Bottom Mud Research Articles

Establishment and application of a TaqMan probe-based qPCR for the detection of Enterocytozoon hepatopenaei in shrimp Litopenaeus vannamei.

Enterocytozoon hepatopenaei (EHP) is a common parasite that invades the epithelial cytoplasm in the hepatopancreas of shrimp Litopenaeus vannamei and results in slow growth of the host shrimps to cause significant economic loss in shrimp aquaculture. In this study, a TaqMan probe-based qPCR for quantitative detection of EHP was established. A pair of specific primers and a TaqMan probe were designed based on the sequence of cysteine desulfurase gene (NFS1) of EHP. The standard curve between cycle threshold (Ct) and the logarithmic starting quantity (SQ) of the template was determined as Ct = - 3.231 lg (SQ) + 40.638, with a correlation coefficient (R2) of 0.998 and an amplification efficiency of 103.9%. The lower limit of quantification was 1.67 × 101 copies/μL for this TaqMan probe-based qPCR and 1.67 × 103 copies/μL for the conventional PCR. The TaqMan probe-based qPCR established in the research was 100 times more sensitive than the conventional PCR method. In addition, the results of clinical sample detection indicated that the present technique was efficient in detecting EHP in the hepatopancreas, feces, water, and pond bottom mud samples. Therefore, the established TaqMan probe-based qPCR is a suitable technique for detecting EHP in both shrimp and aquatic environment samples.

Study on borehole temperature distribution when the well-kick and the well-leakage occurs simultaneously during geothermal well drilling

When the well-leakage or the well-kick occurs during drilling geothermal wells, the borehole temperature is redistributed. It causes the rheology and density of the mud to change, which in turn affects the borehole pressure control, borehole stability and cementing quality. In order to understand the distribution law of borehole temperature under complex working conditions in geothermal well drilling, this paper establishes a borehole temperature distribution model when well-leakage and well-kick occur simultaneously. The borehole temperature distribution law when well-leakage and well-kick occur simultaneously is obtained. When both the well-kick and the well-leakage exist in the drilling process, the temperature of the borehole and the formation fluctuates near the location where the well-kick and well-leakage occurs. Under the ordinary cycle condition, the highest temperature of annular drilling fluid is located at 5325 m; When the well-leakage occurs at the bottomhole and the well-kick occurs at a specific location in the borehole, the highest temperature of annular drilling fluid is at 5250 m; When the well-kick takes place at the bottomhole and the well-leakage occurs at a specific location in the borehole, the highest temperature of annular drilling fluid at 5286 m place. Compared with the ordinary cycle condition, when the well-leakage occurs at the bottom of the well and the well-kick occurs at a specific location in the borehole, the bottomhole mud temperature decreases after the same cycle time. And the temperature of the mud and the formations increases significantly near and above the position where the well-kick takes place. When the well-kick takes place at the bottom of the well, and the well-leakage occurs at a specific location in the borehole, compared with the ordinary cycle condition, the temperature of the bottom hole mud increases after the same cycle time and the mud temperature increases rather than decreases at the well-leakage location. Compared with other situations, it is found that when the well-kick occurs at the bottomhole, it has a more significant impact on the temperature distribution of the entire borehole.

Fish and invertebrate use of restored vs. natural oyster reefs in a shallow temperate latitude estuary

AbstractCoastal marine habitats continue to be degraded, thereby compelling large‐scale restoration in many parts of the world. Whether restored habitats function similarly to natural habitats and fully recover lost ecosystem services is unclear. In estuaries, oyster reefs have been degraded by multiple anthropogenic activities including destructive fishing practices and reduced water quality, motivating restoration to maintain oyster fisheries and other ecosystem services, often at relatively high cost. We compared fish and invertebrate communities on recently restored (0–1 year post‐restoration), older restored (3–4 years post‐restoration), and natural oyster reefs to determine if and when restored reefs support functionally similar faunal communities. To test the influence of landscape setting on the faunal communities, the restored and natural reefs, as well as a control without reef present, were distributed among three landscapes (on the edge of salt marsh away from seagrass [salt marsh landscape], on mudflats [mudflat landscape], and near to seagrass and salt marsh [seagrass landscape]). Oyster density and biomass were greatest on restored reef habitat, as were those of non‐oyster bivalve species. Total abundance of invertebrates was much greater on oyster reefs than in control plots, regardless of reef or landscape type, yet were frequently highest on older restored reefs. Meanwhile, juvenile fish densities were greatest on natural reefs, at intermediate densities on older restored reefs, and least abundant on controls. When comparing the effects of reef age and landscape setting, juvenile fish densities were greatest on younger reefs within the mudflat landscape. Collectively, these results indicate that oyster reefs harbor higher densities of resident invertebrate prey, which may explain why reef habitat is also important for juvenile fish. Laboratory and field experiments supported the notion that gag grouper (a predatory demersal fish) forage more effectively on oyster reefs than on unstructured mud bottom, whereas our experiments suggest that flounders that utilize oyster reefs likely forage on adjacent mud bottom. Because landscape setting influenced fish and invertebrate communities on restored reefs, the ecological consequences of landscape setting should be incorporated into restoration decision making and site selection to enhance the recovery of ecosystem goods and services.

Sediment phosphate release flux under hydraulic disturbances in the shallow lake of Chaohu, China.

Quantifying the effect of hydraulic disturbances on sediment phosphate release is a key issue in the water quality assessment of lakes, especially for the shallow lakes which are susceptible to winds and waves. Here, we sampled the original sediment columns from 12 positions in the eastern, central, and western areas of the Chaohu Lake, a representative shallow lake in China, and observed phosphate release under three levels of hydraulic disturbances in the laboratory. When the disturbance was weak and sediment on the surface of bottom mud moved individually (the Individual Motion Mode), sediment phosphate release rate was insignificant (0.24mg/m2/day). When the disturbance was medium and only a small percentage (< 16%) of surface sediment started to move (the Small Motion Mode), the phosphate release rate sharply increased to 4.81mg/m2/day. When the disturbance was further strengthened and most (≥ 16%) of the surface sediment moved (the General Motion Mode), the phosphate release rate was more than doubled (10.23mg/m2/day). With the increase in hydraulic disturbance intensity, the variation range of phosphate release also became wider. Spatial distribution showed that the release rate varies the most in the western area, followed by the eastern and the central areas. By extrapolating the experimental results to the real scale, it was found that the phosphate release fluxes would probably fall within a wide range between 203.43 to 7311.01kg/day under different levels of hydrodynamic disturbances which considerably affects phosphate release from shallow lakes. This study also has implications for the pollutant management in other shallow lakes.

Nitidotellina hachiensis n. sp. (Bivalvia: Tellinidae) from the Seto Inland Sea, between Honshū and Shikoku, western Japan

ABSTRACT A new species of tellinid, Nitidotellina hachiensis, is described from Japan. The shell of this species is characterised by a pair of strong keels that run from the beaks to the posterior end and forms a prominent posterior notch. The recent individuals are found only in the Seto Inland Sea (Okayama, Hiroshima, Yamaguchi and Ehime prefectures), while the one fossil record so far known is from the Chibanian (middle Pleistocene) Toyohashi Formation in Aichi Prefecture, central Honshū. Living individuals are uncommon and mainly found living in sandy mud bottoms from the low tide line down to the subtidal zone in the inner parts of large bays. It can be regarded as endangered due to the recent habitat loss and water pollution of inner bay environments.

Effects of Environmental and Spatial Variables on Bacteria in Zhanjiang Mangrove Sediments.

The bottom mud of mangroves contains numerous microbial groups that play an important role in the main ecological functions of the mangrove ecosystem. The diversity and functional and environmental factors related to microbial communities, in terms of the assembly process and in environmental adaptation of the abundance and rare bacterial communities in the mangrove ecosystem, have not been fully explored. We used 16S high-throughput sequencing and operational taxonomic unit analysis to compare the diversity and composition of bacterial communities in different tidal zones in the sediments of the Zhanjiang Gaoqiao Mangrove Nature Reserve, compare the ecological adaptation thresholds and phylogenetic signals of bacterial communities under different environmental gradients, and examine the factors affecting the composition of the bacterial community. The diversity of microbial species and structure and function of the mangrove sediments were affected by the environment, showing the trend: mid tide zone > climax zone > low tide zone. Organic matter content, oxygen content, pH, and total phosphorus were identified as important environmental factors determining the functional diversity of bacterial communities and survival, while pH influences species evolution. The abundant taxa showed a wider response threshold and stronger phylogenetic signals of ecological preference across environmental gradients compared to rare taxa. The abundant bacterial groups have broader environmental adaptability than rare bacterial groups, and different environmental factors affect different communities and functions in the mangrove ecological environment. These results elucidate the mechanism underlying the generation and maintenance of bacterial diversity in response to global environmental changes.

DANGER IN SHALLOW WATERS: LIONFISH Pterois volitans (LINNAEUS, 1758) IN AMAZON RIVER PLUME, AMAPÁ, BRAZIL

A new record of the red lionfish Pterois volitans is related to the Amazon River plume. The specimen examined is an adult male, total length 34 cm and weight 620g, caught at june 4th, 2022, by artisanal multispecies fishery, with gillnet at Amapá State, next to Cabo Orange National Park, 04°03’02,67 N 050°56’11,22W, depth of 10 m, in soft bottom (sand and mud). The record expands the geographical distribution of P. volitans, in shallow and low-salinity waters of the Amazon continental shelf.

Spatio-temporal variations of salinity and analysis of desalination factors in a Chinese coastal storage reservoir

Coastal reservoirs could be used to store freshwater in coastal cities, but the conversion of coastal reservoirs to freshwater reservoirs is relatively time-consuming, and coastal reservoirs are facing a risk of salinization. Taking Zhuyu Lake as the research object, the Spatio-temporal variations of water salinity under different seasons were investigated using the field survey and modeling. The influencing factors of the water salinity of the reservoir were analyzed to discover the variation mechanism. The results showed that the disturbance of overlying water is the most significant factor affecting the salt release of sediment, and salt release was increased by 63.3% with the disturbance. The depth of the overlying water and the salt content of bottom sediment also significantly affected the release of salt, with maximum enhancement by 23.1% and 45.6%, respectively. The microbial content in the bottom mud played an essential role in maintaining the salt, and inhibiting the microbial activity could enhance the release of salt by 35.7%. Therefore, disturbing the sediment by using disturbance ships or aeration devices, and the establishment of a long-term periodic plant harvesting belt could be used in the coastal fresh reservoirs desalination and slowing down the salinization of fresh reservoirs.

A description of Florida estuarine gradient complexes and the implications of habitat factor covariation for community habitat analysis

A multi-parameter dataset from 13 Florida estuaries demonstrated complications that multiple gradients (the estuarine gradient complex, EGC) 1 impose when trying to characterize species distributions using regression-based analyses. Variation in the beta diversity of assemblages consisting of 974 taxa in four groups (ichthyoplankton, invertebrate zooplankton, seine nekton, trawl nekton) were assessed using 29 habitat factors. Habitat data were obtained from measurements made during biotic collections, associated characterizations of local habitats, data obtained from the United States Environmental Protection Agency Storage and Retrieval database, and from data that characterized the timing and magnitude of freshwater inflow and turnover. When all habitat factors were used in multivariate regression models (distance-based redundancy analysis, dbRDA) with the objective of explaining variation in beta diversity, the models accounted for as much as 52% of the variation and included factors such as salinity, color, water temperature, distance to the Gulf of Mexico, water depth, presence of mud bottom, and the amount of freshwater input. Habitat factors that contributed to the EGC were identified by performing correlation analyses between each habitat factor and distance to the Gulf of Mexico. This step indicated that, in surface-fed estuaries, submerged aquatic vegetation, mangroves, and warmer temperatures were more common downstream, and lower pH, deeper depths, lower bottom dissolved oxygen, lawn-and-tree shorelines, and manmade bottom substrates were more common upstream. In spring-fed estuaries, oysters and mangroves were more common downstream, and lawn-and-tree shorelines were more common upstream. These correlated factors were used to represent the EGC and were explicitly included in dbRDAs where they explained as much as 78% of the variability in beta diversity. A subsequent partial-dbRDA was performed on the variation that was not explained by EGC habitat factors, and non-EGC factors (freshwater inputs, artificial shorelines, shoreline slope, and the presence of sand bottom) explained as much as an additional 7% of the variability. These results demonstrate the complications inherent in assigning influence to any one habitat factor in estuaries where many habitat factors covary spatially. The substantial amount of beta diversity variation explained by the EGC indicates a goal of estuarine management should be to promote heterogeneity in habitat factors contained in the EGC to maintain overall community diversity.

Fluid mud dynamics in a tide-dominated estuary: A case study from the Yangtze River

Fluid mud plays an important role in the maintenance of the estuarine turbidity maximum (ETM) and makes a significant contribution to estuarine sediment transport. A seabed tripod system and a shipboard vertical profile were deployed to explore the spatial-temporal variation and mechanism of fluid mud in the ETM of the Yangtze Estuary. The near-bed suspended sediment concentration (SSC) measured by OBS and ABS exceeded 50 kg/m3, confirming the existence of fluid mud. The fluid mud layer varied frequently in thickness during spring and intermediate tides, with a maximum of up to 0.6 m, but maintained stability during neap tides. The thickness rose rapidly during the larger ebb tide in semidiurnal tidal cycles of intermediate tides when the gradient Richardson number (Ri) increased to exceed the critical value of 0.25, and the velocity at 0.2 mab was in the range of 0.5–0.8 m/s. The fluid mud layer transported more than twice as much sediment as the low-concentration upper layer did. Waves and intense currents at the flood phase of tide enhanced vertical mixing within the water column, with Ri being reduced to lower than 0.25 and turbulent kinetic energy (TKE) exceeding 0.01 m2/s2, leading to the breakdown of the fluid mud layer. Sediment stratification damps turbulence close to the seabed and leads to gradual solidification of the bottom fluid mud. Approximately 0.2 m of fluid mud deposit was formed on the seabed within 148 h of the observation period.

Isolation and selection of nitrite metabolising bacteria from the bottom mud of lobster culture area in Xuan Dai bay, Phu Yen province

The study had isolated and selected groups of bacteria that metabolise nitrite from the bottom mud of lobster cages in Xuan Dai bay, Phu Yen province. Analysis results from 21 sludge samples taken from 11 cages of lobster farming area isolated 16 strains of bacteria capable of nitrite metabolism. After investigating biological characteristics and nitrite metabolism of bacteria strains, 10 strains of bacteria were collected with the ability to metabolise nitrite over 95% in 72 hours. In addition, 10 strains of bacteria with the highest NO2- treatment efficiency, identified by genetic analysis and looked up on BLAST, defined as Stenotrophomonas pavanii, Chryseobacterium gleum, Stenotrophomonas maltophilia, Delftia lacustris, Acinetobacter junii

Effects of pH on the dynamic migration of nutrient salts in the sediment of ditches in mountain rural areas

Objective As pH is a key factor affecting the migration and release of nutrients in the ditch sediment, this study, with an investigation of the dynamic changes of nutrient release and migration in the bottom mud of mountainous rural ditches under different pH conditions, is aimed to provide a theoretical basis for rural ecological environment management. Method With the bottom mud of typical mountainous rural ditches in the Dianchi Lake Basin collected, indoor simulation experiments were conducted to determine the nutrient salt content of the bottom mud and the overlying water under different pH (pH 5.5, 7.5, 9.5, 11.5) conditions under non-sterilized and sterilized treatments after which the nutrient release flux at the sediment-water interface was estimated. Result The mass fraction of total nitrogen (TN) in the bottom sludge decreased with the increase of pH. The total nitrogen release flux under the strong alkaline (pH 11.5) and acidic (pH 5.5) conditions of the non-sterilized group was 8 and 4 times of the control (pH 7.5), and its release flux in the sterilization group was 2 times of that in the control. The mass concentration and release flux of soluble total phosphorus (DTP) in the overlying water increased with the increase of pH. The release of DTP under the conditions of strong alkaline (pH 11.5) and weak alkaline (pH 9.5) in the non-sterilized group was 12 and 4 times of that in the control, respectively, and its release flux in the sterilized group was 30 and 15 times of that in the control while the non-sterilized group had higher DTP release flux than the sterilized group. RDA shows that acidic conditions promote the release of calcium-bound phosphorus (Ca-P) in sediments, and alkaline (pH≥9.5) conditions promote the release of total nitrogen, total phosphorus and iron-aluminum-bound phosphorus (Fe/Al-P). Neutral (pH 7.5) conditions have little effect on the release of nitrogen or phosphorus in the sediments. Conclusion Alkalinity (pH≥9.5) and acidity significantly promote the release of nitrogen and phosphorus nutrients in the bottom mud of mountain rural ditches, and the release amount is the smallest under neutral conditions. Also, the sterilization of the bottom sludge reduces the microbial activity at different pH levels, and prevents the migration and release of nitrogen and phosphorus in the bottom sludge of mountain and rural ditches to the overlying water. [Ch, 6 fig. 1 tab. 36 ref.]

Adsorption and migration of heavy metals between sediments and overlying water in the Xinhe River in central China.

Long-term polluted rivers often lead to the accumulation of heavy metals in sediments. Anthropogenic activities or biological disturbances break the adsorption balance, causing them to return from the bottom mud to the overlying water and change the aquatic environment. In order to understand the variation of heavy metals between sediments and river water, we collected the riverbed sediments in the polluted Xinhe River and carried out static continuous infiltration and dynamic uninterrupted disturbance experiments. The leaching experiment shows that the absorbability of Cd and Pb is stronger than Cr in the sediment; at the same time, the properties of the medium have a great influence on the adsorption of heavy metals. The disturbance can prompt heavy metals in the sediment to resuspend into the overlying water. The impact is the greatest during the first 12 h, and the influence degree is stronger in the relatively static water than in the moving river. In addition, pH and other factors have different degrees of influence on the desorption of heavy metals.

Using drones and ROV to assess the vulnerability of marine megafauna to the Fundão tailings dam collapse

The ecology and life history of marine megafauna can answer the ecological importance of a region. This study assesses and monitors the abundance and home range of sea turtles, seabirds, marine mammals and the association with coastal microhabitats in potentially impacted areas at the Rio Doce river mouth, Comboios, and Piraquê-açu river mouth after the collapse of the Fundão dam. Remotely Operated Vehicles (ROV) and UAVs (Unmanned Aerial Vehicles, or drones) were used for megafauna species identification, behavior, population data, habitat characterization, and monitoring of environmental protection areas. The species Sotalia guianensis and Pontoporia blainvillei were the most recorded cetaceans, and the main observed behavior was feeding. Guiana dolphin (S. guianensis) occurs in greater density in the Rio Doce river mouth region, resulting in more than 10 sightings/km2, while franciscana (P. blainvillei) were the most concentrated Comboios area. The seabirds (all species) had up to 15 sightings/km2 at the Rio Doce river mouth, the highest density among sampled areas. The green turtle (Chelonia mydas) was the most frequently recorded, followed by the leatherback turtle (Dermochelys coriacea). The green turtle occurred at a higher concentration at the Piraquê-Açu river mouth (above 6 sightings/km2). The sites closest to Rio Doce river mouth and Comboios predominantly showed mud bottoms, while those at Piraquê-Açu mouth were mostly reef structures. The estuarine areas showed greater importance for megafauna than marine areas.

Transcriptomics unravels molecular players shaping dorsal lip hypertrophy in the vacuum cleaner cichlid, Gnathochromis permaxillaris

BackgroundTeleosts display a spectacular diversity of craniofacial adaptations that often mediates ecological specializations. A considerable amount of research has revealed molecular players underlying skeletal craniofacial morphologies, but less is known about soft craniofacial phenotypes. Here we focus on an example of lip hypertrophy in the benthivorous Lake Tangnayika cichlid, Gnathochromis permaxillaris, considered to be a morphological adaptation to extract invertebrates out of the uppermost layer of mud bottom. We investigate the molecular and regulatory basis of lip hypertrophy in G. permaxillaris using a comparative transcriptomic approach.ResultsWe identified a gene regulatory network involved in tissue overgrowth and cellular hypertrophy, potentially associated with the formation of a locally restricted hypertrophic lip in a teleost fish species. Of particular interest were the increased expression level of apoda and fhl2, as well as reduced expression of cyp1a, gimap8, lama5 and rasal3, in the hypertrophic lip region which have been implicated in lip formation in other vertebrates. Among the predicted upstream transcription factors, we found reduced expression of foxp1 in the hypertrophic lip region, which is known to act as repressor of cell growth and proliferation, and its function has been associated with hypertrophy of upper lip in human.ConclusionOur results provide a genetic foundation for future studies of molecular players shaping soft and exaggerated, but locally restricted, craniofacial morphological changes in fish and perhaps across vertebrates. In the future, we advocate integrating gene regulatory networks of various craniofacial phenotypes to understand how they collectively govern trophic and behavioural adaptations.

Embryonic developmental arrest in the annual killifish Austrolebias charrua: A proteomic approach to diapause III.

Diapause is a reversible developmental arrest faced by many organisms in harsh environments. Annual killifish present this mechanism in three possible stages of development. Killifish are freshwater teleosts from Africa and America that live in ephemeral ponds, which dry up in the dry season. The juvenile and adult populations die, and the embryos remain buried in the bottom mud until the next rainy season. Thus, species survival is entirely embryo-dependent, and they are perhaps the most remarkable extremophile organisms among vertebrates. The aim of the present study was to gather information about embryonic diapauses with the use of a “shotgun” proteomics approach in diapause III and prehatching Austrolebias charrua embryos. Our results provide insight into the molecular mechanisms of diapause III. Data are available via ProteomeXchange with identifier PXD025196. We detected a diapause-dependent change in a large group of proteins involved in different functions, such as metabolic pathways and stress tolerance, as well as proteins related to DNA repair and epigenetic modifications. Furthermore, we observed a diapause-associated switch in cytoskeletal proteins. This first glance into global protein expression differences between prehatching and diapause III could provide clues regarding the induction/maintenance of this developmental arrest in A. charrua embryos. There appears to be no single mechanism underlying diapause and the present data expand our knowledge of the molecular basis of diapause regulation. This information will be useful for future comparative approaches among different diapauses in annual killifish and/or other organisms that experience developmental arrest.

Culturable fungi from dredged and marine sediments from six ports studied in the framework of the SEDITERRA Project

Mycological characterisation of marine and dredged sediments consists of the isolation of vital and culturable fungal strains as well as their identification and analysis, in order to increase knowledge of sediment mycobiota and isolated species that can be employed in biotechnological processes. Our study undertook the mycological characterisation of sediments from six different port environments: marine bottom sediments from the ports of Genoa (Liguria, Italy) and Centuri (Corsica, France), dredged sediments (sediments removed from the sea bottom) from landfill sites (contaminated land sites where dredged sediments are deposited) of the ports of Leghorn (Tuscany, Italy) and Cagliari (Sardinia, Italy), bottom muds from the brackish environment of the navigable Navicelli Canal of Pisa (Tuscany, Italy) and dredged marine sediments from a temporary storage site in the port of Toulon (Var, France). At each site, 30 kg of sediment was sampled for physical, chemical and mycological analyses. They were analysed in terms of grain size composition, organic and inorganic content, metal concentration and hydrocarbon and polychlorinated biphenyl concentration. Fungi were then isolated from sediments by a modified dilution plate technique from 1:10 up to 1:100. Fungal identification was carried out using a morphological and molecular polyphasic approach. Forty-six fungal species belonging to 20 genera were isolated. The highest biodiversity was found in Leghorn (14 species), Genoa (11) and Cagliari (11) sediments, while very low numbers of species were isolated from the ports of Centuri (3) and Toulon (4). Similarly, the number of colony-forming units (CFUs), calculated on the dry weight of the sediments, followed this order: Genoa (3,765 CFUs*g-1) > Leghorn (1,370 CFUs*g-1) > Pisa (1,190 CFUs*g-1) > Cagliari (410 CFUs*g-1) > Toulon (380 CFUs*g-1) > Centuri (220 CFUs*g-1). The most represented genera were Penicillium, Aspergillus and Trichoderma. Some halotolerant species known for their biotechnological properties were isolated: Emericellopsis maritima, Cladosporium halotolerans and Aspergillus micronesiensis. A potential marine pathogenic fungus was found: Aspergillus sydowii. This work increased knowledge of fungi from marine and dredged sediments in six Mediterranean ports in the framework of the SEDITERRA Project.

Effect of Oxidation Strengthening on In-situ Phosphorus Immobilization of Calcium Hydroxide

In this research, calcium hydroxide[Ca(OH)2] and hydrogen peroxide (H2O2) were injected into the bottom mud in the form of plum blossom scatterers to investigate the effect on the control of endogenous phosphorus. The results showed that Ca(OH)2 used singly effectively immobilized in the order of 90% of endogenous phosphorus approximately 20 mm below the sediment-water interface (SWI); however, at the same time, the anaerobic environment was enhanced, resulting in the transformation of stable phosphorus to easily released phosphorus and the accumulation of potential active phosphorus. Nevertheless, the addition of H2O2 greatly reduced the amount of potential active phosphorus in deep sediments after adding Ca(OH)2. The vertical diffusion depth of Ca(OH)2 in the sediments was significantly increased, having an influence across the depth range of 0-40mm below the SWI; the improvement at depths greater than 40 mm was not notable, which was mainly attributed to an 18-fold increase of redox potential due to the addition of the oxidant. The change of phosphorus forms in the sediment also demonstrated the excellent immobilization effect of the oxidant on phosphorus. In the 0-20 mm layer, the content of readily released phosphorus decreased significantly, while compared with a control test, Ca-P increased by approximately 10%. However, at greater depths, the amount of easily released phosphorus decreased and the rate of Ca-P increase gradually slowed.

Continental shelf morphology controlled by bottom currents, mud diapirism, and submarine slumping to the east of the Gaoping Canyon, off SW Taiwan

The Gaoping River-Gaoping Submarine Canyon (GPC) is one of the dispersal river systems in the world. Tens of tons of terrestrial sediments discharge per year at the mouth of the river, where gravity-driven flow can damage the telecommunication cable along the 260-km-long GPC; to the east of the GPC, the continental shelf has been eroded. To understand this geological phenomenon, high-resolution sparker seismic data around the continental shelf as well as parallel and across the GPC were collected. Deep-towed sub-bottom profiler (SBP) data and data from shipboard acoustic Doppler current profiler were also collected. Three major system tracts off southwest Taiwan were identified, based on which the coastline of the last glacial maximum was identified at approximately 138 m below the current sea level. Analysis of the deep-towed SBP profiles suggested sandy sediment overflows through breakages on the east bank of the GPC. A convergence of bottom currents with a speed of up to 1.5 m/s flowing southeastward has eroded the continental shelf intensively, forming the Xiaoliuchiu channel. Although a mud diapir is active to the east of the GPC and forms the Xiaoliuchiu islet, it has been eroded at the Xiaoliuchiu channel. The average erosion rate on the east bank of the GPC was estimated to be approximately 609 cm/ka in the past 8.2 ka; between the GPC and the Xiaoliuchiu islet, the continental shelf is wasted due to severe seabed slumping.

A study on the characteristics of diatoms and ecological environment pollution in the main water of Tianjin, China

Twenty lake bottom surface layers mud and water samples in the Qilihai Wetland and the Beidagang Reservoir in Tianjin were taken to do diatoms analysis. More than 6000 diatoms were identified and divided into 117 species and 28 genera. Based on the calculation of DAIpo(Diatom Assemblage to organic water pollution), the water pollution level of the Beidagang Reservoir can be divided into: Xenosaprobic, β -oligosaprobic, α -oligosaprobic, β -mesosaprobic, from clear to slightly cloudy water. The water pollution level of Qilihai wetland can be divided into: extremely oligarchy dirt belt, β oligarchy dirt belt, α oligarchy dirt belt, β Medium dirt belt, that is, the water quality is clear to slightly turbid. The water quality of the Beidagang Reservoir is clearer than that of the Qilihai Wetland. The physical and chemical indexes such as EC, pH, TN, TP and CODMn were determined for the water samples, and the correlation between DAIpo and these measured values was analyzed. The results showed that the degree of water pollution detected was consistent with the conclusion obtained by diatom analysis. The results show that the water quality of the Beidagang Reservoir and the Qilihai Wetland was mildly polluted in the spring and summer of 2019, but the eutrophication is more serious.