Search Results (44)

Juglans neotropica Diels, an Andean native species classified as endangered by the IUCN, holds significant potential for reforestation and sustainable forest management programs. This study evaluated seed quality, phenotypic variability, and early establishment under nursery and field conditions in southern Ecuador. Three provenance sites—The Tundo, The Victoria, and The Argelia—were evaluated during the nursery phase, and two (The Tundo and The Victoria) in plantations, applying four pre-germination treatments: control, mechanical scarification, hot water, and water-sun exposure. Parameters assessed included seed weight, size, viability, germination, survival, and growth across three planting environments: secondary forest, riparian forest, and pasture. Significant differences in seed morphometry were observed among localities, while germination was influenced by treatment but not provenance. Seed viability remained high for up to six months, decreasing with a 2% loss of moisture. Survival reached 100% with urea application, and 96% of individuals exhibited straight stems after one year. No significant differences in growth were found between localities; however, basal diameter was highest in the pasture (13.2 mm/year⁻¹), and total height was greatest in the secondary forest (54.8 cm/year⁻¹). These findings provide key technical evidence to optimize the propagation and establishment of J. neotropica in ecological restoration and forest production contexts. Full article

Recent studies have emphasized the diel nature of dissolved CO₂ (pCO₂) in lake systems; however, around the world, field measurements have been conducted at different times, and it is not clear how, and to what extent, this variable sampling time affects CO₂ emission (FCO₂). This research aimed to investigate whether 10:00 am. was an effective time for lake field sampling to capture 24 h mean pCO₂ and FCO₂ from subtropical eutrophic shallow lake systems. To accomplish this goal, our study compiled long-term data from three individual studies on a shallow lake system in southeast Louisiana, USA. The data comprised samples collected across three-hour intervals, seasonally, over five years. This study highlights that a lake system can function as a carbon sink during peak daylight hours and can shift to a source overnight to early morning. The findings from the longer-term data confirmed 9:00 am to 11:00 am as the time range when pCO₂ deviation from the daily mean is at its lowest (111% of the daily mean). Sampling outside of this time range resulted in an increase in FCO₂ (32.09 mmol m⁻² h⁻¹) of up to 271% (87.03 mmol m⁻² h⁻¹) in overnight samples, with daytime measurements of FCO₂ flipping the lake from source to sink sequestering −20.17 mmol m⁻² h⁻¹. Based on our findings, we strongly recommend that future studies in similar aquatic systems utilize the 9:00–11:00 am timeframe for field sampling to increase the accuracy and compatibility of shared data in carbon emission estimation. Full article

(1) Background: Juglans neotropica Diels, native to the Andes, is highly valued for its quality wood, medicinal uses, edible fruits, and natural dyes. However, its population has been greatly reduced due to overexploitation, becoming threatened and resulting in genetic stochasticity. Therefore, a prompt ex situ and in situ conservation effort is needed for its conservation and restoration. (2) Methods: A total of 439 trees of J. neotropica Diels were sampled from selected individuals across the northern and central regions of Ecuador. These trees were planted in a randomized complete block design to assess their growth and genetic variability. (3) Results: Annual average tree growth varied significantly among progenies. Based on their dasometric traits, two distinct groups were identified as superior and surveillance. Five trees demonstrated promising traits (TJ182, ChL2314, ChL142, TJ1310, and BSM14), suggesting potential for inclusion in forest genetic improvement programs. (4) Conclusions: Fifteen percent of individuals from the five studied provenances exhibited desirable dasometric characteristics and high-quality wood. In addition, several individuals within the progenies exhibit resistance to biotic agents, indicating a genetic potential for disease. Full article

Thermal refuges in streams are essential for the survival of coldwater fish species such as Redband trout (Oncorhynchus mykiss) in landscapes with stressful or lethal stream temperatures. We utilized an uncrewed aerial system (UAS) mounted with thermal and natural color sensors to conduct hourly flights over a 24 h period in the desert stream Little Jacks Creek during late summer when temperatures were near seasonal maximums and streamflow was near seasonal minimums. We used fine-resolution imagery to map stream temperatures and characterize how our thermal sensor exhibits variability across a diel period in an environment where thermal sensor viability had not yet been assessed. Thermal imagery from 3 out of 24 flights showed no significant differences when compared to true water temperatures from in-stream temperature loggers, which appeared to be highly dependent on atmospheric conditions. The thermal imagery (range of $9.17$ to $21.04 °$C) consistently underestimated HOBO logger stream temperatures (range of $13.6$ to $17.1 °$C) during cooler, nighttime flights and overestimated temperatures during hotter, afternoon hours, resulting in a global RMSE of 2.12 $°$C. Between-flight RMSE values ranged from 0.53$°$C to 4.00$°$C, within the error range of the thermal sensor. The thermal data support existing findings of optimal hours for flying UAS thermal surveys and showed specific patterns in TIR sensor accuracy that were dependent on the time of flight. This study yields valuable lessons for future stream temperature data collection in environments with highly variable temperatures, aiding in the calibration of thermal sensors on UAS missions. Furthermore, our results provide insights into environmental stressors such as increased stream temperatures, which is vital for conservation efforts for organisms that rely on coldwater refuges within desert streams. Full article

Vaccinium mandarinorum Diels, a wild blueberry species distributed in the south of the Yangtze River in China, holds significant ecological and commercial value. Understanding its potential distribution and response to climate change is crucial for effective resource utilization and scientific introduction. By using the Maximum Entropy (MaxEnt) model, we evaluated V. mandarinorum’s potential distribution under current (1970–2000) and future climate change scenarios (2041–2060, 2061–2080, and 2081–2100) based on 216 modern distribution records and seven bioclimatic variables. The results showed that the MaxEnt model could effectively simulate the historical distribution and suitability degree of V. mandarinorum. The top two major environmental variables were precipitation of the driest quarter and annual precipitation, considering their contribution rates of 61.3% and 23.4%, respectively. Currently, the high suitability areas were mainly concentrated in central and northern Jiangxi province, central and southern Zhejiang province, southern Anhui province, central and northern Fujian province, and the border areas of Hunan and Guangxi provinces, covering 21.5% of the total suitable area. Future projections indicate that habitat will shift to higher latitudes and altitudes and that habitat quality will decline. Strategies are required to protect current V. mandarinorum populations and their habitats. The study results could provide an important theoretical reference for the optimization of planting distribution and ensure the sustainable production of the blueberry industry. Full article

Adaptive movement in response to individual interactions represents a fundamental evolutionary solution found by both unicellular organisms and metazoans to avoid predators, search for resources or conspecifics for mating, and engage in other collaborative endeavors. Displacement processes are known to affect interspecific relationships, especially when linked to foraging strategies. Various displacement phenomena occur in marine plankton, ranging from the large-scale diel vertical migration of zooplankton to microscale interactions around microalgal cells. Among these symbiotic interactions, collaboration between the centric diatom Chaetoceros coarctatus and the peritrich ciliate Vorticella oceanica is widely known and has been recorded in several studies. Here, using 2D and 3D tracking records, we describe the movement patterns of the non-motile, chain-forming diatoms (C. coarctatus) carried by epibiotic ciliates (V. oceanica). The reported data on the Chaetoceros–Vorticella association illustrated the consortium’s ability to generate distinct motility patterns. We established that the currents generated by the attached ciliates, along with the variability in the contraction and relaxation of ciliate stalks in response to food concentration, resulted in three types of trajectories for the consortium. The characteristics of these distinct paths were determined using robust statistical methods, indicating that the different displacement behaviors allowed the consortium to adequately explore distributed resources and remain within the food-rich layers provided in the experimental containers. A simple mechanical–stochastic model was successfully applied to simulate the observed displacement patterns, further supporting the proposed mechanisms of collective response to the environment. Full article

High mountain rainforests are vital in the global energy and carbon cycle. Understanding the exchange of energy and carbon plays an important role in reflecting responses to climate change. In this study, an eddy covariance (EC) measurement system installed in the high Andean Mountains of southern Ecuador was used. As EC measurements are affected by heterogeneous topography and the vegetation height, the main objective was to estimate the effect of the sloped terrain and the forest on the turbulent energy and carbon fluxes considering the energy balance closure (EBC) and the heat storage. The results showed that the performance of the EBC was generally good and estimated it to be 79.5%. This could be improved when the heat storage effect was considered. Based on the variability of the residuals in the diel, modifications in the imbalances were highlighted. Particularly, during daytime, the residuals were largest (56.9 W/m² on average), with a clear overestimation. At nighttime, mean imbalances were rather weak (6.5 W/m²) and mostly positive while strongest underestimations developed in the transition period to morning hours (down to −100 W/m²). With respect to the Monin–Obukhov stability parameter ((z − d)/L) and the friction velocity (u*), it was revealed that the largest overestimations evolved in weak unstable and very stable conditions associated with large u* values. In contrast, underestimation was related to very unstable conditions. The estimated carbon fluxes were independently modelled with a non-linear regression using a light-response relationship and reached a good performance value (R² = 0.51). All fluxes were additionally examined in the annual course to estimate whether both the energy and carbon fluxes resembled the microclimatological conditions of the study site. This unique study demonstrated that EC measurements provide valuable insights into land-surface–atmosphere interactions and contribute to our understanding of energy and carbon exchanges. Moreover, the flux data provide an important basis to validate coupled atmosphere ecosystem models. Full article

The soundscape is a complex arrangement of sounds originating from animals and the environment. It is considered a reliable proxy for ecosystem niche structure at the community level. Acoustic communities of anuran species include advertising males, which compete in acoustic space for conspecific females. Stochastic niche theory predicts that all local niches are occupied, and the acoustic community is species-saturated. Acoustic niches, which include the spectral and temporal call structure and diel and seasonal patterns of call activity, are of similar breadth with small overlap. We tested these predictions in four communities inhabiting pristine wetlands at 2546–3188 m a.s.l. in the Volcanoes National Park, Rwanda. We sampled 74 days of hourly 5 min recordings of the local soundscape (September 2019–March 2020) using passive automated monitoring devices (Songmeter SM4). We identified species based on the advertisement call features and measured call activity as calls per minute. The communities included 4–6, species depending on wetland structure, with a shared stock of three species (Hyperolius castaneus, H. glandicolor, Leptopelis kivuensis). Independent of elevation, niche breadth for call features was similar among species and overlap reduced by partitioning the frequency range used. The diel and seasonal niche breadth of specific call activity varied according to the local temperature regime at different altitudes representing the variable part of the acoustic niche. We conclude that communities are indeed species-saturated and acoustic niches differ primarily by the fixed call features remaining locally adaptable by the modulation of the call activity pattern, corroborating the predictions of the stochastic niche theory. Full article

This study examines the physiological response of the Atlantic surfclam (Spisula solidissima) to ocean acidification in warm summer temperatures. Working with ambient seawater, this experiment manipulated pH conditions while maintaining natural diel fluctuations and seasonal shifts in temperature. One-year-old surfclams were exposed to one of three pH conditions (ambient (control): 7.8 ± 0.07, medium: 7.51 ± 0.10, or low: 7.20 ± 0.10) in flow-through conditions for six weeks, and feeding and digestive physiology was measured after one day, two weeks, and six weeks. After six weeks of exposure to medium and low pH treatments, growth was not clearly affected, and, contrastingly, feeding and digestive physiology displayed variable responses to pH over time. Seemingly, low pH reduced feeding and absorption rates compared to both the medium treatment and ambient (control) condition; however, this response was clearer after two weeks compared to one day. At six weeks, suppressed physiological rates across both pH treatments and the ambient condition suggest thermal stress from high ambient water temperatures experienced the week prior (24–26 °C) dominated over any changes from low pH. Results from this study provide important information about reduced energy acquisition in surfclams in acidified environments and highlight the need for conducting multistressor experiments that consider the combined effects of temperature and pH stress. Full article

Thermal stratification is an important driver shaping phytoplankton community and their habitat condition in freshwater ecosystems. However, studies on river stratification have been restricted to rivers below dams or reservoirs affected by their water release and lacked examination of diel stratification and its impact on phytoplankton, in particular. Therefore, this study aimed to determine the degree of thermal stratification, its environmental drivers, and the response of water quality and phytoplankton community against stratification in the mid-lower reach of the Nakdong River, whose morphology has been highly modified, including the construction of eight weirs. We implemented vertical temperature profiling at three study sites, both seasonally and diurnally. From this data, we calculated three stratification indices: relative water column stability (RWCS), Schmidt stability (S), and maximum temperature gradient (Max). These indices showed that most sites experienced diel stratification during summer (mean = RWCS 74.3, S 41.5 J m⁻², Max 0.9 °C m⁻¹). Principal component analysis showed that stratification significantly led to seasonal and diel variations in the water environment. Solar radiation and air temperature were positive controllers, while a negative controller (in this case, the river flow rate) existed only for diel variation in the stratification. The seasonal shifts in phytoplankton community structure were either insensitive or showed a limited response to the stratification indices. In summer, Microcystis cell abundance and accumulation into the surface water was positively affected by the diel variations in the stratification indices and thermocline instead of with other temperature and nutrient variables. Overall, the results suggest that the river has summer stratification, which is involved in amplifying cyanobacterial bloom intensity. Without a suppressing factor, summer stratification is expected to be recurrent in the river, and thus mitigating the developed stratification is needed by promptly regulating the river flow. Full article

Studies based on fish early life stages can provide information on spawning grounds and nursery areas, helping to determine the implications for stock biomass fluctuations of recruitment variability. This study describes the composition, abundance, spatial distribution and differences in day/night vertical distribution of ichthyoplankton in the southern Adriatic Sea. Samples were collected within the framework of the COCONET project (Towards COast to COast NETworks of marine protected areas) from 9 to 18 May 2013 by the R/V Urania, using the electronic multinet EZ-NET BIONESS (Bedford Institute of Oceanography Net Environmental Sampling System). A total of 20 species, belonging to 20 genera and 13 families, were identified. Of the collected larvae, 74.3% were meso- or bathypelagic species, 24.7% were epipelagic and 0.9% were demersal. The community was dominated by Gonostomatidae, followed by Engraulidae, Myctophidae and Photychthaidae. The most abundant species was Cyclothone braueri (45.6%), followed by Engraulis encrasicolus, Ceratoscopelus maderensis, Cyclothone pygmaea, Vinciguerria attenuata and Myctophum punctatum. An inshore/offshore increasing gradient in biodiversity and abundance was observed. Different weighted mean depths (WMDs) were observed for larvae and juveniles. No diel vertical migrations were observed. The high abundance of meso- or bathypelagic species in the upper 100 m confirms the epipelagic zone as an important environment for the development of the larval stages of these fish. Full article

Unprovoked shark bites have increased over the last three decades, yet they are still relatively rare. Bull sharks are globally distributed throughout rivers, estuaries, nearshore areas and continental shelf waters, and are capable of making long distance movements between tropical and temperate regions. As this species is implicated in shark bites throughout their range, knowledge of the environmental drivers of bull shark movements are important for better predicting the likelihood of their occurrence at ocean beaches and potentially assist in reducing shark bites. Using the largest dataset of acoustically tagged bull sharks in the world, we examined the spatial ecology of 233 juvenile and large (including sub-adult and adult) bull sharks acoustically tagged and monitored over a 5.5-year period (2017–2023) using an array of real-time acoustic listening stations off 21 beaches along the coast of New South Wales, Australia. Bull sharks were detected more in coastal areas of northern NSW (<32° S) but they travelled southwards during the austral summer and autumn. Juveniles were not detected on shark listening stations until they reached 157 cm and stayed north of 31.98° S (Old Bar). Intra-specific diel patterns of occurrence were observed, with juveniles exhibiting higher nearshore presence between 20:00 and 03:00, whilst the presence of large sharks was greatest from midday through to 04:00. The results of generalised additive models revealed that large sharks were more often found when water temperatures were higher than 20 °C, after >45 mm of rain and when swell heights were between 1.8 and 2.8 m. Understanding the influence that environmental variables have on the occurrence of bull sharks in the coastal areas of NSW will facilitate better education and could drive shark smart behaviour amongst coastal water users. Full article

The first cave-monitoring studies to be carried out on the southwest (SW) coast of Türkiye on endangered Mediterranean monk seals using camera traps occurred between 2017 and 2021 in five marine caves within Gökova Bay. The visual data obtained from the monitoring studies were evaluated to reveal the Mediterranean monk seals’ seasonal and diel cave use and identify the individual seals who were using the caves. Moreover, the necessary features and measurements of the identified caves were recorded to determine whether there were any correlations between the determined variables and monthly cave use by the monk seals. The results showed that cave use occurred mainly nocturnally, with the seals showing a diurnal activity pattern in the area. We evaluated 108,280 images/videos in total and identified 18 individuals using five caves in Gökova Bay. Three of these caves provided suitable characteristics for pupping, and two of them were used for pupping. A beta regression model revealed that the monthly cave use ratios varied seasonally, with more use in the fall season. Furthermore, the trends in annual cave use ratios, seasonality, wind speed, size of the wet area, luminance, number of cave-entry paths, and human activity were the best variables with which we could forecast the cave preferences of the seals. Full article

The tuberous root of Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is a traditional Chinese medicine with a wide range of clinical applications. However, the scarcity of its wild resources, its low yield, and the variable quality that results from its artificial cultivation leads to expensive market prices that are not conducive to the further industrial development of T. hemsleyanum. In this study, transcriptomic and non-targeted metabolomic analyses were integrated to explore the underlying molecular mechanisms and metabolite biosynthesis that occur during its root development. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that differentially expressed genes (DEGs) were predominantly enriched for processes associated with flavonoid and phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction. Genes related to lignin were downregulated in tuberous roots (TRs), resulting in a decrease in lignification and the downregulation of metabolites related to flavonoids and phenylpropanoid biosynthesis. In addition, the expression levels of starch- and sucrose-related genes were upregulated in TRs. The root development of SYQ is also related to IAA, GA, ABA, and JA signaling pathways. Collectively, this study lays the foundation for analyzing the root development and quality-modulating mechanisms employed by T. hemsleyanum; this will be beneficial in conducting molecular-assisted breeding and controlling its secondary metabolite production. Full article

Most mesopelagic fishes perform large diel vertical migrations from the deep-sea zone to the surface. Although there is a trade-off between a higher food availability at the upper layers and an energy cost and predation risk, incursion towards the surface also implies a transport by currents, where the fish are exposed to a stranding risk on the coast. Here, we reported the first documented stranding of mesopelagic fishes along the southeast shore of Gran Canaria Island. Our study hypothesized that (1) the influence of the Canary Current, (2) the dominant incidence of the Trade Winds during summer, and (3) the presence of an upwelling filament coupled with an anticyclonic eddy south of Gran Canaria Island were the causative mechanisms of the strandings. Diaphus dumerilii (Myctophidae family) was the main species found as observed from an external morphological analysis using traditional taxonomy. The otolith contour analysis suggested the presence of other Diaphus spp. and Lobianchia dofleini. Nevertheless, the otolith morphological features described in the literature suggested that all the specimens were actually D. dumerelii. Errors in the identification were mainly due to the high intraspecific variability found in the otolith morphology. Even so, two patterns of oval and elliptic shapes were described with significant differences in its morphometry. Full article