The effects of climatic fluctuations and extreme events on running water ecosystems

Most research on the effects of environmental change in freshwaters has focused on incremental changes in average conditions, rather than fluctuations or extreme events such as heatwaves, cold snaps, droughts, floods or wildfires, which may have even more profound consequences. Such events are commonly predicted to increase in frequency, intensity and duration with global climate change, with many systems being exposed to conditions with no recent historical precedent. We propose a mechanistic framework for predicting potential impacts of environmental fluctuations on running water ecosystems by scaling up effects of fluctuations from individuals to entire ecosystems. This framework requires integration of four key components: effects of the environment on individual metabolism, metabolic and biomechanical constraints on fluctuating species interactions, assembly dynamics of local food webs and mapping the dynamics of the meta-community onto ecosystem function. We illustrate the framework by developing a mathematical model of environmental fluctuations on dynamically assembling food webs. We highlight (currently limited) empirical evidence for emerging insights and theoretical predictions. For example, widely supported predictions about the effects of environmental fluctuations are: high vulnerability of species with high per capita metabolic demands such as large-bodied ones at the top of food webs; simplification of food web network structure and impaired energetic transfer efficiency; reduced resilience and top-down relative to bottom-up regulation of food web and ecosystem processes. We conclude by identifying key questions and challenges that need to be addressed to develop more accurate and predictive bio-assessments of the effects of fluctuations, and implications of fluctuations for management practices in an increasingly uncertain world

The effects of climatic fluctuations and extreme events on running water ecosystems

Most research on the effects of environmental change in freshwaters has focused on incremental changes in average conditions, rather than fluctuations or extreme events such as heatwaves, cold snaps, droughts, floods or wildfires, which may have even more profound consequences. Such events are commonly predicted to increase in frequency, intensity and duration with global climate change, with many systems being exposed to conditions with no recent historical precedent. We propose a mechanistic framework for predicting potential impacts of environmental fluctuations on running-water ecosystems by scaling up effects of fluctuations from individuals to entire ecosystems. This framework requires integration of four key components: effects of the environment on individual metabolism, metabolic and biomechanical constraints on fluctuating species interactions, assembly dynamics of local food webs, and mapping the dynamics of the meta-community onto ecosystem function. We illustrate the framework by developing a mathematical model of environmental fluctuations on dynamically assembling food webs. We highlight (currently limited) empirical evidence for emerging insights and theoretical predictions. For example, widely supported predictions about the effects of environmental fluctuations are: high vulnerability of species with high per capita metabolic demands such as large-bodied ones at the top of food webs; simplification of food web network structure and impaired energetic transfer efficiency; and reduced resilience and top-down relative to bottom-up regulation of food web and ecosystem processes. We conclude by identifying key questions and challenges that need to be addressed to develop more accurate and predictive bio-assessments of the effects of fluctuations, and implications of fluctuations for management practices in an increasingly uncertain world

Cheddar: analysis and visualisation of ecological communities in R

There has been a lack of software available to ecologists for the management, visualisation and analysis of ecological community and food web data. Researchers have been forced to implement their own data formats and software, often from scratch, resulting in duplicated effort and bespoke solutions that are difficult to apply to future analyses and comparative studies. We introduce Cheddar – an R package that provides standard, transparent implementations of a wide range of food web and community-level analyses and plots, focussing on ecological network data that are augmented with estimates of body mass and/or numerical abundance. The package allows analysis of individual communities, as well as collections of communities, allowing examination of changes in structure through time, across environmental gradients, or due to experimental manipulations. Several commonly analysed food web data sets are included and used in worked examples. This is the first time these important features have been combined in a single package that helps improve research efficiency and serves as a unified framework for future development

Climate change impacts in multispecies systems: drought alters food web size-structure in a field experiment

Experimental data from intergenerational field manipulations of entire food webs are scarce, yet such approaches are essential for gauging impacts of environmental change in natural systems. We imposed 2 years of intermittent drought on stream channels in a replicated field trial, to measure food web responses to simulated climate change. Drought triggered widespread losses of species and links, with larger taxa and those that were rare for their size, many of which were predatory, being especially vulnerable. Many network properties, including size–scaling relationships within food chains, changed in response to drought. Other properties, such as connectance, were unaffected. These findings highlight the need for detailed experimental data from different organizational levels, from pairwise links to the entire food web. The loss of not only large species, but also those that were rare for their size, provides a newly refined way to gauge likely impacts that may be applied more generally to other systems and/or impacts

Confirmation of traumatic cardiac arrest in children: A literature review to inform the peruki ptca consensus study

Aims Traumatic cardiac arrest (TCA) is associated with high mortality and poor neurological outcomes. Several methods of confirming cardiac arrest are utilised including auscultation of heart sounds, palpation of pulses and echocardiography. We did a literature review to identify the best method of confirming traumatic cardiac arrest in children.Methods A Medline search from 1966 to 1/11/2016 was performed using the search terms: (Cardiac AND arrest OR standstill) AND confirm* AND auscult*OR (palpat* AND pulse) OR ultrasound OR echo* AND trauma* AND pediatr* OR paediatr*. 59 papers were identified, of which 8 were deemed relevant and of sufficient quality; 2 related to palpation of pulses and 6 related to point of care ultrasound (POCUS) in adult TCA. There were no papers related to POCUS in childhood TCA, or to auscultation.Results 2 papers examined palpation of pulses on ECMO patients, concluding that diagnosis of cardiac arrest by palpation alone was unreliable, and that the most important factor in accuracy was clinical experience. Papers related to POCUS discussed its role in predicting outcomes, and reducing unnecessary procedures or duration of resuscitation efforts. One stated a positive predictive value of 100\% for death in the presence of cardiac arrest on POCUS, another stated POCUS increased confidence in decision making, while another discussed its use in a pre-hospital training course. No papers described the performance accuracy of POCUS in confirming cardiac arrest {\textendash} this may be because its advocates view it as the gold standard test in such situations.Conclusion There is little evidence to support which method of confirming paediatric cardiac arrest is optimal, and no evidence specific to cardiac arrest which occurs after energy transfer mechanisms seen in childhood trauma. Further work is needed to determine the optimal combination of methods for identifying cardiac arrest from medical and traumatic conditions, which may be best done through the creation of a robust childhood cardiac arrest registry. It is therefore important to derive consensus in this area to guide clinicians, though this must be pragmatic and may be restricted in part by the availability of emerging technologies such as POCUS