Relative Biomass Research Articles

Chub Mackerel (Scomber colias) Population Dynamics in the Atlantic Iberian Waters: Use of Long‐Term Regional Data for a Data‐Limited Fishery Scomber colias

ABSTRACTThe Atlantic chub mackerel (Scomber colias) became an important resource in purse‐seine fisheries of the Iberian Peninsula in the mid‐2000s. Being data‐limited at the stock level, 60 years of landings and 40 years of bottom‐trawl survey data were available for part of the area. A biomass model fitted to landings and survey data performed well under the assumption of homogeneous dynamics across the stock area. During 1993–2020, relative stock biomass was above potential reference points with wave‐like variation and peaks in 1995 and 2008. Credible intervals of relative fishing mortality indicated that exploitation may have been unsustainable since 2012. Chub mackerel productivity increased from the 1980s to the 1990s, possibly due to decreased sardine predation and competition and increased larval growth. The approach we used demonstrated how information from a portion of a stock's distribution area can be utilised for stock assessment, to potentially prevent neglect of stock data or alteration of management units.

Nickel tolerance in cool‐season grasses

AbstractNickel (Ni) toxicity is becoming more prevalent in plants and soils due to increased use of sewage sludge as fertilizers and wastewater irrigation applications; therefore, research on the tolerance of cool‐season turfgrasses and other grassy species is needed. Annual bluegrass (Poa annua L.) is one of most prevalent annual grassy weeds on fine turf worldwide. This research was conducted to examine Ni tolerance of two creeping bentgrass (Agrostis stolonifera L.) cultivars Seaside II and PennLinks II plus a mixture of annual bluegrass and perennial ryegrass (Lolium perenne L.) grown in pure sand and treated with six different Ni concentration levels supplied as NiSO4·6H2O (control, 200, 400, 800, 1600, and 3200 µg L−1 of Ni). Grasses were assessed based on quality, normalized difference vegetation index (NDVI), relative clipping biomass, relative root biomass, relative total biomass, and plant tissue Ni concentration. All measured parameters decreased, and toxicity symptoms followed by growth reductions were noted for all grasses as Ni concentrations increased. Seaside II and PennLinks II at Ni concentrations of 400 and 800 µg L−1 were noted to be at acceptable turf quality or higher, when weedy species mixture was below the acceptable grass quality level. Seaside II displayed acceptable turf quality even at 1600 µg L−1 of Ni. At 3200 µg L−1 of Ni, PennLinks II and weedy species mixture were necrotic at the conclusion of the 8 weeks of the study compared to Seaside II, which was actively growing with signs of yellowing. Results illustrate genetic differences in Ni tolerance, and Seaside II, a salt‐tolerant creeping bentgrass cultivar, has stronger Ni toxic concentration tolerance than PennLinks II and a mixture of two annual weedy grass species, which are often found in the transition zone. This may explore potentials of more research on micronutrient management of weedy species.

Remote sensing reveals the role of forage quality and quantity for summer habitat use in red deer

BackgroundThe habitat use of wild ungulates is determined by forage availability, but also the avoidance of predation and human disturbance. They should apply foraging strategies that provide the most energy at the lowest cost. However, due to data limitations at the scale of movement trajectories, it is not clear to what extent even well-studied species such as red deer (Cervus elaphus) trade-off between forage quality and quantity, especially in heterogeneous alpine habitats characterized by short vegetation periods.MethodsWe used remote sensing data to derive spatially continuous forage quality and quantity information. To predict relative nitrogen (i.e. forage quality) and biomass (i.e. forage quantity), we related field data to predictor variables derived from Sentinel-2 satellite data. In particular, our approach employed random forest regression algorithms, integrating various remote sensing variables such as reflectance values, vegetation indices and optical traits derived from a radiative transfer model. We combined these forage characteristics with variables representing human activity, and applied integrated step selection functions to estimate sex-specific summer habitat selection of red deer in open habitats within and around the Swiss National Park, an alpine Strict Nature Reserve.ResultsThe combination of vegetation indices and optical traits greatly improved predictive power in both the biomass (R2 = 0.60, Root mean square error (RMSE) = 88.55 g/m2) and relative nitrogen models (R2 = 0.34, RMSE = 0.28%). Both female and male red deer selected more strongly for biomass (estimate = 0.672 ± 0.059 SE for normalised values for females, and 0.507 ± 0.061 for males) than relative nitrogen (estimate = 0.124 ± 0.062 for females, and 0.161 ± 0.061 for males, respectively). Females showed higher levels of use of the Swiss National Park.ConclusionsRed deer in summer habitats select forage quantity over quality with little difference between sexes. Females respond more strongly to human activities and thus prefer the Swiss National Park. Our results demonstrate the capability of satellite data to estimate forage quality and quantity separately for movement ecology studies, going beyond the exclusive use of conventional vegetation indices.

Effects of different eco-stoichiometric ratios of calcium and cadmium on the detoxification mechanisms of Capsicum annuum L. under cadmium stress.

The eco-stoichiometry of Ca/Cd in soil significantly affects Cd uptake and accumulation by plants in carbonate regions. In this study, the physiological responses and detoxification mechanisms of Capsicum annuum L. (capsicum) were investigated based on the eco-stoichiometric relationship of Ca/Cd in production substrates under varying pH levels (5, 6, and 7). The results revealed that increased Ca/Cd ratio enhanced the Cd accumulation in roots at pH values of 5 and 6. The enrichment of Cd in stems and leaves gradually decreased with varying Ca/Cd ratios at different pH levels. In addition, root vigor, relative chlorophyll content, biomass, and catalase and peroxidase activities increased across various pH levels, while the concentration of protein carbonyl and malondialdehyde decreased. The ability of pectin and cellulose in the cell wall and that of soluble components within the cell to adsorb and partition Cd improved as the Ca/Cd ratio increased at different pH values. Notably, the effects of varying Ca/Cd ratios were most significant at pH 6. Overall, Ca enhanced the tolerance of capsicum to Cd stress, thereby promoting the fixation of Cd in root cells, reducing its transfer to aboveground tissues, and improving both the growth and antioxidant stress response. The effect was attributed to different Ca/Cd stoichiometric ratios, pH levels, and their interactions. These findings enhance the understanding of the mechanism of the interaction between Ca and Cd on crops in the karst agroecosystem.

Threshold responses of freshwater fish community size spectra to invasive species

AbstractAquatic invasive species (AIS) threaten biodiversity and ecosystem services around the world, but their management has been hampered by the lack of quantifiable control targets. The introduction of Silver Carp (Hypophthalmichthys molitrix) throughout the mid‐western United States epitomizes both the impacts of AIS and the need for quantitative control targets. Silver Carp are large‐bodied planktivores that compete with native planktivores, which can cause cascading effects throughout the food web. Our study tested the threshold of abundance beyond which Silver Carp alter fish assemblage structure. We used a community size spectra (CSS) approach to evaluate fish community size structure across temporal and spatial gradients of Silver Carp abundances. We hypothesized that Silver Carp would flatten the size spectra slope because they are large‐bodied and feed at a low trophic position. Electrofishing data were obtained for the La Grange Pool of the Illinois River (1994–2021) and for six pools of the Ohio River (2015–2020). Results supported our hypothesis, showing a 98% probability that the relative biomass of Silver Carp is positively related to the CSS slope (resulting in “flattening”). This pattern was strongest in the Illinois River, where Silver Carp made up >30% of fish assemblage biomass in recent years. The pattern was weakest in the Ohio River (78% probability of a positive relationship) where Silver Carp rarely exceeded 20% of total fish biomass. Subsequent changepoint models indicated that a Silver Carp relative biomass of ~24% represents a threshold below which negative food web impacts should be minimized. Our study demonstrates a clear shift in fish community size structure following invasion by Silver Carp and suggests that pre‐invasion CSS slopes may serve as a restoration target. It also illustrates the benefits of CSS to guide Silver Carp and other AIS management.

Accounting for post-release mortality in data-limited, length-based assessments for four demersal fish species with varying life histories

Released (or discarded) fish from recreational and commercial line fisheries can experience significant levels of post-release mortality (PRM), affecting sustainability. Although PRM effects are often considered in data-rich (integrated model) assessments, this is uncommon in data-limited assessments. This study investigates impacts of PRM when applying data-limited, length-based assessment methods for four reef-dwelling demersal fish species in temperate Western Australia (Glaucosoma hebraicum, Chrysophrys auratus, Choerodon rubescens and Epinephelides armatus). These species differ considerably in their biology and susceptibility to PRM. For each species simulations were undertaken to (1) evaluate the reliability of a length-based catch curve (LBCC) method for estimating fishing mortality (F) and selectivity parameters, and (2) predict the impacts of different PRM levels on values of relative biomass, i.e. ratios of fished to unfished equilibrium spawning biomass (Brel), estimated using a length-based equilibrium analysis (LBEA). LBEA extends length-based per-recruit analysis to incorporate a stock-recruitment relationship as well as allow for PRM. On average, estimates of F and selectivity parameters from LBCC for each species were unbiased when applied to simulated data. Precision decreased, however, when LBCC was fitted to data simulated with recruitment variation. For a given F, increased PRM levels reduced Brel for all species, with the extent of impacts varying depending on species biology. LBCC was then applied to two actual datasets, firstly to lengths for all fish that had either been retained or released during historical recreational fishing trips (to estimate gear selectivity), and secondly to length data for retained fish from recent charter fishing (to estimate F and selectivity of landings). The resultant estimates were then used in LBEA to estimate Brel with and without accounting for PRM. Relative impacts of PRM varied among species depending on their biology and size limits. While PRM was predicted to have limited impact on Brel for C. rubescens (as fish are not fully selected by the gear until they attain a relatively large size), accounting for PRM resulted in estimates of Brel (at their current estimated F levels) being reduced by 31 % for G. hebraicum, 36 % for C. auratus and 23 % for E. armatus. It is recommended that, where evidence of PRM exists for a species, this be accounted for in data-limited assessments.

Bottom depth carving the pelagic spatial organisation in large marine ecosystem: The case of North West Africa

This study aimed to examine the spatial organization of pelagic communities within the water column along a horizontal gradient extending from the coast to the offshore area, categorized into three zones: inshore, offshore, and transition. Using fisheries acoustics, a total of 29 000 nautical miles of acoustic transects collected during 14 annual standardized surveys were analyzed using two complementary acoustic methods: (i) extraction of sound scattering layers (SSL) and (ii) echointegration (EI) across the entire water column, both horizontally and vertically averaged. The results revealed significant differences between the three bathymetric areas based on SSL and EI descriptors, with micro-nektonic communities in the transition area exhibiting intermediate characteristics between those in the inshore and offshore areas. The relative abundance of micro-nektonic communities decreased from shallow coastal areas to deep offshore areas, with a mean Sv from echointegration of −66.43, −74.39 and −73.65 dB for inshore, transition and offshore, respectively. The inshore area is different from the transition and offshore areas, which is confirmed by diel vertical migration (DVM) analyze through vertical profiles. All areas exhibited classic DVM type I; however, offshore and transition areas also presented unexpected DVMs of type II, i.e., organisms descend deeper during the night, displaying distinct vertical profiles compared to the inshore area. This suggests that the functional and specific composition of pelagic micro-nektonic communities differed between inshore and offshore areas, indicating that organisms adjust their responses to their environment. Over two decades, the three bathymetric areas showed a significant increase in pelagic relative biomass and variation in SSL spatial structure. The number of SSLs significantly increase, from 0.97 to 1.05 inshore, from 1.75 to 2.25 in the transition area and from 2.2 to 2.7 offshore. Nevertheless, micro-nektonic communities reacted differently to interannual changes depending on the bathymetric areas, such as the minimal depth of the shallowest SSL. Fluctuations in SSL descriptors were highlighted over the study period, which may be related to multi-decadal oscillations in the Atlantic Ocean.

Effect of arbuscular mycorrhiza and rhizobium on physiology and yield of peanut under drought conditions.

Drought is the one primary issue limiting peanut growth and productivity. The study aimed to investigate the effects of arbuscular mycorrhizal fungi (AMF), rhizobium (Rhi), and their combinations on phenolic content, proline content, growth, and yield of peanut under different soil water regimes. The pot experiments were carried out for two growing seasons under greenhouse conditions and designed based on a 2×3 factorial in randomized complete block design (RCBD) with four replications. Factor A comprised two soil water regimes: field capacity (FC) and 1/3 available soil water (1/3 AW), whereas factor B included three different types of microorganisms: (i) uninoculated control, (ii) arbuscular mycorrhiza (AMF), and (iii) a combination of AMF and rhizobium (Rhi) inoculations. Data were collected for growth, proline content, phenolic content, yield, and yield components. Drought stress significantly reduced in relative water content, leaf area, biomass, yield, and yield components of peanut, whereas leaf phenolic content was increased under drought stress. Higher pod dry weight was achieved under FC conditions (28.87g plant-1), and it was reduced to 16.06g plant-1 under 1/3 FC. Interestingly, AMF+Rhi synergistically increased the leaf area compared with non-incubated peanut under 1/3 FC conditions. AMF-inoculated peanut tended to increase biomass, while the combination of AMF+Rhi tended to have higher yield components compared with uninoculated control, especially for the weight of 100 seeds.

Robust vegetation detection using RGB colour composites and isoclust classification of the Landsat TM image

The paper presents the application of ArcGIS for environmental modelling of the landscapes in northern Iceland (17.00°W–23.00°W, 64.30°N–67.00°N). The aim was to explore the vegetation distribution by NDVI and ISOCLUST classification of the land cover types. Data include the Landsat TM image. Freely available satellite remote sensing data from the Landsat mission have been processed by GIS to deliver information on land cover types from image classification and NDVI vegetation index. Landsat products provide geospatial data on regional scale with moderate temporal (weekly) and spatial (30–10 m) resolution, making them useful for environmental monitoring and landscape studies. The tools include the ArcGIS software used for raster processing. Data processing was performed in the three steps: 1) comparative analysis of the visualized sixteen band combinations to assess the distinguishability of vegetation and other land cover types in colour composites; 2) computed NDVI standardized vegetation index; 3) unsupervised classification of the Landsat TM by the ISOCLUST algorithm. Large glaciers Hofsjökull and Langjökull were detected on various colour composites, and the visibility of the water/land borders is assessed (Blöndulón lake), agricultural areas near the Varmahlíð, vegetated areas around the Akrahreppur municipality. Computing the NDVI and using ISOCLUST by ArcGIS software enabled to distinguish various land cover types and map landscapes in the study area. The computed NDVI shown the presence and condition of vegetation, that is, a relative biomass in the area of northern Iceland. The NDVI was used based on the contrast of the two channels from a multispectral Landsat TM raster data.

Impact of Cow Urine and Substrate Composition on Germination and Early Growth of Papaya (Carica papaya L.) Seedlings

Aim: This study evaluates the impact of cow urine and substrate composition on the germination and early growth of papaya (Carica papaya L.) seedlings, a critical phase for successful crop establishment. Study Design and Methodology: Conducted as a factorial experiment, it assessed eleven substrate or growing media combinations with and without cow urine treatment. Results: Results reveal that cow urine significantly reduces the time to 90 percent germination (T90) and enhances the germination index, indicating its stimulatory effect on seed metabolic activity. Treatments combining cow urine with substrates like soil, sand, vermiculite, cocopeat, and perlite (T10) showed the shortest T90 and highest germination index, suggesting cow urine accelerates germination. Additionally, cow urine application improved growth metrics such as relative growth rate (RGR) and total biomass accumulation, with T10 and T8 treatments yielding the highest values. Enhanced leaf relative water content (LRWC) and elevated proline levels in cow urine-treated plants indicate better water retention and stress resilience. Strong positive correlations were observed among proline content, RGR, and biomass accumulation, highlighting cow urine’s contribution to vigorous seedling growth and stress adaptation. Conclusion: The findings suggest that cow urine, in combination with optimized substrates, is a sustainable growth enhancer that promotes robust seedling development, suitable for organic farming practices aimed at papaya cultivation.

Capital and income breeders among herbs: how relative biomass allocation into a storage organ relates to clonal traits, phenology and environmental gradients.

Perennial herbs of seasonal climates invest carbon into belowground storage organs (e.g. rhizomes) to support growth when photosynthetic acquisition cannot cover demands. An alternative explanation interprets storage allocation as surplus carbon that is undeployable for growth when plants are limited by nutrients/water. We analysed relative investments to rhizomes to see to which of these explanations they align, and asked whether they scale with biomass of aboveground organs in individual species and whether clonal growth traits, phenology or environmental conditions explain investment among populations or species. We measured biomass of rhizomes, aboveground stems and leaves in 20 temperate herbaceous perennial species, each at two localities, establishing allometric relationships for pairs of organs. We correlated relative rhizome investment with clonal traits, environmental gradients and phenology, across species. For pairs of organs, biomass typically scales isometrically. Interspecific allocation differences are largely explained by phenology. Neither interspecific nor intraspecific differences were explained by clonal traits or environment. Storage organs of perennial herbs do not comprise deposition of carbon surplus, but receive greater allocation in capital breeders (early-flowering), than among income breeders (late-flowering) relying on acquisition during growing season. Capital and income breeders in plants deserve further examination of benefits/costs.

Chemical composition and influence of essential oil from Croton pulegiodorus Baill. Leaves on the nutrition and survival of Sitophilus zeamais Mots. (Coleoptera: Dryophthoridae) as well as survival and behavior of Nasutitermes corniger Mots. (Blattodea: Termitidae)

Essential oils have been studied to develop sustainable alternatives for controlling pest-species. This study determined the chemical composition and toxicity of an essential oil from Croton pulegiodorus leaves against Sitophilus zeamais and Nasutitermes corniger. Ascaridole (22.75%) and camphor (18.11%) were the major compounds. The essential oil showed toxicity upon ingestion on S. zeamais, with LC50 and LC90 of 24.24 and 46.76 μL/g for 15 days, respectively. It presented a moderate (10.0 and 12.5 μL/g) to strong (15 μL/g) deterrent effect, interfering with nutritional parameters, causing a reduction in the relative consumption rate, relative biomass gain rate and efficiency in conversion of ingested food. Furthermore, it stimulated in vitro S. zeamais β-D-xylanase (+33.39%), endoglucanase (+8.28%), exoglucanase (+84.77%), and α-amylase (+359.18%) activities and reduced in vitro the activity of trypsin-like enzymes (−79.67%). The essential oil showed fumigant effect against N. corniger termites with LC50 and LC90 (24 h) of 0.57 and 3.26 μL/mL of air for workers and 1.63 and 4.74 μL/mL of air for soldiers respectively. In workers, it caused 100% mortality through contact in 2.08 and 0.49 min (at 0.4 μL/μL and neat oil). A significant increase in the number of self-cleaning and falls indicated behavioral changes induced by the oil in N. corniger workers. The study shows the potential of the essential oil of C. pulegiodorus leaves as an alternative method in the management of maize weevil and N. corniger.

Fishery characteristics, population dynamics and the impacts of the invasive red swamp crayfish (Procambarus clarkii) in the Nile River, Egypt

Alien intrusive species are one of the extreme pressures on biodiversity for their rapid reproduction and adaptation to new environments. Crayfish Procambarus clarkii entered Egyptian freshwater ecosystems at the beginning of 1980's. After many years of negative effects of its introduction onto the Egyptian waters, it became one of the commercially important species. Population parameters of P. clarkii are estimated based on 1355 specimens collected from the Nile off El-Minya during 2019–2020. The isometric growth of the species under the study is confirmed according to the obtained b-value of length–weight relationship (LWR). Annual sex ratio (female : male) was in favour of females with an annual sex ratio 1.44 : 1. The values of growth coefficient (K) and the asymptotic total length (L∞) were assessed for males, females and combined sexes. Using mortality estimates, the exploitation ratio was 0.64 year–1. Investigation of relative yield per recruit (Y'/R) and analysis of relative biomass per recruit (B'/R) for P. clarkii in the Nile off El-Minya provides the highest (Y'/R) at Emax = 0.81 and the E0.5 (utilisation level that preserves the spawner stock biomass at 50% of the virgin spawning biomass) was 0.38. From fisheries management point of view, the current exploitation level should be decreased to that maintain the spawning stock biomass (from 0.64 to 0.38).

Effect of the Membrane Insertase YidC on the Capacity of Lactococcus lactis to Secret Recombinant Proteins.

Lactococcus lactis is a crucial food-grade cell factory for secreting valuable peptides and proteins primarily via the Sec-dependent pathway. YidC, a membrane insertase, facilitates protein insertion into the lipid membrane for the translocation. However, the mechanistic details of how YidC affects protein secretion in L. lactis remain elusive. This study investigates the effects of deleting yidC1/yidC2 on L. lactis phenotypes and protein secretion. Compared to the original strain, deleting yidC2 significantly decreased the relative biomass, electroporation efficiency, and F-ATP activity by 25%, 47%, and 33%, respectively, and weakened growth and stress resistance, whereas deleting yidC1 had a minimal impact. The absence of either yidC1 or yidC2 reduced target proteins secretion. Meanwhile, there is a considerable alteration in the transcription levels of genes involved in the secretion pathway, with secY transcription increasing over 135-fold. Our results provide a theoretical foundation for further improving target protein secretion and investigating the YidC function.

A radar backscatter simulation of a forest canopy using 3D physical structures derived from LiDAR scanning

ABSTRACT This study aims to explore the forest aboveground biomass relationship to C-band backscatter. A one-hectare area in Wytham Woods, located west of Oxford, was selected for this research. The area has a total of 525 trees of seven different tree species. The Michigan Microwave Canopy Scattering Model (MIMICS), a two-layer radiative transfer model, was applied to simulate canopy backscatter responses in this deciduous UK forest. Model parameters related to forest structure were derived from previously published terrestrial laser (LiDAR) data. Simulated backscatter was performed for co-polarized and cross-polarized modes at a C-band frequency range and incidence angles (20° to 45° at 5° increments). The research includes five objectives: i) backscatter sensitivity analysis from the variation of different model parameters; ii) backscatter seasonal effect under spring–summer (leaf-on) and autumn–winter (leaf-off) periods; iii) backscatter comparison between species as well as between simulated and satellite observations in a spatial pattern; iv) relationship between simulated backscatter and aboveground biomass; and v) relationship between MIMICS forest structure parameters and simulated backscatter. Sensitivity analysis results showed significant differences in backscatter from changes in leaf distribution, leaf thickness and water content (leaf, trunk and soil) for both polarization modes in leaf-on scenarios. Leaf-off scenarios presented significant differences from changes in branch distribution but only for the co-polarized mode. Seasonal variations presented significant backscatter differences between spring–summer and autumn–winter scenarios; additionally, backscatter differences among species for each seasonality in the co-polarized mode were observed. The computation of the grid resolution (20 m × 20 m) showed a range of backscatter values depending on the grid and incidence angle. Higher backscatter values were observed for the satellite data than for the simulated data. Finally, the aboveground biomass and the MIMICS input parameters presented high random variability and little systematic co-variation with the total backscatter on both simulated seasons, suggesting that more robust allometric equations for biomass estimation are required.

Is the population of kingfish (Scomberomorus commerson) in the northern Persian Gulf really under pressure from overfishing?

AbstractQuantifying the population dynamics of marine species is difficult when good, comprehensive data are not available. We sought to determine if the kingfish Scomberomorus commerson stock in the Persian Gulf was overfished. The ICES data‐limited assessment framework was used to provide precautionary advice, with a 20% decrease advised in situations where only catch or bycatch data were available. The length‐based Bayesian biomass (LBB) was used to model fork length from landing records of licensed fishers in the Khuzestan Province during 2002–2018, which had increased despite sought being overexploited. Most kingfish were immature and smaller than optimum length of the catch (Lc‐opt = 88 cm) and optimum length (Lopt = 104 cm). Relative biomass (B/Bmsy) ranged 0.62–0.66 and exceeded 0.5. The B/Bmsy ratio (1.25) was >1.1. The stock appeared to be healthy and exploitable, but wide confidence intervals of the B/Bmsy ratio complicated interpretation of stock status. The kingfish stock appeared to use waters of the study area as a spawning and nursery ground, so many young immature individuals were present. If current exploitation of young individuals continues, this the stock will eventually be overfished. Long‐term increases in the catch of young immature kingfish can have a side effect on stock maturation and recruitment. We recommend that the mesh size of fishing gear be selected based on optimum length, to enhance economic, and commercial viability of the kingfish fishery.

Ecosystem Size Drives Patterns and Control Mechanisms of Mixotrophs Success Across Tropical Lakes: A Large-Scale Assessment of the Grand Écart Hypothesis

Mixotrophy, a physiological trait combining autotrophy and heterotrophy in one organism, significantly contributes to energy and matter transfer in aquatic ecosystems. However, understanding how environmental factors influence mixoplankton success across freshwater ecosystems has been uncertain. The grand écart hypothesis (GEH) posits that light and nutrient availability are key components of mixotrophs' niche, suggesting that ecosystem properties determine opposing gradients of light and nutrients, creating environmental filtering for mixotrophs. We hypothesized that ecosystem size, a property of lake ecosystems, mediates the prevalence of patterns and control mechanisms predicted by the GEH on mixoplankton relative biomass (MRB). Using data from 98 tropical lakes, we demonstrated that lake size mediates the inverse relationship between light and nutrient availability across ecosystems. Larger lakes have more light but low nutrients, while smaller lakes have more nutrients but greater shading. Light availability better explains MRB in small lakes, and nutrients better explain MRB in large lakes, with MRB values being higher in small lakes, with secondary influence from zooplankton herbivory. Our results validate the GEH as a significant framework for explaining patterns and control mechanisms of mixoplankton across tropical lakes. This study highlights the significance of lake size as an ecosystem property that generates opposing light and nutrient gradients, further emphasizing its importance for understanding mechanisms regulating freshwater phytoplankton community structure and functioning. Integrating lake size within the conceptual framework of the GEH could aid in explaining mixoplankton success over macroecological scales.

Managing nutrition-biodiversity trade-offs on coral reefs

Coral reefs support an incredible abundance and diversity of fish species, with reef-associated fisheries providing important sources of income, food, and dietary micronutrients to millions of people across the tropics. However, the rapid degradation of the world's coral reefs and the decline in their biodiversity may limit their capacity to supply nutritious and affordable seafood while meeting conservation goals for sustainability. Here, we conduct a global-scale analysis of how the nutritional quality of reef fish assemblages (nutritional contribution to the recommended daily intake of calcium, iron, and zinc contained in an average 100g fish on the reef) relates to key environmental, socioeconomic, and ecological conditions, including two key metrics of fish biodiversity. Our global analysis of more than 1,600 tropical reefs reveals that fish trophic composition is a more important driver of micronutrient concentrations than socioeconomic and environmental conditions. Specifically, micronutrient density increases as the relative biomass of herbivores and detritivores increases at lower overall biomass or under high human pressure. This suggests that the provision of essential micronutrients can be maintained or even increase where fish biomass decreases, reinforcing the need for policies that ensure sustainable fishing, and that these micronutrients are retained locally for nutrition. Furthermore, we found a negative association between micronutrient density and two metrics of fish biodiversity, revealing an important nutrition-biodiversity trade-off. Protecting reefs with high levels of biodiversity maintains key ecosystem functions, whereas sustainable fisheries management in locations with high micronutrient density could sustain the essential supply of micronutrients to coastal human communities.

Use of Phenomics in the Selection of UAV-Based Vegetation Indices and Prediction of Agronomic Traits in Soybean Subjected to Flooding

Flooding is a frequent environmental stress that reduces soybean growth and grain yield in many producing areas in the world, such as the United States, Southeast Asia, and Southern Brazil. In these regions, soybean is frequently cultivated in lowland areas in crop rotation with rice, which provides numerous technical, economic, and environmental benefits. In this context, the identification of the most important spectral variables for the selection of more flooding-tolerant soybean genotypes is a primary demand within plant phenomics, with faster and more reliable results enabled using multispectral sensors mounted on unmanned aerial vehicles (UAVs). Accordingly, this research aimed to identify the optimal UAV-based multispectral vegetation indices for characterizing the response of soybean genotypes subjected to flooding and to test the best linear model fit in predicting tolerance scores, relative maturity group, biomass, and grain yield based on phenomics analysis. Forty-eight soybean cultivars were sown in two environments (flooded and non-flooded). Ground evaluations and UAV-image acquisition were conducted at 13, 38, and 69 days after flooding and at grain harvest, corresponding to the phenological stages V8, R1, R3, and R8, respectively. Data were subjected to variance component analysis and genetic parameters were estimated, with stepwise regression applied for each agronomic variable of interest. Our results showed that vegetation indices behave differently in their suitability for more tolerant genotype selection. Using this approach, phenomics analysis efficiently identified indices with high heritability, accuracy, and genetic variation (>80%), as observed for MSAVI, NDVI, OSAVI, SAVI, VEG, MGRVI, EVI2, NDRE, GRVI, BNDVI, and RGB index. Additionally, variables predicted based on estimated genetic data via phenomics had determination coefficients above 0.90, enabling the reduction in the number of important variables within the linear model.

Assessment of Suitable Growth Condition of Salvinia spp. for Sustainability of Floating Agriculture to Mitigate Climate Change Challenges on Crop Cultivation

Floating agriculture is an indigenous cultivation practice in the southern waterlogged areas of Bangladesh. Water hyacinth and other macrophytes were utilized in this agricultural method to prepare the floating bed. Among the numerous macrophytes used as mulch in floating beds, Salvinia spp. is a common species. To meet the local farmer's demand, it is necessary to improve the growth rates of these macrophytes so that they can be available year-round for preparing floating beds. For this purpose, an experiment was conducted to assess the growth conditions of Salvinia spp. under various nutritional media. Salvinia molesta and Salvinia cucullata were cultivated in four healthy media to carry out the experiment. The experimental design used in the present investigation was a split-plot arrangement in a Randomized Block Design (RBD), where four nutrients (NO3-; PO43-; NH4+ and Urea) were assigned to the main plots, while five different concentrations of nutrient (0, 1, 5, 10 and 15 mM) were given to the sub-plots. Salvinia spp. growth was examined in terms of morphological and physiological responses and the distribution of nutrients. The highest relative growth rate (RGR) and biomass production (g DW) were found in the medium with one mM and five mM PO43- in the case of S. molesta and one mM NH4+ in the case of S. cucullata. It was also observed that the plant growth rate became suppressed when this macrophyte grew above the 5mM of nutrient concentration, and this suppressed condition turned into a toxic state when the organic nutrient concentration reached a concentration of 15 mM or above. In the case of Urea, this harmful condition starts with a concentration of 5 mM or more for S. molesta and any concentration for S. cucullata.Nonetheless, very few variations were found in how various plant tissues and species absorbed mineral concentrations. The overall findings from this experiment indicate that both PO43- and NH4+ concentrations of 1 mM and 5 mM are comparatively more suitable than NO3- and Urea for the growth and multiplication of Salvinia spp. However, more research is required in addition to varying the quantities of phosphate and ammonium to make a definitive choice. J. of Sci. and Tech. Res. 5(1): 53-62, 2023