Spatial and temporal variability in midge (Nematocera) assemblages in shallow Finnish lakes (60−70 °N) : community-based modelling of past environmental change

Multi- and intralake datasets of fossil midge assemblages in surface sediments of small shallow lakes in Finland were studied to determine the most important environmental factors explaining trends in midge distribution and abundance. The aim was to develop palaeoenvironmental calibration models for the most important environmental variables for the purpose of reconstructing past environmental conditions. The developed models were applied to three high-resolution fossil midge stratigraphies from southern and eastern Finland to interpret environmental variability over the past 2000 years, with special focus on the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) and recent anthropogenic changes. The midge-based results were compared with physical properties of the sediment, historical evidence and environmental reconstructions based on diatoms (Bacillariophyta), cladocerans (Crustacea: Cladocera) and tree rings. The results showed that the most important environmental factor controlling midge distribution and abundance along a latitudinal gradient in Finland was the mean July air temperature (TJul). However, when the dataset was environmentally screened to include only pristine lakes, water depth at the sampling site became more important. Furthermore, when the dataset was geographically scaled to southern Finland, hypolimnetic oxygen conditions became the dominant environmental factor. The results from an intralake dataset from eastern Finland showed that the most important environmental factors controlling midge distribution within a lake basin were river contribution, water depth and submerged vegetation patterns. In addition, the results of the intralake dataset showed that the fossil midge assemblages represent fauna that lived in close proximity to the sampling sites, thus enabling the exploration of within-lake gradients in midge assemblages. Importantly, this within-lake heterogeneity in midge assemblages may have effects on midge-based temperature estimations, because samples taken from the deepest point of a lake basin may infer considerably colder temperatures than expected, as shown by the present test results. Therefore, it is suggested here that the samples in fossil midge studies involving shallow boreal lakes should be taken from the sublittoral, where the assemblages are most representative of the whole lake fauna. Transfer functions between midge assemblages and the environmental forcing factors that were significantly related with the assemblages, including mean air TJul, water depth, hypolimnetic oxygen, stream flow and distance to littoral vegetation, were developed using weighted averaging (WA) and weighted averaging-partial least squares (WA-PLS) techniques, which outperformed all the other tested numerical approaches. Application of the models in downcore studies showed mostly consistent trends. Based on the present results, which agreed with previous studies and historical evidence, the Medieval Climate Anomaly between ca. 800 and 1300 AD in eastern Finland was characterized by warm temperature conditions and dry summers, but probably humid winters. The Little Ice Age (LIA) prevailed in southern Finland from ca. 1550 to 1850 AD, with the coldest conditions occurring at ca. 1700 AD, whereas in eastern Finland the cold conditions prevailed over a longer time period, from ca. 1300 until 1900 AD. The recent climatic warming was clearly represented in all of the temperature reconstructions. In the terms of long-term climatology, the present results provide support for the concept that the North Atlantic Oscillation (NAO) index has a positive correlation with winter precipitation and annual temperature and a negative correlation with summer precipitation in eastern Finland. In general, the results indicate a relatively warm climate with dry summers but snowy winters during the MCA and a cool climate with rainy summers and dry winters during the LIA. The results of the present reconstructions and the forthcoming applications of the models can be used in assessments of long-term environmental dynamics to refine the understanding of past environmental reference conditions and natural variability required by environmental scientists, ecologists and policy makers to make decisions concerning the presently occurring global, regional and local changes. The developed midge-based models for temperature, hypolimnetic oxygen, water depth, littoral vegetation shift and stream flow, presented in this thesis, are open for scientific use on request.

Epidemiology, treatment and outcome of Staphylococcus aureus bacteremia and endocarditis

Staphylococcus aureus is the second most common bloodstream isolate both in community- and hospital-acquired bacteremias. The clinical course of S. aureus bacteremia (SAB) is determined by its complications, particularly by the development of deep infections and thromboembolic events. Despite the progress of antimicrobial therapy, SAB is still associated with high mortality. However, injection drug users (IDUs) tend to have fewer complications and better prognosis than nonaddicts, especially in endocarditis. The present study was undertaken to investigate epidemiology, treatment and outcome of S. aureus bacteremia and endocarditis in Finland. In particular, differences in bacterial strains and their virulence factors, and host immune responses were compared between IDUs and nonaddicts. In Finland, 5045 SAB cases during 1995-2001 were included using the National Infectious Disease Register maintained by National Public Health Institute. The annual incidence of SAB increased, especially in elderly. While the increase in incidence may partly be explained by better reporting, it most likely reflects a growing population at risk, affected by such factors as age and/or severe comorbidity. Nosocomial infections accounted for 51% of cases, with no change in their proportion during the study period. The 28-day mortality was 17% and remained unchanged over time. A total of 381 patients with SAB were randomized to receive either standard antibiotic treatment or levofloxacin added to standard treatment. Levofloxacin combination therapy did not decrease the mortality, lower the incidence of deep infections, nor did it speed up the recovery during 3 months follow-up. However, patients with a deep infection appeared to benefit from combination therapy with rifampicin, as suggested also by experimental data. Deep infections were found in 84% of SAB patients within one week after randomization, and they appeared to be more common than previously reported. Endocarditis was observed in 74 of 430 patients (17%) with SAB, of whom 20 were IDUs and 54 nonaddicts. Right-sided involvement was diagnosed in 60% of addicts whereas 93% of nonaddicts had left-sided endocarditis. Unexpectedly, IDUs showed extracardiac deep infections, thromboembolic events and severe sepsis with the same frequency as nonaddicts. The prognosis of endocarditis was better among addicts due to their younger age and lack of underlying diseases in agreement with earlier reports. In total, all 44 IDUs with SAB were included and 20 of them had endocarditis. An equal number of nonaddicts with SAB were chosen as group matched controls. Serological tests were not helpful in identifying patients with a deep infection. No individual S. aureus strain dominated in endocarditis among addicts. Characterization of the virulence factors of bacterial strains did not reveal any significant differences in IDUs and nonaddicts.

Agricultural expansion and climate change in the Taita Hills, Kenya: an assessment of potential environmental impacts

The indigenous cloud forests in the Taita Hills have suffered substantial degradation for several centuries due to agricultural expansion. Currently, only 1% of the original forested area remains preserved in this region. Furthermore, climate change imposes an imminent threat for local economy and environmental sustainability. In such circumstances, elaborating tools to conciliate socioeconomic growth and natural resources conservation is an enormous challenge. This dissertation tackles essential aspects for understanding the ongoing agricultural activities in the Taita Hills and their potential environmental consequences in the future. Initially, alternative methods were designed to improve our understanding of the ongoing agricultural activities. Namely, methods for agricultural survey planning and to estimate evapotranspiration were evaluated, taking into account a number of limitations regarding data and resources availability. Next, this dissertation evaluates how upcoming agricultural expansion, together with climate change, will affect the natural resources in the Taita Hills up to the year 2030. The driving forces of agricultural expansion in the region were identified as aiming to delineate future landscape scenarios and evaluate potential impacts from the soil and water conservation point of view. In order to investigate these issues and answer the research questions, this dissertation combined state of the art modelling tools with renowned statistical methods. The results indicate that, if current trends persist, agricultural areas will occupy roughly 60% of the study area by 2030. Although the simulated land use changes will certainly increase soil erosion figures, new croplands are likely to come up predominantly in the lowlands, which comprise areas with lower soil erosion potential. By 2030, rainfall erosivity is likely to increase during April and November due to climate change. Finally, this thesis addressed the potential impacts of agricultural expansion and climate changes on Irrigation Water Requirements (IWR), which is considered another major issue in the context of the relations between land use and climate. Although the simulations indicate that climate change will likely increase annual volumes of rainfall during the following decades, IWR will continue to increase due to agricultural expansion. By 2030, new cropland areas may cause an increase of approximately 40% in the annual volume of water necessary for irrigation.