2,496 research outputs found
Assessing methods to improve benthic fish sampling in a stony headwater stream
Electrofishing is a well-established and widely used method for surveying fish populations. Nonetheless, its effectiveness is impacted by numerous factors, including water chemistry, habitat type and fish species. Both physiological and behavioural responses make bottom-dwelling âbenthicâ fish which lack swim bladders (e.g. European bullhead Cottus gobio) particularly difficult to survey by electrofishing.
We compare the performance and practicalities of electrofishing for benthic fish at a rocky northern English headwater stream with two sampling methods originally designed for crayfish surveys; the triple drawdown method which involves repeated dewatering of a site, and the Pritchard Trap method which involves sunken traps filled with natural substrate that samples a small, fixed (0.25 m2) area of river bed.
Both the Pritchard trapping and triple drawdown methods provided similar high-density population density estimates for bullhead which were at least 2.5â5 times higher than predicted from electrofishing derived sweep depletion curves.
Electrofishing and the triple drawdown method are both resource-intensive, requiring expensive equipment and a team of trained operatives. These approaches also pose a risk to fish and non-target organisms. In contrast, Pritchard Traps provide a cost-effective passive, low risk survey method requiring minimal training and only one operative. Pritchard traps, therefore, show particular promise for benthic fish surveying and monitoring
Historical Analysis Exposes Catastrophic Seagrass Loss for the United Kingdom
The spatial extent of seagrass is poorly mapped, and knowledge of historical loss is limited. Here, we collated empirical and qualitative data using systematic review methods to provide unique analysis on seagrass occurrence and loss in the United Kingdom. We document 8,493 ha of recently mapped seagrass in the United Kingdom since 1998. This equates to an estimated 0.9 Mt of carbon, which, in the current carbon market represents about ÂŁ22 million. Using simple models to estimate seagrass declines triangulated against habitat suitability models, we provide evidence of catastrophic seagrass loss; at least 44% of United Kingdomâs seagrasses have been lost since 1936, 39% since the 1980âs. However, losses over longer time spans may be as high as 92%. Based on these estimates, historical seagrass meadows could have stored 11.5 Mt of carbon and supported approximately 400 million fish. Our results demonstrate the vast scale of losses and highlight the opportunities to restore seagrass to support a range of ecosystems services
Strategies to reduce nutrient pollution from manure management in China
As the demand for livestock products continues to increase in China, so too does the challenge of managing increasing quantities of manure. Urgent action is needed to control point source (housing, storage and processing) and diffuse (field application) pollution and improve the utilization of manure nutrients and organic matter. Here, we review strategies to improve management at each stage of the manure management chain and at different scales. Many strategies require infrastructure investment, e.g., for containment of all manure fractions. Engineering solutions are needed to develop advanced composting systems with lower environmental footprints and design more efficient nutrient stripping technologies. At the field-scale, there is an urgent need to develop a manure nutrient recommendation system that accounts for the range of manure types, cropping systems, soils and climates throughout China. At the regional scale, coordinated planning is necessary to promote recoupling of livestock and cropping systems, and reduce nutrient accumulation in regions with little available landbank, while minimizing the risk of pollution swapping from one region to another. A range of stakeholders are needed to support the step change and innovation required to improve manure management, reduce reliance on inorganic fertilizers, and generate new business opportunities
Avoiding Chaos in Wonderland
Wonderland, a compact, integrated economic, demographic and environmental
model is investigated using methods developed for studying critical phenomena.
Simulation results show the parameter space separates into two phases, one of
which contains the property of long term, sustainable development. By employing
information contain in the phase diagram, an optimal strategy involving
pollution taxes is developed as a means of moving a system initially in a
unsustainable region of the phase diagram into a region of sustainability while
ensuring minimal regret with respect to long term economic growth.Comment: 22 pages, 9 figures. Submitted to Physica
Fluvial biotopes influence macroinvertebrate biodiversity in South-East Asian tropical streams
This is the final version. Available from Ecological Society of America via the DOI in this record.Given the widespread degradation of aquatic systems caused by landâuse changes associated with palm oil production in SouthâEast Asia, it is imperative to identify and study the remaining undisturbed rivers and streams. Stream macroinvertebrates are reliable indicators of environmental health. Linking the community structure of these organisms to natural hydraulic and geomorphic conditions (categorized as biotopes) is vital for the conservation and restoration of streams. This study characterizes the effects of biotopes on macroinvertebrate community structure in three streams within Ulu Temburong National Park in northern Borneo. Biotopes within these streams were categorized as either bedrock (waterfalls and cascades) or mixed substrate (riffles and pools). In total, 119 taxa were collected from all sampled biotopes, but not all taxa were collected from each stream. Biotopes were statistically distinct in terms of taxonomic richness, but not mean individual density or average community biomass. There were differences in community structure between waterfalls, cascades, pools, and riffles. The survey suggests that pool and riffle biotopes were more vulnerable to scouring flows and had similar community structure, while waterfalls and cascades likely experienced lower sheer stress during floods and had similar macroinvertebrate communities. This study has found that classification and mapping of macroinvertebrates with biotope theory in pristine, tropical streams is a useful framework for simplifying the many linkages between ecology, geomorphology, and hydrology. These natural patterns increase our understanding of tropical streams and can be used to assess the impacts of forest degradation.Natural Environment Research Councilâfunded PhD Studentshi
Nitrogen, Phosphorus, and Potassium Flows through the Manure Management Chain in China
The largest livestock production
and greatest fertilizer use in
the world occurs in China. However, quantification of the nutrient
flows through the manure management chain and their interactions with
management-related measures is lacking. Herein, we present a detailed
analysis of the nutrient flows and losses in the âfeed intakeâexcretionâhousingâstorageâtreatmentâapplicationâ
manure chain, while considering differences among livestock production
systems. We estimated the environmental loss from the manure chain
in 2010 to be up to 78% of the excreted nitrogen and over 50% of the
excreted phosphorus and potassium. The greatest losses occurred from
housing and storage stages through NH<sub>3</sub> emissions (39% of
total nitrogen losses) and direct discharge of manure into water bodies
or landfill (30â73% of total nutrient losses). There are large
differences among animal production systems, where the landless system
has the lowest manure recycling. Scenario analyses for the year 2020
suggest that significant reductions of fertilizer use (27â100%)
and nutrient losses (27â56%) can be achieved through a combination
of prohibiting manure discharge, improving manure collection and storages
infrastructures, and improving manure application to cropland. We
recommend that current policies and subsidies targeted at the fertilizer
industry should shift to reduce the costs of manure storage, transport,
and application
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