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Interactions between dissolved organic carbon (DOC) and bacterioplankton were examined during a diatom and Phaeocystis bloom in the Santa Barbara Channel (SBC) over five days following an upwelling event. The SBC was heterogeneous in physical state (recently upwelled vs. more stratified), nutrient concentration, and productivity, encompassing phytoplankton physiological states from a healthy bloom through the onset of silicon stress. DOC accumulated in the upper 10 m over the bloom, with compositional shifts indicated by chromophoric dissolved organic matter (CDOM) parameters. DOC bioavailability and bacterial growth and community composition responses were assessed with dilution batch-culture bioassays. In these experiments, bacterioplankton DOC usage increased over the bloom, with uptake of 1.5-5.3 μmol L−1 over three days, 1.5-5.7 μmol L−1 over one week, and 1.8-10.8 μmol L−1 over 10 weeks. DOC removal was poorly correlated with traditional proxies of bioavailability (chlorophyll a concentration, elemental ratios of dissolved organic matter, and CDOM). However, bacterial growth efficiency (BGE) was strongly related to in situ conditions, with higher BGEs on fresher, late-bloom DOC. After 10 weeks, 1.6-15.7 μmol L−1 of the DOC that accumulated during the bloom remained unutilized in the bioassays, with higher concentrations of persistent DOC in experiments from senescent bloom physiological states, supporting the putative relationship between phytoplankton blooms and seasonal DOC accumulation in the field. These experiments demonstrate that DOC released by the plankton community during a bloom fuels increased short-term and long-term bacterial activity, enhances presumed trophic transfer via increased BGEs, and leads to the accumulation of persistent, potentially exportable, DOC. © 2015 Association for the Sciences of Limnology and Oceanography [ABSTRACT FROM AUTHOR]

Objectives: Extensive discussion with renal patients about treatment intensity is not systematically integrated into their care and often occurs during an acute hospitalization. We conducted a "test-of-change" pi lot study to assess the utility of providing an upstream discussion in the ambulatory setting as an additional nephrology consult to assist patients with chronic kidney disease considering treatment choices. Methods: We randomly assigned patients with Stage 4 or Stage 5 chronic kidney disease who had not yet begun renal dialysis to 1 of 2 groups. The test group received the additional nephrology consult and met with an interdisciplinary team composed of a nephrologist, social worker, and clinical ethicist, and the control group did not. Qualitative data were collected in 2012 and 2013 via oral questionnaire. Both groups received a 6-month follow-up assessment. Results: Patients who received the nephrology consult reported that they experienced help in forming a treatment plan, felt well understood, and had the opportunity to thoroughly discuss questions. The controls had a 26% increased probability of beginning dialysis and had a statistically significant increase in dialysis and clinic visits (p < 0.10 and p < 0.05). Controls also were likelier than the test group to be admitted to the hospital (0.5 vs 0.2 admissions per patient in the test group), spend more days hospitalized (2.8 vs 0.5 bed days per patient), and visit the emergency room (0.73 vs 0.66 visits per patient) and clinic (6.6 vs 3.6 visits per patient). Conclusions: An additional nephrology consultation proved helpful both qualitatively and quantitatively. [ABSTRACT FROM AUTHOR]

Eutrophication remains one of the foremost impacts of industrialization and population expansion on aquatic ecosystems worldwide. Selecting metrics for assessing the manner in which communities and biogeochemical processes respond to nutrient fertilization is an ongoing management challenge critical both for detecting changes and for monitoring recovery of impaired environments. A key limitation to the selection of response variables is the lack of consistent evaluation of metrics under the same conditions in multiple systems across ecoregions. Here we report the results of nutrient‐diffusing agar fertilization experiments conducted simultaneously in 30 streams in two distinct ecoregions of California, USA: the mountainous Sierra Nevada and the coastal chaparral of Santa Barbara county. In each experiment we evaluated algal community shifts across five nutrient delivery rates using multiple response variables at the ecosystem process (respiration and primary production), community (biomass and diversity metrics), functional group (nitrogen fixing, growth form, nutrient adaptation), and taxonomic group (indicator species, genera, families) levels of ecological organization. We used mixed‐effect general linear models to quantify the magnitude, sensitivity, and consistency of responses among streams within and across ecoregions to provide an objective assessment of the potential for each variable to describe and detect significant changes in algal community characteristics. Our results indicate that ecosystem‐ and community‐level variables showed significant and consistent nutrient responses among diverse streams and across the two ecoregions, while indicator taxa and functional groups were less likely to respond consistently to nutrient enrichment. We discuss the relevance of our findings to the ongoing development of monitoring and bioassessment strategies for aquatic eutrophication. [ABSTRACT FROM AUTHOR]

To examine the influence of landscape characteristics and landscape position on aquatic biogeochemistry, we sampled a total of 76 lakes within 14 different lake-chains spanning the latitudinal extent of the high-elevation Sierra Nevada (California). We measured water chemistry, dissolved organic matter (DOM), nutrients, and biotic variables in study catchments that encompassed representative ranges of area (3-22 km), elevation (2,200-3,700 m.a.s.l), elevation change (50-700 m), and average slope (13°-26°). Hierarchical models were used to account for variability in biogeochemistry because they explicitly maintain the framework of lakes within individual lake-chains while accounting for variation among lake-chains. Unconditional means models, where lake-chain was a random effect, revealed significant differences among lake-chains for nearly all biogeochemical variables. Models explained 42-95% of this variability, with the majority of the variation (70%) explained by the among lake-chain component. To explore the amount of additional variation explained by lake landscape position, we added lake network number (LNN) to models. LNN explained a significant amount of additional variation (7% average) in 8 of 23 biogeochemical parameters. However, it explained more variability within individual lake-chains (75%), where among lake-chain differences did not obscure patterns. Patterns of increase with LNN were found for dissolved organic carbon and nitrogen, fluorescence of DOM, alkalinity, and bacterioplankton abundance, whereas nitrate and nitrogen to phosphorus nutrient ratios decreased. LNN explained variation because it served as a proxy for underlying catchment characteristics that changed consistently along downstream flow paths. To characterize the amount of variation explained by catchment characteristics alone, we fit a third model that included lake-chain as a random effect and landscape or lake morphometry attributes as fixed effects. Catchment characteristics explained about as much additional variation (6%) as LNN, but for substantially more biogeochemical parameters (18 out of 23). The catchment characteristics most predictive of biogeochemistry were land-cover factors delineating alpine and subalpine zones (elevation, slope, or proportions of rock or shrub cover). In general, catchment characteristics were stronger predictors of biogeochemistry than characteristics of lake morphometry, emphasizing the relative importance of landscape processes in snowmelt-dominated lake ecosystems. [ABSTRACT FROM AUTHOR]

The idea that productivity regulates species diversity is deeply ingrained in the field of ecology. Yet, over the past few decades, an increasing number of experiments have shown that species diversity controls, rather than simply responds to, biomass production. These contrasting perspectives have led to a seeming paradox: Is diversity the cause or the consequence of biological production? Here we present empirical evidence for the multivariate productivity--diversity (MPD) hypothesis, which argues that differing perspectives on productivity--diversity relationships can be resolved by recognizing that historical research has focused on how resource supply regulates both the productivity and richness of local competitors, whereas more recent studies have focused on how the richness of a colonist pool regulates the efficiency by which resources are captured and converted into new tissue. The MPD hypothesis predicts that three pathways operate concurrently to generate productivity--diversity relationships in nature: (1) resource supply directly limits the standing biomass and/or rate of new production by primary producers, (2) producer biomass is directly influenced by the richness of species that locally compete for resources, and (3) resource supply rate indirectly affects producer biomass by influencing the fraction of species from a colonist pool that locally coexist. To examine whether this set of pathways explains covariation between productivity and diversity in natural streams, we used nutrient-diffusing agar "patches" to manipulate resource supply rates in 20 streams throughout the Sierra Nevada mountain range, California, USA. We then measured the fraction of periphyton species from the stream colonist pool co-occurring on each nutrient patch, as well as the standing biomass and rates of primary production. Natural patterns of covariation agreed with predictions of the MPD hypothesis. Algal biomass was an increasing function of nutrient supply, and an increasing function of local richness. The fraction of species from the colonist pool found co- occurring on a patch was a concave-down function of nutrient supply, causing nutrients to indirectly affect biomass via control over local richness. These results suggest that the MPD hypothesis is a viable explanation of patterns of diversity and productivity in natural stream ecosystems, and that it has potential to merge the historical view that productivity drives diversity with a parallel view that diversity drives productivity. [ABSTRACT FROM AUTHOR]

Final results from a longitudinal investigation of the effectiveness of cognitive-behavioral treatment with sexual offenders are presented. The study was a randomized clinical trial that compared the reoffense rates of offenders treated in an inpatient relapse prevention (RP) program with the rates of offenders in two (untreated) prison control groups. No significant differences were found among the three groups in their rates of sexual or violent reoffending over an 8-year follow-up period. This null result was found for both rapists and child molesters, and was confirmed in analyses using time to reoffense as the outcome and those controlling for static risk differences across the groups. Closer examination of the RP group's performance revealed that individuals who met the program's treatment goals had lower reoffense rates than those who did not. Although our results do not generally support the efficacy of the RP model, they do suggest a number of ways in which this kind of treatment program can be improved. This study also emphasizes the importance of including appropriate control groups in treatment outcome research. Additional controlled investigations are needed to address the many questions that remain about when and how treatment works for sexual offenders. [ABSTRACT FROM AUTHOR]

We examined bacterioplankton community composition (BCC; using polymerase chain reaction-based phylogenetic fingerprinting) and the composition of dissolved organic matter (DOM; using scanning fluorometry) within lake chains in high-elevation catchments of the Sierra Nevada, California. We compared temporal BCC dynamics in two connected cirque lakes and their inlets and found that lake : inlet community similarity of both lakes declined with increasing residence time because of seasonal snowpack melting. However, for over 3 yr the headwater lake remained distinct from its inlet even during peak snowmelt (residence time <5 d), whereas the downstream lake was consistently similar to both its inlet and the upstream lake. We subsequently sampled 17 lake chains (4-8 lakes each) throughout the Sierra Nevada longitudinally to examine how landscape position and catchment characteristics influenced the similarity in BCC and DOM among lakes and their connecting streams. Headwater lakes were significantly less similar to their inlet streams than were downstream lakes. BCC was heterogeneous throughout each catchment, but headwater inlet BCC was consistently distinct from all downstream samples. In contrast, DOM exhibited a trend of increasing homogeneity as water moved downstream: upstream and downstream waters were distinct but without clear headwater outliers. The similarity in BCC and DOM between any two lakes within a chain declined with geographic distance. Our results illustrate the contrasting roles of environmental selection and dispersal in structuring bacterioplankton communities, supporting both strong within-lake environmental selection for communities distinct from terrigenous inputs and a weaker effect of geographic dispersal differentiating communities among lakes linked by advective flow. [ABSTRACT FROM AUTHOR]

Many eukaryotic communities exhibit predictable seasonality in species composition, but such phenological patterns are not well-documented in bacterial communities. This study quantified seasonal variation in the community composition of bacterioplankton in a high-elevation lake in the Sierra Nevada of California over a 3-year period of 2004-2006. Bacterioplankton exhibited consistent phenological patterns, with distinct, interannually recurring community types characteristic of the spring snowmelt, ice-off and fall-overturn periods in the lake. Thermal stratification was associated with the emergence of specific communities each summer and increased community heterogeneity throughout the water column. Two key environmental variables modulated by regional meteorologic variation, lake residence time and thermal stability, predicted the timing of occurrence of community types each year with 75% accuracy, and each corresponded with different aspects of variation in community composition (orthogonal ordination axes). Seasonal variation in dissolved organic matter source was characterized fluorometrically in 2005 and was highly correlated with overall variation in bacterial community structure (r(Mantel)=0.75, P<0.001) and with the relative contributions of specific phylotypes within the Cyanobacteria, Actinobacteria and beta-Proteobacteria. The seasonal dynamics of bacterial clades (tracked through coupling of randomized clone sequence libraries to restriction fragment length polymorphism fingerprints) matched previous results from alpine lakes and were variously related to solute inputs, thermal stability and temperature. Taken together, these results describe a phenology of high-elevation bacterioplankton communities linked to climate-driven physical and chemical lake characteristics already known to regulate eukaryotic plankton community structure.