Seasonal Temperature Variations Research Articles

Bioclimatic Envelopes for Two Bat Species from a Tropical Island: Insights on Current and Future Distribution from Ecological Niche Modeling

Bats perform critical ecosystem functions, including the pollination, seed dispersal, and regulation of invertebrate populations. Yet, bat populations are declining worldwide primarily due to habitat loss and other anthropogenic stressors. Thus, studies on bat ecology, particularly on environmental determinants of bat occupancy, are paramount to their conservation. High mobility, nocturnal behavior, and roosting site selection of bats make conventional surveys challenging. Moreover, little is known about geographic distribution, habitat suitability, and responses to climate change among tropical bat species. To bridge these research gaps, we applied ecological niche modeling to two Ceylonese bat species, Kerivoula malpasi and Kerivoula picta, to map their geographic distribution. Seasonal variations in temperature and precipitation were critical environmental predictors of bat distribution in general. Southwestern lowland forests contained the most optimal habitats for the relatively wide-ranging Kerivoula picta, while the central highlands provided the most suitable habitats for the narrow-ranging Kerivoula malpasi. No tangible changes in the highly suitable habitats were evident in response to projected climate change for either species. Yet, the optimal ranges of K. malpasi can become fragmented in the future, whereas the most optimal habitats for K. picta are likely to become spatially contiguous in the future. Habitat availability or fundamental niche alone is insufficient to reliably forecast species persistence, thus we caution against considering these two bat species as resilient to climate change. Our findings will enable the conservation authorities to initiate preemptive conservation strategies, such as the establishment of landscape-scale habitat connectivity and management of buffer zones around conservation lands. We also encourage conservation authorities to employ ecological niche models to map potential species distributions and to forecast range shifts due to climate change.

Influence of physical environmental parameters on the abundance of Chrysichthys nigrodigitatus of the Cross River, Nigeria.

In this study, the influence of physical environmental factors (rainfall, temperature, water depth, turbidity, transparency and conductivity) on the temporal distribution, abundance and catch of C. nigrodigitatus from the Cross River was investigated. Fish catch and abundance were monitored fortnightly for 12 months. Surface water samples were collected twice monthly and analyzed using standard methods. Seasonal variations in rainfall, water depth, temperature, turbidity, transparency and conductivity were observed across the study period. Correlation analysis showed a positive and significant relationship between rainfall and fish catch (P<0.05), while temperature and conductivity were negatively correlated with fish catch (P<0.05 and 0.01 respectively). Transparency was negatively correlated with fish catch but this relationship was, however, not statistically significant (P>0.05). On the other hand, water depth and turbidity were positively correlated with fish catch but again both relationships were not statistically significant (P>0.05). These findings suggest that rainfall, temperature, conductivity and other environmental variables play important role(s) in the distribution and abundance of Chrysichthys nigrodigitatus in the Cross River, with implication of climate change impact on the species reproductive ecology and population dynamics.

Consistent heat tolerance under starvation across seasonal morphs in Mycalesis mineus (Lepidoptera: Nymphalidae)

Heat tolerance is a key trait for understanding insect responses to extreme heat events, but tolerance may be modulated by changes in food availability and seasonal variability in temperature. Differences in sensitivity and resistance across life stages are also important determinants of species responses. Using a full-factorial experimental design, we here investigated the effects of larval starvation, adult starvation, and seasonal morph (developmental temperature) on heat tolerance of a seasonally polyphenic butterfly, Mycalesis mineus, in both larval and adult stages. While starvation and rearing temperature profoundly influenced various life history traits in the insect, none of the treatments affected adult heat tolerance. There was also no evidence of reduced heat tolerance in larvae under starvation stress, though larval thermal tolerance was higher by ~1 °C at the higher developmental temperature. The lack of a starvation effect was unexpected given the general physiological cost of heat tolerance mechanisms. This might be attributed to the ability to tolerate heat being preserved under resource-based trade-offs due to its critical role in ensuring insect survival. Invariant heat tolerance in M. mineus shows that some insects may have thermal capacity to cope with extreme heat under short-term starvation and seasonality disruptions, though more prolonged changes may have greater consequences. The capacity to maintain key physiological function under multiple stressors will be crucial for species resilience in future novel environments.

Temperature mediated the balance between stochastic and deterministic processes and reoccurrence of microbial community during treating aniline wastewater

Seasonal temperature changes significantly affect microbial community diversity, composition, and performance in wastewater treatment plants. However, the community assembly mechanisms under seasonal temperature variations remain unclear. Here, we carried out temperature cycling experiments (30 °C, 35 °C, 37 °C, 40 °C, 42 °C, 45 °C, 40 °C, and 30 °C) to investigate how temperature impacts microbial performance and co-occurrence network and how assembly processes determine the structure and function of microbial communities during treating aniline wastewater. During the 195-day operation, the system achieved an efficient and stable aniline removal of 99%. Interestingly, α-diversity and network complexity were negatively correlated with temperature but could be recovered when the temperature was returned to 30 °C. The results showed that functional redundancy was probably responsible for the excellent microbial performance during the whole process. Null model analyses presented that deterministic process dominated the community when the temperature was 30 °C, and stochasticity dominated the assembly process when the temperature was over 30 °C. Overall, the balance between stochastic and deterministic processes in the treatment of aniline wastewater mediated the reoccurrence of microbial community and co-occurrence network at different temperatures. This study provides new insights into microbial community reoccurrence under seasonal temperature changes and a theoretical basis for regulating microbial communities in wastewater treatment plants.

Evaluation of Observed and Future Climate Change Projection for Uttarakhand, India, Using CORDEX-SA

The climate change scenarios, especially global warming, have raised significant concerns, and the Himalayan regions such as Uttarakhand are highly vulnerable to such climatic shifts. Considering 10 Coordinated Regional Climate Downscaling Experiments in South Asia (CORDEX-SA), experiments with 3 regional climate models (RCMs), driven by 13 global climate models, historical estimates and future projections are analyzed from the mid-century (MC) i.e., from 2021–2050 to the end of the century (EC) i.e., from 2070–2099 to characterize annual and seasonal variations in precipitation and temperature. The analysis shows a decrease in the annual average precipitation by 5.92% at MC and an increase of 5.97% at EC for the Representative Climate Pathway (RCP) 4.5, while precipitation may likely increase from 2.83% to 15.89% towards MC and EC in the RCP 8.5. The maximum temperature may likely increase from 0.42 °C to 3.07 °C from MC to EC in the RCP 4.5 and from 0.83 °C to 5.49 °C in the RCP 8.5. In addition, the minimum temperature may increase from 0.80 °C to 3.25 °C from MC to EC in the RCP 4.5 and from 0.30 °C to 5.86 °C from MC to EC in the RCP 8.5. Notably, a decrease in the pre-monsoon precipitation at EC and a higher increase in the maximum temperature during the monsoon season are observed. An increase in the maximum temperature along with precipitation may lead to an increase in the frequency of the monsoon season’s extreme rainfall events.

Variations of microbial communities and substrate regimes in the eastern Fram Strait between summer and fall.

Seasonal variations in day length and temperature, in combination with dynamic factors such as advection from the North Atlantic, influence primary production and the microbial loop in the Fram Strait. Here, we investigated the seasonal variability of biopolymers, microbial abundance and microbial composition within the upper 100 m during summer and fall. Flow cytometry revealed a shift in the autotrophic community from picoeukaryotes dominating in summer to a 34-fold increase of Synechococcus by fall. Furthermore, a significant decline in biopolymers concentrations covaried with increasing microbial diversity based on 16S rRNA gene sequencing along with a community shift towards fewer polymer-degrading genera in fall. The seasonal succession in the biopolymer pool and microbes indicates distinct metabolic regimes, with a higher relative abundance of polysaccharide-degrading genera in summer and a higher relative abundance of common taxa in fall. The parallel analysis of DOM and microbial diversity provides an important baseline for microbe-substrate relationships over the seasonal cycle in the Arctic Ocean.

A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability

Abstract. Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The carbon isotopic composition (δ13C) of such carbonates depends on the δ13C of dissolved inorganic carbon (DIC). Their oxygen isotopic composition (δ18O) is controlled by the δ18O of the lake water and by water temperature during carbonate precipitation. Lake water δ18O, in turn, reflects the δ18O of atmospheric precipitation in the catchment area, water residence time and mixing, and evaporation. A paleoclimatic interpretation of carbonate isotope records requires a site-specific calibration based on an understanding of these local conditions. For this study, samples of different biogenic carbonate components and water were collected in the littoral zone of Lake Locknesjön, central Sweden (62.99∘ N, 14.85∘ E, 328 ma.s.l.) along a water depth gradient from 1 to 8 m. Carbonate samples of living organisms and subfossil remains in surface sediments were taken from the calcifying alga Chara hispida, from bivalve mollusks of the genus Pisidium, and from adult and juvenile instars of two ostracod species, Candona candida and Candona neglecta. Our results show that neither the isotopic composition of carbonates nor the δ18O of water vary significantly with water depth, indicating a well-mixed epilimnion. The mean δ13C of Chara hispida encrustations is 4 ‰ higher than the other carbonates. This is due to fractionation related to photosynthesis, which preferentially incorporates 12C into the organic matter and increases the δ13C of the encrustations. A small effect of photosynthetic 13C enrichment in DIC is seen in contemporaneously formed valves of juvenile ostracods. The largest differences in the mean carbonate δ18O between species are caused by vital offsets, i.e., the species-specific deviations from the δ18O of inorganic carbonate which would have been precipitated in isotopic equilibrium with the water. After subtraction of these offsets, the remaining differences in the mean carbonate δ18O between species can mainly be attributed to seasonal water temperature changes. The lowest δ18O values are observed in Chara hispida encrustations, which form during the summer months when photosynthesis is most intense. Adult ostracods, which calcify their valves during the cold season, display the highest δ18O values. The seasonal and interannual variability in lake water δ18O is small (∼ 0.5 ‰) due to the long water residence time in the lake. Seasonal changes in the temperature-dependent fractionation are therefore the dominant cause of carbonate δ18O differences between species when vital offsets are corrected. Temperature reconstructions based on paleotemperature equations for equilibrium carbonate precipitation using the mean δ18O of each species and the mean δ18O of lake water are well in agreement with the observed seasonal water temperature range. The high carbonate δ18O variability of samples within a species, on the other hand, leads to a large scatter in the reconstructed temperatures based on individual samples. This implies that care must be taken to obtain a representative sample size for paleotemperature reconstructions.

Predicted Pleistocene–Holocene range and connectivity declines of the vulnerable fishing cat and insights for current conservation

AbstractAimIdentifying appropriate conservation measures requires a reasonable understanding of a species' population status, distribution and vulnerability. However, for many species, these variables may not be understood under the context of current conditions alone. Here, we assess the potential role historical changes in climate, sea level and anthropogenic activity may have had on the distribution of one of the world's least‐understood wild cats and identify broader implications for conservation efforts that may not be apparent from just an examination of the species' current distribution.LocationTropical Asia.TaxonFishing cat (Prionailurus viverrinus).MethodsWe used a presence‐only ecological niche model and a least‐cost graph‐based connectivity model to characterize the species' bio‐climatic niche and predict changes in suitability and connectivity under current and paleoenvironmental conditions.ResultsFishing cat occurrence was associated with landscapes that were low in elevation and high in topographic wetness and climates that were warm with moderate annual precipitation and moderate seasonal variation in both temperature and precipitation. Since the Last Interglacial, the area predicted to be climatically suitable has ranged from 5.9 million km2 during the Last Glacial Maximum to 2.2 million km2 during the Current Era. Changes in regional connectivity correlated with changes in suitable area for all periods except the Current Era. Relative connectivity of areas affected by past sea level rise was highest in areas with large alluvial plains, emergent coastal areas and deltas.Main conclusionsOur findings suggest that the fishing cat's current distribution and vulnerability can be explained by a synergistic combination of historical climate change, sea level rise, and anthropogenic land‐use change. Changes in suitability and connectivity over time highlight potential core areas that are underrepresented by historical survey efforts. Future survey efforts should include these areas, with an emphasis on quantifying tolerances to anthropogenic disturbances.

Oxygen Isotopic Studies of a Species of Pitar (Hyphantosoma) from Quilon Formation, Kerala, Southwest India: Inferences on Seasonality during the Miocene (late Burdigalian)

Abstract The carbonaceous shale of the Miocene (late Burdigalian) Quilon Formation (Kerala Basin, southwest India) were collected and processed to retrieve the microfaunal component. In the present study, the oxygen isotope analysis of the growth bands of the recovered bivalves Pitar (Hyphantosoma) simonnei and Ostrea sp. (both retrieved from the Quilon Formation) is emphasized to help reconstruct the palaeomonsoonal seasonality. The oxygen-isotope record for the specimens of P.(Hyphantosoma) simonnei and Ostrea sp. exhibits regular, high amplitude δ18O cycles caused by the yearly seasonal temperature and monsoonal variations. Based on the number of δ18O cycles,P. (Hyphantosoma) simonnei and Ostrea sp. have been considered to be approximately 2- and 4-year-old, respectively, at the time of deposition. The calculated palaeo- seawater δ18O values between -0.6 to -1.1‰ [for P. (Hyphantosoma) simonnei] allow us to distinguish between the wet and dry seasons. In addition, the two-component mixing model is suggestive of seasonal freshwater discharge of ~70-80% during wet season and ~20-40% during the dry season into the depositional system. This reconstructed palaeo-seasonality clearly indicates presence of monsoon system in the south west of India during the Miocene (late Burdigalian).

Effect of Natural Seasonal Changes in Photoperiod and Temperature on Immune Function in Striped Hamsters.

What environmental factors contribute to seasonal variation in immune function in striped hamsters (Cricetulus barabensis) remains unclear. How immune responses would respond to natural seasonal changes in photoperiod and temperature was investigated in the present study. Twenty-nine male and 30 female hamsters were randomly assigned to the winter, spring, summer, and autumn groups. Spleen mass was the highest in male hamsters during autumn, while it did not differ among seasons in females. Regardless of sex, bacteria killing activity (BKA) was the lowest in the spring, whereas phytohaemagglutinin (PHA) responses at 12 h, 24 h, and 48 h were all highest in the winter among the four seasons. Females had the lowest titers of immunoglobin (Ig)G5, 10, and 15 in winter, while they did not show seasonal variation in males. Compared with male hamsters, females had higher levels of IgG10 and IgG15 in the spring and autumn, but had lower BKA in autumn. Blood glucose was the lowest in the spring in both sexes. Males had higher leptin level in winter than in summer and autumn, while leptin level was higher in winter and spring than in autumn in females. Corticosterone level was higher in winter and summer than in spring and autumn in males, while it was higher in winter than in the other three seasons in females. Males had higher levels of leptin in winter, and corticosterone in summer, than females. In summary, distinct parts of the immune system respond differently to natural seasonal variations in photoperiod and temperature.

Transcriptome analysis revealed hub genes for muscle growth in Indian major carp, Catla catla (Hamilton, 1822)

Catla (Catla catla) is the fastest growing Indian major carp species and forms an important component of the freshwater aquaculture systems in the Indian sub-continent. The molecular mechanisms of growth of the species in response to seasonal water temperature variations hitherto are still unknown. In the current study, high-throughput transcriptome sequencing was used to study the differential gene expression pattern in catla muscle tissues between pre-winter and post-winter fingerling groups and fast-growing table size fish. Transcriptome analysis identified 1677 differentially expressed genes (DEGs) in three different growth stages and 236 common DEGs between fingerling at low temperature and table fish post-winter, including four genes under GH/IGF1 axis and 163 genes under signature for compensatory muscle growth. Molecular pathways for the mapped genes identified 42 KEGG pathways and the critical pathways under Environmental Information Processing identified were PI3K-Akt signaling, AMPK signaling pathway, Calcium signaling pathway and MAPK signaling pathway. In this study, 14 differentially expressed potential regulatory hub genes for growth were identified, for the first time and categorized into three major GO groups: unfolded protein binding, rNA processing and biogenesis and muscle development and differentiation. These regulatory hub genes, except acta1, were found to be upregulated in fast-growing table size and post-winter fingerling groups. The results provided valuable information about the key genes, with potential to be used as biomarkers of growth in breeding programs and contributed to our understanding of the molecular mechanisms and pathways regulating muscle growth, in response to temperature fluctuations and different growth stages in C. catla.

The role of alternative fuel buses in the transition period of public transport electrification in Europe: a lifecycle perspective

In alignment with climate change, the European Union endeavors to accelerate the electrification progress of the public transit system. In particular, Copenhagen in Denmark and Oslo in Norway develop a blueprint to have 100% public transit electrification by 2030 and 2028, respectively. In this study, the lifecycle approach is applied to explore the role of electric buses in the electrification progress of the public transport system in different European countries. To better model the energy/fuel consumption, we integrate the theoretical model of human thermal comfortable temperature into our proposed framework. We take into account the effects of weather, the daily operation characteristics, and the energy mix of different European counties, and evaluate the lifecycle environmental and economic performance of electric buses. The result shows that the public transportation system with both hybrid and electric buses can be good compensation between financial and environmental needs instead of using electric buses to replace all the conventional buses. Moreover, the operational plan of the public transportation system mixed with electric and hybrid buses may be adjusted according to the seasonal temperature variation so as to maximize the environmental benefits. Considering the different economic and environmental scenarios of energy sources, some EU countries would be able to reduce or remove the incentives for electric buses.

Burden, Clinical Characteristics, Risk Factors, and Seasonality of Adenovirus 40/41 Diarrhea in Children in Eight Low-Resource Settings

BackgroundThe application of molecular diagnostics has identified enteric group adenovirus serotypes 40 and 41 as important causes of diarrhea in children. However, many aspects of the epidemiology of adenovirus 40/41 diarrhea have not been described.MethodsWe used data from the 8-site Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development Project birth cohort study to describe site- and age-specific incidence, risk factors, clinical characteristics, and seasonality.ResultsThe incidence of adenovirus 40/41 diarrhea was substantially higher by quantitative polymerase chain reaction than enzyme immunoassay and peaked at ∼30 episodes per 100 child-years in children aged 7–15 months, with substantial variation in incidence between sites. A significant burden was also seen in children 0–6 months of age, higher than other viral etiologies with the exception of rotavirus. Children with adenovirus 40/41 diarrhea were more likely to have a fever than children with norovirus, sapovirus, and astrovirus (adjusted odds ratio [aOR], 1.62; 95% CI, 1.16–2.26) but less likely than children with rotavirus (aOR, 0.66; 95% CI, 0.49–0.91). Exclusive breastfeeding was strongly protective against adenovirus 40/41 diarrhea (hazard ratio, 0.64; 95% CI, 0.48–0.85), but no other risk factors were identified. The seasonality of adenovirus 40/41 diarrhea varied substantially between sites and did not have clear associations with seasonal variations in temperature or rainfall.ConclusionsThis study supports the situation of adenovirus 40/41 as a pathogen of substantial importance, especially in infants. Fever was a distinguishing characteristic in comparison to other nonrotavirus viral etiologies, and promotion of exclusive breastfeeding may reduce the high observed burden in the first 6 months of life.

Climate predictors and climate change projections for avian haemosporidian prevalence in Mexico.

Long-term, inter-annual and seasonal variation in temperature and precipitation influence the distribution and prevalence of intraerythrocytic haemosporidian parasites. We characterized the climatic niche behind the prevalence of the three main haemosporidian genera (Haemoproteus, Plasmodium and Leucocytozoon) in central-eastern Mexico, to understand their main climate drivers. Then, we projected the influence of climate change over prevalence distribution in the region. Using the MaxEnt modelling algorithm, we assessed the relative contribution of bioclimatic predictor variables to identify those most influential to haemosporidian prevalence in different avian communities within the region. Two contrasting climate change scenarios for 2070 were used to create distribution models to explain spatial turnover in prevalence caused by climate change. We assigned our study sites into polygonal operational climatic units (OCUs) and used the general haemosporidian prevalence for each OCU to indirectly measure environmental suitability for these parasites. A high statistical association between global prevalence and the bioclimatic variables ‘mean diurnal temperature range’ and ‘annual temperature range’ was found. Climate change projections for 2070 showed a significant modification of the current distribution of suitable climate areas for haemosporidians in the study region.

Effect of varying pore water salinity on frost susceptibility behaviour of soils

The susceptibility of soil to frost action is a major distress for engineering infrastructure constructed over it in regions that experience seasonal freezing and thawing. The soil deposits which are not otherwise problematic for use as a subgrade/foundation material can become very problematic under seasonal freeze-thaw. Since presence of dissolved salts in pore water depresses the freezing-point and increases the unfrozen water content, it can be ascertained that pore water salinity can affect soil frost susceptibility due to seasonal temperature variations by reducing the total ice content during freezing. An experimental investigation was carried out to assess the effect of pore water solute content on the behaviour of a frost susceptible soil subjected to freeze-thaw cycles in a laboratory test setup as per ASTM D5918-13. The presence of solute primarily depressed the freezing point of the soil. The heave rate, maximum heave and the frost penetration depth was found to decrease with increasing solute concentration in pore water. The effect on the thaw-CBR value, variation in water migration pattern and micro-structural changes along the depth of the sample was also examined. It was found that the presence of solutes negates the undesirable effects during freezing by controlling ice segregation, frost penetration and heaving of the soil which in turn limit the adverse weakening during thawing. The destruction to soil at micro-structural level was also restricted in the samples containing solute in their pore water.

Analysis of Climate Variability and Its Impact on Crop Yield Over Waghemra Zone, Ethiopia

Climate variability manifested by seasonal rainfall and temperature variability greatly affects agricultural crop production under rain-fed conditions (main source of income for rural communities). Therefore, this study has focused on analyzing the impacts of climate variability on rain-fed wheat and sorghum production in Waghemra Zone, Ethiopia. Daily rainfall and temperature data were collected from National Meteorological Agency of Ethiopia and crop yield data was collected from Central Statics Agency of Ethiopia. Temporal variability of rainfall, temperature and crop yield was analyzed using coefficient of variation (CV) and standardized anomaly method. The rainfall and temperature trends were assessed via Mann-Kendall test and Sen’s slope estimator. The impacts of climate variability on crop yields were evaluated using correlation and regression analysis. The rainfall analysis exhibited large inter-annual and seasonal variation both in amount and distribution. The rainfall has showed decreasing trends in Belg and increasing in both annual and Kiremt season. Moreover, the detected trends are not significant. In contrast, minimum and maximum temperature showed significantly increasing trends at annual and seasonal time scales. The number of warm days and nights has increased and the number of cold days and nights has decreased. The regression analysis revealed that climate variability over the study area has differential effects on the yield of Wheat and Sorghum with coefficient of determination 86% and 84%, respectively. The observed rainfall and temperature variability has posed major risks to rain-fed agriculture and specific adaptation strategies are needed to cope with the risks, sustain farming and improve food security.

Monitoring the Seasonal Distribution and Variation of Sea Surface Temperature and Chlorophyll Concentration in Bay of Bengal using MODIS Satellite Images

Using MODIS Global Satellite products from 2016 to 2020, the variance in sea surface temperature (SST) and chlorophyll concentrations in the waters of the Bay of Bengal (BoB) is investigated during this study. Seasonal maps prepared from the monthly average of SST are compared to observe the change throughout the timeframes of spring, summer, autumn, and winter. The annual cycle of SST depicts the phases of cooling in winter, heating in summer, and warming in spring. It has been found that the presence of heated pools (SST > 30°C) prolongs the summer endurance within the Bay in summer. The SST variations are also strongly linked to regional-scale climate variations from late winter to early spring. Anomalies in chlorophyll are often considered early indicators and drivers of changes in marine resources. However, there has been little assessment of the abnormality in this component in coastal waters of the BoB. The measured chlorophyll distribution during the study reveals anomalies consistent in magnitude having a prominent north-south gradient, where the greater concentrations lie in the northern part. In addition, the fluvial input provided in the central part of the Bay by the Ganges-Brahmaputra-Meghna River system during monsoon contributes additional credence to this assertion.

Formation of murtoos by repeated flooding of ribbed bedforms along subglacial meltwater corridors

Fluctuations in meltwater discharge below modern glaciers and ice sheets due to diurnal, seasonal and long-term temperature variations are modulated by complex interactions between subglacial drainage, basal processes and bedform development. The bed of palaeo-ice sheets contains a variety of bedforms recording these modulations and provides an open window into the subglacial environment. Through the morphometric analysis of natural and experimental bedforms, respectively mapped along Scandinavian meltwater corridors and produced in a physical model simulating transitory subglacial water flow, we observe a morphological and genetic bedform continuum corresponding to the progressive transformation of ribbed bedforms into murtoos. Two alternating drainage configurations, related to repeated subglacial flooding events, are involved in this transformation: (i) significant meltwater discharge, high hydraulic connectivity and ice-bed decoupling during flooding events lead to hydraulic alteration of ribbed bedforms by erosion, sediment deposition and channel incision, while (ii) limited meltwater flow, low hydraulic connectivity and ice-bed recoupling that follow flooding events lead to their deformational reshaping into murtoos. The degree of transformation of ribbed bedforms into murtoos can be quantified by combining two dimensionless morphometric parameters (circularity and sinuosity) and provides a convenient proxy to constrain magnitudes, durations and/or frequencies of subglacial floods in palaeo-meltwater corridors.

Comparative analysis of the performance of the GOFS, PSY4 and AMSEAS ocean model frameworks in the Virgin Islands and Puerto Rico coastal ocean

ABSTRACT This work compares the performance of three ocean model frameworks that currently produce outputs of the ocean properties specific to the US Caribbean ocean; the Global Ocean Forecast System (GOFS), US Navy Coastal Ocean Model for the American Seas (AMSEAS) and the Daily Global Physical Bulletin (PSY4). Separate comparisons are done for the ocean properties in the open ocean and nearshore regions. For the open ocean, the model outputs are compared with the AVISO satellite altimetry data for the sea-surface height anomaly (SSHA), the OSCAR data for surface current velocities and the G1SST satellite data for sea-surface temperature (SST). For the nearshore analysis, the model outputs are compared with in-situ buoy measurements and HOBO logger data in the nearshore regions. Our analysis shows that the PSY4 produces the most realistic outputs of SSHA and surface current velocities in the open ocean, whereas all the models produce a strong correlation in terms of the seasonal variability of the surface temperature when compared to the G1SST data. The AMSEAS model, despite being a fine resolution regional model, underperforms in terms of the surface current velocity outputs in the open ocean due to the influence of the simulated submesoscale turbulence on the mesoscale variability. In the nearshore regions, none of the models produce agreeable outputs on the SSHA and current velocities. These findings provide useful insight on the applicability of the model outputs for various operations that require oceanographic data specific to the US Caribbean ocean.

Seasonal Changes in an Afromontane Forest Bird Community in Tanzania

Seasonal variation in the composition of avian communities is poorly documented in African montane forests. Using field observations, mist-netting data (63,424 NMH), recording of mixed-species flocks (160 flocks noted), and of the feeding ecology of greenbuls (757 observations), we document marked seasonal changes in a bird community in an East African montane forest (1,340–2,130 m) in the Udzungwa Mountains in south-central Tanzania. This mountain range contains the largest remaining forests in the Eastern Arc Mountains in Tanzania, part of a key global biodiversity hotspot. Our analysis is based on data in the dry and wet season from about 12 months of fieldwork. Field observation data combined with mist-net data demonstrate noticeable seasonal changes in certain species’ abundances, indicating (i) seasonal movements out of the montane forest during the dry season and (ii) movements of part of the populations for other species. Our mist-net results show a significant difference in species abundances between the two seasons driven by 16 species. We also document significant changes in diet for two species of greenbuls, which shift feeding behavior from arthropods in the wet season to include a larger proportion of fruit in their dry season diet. Our results further show that birds are more active in mixed-species flocks in the dry season, with a significantly higher average number of species and of individuals in the dry season, i.e., 11.3 (±0.52 SE) species, 32.3 (±1.76 SE) individuals] compared to the wet season 9.7 (±0.78 SE) species, 20.8 (±1.85 SE) individuals]. One of two very distinctive types of mixed-species flocks – confined to the understory – exists only in the dry season. We discuss these changes to seasonal variability in climate, i.e., temperature and precipitation.