Seasonal Occurrence Research Articles

Relationships of the Cyprideis torosa (Ostracoda, Crustacea) with Seasonal Occurrences, Carapace Type and Physicochemical Variables in Kocaçay Delta (Türkiye)

To understand the spatial and temporal continuing occurrence patterns and relationships of Cyprideis torosa to several physicochemical variables, monthly samples from seven stations were collected from Kocaçay Delta (Bursa, Türkiye) between 2018 and 2019. Four (Cyprideis torosa, Koencypris ornata, Candona cf. lindneri, Candona meerfeldiana) of 14 ostracod taxa are new records for the ostracod fauna of Bursa province, where the total numbers of recent species increased to 33. Cyprideis torosa was the only dominant species found in almost all samples throughout the sampling. Based on the carapace type of the species, three groups can be divided as i) Type-1 (smooth carapaces), ii) Type-2 (noded carapaces), and iii) Type-3 (carapaces noded on one valve and smooth/rare on the other). Different occurrence patterns of the species with overlapping ecological ranges were observed among the stations. Except for station 1, all the types were encountered from other stations. Beginning from December 2018, nearly all populations had mostly Type-1 individuals until March. During April-May, individuals with Types-2 and 3 appeared to increase until October, while individuals in the Type-2 group were solely found from three stations (2, 3, and 5) in March and May 2018. There was a significant difference in salinity, magnesium, and calcium values among the stations (P<0.05) but only total nitrogen, temperature, and calcium showed a medium correlation to carapace type. In all cases, populations with noded individuals were found in narrower ecological ranges for those variables than other populations with smooth individuals.

Data-Driven Machine Learning Techniques for the Prediction of Cholera Outbreak in West Africa

The cholera epidemic remains a public threat throughout history, affecting vulnerable populations living with unreliable water and substandard sanitary conditions. Various studies have observed that the occurrence of cholera has a strong linkage with environmental factors such as climate change and geographical location. Poor Hygiene has been strongly linked to the seasonal occurrence and widespread of cholera through the creation of weather patterns that favour the disease’s transmission, infection, and the growth of Vibrio cholerae, which cause the disease. Over the past decades, there have been great achievements in developing epidemic models for the proper prediction of cholera. However, machine learning techniques have not been explicitly deployed in modelling cholera epidemics due to the challenges that come with its datasets, such as imbalanced data and missing information. This paper explores the use of machine learning algorithms such as decision tree, random forest, and logistics regression to evaluate the prevalence of cholera epidemics in West African countries while overcoming the data imbalance problem. In addition, mean square error, mean absolute error, F1 score, precision and balanced accuracy metrics were used to evaluate the performance of the three (3) models. The results show that logistic regression has an accuracy of 0.47%, random forest 0.978% and the most efficient model was the decision tree 0.998% with a mean squared error and mean absolute error of 0.001% respectively shows that the model will accurately predict cholera outbreak in Africa. Overall results will improve the understanding of the significant roles of machine learning techniques in healthcare data. The study recommends a review of healthcare systems to facilitate quality data collection and deployment of machine learning techniques

An illustrated guide to lady beetles (Coleoptera: Coccinellidae) of the Indian Subcontinent. Part 1. Tribe Coccinellini.

An illustrated guide to the tribe Coccinellini (Coleoptera: Coccinellidae: Coccinellinae) of the Indian Subcontinent comprising 119 species of 30 genera is presented. Brief diagnostic accounts of the genera and the species included therein are given with supporting illustrations of diagnostic characters, including genitalia, wherever available. Details of distribution, prey and plant associations, and seasonal occurrence are provided based on collections, label data and literature. For 31 species, illustrations of the life stages are included to facilitate the field identification of the immature stages. Adalia puetzi Iablokoff-Khnzorian, 1986 is synonymized with Adalia simmondsi Kapur & Sudha Rao, 1962 (new synonym). Oenopia smetanai Canepari, 1997 is removed from synonymy with O. flavidbrunna Jing, 1986 and restored as a valid species (status revised). Illeis kapuri Anand, Gupta & Ghai is transferred to Ortalia Mulsant, 1850 (new combination). Two new species, Harmonia andamanensis sp. n. and Phrynocaria prathapani sp. n. are described and illustrated from the Andamans and the Western Ghats, respectively. Coelophora lushuiensis (Jing, 1992) is documented as a new record for India (Manipur). An updated checklist of the Coccinellini of the Indian Subcontinent is also provided.

Birds of SABAP2 pentad 2915_2555 on the Jagersfontein Road, south-west of Bloemfontein, Free State

This paper describes results of a bird survey done at Pentad 2915_2555 on the Jagersfontein road south-west of Bloemfontein between April 2008 and January 2023. A total of 197 species have been recorded from mainly 169 full-protocol SABAP2 cards (162 done by author) and more than 30 ad hoc lists. The seasonality of waterbird species is discussed based on responses and occurrences after the rainfall seasons. Higher reporting rates were obtained for species such as Yellow-billed Ducks (49.7%), Red-billed Teals (37.9%) and White-faced Whistling Ducks (32.0%) during the summer months, which were sometimes still present into the drier winter months. Spur-winged Goose (39.6%) and Egyptian Goose (69.2%) also have high reporting occurrences, although South African Shelducks showed a more seasonal occurrence with lower reporting rates (17.8%). The seasonality of winter visiting species such as Swallow-tailed Bee eater and Sickle-winged Chats is discussed. Sickle-winged Chats were mostly observed in the area between April–August preferring low shrubs in open patches in grassland and on gravel roads. Swallow-tailed Bee eater were observed in the Buddleja sp. bush areas on the slope of the hill at the Praalhoek farm between May and July. The seasonal occurrence of Melodeuis Larks, which starts singing after the first summer rains, is also discussed. The ongoing monitoring of bird populations through the SABAP2 project (and with other platforms such as the Virtual Museum digitization projects) is emphasized and therefore the importance of monitoring bird populations over time.

Seasonal Occurrence of the Indian Ocean Blue Whale (Balaenoptera musculus indica) off South Coast of Sri Lanka

This paper describes the distribution, abundance and seasonal variation in blue whales (BWs) on the south coast of Sri Lanka, off Mirissa, where they are faced with anthropogenic threats. Data collection encompassed opportunistic sightings by whale-watching (WW) operations. This study revealed that large aggregations of BWs consistently overlapped with busy shipping lanes located between Dondra Head and Galle within important foraging and breeding regions on the south coast. Throughout 2015 (except June and July), 729 BWs were sighted over 177 sighting days. The sighting frequency was higher during the northeast monsoon and the first intermonsoon and lower throughout the second intermonsoon (n = 9) and latter part of the southwest monsoon. The highest frequencies of BW encounters per day occurred in April (n = 15) and December (n = 20), while the mean annual group size per sighting was 3.07 ± 0.24. From the January-to-April season, 13 mother–calf combinations and 1 pregnant cow were sighted off the southern coastline of Mirissa, suggesting the calving season peaks between the months of March and April in Sri Lanka. As this important habitat overlapped with the busiest shipping lanes, fishing and commercial whale-watching activities, the authorities have to take action toward the conservation of this ecosystem and whales as well as their safe navigation.

Occurrence, removal, emission and environment risk of 32 antibiotics and metabolites in wastewater treatment plants in Wuhu, China

Wastewater treatment plants (WWTPs) are considered important sources of antibiotics and metabolites in aquatic environments and pose a serious threat to the safety of aquatic organisms. In this study, we investigated the seasonal occurrence, removal, emission, and environmental risk assessment (ERA) of 32 antibiotics and metabolites at four WWTPs located in Wuhu, China. The main findings of this study are as follows: Ofloxacin concentrations dominated all WWTPs, and large quantities of sulfachinoxalin were only detected in WWTP 2 treating mixed sewage. The average apparent removal of individual parent antibiotics or metabolites ranged from −94.7 to 100 %. There was a noticeable seasonal emission pattern (independent t-test, t = 9.89, p < 0.001), with lower emissions observed during summer. WWTPs discharged 85.2 ± 43.8 g of antibiotics and metabolites each day. Approximately 87 % of emissions were discharged into the mainstream of the Yangtze River, while the remainder were discharged into its tributary, the Zhanghe River. The total emissions of 21 parent antibiotics were approximately 18 % of the prescription data, indicating that a considerable and alarming amount of prototype drugs entered the receiving water body. Based on the risk quotient (RQ) of the ERA, the Zhanghe River has a moderate risk of ofloxacin (RQ = 0.111–0.583), a low or insignificant risk of sulfamethoxazole (RQ = 0.003–0.048), and an insignificant risk of other antibiotics or metabolites. However, the risk of antibiotics or metabolites in the mainstream of Yangtze River is insignificant. This study could help understand the seasonal emission patterns of antibiotics and metabolites, as well as more antibiotics sensitive of environmental risks in tributary than that in mainstream.

Spatial and temporal differences in surface and subsurface meltwater distribution over Greenland ice sheet using multi-frequency passive microwave observations

Increasingly larger portions of the Greenland ice sheet are undergoing seasonal melting-refreeze cycles due to global climate warming. The cycle begins with the arrival of high temperatures and increased solar radiation in the spring and summer seasons generating meltwater on the ice sheet's surface. Meltwater percolates to deeper ice layers, either refreezing within the firn, creating longer-term meltwater pockets (firn aquifers), or generating peripheral runoff. Depending on the location and climate, the refreeze duration, the depth of infiltration, and meltwater persistence are temporally and spatially complex. Our recent study showed that multi-frequency passive microwave measurements in the 1.4 GHz to 36.5 GHz range effectively distinguished seasonal meltwater between the immediate surface and deeper firn layers at an experiment site in the accumulation zone of the southwestern Greenland ice sheet. Here, we further explored the vertically and horizontally polarized multi-frequency melt response at the pan-Greenland scale. We employed 1.4 GHz brightness temperature (TB) measurements from the NASA Soil Moisture Active Passive (SMAP) satellite and 6.9, 10.7, 18.9, and 36.5 GHz TB measurements from the JAXA Global Change Observation Mission-Water Shizuku (GCOM-W) satellite. The results show that the frequency-dependent response was consistent across the ice sheet. The multi-frequency melt indications match with lasting seasonal subsurface meltwater with delayed refreezing compared to the surface. These results suggest persistent seasonal subsurface meltwater occurrences that are spatially and temporally significant but concealed from the high-frequency observations. Retrieving the meltwater evolution in snow and firn presents a complex problem; this work represents an initial step toward developing an ice-sheet-wide algorithm for more comprehensive retrieval of the meltwater profile.

Variability in the occurrence of thermal seasons in Poland in 1961–2020

AbstractThe article analyses the variability of thermal seasons in Poland in 1961–2020. Based on the average monthly air temperature values from 55 stations, the onset and end dates as well as the duration of the six thermal seasons were calculated. Taking into account the thermal thresholds of 0°C, 5°C and 15°C for each year, early spring, spring, summer, autumn, early winter and winter can be distinguished. A significant spatial differentiation of the dates of the beginning and duration of the thermal seasons in Poland was observed. The influence of continentalism (in the east) and oceanic climate (in the west) and the influence of the Baltic Sea are noticeable, and in mountainous regions, altitude above sea level is the main factor. The air temperature in Poland increases at the rate of 0.3°C–0.4°C/10 years. This causes significant changes in the occurrence and duration of the thermal seasons. An early beginning of early spring and spring was observed. Summer arrives earlier and is significantly longer, becoming the longest season of the year (above 110 days in the south of Poland). Autumn and early winter are delayed and get shorter, whereas winter comes much later. Throughout the country, winter is 44 days shorter, and in the north‐west it does not occur at all. Changes in the onset of thermal seasons are a clear indicator of progressing global warming. They have also a decisive impact on the environment and human activity.

Seasonal Occurrence of Greater Banded Hornet (Vespa tropica Linn.) in Western Honey Bee (Apis mellifera Linn.) Colonies under Terai Agro-ecological Region of West Bengal

The present study was conducted during September, 2018 to August, 2020 on the seasonal incidence of Vespa tropica Linn. on Apis mellifera Linn. under terai agro-ecological region of West Bengal, India. Ten numbers of A. mellifera colonies of similar strength was placed in the apiary unit of Uttar Banga Krishi Viswavidyalaya, West Bengal, India in which no pest management strategies were carried out. Incidence of V. tropica was recorded higher during July to October peaking in the month of July (251.50±22.17 visits day-1) with annual average success rate of 57.23%±1.16%. From December to March little or no incidence was recorded. Minimum abundance of hornets was recorded at 07:00–09:00 hours. After that incidence started increasing with maximum incidence recorded at 13:00–15:00 hours i.e., 43.52±11.97 visits to the bee colonies day-1 during this time gap. Both maximum and minimum temperature and relative humidity showed significantly positive correlation with the incidence of V. tropica. However, rainfall was found to be detrimental for their incidence as it showed negative and non-significant correlation with their incidence. As V. tropica has been considered as a major enemy of honey bees, so the results obtained from the study can be used for designing integrated pest management strategies against this pest that will allow the beekeepers to focus on that particular time period when this pest is more abundant.

Changes in atmospheric moisture transport over tropical South America: an analysis under a climate change scenario

Warming induced by increased greenhouse gas emissions is intensifying the global water cycle and increasing the water vapor content of the global atmosphere. However, there is a lack of scientific literature assessing how regional atmospheric moisture transport and recycling will change in a warming climate. This work analyzes the projections of atmospheric moisture transport and recycling over tropical South America by the end of the twenty-first century (2070–2100) under a climate change scenario (RCP8.5). We used the Dynamic Recycling Model to estimate atmospheric moisture contributions to the region considering input data from the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis and 11 models included in the Fifth Phase of the Coupled Model Intercomparison Project. Projected increases of precipitable water in tropical South America are linked with increased evaporation from the oceans. However, those projections also indicate (1) reductions in the precipitation contributed by the main atmospheric moisture sources to the continental regions of tropical South America, (2) reductions of total precipitation, and (3) reductions of recycled precipitation over the region. The largest reductions of precipitation recycling are projected over the southern Amazon during the dry-to-wet transition season (about 31%) and the northern Amazon during its dry season (about 25%). This is particularly relevant since the southern Amazon has experienced the occurrence of longer dry seasons during the recent decades and has been highlighted as a hotspot of climate change.

Seasonal occurrence and environmental drivers of pelagic shark species in Los Cabos, Mexico, assessed using citizen science

Seasonal occurrence and environmental drivers of pelagic shark species in Los Cabos, Mexico, assessed using citizen science

Seasonal fluctuations and diversity of Ingoldian mycobiota in two water bodies receiving different effluents at Assiut Governorate (Upper Egypt)

In the current study, fifty-eight Ingoldain fungal species assignable to forty-one genera were recovered from two water bodies receiving the treated sewage and the effluents of oils and soaps factory at Assiut Governorate (Upper Egypt), of which Anguillospora, Amniculicola, Flagellospora, and Mycocentrospora were the most prevalent genera. The most widespread identified species were Anguillospora furtive, Amniculicola longissima and Flagellospora fusarioides. Forty-three species were identified for the first time in Egypt. The most Ingoldain taxa were estimated for El-Zinnar canal, with the highest recorded taxa in winter. Whereas, the highest dominance of Ingoldian fungi was estimated for the El-Ibrahimia canal. The highest Simpson and Shannon diversity indexes were estimated for El-Zinnar canal samples recording 0.9683 and 3.741, respectively. The poorest water sites with Ingoldian fungi were those exposed directly to either treated sewage or industrial effluents, with which relatively higher values of water conductivity, cations and anions. Water temperature was the main abiotic factor driving the seasonal occurrence of Ingoldian fungi. It is interesting to isolate some Ingoldian fungal species from the stressful water sites receiving the effluents which provide valuable insights regarding their adaptation, predictive and putative role as bioindicators and their potentiality in pollutants degradation, organic decomposition, and transformation of xenobiotic compounds.

Drivers of Physical and Biological Frontal Variability in the Northern California Current System

AbstractOceanic fronts mark the boundary between two water masses and are often sites of complex bio‐physical processes and multi‐trophic level interactions, making them particularly important features in marine ecosystems. As global climate change induces multi‐scale shifts in the driving physical mechanisms of fronts, spatiotemporal tracking of frontal variability can aid in efforts to understand the downstream effects on marine biodiversity and ecosystem structure. Here we focus on fronts within the dynamic northern extent of the California Current System (NCC). We derived mesoscale sea surface temperature (SST) and chlorophyll‐a (chl‐a) fronts across the NCC region from 4‐km MODIS‐Aqua L3 daily fields over 2003–2019. Mesoscale physical (SST) and biological (chl‐a) fronts were often adjacent and coherent in their seasonal and interannual occurrence frequencies, but were spatially decoupled. SST fronts were most frequent and broadly distributed offshore while chl‐a fronts mostly occurred along the continental shelf break, particularly from Vancouver Island to central Oregon. Additionally, we employed a standardized multiple linear regression analysis to quantify the relative influence of local‐ and basin‐scale processes on frontal variability in the NCC. Local wind stress and wind stress curl variability were the most influential drivers of fronts over the shelf, while basin‐scale climate variability (i.e., climate oscillations) significantly drove frontal occurrences along the shelf break and offshore. Given predictions in the intensification of coastal upwelling in systems such as the NCC, our results indicate that oceanic response to climate change driven atmospheric variability will significantly impact the NCC marine ecosystem on the mesoscale.

イネカメムシ（カメムシ目：カメムシ科）の水田での発生消長と卵巣の発育状況

We investigated the seasonal occurrence of the rice stink bug, Niphe elongata (Hemiptera: Pentatomidae), in paddy fields and the ovarian development of females collected from fields in Shiga Prefecture, Japan. Early in August, when the rice ears of medium-maturing varieties emerged, adult bugs migrated to the paddy field, and the females laid eggs. The eggs hatched, and nymphs grew into adults. When late-maturing rice varieties started heading in late August, the adults entered the paddy field, and the females laid eggs. The eggs hatched, and the nymphs became adults. Therefore, in Shiga Prefecture, the life cycle of the rice stink bug produces two generations in 1 year. In September, no females had mature eggs in their ovaries, and adult bugs were believed to overwinter.

No evidence for seasonal variations of the incidence of testicular germ cell tumours in Germany.

The pathogenesis of testicular germ cell tumours (GCTs) is still incompletely understood. Any progress in its understanding must derive from observational studies. Recently, it has been suggested that the incidence of GCTs may follow a seasonal pattern based on circannual changes in the Vitamin D serum levels, with maximum incidence rates in winter months. To examine this promising hypothesis, we studied monthly incidence rates of testicular GCTs in Germany by analysing 30,988 GCT cases aged 15-69 years, diagnosed during 2009-2019. Monthly incident case numbers with data regarding histology and patient age were obtained from the Robert Koch Institut, Berlin, along with annual male population counts. We used precision weighting for deriving pooled monthly incidence rates for GCTs of the period 2009-2019. We stratified pooled rates by histology (seminoma and nonseminoma) and age (15-39 and 40-69 years). By assuming a cyclical effect, we used an estimator of the intensity of seasonal occurrence and report seasonal relative risks (RR). The mean monthly incidence rate was 11.93/105 person-months. The seasonal RR for testicular cancer over-all is 1.022 (95% CI 1.000-1.054). The highest seasonal RR was found in the subgroup of nonseminoma aged 15-39 years, with a RR 1.044 (95% CI 1.000-1.112). The comparison of the pooled monthly rates of the winter months (October-March) with the summer months (April-September) revealed a maximum relative difference of 5% (95% CI 1-10%) for nonseminoma, aged 15-39 years. We conclude that there is no evidence of a seasonal variation of incidence rates of testicular cancer. Our results are at odds with an Austrian study, but the present data appear sound because the results were obtained with precision weighted monthly incidence rates in a large population of GCT cases.

First hydrological study on the seasonal occurrence of glyphosate, glufosinate, and their metabolites in the Red River system, North Vietnam

We report the spatial and seasonal distribution of organophosphorus herbicides, namely glyphosate (GLYP), glufosinate (GLUF), and their respective metabolites aminomethyl phosphonic acid (AMPA) and 3-(methylphosphinico)-propionic acid (MPPA), in the Red River system (North Vietnam), a major water body in Southeast Asia. The four compounds were measured at 34 sampling stations located from upstream to the estuary during the dry (March) and wet (July) seasons in 2019. Large seasonal variations in herbicide concentrations were measured for the four analytes from upstream to the estuary, with the highest range of variations observed during the wet season. In the surface waters of the Red River, the maximum concentrations of GLUF (234 ng L–1), GLYP (565 ng L–1) and its metabolite AMPA (1329 ng L–1), occurred in the wet season. These values however, are lower than reported in other rivers worldwide. In contrast, the estimated fluxes of these compounds in the Red River water basin were very high during the wet season, i.e., up to 121, 50.2, 284, and 186 kg d–1 for GLYP, GLUF, AMPA, and MPPA, respectively. During both seasons, we observed correlations between the four compounds and ammonium (NH4+), suggesting that both nitrogen containing fertilizers and herbicides were applied in areas close to the river shore. The concentrations and fluxes of the herbicides GLYP, GLUF, and their metabolites determined in the Red River were compared to those recorded in other world river systems, such as the Garonne River (France), thus highlighting the importance of monitoring these compounds in surface waters.

Bird Biodiversity and Ringing Data Analysis at Shakpak Pass in the Tanirtau (2017-2022)

The Shakpak Pass, located in the foothills of the Western Tien Shan, is a significant migration route for birds. This work presents the ringing data collected between 2017 and 2022, providing insights into the diversity, abundance, and seasonal occurrence of bird species at the pass. The study reveals several key findings, including the identification of rare species, the documentation of migration patterns for both passerine and non-passerine species, and the notable reappearance of a species that had been absent for an extended period. These results deepen our understanding of avian ecology and biodiversity and underscore the importance of long-term monitoring efforts for effective conservation strategies.

An improved algorithm for detecting mesoscale ocean fronts from satellite observations: Detailed mapping of persistent fronts around the China Seas and their long-term trends

Mesoscale fronts are highly energetic ocean processes that dominate local biogeochemical processes and air-sea interactions and exert significant effects on ocean dynamics, ecology, and climate. An automatic front detection algorithm applied to satellite-based observations is a fundamental approach to acquiring frontal occurrence information. Histogram-based algorithms have been widely used in previous studies, and, despite being the most popular front detection algorithm, continuous improvements have been needed to address imperfect detection issues (undetected coastal fronts, discontinuities of fronts and repeated detection of fronts). In this study, a new algorithm is proposed to address the issues by coupling inverse distance weighting and mathematical morphology operators. Using 14,610 images acquired from 1982 to 2021, a series of comparisons between the new and existing algorithms have been implemented to validate the improvements. Statistical results suggest that the number of frontal pixels detected by our algorithm increased by 58.45% in the coastal domain when compared to previous methods. Statistical analysis also shows most of these increased fronts can be supported by a classic gradient-based method which is superior in detecting coastal fronts, which demonstrates the improvement of new algorithm in detecting coastal fronts. Furthermore, visual analyses suggest that our algorithm can better connect discontinuous fronts and reduce repeated detections, and statistical comparisons in the open seas present a 34.50% improvement in the average length of frontal segments. Moreover, based on an automated objective delineation method, an analysis of 40 years of seasonal frontal occurrences (as detected by our algorithm) produced a dataset that shows a detailed map of 59 persistent fronts around the China Seas. This map updates previously hand-delineated frontal positions and identifies some previously unreported persistent fronts. Further analyses show that the frontal occurrence or intensity of a majority of persistent fronts around the China Seas presents significant (P < 0.05) long-term variability over the last 40 years. The improved algorithm, together with its application in identifying persistent fronts around the China Seas, is expected to be extended to other waters to better investigate the response of marine ecosystems to front dynamics and predict the distribution of marine organisms within a changing climate.

Arabian Sea Humpback Whale (Megaptera novaeangliae) Singing Activity off Netrani Island, India

Arabian Sea humpback whales (Megaptera novaeangliae), listed as “Endangered” on the International Union for Conservation of Nature’s Red List, remain resident throughout the year in the waters of the Arabian Sea and constitute a genetically isolated population. In the eastern Arabian Sea, information on humpback whales off the Indian coast has largely been limited to stranding records, local ecological knowledge, and opportunistic visual sighting data. These data, along with information from a long-term study off Oman, suggest that humpback whales migrate across the Arabian Sea into Indian territorial waters from October to March. To study the presence of Arabian Sea humpback whales in Indian waters more comprehensively, passive acoustic monitoring (PAM) was initiated along the west coast of India in 2019. Male humpback whales produce complex songs with a stereotyped structure; these songs are shared within a population, and song patterns are known to evolve progressively over time. In this article, a structural analysis of humpback whale song recorded over four days off the coast of Netrani Island, Karnataka, India, in December 2019 is presented. Time-frequency features of 2,641 individual call units were analysed. Call units had a fundamental frequency bandwidth ranging from 149.98 to 541.65 Hz, with a duration ranging from 1.19 to 5.5 s. The call units were used to identify phrases and themes required to construct the structure of the song, which can potentially help identify the population to which singing individuals belong. This study indicates the need for a long-term PAM program across the Arabian Sea to compare whale songs across the region. Simultaneous recordings over multiple seasons will best assess population connectivity, seasonal occurrence, and movement patterns within and between populations across the Arabian Sea and the Indian Ocean.

Seasonal occurrence of microplastics in sediment of two South African recreational reservoirs

Inland water systems are regarded as a pathway and sink of plastic pollutants from the terrestrial environment. Aquatic ecosystems are globally contaminated with microplastics, but the spatiotemporal occurrence and density of microplastics in freshwater ecosystems remain poorly understood. The present study seasonally assessed differences in microplastic density in the sediments from two South African recreational reservoirs associated with low human activities (macadamia orchards) and high human activities (communal areas). Microplastics were recovered from all of the reservoirs assessed, indicating their extensive occurrence and densities. Microplastic numbers were significantly higher in reservoirs associated with high anthropogenic activities during the hot-dry season (140.6 particles kg−1 dwt) and lower in reservoirs associated with low anthropogenic activities during the hot-wet and cool-dry seasons, i.e., 22.60 particles kg−1 dwt and 16.13 particles kg−1 dwt, respectively. Overall, polypropylene (31%) and polystyrene (30%) were identified as the dominant types of microplastic polymer in both reservoir types. Moreover, no correlative relationships were observed for environmental parameters and microplastic densities across reservoirs and seasons, suggesting a widespread and largely context-independent pollution level. These results show that microplastics are not evenly distributed between waters associated with low human activities and high human activities. Future work should seek greater sample sizes and centre around observing microplastic contamination in the region by examining their sources, transport, and impacts to freshwater environments, whilst informing management strategies.