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1.
Public Health Rep ; : 333549231222479, 2024 Jan 25.
Article in English | MEDLINE | ID: mdl-38268479

ABSTRACT

OBJECTIVE: Opioid use disorder (OUD) affects approximately 5.6 million people in the United States annually, yet rates of the use of effective medication for OUD (MOUD) treatment are low. We conducted an observational cohort study from August 2017 through May 2021, the MOUD Study, to better understand treatment engagement and factors that may influence treatment experiences and outcomes. In this article, we describe the study design, data collected, and treatment outcomes. METHODS: We recruited adult patients receiving OUD treatment at US outpatient facilities for the MOUD Study. We collected patient-level data at 5 time points (baseline to 18 months) via self-administered questionnaires and health record data. We collected facility-level data via questionnaires administered to facility directors at 2 time points. Across 16 states, 62 OUD treatment facilities participated, and 1974 patients enrolled in the study. We summarized descriptive data on the characteristics of patients and OUD treatment facilities and selected treatment outcomes. RESULTS: Approximately half of the 62 facilities were private, nonprofit organizations; 62% focused primarily on substance use treatment; and 20% also offered mental health services. Most participants were receiving methadone (61%) or buprenorphine (32%) and were predominately non-Hispanic White (68%), aged 25-44 years (62%), and female (54%). Compared with patient-reported estimates at baseline, 18-month estimates suggested that rates of abstinence increased (55% to 77%), and rates of opioid-related overdoses (7% to 2%), emergency department visits (9% to 4%), and arrests (15% to 7%) decreased. CONCLUSIONS: Our results demonstrated the benefits of treatment retention not only on abstinence from opioid use but also on other quality-of-life metrics, with data collected during an extended period. The MOUD Study produced rich, multilevel data that can lay the foundation for an evidence base to inform OUD treatment and support improvement of care and patient outcomes.

2.
Front Public Health ; 11: 1215925, 2023.
Article in English | MEDLINE | ID: mdl-38074746

ABSTRACT

Despite the investment of public resources to fight staggering suicide rates among veterans, we know little about how veterans and service members in crisis communicate suicidal ideations, and what interventions they are willing to receive. We aim to identify communication and suicide intervention preferences of veterans and service members in times of crisis. Descriptive statistics were used to explore veterans communication of suicidal ideations. While 89.9% of participants indicated they were willing to speak to someone when having thoughts of suicide, less than 26% of participants indicated they were willing to bring up their thoughts with a crisis line or veterans organization. Rather, they indicate that family members (62.2%) and military friends (51.1%) would be their primary outreach. Logistic regression was used to determine whether or not preferred interventions varied by participant demographic characteristics. While the majority of participants indicated they were willing to allow intervention (88.6%), no one method was accepted by the majority of the population. The most accepted means of communication was to proactively contact a friend or family member about general life struggles (32.6%) or suicide-specific concerns (27.5%). Many participants were open to receiving resources (42.0%), suicide-specific mental health treatment (36.3%), and some sort of lethal means safety intervention (19.1%-26.4%). The age, marital status, and veterans status of participants significantly impacted what interventions they were willing to allow. We discuss the implications of these findings and the need for evidence-based, multimodal interventions in order to assist veterans in need.


Subject(s)
Military Personnel , Suicide , Veterans , Humans , Veterans/psychology , Suicide/psychology , Suicidal Ideation , Violence
3.
Sci Total Environ ; 828: 154425, 2022 Jul 01.
Article in English | MEDLINE | ID: mdl-35276136

ABSTRACT

Forest regeneration has increased in many tropical abandoned lands and current restoration commitments in this region aim to restore over 1,400,000 km2 of degraded land by 2030. Although regenerating forests recover biomass, biodiversity, and processes with time, the recovery trajectories may be uncertain due to past disturbances. Currently, there is a lack of knowledge to sustain the effectiveness of passive regeneration for the recovery of riparian forests and the adjacent waterbodies in the tropics, which may compromise the outcomes of ongoing and future tropical riparian restoration programs. We evaluated the drivers of riparian forest structural recovery and how this relates to stream conditions in 12 abandoned pasturelands in eastern Brazilian Amazonia. These pasturelands range across regeneration age (pasture (PA) - 0 to 4 years; young regeneration (YR) - 8 to 12 years; old regeneration (OR) - 18 to 22 years) and years of past land-use (PA - 23.25 average years of past land-use, YR - 18.25, OR - 7). We compared the conditions of these sites to 4 reference sites with conserved forests (REF, >100 years), where there was no recorded pasture use in the past. Short-term responses of forests and streams to passive regeneration indicated high ecosystem resilience after low to intermediate past land-use intensity, reflected in the improvement of stream ecosystems. Such high resilience is possibly attributable to low- to intermediate-intensity pasture-related disturbances, remaining forest matrix, and residual structures (e.g. roots, sprouts, and in-stream wood) observed in the area. Our results suggest a recovery by 12 to 20 years for riparian forests of this region. However, areas degraded by intensive land-use apparently showed delayed recovery. We conclude that seizing resilience windows (defined here as the period when ecosystems retain high potential resilience) is essential to foster passive recovery of riparian forests and streams more cost-effectively in the tropics.


Subject(s)
Ecosystem , Water , Biodiversity , Forests , Rivers , Trees
5.
Genet Med ; 23(4): 758-766, 2021 04.
Article in English | MEDLINE | ID: mdl-33281187

ABSTRACT

PURPOSE: To estimate health and economic outcomes associated with newborn screening (NBS) for infantile-onset Pompe disease in the United States. METHODS: A decision analytic microsimulation model simulated health and economic outcomes of a birth cohort of 4 million children in the United States. Universal NBS and treatment was compared with clinical identification and treatment of infantile-onset Pompe disease. Main outcomes were projected cases identified, costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) over the life course. RESULTS: Universal NBS for Pompe disease and confirmatory testing was estimated to cost an additional $26 million annually. Additional medication costs associated with earlier treatment initiation were $181 million; however, $8 million in medical care costs for other services were averted due to delayed disease progression. Infants with screened and treated infantile-onset Pompe disease experienced an average lifetime increase of 11.66 QALYs compared with clinical detection. The ICER was $379,000/QALY from a societal perspective and $408,000/QALY from the health-care perspective. Results were sensitive to the cost of enzyme replacement therapy. CONCLUSION: Newborn screening for Pompe disease results in substantial health gains for individuals with infantile-onset Pompe disease, but with additional costs.


Subject(s)
Glycogen Storage Disease Type II , Child , Cost-Benefit Analysis , Enzyme Replacement Therapy , Glycogen Storage Disease Type II/diagnosis , Glycogen Storage Disease Type II/epidemiology , Glycogen Storage Disease Type II/genetics , Humans , Infant , Infant, Newborn , Neonatal Screening , Quality-Adjusted Life Years , United States/epidemiology
6.
Sci Total Environ ; 692: 1291-1303, 2019 Nov 20.
Article in English | MEDLINE | ID: mdl-31539961

ABSTRACT

Pesticides are important contributors to the global freshwater biodiversity crisis. Among pesticides, neonicotinoids are the best-selling class of agricultural insecticides and are suspected to represent significant risks to freshwater and terrestrial ecosystems worldwide. Despite growing recognition that neonicotinoid impacts may be modified by the presence of additional stressors, there is limited information about their interactions with other agricultural stressors in freshwater ecosystems. We conducted an outdoor pond-mesocosm experiment to investigate the individual and interactive effects of nutrients, fine sediment, and imidacloprid (a neonicotinoid insecticide) inputs on freshwater community structure (density, diversity, and composition of zooplankton and benthic invertebrates) and ecosystem functioning (ecosystem metabolism, primary production, and organic matter decomposition). We hypothesized antagonistic nutrient-imidacloprid, and synergistic sediment-imidacloprid interactions, affecting aquatic invertebrate communities. The three stressors had significant individual and interactive effects on pond ecosystems. The insecticide neutralized the positive effects of nutrient additions on benthic invertebrate richness and mitigated the negative effects of sediment on zooplankton communities (antagonistic interactions). Moreover, we observed compensatory responses of tolerant benthic invertebrates, which resulted in reversal interactions between sediment and imidacloprid. Furthermore, our observations suggest that imidacloprid has the potential to increase net ecosystem production at environmentally relevant concentrations. Our findings support the hypothesis that the impacts of imidacloprid may be modified by other agricultural stressors. This has important implications on a global scale, given the widespread use of these pesticides in intensive agricultural landscapes and the growing body of literature suggesting that traditional pesticide assessment frameworks, based on laboratory toxicity tests alone, may be insufficient to adequately predict effects to complex freshwater ecosystems.


Subject(s)
Aquatic Organisms/physiology , Ecosystem , Insecticides/toxicity , Neonicotinoids/toxicity , Water Pollutants, Chemical/toxicity , Agriculture , Animals , Biodiversity , Environmental Monitoring , Fresh Water , Insecticides/analysis , Invertebrates/physiology , Neonicotinoids/analysis , Nitrogen , Phosphorus , Water Pollutants, Chemical/analysis , Zooplankton
8.
Vaccine ; 36(43): 6416-6423, 2018 10 15.
Article in English | MEDLINE | ID: mdl-30236631

ABSTRACT

PURPOSE: Measure the preferences of decision makers and researchers associated with the Advisory Committee on Immunization Practices (ACIP) regarding the recommended format for presenting health economics studies to the ACIP. METHODS: We conducted key informant interviews and an online survey of current ACIP work group members, and current and previous ACIP voting members, liaison representatives, and ex-officio members to understand preferences for health economics presentations. These preferences included the presentation of results and sensitivity analyses, the role of health economics studies in decision making, and strategies to improve guidelines for presenting health economics studies. Best-worst scaling was used to measure the relative value of seven attributes of health economics presentations in vaccine decision making. RESULTS: The best-worst scaling survey had a response rate of 51% (n = 93). Results showed that summary results were the most important attribute for decision making (mean importance score: 0.69) and intermediate outcomes and disaggregated results were least important (mean importance score: -0.71). Respondents without previous health economics experience assigned sensitivity analysis lower importance and relationship of the results to other studies higher importance than the experienced group (sensitivity analysis scores: -0.15 vs. 0.15 respectively; relationship of the results: 0.13 vs. -0.12 respectively). Key informant interviews identified areas for improvement to include additional information on the quality of the analysis and increased role for liaisons familiar with health economics. CONCLUSION: Additional specificity in health economics presentations could allow for more effective presentations of evidence for vaccine decision making.


Subject(s)
Decision Making , Health Policy/economics , Immunization/economics , Research Personnel , Advisory Committees , Health Policy/legislation & jurisprudence , Humans , Immunization/legislation & jurisprudence , Immunization/standards , Immunization Programs/economics , Immunization Programs/legislation & jurisprudence , Immunization Programs/standards , Surveys and Questionnaires , Vaccines/economics , Vaccines/standards
9.
PLoS One ; 13(9): e0200180, 2018.
Article in English | MEDLINE | ID: mdl-30192753

ABSTRACT

Allochthonous detritus of terrestrial origin is one of the main energy sources in forested headwater streams, but its poor nutritional quality makes it difficult to use by heterotrophs. It has been suggested that algae growing on this detritus can enhance its nutritional quality and promote decomposition. So far, most evidence of this "priming effect" is derived from laboratory or mesocosm experiments, and its importance under natural conditions is unclear. We measured accrual of algae, phosphorus uptake capacity, and decomposition of poplar leaves in autumn in open- and closed-canopy reaches in 3 forest and 3 agricultural streams. Chlorophyll a abundance did not change significantly with stream type or with canopy cover, although in some agricultural streams it was higher in open than in closed canopy reaches. Canopy cover did not affect either phosphate uptake capacity or microbial decomposition. On the other hand, although there was no effect of canopy cover on invertebrate fragmentation rate, a significant interaction between canopy cover and stream suggests priming occurs at least in some streams. Overall, the results point to a weak or no priming effect of algae on litter decomposition in natural streams during autumn.


Subject(s)
Rhodophyta , Rivers , Seasons , Biological Assay
11.
Psychiatr Serv ; 69(9): 1032-1035, 2018 09 01.
Article in English | MEDLINE | ID: mdl-29852826

ABSTRACT

OBJECTIVE: Single-site studies indicate irregular hospital discharges are associated with elevated suicide risk. As part of ongoing analytics in the Veterans Affairs (VA) health system, the authors evaluated associations between irregular discharge and suicide over a 15-year period. METHODS: All inpatient discharges and discharge types from 2001 through 2014 were identified using VA administrative data. Mortality and cause-of-death data were drawn from comprehensive VA searches of the Centers for Disease Control and Prevention National Death Index. Suicide risk following regular versus irregular discharge was compared by using survival analysis and adjusting for age, gender, and VA facility. RESULTS: Among 5,051,051 discharges, 2.1% (103,995) were irregular. Adjusted suicide risk was higher following irregular discharge compared with regular discharge (hazard ratio [HR]=2.02, 95% confidence interval [CI]=1.78-2.29). Stratified analyses by unit type showed that the association was nonsignificant for psychiatric discharges but significant for general medical discharges (HR=3.01, CI=2.54-3.57). CONCLUSIONS: Patients were at increased suicide risk after irregular hospital discharges.


Subject(s)
Hospitals, Veterans/statistics & numerical data , Patient Discharge/statistics & numerical data , Suicide/statistics & numerical data , Cause of Death , Humans , Risk Factors , Survival Analysis , United States , Veterans/psychology
12.
J Anim Ecol ; 87(5): 1383-1394, 2018 09.
Article in English | MEDLINE | ID: mdl-29737519

ABSTRACT

Increasing habitat availability (i.e. habitat suitable for occupancy) is often assumed to elevate the abundance or production of mobile consumers; however, this relationship is often nonlinear (threshold or unimodal). Identifying the mechanisms underlying these nonlinearities is essential for predicting the ecological impacts of habitat change, yet the functional forms and ultimate causation of consumer-habitat relationships are often poorly understood. Nonlinear effects of habitat on animal abundance may manifest through physical constraints on foraging that restrict consumers from accessing their resources. Subsequent spatial incongruence between consumers and resources should lead to unimodal or saturating effects of habitat availability on consumer production if increasing the area of habitat suitable for consumer occupancy comes at the expense of habitats that generate resources. However, the shape of this relationship could be sensitive to cross-ecosystem prey subsidies, which may be unrelated to recipient habitat structure and result in more linear habitat effects on consumer production. We investigated habitat-production relationships for juveniles of stream-rearing Pacific salmon and trout (Oncorhynchus spp.), which typically forage in low-velocity pool habitats, while their prey (drifting benthic invertebrates) are produced upstream in high-velocity riffles. However, juvenile salmonids also consume subsidies of terrestrial invertebrates that may be independent of pool-riffle structure. We measured salmonid biomass production in 13 experimental enclosures each containing a downstream pool and upstream riffle, spanning a gradient of relative pool area (14%-80% pool). Increasing pool relative to riffle habitat area decreased prey abundance, leading to a nonlinear saturating effect on fish production. We then used bioenergetics model simulations to examine how the relationship between pool area and salmonid biomass is affected by varying levels of terrestrial subsidy. Simulations indicated that increasing terrestrial prey inputs linearized the effect of habitat availability on salmonid biomass, while decreasing terrestrial inputs exaggerated a "hump-shaped" effect. Our results imply that nonlinear effects of habitat availability on consumer production can arise from trade-offs between habitat suitable for consumer occupancy and habitat that generates prey. However, cross-ecosystem prey subsidies can effectively decouple this trade-off and modify consumer-habitat relationships in recipient systems.


Subject(s)
Ecosystem , Salmonidae , Animals , Forests , Invertebrates , Trout
13.
J Head Trauma Rehabil ; 33(2): E1-E6, 2018.
Article in English | MEDLINE | ID: mdl-28422894

ABSTRACT

OBJECTIVE: To explore the impact of problem-solving treatment (PST) for mild traumatic brain injury in active duty service members on the use of medical and psychological services. PARTICIPANTS: Service members who had a mild traumatic brain injury during their last deployment and enrolled in the CONcussion Treatment After Combat Trauma (CONTACT) study. DESIGN: Secondary analysis of a randomized clinical trial. Participants were assigned to telephone-based PST, or e-mailed or mailed education only over the course of 6 months. MAIN MEASURE: Self-reported health service utilization from months 4 through 6 and 10 through 12 after initiation of treatment, using the Cornell Service Index. RESULTS: In months 4 to 6, participants receiving PST had 6.17 times the odds of an emergency department visit or hospitalization than those receiving education only (95% confidence interval = 1.92-19.8; P value = .0023). These estimates, however, were not significant using a conservative Bonferroni correction (P value threshold < .0014). There were no other significant differences for other medical or psychological services received in months 4 to 6 or 10 to 12. CONCLUSION: Telephone-based PST was designed to complement clinical care, and this study showed that it may increase emergency department utilization. Future evaluations of PST with more accurate and complete measures of health service utilization are needed.


Subject(s)
Brain Concussion/psychology , Brain Concussion/therapy , Mental Health Services , Military Personnel , Problem Solving , Telemedicine , Adult , Emergency Service, Hospital , Female , Humans , Male , Middle Aged , Patient Acceptance of Health Care , Self Care , Telephone , Young Adult
14.
J Telemed Telecare ; 24(4): 282-289, 2018 May.
Article in English | MEDLINE | ID: mdl-28372513

ABSTRACT

Introduction Mild traumatic brain injury (mTBI) is an unfortunately common repercussion of military service in a combat zone. The CONTACT study tested an individualized telephone support intervention employing problem solving therapy (PST) for mTBI in soldiers recently returned from deployment. We sought to determine the cost effectiveness of this intervention from a military healthcare system perspective. Methods We conducted an intent-to-treat post-hoc analysis by building a decision analytic model that evaluated the choice between using PST or education only (EO). The model included cost-minimization and cost-effectiveness analyses. The incremental cost-effectiveness ratios (ICERs) were calculated as the differences in costs of PST versus EO relative to the differences in the outcomes of participants. Results The PST intervention resulted in an annual per-enrolee cost of $1027 (95% CI: $836 to $1248), while EO costs were $32 (95% CI: $25 to $39), resulting in a net incremental cost of $996 per enrolee (95% CI: $806 to $1,217). The ICERs were $68,658/QALY based on EQ-5D (95% CI: -$463,535 to $596,661) and $49,284/QALY based on SF-6D (95% CI: $26,971 to $159,309). Estimates of treatment costs in a real-world setting were accompanied by substantially lower ICERs that are within accepted thresholds for willingness-to-pay. Discussion Although the intervention had short-term benefits sufficient to yield acceptable ICERs, there was no long-term effect of PST over EO observed in the study. Consequently, we suggest that future studies examine the use of low-cost approaches, such as booster relapse-prevention calls, that may lead to a sustained treatment benefit for this population.


Subject(s)
Brain Concussion/therapy , Military Personnel , Problem Solving , Telephone , Cost-Benefit Analysis , Decision Making , Female , Humans , Quality-Adjusted Life Years , War Exposure
15.
Ecol Appl ; 28(1): 162-176, 2018 01.
Article in English | MEDLINE | ID: mdl-29024139

ABSTRACT

Chlorpyrifos is one of the most widely used agricultural insecticides in the world, but to date there is limited empirical information about its potential to interact with other common agricultural stressors. We conducted a 15-d, community-level, microcosm experiment evaluating individual and combined effects of chlorpyrifos, nutrient enrichment, and sedimentation on stream invertebrate communities (abundance, biomass, richness, size structure, composition) and ecosystem processes (primary productivity and leaf decomposition). We found that sedimentation was the most detrimental stressor, with significant negative impacts on most invertebrate community and ecosystem function variables. Even though chlorpyrifos did not cause significant invertebrate mortality in the microcosms, it still altered ecosystem function by lowering leaf decomposition rates, probably through sublethal inhibition of invertebrate shredders. Furthermore, we observed a significant reversal interaction between chlorpyrifos and sediment for small-sized invertebrates collected in gravel (abundance in sediment × insecticide microcosms was 2.4 times lower than predicted by additivity), as well as an antagonistic interaction with nutrients on invertebrate richness in the same microhabitat (richness in nutrient × insecticide microcosms was 1.6 times higher than predicted by additivity). Our results suggest that chlorpyrifos has the potential to alter freshwater ecosystem function and interact non-additively with other common agricultural stressors. These findings are in keeping with a growing body of research highlighting that multiple stressor interactions and ecosystem processes should be considered when evaluating the impacts of organic toxicants on freshwater ecosystems.


Subject(s)
Chlorpyrifos/toxicity , Ecosystem , Invertebrates , Rivers , Water Pollutants, Chemical/toxicity , Animals , British Columbia , Water Quality
16.
J Anim Ecol ; 85(5): 1136-46, 2016 Sep.
Article in English | MEDLINE | ID: mdl-26972564

ABSTRACT

Spatial resource subsidies can alter bottom-up and top-down forces of community regulation across ecosystem boundaries. Most subsidies are temporally variable, and recent theory has suggested that consumer-resource dynamics can be stabilized if the peak timing of a subsidy is desynchronized with that of prey productivity in the recipient ecosystem. However, magnitude of consumer responses per se could depend on the subsidy timing, which may be a critical component for community dynamics and ecosystem processes. The aim of this study was to test (i) whether a recipient consumer (cutthroat trout) responds differently to a resource subsidy occurring early in its growing season than to a subsidy occurring late in the season and, if this is the case, (ii) whether the timing-dependent consumer response has cascading effects on communities and ecosystem functions in streams. To test those hypotheses, we conducted a large-scale field experiment, in which we directly manipulated the timing of augmentation of the terrestrial invertebrates that enter stream (i.e. peak timing of June-August vs. August-October), keeping constant the total amounts of the invertebrates entered. We found large increases in the individual growth rate and population biomass of the cutthroat trout, in response to the early resource pulse, but not to the late pulse. This timing-dependent consumer response cascaded down to reduce benthic invertebrates and leaf breakdown rate, and increased water nutrient concentrations. Furthermore, the early resource pulse resulted in higher maturity rate of the cutthroat trout in the following spring, demonstrating the importance of the subsidy timing on long-term community dynamics via the consumer's numerical response. Our results emphasize the need to acknowledge timing-dependent consumer responses in understanding the effects of subsidies on communities and ecosystem processes. Elucidating the mechanisms by which consumers effectively exploit pulsed subsidies is an important avenue to better understand community dynamics in spatially coupled ecosystems.


Subject(s)
Biomass , Food Chain , Invertebrates/physiology , Oncorhynchus/growth & development , Rivers , Animals , Aquatic Organisms/physiology , British Columbia , Ecosystem , Seasons
18.
Psychiatr Serv ; 65(8): 1012-9, 2014 Aug 01.
Article in English | MEDLINE | ID: mdl-24788454

ABSTRACT

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: The study supports the business case for payers, particularly Medicaid, to invest in postdischarge follow-up calls.


Subject(s)
Continuity of Patient Care/economics , Cost-Benefit Analysis/economics , Health Care Costs/statistics & numerical data , Medicaid/economics , Patient Discharge/statistics & numerical data , Self-Injurious Behavior/economics , Suicidal Ideation , Humans , Self-Injurious Behavior/therapy , United States
19.
Glob Chang Biol ; 20(11): 3386-96, 2014 Nov.
Article in English | MEDLINE | ID: mdl-24753392

ABSTRACT

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.


Subject(s)
Biodiversity , Biomass , Invertebrates/physiology , Rivers , Animals , Anura/physiology , British Columbia , Carbon Dioxide/metabolism , Chlorophyll/metabolism , Chlorophyll A , Environmental Monitoring , Food Chain , Insecta/physiology
20.
Oecologia ; 175(1): 353-61, 2014 May.
Article in English | MEDLINE | ID: mdl-24399484

ABSTRACT

Climate change and invasive species have the potential to alter species diversity, creating novel species interactions. Interspecific competition and facilitation between predators may either enhance or dampen trophic cascades, ultimately influencing total predator effects on communities and biogeochemical cycling of ecosystems. However, previous studies have only investigated the effects of a single predator species on CO2 flux of aquatic ecosystems. In this study, we measured and compared the individual and joint effects of predatory damselfly larvae and diving beetles on total prey biomass, leaf litter processing, and dissolved CO2 concentrations of experimental bromeliad ecosystems. Damselfly larvae created strong trophic cascades that reduced CO2 concentrations by ~46% relative to no-predator treatments. Conversely, the effects of diving beetles on prey biomass, leaf litter processing, and dissolved CO2 were not statistically different to no-predator treatments. Relative to multiplicative null models, the presence of damselfly larvae and diving beetles together resulted in antagonistic relations that eliminated trophic cascades and top-down influences on CO2 concentrations. Furthermore, we showed that the antagonistic interactions between predators occurred due to a tactile response that culminated in competitive displacement of damselfly larvae. Our results demonstrate that predator identity and predator-predator interactions can influence CO2 concentrations of an aquatic ecosystem. We suggest that predator effects on CO2 fluxes may depend on the particular predator species removed or added to the ecosystem and their interactions with other predators.


Subject(s)
Carbon Dioxide/chemistry , Coleoptera , Ecosystem , Food Chain , Odonata , Predatory Behavior , Animals , Biomass , Bromeliaceae , Competitive Behavior , Fresh Water/chemistry , Larva , Models, Biological
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