Variations In Environmental Parameters Research Articles

Feature-Based Place Recognition Using Forward-Looking Sonar

Some structures in the harbour environment need to be inspected regularly. However, these scenarios present a major challenge for the accurate estimation of a vehicle’s position and subsequent recognition of similar images. In these scenarios, visibility can be poor, making place recognition a difficult task as the visual appearance of a local feature can be compromised. Under these operating conditions, imaging sonars are a promising solution. The quality of the captured images is affected by some factors but they do not suffer from haze, which is an advantage. Therefore, a purely acoustic approach for unsupervised recognition of similar images based on forward-looking sonar (FLS) data is proposed to solve the perception problems in harbour facilities. To simplify the variation of environment parameters and sensor configurations, and given the need for online data for these applications, a harbour scenario was recreated using the Stonefish simulator. Therefore, experiments were conducted with preconfigured user trajectories to simulate inspections in the vicinity of structures. The place recognition approach performs better than the results obtained from optical images. The proposed method provides a good compromise in terms of distinctiveness, achieving 87.5% recall considering appropriate constraints and assumptions for this task given its impact on navigation success. That is, it is based on a similarity threshold of 0.3 and 12 consistent features to consider only effective loops. The behaviour of FLS is the same regardless of the environment conditions and thus this work opens new horizons for the use of these sensors as a great aid for underwater perception, namely, to avoid degradation of navigation performance in muddy conditions.

Effect of environmental drivers of fish assemblage and diversity patterns in temporal scale in Mongra Reservoir: A case study from one of the tributaries of Mahanadi Basin, Central India

AbstractInfluence of seasonal variations in environmental parameters on fish assemblage and species diversity patterns was studied in a tropical reservoir of Central India during March 2021 to February 2022. A total of 41 species belonging to 7 orders, 15 families and 29 genera were recorded with highest diversity during post‐monsoon season compared to the pre‐monsoon season and monsoon season. The fish abundance similarity between the monsoon and post‐monsoon reached a maximum of 89%. Seasonal variations in the mean species abundance, Simpson dominance index, Shannon diversity index, Pielou's evenness index and Margalef's richness index were determined. One‐way ANOVA revealed a significant difference (P < 0.05) at the temporal scale. There was a significant seasonal difference in species abundance (P = 0.0006) and evenness index (P = 0.02) among the diversity indices. During the study period, three ‘vulnerable’ species, three ‘near threatened’ species and two ‘endangered’ species were caught. Carnivore dominance was evident throughout the year in the trophic guild of fishes. The Pearson correlation test revealed that water pH, dissolved oxygen, sediment organic carbon and clay percentage were positively correlated to all four diversity indices. Simpson and Margalef species richness diversity indices were positively correlated to sediment pH. Fish abundance was positively associated with sediment pH, silt, phosphorus and nitrogen content. Canonical correspondence analysis was used to investigate the relationships between fish assemblages and environmental conditions. Among the 19 physicochemical parameters, nine (dissolved oxygen, total dissolved solids, conductivity, transparency, hardness, phosphate and chlorophyll‐a, sediment nitrogen and phosphorus) characteristics were shown to be statistically significant (P < 0.05) in determining fish diversity. Dissolved oxygen, total dissolved solids, conductivity, transparency, hardness, phosphate and chlorophyll‐a of water and sediment nitrogen and phosphorus qualities were the key factors for the species abundance. The reservoir boasts a diverse fish population that allows multi‐species fishing and generates revenue for numerous local fishers. Fish habitats should be protected in order to maintain diversity and long‐term ecological benefits.

A virtual sensor network for pressure distribution inside a multi-zone building based on spatial adjacency relationships and multivariate adaptive regression spline

Airflows within multi-zone buildings cause variations in environmental parameters both vertically and horizontally. Although it is difficult to monitor the airflows through existing sensors, pressure monitoring allows the identification of airflows, since airflows across zones are induced by pressure differences. This study proposes a data-driven method for establishing a virtual pressure sensor network within a multi-zone building. Three scenarios with various sample sizes are applied to evaluate their impacts on the analyzed results, and scenario 3 is identified as the most suitable database for creating a virtual sensor network. The single-sided or multi-sided spatial adjacency relationships are determined for each zone, and the MARS model is then applied to develop the relationships among the variables, with key physical sensors designated by the frequency analysis of independent variables. The final sensor network comprises four key physical sensors, thirteen direct virtual sensors, and five indirect virtual sensors. All virtual sensors can achieve excellent predicted results with high R2 values and low MAE and RMSE, with mean values of 0.997 Pa and 1.269 Pa, respectively. Notably, the difference in accuracy between direct and indirect virtual sensors is influenced by spatial adjacency relationships. This study demonstrates a reliable virtual sensor network for predicting pressure variations and provides a reference for the identification of airflows and the efficient adjustment of HVAC systems.

Ecological assessment of a subtropical floodplain wetland of the Ganga basin in the context of changing climate using GIS tools

Abstract Climate change associated with anthropogenic stressors are considered the main threat to the tropical wetlands, resulting in reduced water connection followed by a decline in ecological functions. This article presents a systemic approach to assess the present ecological status of a tropical floodplain wetland concerning the fisheries and associated ecosystem services. The analysis of historic climatic data indicated significant change (increasing average annual air temperature, R2 = 0.098; decreasing total annual rainfall, R2 = 0.042). In addition, a significant reduction in the wetland area was also observed. Altogether, 45 fish species were reported in the studied wetland, of which 2 are listed as endangered and 7 are near threatened. The present study demonstrated the variation of the important fisheries-related environment and nutrient parameters of the wetland through the geographic information system (GIS)-based spatial distribution map for the reader's digest. It has been found that the provisioning ecosystem services are higher in number (n=9) followed by supporting (n=6), regulating (n=4), and cultural (n=2) ecosystem services. Finally, we have discussed some important case-specific sustainable climate-smart adaptation and mitigation approaches to strengthen the resilience and adaptive capacity of fishers.

Impact of Variation in Environmental Parameters on Abundance of Paracalanidae (Calanoida: Copepoda) from the Tropical Coast of India, Bay of Bengal

Impact of Variation in Environmental Parameters on Abundance of Paracalanidae (Calanoida: Copepoda) from the Tropical Coast of India, Bay of Bengal

Shifts in species dominance related to spatial assemblages and variation in environmental parameters in a tropical mangrove estuary

A shift in species dominance in the mangrove microalgae community in Cross River Estuary System (CRES), Nigeria, was carried out during the wet season to highlight the microalgae structure, identify potential indicators, and evaluate the water quality variation. Plankton samples were collected at sixteen selected sampling sites along the river. Diatoms showed the highest number of species (240 species), contributing more than 70% of the total microalgae abundance. Cluster analysis of the microalgae community delimits the CRES into three sections; upper (UCRS), middle (MCRS), and lower (LCRS) communities. The spatial shift in the microalgae community showed that the green algae (Eudorina elegans and Hylotheca dissiliens) dominated the UCRS communities, while diatoms dominated the MCRS (Polymyxus coronalis and Actinocyclus normanii) and LCRS (A. normanii and A. octonarius). The principal component analysis showed that the UCRS was influenced by turbidity and nitrate, while the MCRS and LCRS were characterized by phosphate, electrical conductivity, and salinity/total dissolved solids. The similarity percentage (SIMPER) analysis showed that Surirella tenera and Hylotheca dissiliens contributed >3.5% inter site dissimilarity between the UCRS and LCRS microalgae community. The redundancy analysis revealed that some microalgae species such as Odontella mobiliensis, Coscinodiscopsis jonesiana, A. normanii, and A. octonarius responded positively to salinity change and ammonia concentration in the estuary, while S. tenera, P. coronalis, Bacillaria paxilifer, Navicula transitans, Cyclotella meneghiniana, Humidophila contenta, Melosira granulata, Aulacoseira herzogii, Eudorina elegans, H. dissiliens, Mougeotia sp., and Dinobryon sertularia responded positively to turbidity, nitrate, and phosphate concentration. This study illustrates that CRES inhabit rich biodiversity of microalgae which some taxa could be used as indicators of the environmental changes in marine waters.

Slow growing bacteria survive bacteriophage in isolation

The interactions between bacteria and bacteriophage have important roles in the global ecosystem; in turn changes in environmental parameters affect the interactions between bacteria and phage. However, there is a lack of knowledge on whether clonal bacterial populations harbour different phenotypes that respond to phage in distinct ways and whether the abundance of such phenotypes within bacterial populations is affected by variations in environmental parameters. Here we study the impact of variations in nutrient availability, bacterial growth rate and phage abundance on the interactions between the phage T4 and individual Escherichia coli cells confined in spatial refuges. Surprisingly, we found that fast growing bacteria survive together with all of their clonal kin cells, whereas slow growing bacteria survive in isolation. We also discovered that the number of bacteria that survive in isolation decreases at increasing phage doses possibly due to lysis inhibition in the presence of secondary adsorptions. We further show that these changes in the phenotypic composition of the E. coli population have important consequences on the bacterial and phage population dynamics and should therefore be considered when investigating bacteria-phage interactions in ecological, health or food production settings in structured environments.

Evaluation of Rodent Diet Stability when Stored in Conditions that Diverge from Guide Parameters.

An essential aspect of animal resource programs is the storage and provision of food for a variety of species. Environmental parameters for feed storage conditions (temperature less than 70 °F; relative humidity less than 50%) are recommended in the Guide for the Care and Use of Laboratory Animals, along with aspects of nutrition such as palatability, vermin-control measures, diet quality, and integrity of feed bags. After receiving a suggestion for improvement for environmental conditions in 2 feed storage locations during an AAALAC accreditation visit, we hypothesized that the packaging of contemporary rodent feed could sustain wider environmental variations in temperature and humidity without adverse impact on integrity and palatability. This study evaluated representative feed storage sites across campus buildings to capture the variation in environmental conditions that are inherent to large and diverse animal care programs. Each test storage location held 2 identical bags of feed (same type, lot, and expiration date) that were stored from June to September of 2021; some aspects of the project were repeated during summer 2022 with a similar rodent feed. Baseline nutrients were analyzed from feed samples collected at time 0 (control) and again after 1 and 3mo of storage. The overall nutritional values measured in feed at the end of the study were not significantly different from control values, regardless of test site and variation in environmental parameters. Retinol (as a measure of Vitamin A) was the only component that decreased significantly; however, final retinol levels were consistently above those necessary for appropriate nutrition for mice. Our animal care program stakeholders were briefed on the outcomes of this study with the intent to verify at future AAALAC site visits that our storage conditions are adequate for maintaining the nutritional quality of packaged rodent feed.

Influence of environmental conditions on mass rearing parameters of tsetse flies at the Bobo-Dioulasso insectary (Burkina Faso): Retrospective study

With the goal of eradicating tsetse flies and trypanosomiasis in Africa, several control methods have been developed. One of this is the biological control through the application of the sterile insect technique (SIT) as a part of an area-wide integrated pest management. This method required the mass production of sterile males with a high competitiveness. The success of the tsetse mass rearing is strongly linked to the rearing conditions. The objective of this study was to do a retrospective evaluation of the impact of ambient conditions on the production performances of Glossina palpalis gambiensis at Insectary of Bobo Dioulasso. Data of productivity, fecundity, adult emergence and environmental conditions (temperature and relative humidity) of the rearing rooms were recorded from March to June 2020 and were analysed. The results showed a reduction of the normal pupae produced and the increase of soft pupae during this period. In addition, the relative humidity has shown a significant positive correlation with the production of soft pupae, whereas it had a significant negative correlation with the number of pupae produced per female per 10 days. However, the temperature variation during the period of the data recording didn’t have any impact on the production parameters. Rearing rooms need a better management to avoid large variations in environmental parameters.

The Fontanamare Discovery (Sardinia Coast, Italy), a Case of Underwater Corrosion of Bronze Coins

This study reports the analytical approach towards nine coins found in wreck A of Fontanamare for understanding the complex corrosion processes that take place in underwater conditions. Optical microscopy (OM) combined with micro-Raman (µ-Raman) spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM and EDS) were used to analyze the nature and the microstructure of the corrosion patina in comparison with the non-degraded state of coins. Three main types of corrosion patina based on copper, lead chloride, and carbonate were identified: black, white, and green, and the obtained results demonstrate the complex corrosion processes that take place in underwater conditions. To better understand the role played by different chemical and physical parameters in the corrosion of bronze artefacts in an underwater environment, this study attempts to understand the nature of the patinas on the coins in relation to the specific structural and environmental parameter variation.

Field measurement of environmental parameters in solar greenhouses and analysis of the application of passive ventilation

Solar greenhouses are passive agricultural facilities that can realize off-season production. The growth of crops in greenhouses is affected by various environmental parameters. Therefore, it is necessary to understand the variations of environmental parameters in solar greenhouses through field testing to improve their internal environment. Through field tests, it was found that the temperature variation in solar greenhouses was positively correlated with the change in solar radiation. When the top vent was opened, the minimum temperature in the greenhouse remained higher than 30 °C. The temperature gradient in the tall-plant greenhouse was twice that in the short-plant greenhouse. The relative humidity at the bottom of the tall-plant greenhouse remained greater than 65%. Top-vent opening for greenhouse ventilation is not conducive to the cooling and dehumidification of these relatively large sized greenhouses tested in this study. Passive ventilation via an integrated solar chimney and earth-air heat exchanger was applied in an experimental solar greenhouse. The results showed that when the passive ventilation was turned on, the indoor air temperature in the horizontal and vertical direction could be maintained in the range of 25 ∼ 28 °C and 25 ∼ 30 °C, respectively. The air temperature in the vertical direction had been decreased by approximately 3.5 to 6.5 °C. The passive ventilation effectively prevented continuous increases in indoor temperature, improved indoor air distribution and was conducive to the normal growth of crops.

Anatomical, morphological and physiological leaf characters of black betel (Piper betle L. var. nigra) in varying natural and man-made habitats

Abstract. Kuswandi PC, Ariyanti NA, Yunus MF, Amri CNAC. 2023. Anatomical, morphological and physiological leaf characters of black betel (Piper betleL. var. nigra) in varying natural and man-made habitats. Biodiversitas 24: 3236-3244. Piper betle L. var. nigra or black betel (known as Sirih hitam in Indonesia) contains valuable secondary metabolites, such as alkaloids, flavonoids, saponins, tannins, phenols, carotenoids, steroids and terpenoids. Black betel leaf extract has been shown to have antimicrobial activity thus there is a prospect to be developed as a promising herbal plant. Nevertheless, little information is available about its development as a medicinal plant. This research studies the influence of different habitats on several characters of black betel leaves with the aim to understand the suitable environmental conditions for the optimum growth of black betel plants. We used a survey method and random sampling of black betel leaves in four locations in Java Island, Indonesia, namely Banyuwangi which represents natural habitat, and Karanganyar, Ngaglik and Pakem which represent man-made habitats. Measurements of temperature, humidity, soil moisture and light intensity were carried out at each location. Analyses of leaf area, leaf water content, total leaf chlorophyll content and flavonoid content were undertaken and statistically analyzed using SPSS software. Leaf transverse sections were also observed. The results showed that the environmental parameters differed in the four locations. Leaves samples from the natural habitat in Banyuwangi were significantly different (P<0.05) from the three man-made habitats for chlorophyll and flavonoid content. For water content, significant difference was only for Banyuwangi samples with those from Karanganyar and Pakem. For leaf area, significant difference was only found between the Banyuwangi samples and Karanganyar. Observations on the transverse cross section of midrib of black betel leaves from the four locations showed structures that are generally found in Piper betle species, namely the presence of an epidermal layer, trichomes in the abaxial part of the leaf, several layers of the hypodermis, visible vascular tissue and the presence of secretion cells. There were several differences in the leaf anatomy such as greater number of trichomes on the leaves from Karanganyar, the secretory cells that were more visible in the leaves from Ngaglik and Banyuwangi and the sclerenchymal tissue that was more visible in the leaves from Banyuwangi. Such differences are likely influenced by variations in environmental parameters thus showing that the man-made habitat in the Karanganyar location can affect leaves characters similar to black betel plant grown in its natural habitat in Banyuwangi.

Public Health Risks Assessment of Bioaerosols from Different Locations in Bariga Metropolis of Shomolu Local Government Area, Lagos State, Nigeria

The increasing human populations and their daily activities have contributed to bioaerosols generation in Bariga, leading to air pollution with consequent public health threats to exposed individuals. This study aimed to assess public health risks associated with bioaerosols generated from outdoor activities in Bariga community, Shomolu Local Government Area of Lagos State. An analytical observational study design based on the measurement of meteorological parameters in the field and laboratory analysis of bioaerosol particles collected from the study population using a handheld Kestrel 3000 weather meter and standard microbiological procedures, respectively, was adopted. Four hundred (400) samples of bioaerosol particles obtained by the Taro Yamani formula at a 5% level of precision were analyzed. Passive air monitoring using Koch’s sedimentation method was employed for total viable counts, while microbial isolates were identified using cultural, morphological, and biochemical characterization. The variation in environmental parameters obtained was largely dependent on time and seasons, with a consequent adverse effect on the presence and movement of bioaerosol particles in the atmosphere. Microbial populations varied in densely and less-densely populated study areas. The study identified Bariga as a high-risk area with CFU above 102 –104 CFU/m3, thus capable of causing bioaerosols-related diseases. A total of twelve (12) bacterial and six (6) fungal genera were isolated, with Gram-positive bacteria having a prevalence rate of 87.02% and Gram-negative bacteria at 12.99%. The predominant fungi, on the other hand, were 87.94% mold and 12.06% yeast. One-way analysis of variance (ANOVA) at 0.05 significance level showed a significant correlation (F-ratio ˃ F-critical value) (p=0.05) between exposure to bioaerosol particles and associated health risks in the exposed individuals. We recommend that Lagos State Government should intensify efforts to reduce the public health effect of bioaerosols through policies, structural planning, development, and education on environmentally friendly activities and personal hygiene

Copepod assemblage structure in a tropical eutrophic estuarine system in the Southwestern Atlantic Ocean: Ecological indicators and functional groups

Changes in the structure of copepod assemblages and their functional groups because of variations in environmental and water quality parameters were examined in Guanabara Bay, which is a heavily eutrophic system. Monthly samples were collected over 2 years from 2012 to 2013. Most environmental and water quality parameters, and copepod assemblage diversity and evenness, varied between the annual dry and rainy periods. Opportunistic broadcast-spawning species were the most abundant in the system, most commonly those with mixed feeding strategies. Copepod abundance, taxonomic and functional assemblage indices, and primary functional groups of copepods were negatively affected by increased water quality parameters. These results showed that even in the Guanabara Bay area with great water circulation, pollution negatively affected copepod assemblages. This study also illustrated the importance of analyzing functional diversity and groups for the realistic diagnosis of functioning assemblages and ecosystems.

Opening the black box of winter: Full‐year dynamics of crustacean zooplankton along a nearshore depth gradient in a large lake

AbstractPast studies of zooplankton seasonality in large temperate lakes have often neglected the winter period. Winter conditions are rapidly changing (e.g., reduced ice cover extent and duration, altered thermal and mixing regimes) in northern lakes, making it important to fill the existing winter knowledge gap. In this study, we sampled five stations in Lake Superior across a nearshore depth gradient through the full year to assess the phenology of crustacean zooplankton communities and the effect of environmental drivers on them. Across stations, zooplankton densities were the lowest in winter (0.9 ± 0.6 Ind. L−1) and highest in summer (14.2 ± 15.1 Ind. L−1). Zooplankton abundances and community composition were less seasonally variable at deeper stations compared to shallower and more terrestrially affected regions. Cladocerans were the dominant taxonomic group during the summer across all stations, while cyclopoid and calanoid copepods were more important during the fall, winter, and spring. Among feeding groups, herbivores were most abundant in summer while omnivores and carnivores dominated in winter. We found that water temperature and food availability were the main drivers of total zooplankton densities through the year and during the cold seasons, but the effect of these factors varied among the main taxonomic groups. Our study demonstrates seasonal and spatial variation in crustacean zooplankton and environmental parameters, with the highest fluctuation at shallower stations. This study offers new information on seasonal crustacean zooplankton dynamics and contributes to understanding the effects of climate change on large lake ecosystems.

Elevated nutrients and surface chlorophyll-α associated with natural methane seeps in the Haima cold seep area of the Qiongdongnan Basin, northern South China Sea

Cold seeps are a significant source of methane to the ocean. However, nutrients and Chl-α in the euphotic layer overlying cold seeps have been poorly studied. Variations in Chl-α, nutrients, environmental parameters, and CH4 concentrations in the Haima cold seeps were analyzed. Results show that the overlying water exhibits a typical low nutrient and low Chl-α marine environment. Phosphate and Chl-α were significantly elevated, and the average SCM in cold seeps was much higher than that in control stations. Spearman correlation analysis indicated Chl-α in cold seep was positively correlated with salinity and negatively with nutrient and CH4 concentrations. It implied that the CH4 concentrations may promote the increase of Chl-α, and may be linked to CH4 plumes, bringing cold, nutrient-rich waters to the thermocline. However, due to the CH4 plumes hardly to track, more sampling is needed to determine the effects on Chl-α and phytoplankton in the euphotic layer.

Depositional Environment and Lithofacies Analyses of Eocene Lacustrine Shale in the Bohai Bay Basin: Insights from Mineralogy and Elemental Geochemistry

AbstractThe effect of various depositional parameters including paleoclimate, paleosalinity and provenance, on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment. The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity. The lower 3rd member of the Eocene Shahejie Formation (Es3x shale) was selected for this study, as one of the main prospective intervals for shale oil exploration and development in the intracratonic Bohai Bay Basin. Mineralogically, it is composed of quartz (avg. 9.6%), calcite (avg. 58.5%), dolomite (avg. 7%), pyrite (avg. 3.3%) and clay minerals (avg. 20%). An advanced methodology (thin‐section petrography, total organic carbon and total organic sulfur contents analysis, X‐ray diffraction (XRD), X‐ray fluorescence (XRF), field‐emission scanning electron microscopy (FE‐SEM)) was adopted to establish shale lithofacies and to interpret the depositional environment in the lacustrine basin. Six different types of lithofacies were recognized, based on mineral composition, total organic carbon (TOC) content and sedimentary structures. Various inorganic geochemical proxies (Rb/Sr, Ca/(Ca + Fe), Ti/Al, Al/Ca, Al/Ti, Zr/Rb) have been used to interpret and screen variations in depositional environmental parameters during the deposition of the Es3x shale. The experimental results indicate that the environment during the deposition of the Es3x shale was warm and humid with heightened salinities, moderate to limited detrital input, higher paleohydrodynamic settings and strong oxygen deficient (reducing) conditions. A comprehensive depositional model of the lacustrine shale was developed. The interpretations deduced from this research work are expected to not only expand the knowledge of shale lithofacies classification for lacustrine fine‐grained rocks, but can also offer a theoretical foundation for lacustrine shale oil exploration and development.

The ichnology of shallow-marine and transitional environments

Abstract The ichnology between marine and non-marine environments is a key field of work concerning the understanding of the variation of environmental parameters in inland-to-offshore transitional environments. In order to understand the geological and palaeobiological processes at these locations, this Special Publication attempts to discuss records in shallow-marine and transitional environments throughout the Phanerozoic, including topics such as ichnotaxonomy, ichnofacies analysis, ichnofabric analysis for records from both shallow-marine and transitional environments, and neoichnological aspects. The volume includes 14 papers in total: one focused on aspects of neoichnology in rock iguanas in coastal settings, nine concerning various shallow-marine palaeoenvironment topics and four addressing issues about dinosaur tracks in transitional environments.

Seasonality and growth in tropical freshwater ectotherm vertebrates: Results from 1-year experimentation in the African gray bichir, giraffe catfish, and the West African mud turtle.

Growth in ectotherm vertebrates is strongly rhythmed by seasonal variation in environmental parameters. To track the seasonal variation in ancient times in a continental and tropical context, we aim to develop a method based on the use of the growth rate of fossil ectotherm vertebrates (actinopterygians and chelonians) influenced by seasonal environmental fluctuations they experienced in their lifetime. However, the impact of environmental parameters on growth, positive or negative, and its intensity, depends on the taxa considered, and data are scarce for tropical species. For 1 year, an experiment was conducted to better understand the effect of seasonal variation in environmental parameters (food abundance, temperature, and photoperiod) on the somatic growth rate of three species of tropical freshwater ectotherm vertebrates: the fishes Polypterus senegalus and Auchenoglanis occidentalis and the turtle Pelusios castaneus. Mimicking seasonal shifts expected to be experienced by the animals in the wild, the experiment highlighted the preponderant effect of food abundance on the growth rate of those three species. Water temperature variation had a significant effect on the growth rate of Po. senegalus and Pe. castaneus. Moreover, the photoperiod demonstrated no significant effect on the growth of the three species. The duration of application of starvation or cool water conditions, ranging from 1 to 3months, did not affect the growth rate of the animals. However, Pelusios castaneus showed a temporary sensitivity to the return of ad libitum feeding or of warm water, after a period of starvation or cool water, by a period of compensatory growth. Finally, this experiment revealed, in the three species, fluctuations in the growth rate under controlled and constant conditions. This variation, similar to the variation in precipitation and temperature observed in their native environment, could be linked to a strong effect of an internal rhythm controlling somatic growth rate.

Three stages in the variation of the depth of hypoxia in the California Current System 2003–2020 by satellite estimation

The depth of hypoxia (DOH) is the shallowest depth at which the waters become hypoxic (oxygen concentration < 60 μmol kg−1), is a crucial indicator of the formation and expansion of oxygen minimum zones (OMZs). In this study, a nonlinear polynomial regression inversion model was developed to estimate the DOH in the California Current System (CCS), based on the dissolved oxygen profile detected by the Biogeochemical-Argo (BGC-Argo) float and remote sensing data. Satellite-derived net community production was used in the algorithm development, to denote the combined effect of phytoplankton photosynthesis and O2 consumption. Our model performs well, with a coefficient of determination of 0.82 and a root mean square error of 37.69 m (n = 80) from November 2012 to August 2016. Then, it was used to reconstruct the variation in satellite-derived DOH in the CCS from 2003 to 2020, and three stages of the DOH variation trend were identified. From 2003 to 2013, the DOH showed a significant shallowing trend due to the intense subsurface O2 consumption caused by strong phytoplankton production in the CCS coastal region. The trend was interrupted by two successive strong climate oscillation events from 2014 to 2016, which led to a significant deepening of the DOH and a slowing, or even reversal, of the variations in other environmental parameters. After 2017, the effects of climate oscillation events gradually disappeared, and the shallowing pattern in the DOH recovered slightly. However, by 2020, the DOH had not returned to the pre-2014 shallowing characteristic, which would lead to continuing complex ecosystem responses in the context of global warming. Based on the satellite inversion model of DOH in the CCS, we provide a new insight on the high-resolution spatiotemporal OMZ variations during an 18-year period in the CCS, which will aid in the evaluation and prediction of local ecosystems variation.