Bechstein’s bats maintain individual social links despite a complete reorganisation of their colony structure

Several social mammals, including elephants and some primates, whales and bats, live in multilevel societies that form temporary subgroups. Despite these fission–fusion dynamics, group members often maintain long-term bonds. However, it is unclear whether such individual links and the resulting stable social subunits continue to exist after a complete reorganisation of a society, e.g. following a population crash. Here, we employed a weighted network analysis on 7,109 individual roosting records collected over 4 years in a wild Bechstein’s bat colony. We show that, in response to a strong population decline, the colony’s two stable social subunits fused into a non-modular social network. Nevertheless, in the first year after the crash, long-term bonds were still detectable, suggesting that the bats remembered previous individual relationships. Our findings are important for understanding the flexibility of animal societies in the face of dramatic changes and for the conservation of social mammals with declining populations.

     

The Control of an Invasive Bivalve, Corbicula fluminea, Using Gas Impermeable Benthic Barriers in a Large Natural Lake

Anoxia can restrict species establishment in aquatic systems and the artificial promotion of these conditions can provide an effective control strategy for invasive molluscs. Low abundances (2-20 m(-2)) of the nonnative bivalve, Asian clam (Corbicula fluminea), were first recorded in Lake Tahoe, CA-NV in 2002 and by 2010 nuisance-level population densities (>10,000 m(-2)) were observed. A non-chemical control method using gas impermeable benthic barriers to reduce dissolved oxygen (DO) concentrations available to C. fluminea was tested in this ultra-oligotrophic natural lake. In 2009, the impact of ethylene propylene diene monomer (EPDM) sheets (9 m(2), n = 6) on C. fluminea beds was tested on 1-7 day intervals over a 56 day period (August-September). At an average water temperature of 18 °C, DO concentrations under these small barriers were reduced to zero after 72 h resulting in 100 % C. fluminea mortality after 28 days. In 2010, a large EPDM barrier (1,950 m(2)) was applied to C. fluminea populations for 120 days (July-November). C. fluminea abundances were reduced over 98 % after barrier removal, and remained significantly reduced (>90 %) 1 year later. Non-target benthic macroinvertebrate abundances were also reduced, with variable taxon-specific recolonization rates. High C. fluminea abundance under anoxic conditions increased the release of ammonium and soluble reactive phosphorus from the sediment substrate; but levels of unionized ammonia were low at 0.004-0.005 mg L(-1). Prolonged exposure to anoxia using benthic barriers can provide an effective short term control strategy for C. fluminea.     

SUBALPINE,COLD CLIMATE,STORMWATER TREATMENT WITH A CONSTRUCTED SURFACE FLOW WETLAND1

The Tahoe City Wetland Treatment System (TCWTS) was constructed in 1997 to treat stormwater runoff from 23 ha of commercial, highway, and residential land use in the Lake Tahoe Basin. This subalpine, constructed, surface flow wetland treatment system consists of two cells in series, with a design water surface area of about 0.6 ha. Water quality monitoring from October 2002 through September 2003 was conducted with autosamplers at the inflow and outflow sites during 24 sampling events, with a median duration of 53 hours, representing 42 percent of total inflow to this wetland during the year. Monitoring data indicate an improvement of 49 percent or greater in effluent concentrations of dissolved phosphorus, nitrate, orthophosphorus, and total suspended solids. On average, event mean concentrations of total phosphorus were reduced from a median 279 μg/l at the inflow to 94 μg/l at the outflow. Event mean concentrations of total nitrogen were reduced from a median 1,599 μg/l at the inflow to 810 μg/l at the outflow. Net nutrient retention for the sampling period was estimated at 3 g phosphorus (P)/m²/y and 13 g nitrogen (N)/m²/y. Almost 4,000 kg of suspended sediment was captured by this wetland system during the year.     

Die Umsetzung des EU Weißbuches zur Chemikalienpolitik

Background

Aim and Scope. Implementation of the European Union White Paper on chemicals policy shall provide more safety and more transparency in chemicals use. In the past, when assessing existing commercial substances there was often a lack of information in the fields of application of the chemicals and the exposures arising in those contexts. The White Paper therefore calls for ‘shared responsibility’. Processors and commercial users of substances are to be involved much more closely in the risk evaluation process than has hitherto been the case. They are to provide data on substance applications and exposures, and, to some extent, they are also to carry out exposure assessments and risk assessments themselves. By analysing case studies, the paper highlights the consequences of this approach.

Results and Discussion

Fear has often been voiced that these new tasks will completely overburden small and medium-sized enterprises. It is assumed that many chemicals are no longer available for smallvolume applications, as — for cost reasons — producers do not include these applications in their registration. The wording of the White Paper is not precise enough to be able to appraise the costs that will be associated with the required intensified communication. In this situation, it is essential to analyse prototypical substances and their applications in order to gain an improved understanding of the principle of shared responsibility.

Conclusions

The concrete study of several product chains has shown that the flow of information required between producers and users is very likely feasible within the context of the REACH system. For the producers of chemicals, the intensified communication will presumably make it simpler to procure information in the fields of application and exposures. However, in order to avoid users being overburdened, it will be important that registration requirements and focuses are shaped in a manner doing justice to practical realities. Users will need to undertake community-wide efforts on an industry federation and branch level. In this context, the protection of company know-how also needs to be ensured.

Recommendation and Outlook

In practice, implementation of the principle of shared responsibility can lead to intensified communication among the producers and users of chemicals. This can greatly facilitate exposure assessments and risk assessments. There is a need to develop manageable procedures that can also be implemented by small and medium-sized enterprises. Numerous proposals have been made in this context, and extensive reference material is now available.     

Information system for monitoring environmental impacts of genetically modified organisms

Background, aim and scope  

European legislation stipulates that genetically modified organisms (GMO) have to be monitored to identify potential adverse environmental effects. A wealth of different types of monitoring data from various sources including existing environmental monitoring programmes is expected to accumulate. This requires an information system to efficiently structure, process and evaluate the monitoring data.     

Stream Phosphorus Transport in the Lake Tahoe Basin, 1989–1996

Lake Tahoe is undergoing the initial stages of culturaleutrophication due to human alteration of the airshed andwatershed. The lake's switch from nitrogen (N) to phosphorus (P)limitation has been attributed primarily to atmospheric Nloading. This places an increased importance on controllingwatershed movement of P to the lake. A stream water qualitymonitoring data set consisting of nine streams in the Lake Tahoebasin has been analyzed to characterize the spatiotemporalvariation of P delivery to the lake. This data is from the LakeTahoe Interagency Monitoring Program (LTIMP), which providesscientific data for planning and regulatory agencies to addressenvironmental problems in the Lake Tahoe basin. Results indicatethat P delivery (concentrations, loads) varies greatly atinterannual, seasonal, and spatial scales. Annual and seasonaltotal P (TP) concentrations can vary up to three orders ofmagnitude in a given stream and are strongly associated withsuspended sediment. Particulate P is the major form of Ptransported by Tahoe streams and was strongly correlated withpercent surficial geologic deposits, which are primarily locatednear streams. Tahoe streams with the highest annualP concentrations often had the lowest annual P loads, and visaversa. P loading is greatest during the spring snowmelt (75% ofannual average). Potential watershed parameters influencing Pdelivery to Lake Tahoe have been identified as precipitation,basin area, basin steepness, and road and human developmentcoverage. Results also suggest that human development impacts onstream P loads are most prevalent during high precipitationyears. Identification and quantification of stream sediment andP sources such as streambanks and impervious surface isnecessary to aid in watershed restoration efforts.