scholarly journals Effects of multiple stressors on river biofilms depend on the time scale

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ferran Romero ◽  
Vicenç Acuña ◽  
Carme Font ◽  
Anna Freixa ◽  
Sergi Sabater
Keyword(s):  
Exposure Time ◽  
Pesticide Exposure ◽  
Multiple Stressors ◽  
Freshwater Ecosystems ◽  
Additive Effects ◽  
Short Term ◽  
Multiple Stressor ◽  
Hydrological Stress ◽  
Additive Interactions

Abstract Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surface of stressed area) and temporal (i.e. exposure time) components. Among freshwater ecosystems, rivers and streams are subject to physical, chemical and biological stressors, which interact with each other and might produce diverging effects depending on exposure time. We conducted a manipulative experiment using 24 artificial streams to examine the individual and combined effects of warming (1.6 °C increase in water temperature), hydrological stress (simulated low-flow situation) and chemical stress caused by pesticide exposure (15.1–156.7 ng L−1) on river biofilms. We examined whether co-occurring stressors could lead to non-additive effects, and if these differed at two different exposure times. Specifically, structural and functional biofilm responses were assessed after 48 hours (short-term effects) and after 30 days (long-term effects) of exposure. Hydrological stress caused strong negative impacts on river biofilms, whereas effects of warming and pesticide exposure were less intense, although increasing on the long term. Most stressor combinations (71%) resulted in non-significant interactions, suggesting overall additive effects, but some non-additive interactions also occurred. Among non-additive interactions, 59% were classified as antagonisms after short-term exposure to the different stressor combinations, rising to 86% at long term. Our results indicate that a 30-day exposure period to multiple stressors increases the frequency of antagonistic interactions compared to a 48-hour exposure to the same conditions. Overall, the impacts of multiple-stressor occurrences appear to be hardly predictable from individual effects, highlighting the need to consider temporal components such as duration when predicting the effects of multiple stressors.

scholarly journals Multiple Stressors Determine Community Structure and Estimated Function of River Biofilm Bacteria

2020 ◽  
Vol 86 (12) ◽  
Author(s):  
Ferran Romero ◽  
Vicenç Acuña ◽  
Sergi Sabater
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Bacterial Communities ◽  
Pesticide Exposure ◽  
Multiple Stressors ◽  
Bacterial Community Composition ◽  
Freshwater Ecosystems ◽  
Low Flow ◽  
Hydrological Stress ◽  
The Individual

ABSTRACT Freshwater ecosystems are exposed to multiple stressors, but their individual and combined effects remain largely unexplored. Here, we investigated the response of stream biofilm bacterial communities to warming, hydrological stress, and pesticide exposure. We used 24 artificial streams on which epilithic (growing on coarse sediments) and epipsammic (growing on fine sediments) stream biofilms were maintained. Bacterial community composition and estimated function of biofilms exposed during 30 days to individual and combined stressors were assessed using 16S rRNA gene metabarcoding. Among the individual effects by stressors, hydrological stress (i.e., a simulated low-flow situation) was the most relevant, since it significantly altered 57% of the most abundant bacterial taxa (n = 28), followed by warming (21%) and pesticide exposure (11%). Regarding the combined effects, 16% of all stressor combinations resulted in significant interactions on bacterial community composition and estimated function. Antagonistic responses prevailed (57 to 89% of all significant interactions), followed by synergisms (11 to 43%), on specific bacterial taxa, indicating that multiple-stressor scenarios could lead to unexpected shifts in the community composition and associated functions of riverine bacterial communities. IMPORTANCE Freshwater ecosystems such as rivers are of crucial importance for human well-being. However, human activities result in many stressors (e.g., toxic chemicals, increased water temperatures, and hydrological alterations) cooccurring in rivers and streams worldwide. Among the many organisms inhabiting rivers and streams, bacteria are ecologically crucial; they are placed at the base of virtually all food webs and they recycle the organic matter needed for bigger organisms. Most of these bacteria are in close contact with river substratum, where they form the biofilms. There is an urgent need to evaluate the effects of these stressors on river biofilms, so we can anticipate future environmental problems. In this study, we experimentally exposed river biofilms to a pesticide mixture, an increase in water temperature and a simulated low-flow condition, in order to evaluate the individual and joint effects of these stressors on the bacterial community composition and estimated function.

scholarly journals Novel energy-saving strategies to multiple stressors in birds: the ultradian regulation of body temperature

2016 ◽  
Vol 283 (1839) ◽  
pp. 20161551 ◽  
Author(s):  
Glenn J. Tattersall ◽  
Damien Roussel ◽  
Yann Voituron ◽  
Loïc Teulier
Keyword(s):  
Body Temperature ◽  
Multiple Stressors ◽  
Energetic Cost ◽  
Short Term ◽  
Ad Libitum ◽  
Key Sites ◽  
Ad Libitum Feeding ◽  
Reduced Surface ◽  
Internal Body

This study aimed to examine thermoregulatory responses in birds facing two commonly experienced stressors, cold and fasting. Logging devices allowing long-term and precise access to internal body temperature were placed within the gizzards of ducklings acclimated to cold (CA) (5°C) or thermoneutrality (TN) (25°C). The animals were then examined under three equal 4-day periods: ad libitum feeding, fasting and re-feeding. Through the analysis of daily as well as short-term, or ultradian, variations of body temperature, we showed that while ducklings at TN show only a modest decline in daily thermoregulatory parameters when fasted, they exhibit reduced surface temperatures from key sites of vascular heat exchange during fasting. The CA birds, on the other hand, significantly reduced their short-term variations of body temperature while increasing long-term variability when fasting. This phenomenon would allow the CA birds to reduce the energetic cost of body temperature maintenance under fasting. By analysing ultradian regulation of body temperature, we describe a means by which an endotherm appears to lower thermoregulatory costs in response to the combined stressors of cold and fasting.

scholarly journals The Effect of Perfluorooctane Sulfonate, Exposure Time, and Chemical Mixtures on Methanogenic Community Structure and Function

2015 ◽  
Vol 8s2 ◽  
pp. MBI.S31345 ◽  
Author(s):  
Patrick J. McNamara ◽  
Timothy M. LaPara ◽  
Paige J. Novak
Keyword(s):  
Community Structure ◽  
Exposure Time ◽  
Methane Production ◽  
Perfluorooctane Sulfonate ◽  
Structure And Function ◽  
Short Term ◽  
Anaerobic Digesters ◽  
And Function ◽  
The Impact

A plethora of organic micropollutant mixtures are found in untreated municipal wastewater. Anaerobic digesters receive large loadings of hydrophobic micropollutants that sorb to wastewater biosolids. Despite micropollutants being pervasive as mixtures, little research is available to explain the impact that mixtures of compounds, as well as exposure time, have on microbial communities in anaerobic digesters. Perfluorooctane sulfonate (PFOS) was added to anaerobic enrichment cultures in both short-term (14 days) and long-term (140 days) studies to determine the impact of exposure time. Additionally, triclosan was added during the experiments to investigate the impact of mixtures on community structure and function. PFOS did not alter methane production in short-term studies, but in long-term studies, methane production increased, consistent with our hypothesis that PFOS may act as a metabolic uncoupler. The impact of triclosan on methane production was exacerbated when PFOS was already present in the anaerobic enrichment cultures. Triclosan also had greater impacts on microbial community structures in the bottles that had been exposed to PFOS long-term. These results demonstrate that both chemical mixtures and exposure time are important parameters to address when trying to define the impacts of micropollutants on anaerobic microbial communities.

scholarly journals Perceptions on climate change and its impact on livelihoods in Hwange district, Zimbabwe

2014 ◽  
Vol 6 (1) ◽  
Author(s):  
Charles Nhemachena ◽  
Reneth Mano ◽  
Shakespear Mudombi ◽  
Virginia Muwanigwa
Keyword(s):  
Climate Change ◽  
Rural Communities ◽  
Rural Community ◽  
Multiple Stressors ◽  
Climatic Factors ◽  
Climate Change Impacts ◽  
Short Term ◽  
Local Livelihood ◽  
Impacts Of Climate Change

This study investigated perceptions of rural communities on climate change and its impacts on livelihoods. The research was conducted in the semi-arid Hwange district in Matebelel and North province of Zimbabwe. The perceptions were compared with empirical evidence from climatic studies on trends on temperature and rainfall, and impacts on livelihoods in the country and region. The findings from the current study are generally in agreement with those of other studies that indicate changes in the climate, especially in terms of rainfall. This largely applies to short-term periods; however, for long-term periods it is difficult to accurately relate rural community perceptions to changes in rainfall over time. Despite perceived changes and impacts of climate change on local livelihood activities, mainly agriculture, there are multiple stressors that the communities face which also affect their livelihoods. Further evidence-based research is required to disentangle climate change impacts on livelihoods, including livelihood impacts arising from interactions of climate and non-climatic factors.

scholarly journals The role of paleolimnology in climate and environment reconstruction and lake restoration in light of research on selected bioindicators

2020 ◽  
Vol 10 (1) ◽  
pp. 16-28
Author(s):  
Marta Wojewódka ◽  
Dario Hruševar
Keyword(s):  
Lake Restoration ◽  
Pollen Grains ◽  
Freshwater Ecosystems ◽  
Short Term ◽  
Environment Changes ◽  
Abiotic Variables ◽  
Modern Population ◽  
Restoration Measures

Paleolimnologists and ecologists study biotic and abiotic variables to track long-term and short-term environment changes. Microscopic invertebrates, phytoplankton of freshwater ecosystems, and pollen grains have been extensively studied during the last decades. Surveys of modern and fossil biota composition might provide information about past changes caused by climate alteration and human activity. Furthermore, research on the modern population of these biological proxies may be utilized to assess environmental quality and restoration measures. This paper synthesizes knowledge of the use of selected microscopic invertebrates (Cladocera, Copepoda, Ostracoda, Rotifera), phytoplankton, and pollen grains for the aforementioned issues. This review shows that the ability of these biological proxies to indicate environment changes is versatile. Some of them may be utilized to track long-term changes of temperature (pollen) or pH (Diatomeae). Others are useful to reconstruct paleosalinity (Ostracoda) or conductivity (Ostracoda, Diatomeae), while the utilization of Rotifera and Copepoda in paleoreconstruction, due to the very poor preservation of the remains, is very limited, although these fauna are very useful for assessing modern water quality. Larger species of Cladocera are significant for lake restoration

scholarly journals Current insecticide treatments used in locust control have less of a short-term impact on Australian arid-zone reptile communities than does temporal variation

2015 ◽  
Vol 42 (1) ◽  
pp. 50 ◽  
Author(s):  
Kimberly Maute ◽  
Kristine French ◽  
C. Michael Bull ◽  
Paul Story ◽  
Grant Hose
Keyword(s):  
Community Composition ◽  
Pesticide Exposure ◽  
Arid Zone ◽  
Large Field ◽  
Annual Rainfall ◽  
Potential Hazard ◽  
Pitfall Trapping ◽  
Short Term ◽  
Locust Control

Context Despite the regular use of pesticides to control locusts, there is a lack of information on the effects of locust-control treatments on reptiles worldwide. Exposure to pesticides poses a significant potential hazard to small reptiles, both from the direct effects of exposure, and indirectly because of their largely insectivorous diet and small home ranges. Aims Our study aimed to monitor the effects of two insecticides applied operationally for locust control in Australia. A phenyl pyrazole pesticide, fipronil, and a fungal biopesticide, Metarhizium acridium (Green Guard®), were applied aerially in either a barrier or block treatment in the absence of dense locust populations, and effects on non-target arid-zone reptiles were measured. Methods We monitored reptile-abundance and community-composition responses to treatments using a large field-based pitfall-trapping experiment, with replicated control and spraying treatments, which approximated the scale of aerial-based locust-control operations in Australia. Key results Neither reptile abundance nor community composition was significantly affected by locust-control treatments. However, both abundance and community composition as detected by pitfall trapping changed over time, in both control and treatment plots, possibly as a result of a decrease in annual rainfall. Conclusions The absence of any significant short-term pesticide treatment effects in our study suggests that the two locust-control application methods studied present a relatively insignificant hazard to reptiles at our site, based on a single application. Similar to other areas of Australia, climate and other factors are likely to be stronger drivers of reptile abundance and community structure. Implications Monitoring over an area that approximates the scale of the current locust-control operations is an important step in understanding the possible effects of current pesticide exposure on reptile populations and will inform insecticide risk assessments in Australia. However, important information on the immediate response of individuals to insecticide application and long-term effects of exposure are missing. The preliminary research reported in the present paper should be complemented by future investigations on long-term and sublethal impacts of pesticide exposure on Australian native reptiles and the possible benefits provided to reptiles by the resource pulses represented in untreated high-density locust populations.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Comparison of Auditory, Language, Memory, and Attention Abilities in Children With and Without Listening Difficulties

2020 ◽  
Vol 29 (4) ◽  
pp. 710-727
Author(s):  
Beula M. Magimairaj ◽  
Naveen K. Nagaraj ◽  
Alexander V. Sergeev ◽  
Natalie J. Benafield
Keyword(s):  
Auditory Processing ◽  
Short Term Memory ◽  
Group Differences ◽  
Long Term Memory ◽  
Short Term ◽  
Significant Group ◽  
Term Memory ◽  
Memory And Attention ◽  
Speed And Accuracy

Objectives School-age children with and without parent-reported listening difficulties (LiD) were compared on auditory processing, language, memory, and attention abilities. The objective was to extend what is known so far in the literature about children with LiD by using multiple measures and selective novel measures across the above areas. Design Twenty-six children who were reported by their parents as having LiD and 26 age-matched typically developing children completed clinical tests of auditory processing and multiple measures of language, attention, and memory. All children had normal-range pure-tone hearing thresholds bilaterally. Group differences were examined. Results In addition to significantly poorer speech-perception-in-noise scores, children with LiD had reduced speed and accuracy of word retrieval from long-term memory, poorer short-term memory, sentence recall, and inferencing ability. Statistically significant group differences were of moderate effect size; however, standard test scores of children with LiD were not clinically poor. No statistically significant group differences were observed in attention, working memory capacity, vocabulary, and nonverbal IQ. Conclusions Mild signal-to-noise ratio loss, as reflected by the group mean of children with LiD, supported the children's functional listening problems. In addition, children's relative weakness in select areas of language performance, short-term memory, and long-term memory lexical retrieval speed and accuracy added to previous research on evidence-based areas that need to be evaluated in children with LiD who almost always have heterogenous profiles. Importantly, the functional difficulties faced by children with LiD in relation to their test results indicated, to some extent, that commonly used assessments may not be adequately capturing the children's listening challenges. Supplemental Material https://doi.org/10.23641/asha.12808607

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