A tool for rapid assessment of erosion risk to support decision-making and policy development at the Ngenge watershed in Uganda

This study tests a rapid, user-friendly method for assessing changes in erosion risk, which yields information to aid policy development and decision-making for sustainable natural resources management. There is currently a lack of timely, up-to-date and current information to support policy development on sustainable natural resources management in Uganda. The study was carried out in the Ngenge watershed, a typical catchment in the Ugandan Highlands, characterised by deforestation in favour of subsistence agriculture without adequate soil and water conservation measures. The watershed is experiencing soil erosion, sedimentation and flooding problems which are threatening agricultural productivity and food security. Sustainable management of environmental resources is needed to ensure a livelihood for the rural population which is dependent on the land. Historical erosion risk was evaluated in three steps using multi-temporal satellite data. First, current erosion risk was assessed by combining slope and vegetation cover during periods of high intensity rainfall. The data used for the assessment was obtained from public (free) satellite images. Erosion risk was then linked to land use and finally to the change in vegetation cover over the years 1980-2000. The analysis of erosion risk using rainfall, slope and NDVI (Normalised Difference Vegetative Index) as a proxy for vegetation cover gives an indication of the current erosion risk in the area. The results of historical vegetation cover change analysis indicate an overall increase in areas under erosion risk in the study area from 1980 to 2000. This method of erosion risk mapping provides a quick and straightforward means for identifying priority areas for interventions for soil and water resource management. Considering that resources are limited, the interventions to be appropriate have to be focused mainly on areas affected by degradation.     

Affluent effluent: growing vegetables with wastewater in Melbourne, Australia—a wealthy but bone-dry city

Water scarcity in Australia has become a significant challenge for all water users and water reuse is now a critical component of Melbourne’s response to this water crisis, particularly for food production. While most vegetable production occurs in a large-scale commercial environment, there is a significant proportion produced in backyards. With the introduction of severe water restrictions, commercial vegetable production now relies heavily on high quality Class A reclaimed water, while households have turned to the use of greywater. While there are many benefits of wastewater reuse, there are also many potential risks to plant, environmental and human health. A quantitative microbial risk assessment of the two systems was conducted to evaluate the human health risks associated with both large-scale and backyard reuse of water for vegetable irrigation. This preliminary model suggests that for irrigation with typical greywater, the annual infection probability for enteric viruses is >10^?4, even after a two week period of no irrigation with greywater. The human annual enteric virus risk from Class A reclaimed water was much lower.     

Modelling decomposition of sugar cane surface residues with APSIM–Residue

Since residues on the soil surface affect the soil hydrological and nitrogen cycles, cropping system models need to accurately predict the decomposition of surface residues through time. Recent field measurements of sugar cane residue decomposition have found that rates of residue decomposition are slower than those predicted by the agricultural productions systems simulator (APSIM) cropping system model. To improve predictions of sugar cane residue decomposition in APSIM, a new function relating decomposition rate to mass of residues was developed, and parameter values in other functions modified in the APSIM–Residue model. Predictions were compared to measurements of residue decomposition made over 1 year in five field experiments located at sites with contrasting climates in the Australian sugar industry. The new function was found to provide more accurate predictions of decomposition of large (>10 t DM ha⁻¹) masses of residue that are common with sugar cane crops. To better predict residue masses below 5–7 t ha⁻¹, the values of parameters describing the potential decomposition rate (i.e., decomposition without environmental or residue quality constraints) and constraints to decomposition from sub-optimal temperatures were determined by applying a numerical optimisation technique to measurements made at two of the field experiments. These two experiments were chosen because they had a large difference in initial residue mass (7.7 and 19.6 t ha⁻¹) and included data on soil moisture. These latter measurements, which were not made in the other experiments, provided rigorous data for the function describing the moisture limitation to residue decomposition. Using the optimised parameter values, predictions of residue decomposition in the other three experiments were close to measured values. This study illustrates the potential importance of considering initial residue mass in predictions of decomposition in sugar cane systems. The function relating decomposition rate to mass of residues may be useful for other models applied in cropping systems with high residue masses. The study also provided further evidence that some parameters in APSIM–Residue, notably the potential decomposition rate, may be crop-specific.     

Leaf chlorophyll readings as an indicator of nitrogen status and yield of spinach (Spinacia oleracea L.) grown in soils amended with Luecaena leucocephala prunings

A field study was conducted to evaluate the nitrogen status and yield of spinach grown in soils amended with prunings of Leucaena leucocephala, (applied at a rate of 3, 5, 7 or 11 t ha^?1). A ‘no fertilizer’ 0 nitrogen (N) and 150 kg N ha^?1 (recommended) were the control treatments. SPAD readings were recorded for the top six leaves. Nitrogen sufficiency indices were used to indicate the N status of plants. Application of L. leucocephala prunings increased spinach yields (8.98–13.86 t DM ha^?1) relative to the 0N treatment (1.35 t DM ha^?1) and yields increased with increasing rate of pruning application. SPAD readings showed a linear increase with the increase in applied prunings. There was preferential distribution of N to upper leaves. The relationship between shoot N concentration and SPAD readings was linear and strongest for the top three leaves (r² = 0.84–0.92). The results indicate the potential of chlorophyll meter readings in assessing N status of leafy vegetables grown on soils amended with different levels of legume tree prunings.     

Importance of DNA quality in comparative soil microbial community structure analyses

This study assessed how different in-situ lysis soil DNA extraction methods influence the DNA yield, quality and hence the results obtained by bacterial and fungal automated ribosomal intergenic spacer analysis (ARISA). Of the methods tested in three soils, a modified hexadecyltrimethylammonium bromide-dithiotreitol (CTAB-DTT)-based method produced ?3 times more DNA of higher quality than the other methods (260/230 nm ratios=1.64–1.82 and 260/280 nm ratios=1.82–1.89 and extracts were less inhibitory of PCR). DNA extracted by this method also yielded more reproducible ARISA ribotypes (89?119 for bacteria and 48?88 for fungi; P<0.05) than DNA extracted by other methods, and consequently produced more reliable estimates of bacterial and fungal diversity in all three test soils. The significant correlations observed between the numbers of reproducible ribotypes and DNA extract 260/230 nm ratios (r=0.88 and 0.72 for bacteria and fungi, respectively; P<0.001) reaffirmed the strong influence of DNA quality on the reliability of microbial diversity indices determined based on PCR-based DNA fingerprinting technique. Results of discriminant function analysis (DFA) and multivariate analysis of variances (MANOVA) performed on ARISA profiles (number and relative abundance of ribotype) revealed that the variability associated with DNA extraction methods did not exceed the biological variability among soil types; this supports the conclusion that high-quality DNA underpins DNA fingerprinting techniques.     

Cooking decreases observed perfluorinated compound concentrations in fish

Dietary intake is a major route of exposure to perfluorinated compounds (PFCs). Although fish and seafood contribute significantly to total dietary exposure to these compounds, there is uncertainty with respect to the effect of cooking on PFC concentrations in these foods. Eighteen fish species purchased from markets in Toronto, Mississauga, and Ottawa, Canada were analyzed for perfluorooctanesulfonamide (PFOSAs)-based fluorochemicals and perfluorinated acids (PFAs) in raw and cooked (baked, boiled, fried) samples. Of 17 analytes, perfluorooctanesulfonic acid (PFOS) was detected most frequently; concentrations ranged from 0.21 to 1.68 ng/g ww in raw and cooked samples. PFOSAs were detected only in scallops at concentrations ranging from 0.20 ng/g ww to 0.76 ng/g ww. Total concentrations of PFAs in samples were 0.21 to 9.20 ng/g ww, respectively, consistent with previous studies. All cooking methods reduced PFA concentrations. Baking appeared to be the most effective cooking method; after baking samples for 15 min at 163 C (325 degrees F), PFAs were not detected in any of the samples. The margin of exposures (MOE) between the toxicological points of reference and the dietary intake of perfluorocarboxylates (PFCAs) and PFOS in fish and seafood muscle tissue were greater than 4 orders of magnitude. This indicates that reducing consumption of fish muscle tissue is not warranted on the basis of PFC exposure concerns at the reported levels of contamination, even for high fish consuming populations.     

Evolutionary impact assessment: accounting for evolutionary consequences of fishing in an ecosystem approach to fisheries management

Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries‐induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life‐history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries.     

Effects of trap fishing on reef fish communities

• 1. Trap fishing is widespread on coral reefs but the sustainability of this practice is causing concern because it is efficient and unselective. The effects of trap fishing were investigated by comparing fish assemblages among six Caribbean islands subject to different trapping pressures. These ranged from none in Bonaire and Saba increasing through Puerto Rico, St Lucia, Dominica and Jamaica respectively.
• 2. Fish were censused at depths of 5 m and 15 m on fore‐reef slopes by counting the numbers within replicate 10 m diameter areas for 15 min. Between 64 and 1375 counts were made in each country.
• 3. In St Lucia and Jamaica abundance of fish censused on the reef was compared to representation in traps which were visually sampled underwater in the area of fish counts. Twenty‐three traps were sampled in Jamaica and 75 in St Lucia. For some comparisons between these islands, St Lucian sampling effort was reduced to that of Jamaica (23 traps and 112 counts) by randomly sub‐sampling 10 times.
• 4. Traps contained 54 different species in St Lucia and 22 in Jamaica, while there were 90 and 57 respectively in counts. After reducing St Lucian sampling effort to Jamaican levels, an average of 35 species were found in traps and 70 seen in counts. Of these, 76% in St Lucia and 73% in Jamaica were relatively more abundant in traps than they were on the reef.
• 5. Species were considered to be highly susceptible to trapping if the ratio of their abundance in traps compared to that on the reef exceeded 3:1. Trapping pressure was approximately three and a half times greater in Jamaica than St Lucia. After equalizing sampling effort, there was an average of 16 highly trappable species in St Lucia compared to 13 in Jamaica. Species did not always appear highly trappable in both countries. Eleven of St Lucia's highly trappable species were absent from Jamaica (falling to 8.5 on average after equalizing sampling effort), but none vice versa, suggesting that trapping may have contributed to their absence or rarity on Jamaican reefs.
• 6. The Tetraodontiformes, which include many non‐target species, were particularly susceptible to trapping in both countries. Their abundance in the six islands censused was inversely related to trap fishing pressure, as was that of two other non‐target families, butterflyfish (Chaetodontidae) and angelfish (Pomacanthidae).
• 7. To determine whether fish that are common in traps in St Lucia are reaching sexual maturity before capture, size frequency data for 23 species from a sample of trap catches were gathered and examined for their state of maturity. In seven species, more than a third of 705 trapped fish were immature, indicating that trap fishing causes growth over‐fishing (premature removal of fish), and calling into question the sustainability of yields for these species.
• 8. In conclusion, at the intensities seen in this study, trap fisheries cause serious over‐fishing, reduce biodiversity, and alter ecosystem structure. While commonly perceived as low impact, coral reef trap fisheries in the Caribbean and further afield, need tighter regulation and control.

Copyright © 2006 John Wiley & Sons, Ltd.     

Genetic diversity of piscine myocarditis virus in Atlantic salmon Salmo salar L. in Ireland

Piscine myocarditis virus (PMCV) is a double‐stranded RNA virus which has been linked to cardiomyopathy syndrome (CMS) in Atlantic salmon (Salmo salar L.). The first recorded outbreak of CMS in Ireland occurred in 2012. Heart tissue samples were collected in the current study from farmed Atlantic salmon from various marine sites around Ireland, and the open reading frames (ORFs) 1 and 3 were amplified and sequenced in order to examine the genetic diversity of PMCV. Results showed PMCV to be largely homogenous in Irish samples, showing little genetic diversity. However, several amino acid positions within both ORF1 and ORF3 showed consistent variations unique to the Irish PMCV strains when compared with previously published Norwegian strains. The phylogeny generated in the present study suggests that PMCV may have been introduced into Ireland in two waves, both coming from the southern part of PMCV's range in Norway. In addition, over three‐quarters of the PMCV strains which were sequenced came from fish not exhibiting any clinical signs of CMS, suggesting that either PMCV is evolving to become less virulent in Ireland or Irish Atlantic salmon are developing immunity to the disease.