Search Results (113)

Deposit-feeding aquatic oligochaete worms are abundant and widely distributed benthic animals in lakes that affect the nutrient cycling between sediments and the water and thus the water quality. This effect can be density-dependent and affected by the presence of filter-feeding bivalves, which can modulate the worms’ impact. We conducted a mesocosm experiment with high, medium, and low densities of the tubificid worms Limnodrilus hoffmeisteri (Oligocheata, Tubificida, and Naididae) in the presence of the filter-feeding bivalve Hyriopsis cumingii. In the low-density treatment, the concentrations of nitrate nitrogen (NO₃⁻-N), ammonium nitrogen (NH₄⁺-N), and organic suspended solids (OSSs) increased moderately compared with the control. In the medium- and high-density treatments, there were also increases in total nitrogen (TN), total phosphorus (TP), soluble reactive phosphorus (SRP), total suspended solid (TSS) and inorganic suspended solid (ISS) concentrations. Moreover, the biomass of phytoplankton (Chl a), the light attenuation coefficients, and the abundance of both cladoceran and rotifer zooplankton rose with increasing worm densities. Water quality deteriorated in both the medium and high worm density treatments, likely due to increased nutrient leading to an increase in the biomass of phytoplankton in our mesocosms, even though plankton-consuming bivalves were present. Thus, during the restoration of eutrophic shallow lakes with a high density of worms, more bivalves are needed to compensate for the negative impact of worms on water quality. Full article

To investigate the influence of bioturbating organisms on the migration and degradation of chlorophenols in freshwater sediments, simulated experimental systems were established, with tubificid worms employed as the model bioturbator and 2,4,6-trichlorophenol (TCP) as a representative chlorophenol contaminant. The results showed that tubificid worms significantly promoted the removal of TCP in sediments, with this effect mainly concentrated in the surface sediment layer (0–2 cm) and limited impact on deeper sediment layers (2–6 cm). The removal efficiency was higher in the low-concentration TCP group than in the high-concentration group. TCP in the overlying water was predominantly in the dissolved phase, and the presence of tubificid worms reduced the TCP concentration in the aqueous phase, resulting in a greater amount of removal. The bioturbation of tubificid worms altered the physicochemical characteristics of the system, increasing the turbidity of the overlying water, decreasing its pH, elevating the redox potential across different sediment depths, and improving the organic matter conditions. Tubificid worms also modified the bacterial community structure in both the overlying water and the sediment. The core mechanism by which tubificid worms accelerate TCP removal is through promoting the migration of TCP from the sediment to the overlying water, while concurrently regulating the bacterial community structure in the overlying water to enhance the degradation capacity of chlorophenols in this layer. This highlights the important role of bioturbators in aquatic ecosystems, and ignoring their presence may lead to an erroneous underestimation of the system’s self-purification capacity. Full article

Bioturbating animals move around large amounts of sediment, changing its physicochemical properties and biogeochemical processes. The present study assessed the role of the ghost shrimp Lepidophthalmus louisianensis, a major coastal bioturbator in the Northern Gulf of Mexico, in the fate of crude oil after the 2010 Deepwater Horizon blowout. Experiments were conducted in greenhouse mesocosms, with or without ghost shrimp and with or without added oil, reflecting mild surface or subsurface oiling in a beach environment. To evaluate the hydrocarbon-degradation potential of the sediment microbial community, a respirometric radiotracer assay was conducted with ¹⁴C naphthalene as a model polycyclic aromatic hydrocarbon (PAH) compound. Oil augmentation led to a substantial increase in the PAH degradation potential of mesocosm sediments, which was further enhanced by the presence of the bioturbator. However, bioturbation alone, without previous oil exposure, did not enhance naphthalene degradation. 16S rRNA gene analyses showed that there were no significant changes in the microbial community composition associated with either bioturbation, oil augmentation, or both. This study demonstrated bioturbation- and oil-exposure-related enhancement in hydrocarbon degradation in mildly oiled sediment, and indicated that this may be due to an increased expression of PAH degrading activities in the preexisting community of hydrocarbon-degrading bacteria rather than resulting from a shift in the microbial community composition. Full article

The Pantanos de Villa wetland, a protected Ramsar site in Lima, Peru, faces significant pressure from invasive species and urban pollution. This study provides a comprehensive evaluation of microhabitat use and trace-element bioaccumulation in the invasive crayfish Procambarus clarkii (Girard, 1852). We analyzed the physicochemical parameters of the microhabitat and measured the concentrations of macroelements (Na, Mg, P), trace metals (Cu, Zn, Al, Ni, Ti, Pb), and a metalloid (B) in water, sediment, and crayfish tissues (gill, hepatopancreas, and muscle) using ICP-OES. Additionally, we examined the growth pattern of P. clarkii through its length–weight relationships. A total of 171 individuals were recorded: 99 males and 72 females. Males were longer (13–15 cm), while females were heavier (18–21 g). Additionally, a positive correlation was observed in females between the size and weight of the hepatopancreas and abdominal muscle, whereas no significant link was found in males. Sediments had higher levels of the evaluated chemical elements, with Cu (28.26 mg kg⁻¹) and Zn (66.88 mg kg⁻¹) exceeding international quality guidelines, indicating a possible ecotoxicological risk. The significant negative correlation between dissolved oxygen and the abundance of P. clarkii suggests that higher D.O. is associated with less bioturbation and more predators, making the microhabitat less suitable for juveniles. We conclude that P. clarkii serves as an essential bioindicator and potential vector for the relocation of the trace in an urban wetland, highlighting the need for integrated management strategies to reduce the ecological impacts of this invasive species. Full article

The family Capitellidae performs critical roles in bioturbation and sediment remediation within global marine benthic ecosystems. However, they are a taxonomically challenging group due to their simple morphology and a ‘morphological mosaic’, where traditional classificatory traits, such as thoracic chaetiger counts, appear convergently across genera. Previous multi-locus studies (using 18S, 28S, H3, and COI) first highlighted this conflict, revealing the polyphyly of major genera like Notomastus and even Leiochrides itself (based on unidentified specimens). More recently, mitogenomic studies uncovered massive gene order rearrangements and a conflicting topology but did not include Leiochrides. Critically, with no complete mitogenome reported for a formally identified Leiochrides species, its true phylogenetic position and the validity of its polyphyly remain unresolved. To address this critical gap, we sequenced and characterized the first complete mitochondrial genome from a formally identified species, Leiochrides yokjidoensis, recently described from Korean waters. The complete mitogenome was 17,933 bp in length and included the typical 13 protein-coding genes (PCGs), 2 ribosomal RNAs (rRNAs), and 22 transfer RNAs (tRNAs). Gene order (GO) analysis revealed the occurrence of gene rearrangements in Capitellidae and in its sister clade, Opheliidae. A phylogenomic analysis using the amino acid sequences of 13 PCGs from 30 species established the first robust systematic position for the genus Leiochrides (based on this formally identified species). Phylogenetic results recovered Leiochrides as a sister group to the clade comprising Mediomastus, Barantolla, Heteromastus, and Notomastus hemipodus (BS 99%). This distinct placement confirms that Leiochrides represents an independent evolutionary lineage, phylogenetically separate from the polyphyletic Notomastus complex, despite their morphological similarities. Furthermore, our analysis confirmed the polyphyly of Notomastus, with N. hemipodus clustering distinctly from other Notomastus species. Additionally, signatures of positive selection were detected in ND4, and ND5 genes, suggesting potential adaptive evolution to the subtidal environment. This placement provides a critical, high-confidence anchor point for the genus Leiochrides. It provides a reliable reference to investigate the unresolved polyphyly suggested by previous multi-locus studies and provides compelling evidence for the hypothesis that thoracic chaetiger counts are of limited value for inferring phylogenetic relationships. This study provides the foundational genomic cornerstone for Leiochrides, representing an essential first step toward resolving the systematics of this taxonomically challenging family. Full article

Holothuroids play a vital role in nutrient cycling and bioturbation to enhance the marine ecosystem. They enhance the biodiversity for various symbiotic marine organisms by providing essential shelter and spawning grounds. This review focuses on the Class Holothuroidea (Phylum Echinodermata) in Indian waters, encompassing a total of 187 species organized into 7 orders and 21 families. Notably, the order Holothuriida represents the largest proportion of species, accounting for 27%. These species are well-distributed across India, with the Andaman and Nicobar Islands exhibiting the highest level of species richness (107 species), followed by the East Coast (102 species), Lakshadweep (39 species), and the West Coast (34 species). Species diversity was assessed using the Shannon–Weiner diversity index. Results indicate that the Andaman and Nicobar Islands (H’ = 2.23) and the West Coast (H’ = 2.14) demonstrate the highest levels of diversity. This review provides a comprehensive and precise inventory of all species of Holothuroidea reported in Indian waters, which is provided to facilitate understanding of the reported species, their systematics, and distribution. In addition, a significant insight for both conservation and management of sea cucumbers in India has also been provided. Full article

Rice–fishery integrated farming has expanded rapidly in China, yet its implications for arsenic (As) accumulation remain insufficiently understood. This study evaluated As bioavailability and enrichment in a rice–crayfish farming system (RCFS) by establishing controlled field plots with soil As concentrations ranging from 5 to 40 mg/kg under three water-management regimes: alternating wetting and drying (AWD), continuously flooded (CF), and RCFS. Soil–water physicochemical variables and As accumulation in both rice organs and crayfish tissues were systematically analyzed, followed by human health risk assessment. Inorganic As in brown rice increased linearly with soil As, following Y = 0.0117X + 0.0598 (R² = 0.96), and the estimated soil safety thresholds were 26.48 mg/kg for AWD, 11.98 mg/kg for RCFS, and 9.24 mg/kg for CF. AWD consistently exhibited the lowest As risk due to its ability to elevate soil Eh and maintain a more favorable pH, thereby suppressing As mobilization. Compared with CF, RCFS reduced As bioavailability through crayfish-induced bioturbation, which increased Eh, enhanced SOM and CEC, and improved soil aeration. As accumulation in crayfish tissues also rose with soil As, with abdominal muscle As fitting Y = 0.0085X + 0.0553 (R² = 0.8588). Although abdominal muscle met safety limits, the hepatopancreas accumulated substantially higher As and exceeded carcinogenic risk thresholds, even at 5 mg/kg of soil As, indicating a potential health concern for consumers. This work elucidates As dynamics and enrichment mechanisms in RCFS, providing guidance for safer rice–crayfish production in As-impacted areas. Full article

This study reports the discovery of a newly identified phosphorite deposit in the Al-Tafeh area of northern Jordan. Geological fieldwork investigated three outcrops and one comparison site in the Russifa area. Geochemical analyses reveal a high P₂O₅ content (average 24.32 wt.%), strongly correlating with CaO. There are also significant levels of trace elements, including uranium (0.045 mg/g), cadmium (0.025 mg/g), and zinc (0.099 mg/g). Mineralogical investigation reveals that francolite is the main phosphate mineral. Calcite and quartz are also present. Petrographic analysis reveals the presence of pellets, skeletal fragments, coated grains, and indicators of storm deposits, bioturbation, and fossil-rich layers. These findings indicate that the Al-Tafeh area in northern Jordan is an important yet under-explored area for phosphorite, suggesting that this discovery could have significant economic value. Full article

Dolostone is an important reservoir for hydrocarbons, and significant hydrocarbons have been produced in the Middle Permian Qixia Formation dolostone reservoirs in the southeastern Sichuan Basin. The origin and formation process of the dolomite reservoir in the research area are studied through thin-section, geochemical, and sedimentary cycle analyses and U-Pb geochronology. Three types of dolomites were identified, including stratiform fine-crystalline dolomite (D1), patchy fine-crystalline dolomite (D2), and saddle dolomite cement (SD). D1 and D2 exhibit a range of δ¹³C values from 3.39‰ to 4.21‰ and a range of δ¹⁸O values from −6.06‰ to −5.75‰, indicating a mild depletion of δ¹⁸O relative to coeval seawater while maintaining seawater-equivalent δ¹³C signatures. Their ⁸⁷Sr/⁸⁶Sr ratios and REE patterns indicate seawater-derived fluids for D1 and D2 (both test results showed a U-Pb age of ≈274 Ma) and hydrothermal origin for SD. Sedimentary cycle analysis found that the regression process in the fourth-order sequence is conducive to the formation of dolomite under the background of regression in the third-order sequence. Exposure of bioclastic shoals enabled evaporated seawater reflux, forming penecontemporaneous D1 in fluid-saturated settings. Selective dolomitization occurred in the bioturbation structure with good porosity and permeability, forming D2. In the burial stage, the hydrothermal fluid had a slight transformation on the dolomite and formed SD. This model highlights transgressive–regressive cycle controls on reservoir development, providing exploration criteria for analogous carbonate systems. Full article

An experimental study was conducted in the laboratory to investigate the interactive effects of fish and algae on growth patterns and water quality. Body length and body weight of Carassius carassius, Microcystis aeruginosa (M. aeruginosa) density, and concentrations of nutrients were monitored continuously over a period of 92 days. It was noted that fish growth was significantly higher in the absence of M. aeruginosa compared to its presence (p < 0.05). This can be partly attributed to toxin production by M. aeruginosa. The densities and growth rates of M. aeruginosa in groups with Carassius carassius were significantly higher than those in fishless groups (p < 0.05), and this was attributable to fish metabolism and bioturbation, which led to a considerable increase in ammonia and total dissolved nitrogen concentrations, as well as a significant impact on proportions of nutrients. The growth rate of Carassius carassius firstly increased and then decreased with increasing M. aeruginosa densities, and a quantitative relationship was established using the Gompertz equation and Logistic equation (R² = 0.914–0.955). Based on the above results, we concluded that interactions between fish and algae are greatly related to their consequences on water qualities, by employing equations, a more detailed interpretation of the processes occurring in the fish–algae system can be achieved. Full article

This study quantified nitrogen (N) inputs by water, feed, animals, and atmospheric gas and outputs by water, harvested animals, sediments, and gas emissions in earthen ponds used for the monoculture and integrated cultures of yellow-tail lambari (Astyanax lacustris), Amazon River prawn (Macrobrachium amazonicum), and curimbata (Prochilodus lineatus), and evaluated whether epibenthic species improve N retention in harvested biomass. Three systems with four replicates were tested, lambari monoculture (L), lambari–prawn (LP), and lambari–prawn–curimbata (LPC), stocked at 50, 25, and 13 individuals m⁻², respectively. Feed N was the major input (67–75%), followed by inlet water (19–30%). Harvested biomass represented 20–23% of total outputs, sediments 25–33%, and gaseous emissions 7–29%, while outlet water contributed <3%. N lost through seepage was highest in L (70.5 ± 22.9 kg N ha⁻¹). N₂ ebullition increased with benthic species, from 10.4 ± 10.6 kg N ha⁻¹ (L) to 72.1 ± 32.4 kg N ha⁻¹ (LPC). N recovered in lambari was 43.2 ± 7.4 kg N ha⁻¹ in LPC, 36 ± 8.6 in L, and 33 ± 5.6 in LP. Considering all species, recovery of dietary N increased from 20.0 ± 4.3% (L) to 35.0 ± 5.9% (LPC), and recovery from all inputs rose from 13.0 ± 2.2% to 18.0 ± 3.4%. Integrated systems, particularly LPC, enhanced N retention in biomass and reduced environmental losses. Full article

Understanding how disturbances affect marine foundation species is critical for enhancing the success of coastal ecosystem restoration. Extreme bioturbation by burrowing animals is increasingly impacting coastal vegetated habitats worldwide, with the potential to undermine the persistence and resilience of key foundation species. However, the role of faunal disturbances in modulating restoration outcomes remains poorly understood. Here, we combine field surveys and manipulative field experiments to examine how mud shrimp (Upogebia major) bioturbation impacts vegetation dynamics and restoration outcomes for intertidal seagrass (Zostera japonica). Field surveys revealed pronounced seasonal variation in shrimp bioturbation intensity, with peak burrow densities occurring in fall (up to 400 burrows m⁻²; 289% higher than in spring). The intensified bioturbation was associated with significant declines in seagrass shoot cover, density, and biomass, with negative associations restricted to fall. To test whether seasonally intensified shrimp bioturbation impairs seagrass restoration, we conducted a 24-day field experiment transplanting seagrass patches of varying initial sizes (5–26 cm diameter) into plots representing three levels of shrimp burrow density observed during the fall peak: control (~9 burrows m⁻²), high (~280 burrows m⁻²), and extremely high (~455 burrows m⁻²). Compared to the control, high and extremely high burrow treatments exhibited accelerated patch losses. By day 24, vegetation was virtually eliminated in all shrimp treatments, but the rate of patch loss was significantly lower in larger patches. These results suggest that seasonal intensification of mud shrimp bioturbation has a potential to compromise intertidal seagrass restoration, while increasing planting scale offers a potential mitigation strategy. Restoration interventions should explicitly consider temporal patterns in faunal bioturbation and integration of positive interactions to improve long-term success of vegetation restoration in bioturbator-dominated coastal systems. Full article

Red sandstones of the Cambrian age are globally distributed and represent an important sedimentation phase during this critical time interval. Their sedimentology and geochemistry can provide key information about the sedimentation style, paleoclimatic conditions, and weathering trends during the Cambrian. In the Salt Range of Pakistan, the Khewra Sandstone constitutes the Lower Cambrian strata and consists of red–maroon sandstones with minor siltstone and shale in the basal part. Cross-bedding, graded bedding, ripple marks, parallel laminations, load casts, ball and pillows, desiccation cracks, and bioturbation are the common sedimentary features of the formation. The sandstones are fine to medium to coarse-grained with subangular to subrounded morphology and display an overall coarsening upward trend. Petrographic analysis indicates that the sandstones are sub-arkose and sub-lithic arenites, and dolomite and calcite are common cementing materials. X-ray Diffraction (XRD) analysis indicates that the main minerals in the formation are quartz, feldspars, kaolinite, illite, mica, hematite, dolomite, and calcite. Geochemical analysis indicates that SiO₂ is the major component at a range of 53.3 to 88% (averaging 70.4%), Al₂O₃ ranges from 3.1 to 19.2% (averaging 9.2%), CaO ranges from 0.4 to 25.3% (averaging 7.4%), K₂O ranges from 1.2 to 7.4% (averaging 4.8%), MgO ranges from 0.2 to 7.4% (averaging 3.5%), and Na₂O ranges from 0.1 to 0.9% (averaging 0.4%), respectively. The results of the combined proxies indicate that the sedimentation occurred in fluvial–deltaic settings under overall arid to semi-arid paleoclimatic conditions with poor to moderate chemical weathering. The Khewra Sandstone represents the red Cambrian sandstones on the NW Indian Plate margin of Gondwana and can be correlated with contemporaneous red sandstones in the USA, Europe, Africa, Iran, and Turkey (Türkiye). Full article

The water level of Lake Neuchâtel (Switzerland) was lowered 150 years ago, initiating soil formation and colonization by riparian forests of the previously submerged areas. Although the soils of the whole area are young and have probably quite similar parent material (lacustrine sediments and moraine), the present soils show a large diversity of horizon structures and contents. The aim of this study is to describe the respective processes of accumulation, integration, and stabilization of organic matter and assess the soil variables influenced by these processes in the various types of riparian forests with different moisture levels. The investigation employed a semi-quantitative, holistic approach that combined field observations, laboratory analyses, and micromorphological examination of soil thin sections. The results indicate that the accumulation and stabilization of organic matter are primarily governed by physicochemical factors associated with the parent material, particularly soil texture and calcium cation saturation. Soil moisture and groundwater elevation were found to mainly influence biological activity and vegetation types. Additionally, the incorporation of organic matter is affected by both soil texture and bioturbation processes. Overall, this study underscores the complexity of the mechanisms regulating organic matter dynamics in young soils. Full article

Small terrestrial mammals (STMs) are vital components of forest ecosystems. They serve as seed dispersers, herbivores, prey, and vectors of pathogens. The STM community structure responds dynamically to forest composition, disturbance, and management regimes. However, despite their central ecological functions and frequent occurrence, STMs remain underestimated. This narrative review aims to comprehensively synthesize existing literature on the reciprocal interactions between STMs, temperate and boreal ecosystems, and forest management. Specifically, we (1) define a group of STMs and their specificities; (2) discuss the influence of forest structure, disturbance, and management on STM populations; and (3) analyze the known direct and indirect effects of STMs on forest ecosystems and forestry. Full article