1,316 research outputs found
Differential effects of bivalves on sediment nitrogen cycling in a shallow coastal bay
In coastal ecosystems, suspension-feeding bivalves can remove nitrogen though uptake and assimilation or enhanced denitrification. Bivalves may also retain nitrogen through increased mineralization and dissimilatory nitrate reduction to ammonium (DNRA). This study investigated the effects of oyster reefs and clam aquaculture on denitrification, DNRA, and nutrient fluxes (NOx, NH4 6 +, O2). Core incubations were conducted seasonally on sediments adjacent to restored oyster reefs (Crassostrea virginica), clam aquaculture beds (Mercenaria mercenaria) which contained live clams, and bare sediments from Smith Island Bay, Virginia, USA. Denitrification was significantly higher at oyster reef sediments and clam aquaculture site than bare sediment in the summer; however DNRA was not enhanced. The clam aquaculture site had the highest ammonium production due to clam excretion. While oyster reef and bare sediments exhibited seasonal differences in rate processes, there was no effect of season on denitrification, DNRA or ammonium flux at the clam aquaculture site. This suggests that farm management practices or bivalve metabolism and excretion may override seasonal differences. When water column nitrate concentration was elevated, denitrification increased in clam aquaculture site and oyster reef sediments but not in bare sediment; DNRA was only stimulated at the clam aquaculture site. This, along with a significant and positive relationship between denitrification and sediment organic matter, suggests that labile carbon limited nitrate reduction at the bare sediment site. Bivalve systems can serve as either net sinks or sources of nitrogen to coastal ecosystems, depending mainly on the type of bivalve, location and management practices
Recommended from our members
Written evidence to the Welsh Affairs Select Committee inquiry on the impact of population change in Wales
This evidence does not seek to respond to the committees’ full agenda rather it focuses on the following aspects of the inquiry’s terms of reference.
• What will the impact of population trends be on the demand for and delivery of public services, including housing, education, and healthcare?
• What steps should the Government take to mitigate the challenges of population change in Wales?
The Committee seeks to understand the reasons for population change and its impacts. It will also examine what mitigations could be put in place by the UK Government to meet the potential challenges of population change
Microbial nitrogen processing in hard clam (Mercenaria mercenaria) aquaculture sediments: the relative importance of denitrification and dissimilatory nitrate reduction to ammonium (DNRA)
As bivalve aquaculture expands worldwide, an understanding of its role in nutrient cycling is necessary to ensure ecological sustainability and determine the potential of using bivalves for nutrient mitigation. Whereas several studies, primarily of epifaunal bivalves, have assessed denitrification, few have considered nutrient regeneration processes such as dissimilatory nitrate reduction to ammonium (DNRA), which competes with denitrification for nitrate and results in nitrogen retention rather than loss. This study compares sediment nitrogen cycling including mineralization, DNRA, and denitrification within U.S. clam aquaculture sediments to nearby uncultivated sediments, seasonally. Clam aquaculture significantly increased sediment ammonium and phosphate effluxes relative to uncultivated sediments. Both DNRA and denitrification were significantly enhanced at clam beds compared to uncultivated sediments in July and November, while in May only DNRA was increased. The ratio of DNRA to denitrification was significantly higher at clam beds compared to uncultivated sediments, demonstrating that DNRA may be favored due to a ready supply of labile organic carbon relative to nitrate and perhaps sulfidic conditions. Functional gene abundances, nrfA (DNRA) and nirS (denitrification) followed similar patterns to nitrate respiration rates with highest nrfA abundances in the clam sediments and similar nirS abundances across seasons and sediment type. Ultimately clam sediments were found to be a significant source of nutrients to the water column whereas uncultivated sediments retained ammonium produced by microbial mineralization. Thus, clam cultivation may promote local eutrophication (i.e., increased primary production) by facilitating nutrient regeneration and retention of ammonium in the sediments
Recommended from our members
Perceiving financial vulnerability: investigating Northamptonshire County Council through the lens of financial resilience
Recommended from our members
Financial resilience in English local authorities: delivering cultural and related services (CRS) during the era of austerity
Local Authorities (LAs) have been exposed to increasing financial and service demand pressures from the occurrence of disruptive events, particularly austerity. These pressures make it challenging for LAs to continue delivering services that are essential to their residents (users). In England, cultural services are essential services to residents, although English LAs struggle to consistently provide cultural and related services to their residents. This paper adopted a mixed method comprising secondary data (through data visualisation) and evidence from primary research to explore the impacts of austerity and how English LAs withstood these pressures by continuing to provide cultural and related services. The findings of this paper contribute to knowledge in the public service management literature and also provides some recommendations towards policy formulation, which is expected to enhance the financial resilience of English LAs to enable them to withstand pressures from future disruptive events
Recommended from our members
Local authority financial sustainability and the Section 114 regime
This submission provides evidence on all of the key issues outlined in the terms of reference.
There are increasing numbers of long-term and complex financial challenges besetting local government, that if not addressed, will continue to make an increasing number of authorities financially unsustainable. Under current financial reporting arrangements this will lead to the issuing of more Section 114 Notices.
The scale of the problem is significant, and the long-term unsustainability of local authority finances is fundamentally due to underlying structural issues in the collection, allocation and distribution of revenue raised to support local public service provision.
Continuing to provide short term and piecemeal financial support on the basis of the system last revised in 2013 is increasingly inefficient and sub-optimal in terms of distribution, with all parts of the current model becoming demonstrably more regressive in terms of their impact.
COVID-19 impacts and authorities’ involvement in risky commercial investments exacerbate and intensify this long-term problem and have accelerated the process, but neither are they the fundamental causes of these problems.
There is a long-term need to re-establish a new regime for local authority financing that is fair and sustainable; that reflects the levels of need for local services and the ability of individual local areas to generate revenue.
The implementation of the Redmond proposals for local audit, the adoption of CIPFA’s financial resilience index and the provisions of the Fair Funding Review will not resolve these fundamental issues on their own. A new local audit regime and a fairer distribution mechanism are both necessary, but not sufficient to generate long-term stability and a robust new regime.
A new regime will require significantly improved data and information, not least for the assessment of need, as the basis of calculating the future property tax component, and for the economic and efficient operation of the re-distributional mechanism.
An improved and updated Resilience Index; changes to the oversight of the Prudential Framework, capitalisation and reform of the Public Works Loan Board are necessary in themselves and as part of a new local government financial regime.
The submission provides detailed analysis and recommendations on each of these issues
Recommended from our members
Local authority financial reporting and external audit in England: the Redmond Review and the future of local audit
Academics and auditors have expressed growing concerns about the financial resilience and vulnerability of English local authorities after a decade of funding cuts and growing demand for public services (Barbera et al 2017; CIPFA 2017; Sandford 2020). The COVID-19 pandemic has exacerbated these problems, as local authority income has fallen, demand for services has risen and investments in assets and companies have proven less rewarding in uncertain times. (Murphy et al. 2021).
There is a widespread consensus that arrangements for public audit and formal assurance to the public and key stakeholders are no longer fit for purpose thereby increasing uncertainty amongst all key stakeholders and increasing the risk of severe financial problems within local authorities (Murphy and Lakoma 2020). In response to these growing concerns, the UK Government established an independent review of local authority audit (Redmond 2020). This has been complemented by the release of an updated Code of Audit Practice from the National Audit Office (2020), which sought to guide auditors in how to address financial sustainability. The subsequent Redmond report articulated the widespread concerns about the adequacy and transparency of local authority audit and accounts arrangements. It found new local authority activities such as new commercial and hybrid organisations fell outside of the scope of the statutory audit and it acknowledged the widening ‘expectations gap’ in what the public expect from the audit and what it is actually obliged to deliver (ICAEW 2018). In terms of the overall audit regime Redmond (2020) also found an inadequate regulatory framework, delivered by an overly complex and disparate organisational landscape having no single regulatory authority responsible for systemic leadership, oversight and co-ordination.
In December the UK Government published its response to the report’s recommendations. This paper reviews the Redmond report, the government’s formal response to its recommendations and subsequent progress with implementation in the period prior to the conference. In so doing it will be cognisant of and review its potential compliance with the INTOSAI Financial Audit Guidelines based on the International Standards on Auditing (ISA) issued by the IAASB
Phosphate Energy Metabolism During Domoic Acid-Induced Seizures
The effect of domoic acid-induced seizure activity on energy metabolism and on brain pH in mice was studied by continuous EEC recording and in vivo 31 P nuclear magnetic resonance (NMR) spectroscopy. Mice were divided into ventilated (n = 6) and nonventilated (n = 7) groups. Baseline EEG was 0.1-mV amplitude with frequence of >30-Hz and of 4–5 Hz. After intraperitoneal (i.p.) administration of domoic acid (6 mg/kg), electro graphic spikes appeared at increasing frequency, pro gressing to high-amplitude (0.1-0.8 mV) continuous sei zure activity (status epilepticus). In ventilated mice, the [ 31 P]NMR spectra showed that high-energy phosphate levels and tissue pH did not change after domoic acid administration or during the intervals of spiking or status epilepticus. Nonventilated mice showed periods of EEG suppression accompanied by decreases in the levels of high-energy phosphate metabolites and in pH, corresponding to episodic respiratory suppression during the spiking interval. In all animals, status epilepticus was fol lowed by a marked decrease in EEG amplitude that pro gressed rapidly to isoelectric silence. [ 31 P]NMR spectra obtained after this were indicative of total energy failure and tissue acidosis. In a separate group of ventilated mice (n = 4), domoic acid-induced status epilepticus was ac companied initially by an increase in mean arterial blood pressure (MAP) that slowly returned to baseline level. Isoelectric silence was accompanied by a decrease in MAP to 75 ± 8 mm Hg. These experiments suggest that domoic acid-induced seizures are not accompanied by an increase in substrate demand that exceeds supply.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65953/1/j.1528-1157.1993.tb02124.x.pd
Body odours as lures for stoats Mustela erminea: Captive and field trials
Eradication and control methods to limit damage caused to native biota in New Zealand by the stoat (Mustela erminea) rely on effective lures for trapping and detection devices, such as cameras. Long-life semiochemical lures have the potential for targeting stoats in situations where food-based lures are of limited success. The attractiveness of body odours of captive stoats was tested in a series of captive animal and extensive field trials to investigate their potential as trapping and monitoring lures. Stoats approached and spent significantly more time sniffing stoat urine and scats and bedding from oestrous female stoats than a non-treatment control. The bedding odours were attractive in both the breeding and the non-breeding season. Stoats also spent significantly more time sniffing oestrous stoat bedding than female ferret bedding, but the ferret odour also produced a significant response by stoats. In the field trials, there were no significant differences between the number of stoats caught with food lures (long-life rabbit or hen eggs) compared with oestrous female or male stoat bedding lures. These results indicate the potential of both stoat bedding odour and the scent of another mustelid species as stoat trapping lures that likely act as a general odour attractant rather than a specific chemical signal of oestrus
- …