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Climate change projections indicate increased precipitation in northern Europe, leading to increased inflow of allochthonous organic matter to aquatic systems. The food web responses are poorly known, and may differ depending on the trophic structure. We performed an experimental mesocosm study where effects of labile dissolved organic carbon (DOC) on two different pelagic food webs were investigated, one having zooplankton as highest trophic level and the other with planktivorous fish as top consumer. In both food webs, DOC caused higher bacterial production and lower food web efficiency, i.e., energy transfer efficiency from the base to the top of the food web. However, the top-level response to DOC addition differed in the zooplankton and the fish systems. The zooplankton production increased due to efficient channeling of energy via both the bacterial and the phytoplankton pathway, while the fish production decreased due to channeling of energy mainly via the longer and less efficient bacterial pathway. We conclude that the added DOC either acted as a subsidy by increasing the production of the top trophic level (mesozooplankton), or as a sink causing decreased top consumer production (planktivorous fish). [ABSTRACT FROM AUTHOR]

Predicted increases in runoff of terrestrial dissolved organic matter (DOM) and sea surface temperatures implicate substantial changes in energy fluxes of coastal marine ecosystems. Despite marine bacteria being critical drivers of marine carbon cycling, knowledge of compositional responses within bacterioplankton communities to such disturbances is strongly limited. Using 16S rRNA gene pyrosequencing, we examined bacterioplankton population dynamics in Baltic Sea mesocosms with treatments combining terrestrial DOM enrichment and increased temperature. Among the 200 most abundant taxa, 62 % either increased or decreased in relative abundance under changed environmental conditions. For example, SAR11 and SAR86 populations proliferated in combined increased terrestrial DOM/temperature mesocosms, while the hgcI and CL500-29 clades (Actinobacteria) decreased in the same mesocosms. Bacteroidetes increased in both control mesocosms and in the combined increased terrestrial DOM/temperature mesocosms. These results indicate considerable and differential responses among distinct bacterial populations to combined climate change effects, emphasizing the potential of such effects to induce shifts in ecosystem function and carbon cycling in the future Baltic Sea.

Background: Cotrimoxazole prophylaxis prolongs survival and prevents opportunistic infections, malaria, and diarrhea in persons infected with human immunodeficiency virus (HIV). Many countries recommend that individuals taking antiretroviral therapy (ART) discontinue cotrimoxazole when CD4 counts are >200 cells/μL. However, this practice has not been evaluated in sub-Saharan Africa., Methods: Patients in the Home-Based AIDS Care program in eastern Uganda initiated ART if they had a CD4 cell count ≤250 cells/μL or World Health Organization stage III or IV HIV disease. In the program's fourth year, patients with CD4 counts >200 cells/μL were randomly assigned, by household, to continue or discontinue cotrimoxazole. Consenting participants were followed for episodes of malaria and diarrhea., Results: At randomization, 836 eligible patients had been receiving ART for a mean of 3.7 years, with a median CD4 count of 489 cells/μL; 94% had a viral load <400 copies/mL. Among those continuing (n = 452) vs discontinuing (n = 384) cotrimoxazole, 0.4 vs 12.2%, respectively, had at least 1 episode of malaria (P < .001), and 14% vs 25%, respectively, had at least 1 episode of diarrhea (P < .001). Compared to those remaining on cotrimoxazole, patients who discontinued had a relative risk of malaria of 32.5 (95% confidence interval [CI], 8.6-275.0; P < .001) and of diarrhea of 1.8 (95% CI, 1.3-2.4; P < .001)., Conclusions: HIV-infected adults on ART with CD4 counts >200 cells/μL who live in a malaria-endemic area of sub-Saharan Africa and who abruptly discontinue cotrimoxazole prophylaxis have an increased incidence of malaria and diarrhea compared with those who continue prophylaxis. Clinical Trials Registration. NCT00119093.

Background: Up to 20% of people initiating antiretroviral therapy (ART) in sub-Saharan Africa die during the first year of treatment. Understanding the clinical conditions associated with mortality could potentially lead to effective interventions to prevent these deaths., Methods: We examined data from participants aged ≥18 years in the Home-Based AIDS Care project in Tororo, Uganda, to describe mortality over time and to determine clinical conditions associated with death. Survival analysis was used to examine variables associated with mortality at baseline and during follow-up., Results: A total of 112 (9.4%) deaths occurred in 1132 subjects (73% women) during a median of 3.0 years of ART. Mortality was 15.9 per 100 person-years during the first 3 months and declined to 0.3 per 100 person-years beyond 24 months after ART initiation. Tuberculosis (TB) was the most common condition associated with death (21% of deaths), followed by Candida disease (15%). In 43% of deaths, no specific clinical diagnosis was identified. Deaths within 3 months after ART initiation were associated with World Health Organization clinical stage III or IV at baseline, diagnosis of TB at baseline, a diagnosis of a non-TB opportunistic infection in follow-up and a body mass index ≤17 kg/m² during follow-up. Mortality after 3 months of ART was associated with CD4 cell counts <200 cells per microliter, a diagnosis of TB or other opportunistic infection, adherence to therapy <95%, and low hemoglobin levels during follow-up., Conclusion: Potentially remediable conditions and preventable infections were associated with mortality while receiving ART in Uganda.