Effective aerial monitoring of cyanobacterial harmful algal blooms is dependent on understanding cellular migration

Cyanobacterial harmful algal blooms (CHABs) degrade water quality and may produce toxins. The distribution of CHABs can change rapidly due to variations in population dynamics and environmental conditions. Biological and ecological aspects of CHABs were studied in order to better understand CHABs dynamics. Field experiments were conducted near Hartington, Ontario, Canada in ponds dominated by Microcystis aeruginosa and CHABs floating experiments were conducted at Lake Taihu during the summers of 2015 and 2016. Single colonies composed of hundreds to thousands of cells with an average median of 0.2–0.5 mm in diameter were the basic form assumed by the Microcystis, and this remained the same throughout the growing season. Thorough mixing of the water column followed by calm conditions resulted in over 90% of the cyanobacteria floating after 1 h. Multiple colonies floated on the water surface in four types of assemblages: aggregates, ribbons, patches, and mats. It is the mats that are conventionally considered the blooming stage of cyanobacteria.Presence of CHABs on open water surfaces also depends on environmental influences such as direct and indirect wind effects. For example, field tests revealed that the surface coverage of CHABs can be reduced to half within an hour at wind speeds of 0.5 m/s.Because our findings indicated that blooming involves surface display of cyanobacteria essentially presenting as a two-dimensional plane under defined conditions, the use of surface imagery to quantify CHABs was justified. This is particularly important in light of the fact that traditional detection methods do not provide accurate distribution information. Nor do they portray CHABs events in a real-time manner due to limitations in on-demand surveillance and delays between sample time and analyzed results. Therefore, a new CHAB detection method using small unmanned aerial systems with consumer-grade cameras was developed at a maximum detection altitude of 80 m. When cyanobacteria were floating on the surface, CHABs detection through RGB band cameras and spectral enhancement techniques was efficient and accurate. Small unmanned aerial systems were capable of providing coverage up to 1 km² per mission and the short intervals between sampling and results (approx. 2 h) allowed for the rapid analysis of data and for implementing follow-up monitoring or treatments. This method is very cost-effective at an estimate of as low as $100 CAD per mission with an average cyanobacterial detection accuracy of 86%. Thus, it is a good candidate method to fill the urgent need for CHABs detection, providing cost effective, rapid, and accurate information to improve risk management at a local level as well as to help quickly allocate resources for purposes of mitigation.     

木麻黄海防林种子雨的时空动态

为了解木麻黄(Casuarina equisetifolia)种子雨的时空间分布格局和萌发性能对其天然更新的影响,对海口木麻黄海防林种子雨的时空分布特征和种子雨的萌发动态进行了研究。结果表明,木麻黄种子落雨时间始于7月中旬,结束于次年4月中旬,持续长达9个月,期间种子雨年际平均密度为1 764.63 grain m~(-2)a~(-1);种子雨高峰期在12月上中旬,落种量占总散落量的43.38%;种子雨呈聚集分布,且种子雨密度与附近球果数量呈极显著正相关;种子雨萌发率较低,仅为11.31%,但由于种子雨密度较大,可萌发的种子雨密度仍然较大,为199.58grainm~(-2)a~(-1)。因此,种子数量和质量均不是制约木麻黄天然更新困难的主要障碍因子,但聚集分布特征使木麻黄种子在林内扩散能力十分有限。     

Influence of Stimuli Spatial Proximity on a SSVEP-Based BCI Performance

Objective: Steady-State Visual Evoked Potentials based Brain-Computer Interfaces (SSVEP-based BCIs) systems have been shown as promising technology due to their short response time and ease of use. SSVEP-based BCIs use brain responses to a flickering visual stimulus as an input command to an external application or device, and it can be influenced by stimulus properties, signal recording, and signal processing. We aim to investigate the system performance varying the stimuli spatial proximity (a stimulus property).Material and methods: We performed a comparative analysis of two visual interface designs (named cross and square) for an SSVEP-based BCI. The power spectrum density (PSD) was used as feature extraction and the Support Machine Vector (SVM) as classification method. We also analyzed the effects of five flickering frequencies (6.67, 8.57, 10, 12 e 15 Hz) between and within interfaces.Results: We found higher accuracy rates for the flickering frequencies of 10, 12, and 15 Hz. The stimulus of 10 Hz presented the highest SSVEP amplitude response for both interfaces. The system presented the best performance (highest classification accuracy and information transfer rate) using the cross interface (lower visual angle).Conclusion: Our findings suggest that the system has the highest performance in the spatial proximity range from 4° to 13° (visual angle). In addition, we conclude that as the stimulus spatial proximity increases, the interference from other stimuli reduces, and the SSVEP amplitude response decreases, which reduces system accuracy. The inter-stimulus distance is a visual interface parameter that must be chosen carefully to increase the efficiency of an SSVEP-based BCI.     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.     

Influence of the physical environment and conspecific aggression on the spatial arrangement of breeding grey seals

Understanding the habitat requirements of a species for breeding is essential for its conservation, particularly if the availability of suitable habitat is a limiting factor for population growth. This is postulated to be the case for grey seals, one of the more abundant marine apex predators in northern European waters. In common with similar studies that have investigated the habitat preferences of breeding grey seals, we use abiotic (topographical, climatological) attributes but, unlike previous work, we also incorporate behavioural variables, particularly the occurrence of aggressive interactions between females and the presence of neighbouring seals. We used two Generalized Additive Models (GAM) in a sequential and iterative fashion. The first model links the occurrence of aggression at particular points in the colony to local topography derived from a Geographical Information System (GIS), presence of neighbouring seal pups and the day of the breeding season. The output of this GAM is used as one of the explanatory variables in a GAM of daily variation in the spatial distribution of births. Although proximity of a birth site to a water source and the presence of neighbouring seal pups both had significant influences on the distribution of newborn pups over time and space, at the scale of the study site it was found that simple rules could predict pup distribution more efficiently than a complex individual-based simulation model.     

Molecular network strategy in multi-omics and mass spectrometry imaging

Human physiological activities and pathological changes arise from the coordinated interactions of multiple molecules. Mass spectrometry (MS)-based multi-omics and MS imaging (MSI)-based spatial omics are powerful methods used to investigate molecular information related to the phenotype of interest from homogenated or sliced samples, including the qualitative, relative quantitative and spatial distributions. Molecular network strategy provides efficient methods to help us understand and mine the biological patterns behind the phenotypic data. It illustrates and combines various relationships between molecules, and further performs the molecule identification and biological interpretation. Here, we describe the recent advances of network-based analysis and its applications for different biological processes, such as, obesity, central nervous system diseases, and environmental toxicology.     

Using niche modelling and human influence index to indicate conservation priorities for Atlantic forest deer species

To prioritise conservation actions and management strategies for threatened forest deer species at the Atlantic forest, we aimed to identify and describe the most suitable habitat areas for forest deer species and to indicate conservation measures for state agents and local communities. We adopt an approach based on ecological niche modelling, key variable thresholds and spatial analyses. In addition, we associated our approach with a human influence index, an invasive species dataset of occurrences, protected area cover and IUCN category. We indicate 2 % (484 km²) of the Atlantic forest cover as conservation priority areas (CPAs). Of these, 56.8 % are outside protected areas, 20.7 % are inside IUCN categories i, ii and iii protected areas, 19.9 % are inside IUCN categories iv, v, and vi protected areas, and 2.6 % are inside indigenous areas. Also, we indicate the most relevant protected areas for deer conservation in the Atlantic forest. The CPAs were classified into more human-influenced areas (MHIA) and less human-influenced areas (LHIA), and we identified 21 significant (greater than120 km²) continuous CPAs outside protected areas. We highlight actions in several perspectives of human influence, governance levels and law protection that would rationalise the use of funds and human resources.     

Temporal annotation of high-resolution intra-annual wood density information of Eucalyptus urophylla and its correlation with hydroclimatic conditions

Three different Eucalyptus urophylla clones grown under two different spacing regimes in an experimental site in the state of São Paulo, Brazil, were analyzed to test effects of clone identity, spacing, cambial age and hydroclimatic conditions on high-resolution intra-annual wood density profiles. Since distinct periodic tree-ring boundaries were not visible on the stem cross-sectional surfaces, finding an alternative method for synchronization of density profiles was crucial for the analysis. The challenge was to generate intra- and inter-tree synchronized density profiles that possess high amplitude variation and low phase variation. Thus, we developed a protocol and workflow of how such high-resolution density profiles can be spatially aligned and temporally annotated to enable correlation analyses between trees and with time series of environmental stimuli. Mean wood density was significantly different between clones, but not between the spacings. Wood density increased significantly with increasing cambial age and decreasing growth rate. Principal component analysis showed that the overall variability in the temporally annotated density profiles is dominated by a highly significant common signal. We found significant negative correlation values for precipitation, indicating that water supply is the main driver of stem growth at the site, and providing evidence for the correctness of the method. The developed workflow can easily be adjusted to the analysis of other intra-annual tree-ring features like anatomical xylem cell traits or isotopic signals in the wood. It has a large potential to be used as a general guideline for the synchronization of intra-annual tree-ring traits, especially when distinct tree-ring boundaries are missing, as it is often the case under tropical climatic conditions. The workflow supports the development of spatially aligned and temporally annotated chronologies under non-annual growth rhythms.     

Mapping the spatial variation of mitral valve elastic properties using air-pulse optical coherence elastography

The mitral valve is a highly heterogeneous tissue composed of two leaflets, anterior and posterior, whose unique composition and regional differences in material properties are essential to overall valve function. While mitral valve mechanics have been studied for many decades, traditional testing methods limit the spatial resolution of measurements and can be destructive. Optical coherence elastography (OCE) is an emerging method for measuring viscoelastic properties of tissues in a noninvasive, nondestructive manner. In this study, we employed air-pulse OCE to measure the spatial variation in mitral valve elastic properties with micro-scale resolution at 1 mm increments along the radial length of the leaflets. We analyzed differences between the leaflets, as well as between regions of the valve. We found that the anterior leaflet has a higher elastic wave velocity, which is reported as a surrogate for stiffness, than the posterior leaflet, most notably at the annular edge of the sample. In addition, we found a spatial elastic gradient in the anterior leaflet, where the annular edge was found to have a greater elastic wave velocity than the free edge. This gradient was less pronounced in the posterior leaflet. These patterns were confirmed using established uniaxial tensile testing methods. Overall, the anterior leaflet was stiffer and had greater heterogeneity in its mechanical properties than the posterior leaflet. This study measures differences between the two mitral leaflets with greater resolution than previously feasible and demonstrates a method that may be suitable for assessing valve mechanics following repair or during the engineering of synthetic valve replacements.