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Transitions of care are critical for individuals at risk of suicide. This study determined the return on investment (ROI) for providing postdischarge follow-up calls to patients at risk of suicide who are discharged from a hospital or an emergency department.Claims data were from the 2006-2011 Truven Health MarketScan Commercial Claims and Encounters Database and Multi-State Medicaid Database. Cost estimates were from eight call centers that provide postdischarge follow-up calls. The ROI was estimated for the 30 days after discharge and was calculated from a payer's perspective (return gained for every $1 invested). One-way and probabilistic sensitivity analyses were used to examine the influence of variations of ROI model inputs.Under base case assumptions, the estimated ROI was $1.76 for commercial insurance and $2.43 for Medicaid for patients discharged from a hospital and $1.70 for commercial insurance and $2.05 for Medicaid for those discharged from an emergency department. Variation in the effect size of postdischarge contacts on reducing readmission had the largest effect on the ROI, producing a range from $0 to $4.11. The ROI would be greater than $1 for both payers and across both discharge settings as long as postdischarge contact could reduce readmission by at least 13.3%. Sensitivity analyses indicated a 77% probability (commercial) and an 88% probability (Medicaid) that the ROI would be greater than $1 among hospital discharges; the probabilities among emergency department discharges were 74% (commercial) and 82% (Medicaid).The study supports the business case for payers, particularly Medicaid, to invest in postdischarge follow-up calls.

The regulation of population processes for most organisms depends upon the strength and rate of feedback between resources and consumers. We conducted an experimental manipulation of leaf packs in stream channels, a patchy and ephemeral resource, which is consumed by a number of detritivorous invertebrates. We reduced the number of available food patches (red alder leaf packs) by half and then measured a variety of community responses, including emigration rate, aggregation on remaining food patches, decomposition rate of food patches, and species-specific differences in these responses. Replacement of removed leaf packs with polyester mimics resulted in no statistical difference in emigration rates or aggregation on remaining resources when compared to those removal channels without replacement. These results indicate that leaf packs are not used primarily for refuge. In the removal channels (including those with leaf pack mimics) emigration rate nearly doubled relative to control channels. Those invertebrates that did not emigrate from removal channels aggregated on remaining leaf packs, which led to more rapid decomposition of leaf packs relative to control channels. The increase in emigration rate only became apparent 2-3 days after the manipulation, presumably because animals colonized the remaining leaf packs and did not emigrate until food patch value per individual had been reduced by higher densities or due to increased discharge. Discharge through the channels increased slightly starting 3 days after the manipulation, resulting in increased emigration rates in all channels. Despite the increase in discharge, the effect of the manipulation remained strong. These results show that stream invertebrates colonizing leaf packs responded in predictable ways to a short-term reduction in food resources which would be adaptive in a system which is heterogeneous in space and time.

Elevated concentrations of inorganic sediment supply in streams may impair many biological functions. However, the contribution of exposure duration to the observed impacts has not been previously considered. We evaluated the effects of sediment pulse duration using 14 streamside flow-through experimental channels, each of which contained a naturally colonised invertebrate assemblage and 10 rainbow trout (Oncorhynchus mykiss) fry. Channels were exposed to fine sediment pulses of constant concentration but varied pulse duration (ranging from 0 to 6 h) every second day over 19 days. Total abundance of benthic invertebrate and family richness declined as sediment pulse duration increased. Invertebrate drift total abundance increased as pulse duration increased; however, family richness of drift decreased. Trout length and mass gain over the 19-day period was negatively correlated with pulse duration. Path analysis suggests that the direct effects of fine sediment on trout (impaired vision leading to reduced prey capture success and (or) increased metabolic costs from physiological stress) are more important to trout growth than indirect effects (decreased drift and benthic invertebrate richness and drift abundance).

Reference-condition models for the Fraser River catchment were developed using samples collected during the autumn of 1994, 1995, and 1996. The goal of this study was to examine applicability to the reference-condition models of samples collected in other seasons and the effect of taxonomic resolution (genus and family) on model sensitivity to seasonal variation in the benthic invertebrate assemblage. Samples from eight streams representing interior, coastal, and large-river habitats were collected in spring, summer, autumn, and winter of 1995 and in spring of 1996. The benthic invertebrate assemblage changed seasonally such that the models could not be used for seasons other than autumn. The models were equally sensitive to seasonal variation when genus-level or family-level data were used. We recommend that test samples (i.e., samples collected from disturbed sites and meant for comparison with the reference database) be collected either during the autumn or over multiple sampling dates to reduce the possibility that seasonal shifts or stochastic events will lead to erroneous conclusions about the state of a test site.

Objectives of this study were to determine whether (1) stream algal biomass was nutrient limited, (2) stream herbivores could reduce algal biomass at different levels of productivity, and (3) a large vertebrate herbivore (Ascaphus truei) affected the abundance of insect grazers under different nutrient supply regimes. To address these objectives, we conducted a 2 3 2 factorial experiment to examine the effects of varying phosphate supply on periphyton biomass, insect grazers, and a tadpole grazer in 12 streamside experimental channels in southwestern Canada. We manipulated presence of tailed frog tadpoles (A. truei Stejneger) and varied nutrient levels using nutrient-diffusing pellets. We monitored periphyton biomass as ash-free dry mass (AFDM), insect grazer abundance, dissolved nutrients (NO 3 2 N and PO4 2 P) in water, and tadpole growth rates over 38 days. Dissolved nitrate and phosphate concentrations were temporally variable, and there were no statistical differences among treatments, but dissolved phosphate levels were 1.7 times greater in nutrientenriched channels (3.2 m gL 21) than in unenriched channels (1.7 m gL 21). Periphyton AFDM was significantly higher in channels with added nutrients, as was abundance of insect grazers, primarily Chironomidae and Ephemeroptera. Tadpoles in channels with nutrients had growth rates approximately four times higher than tadpoles in controls. Insect grazer abundance in channels with and without added nutrients was lower in the presence of tadpoles, and this reduction was greater in channels with nutrients. In contrast to other studies that have examined the impact of vertebrate herbivores on periphyton, tadpoles had no measurable effect on periphyton biomass. These data indicate periphyton and grazers were resource limited, as added nutrients increased periphyton biomass, as well as abundance (insect grazers) and biomass (tailed frog tadpoles) of herbivores.

The timing of life cycles, including growth rates, was determined for eight common species of detritivorous insects in a second-order stream in southwestern British Columbia, Canada. Six of the species (Zapada cinctipes, Z. haysi, Malenka californica, M. cornuta, Capnia sp., and Lepidostoma roafi) had simple, univoltine life cycles. The leuctrid stonefly Despaxia augusta has a 2-year life cycle, with an apparent egg diapause of about 6 months. The chironomid Brillia retifinis produced at least three generations per year. The major growth periods for the set of species considered here span the entire year. Adults of several species exhibited seasonal declines in size at emergence, but one species had larger adults as the emergence period proceeded. Closely related taxa had more similar life cycle timing than more distantly related species suggesting a degree of phylogenetic constraint in phenology of their life cycles. The influence of the timing of leaf drop on timing of life cycles for these animals does not fit with proposed scenarios based on fast and slow leaf processing rates.

Fish communities were sampled at 14 sites along the lower 120 km of the Fraser River, British Columbia by beach seine four times in 1972–1973 and three times in 1993–1994. Of the 37 species collected, peamouth chub, largescale sucker, starry flounder, and northern squawfish were predominant in either density or biomass. Densities and biomass of most species and all fish combined were higher in 1993–1994. Strong rank correlations of species abundance or biomass indicated that the overall fish community structure was very similar in both periods. At smaller spatial scales (reaches of 2–3 sites) and shorter time scales (by season), less than half the comparisons showed any significant correlation indicating changes in community composition. Largescale sucker, one of the largest contributors to biomass in both periods, showed decreased abundance, i.e., lower density, lower biomass, and large differences in the size-frequency distribution, specifically very low representation of small size classes. Other species, especially small-bodied forms, generally increased in numbers. Despite large changes in the lower Fraser River ecosystem in the past 21 years, the overall fish community has shown remarkably little change over that interval.

SUMMARY 1. The spatial distribution of macroinvertebrate species was examined in relation to hydraulic and sedimentary conditions in a large gravel-bed river, the Fraser River, Canada. Mean annual discharge in the Fraser River is 2900 m 3 s 1 and annual flood discharge, due to snowmelt in May and June, averages 8760 m 3 s 1 . 2. Invertebrates were sampled from four water depths (0.2, 0.5, 1.5, 3.0 m) at various levels of discharge that together captured the spatial and temporal variability of the physical habitat. Several hydraulic (near-bed shear velocity, Boundary Reynolds number, turbulence intensity, depth-averaged velocity, Froude number, Reynolds number) and substratum variables (mean grain size, Trask’s sorting coefficient, Nikuradse’s roughness, percentage of fine sediment, and Shields entrainment function) were measured for each sample of macroinvertebrates. Concentrations of fine and coarse particulate organic matter were also assessed. 3. The physical habitat was characterized by a major gradient of hydraulic conditions that corresponded positively with increasing water depth and accounted for 52% of the total variation in the habitat data. Substratum conditions and the concentration of organic matter explained 24% of the total variation in the habitat data. 4. The distribution of invertebrates was correlated significantly with hydraulic variables and suggests that hydraulic conditions represent a major physical gradient along which the benthic community is organized. The distribution of organic matter and substratum texture were also important for some species. The spatial distribution of most species reflected morphological and trophic suitability to particular habitat conditions. 5. Hydraulic stress associated with foraging and maintaining position, as well as organic matter retention in coarse substrata, are probable mechanisms affecting the spatial distribution of macroinvertebrates.

To characterize organic matter dynamics in headwater streams of southwestern British Columbia, Canada, we monitored epilithic biomass and fluvial transport of organic matter. Fluvial organic matter was collected once to twice monthly from 7 streams: samples were processed as coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and dissolved organic matter (DOM). Epilithon was collected monthly from unglazed, ceramic tiles in 12 stream reaches and measured for ash-free dry mass (AFDM) and chlorophyll-a. CPOM and FPOM concentrations were higher during the wet season (1 October-30 April) than the dry season (1 May-30 September). Averaged across sites, CPOM and FPOM concentrations were positively related to mean daily discharge averaged over the 7 days before sample collection. In contrast, discharge and DOM concentration were inversely related. DOM concentration was positively correlated to chlorophyll-a accrual. Seasonal variation in epilithic chlorophyll-a and AFDM accumulation was high. AFDM accumulation rates ranged from a low in January 1997 of 0.31 to a high of 3.6 μg cm -2 d -1 in May 1997. As with organic matter in stream water, discharge influenced the temporal dynamics of epilithic biomass accumulation; there was a negative correlation between discharge and epilithic AFDM.

Metal contamination is one of the most widespread impacts on surface waters. Experimental flumes receiving water and aquatic invertebrates from an undisturbed, forested stream were used to determine the impact of metals in a low-conductivity stream. The experimental flumes were exposed to a gradient of doses maintaining a constant ratio of metals (1995: Cu, Zn, Mn, and Pb; 1996: Cu and Zn) for 6 d. Benthos and emigration were sampled from each of the 16 troughs. The overall densities of benthos declined, but not significantly, as the dose of metals increased. On the basis of the slopes of the concentration-response curve, Baetis, Ameletus, and Paraleptophlebia were the most sensitive taxa present. Other taxa (e.g., Nemouridae and Oligochaeta) were mildly affected by high metal concentrations. Chironomidae showed no significant decrease in densities with increasing dose. Chironomids made up >80% of the benthos and is the primary reason for no significant dose effect on overall densities. No treatment effect was observed on either algal standing crop or bacterial respiration rates. The invertebrate genera most affected by exposure to metals in this study were also absent or rare in nearby urban streams with high metal concentrations.

In southwestern British Columbia (BC, Canada) and within a relatively small geographic area, lotic environments range from streams in coastal rainforests, to streams in arid continental grasslands, to very large rivers. Little is known about the invertebrate communities in large rivers in general, or in the streams of continental BC. The purpose of this study was to determine whether the benthic invertebrate community structure changes spatially between small coastal and small interior streams; between small streams versus large rivers; and whether changes in the benthic community are related to the environmental conditions. Kicknet samples and environmental data were collected from three coastal streams, three continental streams and two large rivers (discharge of 781 and 3620 m3/s, respectively). The large river sites had low invertebrate abundance, species richness and diversity, relative to the small streams. The coastal streams had the highest species richness and the continental streams had the highest invertebrate abundance. A number of taxa were specific to each class of stream. Invertebrate abundance decreased with river size, and increased with elevation, pH, conductivity, alkalinity, NO2NO3-N, total Kejldahl nitrogen and percent carbon in suspended solids.

Discussion 1699 Spatial patterns are often present in results of ecological surveys (Legendre and Troussellier 1988; Legendre and Fortin 1989; Legendre 1993). When surveys span broad geographic areas, sites near one another often have similar levels of species abundance or biomass as a result of similar geologic, climatic, or biotic factors (Legendre and Fortin 1989). This positive autocorrelation at “small” spatial scales means that nearby sites should not be treated as independent replicates in classical statistical analyses (Legendre 1993). Under these conditions, statistical tests are too liberal and prone to type I errors. Despite knowing these pitfalls, many fisheries researchers continue to use classical statistical analyses and ignore the potential influence that autocorrelation could have on interpretations of broad geographic scale patterns (see Hinch et al. 1994) or temporal patterns (Pyper and Peterman 1998) of fish attributes. In a recent issue of the Canadian Journal of Fisheries and Aquatic Sciences, Randall et al. (1995) used data from entire fish taxocenes for 31 lake and 62 river sites distributed throughout the world to suggest that relative to lakes, rivers had considerably greater fish production, density, biomass, and P/B and considerably lower individual fish mass. Although these results were compelling, we are concerned with the robustness of their conclusions. Because many of Randall et al.’s study sites were clustered within specific geographic locales (clusters of streams in Poland (14), England (nine), Malaysia (seven), and New Zealand (three) and clusters of lakes in Canada (12), Scandinavia (seven), and Russia (five)), we suspected that positive small-scale spatial autocorrelation exists in their data. If it does exist, then their statistical approach could be biased towards detecting differences between rivers and lakes (i.e., type I errors). The purpose of this comment is to reevaluate the conclusions of Randall et al. in light of spatial autocorrelation. We accomplish this by examining their data for spatial patterns and then using two complementary analytical approaches for comparing fish attributes between rivers and lakes that are appropriate for spatially autocorrelated data. We have other concerns about their study, in particular, their sampling design is not globally well balanced; streams were clustered in northern Europe and the south Pacific, whereas no lakes were from these areas but were instead largely from Canada, Scandinavia, and Russia. There are no analytical approaches, including ones we suggest, that will remedy all biases in interpretation that may be caused by this sampling design. Further, some of the variables used by Randall et al. (e.g., production, biomass, weight, and P/B) are not independent of one another (an issue that has been discussed by Jackson et al. (1994)), yet were treated as independent variables for analytical and interpretative purposes. Moreover, field sampling in rivers and lakes requires different methods with different efficiencies that could bias their contrasts. However, we will not deal here with the sampling biases and independence issues listed above. In our comment, we focus exclusively on the effects of spatial autocorrelation because there still seems to be a general misunderstanding or ignorance among aquatic ecologists about statistical approaches that are appropriate for broad geographic scale survey data. This is despite the publication over the past 10 years of papers that detail the potential pitfalls of spatial autocorrelation in ecological studies (e.g., Legendre and Troussellier 1988; Legendre and Fortin 1989; Legendre 1993; Hinch et al. 1994; Dunham and Rieman 1999). Spatial autocorrelation may be the result of important underlying environmental gradients and it is thus critical to consider such patterns explicitly. However, frequently, one is unaware of such gradients or the scale at which they influence patterns in nature, and autocorrelation analysis can at least expose the presence of such patterns. We are concerned here primarily with the biases that autocorrelation may impose on statistical inferences and not whether important gradients may be ignored as a consequence.

Benthic macroinvertebrates shifted from deep water to shallow water of the shore zone during annual flooding of a large, gravel-bed river. The shore zone is seasonally inundated during flooding for up to 4 mo of the year, and is a geomorphic feature of many large rivers in northern latitudes with limited floodplain habitat. We collected samples of invertebrates along with measures of several hydraulic and sedimentary variables 5 times through the flood cycle from 4 fixed water depths; stations shifted laterally over a distance of 30 m between baseflow and peak flow. In deep water (1.5 and 3.0 m), shear velocity and substrate mobility increased as a result of flooding. At shallow depths (0.2 and 0.5 m) within the shore zone, stable substrate and low hydraulic stress remained throughout the flood cycle, providing flow refugia to benthic invertebrates. Invertebrate density and species richness were similar during months on the rising limb of the hydrograph while the wetted area of the channel markedly increa...

Hodgson et al. [1] propose to represent the ‘resilience’ of natural systems bivariately, using ‘resistance’ and ‘recovery’ as quantifiable components. There has been a recent interest in simultaneously measuring two or more components of change in ecological units following disturbance [2,3]. However, it is of foremost importance to discern which components are being measured in these studies, given the previously unstandardized uses of ‘resistance’ and ‘resilience’ [4]. Their multiple meanings can cause terminological confusion in usage.

Additions of inorganic N and P to replicated stream mesocosms were used to test the hypothesis that production of the benthic food web in the flow-controlled Nechako River, B.C., was N and P limited. N, P, and N + P additions were contrasted with controls to determine the responses of periphyton and macroinvertebrates over a 33-day period in late spring. Periphyton accrual under N + P addition was greater than two times that of the controls, and N alone produced a moderate increase. Periphyton showed relatively little response to P addition compared with controls. Macroinvertebrates, especially orthocladiine midges and mayflies, increased in density under N or N + P additions, in contrast with P additions and controls. Increased emergence rates of adult aquatic insects from the mesocosms were consistent with increases observed in benthic invertebrates. The results showed nutrient limitation of benthic productivity and that algal and benthic invertebrate responses were closely coupled. N was most limiting, but with additions of inorganic N as low as 10 μg·L -1 , P became limiting. The benthic invertebrates that increased most in abundance corresponded to the predominant prey in chinook salmon (Oncorhynchus tshawytscha ) fry diets at the time of the experiment. Resume : Nous avons ajoute du N et du P inorganiques dans une serie de mesocosmes lotiques pour valider l'hypothese selon laquelle la production de la chaine alimentaire benthique dans la riviere Nechako, un cours d'eau de Colombie-Britannique a debit controle, etait limitee en N et en P. Les effets des ajouts de N, de P et de N + P ont ete compares a des valeurs temoins afin de determiner les reponses du periphyton et des macroinvertebres sur une periode de 33 jours de la fin du printemps. L'accroissement du periphyton pour un ajout de N + P etait plus du double que pour les temoins, et l'ajout de N seul a entraine une augmentation moderee. Par contre, l'effet d'un ajout de P a eu relativement peu d'effet sur le periphyton. La densite des macroinvertebres, particulierement les chironomides orthocladiines et les ephemeropteres, a augmente en cas d'ajout de N ou de N + P, mais pas en cas d'ajout de P ni dans les milieux temoins. Les taux accrus d'emergence observes chez les insectes aquatiques adultes des mesocosmes etaient conformes aux augmentations observees chez les invertebres benthiques. Les resultats ont montre que la production benthique etait limitee par les elements nutritifs et que les reactions des algues et des invertebres benthiques etaient etroitement liees. C'est l'azote qui etait l'element le plus limitant; pour des ajouts de N inorganique de seulement 10 μg·L -1 , P est devenu limitant. Les invertebres benthiques dont l'abondance a le plus augmente correspondaient aux principales proies des alevins du saumon quinnat (Oncorhynchus tshawytscha ) au moment de l'experience. (Traduit par la Redaction)

Evidence varies on how subsidies affect trophic cascades within recipient food webs. This could be due to complex nonlinearities being masked by single-level manipulations (presence/absence) of subsidies in past studies. We predicted that trophic cascade strength would increase nonlinearly across a gradient of subsidies. We set out to reveal these complex, nonlinear relationships through manipulating a quantitative gradient of detrital subsidies to lake benthic food webs along with the presence/absence of trout. Contrary to our prediction, we found that trophic cascades only occurred at low subsidy levels, disappearing as subsidies increased. This threshold in trophic cascade strength may be due to an increase in intermediate predators in the absence of top predators, as well as changes in the proportion of armored vs. un-armored primary consumers. Future studies on the effect of subsidies on trophic cascade strength need to incorporate naturally occurring gradients to reveal the complex direct and indirect interactions within food webs.

Concern over accelerating rates of species invasions and losses have initiated investigations into how local and global changes to predator abundance mediate trophic cascades that influence CO2 fluxes of aquatic ecosystems. However, to date, no studies have investigated how species additions or losses at other consumer trophic levels influence the CO2 flux of aquatic ecosystems. In this study, we added a large predatory stonefly, detritivorous stonefly, or grazer tadpole to experimental stream food webs and over a 70-day period quantified their effects on community composition, leaf litter decomposition, chlorophyll-a concentrations, and stream CO2 emissions. In general, streams where the large grazer or large detritivore were added showed no change in total invertebrate biomass, leaf litter loss, chlorophyll-a concentrations, or stream CO2 emissions compared with controls; although we did observe a spike in CO2 emissions in the large grazer treatment following a substantial reduction in chlorophyll-a concentrations on day 28. However, the large grazer and large detritivore altered the community composition of streams by reducing the densities of other grazer and detritivore taxa, respectively, compared with controls. Conversely, the addition of the large predator created trophic cascades that reduced total invertebrate biomass and increased primary producer biomass. The cascading effects of the predator additions on the food web ultimately led to decreased CO2 emissions from stream channels by up to 95%. Our results suggest that stream ecosystem processes were more influenced by changes in large predator abundance than large grazer or detritivore abundance, because of a lack of functionally similar large predators. Our study demonstrates that the presence/absence of species with unique functional roles may have consequences for the exchange of CO2 between the ecosystem and the atmosphere.

Assessing the condition of an ecosystem to ascertain its ‘health’ presupposes that we can diagnose pathological states in system measures. Frequently this means comparing current conditions to reference states, either historical or other sites, which also exhibit some natural range of variation. In the Fraser River, a 9th order river on the west coast of Canada, and one of the most productive salmon rivers in the world. we have studied assemblages of fish and benthos to assess ecosystem health. The biggest challenge to using species composition and abundance measures as indicators of system condition is the absence of appropriate reference conditions in many instances. There are few unperturbed rivers of large size in western North America, and indeed in much of the world, with which to compare the Fraser River or any other large river ecosystem. Multiple insults from point and non-point sources make it difficult to isolate factors from natural longitudinal changes in terms of their effects on river biota. Potential solutions include analysis of fragmentary historical data, making comparisons with other large rivers, and conducting extensive surveys within the basin to account for spatial gradients. An absolute diagnosis of ecosystem health of large rivers in natural science terms is unlikely, and otherwise will depend on relative changes through time assuming these can be isolated from natural variation and local effects. Definition of health for large, riverine ecosystems remains largely a case of expert opinion and weight of evidence rather than a testable hypothesis.

Benthic insects, sediments and sculpins were collected from the Fraser River, British Columbia, in winter 1993 to assess concentrations of chlorinated organic contaminants. Concentrations of most chlorinated dioxins/furans and phenolics (phenols, guaiacols and catechols) analyzed were below detection limits. Concentrations of 2,3,7,8-tetrachlorodibenzofuran were 2.5 to 6.5 pg/g wet mass in four different taxonomic groupings of aquatic insects. Other chlorinated dioxins/furans detected were heptachlorodioxins and octachlorodioxin in sediments and detritivorous benthic insects, tetrachlorodibenzofurans (not including 2,3,7,8-TCDF) in insects, and pentachlorodibenzofurans. Some chlorinated phenolics, e.g., 3,4,5-trichloroguaiacol, were found in most taxa. Highest concentrations of phenolics were measured in prickly sculpins (Cottus asper) about an order of magnitude higher than in benthos, but all concentrations were less than 6 ng/g wet mass. Concentrations of the chlorinated organics measured were in the same range as those for juvenile chinook salmon collected at the same sites.

Incomplete knowledge of the ecological functions of small streams and their riparian zones, particularly their roles in larger watershed and landscape contexts, contributes to confusion and debate about the levels of riparian vegetation retention required along small streams for the purpose of protecting aquatic ecosystems, riparian wildlife, and water quality. As a consequence, there are marked differences in riparian forestry practices and management among jurisdictions throughout North America. To aid in resolving these issues, a symposium on small streams and their riparian zones was held at The University of British Columbia from 19 to 21 February 2002, which brought together scientists, managers, and practitioners and provided a forum for the presentation and discussion of emerging research results. This special issue includes a selection of papers presented at that symposium as well as one solicited paper.

International audience; Inorganic fine sediments are easily carried into streams and rivers from disturbed land. These sediments can affect the stream biota, including detritivorous invertebrates (shredders) and impair ecosystem functions, such as leaf litter decomposition. We hypothesized that fine sediment (kaolin) deposited on leaves would reduce or suppress fungal development, reducing decomposition rates of leaves. Moreover, we predicted that shredders would act as ecosystem engineers by perturbing sediment deposition, reducing its impact on decomposition and fungi. We used a fully crossed experimental design of sediment addition (control, 400 mg L-1) and shredders (none, Gammarus, Potamophylax) in laboratory aquaria. Leaf mass loss, sus- pended solids, microbial respiration, fungal biomass and spore production were measured. Sediment addition had no significant effects on the leaf mass remaining nor on shredders' consumption rates. However, sediment slightly reduced fungal assemblage richness and the sporulation rate of three fungal species. The presence of shredders sub- stantially increased the resuspension of fine sediments ([300%),resultinginhighersuspendedloads.However,the action of shredders did not have a significant effect on fungal biomass nor on leaf mass loss. Even if shredders did not enhance fungal colonisation, they affected the settle- ment of fine sediment, serving as allogenic engineers. Our study suggests that concentrations of fine sediment of 400 mg L-1 with short exposure times (192 h) can have some effect on leaf decomposition.

With predicted decreases in genetic diversity and greater genetic differentiation at range peripheries relative to their cores, it can be difficult to distinguish between the roles of current disturbance versus historic processes in shaping contemporary genetic patterns. To address this problem, we test for differences in historic demography and landscape genetic structure of coastal giant salamanders (Dicamptodon tenebrosus) in two core regions (Washington State, United States) versus the species' northern peripheral region (British Columbia, Canada) where the species is listed as threatened. Coalescent-based demographic simulations were consistent with a pattern of post-glacial range expansion, with both ancestral and current estimates of effective population size being much larger within the core region relative to the periphery. However, contrary to predictions of recent human-induced population decline in the less genetically diverse peripheral region, there was no genetic signature of population size change. Effects of current demographic processes on genetic structure were evident using a resistance-based landscape genetics approach. Among core populations, genetic structure was best explained by length of the growing season and isolation by resistance (i.e. a 'flat' landscape), but at the periphery, topography (slope and elevation) had the greatest influence on genetic structure. Although reduced genetic variation at the range periphery of D. tenebrosus appears to be largely the result of biogeographical history rather than recent impacts, our analyses suggest that inherent landscape features act to alter dispersal pathways uniquely in different parts of the species' geographic range, with implications for habitat management.

Lack of midwives in rural and remote areas of Ghana is a national concern as the country attempts to reach targets set by Millennium Development Goals to reduce maternal and child mortality by 2015.To understand factors influencing third-year Ghanaian midwifery students' willingness to work in rural areas.Two of the largest midwifery schools in Ghana.Third-year midwifery students (n=238) about to graduate and enter the workforce.Based on focus group discussions with midwifery students, we refined a computerized survey to assess students' preferences for rural posting after graduation. We then administered this survey to midwifery students in Ghana. We used Pearson's chi-squared to compare the top reasons for choosing job location between those students likely and not likely to work in a rural area. Logistic regression models were used to calculate the odds ratios.An opportunity to gain additional education was the most important factor for the midwifery students in deciding where they would eventually work (72%). Poor quality of clinical facilities (26%), poor quality of education for children (19%), and lack of social amenities (17%) were major deterrents to working in rural communities. For student midwives willing to work in rural areas the top reasons cited included to serve humanity (74%), and increased opportunities to gain clinical experience (62%). More experiences overall with rural communities resulted in greater odds of being willing to work in a rural area. Being born in a rural area (OR: 1.95, 95% CI: 0.736, 5.16) and living in a rural area after age 5 for one-year or more (OR: 1.52, CI: 0.857, 2.70). An exception to this was midwifery students who performed health work for six weeks or more in a rural area during training. These students were found to have 0.83 lower odds of willingness to work in a rural area (95% CI: 0.449, 1.55).By better understanding the motivating factors for rural healthcare workers, specific policy interventions can be established to improve the distribution of midwives thereby decreasing the burden of maternal and infant mortality.

Commercial formulations of the insecticidal bacterium Bacillus thuringiensis var. kurstaki (Btk) are frequently sprayed over bodies of water. The hypothesis that Btk poses a threat to stream communities was tested using streamside, flow-through mesocosms which received water and invertebrate colonists from a second-order stream in southwestern British Columbia; low (50 BIU/ha) and high (≥ 5000 BIU/ha) treatment levels were contrasted with controls. There were no significant differences in the density or composition of benthos sampled 7 d after Btk application. The densities were highest in the high-dose mesocosms. There were no significant differences in emergence rate of adults due to treatment. During the 2.5-h treatment, there were marginally elevated drift rates of the mayfly Baetis when exposed to the solution, but these differences were negated during the remainder of the 24-h period. Leaf packs lost significantly more mass in controls than in high-dose mesocosms, but there were no significant differences in the numbers of macro-invertebrates on those leaf packs. There was no evidence that addition of Btk to stream mesocosms created adverse effects for this benthic community, even at > 100 times expected exposure rates.

Cross-boundary flows of energy and nutrients link biodiversity and functioning in adjacent ecosystems. The composition of forest tree species can affect the structure and functioning of stream ecosystems due to physical and chemical attributes, as well as changes in terrestrial resource subsidies. We examined how variation in riparian canopy composition (coniferous, deciduous, mixed) affects adjacent trophic levels (invertebrate and microbial consumers) and decomposition of organic matter in small, coastal rainforest streams in southwestern British Columbia. Breakdown rates of higher-quality red alder (Alnus rubra) litter were faster in streams with a greater percentage of deciduous than coniferous riparian canopy, whereas breakdown rates of lower-quality western hemlock (Tsuga heterophylla) litter were independent of riparian forest composition. When invertebrates were excluded using fine mesh, breakdown rates of both litter species were an order of magnitude less and were not significantly affected by riparian forest composition. Stream invertebrate and microbial communities were similar among riparian forest composition, with most variation attributed to leaf litter species. Invertebrate taxa richness and shredder biomass were higher in A. rubra litter; however, taxa evenness was greatest for T. heterophylla litter and both litter species in coniferous streams. Microbial community diversity (determined from terminal restriction fragment length polymorphisms) was unaffected by riparian forest or litter species. Fungal allele richness was higher than bacterial allele richness, and microbial communities associated with lower-quality T. heterophylla litter had higher diversity (allele uniqueness and richness) than those associated with higher-quality A. rubra litter. Percent variation in breakdown rates was mostly attributed to riparian forest composition in the presence of invertebrates and microbes; however, stream consumer biodiversity at adjacent trophic levels did not explain these patterns. Riparian and stream ecosystems and their biotic communities are linked through exchange and decomposition of detrital resources, and we provide evidence that riparian forest composition affects stream ecosystem catabolism despite similarities in microbial and invertebrate communities.

The umbrella-species concept, which suggests that conservation strategies designed for one species may benefit co-occurring species, has been promoted as a framework for conservation planning. Nevertheless, there has been considerable variation in the outcome of empirical tests of this concept that has led researchers to question its value, so we used data from 15 published studies in a meta-analysis to evaluate whether conservation of putative umbrella species also conserves co-occurring species. We tested the effectiveness of putative umbrella species categorized by taxonomic group, taxonomic similarity to co-occurring species, body size, generality of resource use, and trophic level to evaluate criteria proposed to guide the selection of umbrella species. We compared species richness and number of individuals (by species and higher taxonomic group) between sites with and without putative umbrella species to test whether more co-occurring species were present in greater abundances when the area or resource needs of umbrella species were met. Species richness and abundance of co-occurring species were consistently higher in sites where umbrella species were present than where they were not and for conservation schemes with avian than with mammalian umbrella species. There were no differences in species richness or species abundance with resource generalist or specialist umbrella species or based on taxonomic similarity of umbrella and co-occurring species. Taxonomic group abundance was higher in across-taxonomic umbrella species schemes than when umbrella species were of the same taxon as co-occurring species. Co-occurring species had similar, or higher, species richness with small-bodied umbrella species relative to larger-bodied umbrella species. The only significant difference among umbrella species categorized by trophic level was that species richness was higher with omnivorous than it was with carnivorous avian umbrella species. Our results suggest there is merit to the umbrella-species concept for conservation, but they do not support the use of the criteria we used to identify umbrella species.

The Coastal Giant Salamander (Dicamptodon tenebrosus) is classified as threatened at the northern periphery of its range in British Columbia (BC), Canada, primarily due to forestry practices and habitat fragmentation. Characterising dispersal behaviour and population connectivity is therefore a priority for this region, while genetic differentiation in core versus peripheral locations remains unstudied in this wide-ranging species. We present seven new polymorphic microsatellite markers for use in population genetic analyses of D. tenebrosus. We examine locus characteristics and genetic variation in 12 streams at the species' northern range limit in BC, and within two regions representing sub-peripheral (North Cascades) and core localities (South Cascades) in Washington State, United States. In BC, the number of alleles per locus ranged from 2-5 and observed heterozygosity ranged from 0.044-0.825. Genetic differentiation was highest between BC and the South Cascades, and intermediate between BC and the North Cascades. Across loci, mean allelic richness was similar across regions, while private allelic richness was highest in the core locality (corrected for sample size). These new microsatellite loci will be a valuable addition to existing markers for detailed landscape and population genetic analyses of D. tenebrosus across its range.

Historically, forested riparian buffers have been created to provide protection for aquatic organisms and aquatic ecosystem functions. Increasingly, new and existing riparian buffers are being used also to meet terrestrial conservation requirements. To test the effectiveness of riparian buffers for conserving terrestrial fauna, we conducted a meta-analysis using published data from 397 comparisons of species abundance in riparian buffers and unharvested (reference) riparian sites. The response of terrestrial species to riparian buffers was not consistent between taxonomic groups; bird and arthropod abundances were significantly greater in buffers relative to unharvested areas, whereas amphibian abundance decreased. Edge-preferring species were more abundant in buffer sites than reference sites, whereas species associated with interior habitat were not significantly different in abundance. The degree of buffer effect on animal abundance was unrelated to buffer width; wider buffers did not result in greater similarity between reference and buffer sites. However, responses to buffer treatment were more variable in buffers

An on-site continuous-flow trough mesocosm was used to examine changes in the composition and abundance of periphytic algae and benthic invertebrates from additions of a solution of treated acid mine drainage (AMD). Five control and five treatment troughs supported an assemblage of periphyton and invertebrates that colonized from water withdrawn from Foxy Creek, a stream that receives limed AMD from the Equity Silver Mine, central British Columbia, Canada. A water intake for the mesocosm was located upstream of the AMD discharge. The treated AMD was delivered to the apparatus through a pipeline laid in a canal that carried the AMD to Foxy Creek. After three weeks of colonization in the troughs, additions of one part AMD to 10 parts Foxy Creek water was delivered to the treatment troughs and continued for three weeks. Analyses of variance of measurements of abundance and biomass indexes contained high power values and indicated that the AMD addition did not significantly change the algal and insect composition and abundance. Advantages and disadvantages of the mesocosm with regard to the relative sensitivity of the measured parameters for use in examining effects of the AMD additions are discussed. The conclusion was that quantitative on-site experimentation using the mesocosm apparatus is a powerful approach in setting guidelines for AMD discharge mainly due to its capability of integrating ecosystem processes in experiments where hypothesis testing is possible.

SUMMARY 1. Leaf packs in streams may serve as food and substrate to many macroinvertebrates, but the relative importance of these two functions has not been disentangled. To test the hypothesis that leaf packs are colonized primarily for their food value rather than as microhabitat, the colonization of leaf packs of red alder and of polyester cloth in a natural stream was compared. 2. Species of shredders showed large differences in the colonization of the two types of leaf pack with almost no use of artificial leaf packs. Non-shredders were also more abundant on natural leaf packs, however, they colonized artificial leaf packs six to eighty times proportionally more than shredders. 3. The effect of different leaf types was virtually eliminated for non-shredders when the amount of fine parriculate detritus (food for many non-shredders) trapped in the leaf pack was added to the analysis as a covariate. Therefore, to non-shredders, leaf types differed only in the retention of fine particulate organic matter. 4. Comparisons of the use of both kinds of leaf packs in riffles versus pools revealed that significantly fewer animals colonized pool leaf packs. 5. These results suggest that food value, and not microhabitat, is the primary determinant of leaf pack use for most shredders and non-shredders.

The dynamics of coarse particulate organic matter (CPOM) were studied for 2 yr in three second-order streams in the Coast Range of British Columbia. Estimates of direct litterfall ranged from 201 to 481 g ash-free dry mass∙m−2∙yr−1. The magnitude of deciduous leaf litter input was similar among streams. Input of conifer needles to a stream with an old-growth canopy was higher than in two streams which drained second-growth forests. There was over a 60-fold seasonal change in deciduous leaf standing stock, but woody debris and total CPOM showed less seasonal variation. Decomposition of alder leaf packs in two of the streams showed a large temperature-dependent component and significant differences between streams, with the more retentive stream having lower rates of decomposition. From estimates of input and decay rates, models of leaf loss were made to predict benthic standing stocks of deciduous leaf litter. Comparisons of the model predictions with actual measures indicate that 70–94% of leaf material was unaccounted for and presumably lost from the study reach by export, floodplain deposition, and burial. The seasonal changes in standing stock of CPOM emphasize the variation in food supply potentially available to detritivorous stream organisms.

Many species of detritivorous invertebrates in small streams depend almost entirely on inputs of leaf litter for their nutritional requirements, however the concentration of this resource varies considerably seasonally. An experiment designed to test the hy- pothesis that productivity of coarse particle detritus feeders (shredders) is seasonally food limited was performed using replicate streamside channels that received one of three input rates of whole leaf detritus (rates equal to those naturally falling into montane streams, and two levels of increased inputs). Seven of the nine common shredder species attained significantly higher adult mass, higher densities, or both when food was supplemented. Larval densities of Malenka spp. and Brillia retifinis were significantly higher when additional food was added. Brillia retifinis densities were more than 10 x greater in high food additions than in the "natural" treatment; B. retifinis apparently fills a role as a fugitive in this system and is better able to track shifts in resource abundance by virtue of its short generation time. Zapada cinctipes and Z. haysi were more dense in high and intermediate food input treatments during the last half of the summer. Other taxa had nonsignificant trends to higher densities when extra food was provided. Most of the change in benthic densities can be attributed to decreased rates of emigration with increased food supply. Six of the eight taxa for which adult mass at emergence was measured were significantly more massive (4-46%) when food was added. Both sexes exhibited this increase in mass, but females gained proportionally more in most species. There were no detectable changes in the timing of adult emergence due to food manipulations. The biomass of most taxa increased in proportion to the overall increase in biomass of the common coarse-detritus consumers. The main exceptions to that pattern were a disproportionate increase in the percentage of the biomass represented by Brillia retifinis and a decrease in the representation of Zapada cinctipes. The responses of this community to food supplementation demonstrate food limitation of detritivores. The exponential increase in benthic biomass under food addition shows the scope for productivity if food were not limiting. These coexisting species benefitted from enhanced food supply on a spatial scale that is relevant for population level processes. The large seasonal variation in resource abundance under natural conditions creates bot- tlenecks during periods of low food supply, which constrain subsequent production even during periods when food is abundant.

To evaluate the common assumption in stream ecosystem theory that fine-particle feeders can indirectly benefit from coarse-particle detritus consumed by detritivores, we manipulated whole-leaf detritus in replicated experimental stream channels. Elevated input rates of detritus resulted in significantly higher densities of collectors and moderate but nonsignificantly higher densities of predators. When collectors were analyzed as filterers and gatherers separately, there were significantly higher densities of both groups at a high loading rate of leaves. The net rates of colonization for each trophic group did not differ significantly with respect to treatment, which suggests that the increased densities of collectors observed under high leaf input rates were due to increased survival of larvae. Density of no single taxon increased significantly in response to coarse particulate organic matter inputs; rather, most species showed moderate increases. Species richness showed no treatment effect. Increases in collector density may result indirectly from increased fine particulate organic matter production due to feeding by shredders. Predaceous species which responded were small taxa and were probably predators on collectors. These effects were observed over a period of less than 5 mo and demonstrate the potential strength of the interactions.

Summary 1. The passive or active movement of organisms between habitat patches plays important roles in achieving ecosystem resilience to disturbance and long-term control of population levels. However, causal mechanisms of disturbance-induced movements of mobile biota across heterogeneous habitat patches at a relatively short time-scale are little understood. 2. We experimentally tested the effects of food resource values on macroinvertebrate colonization of hydraulic refugia from spates in a second-order creek. Experimental cages were colonized by macroinvertebrates with combinations of resource types (natural or polyester leaves), and extent of exposure to stream flow (exposed to or sheltered from current); one half of each set was collected before and after a spate. This experiment was repeated over three spates of varying magnitude and seasonal contexts. 3. Pre-spate colonization was consistently greater for the cages with natural leaves relative to artificial leaves regardless of the extent of flow exposure. Two autumn spates with relatively low and stable antecedent flow conditions caused large movements of organic matter and macroinvertebrates across the stream, showing community-level accumulations into hydraulically sheltered patches independent of food treatment. The smallest spate with high and variable antecedent flows during winter resulted in negligible responses, which we interpret to be a result of depletion of easily transportable organic matter and organisms. 4. Two detritivorous taxa, the mayfly Paraleptophlebia spp. and stonefly Despaxia augusta (Banks) were the most responsive to autumn spates, and had disproportionately higher colonization rates of cages when provided with natural leaves during the largest autumn spate. Preferential settlement in food-enriched hydraulic refugia was attributable to taxon-specific mobility related to efficient acquisition of detritus resource, whose availability varies spatially and temporally. 5. Our findings suggest (1) detritivorous macroinvertebrate colonization of hydraulic refugia can be influenced by hydraulic controls as well as food resource value, and (2) pre-spate environmental conditions in terms of resource distribution and availability may pre-condition organisms’ susceptibility to spates and also affect refugium usage, at least in food-limited, detritus-based stream systems.

The Fraser River, with its headwaters in the Rocky Mountains, flows across the dry Fraser Plateau through coastal mountain ranges to the Pacific Ocean. This chapter describes the main-stem Fraser River, as well as eight major tributaries that illustrate the wide range of geologic, climatic, and biological diversity in the basin. The basin is contained within two physiographic provinces. A portion of the Fraser drains from the Rocky Mountains in Canada province in the east and a portion drains from the coast mountains of British Columbia and Southeast Alaska province. The climate of the basin ranges from subarid to arid and mild in southern lower valleys to humid and cold at higher elevations in the northern reaches, reflecting the interaction of the dominant westerly circulation with the mountain ranges. The basin also shows great biological diversity in both flora and fauna. Because the various tributaries across the basin experience a great range of topographic features and precipitation patterns, they are highly variable in their monthly stream flows. The two major activities in the basin are logging and mining. Effects from tree removal and pulp and paper mills have been of most concern.

The Pacific coast rivers of Canada and Alaska cover the region extending from British Columbia's north coast to north of the Aleutian Islands, and have a latitudinal range from 54°N to 64°N. The region includes parts of three physiographic provinces—Yukon Basin, South Central Alaska, and Coast Mountains of British Columbia and Alaska. The mountains show signs of glacial scouring. Given the northern location and the extensive area of high mountains in this region, a large portion of the annual precipitation falls as snow. This chapter discusses rivers that represent two freshwater ecoregions: the North Pacific Coastal and the Yukon. A unique aspect of the glacial influence on some of these rivers is the periodic occurrence of outburst floods. All rivers sustain important spawning and rearing areas for Pacific salmon and steelhead. A few aquatic species in this region of North America are at risk. Major current and future threats to rivers within this region are impoundments to generate hydroelectric power, contamination from mining effluents and sediments, timber harvest, and introduced (nonnative) species.

We conducted an artificial pond experiment to test hypotheses about the effects of competition and non-lethal predator cues on metamorphic characteristics of sympatric Oregon spotted frogs (Rana pretiosa) and red-legged frogs (Rana aurora) in southwestern British Columbia. Tadpoles were exposed to the presence or absence of one another, two density levels and to the presence or absence of predacious odonate larvae (Aeshna palmata) isolated in enclosures. In the artificial pond study, R. aurora were significantly larger at metamorphosis (12%) and exhibited only slightly longer larval periods when exposed to Aeshna. In the presence of R. pretiosa, they significantly decreased time to metamorphosis, and were significantly larger at metamorphosis (12%) than those reared alone. Rana pretiosa in treatments with R. aurora were somewhat larger at metamorphosis when a non-lethal predator was present, and in treatments where R. pretiosa were alone with a predator tadpole mass at metamorphosis was smaller than those in the absence of Aeshna, but these results were not statistically significant. Both species reduced activity and moved away from the predator in the presence of an enclosed dragonfly larva in the laboratory. Most tadpole mesocosm experiments have found that the trade-off between size and timing of metamorphosis is extremely important to amphibians, but we suggest that the trade-off discussed in traditional amphibian models may not apply to species like R. pretiosa that are exposed to the same gape-limited predators upon reaching metamorphosis.

Artificial light at night is gaining attention for its potential to alter ecosystems. Although terrestrial ecologists have observed that artificial light at night may disrupt migrations, feeding, and other important ecological functions, we know comparatively little about the role artificial light might play in disrupting freshwater and riparian ecosystems. We identify and discuss four future research domains that artificial light may influence in freshwater and associated terrestrial ecosystems, with an emphasis on running waters: (1) dispersal, (2) population genetics and evolution, (3) ecosystem functioning, and (4) potential interactions with other stressors. We suggest that future experimental and modeling studies should focus on the effects of different spectral emissions by different light sources on freshwater organisms, the spatial and temporal scale over which artificial light acts, and the magnitude of change in light at night across the landscape relative to the distribution of running and standing waters. Improved knowledge about the effects of artificial light on freshwater ecosystems will inform policy decisions about changes to artificial light spectral emissions and distributions.

The life cycle of the dragonfly Cordulegaster dorsalis was studied over one year by systematic sampling of larvae in three intermittent headwater streams in southwestern British Columbia. We determined that larvae normally take three years to reach maturity, emerging throughout July and August. There is limited evidence suggesting a split cohort development, with early emergence after two years. Additionally, we tested whether larval instars were distributed randomly or if they occupied different sediment microhabitats. Smaller animals tend to be associated with smaller grained organic sediments, although there was high variation between the streams.

Analysis of sperm has been investigated as a possible method to examine the toxicity of environmental contaminants. The amphibian sperm inhibition toxicological test (ASITT) method examines the effects of contaminants on Xenopus laevis (African clawed frog) sperm motility and path trajectories. As part of a preliminary validation of the method, the effects of increasing divalent metal ion, zinc (Zn2+), on X. laevis sperm motility were examined. We hypothesized that Zn2+ concentration would have significant inhibitory effects on percent sperm motility, velocities, and trajectories. The Zn2+ was added to a control solution in concentrations from 0 to 1,417 microg/L. Sperm cells were videotaped at 30 frames per second under x 400 microscope, and percent motility was recorded and paths were mapped by marking the change in position of the sperm head over a period of 1 s. Sperm motility was categorized as progressive, hyperactivated, idle, or nonmotile, and velocities and trajectories were calculated on the basis of x,y coordinates. Increasing Zn2+ concentrations caused a significant exponential decay in percent total motility and progressive motility. Straight-line velocity increased with increasing Zn2+ concentrations. Overall, results suggest that Zn2+ may be interfering with cellular processes, such as cellular respiration, flagellar bending, or ion exchange, thereby inhibiting sperm motility.

Failure to understand subtle behavioral mechanisms can lead to mischaracterization of interactions within food webs. Laboratory studies indicating increased prey capture by fish when predatory invertebrates are present suggested a field experiment to evaluate the effect of stonefly removal on growth rate of fish. Individually marked juvenile cutthroat trout (Oncorynchus clarki) were introduced into replicate experimental stream channels beside a coastal Pacific rainforest stream. In stream channels with large perlid stoneflies (Doroneuria and Calineuria sp.) trout gained mass, whereas in channels without stoneflies trout lost body mass. There was no significant effect of stoneflies on trout mortality over the month-long experiments. Although total predator number and biomass were higher in channels with stoneflies (trout and stonefly biomass combined), trout apparently gained more from the way prey behavior was altered by the presence of stoneflies, than they lost from any effects of competition for common prey resources. The presence of significant facilitation amongst predators complicates our view of trophic structuring in stream communities, requiring that such non-intuitive interactions be more explicitly considered both by modelers and experimentalists seeking to evaluate the role of predators in these and in other communities.

Using litter bag experiments in the Fraser River estuary in British Columbia, we tested for differences in the relative decomposition rates between leaves of purple loosestrife (Lythrum salicaria), an introduced exotic and a native sedge (Carex lyngbyei). The difference in the mean decay rate coefficient for the two species was significantly defferent (p