy metal contamination in sediment has become a significant global environmental challenge. Numerous studies have demonstrated the effectiveness of modified biochar to solve heavy metal contamination in sediment. However, the modification process with complex methods and expensive modifiers prevented its large-scale application. In this study, an N self-doped biochar was obtained by pyrolysis of Spirulina sp. (SBC). Meanwhile, the K2CO3 impregnation method was utilized to prepare Spirulina sp. biochar (KSBC), which demonstrated a higher specific surface area (874 m2/g) and richer O, N functional groups. The adsorption capacity of KSBC550-120 for Cu (Ⅱ), Zn (Ⅱ), and Cd (Ⅱ) was 57.9 ± 0.3 mg/g, 43.6 ± 0.7 mg/g, and 63.9 ± 0.6 mg/g, respectively. The adsorption process is primarily governed by chemical processes, mainly through ion exchange, surface complexation, dissolution-precipitation, electrostatic interactions, adsorption-reduction, and cation-π interactions. Moreover, utilizing KSBC550-120 for mixing or capping effectively reduced heavy metal concentrations in both the overlying and pore water of the sediments. 1.0 wt% KSBC550-120 with capping treatment significantly reduced the release of heavy metals from the sediment by 80.3-91.9%. This study provides effective theoretical support for re-utilizing waste algal residues and remediation of the heavy metal-contaminated river and lake sediments using microalgae biochar.

Distribution and Fate of Polyethylene Microplastics Released by a Portable Toilet Manufacturer into a Freshwater Wetland and Lake.

A portable toilet manufacturer in northwest Indiana (USA) released polyethylene microplastic (MP) pollution into a protected wetland for at least three years. To assess the loads, movement, and fate of the MPs in the wetland from this point source, water and sediment samples were collected in the fall and spring of 2021-2023. Additional samples, including sediment cores and atmospheric particulates, were collected during the summer of 2023 from select areas of the wetland. The MPs were isolated from the field samples using density separation, filtration, and chemical oxidation. Infrared and Raman spectroscopy analyses identified the MPs as polyethylene, which were quantified visually using a stereomicroscope. The numbers of MPs in 100 mL of the marsh water closest to the source ranged from several hundred to over 400,000, while the open water samples contained few microplastics. Marsh surface sediments were highly contaminated with MPs, up to 18,800 per 30.0 g dry mass (dm), compared to core samples in the lower depths (>15 cm) that contained only smaller MPs (<200 µm), numbering 0-480 per 30.0 g (dm). The wide variations in loads of MP contaminants indicate the influence of numerous factors, such as proximity to the point source pollution, weather conditions, natural matter, and pollution sinks, namely sediment deposition. As proof of concept, we demonstrated a novel remediation method using these real-world samples to effectively agglomerate and remove MPs from contaminated waters.

Cadmium contamination in sediments from a mangrove wetland: Insights from lead isotopes.

Cadmium (Cd) pollution has gained significant attention in mangrove sediments due to its high toxicity and mobility. However, the sources of Cd and the factors influencing its accumulation in these sediments have remained elusive. In this study, we utilized lead (Pb) isotopic signatures for the first time to assess Cd contamination in mangrove sediments from the northern region of the Beibu Gulf. A strong correlation was observed between Cd and Pb concentrations in the mangrove sediments, suggesting a shared source that can be estimated using Pb isotopic signatures. By employing a Bayesian mixing model, we determined that 70.1 ± 8.2 % of Cd originated from natural sources, while 12.9 ± 4.9 %, 9.8 ± 3.7 %, and 7.1 ± 3.4 % were attributed to agricultural activities, non-ferrous metal smelting, and coal combustion, respectively. Our study clearly suggests that natural Cd could also dominate the high Cd content. Agricultural activities were the most important anthropogenic Cd sources, and the increased anthropogenic Cd accumulation in mangrove sediment was related to organic matter. This study introduces a novel approach for assessing Cd contamination in mangrove sediment, providing useful insights into Cd pollution in coastal wetlands.

Anthropogenic and climatic impacts on historic sediment, carbon, and phosphorus accumulation rates using 210Pbex and 137Cs in a sub-watershed linked to Zarivar Lake, Iran.

To estimate a watershed's response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m-2 year-1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m-2 year-1 respectively. During this period, the watershed underwent extensive deforestation (12%) on steep slopes, coinciding with higher mean annual precipitations (more than double). Conversely, after 2009, when check dams were installed in the sub-watershed, the sediment load to the lake became negligible. The results of this research indicate that anthropogenic activities had a pronounced effect on MAR, OCAR, and PPAR, causing them to fluctuate from negligible amounts to values twice the averages over the last century, amplified by climatic factors. These results imply that implementing climate-smart watershed management strategies, such as constructing additional check dams and terraces, reinforcing restrictions on deforestation, and minimum tillage practices, can facilitate protection of lacustrine ecosystems under accelerating climate change conditions.

Blending census and paleolimnological data allows for tracking the establishment and growth of a major gannet colony over several centuries.

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary's (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony's historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony's establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony's dynamics and inform conservation efforts.

Contamination of toxic elements in the sediments, water, and igneous rocks of the Sefid-rud River in Northern Iran using contamination indicators, with a specific focus on Ti-rich coastal sediments.

The Sefid-rud River is a significant river on the southern coast of the Caspian Sea in Iran. In this study, we collected 28 samples of surface sediments and water to assess the level of metal contamination. Chemical analysis revealed that the average concentrations of heavy metals in both sediments and water increase from upstream to downstream. There is no clear significant relationship observed between changes in the values of investigated elements in sediments and water. The levels of these elements in the sediments, exceed toxic response thresholds. In the water samples, As, Ni and V concentrations exceed the WHO standard values. According to the Igeo, EF and PLI indices, the sediments at most stations are not contaminated by any of the elements. The CF and Dc indices suggest low contamination levels at all stations. The NIPI and ecological risk indices (Er and RI) indicate non-polluted conditions at all stations except SF22, SF20, SF11, and SF6. The MI and HEI indices indicate pollution in all water samples of the Sefid-rud, but critical values are only observed at SF5 and SF15. The other stations show no contamination. The Cf index indicates high pollution levels for all elements except Cu, Zn, and Pb. The upstream area poses a relatively high and considerable ecological risk according to the PERI index. In conclusion, the sediments of the Sefid-rud River have a higher potential for the exchange of toxic substances compared to the aquatic environment.