Boundaries and Corridors as a Continuum of Ecological Flow Control: Lessons from Rivers and Streams

Abstract: Landscape boundaries and corridors are areas of small spatial extent relative to their large effects on ecological flows. The trend in ecological literature is to treat corridors and boundaries as separate phenomena on the landscape. This approach, however, misses a fundamental aspect they have in common: their strong influence on ecological flows. Corridors and boundaries exist at opposite ends of a permeability gradient, differing in their effects on rates and direction of flow. The position of landscape structures along this permeability gradient depends on attributes of both the flow and of the structure itself. We discuss boundaries and corridors in terms of mover specificity, scale, and effects on different levels of ecological organization, using rivers and streams to illustrate our points. We predict which structures will act as boundaries or corridors and at what spatial and temporal scales they are likely to be relevant. Considering the function of landscape structures across the boundary-corridor continuum will provide researchers and managers with a more complete, holistic viewpoint and will allow better strategies to attain conservation goals.     

Processing of poultry feathers by alkaline keratin hydrolyzing enzyme from Serratia sp. HPC 1383

The present study describes the production and characterization of a feather hydrolyzing enzyme by Serratia sp. HPC 1383 isolated from tannery sludge, which was identified by the ability to form clear zones around colonies on milk agar plates. The proteolytic activity was expressed in terms of the micromoles of tyrosine released from substrate casein per ml per min (U/mL min). Induction of the inoculum with protein was essential to stimulate higher activity of the enzyme, with 0.03% feathermeal in the inoculum resulting in increased enzyme activity (45 U/mL) that further increased to 90 U/mL when 3 d old inoculum was used. The highest enzyme activity, 130 U/mL, was observed in the presence of 0.2% yeast extract. The optimum assay temperature and pH for the enzyme were found to be 60 °C and 10.0, respectively. The enzyme had a half-life of 10 min at 60 °C, which improved slightly to 18 min in presence of 1 mM Ca²⁺. Inhibition of the enzyme by phenylmethyl sulfonyl fluoride (PMSF) indicated that the enzyme was a serine protease. The enzyme was also partially inhibited (39%) by the reducing agent β-mercaptoethanol and by divalent metal ions such as Zn²⁺ (41% inhibition). However, Ca²⁺ and Fe²⁺ resulted in increases in enzyme activity of 15% and 26%, respectively. The kinetic constants of the keratinase were found to be 3.84 μM (K_m) and 108.7 μM/mL min (V_max). These results suggest that this extracellular keratinase may be a useful alternative and eco-friendly route for handling the abundant amount of waste feathers or for applications in other industrial processes.     

19th century London dust-yards: A case study in closed-loop resource efficiency

The material recovery methods used by dust-yards in early 19th century London, England and the conditions that led to their development, success and decline are reported. The overall system developed in response to the market value of constituents of municipal waste, and particularly the high coal ash content of household ‘dust’. The emergence of lucrative markets for ‘soil’ and ‘breeze’ products encouraged dust-contractors to recover effectively 100% of the residual wastes remaining after readily saleable items and materials had been removed by the thriving informal sector. Contracting dust collection to the private sector allowed parishes to keep the streets relatively clean, without the need to develop institutional capacity, and for a period this also generated useful income. The dust-yard system is, therefore, an early example of organised, municipal-wide solid waste management, and also of public–private sector participation. The dust-yard system had been working successfully for more than 50 years before the Public Health Acts of 1848 and 1875, and was thus important in facilitating a relatively smooth transition to an institutionalised, municipally-run solid waste management system in England. The dust-yards can be seen as early precursors of modern materials recycling facilities (MRFs) and mechanical–biological treatment (MBT) plants; however, it must be emphasised that dust-yards operated without any of the environmental and occupational health considerations that are indispensable today. In addition, there are analogies between dust-yards and informal sector recycling systems currently operating in many developing countries.     

Utilization of molasses spentwash for production of bioplastics by waste activated sludge

Present study describes the treatment of molasses spentwash and its use as a potential low cost substrate for production of biopolymer polyhydroxybutyrate (PHB) by waste activated sludge. Fluorescence microscopy revealed the presence of PHB granules in sludge biomass which was further confirmed by fourier transform-infra-red spectroscopy (FT-IR) and ¹³C nuclear magnetic resonance (NMR). The processing of molasses spentwash was carried out for attaining different ratios of carbon and nitrogen (C:N). Highest chemical oxygen demand (COD) removal and PHB accumulation of 60% and 31% respectively was achieved with raw molasses spentwash containing inorganic nitrogen (C:N ratio = 28) followed by COD removal of 52% and PHB accumulation of 28% for filtered molasses containing inorganic nitrogen (C:N ratio = 29). PHB production yield (Y_p/s) was highest (0.184 g g^?1 COD consumed) for deproteinized spentwash supplemented with nitrogen. In contrast, the substrate consumption and product formation were higher in case of raw spentwash. Though COD removal was lowest from deproteinized spentwash, evaluation of kinetic parameters suggested higher rates of conversion of available carbon to biomass and PHB. Thus the process provided dual benefit of conversion of two wastes viz. waste activated sludge and molasses spentwash into value-added product-PHB.     

The response of sea scallop (Placopecten magellanicus) veligers to a weak thermocline in 9-m deep mesocosms

We examined the vertical distributions of scallop (Placopecten magellanicus) veligers in deep (0.6 m diameter, 9.5 m deep) polyethylene mesocosms from December 1991 to January 1992. In the mesocosms temperature stratification varied from 0 to 1.5 °C. Profiles of vertical distribution revealed several repeated patterns. Peaks in veliger numbers often appeared at the water surface and just above the thermocline. Higher density patches were seen below the surface peaks, and revealed the presence of bio-convective cells. Distribution away from these discontinuities was usually even. Distribution of veligers was affected by thermoclines above 1.0 °C. Responses to thermoclines varied with larval age and time of day, and 28 to 30 d veligers passed in both directions through a 1.5 °C thermocline. We conclude that larval behaviour is a major determinant of whether veligers pass through a thermocline. Kinematic viscosity may play a role in perception of temperature changes. Two potential consequences of such behaviour are (1) remaining in more productive upper water layers, where feeding opportunities are enhanced, and (2) increased horizontal transport in the region of the thermocline, which may enhance recruitment. Received: 15 May 1996 / Accepted: 11 May 2000     

Does risk of intraspecific interactions induce shifts in prey-size preference in aquatic predators?

Interactions between foragers may seriously affect individual foraging efficiency. In a laboratory study of handling time, prey value and prey-size preference in northern pike and signal crayfish, we show that risk of intraspecific interactions between predators does not affect handling time or value of prey. However, the presence of agonistic intraspecific interactors shifts prey-size preference in these predators. Neither northern pike nor signal crayfish foraging alone show a prey-size preference, while pike foraging among conspecifics prefer small prey, and crayfish foraging in groups prefer large prey. We ascribe the different outcomes in prey preference to differences in susceptibility to interactions: northern pike under risk avoid large prey to avoid long handling times and the associated risk of interactions, while signal crayfish foraging among conspecifics may defend themselves and their prey during handling, and thus select prey to maximise investment. In addition, the value of pike prey (roach) is low for very small prey, maximises for small prey, and then decreases monotonically for larger prey, while crayfish prey (pond snail) value is low for very small prey, has a maximum at small prey, but does not decrease as much for larger prey. Therefore, a large and easily detected snail prey provides a crayfish with as much value as a small prey. We conclude that interaction risk and predator density affect prey-size preference differently in these aquatic predators, and therefore has different potential effects on prey-size structure and population and community dynamics. Received: 4 October 1999 / Revised: 20 March 2000 / Accepted: 27 May 2000