Cadmium in aquatic ecosystems in Western Australia: A legacy of nutrient-deficient soils

More than 273 tonnes of cadmium have been added to Western Australian ecosystems through the application of superphosphate fertilisers since 1982. Fifty percent of this is water soluble and therefore eventually leaches into waterbodies and accumulates in the sediments. From this source, it enters the food web through algae and benthic animals and may ultimately be passed to humans. This is reflected in the cadmium levels of the freshwater mussels (Westralunio carteri) that exceeded statutory Australia New Zealand Food Authority (ANZFA) guidelines for Maximum Permissible Concentrations (MPCs) with respect to human consumption. The cadmium levels bioaccumulated in freshwater mussels elevated with increasing catchment clearing, being highest in degraded catchments. The MPC for Cd in crustaceans have recently been removed, yet tissues within the freshwater crayfish (Cherax tenuimanus) frequently exceeded the old MPC (0·2 μCd g⁻¹wet weight). Marron are sometimes consumed in considerable quantities and the risk to human health posed by a high Cd intake is briefly summarised. Finally, a number of management options concerned with reducing the level of Cd from fertilisers passing to humans are reviewed.     

A practical approach to predict the duration of the growing season for European lakes

This work presents the first practically useful models to estimate the duration of the growing season (GS in days) for European lakes. GS is a fundamental parameter in limnology, where it is used, e.g., to calculate lake characteristic annual primary production (in g ww/m²·yr) from measurement data in g C/l·day. We have presented two simple empirical regression equations where GS is estimated from latitude. We have also introduced a more comprehensive model. It is derived from a previously presented well calibrated and validated model predicting lake epilimnetic temperatures from readily available data on latitude, altitude, continentality (distance from the Sea) and lake volume. Operationally, the duration of the growing season (GS in days) is defined from the predicted number of days when epilimentic water temperatures are higher than 9°C. The two modelling approaches are based on different presuppositions and they have been derived and tested from different data-sets. A model comparison has shown that the overall correspondence in predicted GS-values between the methods is very good. Evidently, the more comprehensive model can provide more relevant GS-predictions for many lakes since it also accounts for differences among lakes in altitude, continentality and volume.     

Ecogenetic Characteristics of Dandelion (Taraxacum officinale s.l.) Populations from the Techa River Floodplain Ecosystems

This study looks into T. officinale cenopopulations growing in the Techa River floodplain under conditions of chronic low-dose irradiation. It has been shown that the left-bank and right-bank cenopopulations differ from one another, as well as from the control (background) population, in the allozyme structure, viability, and radioresistance of the seed progeny and the mechanisms of antioxidant protection. In nature, cenopopulations differing in their phenogenetic structure may have different strategies of adaptation to the chronic influence of low radiation doses against the background of changing environmental conditions. The consequences of irradiation for such cenopopulations, including the viability and radiosensitivity of their seed progenies, may also differ considerably.     

ROOT BIOMASS IN RELATION TO CHANNEL MORPHOLOGY OF HEADWATER STREAMS1

ABSTRACT: Intact riparian zones are the product of an incredibly complex multitude of linkages between the geomorphic, hydrologic, and biotiè features of the ecosystem. Land‐use activities that sever or alter these linkages result in ecosystem degradation. We examined the relationship between riparian vegetation and channel morphology by sampling species composition and herbaceous root biomass in incised (down‐cut and widened) versus unincised (intact) sections of unconstrained reaches in three headwater streams in northeastern Oregon. Incision resulted in a compositional shift from wetland‐obligate plant species to those adapted to drier environments. Root biomass was approximately two times greater in unincised sections than incised sections and decreased with depth more rapidly in incised sections than in unincised sections. Total root biomass ranged from 2,153 g m^‐2 to 4,759 g m^‐2 in unincised sections and from 1,107 g m^‐2 to 2,215 g m^‐2 in incised sections. In unincised sections less than 50 percent of the total root biomass was found in the top 10 cm, with approximately 20 percent in successive 10‐cm depth increments. In contrast, incised sections had greater than 60 percent of the total root biomass in the top 10 cm, approximately 15 percent in the 10 to 20 cm depth, less than 15 percent in the 20 to 30 cm depth, and less than 10 percent in the 30 to 40 cm depth. This distribution of root biomass suggests a positive feedback between vegetation and channel incision: as incision progresses, there is a loss of hydrologic connectivity, which causes a shift to a drier vegetation assemblage and decreased root structure, resulting in a reduced erosive resistance capacity in the lower zone of the streambank, thereby allowing further incision and widening.     

水生态系统服务功能价值评估研究综述

随着人类认识的不断进步,水生态系统服务功能价值的分类及评估方法逐渐形成。专家们对湿地、湖泊、水库等生态系统的服务功能价值进行了评估。但评估方法尚不成熟,服务功能分类缺乏统一的标准,以瞬时静态评估为主,不能充分体现各个生态系统的特征和空间异质性。     

A preliminary assessment of socio-ecological metabolism for three neighborhoods within a rust belt urban ecosystem

Rust belt cities of the northeastern United States are plagued by flat or declining economies and the accompanying social fallout from lack of employment. Advocates of green fuels, green infrastructure and green jobs have proposed these nature-based technologies as means to revitalize the economies of cities. Before making public and private investment a baseline analysis of the relative magnitude of existing energy production and energy respiration at the neighborhood scale is useful in order to understand what the potential for green infrastructure might be. Because the urban canopy and other green infrastructure can enhance urban socio-ecological metabolism, we measured the flows of natural energy produced (P) by the urban forest versus the industrial or fossil energy currently consumed or respired (R) in three economically and demographically distinct neighborhoods of a typical rust-belt city, Syracuse, NY. Our objectives were to (1) understand the potential for green energy to replace fossil fuels in general, (2) assess the degree to which different socio-demographic communities are receiving the ecosystem benefits of existing urban “green” infrastructure (i.e. forest primary production), and (3) identify where local (in-city) biotic energy resources could be enhanced or fossil fuel consumption altered to improve overall urban socio-ecological metabolism. We found that (1) the fossil energy consumed in all three neighborhoods was 200-700 times higher than the biotic “green” energy produced; (2) that to produce this much energy from willow biomass grown in the region would require at least between 0.3 and 0.7 ha of bio-energy production per person depending on affluence, density of living, transportation mix and home fuel mix; (3) that although the more affluent neighborhood used, per residence and per person, almost twice as much energy as that of the downtown more densely settled and poorer neighborhood, its R:P ratio was still the lowest due to the high primary productivity of its neighborhood tree canopy. As a first assessment our findings identify several opportunities for enhancement of the socio-ecological metabolism of these neighborhoods, and the city at large, through conversion of heating units in poorer neighborhoods away from expensive electricity, and toward tree planting, solar installations, and per capita energy use reductions.     

Road Facilitation of Trematode Infections in Snails of Northern Alaska

Abstract:  Road disturbances can influence wildlife health by spreading disease agents and hosts or by generating environmental conditions that sustain these agent and host populations. I evaluated field patterns of trematode infections in snails inhabiting ponds at varying distances from the Dalton Highway, a wilderness road that intersects northern Alaska. I also assessed the relationships between trematode infections and snail densities and six environmental variables: calcium concentration, aquatic vegetative cover, canopy cover, temperature, pond size, and community structure. Presence of trematode infections and snail density were negatively correlated with distance from the highway. Of the pond characteristics measured, only calcium concentration and vegetation density declined with distance from road. However, neither variable was positively associated with snail density or trematode presence. One potential explanation for observed patterns is that vehicles, road maintenance, or vertebrate vectors attracted to the highway facilitate colonization of snails or trematodes. Emerging disease threats to biological diversity in northern ecosystems highlight the importance of understanding how roads affect disease transmission.     

VARIATION OF STREAM STABILITY WITH STREAM TYPE AND LWESTOCK BANK DAMAGE IN NORTHERN NEVADA1

ABSTRACT: Many natural and anthropogenic factors contribute to the stability or erodibility of stream channels. Although a stream rating procedure used by more than 60 percent of the U.S. National Forests provides an estimate of overall stability, it does not identify the cause of instability or indicate corrective management. To better sort natural from livestock influences, stream stability rating indicator variables were related to stream types and levels of ungulate bank damage in a large data base for streams in northern Nevada. Stability and the range in stability varied naturally with stream type. Ungulate bank damage had different effects on different stream types and on different parts of their cross-sections. Vegetation is more important for stability on certain stream types than on other types. Streams with noncohesive sand and gravel banks are most sensitive to livestock grazing. Range managers should consider the stream type when setting local standards, writing management objectives, or determining riparian grazing strategies.     

A MONTE CARLO TEST OF LOAD CALCULATION METHODS,LAKE TAHOE BASIN,CALIFORNIA‐NEVADA1

ABSTRACT: The sampling of streams and estimation of total loads of nitrogen, phosphorus, and suspended sediment play an important role in efforts to control the eutrophication of Lake Tahoe. We used a Monte Carlo procedure to test the precision and bias of four methods of calculating total constituent loads for nitrate‐nitrogen, soluble reactive phosphorus, particulate phosphorus, total phosphorus, and suspended sediment in one major tributary of the lake. The methods tested were two forms of the Beale's Ratio Estimator, the Period Weighted Sample, and the Rating Curve. Intensive sampling in 1985 (a dry year) and 1986 (a wet year) provided a basis for estimating loads by the “worked record” method for comparison with estimates based on resampling actual data at the lower intensity that characterizes the present monitoring program. The results show that: (1) the Period Weighted Sample method was superior to the other methods for all constituents for 1985; and (2) for total phosphorus, particulate phosphorus, and suspended sediment, the Rating Curve gave the best results in 1986. Modification of the present sampling program and load calculation methods may be necessary to improve the precision and reduce the bias of estimates of total phosphorus loads in basin streams.