Accumulation Of Detritus Research Articles

Analysis of organic matter stock dynamics in arable soils of Yamal: simulation experiments with the ROMUL model

The goal of this work is to analyze the dynamics of soil organic matter (SOM) in arable soils of Yamal using computational experiments with the ROMUL model. Soil temperature and moisture dynamics were simulated using the SCLISS model. The Yamal experimental station was organized in 1932. The soil is Plaggic Podzol. The thickness of humus horizon (PY) is 30 cm. Pools, kg/m2: SOM – 9.32 and 13.75; N – 0.46 and 0.66 for 0–20 and 0–30 cm respectively. Background: soddy-green-moss tundra near Salekhard. Soil: Folic Podzol: litter (O, 2 cm) and humus-accumulative (AY, 4 cm) and illuvial ferruginous (BF, 6 cm) horizons. Pools, kg/m2: SOM – 1.38 and 2.69, N – 0.03 and 0.18 for 0–2 and 2–6 cm respectively. The quantity and quality of background fall was estimated according to literature data. Clarification of the amount of fall was carried out by the method of inverse problem solving (spin-up). Peat application was simulated: starting application in the dose of 12 kg/m2 and maintenance (every 6 years) in doses 4, 8 and 12 kg/m2, N 1%. Application of mineral fertilizers, 2 variants: a) N 4 g/m2 (40 kg/ha) in peatting years and b) application of the same dose of nitrogen every year. The duration of computational experiments is 30 and 90 years. Computational experiments showed that after the starting peatting of Folic Podzol at the rate of 12 kg/m2 after 30 years, only 15% of the applied detritus remained. Maintenance peatting of 8–12 kg/m2 leads to an increase in SOM pool to 20–30 kg/m2 and excessive accumulation of detritus. Application of 4 kg/m2 of peat once every 6 years for 90 years shows the dynamics of SOM pools from Folic Podzol to Plaggic Podzol which is confirmed by field survey data. Application of mineral nitrogen (4 g/m2) once every 6 years does not affect SOM pools. Annual application of mineral N (4 g/m2) increases SOM pools due to intensified humification. This fact requires experimental verification.

Diversity of nematodes associated with Heterodermia diademata: A case study in the Eco Área of Avellaneda, Buenos Aires, Argentina

Lichens represent a complex life form characterized by a symbiotic partnership between at least two organisms: a fungus and an alga. In this unique relationship, the fungus offers a protective habitat for the alga, which, in turn, harnesses energy from sunshine, water and air to provide sustenance for the fungus. They fulfill ecological roles as a food source for many invertebrates and serve as the basal trophic level for a variety of animals, being considered micro-ecosystems which can host a rich and diverse biota. Nematodes are among the most widespread and abundant of all metazoans, inhabit moist interstitial environments in all habitats and are abundant in marine and freshwater benthic habitats and in the soil. They were also reported from accumulations of detritus in leaf axils, in the angles of tree branches and in mosses and lichens. In this case study, the trophic role and diversity of free-living nematodes associated with lichens were examined in an area of Buenos Aires province, Argentina, revealing seven genera of nematodes linked to Heterodermia diademata, representing all trophic levels of free-living nematodes: bacteriophages (Plectus and Acrobeles), fungivores (Aphelenchus), herbivores (Helicotylenchus), omnivores (Eudorylaimus and Mesodorylaimus) and a predator (Prionchulus).

Sedimentary characteristics of baer knolls deposits in the volga river delta

Baer knolls (BK) are elongated ridges often close to the sub-latitudinal orientation sometimes spatially isometric that are widespread in the entire Northern Caspian Region up to 0 m a.s.l. (the upper limit of the Late Khvalynian sea transgression). The goal of this study was to establish the genesis of BK based on interpretation of textural and lithologic characteristics of sediments and dating the material composing these landforms. Research has led to the following conclusions that BK have been formed during the transition of Late Khvalynian and Early Holocene time. Sediments of BK consists of three lithofacies (LF1, LF2, LF3). Chocolate clay (CC) and Volga alluvium were significant sources of material for knolls formation. Nonetheless, for lithofacies 1, it was also sandy material lying below the CC. The BK material cannot be attributed to the aeolian genesis because of its lithological, faunal and geochemical characteristics. The knolls formed in brackish subaquatic conditions of the lagoon floor, where a low-energy currents occurred due to the descent of Late Khvalynian basin waters through the Manych Strait. Thus, BK are analogues of river bedforms appearing as the result of turbulent flow, like ripples and river dunes, where, in concordance with the accumulation of sandy material and detritus of redeposited shells, clay particles were deposited under the mixing of the brackish water of the lagoon and the fresh water of the rivers flowing into it.

Macrofauna Community Dynamics and Food Webs in the Canopy-forming Macroalgae and the Associated Detrital Subsidies

Dietary variability and the degradation and incorporation of macroalgae in key macroinvertebrate consumers were examined (1) in a monitoring field study including a natural attached canopy habitat and an adjacent habitat receiving natural accumulations of detritus, and (2) in a manipulative in situ experiment of macroalgal detritus at two different depths (3 and 6 m) in the archipelago of SW Finland. The monitoring field study, examining species-specific dietary responses across three sampling dates in natural macroalgal stands, showed that a pulse of drifting filamentous macroalgae shaped the dietary compositions of the abundant benthic macroinvertebrate consumers and that accumulations of drifting filamentous macroalgae were rapidly incorporated into the food web through epigrazers. The in situ field experiment simulating a natural accumulation event and the degradation process of Fucus vesiculosus during 60 days showed that algal decomposition progressed relatively slowly at both depths. Detectable increasing incorporation of Fucus-derived matter to epigrazers and detritivorous bivalves occurred after 2−3 weeks, while simultaneously the incorporation of filamentous algae decreased over time. Hence, the ecological role of decomposing F. vesiculosus might be more important in areas where the algal matter can accumulate for several months. The effect of depth influenced the food incorporation of typical epigrazers. The increasing depth from 3 to 6 m lowered the median proportion of Fucus-derived matter incorporated into the macrofauna community approximately by 10% points compared to the shallower depth of 3 m.

P270 Otomycosis: Main challenging microbial agent causing otitis externa in northern Iran

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PMObjectivesOtitis externa is one of the most common ear diseases, caused by bacterial and fungal agents. Accumulation of epithelial cells, cellular detritus, waxy substances, and microorganisms in the ear canal provide a proper environment for fungal growth, leading to annoying congestion. In this study, we aimed to identify the fungal causative agents and determine their susceptibility to the antifungal drugs were examined.MethodsAll patients with suspected otitis externa, referred to Amir-al Momenin Referral Centre from October 2020 to November 2021 entered to study. A total of 200 patients’ ear discharge and debris collected samples were examined by direct examination and cultured on SDA supplemented with chloramphenicol. Definitive identification of grown fungi was made by PCR-RFLP and sequencing of ribosomal DNA. In vitro susceptibility testing of the fungal isolates against eleven different antifungal agents was analyzed using the CLSI broth microdilution methods.ResultsA total of 101 (50.5%) cases were confirmed with otomycosis. Most patients were in their fifth decade of life (n = 35, 34.6%), female (n = 57, 56.4%), and had unilateral ear involvement (n = 78, 77.2%). The most common symptoms were earache (56.4%) and itching (51.4%). Most underlying predisposing factors are overaggressive using cotton swabs (65.3%) and history of topical antibiotics (48.5%). Among the 117 fungal isolates, Aspergillus section Nigri was the most common agent 58 (49.57%), followed by Aspergillus section Flavi 19 (16.23%), C. parapsilosis 14(11.96%), Aspergillus section Fumigati 12 (10.25%), C. orthopsilosis 6 (5.12%), C. albicans complex 5 (4.27%), Mucor spp. 2 (1.71%), and Syncephalastrum spp. 1 (0.85%). Mainly, all tested antifungals were active against the most isolates of Aspergillus, aside from tioconazole, nystatin, and terbinafine, which showed low in vitro effects. Also, nystatin and itraconazole showed higher GM MICs in against all Candida species isolates. Conversely, amphotericin B (GM = 0.07129) in Aspergillus and voriconazole (GM = 0.03686) in Candida showed the highest antifungal activity. Regarding ECV values represented by ECOFFs, one of each A. niger (MIC 8 μg/mL), A. flavus (MIC 2 μg/ml), and A. fumigatus (MIC 2 μg/ml) isolates were resistant to itraconazole.ConclusionIn this study, inconsistent with previous ones, fungal agents have overcome bacterial ones as the etiology of otitis externa. This result may relate to misuse or improper use of topical steroids, antibiotics, and inappropriate control of infection. In addition, our sample collection site was an ENT referral center and many patients have been admitted to this center due to treatment failure and suffered from recurrence. Aspergillus section Nigri isolation domination was seen, in agreement with other results. The MICs distribution of Aspergillus species isolates against triazole antifungals are close to ECVs defined by the CLSI and likely outrun it over time. We recommend that physicians request drug susceptibility testing before antibiotic therapy, to prevent the development of resistance.

Summer Dystrophic Criticalities of Non-Tidal Lagoons: The Case Study of a Mediterranean Lagoon

Eutrophication determines algal blooms and the subsequent accumulation of organic matter in sediments, which, in turn, results in the dominance of anaerobic respiratory processes that release toxic gases. Dystrophy is a final dissipative moment that reduces the organic load in the sediment. A case of dystrophy occurring in the Burano lagoon (Tuscany, Italy) in 2021 is reported. The study examined the weather, physico-chemistry of the water, submerged vegetation and sediment labile organic matter. In spring, dissolved oxygen (DO) and pH showed high values, in an abundance of submerged vegetation, while low values had ammonium, nitrate and orthophosphate. In mid-August, as warm and moist sea breezes prevailed, hydrogen sulfide releases were produced, preceded by a sharp rise in ammonium and orthophosphate concentrations, which remained high until November. During dystrophy, DO varied between anoxia and oversaturation, the latter in Cyanobacteria blooms. Dystrophic waters evolved gradually due to microphytes blooms, which changed from Cyanobacteria, in August, to the Dinophyta Alexandrium tamarense, in September, and Bacillariophyta, in November. Sediment labile organic matter varied between 3% and 7%. Ruppia spiralis meadows suffered the total detachment of fronds and stems during the dystrophy and proved to be areas of accumulation of organic detritus, themselves sources of dystrophic phenomena.

Wildfire loss of forest soil C and N: Do pre-fire treatments make a difference?

Losses of C and N from the forest floor and top 20-cm of soil were estimated following separate severe wildfires at two Long-Term Soil Productivity sites in the Sierra Nevada of California, USA. Experimental treatments applied 20 years prior to the wildfires included factorial combinations of 1) organic matter (OM) removal following clear-cut harvesting (SO, stem only harvest, WTH, whole-tree harvest, and WTH + FF, WTH plus the forest floor removal), 2) soil compaction (three levels of intensity), and 3) with and without understory vegetation control. Wildfires caused complete losses of the forest floor in all treatments and also oxidized varying portions of OM in the topsoil. As such, pre-fire forest floor measures were used as an estimate of forest floor C and N loss, and post-fire soil measures of C and N were compared to pre-fire soil data to estimate of mineral soil losses. Averaged over all treatments, the less-productive site that also had lesser accumulations of detritus (Wallace) lost 35.1 Mg C ha−1, or 25 % of its original C stores, while the more-productive site with greater detritus (Rogers) lost 18.4 Mg C ha−1, or 20 % of its original. The SO treatments that left harvest residue on site ended up with much greater losses of C: 36 % versus 15 and 17 % for WTH and WTH + FF, respectively. The SO also yielded the largest losses (25–30 %) of C in the top 10-cm of soil. The other treatments had smaller or inconsistent effects (understory vegetation control) or no effect (soil compaction). Our results suggest that potential benefits from SO by leaving residue on site to soil C and N accumulation can also be readily eliminated by wildfire which commonly occurs at these fire-prone forest ecosystems.

The role of inputs of marine wrack and carrion in sandy-beach ecosystems: a global review.

Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross-ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed 'wrack', on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source ('carrion') for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy-beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land- and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy-beach ecosystems, where microbial decomposers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach-cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi-aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach-cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly mobile scavengers (e.g. foxes, coyotes, raptors, vultures). These consumers become important vectors in transferring marine productivity inland, thereby linking marine and terrestrial ecosystems. Whilst deposits of organic matter on sandy-beach ecosystems underpin a range of ecosystem functions and services, they can be at variance with aesthetic perceptions resulting in widespread activities, such as 'beach cleaning and grooming'. This practice diminishes the energetic base of food webs, intertidal fauna, and biodiversity. Global declines in seagrass beds and kelp forests (linked to global warming) are predicted to cause substantial reductions in the amounts of marine organic matter reaching many beach ecosystems, likely causing flow-on effects for food webs and biodiversity. Similarly, future sea-level rise and increased storm frequency are likely to alter profoundly the physical attributes of beaches, which in turn can change the rates at which beaches retain and process the influxes of wrack and animal carcasses. Conservation of the multi-faceted ecosystem services that sandy beaches provide will increasingly need to encompass a greater societal appreciation and the safeguarding of ecological functions reliant on beach-cast organic matter on innumerable ocean shores worldwide.

Toward a holistic view of orchard ecosystem dynamics: A comprehensive review of the multiple factors governing development or suppression of apple replant disease.

Replant diseases are a common occurrence in perennial cropping systems. In apple, progress toward the development of a universally effective disease management strategy, beyond the use of broad-spectrum soil fumigants, is impeded by inconsistencies in defining replant disease etiology. A preponderance of evidence attributes apple replant disease to plant-induced changes in the soil microbiome including the proliferation of soilborne plant pathogens. Findings from alternative studies suggest that the contribution of abiotic factors, such as the accumulation of phenolic detritus from previous orchard plantings, may play a part as well. Engineering of the resident soil microbiome using resource-based strategies is demonstrating potential to limit activity of replant pathogens and improve productivity in newly established orchards. An understanding of factors promoting the assembly of a disease-suppressive soil microbiome along with consideration of host factors that confer disease tolerance or resistance is imperative to the developing a more holistic view of orchard ecosystem dynamics. Here, we review the literature concerning the transition of orchard soil from a healthy state to a replant disease-conducive state. Included in the scope of this review are studies on the influence of soil type and geography on the apple replant pathogen complex. Furthermore, several tolerance and innate resistance mechanisms that have been described in apple to date, including the role of root chemistry/exudates are discussed. Finally, the interplay between apple rootstock genotype and key resource-based strategies which have been shown to “reshape” the plant holobiont in favor of a more prophylactic or disease-suppressive state is highlighted.

The impact of Early to Middle Bronze Age settlements and farming on vegetation, ecology, nutrient flux and sedimentation at Lake Lucone, northern Italy

In this paper, we describe a 5500-year long core obtained from a lake in the Prealps of northern Italy to investigate the impact of human communities on the lacustrine environment. Specifically, we report micro-botanical proxies (upland and aquatic pollen, algae, cyanobacteria, dung spores, microcharcoal particles), sedimentary parameters (LOI steps, calcimetry, FTIR spectra) and nutrients (P forms, C/N and K) on paired samples in a high-resolution stratigraphy, dated by 14C AMS dating and tie point correlation. Independent archaeological evidence indicates the existence of lakeside settlements and farming in Bronze Age times from c. 4000 to 3300 cal yrs. BP. The impact of this Bronze Age village is recorded by an accumulation of plant detritus, pollen, charcoal and abundant wood and bone-derived ash. Intensive P mineralization by ash production was accompanied by the rapid burial of Pinorg, K, and microcharcoal. Correlated peaks of Porg and pasture plant pollen mark the contribution of animal husbandry to Porg lake sink. The nutrient flux produced by external catchment cropping contrasts with the internal flux discharged by prehistoric dwelling and in turn distinguishes domestic hearth production from a contribution by animal husbandry. Forest conditions and lake sedimentation returned to semi-natural baseline at the end of this 700-year long phase of Early to Middle Bronze Age settlement, but pollen proxies indicate that lake-side forests did not fully recover. Lake Lucone represents a key site, since it documents interactions between bronze Age settlements and related ecological impacts on both terrestrial environment and lacustrine sedimentation, as recorded in a continuous sequence, as well as the end of Bronze Age pile dwelling culture.

3D-Reconstruction of a Giant Posidonia oceanica Beach Wrack (Banquette): Sizing Biomass, Carbon and Nutrient Stocks by Combining Field Data With High-Resolution UAV Photogrammetry

Beach wracks are temporary accumulations of vegetal detritus that can be found along coastlines all over the world. Although beach wracks are often perceived as a nuisance for beach users, they play a crucial ecological role in carbon and nutrient connectivity across ecosystem boundaries, especially when they reach a relevant size, as in the case of the wedge-shaped seagrass accumulations called banquette. In this study, three-dimensional mapping of a giant Posidonia oceanica banquette was carried out for the first time using high-resolution UAV photogrammetry combined with field sampling and compositional and chemical analysis. The combined approach allowed a reliable estimation of the amount and spatial distribution of both vegetal biomass and sedimentary mass, as well as of total carbon, nitrogen and phosphorus content, revealing that i) banquette act as a sediment trap and represent hot spots of seagrass biomass and carbon accumulation; ii) banquette thickness, rather than the distance from the sea, influences the spatial distribution of all variables. Moreover, high-resolution digital elevation models (DEM) revealed discontinuous patterns in detritus accumulation resulting in an unknown banquette type here termed “Multiple Mega-Ridge banquette” (MMR banquette). On the one hand, this study highlighted the high potential of the UAV approach in very accurately 3D mapping and monitoring of these structures, with relevant implications for ecosystem service estimation and coastal zone management. On the other hand, it opened new questions about the role played by temporary beach wracks and, in particular, by P. oceanica banquette in the blue carbon exchange across land-ocean boundaries.

Insights into the farming-season carbon budget of coastal earthen aquaculture ponds in southeastern China

Small-hold aquaculture ponds are widespread globally, but their carbon greenhouse gas emissions are poorly quantified. In this study, we used a carbon budget approach to assess the climate footprint of three earthen aquaculture ponds in southeastern China with the whiteleg shrimp (Litopenaeus vannamei) during the farming period. The main carbon inputs to the ponds were planktonic primary production (58.5–61.8%), followed by commercial feeds (31.9–35.3%), while the major carbon outputs occurred through planktonic respiration (44.0–53.6%) and sedimentation (18.0–21.7%). Water-to-air emissions of carbon greenhouse gases (CO2 and CH4) represented only a small fraction of the carbon flow (0.8–1.6%), with a combined CO2-equivalent emission of 528.4 ± 193.3 mg CO2-eq m−2 h−1 based on GWP20. We also observed significant spatio-temporal variation in carbon greenhouse gases among the three ponds, which could be attributed to the variation in Chl-a and carbon substrate supply. Nevertheless, the magnitude of CH4 emission from these ponds was still higher than some other agro-ecosystems. Moreover, we found that only 21% of the excess organic carbon was converted to shrimp biomass, while another 20% ended up in the sediment. Our findings suggested that lowering the feed conversion ratio and removing the bottom sediments regularly could help improve production efficiency, reduce the excessive accumulation of carbon-rich detritus and minimize the climatic warming impacts of aquaculture production.

Ego network analysis of the trophic structure of an island land bird through 300 years of climate change and invaders.

Ego net analysis is a well‐known practice in social sciences, where an ego net (EN) consists of a focal node, the ego, and its links to other nodes, called alters, and alter–alter links may also be included. An EN describes how a focal node is embedded in its interaction context. Here, I introduce EN analysis to ecology in a study of the trophic network of a sub‐Antarctic land bird, Lesser Sheathbill (Chionis minor). Data originate from the sheathbill population on Marion Island in the Southern Ocean. The bird is ego and its enemies and food are alters. The EN is organized along three dimensions: habitat, interaction type, and time (from before human arrival in 1803 and until a future year 2100). Ten EN descriptors are defined, estimated, and used to track the 300 years of change in sheathbill EN structure. Since 1803, the EN has passed two major, but reversible shifts—seal exploitation in the 19th century and presence of cats from 1949 to 1991. These shifts can be read as structural changes in the sheathbill EN. In the future, a third, perhaps irreversible change is predicted, driven by climate change and a surprising, recent shift to seabird predation by House Mouse, the most detrimental of all extant invaders on Marion. In a warmer and drier future, the mouse will proliferate, and if this forces seabirds to abandon the island, their accumulation of detritus runs dry, starving a rich invertebrate detritivore fauna, which also is a key food source to sheathbills. These detritivores together with plants have also constituted the main food sources of mice. The EN descriptors quantify that story. In the future, these events may lead to a collapse of the island ecosystem, including extinction of the sheathbill—unless plans for mouse eradication are implemented.

Vegetal Undercurrents-Obscured Riverine Dynamics of Plant Debris.

Much attention has been focused on fine‐grained sediments carried as suspended load in rivers due to their potential to transport, disperse, and preserve organic carbon (OC), while the transfer and fate of OC associated with coarser‐grained sediments in fluvial systems have been less extensively studied. Here, sedimentological, geochemical, and biomolecular characteristics of sediments from river depth profiles reveal distinct hydrodynamic behavior for different pools of OC within the Mackenzie River system. Higher radiocarbon (14C) contents, low N/OC ratios, and elevated plant‐derived biomarker loadings suggest a systematic transport of submerged vascular plant debris above the active riverbed in large channels both upstream of and within the delta. Subzero temperatures hinder OC degradation promoting the accumulation and waterlogging of plant detritus within the watershed. Once entrained into a channel, sustained flow strength and buoyancy prevent plant debris from settling and keep it suspended in the water column above the riverbed. Helical flow motions within meandering river segments concentrate lithogenic and organic debris near the inner river bends forming a sediment‐laden plume. Moving offshore, we observe a lack of discrete, particulate OC in continental shelf sediments, suggesting preferential trapping of coarse debris within deltaic and neritic environments. The delivery of waterlogged plant detritus transport and high sediment loads during the spring flood may reduce oxygen exposure times and microbial decomposition, leading to enhanced sequestration of biospheric OC. Undercurrents enriched in coarse, relatively fresh plant fragments appear to be reoccurring features, highlighting a poorly understood yet significant mechanism operating within the terrestrial carbon cycle.

Coastal landscape changes at Unguja Ukuu, Zanzibar: Contextualizing the archaeology of an early Islamic port of trade

Unguja Ukuu, located on the Zanzibar Archipelago, eastern Africa, was an active Indian Ocean trading settlement from the mid-first millennium until the early second millennium AD. As part of recent archaeological excavations aimed at understanding the site’s transregional trade networks, geoarchaeological analyses were undertaken to document the geomorphic context of the ancient settlement. Here, we outline the results of these field and laboratory studies to discuss patterns of anthropogenic sediment deposition. Unguja Ukuu’s deep coastal stratigraphy appears to record progradation of an inhabited back-reef shore from the mid-seventh to the nineth centuries AD, perhaps in the wake of an earlier middle to late Holocene marine transgression. Excavations on the back-beach show that deposits associated with the ancient settlement include interlayered middens, paleofloors, and backshore sands and, in later phases, a peri-urban dump with dark-earth-type anthrosols developed on these deposits. Coastal progradation appears to have been driven in part by the accumulation of anthropogenic detritus and compaction of ancient surfaces. We hypothesize how the inherited, submerged relic Late Pleistocene geomorphology of the intertidal zone and later Holocene sediment supply from the hinterland may have supported the emergence of Unguja Ukuu as a trading locale, and possibly contributed to its decline in the early second millennium AD.

Deep-Water Accumulation of Volcaniclastic Detritus from a Petrographic Point of View: Beginning a Discussion from the Alpine Peripheral Basins

The interpretation of eruptive mechanisms accumulating ancient submarine volcaniclastic sequences is still extremely challenging, particularly when no spatial nor temporal constraints are identifiable. The present work reviews petrographic results gained during the last few decades on three different Paleogene Formations accumulated around the Alpine and Apennine Mountain belts, discussing how their detritus could have been formed and moved from the volcanic centers to the depo-centers, taking into account the volcanic mechanisms which are at the base of the production, transportation and accumulation of volcaniclastic detritus. In doing this, we reconsider the classical diagrams of Folk and Gazzi–Dickinson, rediscussing their significance on the basis of how orogenic volcanism delivers detritus to the environment. In addition, this work highlights the need of the scientific community for gaining new petrographic data on modern sedimentary systems to better constrain interpretative criteria for the petrographic study of ancient volcano–sedimentary sequences.

Effects of the short- and long-term accumulation of detritus in larval habitats on life history traits of Aedes aegypti in temperate Argentina.

Aedes aegypti larvae that develop in containers largely depend on plant detritus as a source of nutritional resources. However, few studies have evaluated the performance of immature individuals under natural amounts and quality of this food source. Here, we aimed to assess the effect of the variation in the accumulation time and amount of detritus on life history traits of Ae. aegypti under semi-field conditions. Ae. aegypti larvae were raised with detritus collected in different sites to represent natural variability in its amount, simulating short (28 days) and long (70 days) accumulation. A control with optimal food conditions (yeast) was included. Survival, development time and wing length of adults were compared among treatments. Survival was relatively high in all treatments. Development time was similar among treatments but significantly longer and more variable in containers with the lowest detritus amounts. Wing lengths were smaller in the treatments with detritus than in the control, especially in females. The results support the hypothesis that, in a temperate region, Ae. aegypti larvae may have a nutritional limitation, at least in some containers, and emphasize the importance of performing experiments that simulate the environmental conditions to which individuals are exposed in nature.

The formation and failure process of Yigong landslide in Tibet Plateau

Yigong landslide is located in Zhamunong gully, Yigong Township, Bomi County, Linzhi region in Tibet, the volume of which is 3×108m3. Firstly, we analyse the formation mechanism of Yigong landslide in 2000, based on the field investigation and data collection. Secondly, we analyse the failure mechanism of Yigong landslide in 2000, combined with the mechanical test results of granite rock and stability calculation results of slumped mass (BH01). Under the combined effect of rapid incision and seismic activity in Yigong Lake zone, the basic factor of landslide formation is that the rock mass structure for controlled slope rock mass evolution has entered a stage of progressive failure in Zhamunong gully, and precipitating factors of landslide are excess melt-water and continuous rainfall under the temperature rise before landslide hazard happens, according to the results of the study. The formation process of landslide can be divided into 4 stages. (i) Trailing edge fracture of slope rock mass is in rapid development stage due to the effect of fast incision in the valley. (ii) The frequent seismic activities in Yigong Lake district facilitate the development and evolution of granite rock mass’s structural plane; (iii) The combined effect of excess melt-water and continuous rainfall at the prophase of the disaster makes the high angle fissure in trailing edge of BH01 rock fall body further develop. (iv) The high-speed rock fall block of BH01 rock fall body triggers the liquefaction of detrital accumulation materials at the source of gully, which forms landslide and finally transforms into high-speed granular mass flows. The stability-losing distruction mechanism of landslide is as follows. Under the combined effect of many conditions, such as fast incision of valley in Yigong district, earthquakes, temperature change, and continuous rainfall and so on, the high angle fissure in trailing edge of BH01 rock fall body develops quickly, and continuous creeping deformation occurs in rock fall body along weak structural plane or fracture surface, forming mid ‘locking section’. When the depth of cracking segment in trailing edge of BH01 rock fall body Hcr >363m or the length of rock mass’s locking section L<455m, sudden brittle failure occurs in the mid locking section of BH01 rock fall body, and rock fall occurs in rock fall body.

Unique habitat and macroinvertebrate assemblage structures in spring-fed stream: a comparison among clastic lowland tributaries and mainstreams in northern Japan

The stable flow and temperature regimes of spring-fed streams are distinct from the dynamic regimes of other streams. We investigated differences in habitat and macroinvertebrate assemblages among three stream types (spring-fed tributary, non-spring-fed tributary, and mainstream) in a clastic lowland of northern Japan. Current velocity was the slowest in the spring-fed reach, where the percent of fine sediment deposition was also 3.8–11.4 times higher than in the other stream types. The standing stock of detritus was also greater in the spring-fed reach. These results suggest that the stable flow regime in the spring-fed stream leads to the accumulation of fine sediment and detritus on the streambed. Oligochaeta and chironomids, which are burrower-gatherers, were remarkably abundant in the spring-fed reach. Total macroinvertebrate abundance was 3.8–12.2 times greater in the spring-fed reach than in the other stream types. Sprawler-grazer ephemeropterans were the most abundant in the mainstream reaches, likely due to higher primary productivity. Allomyia sp, which depend on cool spring-fed habitats, was found only in the spring-fed reach. The indicator species analysis also indicated multiple taxa of detritivores and Allomyia sp. for the spring-fed tributary. The macroinvertebrate assemblage in the spring-fed reach was characterized by numerous burrowers, collector-gatherers, and crenobiont taxa, highlighting the uniqueness and its contribution to enhance beta diversity in river networks.

Evaluation of environmental enrichment for Xenopus laevis using a preference test.

Xenopus laevis frogs have long been widely used as an animal model in research. However, their husbandry has scarcely evolved, although they are prone to environmental stress. Environmental enrichment has been shown to improve animal welfare and adaptation, as well as zootechnical indices, which have become very important in recent years. The aim of this study was to examine the preferences of X. laevis frogs for various elements of environmental enrichment: opaque polyvinyl chloride (PVC) pipes, artificial plants and clear spaces. A preferential study was conducted in two different tanks, each divided into six parts, where the two enrichment elements were rotated. Ten X. laevis frogs were introduced into each tank, and the number of frogs was counted in each division three times per day for six weeks. The number of frogs in the different spaces and different enrichments was evaluated through a Poisson regression model. Frogs preferred plants to PVC pipes and clear spaces regardless of the position of the enrichment element, time and day. This indicates that artificial plants should be used as the enrichment element rather than the commonly used PVC pipes. In addition, the use of plants facilitates the observation of frogs without disturbing them and reduces the accumulation of detritus, as it occurs inside the pipes.