Temporal mangrove dynamics in relation to coastal development in Pacific Panama

This study assessed the changes in extent of fringing mangrove located in Punta Mala Bay, Panama in relation to coastal development over a period of two decades. Punta Mala Bay was chosen for this study, due to its social importance and its biological significance, as it is one of the few mangrove areas left around Panama City. Fieldwork confirmed the importance of Laguncularia racemosa in the bay, which formed nearly monospecific stands with a large number of seedlings indicating that the forest was rejuvenating. The mangrove was mapped from 1980 to 2002 using digitised aerial photographs and a GIS was used to determine the location and rates of mangrove growth and loss before and after the construction of a road and water treatment works in 1998. The land use maps were produced with an overall accuracy of 83.8%. The user's accuracy of the maps for L. racemosa dominated stands was 89.7%, although the producer's accuracy was lower due to the omission of seedlings on intertidal areas. It was found that the mangrove was spatially dynamic and had grown substantially in the bay at a rate ranging from 6 to 215% per year until the construction commenced. Between 1997 and 2002 there were 100% loss of mangrove in some areas due to the coastal development. The resilience of the dominant species L. racemosa at this locality was shown by the continued growth of two mangrove zones during the construction period 1997-2002, with one zone increasing in area by 61%. The pioneering ability of L. racemosa after disturbance was demonstrated by the development of two new mangrove zones of 498 and 1254 m2 on bare intertidal areas after construction finished. Future mapping and fieldwork could provide information on the development of mangrove communities and their response to reoccurring human impacts.     

Patterns of short-term sedimentation in a freshwater created marsh

This study investigated different sedimentation measurement techniques and examined patterns of short-term sedimentation in two 1-ha replicate created freshwater marshes in central Ohio, USA. Short-term (one-year) sediment accumulation above feldspar, clay, glitter, and sand artificial marker horizons was compared at different water depths and distances from wetland inflow. A sediment budget was also constructed from turbidity and suspended sediment data for comparison with marker horizons. Glitter and sand marker horizons were the most successful for measuring sediment accumulation (81-100% marker recovery), while clay markers were completely unsuccessful. The sedimentation rate for both wetlands averaged 4.9 cm yr(-1) (36 kg m(-2) yr(-1)), and ranged from 1.82 to 9.23 cm yr(-1) (12.4 to 69.7 kg m(-2) yr(-1)). Sedimentation rates in deep, open water areas were significantly higher than in shallow, vegetated areas for both wetlands (t test, p < 0.05). However, observed sedimentation patterns may be attributed more to preferential flow through open water areas than to water depth or presence of vegetation. Contrary to the expected spatial distribution, sedimentation was highly variable within the wetlands, suggesting that bioturbation and turbulence may cause significant resuspension or that high hydrologic loads may distribute sediments throughout the basins. A sediment budget estimated sediment retention of approximately 740 g m(-2) yr(-1) per wetland (43% removal rate), yet gross sediment accumulation was 36,000 g m(-2) yr(-1) measured by marker horizons. These results suggest that erosive forces may have influenced sedimentation, but also may indicate problems with the sediment budget calculation methodology.     

Identifying relationships between baseflow geochemistry and land use with synoptic sampling and R-mode factor analysis

The relationship between land use and stream chemistry is often explored through synoptic sampling of rivers at baseflow conditions. However, baseflow chemistry is likely to vary temporally and spatially with land use. The purpose of our study is to examine the usefulness of the synoptic sampling approach for identifying the relationship between complex land use configurations and stream water quality. This study compares biogeochemical data from three synoptic sampling events representing the temporal variability of baseflow chemistry and land use using R-mode factor analysis. Separate R-mode factor analyses of the data from individual sampling events yielded only two consistent factors. Agricultural activity was associated with elevated levels of Ca2+, Mg2+, alkalinity, and frequently K+, SO4(2-), and NO3-. Urban areas were associated with higher concentrations of Na+, K+, and Cl-. Other retained factors were not consistent among sampling events, and some factors were difficult to interpret in the context of biogeochemical sources and processes. When all data were combined, further associations were revealed such as an inverse relationship between the proportion of wetlands and stream nitrate concentrations. We also found that barren lands were associated with elevated sulfate levels. This research suggests that an individual sampling event is unlikely to characterize adequately the complex processes controlling interactions between land use and stream chemistry. Combining data collected over two years during three synoptic sampling events appears to enhance our ability to understand processes linking stream chemistry and land use.     

Energy efficiency of farming systems: Organic and conventional agriculture

An assessment was made of the energy efficiency, yield performance, and labor requirements for the production of corn, wheat, potatoes, and apples using organic (without synthetic chemical fertilizers and pesticides) and conventional farming technologies. Organic corn and wheat production was 29–70% more energy efficient than conventional production. However, conventional potato and apple production was 7–93% more energy efficient than organic production. For all four crops, the labor input per unit of yield was higher for organic systems compared with conventional production.     

Natural attenuation of chlorinated solvent plumes at Texas dry cleaners

Dry cleaners are the largest users of perchloroethene (PCE) solvents in the United States. Releases from dry cleaners to soil and groundwater, however, remain largely unstudied. This article presents a database of 137 chlorinated solvent plumes at dry cleaners in Texas. The data indicate that PCE plumes are generally shorter in extent than those from industrial sites. Degradation products were observed at more than 80 percent of the sites with groundwater contamination. Calculated attenuation rates are on the order of one‐to‐three‐year half‐lives for PCE and its degradation products. The estimated cleanup timeframe for calculated attenuation rates is < 50 years. More research is needed to understand the presence of organic carbon sources at dry cleaners and its implications for natural attenuation. © 2004 Wiley Periodicals, Inc.     

Environmental impact assessment in the People's Republic of China: a case study of the Shanghai Second Sewerage Project

In March 1994, China announced its plans for sustainable development in a White Paper entitled 'China's Strategy for Population, Environment and Development in the 21st Century. To achieve the objective of sustainable development; economic, social and environmental aims have to be consistent with each other and meet the needs of the present, without compromising the ability of future generations to meet their own needs. Sustainable development, therefore, encompasses many 'ideals, which need to be introduced through practical management techniques. This paper addresses the role that EIA could play in promoting sustainable development projects in the People's Republic of China by way of the detailed examination of a case study—the Shanghai Second Sewerage Project.     

Using Steady‐State Backwater Analysis to Predict Inundated Area from National Water Model Streamflow Simulations

National Water Model (NWM) simulates the hydrologic cycle and produces streamflow forecasts for 2.7 million reaches in the National Hydrography Dataset for continental United States (U.S.). NWM uses Muskingum–Cunge channel routing, which is based on the continuity equation. However, the momentum equation also needs to be considered to obtain more accurate estimates of streamflow and stage in rivers, especially for applications such as flood‐inundation mapping. Here, we used a steady‐state backwater version of Simulation Program for River NeTworks (SPRNT) model. We evaluated SPRNT’s and NWM’s abilities to predict inundated area for the record flood of Hurricane Matthew in October 2016. The Neuse River experienced record‐breaking floods and was well‐documented by U.S. Geological Survey. Streamflow simulations from NWM retrospective analysis were used as input for the SPRNT simulation. Retrospective NWM discharge predictions were converted to stage. The stages (from both SPRNT and NWM) were utilized to produce flood‐inundation maps using the Height Above Nearest Drainage method which uses the local relative heights to find out the local draining potentials and provide spatial representation of inundated area. The inundated‐area accuracies for NWM and SPRNT (based on comparison to a remotely sensed dataset) were 65.1% and 67.6%, respectively. These results show using steady‐state SPRNT results in a modest improvement of inundation‐forecast accuracy compared to NWM.     

Prioritizing Stream Barrier Removal to Maximize Connected Aquatic Habitat and Minimize Water Scarcity

Instream barriers, such as dams, culverts, and diversions, alter hydrologic processes and aquatic habitat. Removing uneconomical and aging instream barriers is increasingly used for river restoration. Historically, selection of barrier removal projects used score‐and‐rank techniques, ignoring cumulative change and the spatial structure of stream networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. Here, a dual‐objective optimization model identifies barriers to remove that maximize connected aquatic habitat and minimize water scarcity. Aquatic habitat is measured using monthly average streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using economic penalty functions while a budget constraint specifies the money available to remove barriers. We demonstrate the approach using a case study in Utah's Weber Basin to prioritize removal of instream barriers for Bonneville cutthroat trout, while maintaining human water uses. Removing 54 instream barriers reconnects about 160 km of quality‐weighted habitat and costs approximately US$10 M. After this point, the cost‐effectiveness of removing barriers to connect river habitat decreases. The modeling approach expands barrier removal optimization methods by explicitly including both economic and environmental water uses.     

An assessment of toxicity in profundal lake sediment due to deposition of heavy metals and persistent organic pollutants from the atmosphere

A Tier I Sediment Ecological Risk Assessment of profundal lake sediment contaminated by diffuse pollution of heavy metals and POPs deposited from the atmosphere was completed. The concentrations of seven heavy metals and four groups of POPs (OCs, PCBs, PAHs, PBDEs) were determined in the profundal sediment of ten lakes in the United Kingdom and two sediment toxicity tests completed (chironomid survival and emergence and cladoceran survival and reproduction). The results showed that around half the lakes are at least moderately contaminated by Pb, Zn, Cd, As and PAHs deposited from the atmosphere and the toxicity quotient suggests that the contaminants of concern are Pb, As and PAHs, and not the other metals nor OCs and PCBs. There was toxicity in the sediment of four of the lakes. The Probable Effect Concentration Quotient values indicated that metals in the sediments of Scoat Tarn, Agden Reservoir and Llyn Llagi were likely to be responsible for the laboratory toxicity found in these lakes, with PAHs also contributing in Agden Reservoir.     

Effect of Forest Fragmentation on Genetic Diversity and Mating System in a Tropical Tree, Pithecellobium elegans

Genetic diversity, population differentiation, and temporal variation in outcrossing rates were examined for Pithecellobium elegans , a Neotropical rain forest canopy tree. Several forest fragments and a large reserve (1500 ha) were compared for several population genetic parameters. For eight populations sampled on the Atlantic coastal plain of Costa Rica, allozyme heterozygosity (0.13), polymorphism (35%), and effective number of alleles (1.24) were similar to values reported for other tropical tree species that occur at similar densities of less than one individual per hectare. These measures of genetic variation were lowest in populations of the smallest size, farthest from the reserve, and more isolated from other populations. Differentiation among samples collected in small forest fragments and the reserve population accounted for 10% of the total genetic variation observed. There was a positive relationship between the level of differentiation of populations from the reserve population and their distance from the reserve. Though predominantly an annually flowering species, the number of trees in flower at any one time varied from 80% of observed trees to only 6%. Outcrossing rates did not differ for two episodes in which the proportions of flowering trees were 33% and 80%. But periods of low density of flowering adults resulted in poor seed crops or failure to set fruit for many individuals. Population size at many sites will be effectively decreased because of the variation in flowering. Fragmentation of what was once a large, continuous forested area is resulting in genetic erosion of small, isolated populations of Pithecellobium elegans .