Assessment of physico-chemical properties and metal contents of water and sediments of Bodo Creek,Niger Delta,Nigeria

Some physico-chemical properties and the concentrations of the metals Fe, Mn, Ni, Cd, Cr, Co, Cu, Pb, and Zn in water and sediments were examined from September 2011 to January 2012 in Bodo Creek, where oil spills have been recurrent. Temperature, pH, total dissolved solid, conductivity, salinity, dissolved oxygen, biological oxygen demand (BOD), chemical oxygen demand (COD), total hardness, sulfate, nitrate, and phosphate were determined in surface water. Particle size, total organic matter (TOM), and pH were also determined in the sediments. The parameters were within permissible limits except the mean values of BOD, COD, total hardness, and sulfate that exceeded levels permissible for domestic use. The sediments consisted mainly of sand, with TOM ranging from 0.2% to 5.5%. With the exception of cadmium that was below detection limit, metal levels (mg kg^?1) in the sediments were 12 (Mn), 1070 (Fe), 10 (Cu), 10 (Zn), 5.3 (Cr), 1.1 (Pb), 1.0 (Ni), and 0.5 (Co) while in water they were 24, 98, 21, 6.9, 4.0, 0.6, 0.18, and 0.16, respectively. The latter were higher than World Health Organization recommended permissible levels for both surface and drinking water.     

Evaluating Geomorphic Change in Constructed Two‐Stage Ditches

Straight, trapezoidal‐shaped surface drainage channels efficiently drain the soil profile, but their deviations from natural fluvial conditions drive the need for frequent maintenance. Ecological and socioeconomic impacts of drainage ditch maintenance activities can be significant, leading to harmful algal blooms and increased sedimentation. We developed a two‐stage ditch design that is more consistent with fluvial form and process. The approach has potential to enhance ecological services while meeting drainage needs essential for agricultural production. We studied geomorphic change of the inset channel, benches and banks of seven two‐stage ditches in Ohio, Indiana, and Michigan. Three to 10 years after construction, inset channel changes reflected natural adjustments, but not all ditches had reached their quasi‐equilibrium state. Ditches had experienced both degradation and aggradation on the benches at a rate of 0.5‐13 mm/yr. Aggradation on the benches was not likely to threaten tile drain outlets. Localized scour was observed on the banks at some sites, but at all but one site changes were not statistically significant. Except for the removal of woody vegetation, none of the ditches required routine maintenance since construction. Two‐stage ditches can be a stable, viable option for drainage ditch management if designed and installed properly on the landscape.     

Policy design,spatial planning and climate change adaptation: a case study from Australia

There are gaps in the existing climate change adaptation literature concerning the design of spatial planning instruments and the relationship between policy instruments and the sociopolitical barriers to adaptation reform. To help address this gap, this article presents a typology of spatial planning instruments for adaptation and analyses the pattern of instrument choice in Australian planning processes in order to shed light on contextual factors that can impede adaptation. The analysis highlights how policy design can amplify the barriers to adaptation by arranging policy actors in ways inimical to reform and stripping decision makers of the instruments necessary to make and sustain desired policy changes.     

Cyclone disaster vulnerability and response experiences in coastal Bangladesh

For generations, cyclones and tidal surges have frequently devastated lives and property in coastal and island Bangladesh. This study explores vulnerability to cyclone hazards using first‐hand coping recollections from prior to, during and after these events. Qualitative field data suggest that, beyond extreme cyclone forces, localised vulnerability is defined in terms of response processes, infrastructure, socially uneven exposure, settlement development patterns, and livelihoods. Prior to cyclones, religious activities increase and people try to save food and valuable possessions. Those in dispersed settlements who fail to reach cyclone shelters take refuge in thatched‐roof houses and big‐branch trees. However, women and children are affected more despite the modification of traditional hierarchies during cyclone periods. Instinctive survival strategies and intra‐community cooperation improve coping post cyclone. This study recommends that disaster reduction programmes encourage cyclone mitigation while being aware of localised realities, endogenous risk analyses, and coping and adaptation of affected communities (as active survivors rather than helpless victims).     

Targeting Ecosystem Features for Conservation: Standing Crops in the Florida Everglades

Abstract: The Everglades in southern Florida, U.S.A., is a major focus of conservation activities. The freshwater wetlands of the Everglades do not have high species richness, and no species of threatened aquatic animals or plants live there. We have, however, identified a distinctive ecological feature of the Everglades that is threatened by canal construction, draining, and nutrient enrichment from agricultural runoff. Compared to values reported from other freshwater systems, standing stocks of periphyton in relatively undisturbed areas of the Everglades were unusually high, and standing stocks of invertebrates and fish were unusually low. Averaging data gathered from nine sites and five sampling periods spanning 1 year, we found that periphyton standing crop was 88.2 g/m² (ash-free dry mass), invertebrate standing stock was 0.64 g/m² (dry mass), and fish standing stock was 1.2 g/m² (dry mass of large and small species combined). We found that fish standing stocks were much higher in phosphorus-enriched sites than in nearby reference sites but that invertebrate standing stocks were similar in enriched and reference sites. Our results support the notion that oligotrophy is at least partially responsible for the low standing stocks of fish, but they also suggest that species interactions and a paucity of deep-water refugia are important. Anthropogenic eutrophication in Everglades marshes will lead to the loss of distinctive ecosystem features. A focus on species richness and "hot spots" of threatened species provides no basis for conservation of ecosystems like the Everglades. If oligotrophic ecosystems often have low species richness, they will be underrepresented in preservation networks based on some common criteria for establishing conservation priorities.     

Prairie strips reduce fecal indicator bacteria concentrations in simulated runoff

Vegetative filter strips (VFS) have shown promising results in reducing the downstream transport of many agroecosystem contaminants. A recently developed type of VFS, prairie strips, has been shown to significantly reduce the impact of corn and soybean production systems on water quality in terms of sediment, nitrogen, and phosphorus losses. This study assessed potential additional benefits of prairie strips to include the reduction of pathogens. To assess the impact of prairie strips on manure-laden agricultural runoff, we utilized a physical model of prairie strips in a laboratory flume to conduct highly controlled overland flow experiments. Escherichia coli and Enterococcus concentration reductions of up to 45% and 65% were observed for runoff and infiltration flows, respectively, while mass load reductions of up to 65% were observed for surficial runoff flows. The degree of concentration or mass load reductions was dependent on the residence time of the flow within the strip and the partitioning of overland flow running onto the strip to infiltration and runoff flows. Based on our results and a review of the literature, we developed a design method to provide guidance on the width of prairie strip buffer needed to achieve a user-defined reduction of fecal bacteria concentration.     

Fine-scale habitat modeling of a top marine predator: do prey data improve predictive capacity?

Predators and prey assort themselves relative to each other, the availability of resources and refuges, and the temporal and spatial scale of their interaction. Predictive models of predator distributions often rely on these relationships by incorporating data on environmental variability and prey availability to determine predator habitat selection patterns. This approach to predictive modeling holds true in marine systems where observations of predators are logistically difficult, emphasizing the need for accurate models. In this paper, we ask whether including prey distribution data in fine-scale predictive models of bottlenose dolphin (Tursiops truncatus) habitat selection in Florida Bay, Florida, U.S.A., improves predictive capacity. Environmental characteristics are often used as predictor variables in habitat models of top marine predators with the assumption that they act as proxies of prey distribution. We examine the validity of this assumption by comparing the response of dolphin distribution and fish catch rates to the same environmental variables. Next, the predictive capacities of four models, with and without prey distribution data, are tested to determine whether dolphin habitat selection can be predicted without recourse to describing the distribution of their prey. The final analysis determines the accuracy of predictive maps of dolphin distribution produced by modeling areas of high fish catch based on significant environmental characteristics. We use spatial analysis and independent data sets to train and test the models. Our results indicate that, due to high habitat heterogeneity and the spatial variability of prey patches, fine-scale models of dolphin habitat selection in coastal habitats will be more successful if environmental variables are used as predictor variables of predator distributions rather than relying on prey data as explanatory variables. However, predictive modeling of prey distribution as the response variable based on environmental variability did produce high predictive performance of dolphin habitat selection, particularly foraging habitat.     

The effects of habitat loss, fragmentation, and community homogenization on resilience in estuaries.

When changes in the frequency and extent of disturbance outstrip the recovery potential of resident communities, the selective removal of species contributes to habitat loss and fragmentation across landscapes. The degree to which habitat change is likely to influence community resilience will depend on metacommunity structure and connectivity. Thus ecological connectivity is central to understanding the potential for cumulative effects to impact upon diversity. The importance of these issues to coastal marine communities, where the prevailing concept of open communities composed of highly dispersive species is being challenged, indicates that these systems may be more sensitive to cumulative impacts than previously thought. We conducted a disturbance-recovery experiment across gradients of community type and environmental conditions to assess the roles of ecological connectivity and regional variations in community structure on the recovery of species richness, total abundance, and community composition in Mahurangi Harbour, New Zealand. After 394 days, significant differences in recovery between sites were apparent. Statistical models explaining a high proportion of the variability (R2 > 0.92) suggested that community recovery rates were controlled by a combination of physical and ecological features operating across spatial scales, affecting successional processes. The dynamic and complex interplay of ecological and environmental processes we observed driving patch recovery across the estuarine landscape are integral to recovery from disturbances in heterogeneous environments. This link between succession/recovery, disturbance, and heterogeneity confirms the utility of disturbance-recovery experiments as assays for cumulative change due to fragmentation and habitat change in estuaries.     

Herbivores and edaphic factors constrain the realized niche of a native plant

Biotic interactions, such as competition and herbivory, can limit plant species ranges to a subset of edaphically suitable habitats, termed the realized niche. Here we explored the role that herbivores play in restricting the niche of serpentine ecotypes of the native California annual Collinsia sparsiflora. We planted seeds from four populations into a range of natural field environments that varied in the presence/absence of naturally occurring C. sparsiflora and in predicted suitability for growth and survival of the serpentine ecotype of C. sparsiflora. Path analysis was then used to model the direct and herbivore-mediated indirect effects of environmental variables on the survival of C. sparsiflora serpentine ecotypes. We found that C. sparsiflora received more herbivory when planted into areas where serpentine ecotypes of C. sparsiflora were not predicted to persist, and that increased herbivory was associated with decreased survival, suggesting that herbivores may limit the distribution of C. sparsiflora serpentine ecotypes. Additionally, we demonstrated that edaphic environmental variables impacted the survival of C. sparsiflora serpentine ecotypes both directly and indirectly, by altering interactions with herbivores. These indirect effects were probably trait-mediated and probably occurred because edaphic factors may influence plant traits that, in turn, alter attractiveness to herbivores. Although the magnitude of direct effects exceeded the magnitude of indirect effects, many strong herbivore-mediated indirect effects were detected. Thus, interactions between the abiotic environment and insect herbivory contributed to restricting the niche of C. sparsiflora serpentine ecotypes to a subset of available habitat.     

Controls of spatial variation in the prevalence of trematode parasites infecting a marine snail

Geographic variability in abundance can be driven by multiple physical and biological factors operating at multiple scales. To understand the determinants of larval trematode prevalence within populations of the marine snail host Littorina littorea, we quantified many physical and biological variables at 28 New England intertidal sites. A hierarchical, mixed-effects model identified the abundance of gulls (the final hosts and dispersive agents of infective trematode stages) and snail size (a proxy for time of exposure) as the primary factors associated with trematode prevalence. The predominant influence of these variables coupled with routinely low infection rates (21 of the 28 populations exhibited prevalence <12%) suggest broad-scale recruitment limitation of trematodes. Although infection rates were spatially variable, formal analyses detected no regional spatial gradients in either trematode prevalence or independent environmental variables. Trematode prevalence appears to be predominantly determined by local site characteristics favoring high gull abundance.