Temporal Variation In Occurrence Research Articles

Decadal trends and dynamics in the abundance and biomass of marine branchiopods in the southern part of the North Sea

Time-series are fundamental for enhancing our comprehension of plankton community dynamics and forecasting future changes that could significantly affect entire marine food chains and ecosystems. In this study, we investigated spatial and temporal variations in occurrence, abundance and body size of marine branchiopods in the Belgian Part of the North Sea (BPNS), using both traditional microscopy, as well as digital imaging (ZooSCAN). We studied the population dynamics of branchiopods collected between 2014 and 2021 in the BPNS and compared these results with a previously collected (2009–2010) dataset for the same area. The time series showed no significant changes in abundance (Podon spp., Evadne nordmanni) over the years, but we did observe a pronounced seasonal pattern, with both species completely absent in the winter months. Abundance and biomass were positively correlated with water temperature but negatively correlated with nutrient concentrations and turbidity. Additionally, Podon spp. abundance was negatively correlated with anthropogenic chemicals (i.e., polycyclic aromatic hydrocarbons). We employed generalized additive models to quantify the relative contribution of temperature, salinity, turbidity, chlorophyll a concentration and pollutant levels to the dynamics of the studied taxa. Turbidity and chlorophyll a concentrations were revealed to be the predictor with the highest importance in all models predicting the abundances/body size of the selected species. Anthropogenic chemicals were not informative in explaining branchiopod abundance or body size. The findings of this study establish a baseline for future studies, which is essential for our understanding of the zooplankton dynamics in the North Sea, particularly in the context of climate change and changing water quality.

Spatiotemporal variation in harbor porpoise distribution and foraging across a landscape of fear

AbstractUnderstanding spatiotemporally varying animal distributions can inform ecological understanding of species' behavior (e.g., foraging and predator/prey interactions) and support development of management and conservation measures. Data from an array of echolocation‐click detectors (C‐PODs) were analyzed using Bayesian spatiotemporal modeling to investigate spatial and temporal variation in occurrence and foraging activity of harbor porpoises (Phocoena phocoena) and how this variation was influenced by daylight and presence of bottlenose dolphins (Tursiops truncatus). The probability of occurrence of porpoises was highest on an offshore sandbank, where the proportion of detections with foraging clicks was relatively low. The porpoises' overall distribution shifted throughout the summer and autumn, likely influenced by seasonal prey availability. Probability of porpoise occurrence was lowest in areas close to the coast, where dolphin detections were highest and declined prior to dolphin detection, leading potentially to avoidance of spatiotemporal overlap between porpoises and dolphins. Increased understanding of porpoises' seasonal distribution, key foraging areas, and their relationship with competitors can shed light on management options and potential interactions with offshore industries.

An analysis of the spatio-temporal occurrence of anthelmintic veterinary drug residues in groundwater

Anthelmintics are antiparasitic drugs used to control helminthic parasites such as nematodes and trematodes in animals, particularly those exposed through pasture-based production systems. Even though anthelmintics have been shown to be excreted into the environment in relatively high amounts as unmetabolized drug or transformation products (TPs), there is still only limited information available on their environmental occurrence, particularly in groundwater, which has resulted in them being considered as potential emerging contaminants of concern. A comprehensive study was carried out to investigate the occurrence of 40 anthelmintic residues (including 13 TPs) in groundwaters (and associated surface waters) throughout the Republic of Ireland. The study focused on investigating the occurrence of these contaminants in karst and fractured bedrock aquifers, with a total of 106 sites (88 groundwaters and 18 surface waters) samples during spring 2017. Seventeen anthelmintic compounds consisting of eight parent drugs and nine TPs were detected at 22% of sites at concentrations up to 41 ng L−1. Albendazole and its TPs were most frequently detected residues, found at 8% of groundwater sites and 28% of surface water sites. Multivariate statistical analysis identified several source and pathway factors as being significantly related to the occurrence of anthelmintics in groundwater, however there was an evident localised effect which requires further investigation. An investigation of the temporal variations in occurrence over a 13 month period indicated a higher frequency and concentration of anthelmintics during February/March and again later during August/September 2018, which coincided with periods of increased usage and intensive meteorological events. This work presents the first detections of these contaminants in Irish groundwater and it contributes to broadening our understanding of anthelmintics in the environment. It also provides insight to seasonal trends in occurrence, which is critical for assessing potential future effects and implications of climate change.

An advanced hidden Markov model for hourly rainfall time series

The hidden Markov framework is adapted to construct a compelling model for simulation of sub-daily rainfall, capable of capturing important characteristics of sub-daily rainfall well, including: long dry periods or droughts; seasonal and temporal variation in occurrence and intensity; and propensity for extreme values. These adaptations include both clone states and temporally non-homogeneous state persistence probabilities. Set in the Bayesian framework, a rich quantification of parametric and predictive uncertainty is available, and thorough model checking is made possible through posterior predictive analyses. Results from the model are highly interpretable, allowing for meaningful examination of diurnal, seasonal and annual variation in sub-daily rainfall occurrence and intensity. To demonstrate the effectiveness of this approach, both in terms of model fit and interpretability, the model is applied to an 8-year long time series of hourly observations.

Seen or heard? A comparison of visual and acoustic autonomous monitoring methods for investigating temporal variation in occurrence of southern right whales

Passive acoustic detectors are widely used for monitoring distribution of cetaceans. Autonomous visual methods are less frequently employed; they are limited to detections during daylight and good weather, but offer potential advantages due to certainty of species’ identification and longevity of deployment. To compare performance of acoustic and visual methods, temporal changes in distribution of southern right whales, Eubalaena australis, were monitored in the remote sub-Antarctic Auckland Islands (50°31′S, 166°16′E). A time-lapse camera was deployed for 2 years from August 2010, taking an image every 70 min. The presence of whales was scored for each image taken during daylight (n = 8295). A passive acoustic recorder was deployed in August 2011, recording for 3.75 min every hour until battery life expired after 10 months. Each recording (n = 6978) was aurally reviewed. Both methods revealed a similar seasonal distribution; maximum detection rates were in the austral winter and no whales were detected in January or February. However, at the peak of right whale occurrence, the proportion of samples with whales detected was much higher for the acoustic recorder (93.9% in August) than the time-lapse camera (14.8%). A generalised additive model fitted to the visual data revealed significant effects of sea state and visibility. Acoustic detection rates were higher, probably because detection range is greater, and less affected by weather. The solar-powered time-lapse camera system, however, functioned effectively for much longer. We discuss the relative merits of visual and acoustic detectors and attempt to draw conclusions about their efficacy for different focal species and monitoring locations.

Occurrence of Emerging Micropollutants in Water Systems in Gauteng, Mpumalanga, and North West Provinces, South Africa.

The ubiquitous occurrence of emerging micropollutants (EMPs) in water is an issue of growing environmental-health concern worldwide. However, there remains a paucity of data regarding their levels and occurrence in water. This study determined the occurrence of EMPs namely: carbamazepine (CBZ), galaxolide (HHCB), caffeine (CAF), tonalide (AHTN), 4-nonylphenol (NP), and bisphenol A (BPA) in water from Gauteng, Mpumalanga, and North West provinces, South Africa using comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry (GCxGC-HRTOFMS). Kruskal-Wallis test and ANOVA were performed to determine temporal variations in occurrence of the EMPs. Principal component analysis (PCA) and Surfer Golden Graphics software for surface mapping were used to determine spatial variations in levels and occurrence of the EMPs. The mean levels ranged from 11.22 ± 18.8 ng/L for CAF to 158.49 ± 662 ng/L for HHCB. There was no evidence of statistically significant temporal variations in occurrence of EMPs in water. Nevertheless, their levels and occurrence vary spatially and are a function of two principal components (PCs, PC1 and PC2) which controlled 89.99% of the variance. BPA was the most widely distributed EMP, which was present in 62% of the water samples. The detected EMPs pose ecotoxicological risks in water samples, especially those from Mpumalanga province.

Hydrochemical modelling of water quality in terms of emerging micropollutants in Mpumalanga, Gauteng and North West Provinces

Emerging micropollutants (EMPs) are ubiquitous in aquatic systems and are associated with a wide range of eco-toxicological effects worldwide. There remains a lack of scientific understanding of the major underlying hydrochemical factors behind variations in concentration heterogeneities of EMPs in time and space. This study was therefore conducted to determine major hydrochemical processes controlling water quality and the occurrence of EMPs mainly, carbamazepine (CBZ), tonalide (AHTN), galaxolide (HHCB), caffeine (CAF), technical 4-nonylphenol (NP) and bisphenol A (BPA) in water from Mpumalanga, Gauteng and North West Provinces in South Africa. Grab water samples were collected bi-monthly between June 2014 and April 2016 from 44 water sources using standard sampling procedures. BPA, NP, CAF, HHCB, AHTN, CBZ were extracted, cleaned and enriched using autotrace-SPE at neutral pH and analyzed using GC × GC-TOFMS. Kruskal Wallis-test was used to test for temporal variations in occurrence of the analytes. The Geochemist's Workbench® Release 11 software, Surfer Golden Graphics for surface mapping, PHREEQC software and bivariate ion plots were used determine the major hydrogeochemical processes. The mean concentrations of EMPs varied from 3.48 μg/L for CAF to 421.53 μg/L for HHCB. Although the Kruskal Wallis test revealed no any statistically significant temporal variations in concentrations of the analytes in water samples at 95% confidence level, their occurrence and distribution vary spatially with BPA being the most widely distributed EMP and was present in 62% of the sampled sites. Municipal waste water inputs, agricultural pollution, ion-exchange reactions, carbonate and silicate weathering were the major processes controlling water quality in the study area. This study may assist water resource managers to ably address and manage water pollution resulting from a number of natural and anthropogenic hydrochemical processes in the study area.

Spatial and Temporal Variations in the Occurrence and Foraging Activity of Coastal Dolphins in Menai Bay, Zanzibar, Tanzania.

Understanding temporal patterns in distribution, occurrence and behaviour is vital for the effective conservation of cetaceans. This study used cetacean click detectors (C-PODs) to investigate spatial and temporal variation in occurrence and foraging activity of the Indo-Pacific bottlenose (Tursiops aduncus) and Indian Ocean humpback (Sousa plumbea) dolphins resident in the Menai Bay Conservation Area (MBCA), Zanzibar, Tanzania. Occurrence was measured using detection positive minutes. Inter-click intervals were used to identify terminal buzz vocalisations, allowing for analysis of foraging activity. Data were analysed in relation to spatial (location) and temporal (monsoon season, diel phase and tidal phase) variables. Results showed significantly increased occurrence and foraging activity of dolphins in southern areas and during hours of darkness. Higher occurrence at night was not explained by diel variation in echolocation rate and so were considered representative of occurrence patterns. Both tidal phase and monsoon season influenced occurrence but results varied among sites, with no general patterns found. Foraging activity was greatest during hours of darkness, High water and Flood tidal phases. Comparisons of echolocation data among sites suggested differences in the broadband click spectra of MBCA dolphins, possibly indicative of species differences. These dolphin populations are threatened by unsustainable fisheries bycatch and tourism activities. The spatial and temporal patterns identified in this study have implications for future conservation and management actions with regards to these two threats. Further, the results indicate future potential for using passive acoustics to identify and monitor the occurrence of these two species in areas where they co-exist.

AvianPlasmodiumlineages found in spot surveys of mosquitoes from 2007 to 2010 at Sakata wetland, Japan: do dominant lineages persist for multiple years?

The ecology and geographical distribution of disease vectors are major determinants of spatial and temporal variations in the transmission dynamics of vector-borne pathogens. However, there are limited studies on the ecology of vectors that contribute to the natural transmission of most vector-borne pathogens. Avian Plasmodium parasites are multihost mosquito-borne pathogens transmitted by multiple mosquito species, which might regulate the diversity and persistence of these parasites. From 2007 to 2010, we conducted entomological surveys at Sakata wetland in central Japan, to investigate temporal variation in mosquito occurrence and prevalence of avian Plasmodium lineages in the mosquito populations. A polymerase chain reaction (PCR)-based method was used to detect Plasmodium parasites and identify the blood sources of mosquitoes. Culex inatomii and C.pipiens pallens represented 60.0% and 34.8% of 11 mosquito species collected, respectively. Our results showed that the two dominant mosquito species most likely serve as principal vectors of avian Plasmodium parasites during June, which coincides with the breeding season of bird species nesting in the wetland reed beds. Fourteen animal species were identified as blood sources of mosquitoes, with the oriental reed warbler (Acrocephalus orientalis) being the commonest blood source. Although there was significant temporal variation in the occurrence of mosquitoes and prevalence of Plasmodium lineages in the mosquitoes, the dominant Plasmodium lineages shared by the two dominant mosquito species were consistently found at the same time during transmission seasons. Because vector competence cannot be confirmed solely by PCR approaches, experimental demonstration is required to provide definitive evidence of transmission suggested in this study.

Population surveillance of dementia mortality.

Geographic and temporal variation in occurrence of dementia within the US has received little attention despite its importance for generation of new etiologic hypotheses and health services research. We examine methodological problems in the use of vital statistics data for assessing variation over time, among states and within states in the US. We analyzed the US multiple cause of death files for 2005–2006 and 1999–2000 US deaths with Alzheimer’s Disease (International Classification of Disease 10th revision code G30) and other dementias (codes F01, F02, R54) coded as underlying or contributing cause of death based on the death certificate. Age-adjusted death rates were computed by year, state or county for persons aged 65 years and over. In 2005–2006 combined, 555,904 total deaths occurred with any dementia type (212,386 for Alzheimer’s disease) coded as underlying or contributing cause. Among the states, age-adjusted rates per 100,000 per year varied by two fold ranging from 458 in New York to 921 in Oregon. Similar geographic patterns were seen for Alzheimer’s disease. However, between 1999–2000 and 2005–2006 the US death rate for all dementia increased only from 559 to 695 (24%) while that for Alzheimer’s disease doubled from 135 to 266. Use of specific (G30, F01) versus non-specific diagnoses (F02, R54) varied among states and over time, explaining most of the temporal increase in rate of Alzheimer’s disease. Further research is needed to assess artifacts of diagnosis, certification or coding, utilization of health services, versus biological variation as possible causes of temporal and geographic variation to enhance utility of mortality data for dementia monitoring and research.

Spatial and temporal variations in species occurrence rate affect the accuracy of occurrence models

ABSTRACTAim Predictive models of species occurrence have potential for prioritizing areas for competing land uses. Before widespread application, however, it is necessary to evaluate performance using independent data and effective accuracy measures. The objectives of this study were to (1) compare the effects of species occurrence rate on model accuracy, (2) assess the effects of spatial and temporal variation in occurrence rate on model accuracy, and (3) determine if the number of predictor variables affected model accuracy.Location We predicted the distributions of breeding birds in three adjacent mountain ranges in the Great Basin (Nevada, USA).Methods For each of 18 species, we developed separate models using five different data sets — one set for each of 2 years (to address the effects of temporal variation), and one set for each of three possible pairs of mountain ranges (to address the effects of spatial variation). We evaluated each model with an independent data set using four accuracy measures: discrimination ability [area under a receiver operating characteristic curve (AUC)], correct classification rate (CCR), proportion of presences correctly classified (sensitivity), and proportion of absences correctly classified (specificity).Results Discrimination ability was not affected by occurrence rate, whereas the other three accuracy measures were significantly affected. CCR, sensitivity and specificity were affected by species occurrence rate in the evaluation data sets to a greater extent than in the model‐building data sets. Discrimination ability was the only accuracy measure affected by the number of variables in a model.Main conclusions Temporal variation in species occurrence appeared to have a greater impact than did spatial variation. When temporal variation in species distributions is great, the relative costs of omission and commission errors should be assessed and long‐term census data should be examined before using predictive models of occurrence in a management setting.

Ecotopic and Ontogenetic Trophic Variation in Mojarras (Pisces: Gerreidae)

Seven species of mojarras (Gerreidae) were collected from three stations in the Indian River lagoon near the Sebastian Inlet, Florida over an eighteen month period to study spatial and temporal variations in occurrence and feeding habits. Two major habitats common to this area were represented in the study; a sandy beach and a seagrass flat. Of the 2,899 gerreids collected,Eucinostomus gula represented 67% and was found primarily in theHalodule seagrass site. The next most abundant species,E. argenteus (11%),E. jonesi andE. lefroyi (each 10%), were found most frequently at the inlet site.Diapterus auratus, E. melanopterus, andGerres cinereus were captured infrequently and were considered incidental. Prey items found included amphipods, bivalves, copepods, fish eggs, foraminifera, isopods, nematodes, ostracods, polychaetes and crustacean parts. Significant amounts of sand and unidentifiable amorphous debris were also included in the gut content analysis. Little interspecific variation in diet was found among the four major species examined. The general shift seen from a diet composed primarily of copepods and other crustaceans to one of polychaetes suggests an intraspecific ontogenetic progression. Spatial variations in diet composition were also indicated between the two major habitats. Feeding analyses showed gerreids to be diurnal feeders with the greatest consumption (total gut content weight) occurring at dusk.