Soil Salinity Estimation Over Coastal Wetlands Based on Random Forest Algorithm and Hydrological Connectivity Metric

Owing to climate warming and human activities (irrigation and reservoirs), sea level rise and runoff reduction have been threatening the coastal ecosystem by increasing the soil salinity. However, short-term sparse in situ observations limit the study on the response of coastal soil salinity to external stressors and thus its effect on coastal ecosystem. In this study, based on hydrological connectivity metric and random forest algorithm (RF), we develop a coastal soil salinity inversion model with in situ observations and satellite-based datasets. Using Landsat images and ancillary as input variables, we produce a 30-m monthly grid dataset of surface soil salinity over the Yellow River Delta. Based on the cross-validation result with in situ observations, the proposed RF model performs higher accuracy and stability with determination coefficient of 0.89, root mean square error of 1.48 g·kg-1, and mean absolute error of 1.05 g·kg-1. The proposed RF model can gain the accuracy improvements of about 11–43% over previous models at different conditions. The spatial distribution and seasonal variabilities of soil salinity is sensitive to the changing signals of runoff, tide, and local precipitation. Combining spatiotemporal collaborative information with the hydrological connectivity metric, we found that the proposed RF model can accurately estimate surface soil salinity, especially in natural reserved regions. The modeling results of surface soil salinity can be significant for exploring the effect of seawater intrusion and runoff reduction to the evolution of coastal salt marsh ecosystems

Reciprocal facilitation between annual plants and burrowing crabs:Implications for the restoration of degraded saltmarshes

Increasing evidence shows that facilitative interactions between species play an essential role in coastal wetland ecosystems. However, there is a lack of understanding of how such interactions can be used for restoration purposes in saltmarsh ecosystems. We therefore studied the mechanisms of reciprocal facilitative interactions between native annual plants, Suaeda salsa, and burrowing crabs, Helice tientsinensis, in a middle-elevation saltmarsh (with generally high plant density and moderate tides) in the Yellow River Delta of China. We investigated the relationship between the densities of the plants and crab burrows in different seasons. Then, we tested whether and how saltmarsh plants and crabs indeed facilitate each other in a series of field and laboratory experiments. Finally, we applied the results by creating a field-scale artificial approach for microtopographic modification to restore a degraded saltmarsh. We found that the density of plant seedlings in spring was positively correlated with the density of crab burrows in the previous autumn; moreover, the density of crab burrows was correlated with the density of plants in summer. The concave-convex surface microtopography created by crabs promoted seed retention and seedling establishment of saltmarsh plants in winter and spring. These plants in turn facilitated crabs by inhibiting predators, providing food and reducing physical stresses for crabs in summer and autumn. The experimental removal of saltmarsh plants decreased crab burrow density, while both transplanting and simulating plants in bare patches promoted crabs. The microtopographic modification, inspired by our new understanding of the interactions between saltmarsh plants and crabs, showed that these degraded saltmarsh ecosystems can be restored by a single ploughing intervention. Synthesis. Our results suggest a reciprocal facilitation between annual plants and burrowing crabs in a middle-elevation saltmarsh ecosystem. This knowledge yielded new restoration options for degraded coastal saltmarshes through the one-time ploughing initiation of microtopographic variation, which could promote the re-establishment of ecosystem engineers and lead to the efficient recovery of pioneer coastal vegetation and associated fauna

Near-infrared fluorescent macromolecular reporters for real-time imaging and urinalysis of cancer immunotherapy

Real-time imaging of immunoactivation is imperative for cancer immunotherapy and drug discovery; however, most existing imaging agents possess "always-on" signals and thus have poor signal correlation with immune responses. Herein, renal-clearable near-infrared (NIR) fluorescent macromolecular reporters are synthesized to specifically detect an immunoactivation-related biomarker (granzyme B) for real-time evaluation of cancer immunotherapy. Composed of a peptide-caged NIR signaling moiety linked with a hydrophilic poly(ethylene glycol) (PEG) passivation chain, the reporters not only specifically activate their fluorescence by granzyme B but also passively target the tumor of living mice after systemic administration. Such granzyme B induced in vivo signals of the reporters are validated to correlate well with the populations of cytotoxic T lymphocytes (CD8⁺) and T helper (CD4⁺) cells detected in tumor tissues. By virtue of their ideal renal clearance efficiency (60% injected doses at 24 h postinjection), the reporters can be used for optical urinalysis of immunoactivation simply by detecting the status of excreted reporters. This study thus proposes a molecular optical imaging approach for noninvasive evaluation of cancer immunotherapeutic efficacy in living animals.Ministry of Education (MOE)Nanyang Technological UniversityThis work was supported by Nanyang Technological University (NTU-SUG: M4081627) and the Singapore Ministry of Education Academic Research Fund Tier 1 (2017-T1-002-134, RG147/17; 2019-T1-002-045, RG125/19) and Tier 2 (MOE2018-T2-2-042)

Molecular optical imaging probes for early diagnosis of drug-induced acute kidney injury

Drug-induced acute kidney injury (AKI) with a high morbidity and mortality is poorly diagnosed in hospitals and deficiently evaluated in drug discovery. Here, we report the development of molecular renal probes (MRPs) with high renal clearance efficiency for in vivo optical imaging of drug-induced AKI. MRPs specifically activate their near-infrared fluorescence or chemiluminescence signals towards the prodromal biomarkers of AKI including the superoxide anion, N-acetyl-β-D-glucosaminidase and caspase-3, enabling an example of longitudinal imaging of multiple molecular events in the kidneys of living mice. Importantly, they in situ report the sequential occurrence of oxidative stress, lysosomal damage and cellular apoptosis, which precedes clinical manifestation of AKI (decreased glomerular filtration). Such an active imaging mechanism allows MRPs to non-invasively detect the onset of cisplatin-induced AKI at least 36 h earlier than the existing imaging methods. MRPs can also act as exogenous tracers for optical urinalysis that outperforms typical clinical/preclinical assays, demonstrating their clinical promise for early diagnosis of AKI.MOE (Min. of Education, S’pore)Accepted versio

Self-organized mud cracking amplifies the resilience of an iconic “Red Beach” salt marsh

Self-organized patterning, resulting from the interplay of biological and physical processes, is widespread in nature. Studies have suggested that biologically triggered self-organization can amplify ecosystem resilience. However, if purely physical forms of self-organization play a similar role remains unknown. Desiccation soil cracking is a typical physical form of self-organization in coastal salt marshes and other ecosystems. Here, we show that physically self-organized mud cracking was an important facilitating process for the establishment of seepweeds in a “Red Beach” salt marsh in China. Transient mud cracks can promote plant survivorship by trapping seeds, and enhance germination and growth by increasing water infiltration in the soil, thus facilitating the formation of a persistent salt marsh landscape. Cracks can help the salt marsh withstand more intense droughts, leading to postponed collapse and faster recovery. These are indications of enhanced resilience. Our work highlights that self-organized landscapes sculpted by physical agents can play a critical role in ecosystem dynamics and resilience to climate change.</p

Near-infrared afterglow semiconducting nano-polycomplexes for multiplex differentiation of cancer exosomes

The detection of exosomes is promising for the early diagnosis of cancer. However, the development of suitable optical sensors remains challenging. We have developed the first luminescent nanosensor for the multiplex differentiation of cancer exosomes that bypasses real‐time light excitation. The sensor is composed of a near‐infrared semiconducting polyelectrolyte (ASPN) that forms a complex with a quencher‐tagged aptamer. The afterglow signal of the nanocomplex (ASPNC), being initially quenched, is turned on in the presence of aptamer‐targeted exosomes. Because detection of the afterglow takes place after the excitation, background signals are minimized, leading to an improved limit of detection that is nearly two orders of magnitude lower than that of fluorescence detection in cell culture media. Also, ASPNC can be easily tailored to detect different exosomal proteins by changing the aptamer sequence. This enables an orthogonal analysis of multiple exosome samples, potentially permitting an accurate identification of the cellular origin of exosomes for cancer diagnosis.MOE (Min. of Education, S’pore)Accepted versio

Quantification of intensive hybrid coastal reclamation for revealing its impacts on macrozoobenthos

Managing and identifying the sources of anthropogenic stress in coastal wetlands requires an in-depth understanding of relationships between species diversity and human activities. Empirical and experimental studies provide clear evidence that coastal reclamation can have profound impacts on marine organisms, but the focus of such studies is generally on comparative or laboratory research. We developed a compound intensity index (reclamation intensity index, RI) on hybrid coastal reclamation, to quantify the impacts of reclamation on coastal ecosystems. We also made use of mean annual absolute changes to a number of biotic variables (biodiversity, species richness, biomass of total macrozoobenthos, and species richness and biomass of Polychaeta, Mollusca, Crustacea, and Echinodermata) to determine Hedges’ d index, which is a measure of the potential effects of coastal reclamation. Our results showed that there was significant difference of coastal reclamation intensity between Yellow Sea, East China Sea and South China Sea, the biological changes in effect sizes of the three regions differed greatly over time. Our modelling analyses showed that hybrid coastal reclamation generally had significant negative impacts on species diversity and biomass of macrozoobenthos. These relationships varied among different taxonomic groups and included both linear and nonlinear relationships. The results indicated that a high-intensity of coastal reclamation contributed to a pronounced decline in species diversity and biomass, while lower-intensity reclamation, or reclamation within certain thresholds, resulted in a small increase in species diversity and biomass. These results have important implications for biodiversity conservation and the ecological restoration of coastal wetlands in face of the intensive reclamation activities

Stocking rate changed the magnitude of carbon sequestration and flow within the plant-soil system of a meadow steppe ecosystem

Aims Livestock grazing is one of the most common utilization methods and exerts a significant effect on the carbon allocations between the above- and belowground components of a grassland ecosystem. The major aim of this study were to evaluate the proportions of C-13 allocation to various C pools of the plant-soil system of a meadow steppe ecosystem in response to changes of stocking rate. Methods In situ stable C-13 isotope pulse labeling was conducted in a long-term grazing experiment with 4 stocking rate. Plant materials and soil samples were taken at eight occasions (0, 3, 10, 18, 31, 56 and 100 days after labeling) to analyze the decline in C-13 over time, and their composition signature of C-13 were analyzed by the isotope ratio mass spectrometer technique. Results We found a significantly greater decline in assimilated C-13 of shoot and living root for the heavily grazed swards compared to other stocking rates, with the highest relocation rate of C-13 into soil C pool compared to other fractions. In addition, light grazing significantly allocated C-13 assimilates in the belowground pool compared to other stocking rates, especially in the live root and topsoil C-pools. Conclusions In this study, the effects of grazing on the carbon transfers and stocks within the plant-soil system of the meadow steppe were highly grazing pressure dependent. Plant-soil system in light stocking rate presented the highest C utilization efficiency, however, plants allocated more C to soil C pools with heavily stocking rate

A renal-clearable duplex optical reporter for real-time imaging of contrast-induced acute kidney injury

Despite its high morbidity and mortality, contrast‐induced acute kidney injury (CIAKI) remains a diagnostic dilemma because it relies on in vitro detection of insensitive late‐stage blood and urinary biomarkers. We report the synthesis of an activatable duplex reporter (ADR) for real‐time in vivo imaging of CIAKI. ADR is equipped with chemiluminescence and near‐infrared fluorescence (NIRF) signaling channels that can be activated by oxidative stress (superoxide anion, O2.−) and lysosomal damage (N‐acetyl‐β‐d‐glucosaminidase, NAG), respectively. By virtue of its high renal clearance efficiency (80 % injected doses after 24 h injection), ADR detects sequential upregulation of O2.− and NAG in the kidneys of living mice prior to a significant decrease in glomerular filtration rate (GFR) and tissue damage in the course of CIAKI. ADR outperforms the typical clinical assays and detects CIAKI at least 8 h (NIRF) and up to 16 h (chemiluminescence) earlier.MOE (Min. of Education, S’pore)Accepted versio

Cell membrane coated semiconducting polymer nanoparticles for enhanced multimodal cancer phototheranostics

Phototheranostic nanoagents are promising for early diagnosis and precision therapy of cancer. However, their imaging ability and therapeutic efficacy are often limited due to the presence of delivery barriers in tumor microenvironment. Herein, we report the development of organic multimodal phototheranostic nanoagents that can biomimetically target cancer-associated fibroblasts in tumor microenvironment for enhanced multimodal imaging-guided cancer therapy. Such biomimetic nanocamouflages comprise a near-infrared (NIR) absorbing semiconducting polymer nanoparticle (SPN) coated with the cell membranes of activated fibroblasts. The homologous targeting mechanism allows the activated fibroblast cell membrane coated SPN (AF-SPN) to specifically target cancer-associated fibroblasts, leading to enhanced tumor accumulation relative to the uncoated and cancer cell membrane coated counterparts after systemic administration in living mice. As such, AF-SPN not only provides stronger NIR fluorescence and photoacoustic (PA) signals to detect tumors, but also generates enhanced cytotoxic heat and single oxygen to exert combinational photothermal and photodynamic therapy, ultimately leading to an antitumor efficacy higher than the counterparts. This study thus introduces an organic phototheranostic system that biomimetically target the component in tumor microenvironment for enhanced multimodal cancer theranostics.MOE (Min. of Education, S’pore)Accepted versio