Analyzing the Impacts of Dams on Riparian Ecosystems: A Review of Research Strategies and Their Relevance to the Snake River Through Hells Canyon

River damming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1) upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammed river versus an adjacent free-flowing or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions. However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies.     

Macroinvertebrate Responses to Constructed Riffles in the Cache River,Illinois, USA

Stream restoration practices are becoming increasingly common, but biological assessments of these improvements are still limited. Rock weirs, a type of constructed riffle, were implemented in the upper Cache River in southern Illinois, USA, in 2001 and 2003–2004 to control channel incision and protect high quality riparian wetlands as part of an extensive watershed-level restoration. Construction of the rock weirs provided an opportunity to examine biological responses to a common in-stream restoration technique. We compared macroinvertebrate assemblages on previously constructed rock weirs and newly constructed weirs to those on snags and scoured clay streambed, the two dominant substrates in the unrestored reaches of the river. We quantitatively sampled macroinvertebrates on these substrates on seven occasions during 2003 and 2004. Ephemeroptera, Plecoptera, and Trichoptera (EPT) biomass and aquatic insect biomass were significantly higher on rock weirs than the streambed for most sample periods. Snags supported intermediate EPT and aquatic insect biomass compared to rock weirs and the streambed. Nonmetric multidimensional scaling (NMDS) ordinations for 2003 and 2004 revealed distinct assemblage groups for rock weirs, snags, and the streambed. Analysis of similarity supported visual interpretation of NMDS plots. All pair-wise substrate comparisons differed significantly, except recently constructed weirs versus older weirs. Results indicate positive responses by macroinvertebrate assemblages to in-stream restoration in the Cache River. Moreover, these responses were not evident with more common measures of total density, biomass, and diversity.     

Photochemical behaviour of musk tibetene

BACKGROUND: Synthetic musk compounds are widely used as additives in personal care and household products. The photochemical degradation of musk tibetene in aqueous solutions or in acetonitrile/water mixtures under different conditions was studied in order to assess its environmental fate. METHODS: Musk tibetene dissolved (or suspended) in water and/or acetonitrile/water mixtures was irradiated at different times by UV-light and by solar light. The irradiation mixtures were analyzed by NMR and TLC. The photoproducts formed were identified by GC-MS and NMR data. RESULTS: The experimental results indicated that musk tibetene was photodegradable in water or acetonitrile/water mixtures with half-life reaction times close to 20 minutes. The irradiation mixtures were separated by chromatographic techniques yielding three photoproducts (3,3,5,6,7-pentamethyl-4-nitro-3H-indole, 3,3,5,6,7-pentamethyl-4-nitro-1H-indoline and 3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone) identified by means of spectroscopic analysis. DISCUSSION: The numerical modelling of the photodegradation concentration-time profiles gave (8.13 +/- 0.15) x 10(-2) and (1.34 +/- 0.04) x 10(-2) mol/E for the overall primary quantum yield of direct photolysis for musk tibetene and the major intermediate (3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone), respectively, in the wavelength range 305-366 nm. The half-life times of photodegradation of the both substances varied from 1-1.5 hours at 20 degrees N during the summer season to 6-10 hours for highest latitudes in winter. CONCLUSIONS: Under solar light, musk tibetene was photolabile in acetonitrile and acetonitrile/water 1/1, while it was slowly degraded when suspended in water. In all media, musk tibetene was photodegraded into three photoproducts. By using a kinetic model, the overall primary quantum yields of direct photolysis of musk tibetene and its main photoproduct, in the wavelength range 305-366 nm, were estimated, indicating that the photodegradation rate for musk tibetene is faster than the photolysis rate of the major by-product. RECOMMENDATIONS AND PERSPECTIVES: The results indicate that, in order to assess the environmental impact of musk tibetene on the aquatic ecosystem, great attention should be focused on the major photoproduct which is proved to be more persistent than the parent compound under light irradiation. The predicted half-life times of direct photolysis for both substances ranged from 1-1.5 hours at 20 degrees N during the summer season to about 6-10 hours for highest latitudes in winter, indicating that, from a photochemical point of view, the environmental persistence of these substances increases by increasing the latitudes and during the cold seasons, making more realistic an intake of these xenobiotic molecules into the food chain of aquatic living organisms. Tanabe reports in his Editorial (Tanabe 2005) that "It is necessary to have knowledge of the global picture of synthetic musk pathways. So, it is conceivable that now is the time to study the transport, persistency, distribution, bioaccumulation and toxic potential of this new environmental menace on a global scale, especially in developing countries". Therefore, the future environmental analysis and investigations on the eco-toxicity of nitro musk compounds should take into account not only the presence of the parent compounds but also their photochemical intermediates or end-by-products.     

Cache and carry: hoarding behavior of arctic fox

Food-hoarding animals are expected to preferentially cache items with lower perishability and/or higher consumption time. We observed arctic foxes (Alopex lagopus) foraging in a greater snow goose (Anser caerulescens atlanticus) colony where the main prey of foxes consisted of goose eggs, goslings, and lemmings (Lemmus and Dicrostonyx spp.). We recorded the number of prey consumed and cached and the time that foxes invested in these activities. Foxes took more time to consume a goose egg than a lemming or gosling but cached a greater proportion of eggs than the other prey type. This may be caused by the eggshell, which presumably decreases the perishability and/or pilfering risk of cached eggs, but also increases egg consumption time. Arctic foxes usually recached goose eggs but rarely recached goslings or lemmings. We tested whether the rapid-sequestering hypothesis could explain this recaching behavior. According to this hypothesis, arctic foxes may adopt a two-stage strategy allowing both to maximize egg acquisition rate in an undefended nest and subsequently secure eggs in potentially safer sites. Foxes spent more time carrying an egg and traveled greater distances when establishing a secondary than a primary cache. To gain further information on the location and subsequent fate of cached eggs, we used dummy eggs containing radio transmitters. Lifespan of primary caches increased with distance from the goose nest. Secondary caches were generally located farther from the nest and had a longer lifespan than primary caches. Behavioral observations and the radio-tagged egg technique both gave results supporting the rapid-sequestering hypothesis.     

A Model for Landscape Planning Under Complex Spatial Conditions

We present a new mathematical programming framework that is adaptable to a variety of spatially explicit landscape problems in environmental investment, conservation, and land-use planning, transport planning, and agriculture. As part of capturing spatial interdependencies, the framework considers decision variables at two levels, finely spaced grid cells and landholdings. We applied the framework to an environmental investment problem using objective functions representing biodiversity and carbon sequestration. We also tested the model to optimize the path of a road through part of the landscape. Using the Nambucca case study in eastern Australia, we applied a hybrid greedy randomised adaptive search procedure (GRASP) to find solutions to the model.     

Ink utilization by mesopelagic squid

Remotely operated vehicle dive video recordings of deep-sea squid ink release were examined to determine species, ink release type, release depth, and accompanying behavior/s. Ink release was commonly observed between the surface and 1,842.1 m in Monterey Bay, CA, and surrounding waters. Six ink release types were observed: pseudomorphs, pseudomorph series, ink ropes, clouds/smokescreens, diffuse puffs and mantle fills. Each species released ink throughout all or most of its depth range; inking was not limited to shallow, sunlit waters. Individuals of each species produced one ink release type more commonly than other types, however, multiple ink types could be released by individuals of all species. Common behaviors preceded and/or followed each release type; pseudomorphs and pseudomorph series were generally associated with escape behaviors, while ink ropes, clouds, and puffs normally involved the animal remaining adjacent to or amid the ink. Deep-sea squids may use ink for defensive purposes similar to those of shallow-dwelling species when they release pseudomorphs, pseudomorph series, or large clouds, and may use ink puffs in intra-specific communication. The function of ink ropes and mantle fills is unknown.     

An energy systems view of sustainability: emergy evaluation of the San Luis Basin, Colorado

Energy Systems Theory (EST) provides a framework for understanding and interpreting sustainability. EST implies that "what is sustainable" for a system at any given level of organization is determined by the cycles of change originating in the next larger system and within the system of concern. The pulsing paradigm explains the ubiquitous cycles of change that apparently govern ecosystems, rather than succession to a steady state that is then sustainable. Therefore, to make robust decisions among environmental policies and alternatives, decision-makers need to know where their system resides in the cycles of change that govern it. This theory was examined by performing an emergy evaluation of the sustainability of a regional system, the San Luis Basin (SLB), CO. By 1980, the SLB contained a climax stage agricultural system with well-developed crop and livestock production along with food and animal waste processing. The SLB is also a hinterland in that it exports raw materials and primary products (exploitation stage) to more developed areas. Emergy indices calculated for the SLB from 1995 to 2005 revealed changes in the relative sustainability of the system over this time. The sustainability of the region as indicated by the renewable emergy used as a percent of total use declined 4%, whereas, the renewable carrying capacity declined 6% over this time. The Emergy Sustainability Index (ESI) showed the largest decline (27%) in the sustainability of the region. The total emergy used by the SLB, a measure of system well-being, was fairly stable (CV?=?0.05). In 1997, using renewable emergy alone, the SLB could support 50.7% of its population at the current standard of living, while under similar conditions the U.S. could support only 4.8% of its population. In contrast to other indices of sustainability, a new index, the Emergy Sustainable Use Index (ESUI), which considers the benefits gained by the larger system compared to the potential for local environmental damage, increased 34% over the period.     

Assessing the risk posed by high-turbidity water to water supplies

The objective of this study is to assess the risk of insufficient water supply posed by high-turbidity water. Several phenomena can pose risks to the sufficiency of a water supply; this study concerns risks to water treatment plants from particular properties of rainfall and raw water turbidity. High-turbidity water can impede water treatment plant operations; rainfall properties can influence the degree of soil erosion. Thus, water turbidity relates to rainfall characteristics. Exceedance probabilities are presented for different rainfall intensities and turbidities of water. When the turbidity of raw water is higher than 5,000 NTU, it can cause operational problems for a water treatment plant. Calculations show that the turbidity of raw water at the Ban-Sin water treatment plant will be higher than 5,000 NTU if the rainfall intensity is larger than 165 mm/day. The exceedance probability of high turbidity (turbidity >5,000 NTU) in the Ban-Sin water treatment plant is larger than 10%. When any water treatment plant cannot work regularly, its ability to supply water to its customers is at risk.