Factors influencing submerged macrophyte presence in fresh and brackish eutrophic waters and their impact on carbon emissions

In agricultural landscapes of North-Western Europe, the majority of water bodies do not meet the targets set by the European Water Framework Directive due to a lack of submerged macrophytes and associated biodiversity. These eutrophic waters can also be a substantial source of methane (CH4) and carbon dioxide (CO2) to the atmosphere. Here we present a two-year field experiment on the island of Goeree-Overflakkee (southwest Netherlands), conducted in six drainage ditches varying in salinity, where we monitored four permanent plots per ditch and varied the presence of both fish and macrophytes. We aimed to: 1) investigate factors limiting submerged macrophyte growth, focussing on exclusion of grazing pressure and bioturbation by fish; and 2) quantify the CO2 and CH4 emission under these conditions. Even in highly eutrophic, semi turbid ditches with fluctuating salinity levels and sulphide presence in the root zone, submerged macrophytes established successfully after introduction when the influence of grazing and bioturbation by fish was excluded. In the exclosures, diffusive CH4 and CO2 emissions, but not ebullitive CH4 emissions were significantly reduced. The spontaneous development of submerged macrophytes in the exclosures without macrophyte introduction underlined the effect of grazing and bioturbation by fish and suggest that abiotic conditions did not hamper submerged macrophyte development. Our results provide important insights into the influential factors for submerged macrophyte development and potential for future management practices. Large-scale fish removal may stimulate submerged macrophyte growth and reduce methane emissions, albeit that the macrophyte diversity will likely stay low in our study region due to fluctuating salinity and eutrophic conditions.</p

The costs of HIV treatment and care in Ghana

textabstractObjective: To determine cost functions that describe the dynamics of costs of HIV treatment and care in Ghana by CD4+ cell count at treatment initiation and over time on antiretroviral therapy (ART). Design: We used detailed longitudinal healthcare utilization data from clinical health records of HIV-infected patients at seven Ghanaian ART clinics to estimate cost functions of treatment and care by CD4+ cell count at treatment initiation and time on ART. Methods: We developed two linear regression models; one with individual random effects to determine the relationship between CD4+ cell count at ART initiation and costs of treatment and care, and one with individual fixed effects to determine the causal effect of time in care on costs of treatment and care. Results: Costs for treatment and care were lowest (-7.9 US$) for patients with CD4+ cell counts of at least 350 cells/μl at ART initiation, compared with patients with 50 cells/μl or less at ART initiation, yet the difference was not significant. The per-patient costs peaked during the first 6 months on ART at 112.6 US$, and significantly decreased by 70% after 4 years on treatment. Conclusion: Our findings show that an accurate analysis of resource needs of HIV treatment and care should take into account that healthcare costs for HIV-infected people are dynamic rather than constant. The cost functions derived from our study are valuable input for cost-effectiveness analyses and research allocation exercises for HIV treatment in sub-Saharan Africa