Bio- ja ympäristötieteellinen tiedekunta


Recent Submissions

  • Viljanen, Martta (Helsingin yliopisto, )
    Adaptation to environmental light conditions at different time scales and biological levels was studied using the visual system of opossum shrimps (genus Mysis) as model. The focus of the study was on two aspects of visual adaptation: 1) mechanisms behind spectral tuning which enables effective photon catch in different light environments and 2) photo-induced damage and protective mechanisms in the eyes arising as a trade-off from tuning the visual system to be highly sensitive. For spectral adaptation studies mysids representing 12 species were collected from different water bodies around circumpolar and Caspian areas. Their opsin genes were sequenced and compared with phylogenetic relationships. Spectral sensitivities were determined for 15 populations representing four species by recording single-rhabdom absorption spectra with microspectrophotometer. Water transmission spectra were measured and the wavelength of maximal transmission of light and the attenuation coeffcient was determined to quantify the light conditions in the respective habitats. Animals originating from different environments were also bred in carefully controlled laboratory conditions to observe possible effects of ambient salinity on spectral sensitivity. The photoprotective mechanisms were studied by subjecting animals from populations with intrinsically different vulnerability to light-induced damage to an ultra-slow light acclimation procedure before exposing them to a bright light. The effects of this procedure were examined structurally by transmission electron microscopy and functionally by electroretinography. The equilibrium between rhodopsin and metarhodopsin was studied by microspectrophotometry. The acclimation protocol was conducted at different speeds to investigate the time scale of light acclimation. The studies of spectral tuning show that the spectral sensitivity of different Mysis populations generally correlates in an adaptive manner with the light conditions in their living environment. However, neither opsin gene sequence nor water light transmission could fully explain the observed differences in spectral sensitivities between study populations. Neither were there differences in chromophore use. The findings indicate that there are two opsin genes which are expressed in different proportions following a reaction norm triggered by an yet unidentified environmental factor. This hypothesis still requires more investigation. The study on light damage shows that very slow light acclimation can prevent structural and functional deterioration of photoreceptors caused by bright light exposure. The time scale of successful acclimation corresponds to the tempo of seasonal changes of light levels in the natural habitat. One key player in this phenomenon seems to be the amount of native visual pigment.
  • Kauppi, Laura (Helsingin yliopisto, 2018)
    Introductions of non-native species are changing the composition of plant and animal communities worldwide. In order to assess their ecological and socio-economic impacts it is imperative to know their effects on the surrounding ecosystem. Basic knowledge of the non-native species’ biology, ecology and effects on ecosystem functions in their new environment is therefore needed but often lacking. Naturally low species richness and frequent disturbances make the Baltic Sea one of the most heavily invaded seas in the world. One of the most successful invaders has been the spionid polychaete genus Marenzelleria, three species of which now occur in the Baltic Sea, M. viridis, M. neglecta and M. arctia. Their differing burrowing and ventilation behavior compared to the native species suggest an impact on nutrient cycling. A combination of monitoring data, field surveys and laboratory experiments were used to investigate the ecosystem effects of Marenzelleria spp. The genus occurs in the entire Baltic Sea with highest densities in deeper (over 30 m) areas. M. arctia prefers deeper sites, all three species co-occur at muddy sites up to 20 m depth, and M. viridis and M. neglecta occur together and hybridize at sandy sites. Population dynamics and productivity of the three species differ spatially. Seasonal differences in biotic and abiotic factors lead to variation in the relative importance of Marenzelleria spp. on an important ecosystem function, nutrient cycling. The contribution of Marenzelleria spp. to nutrient cycling was highest during spring when food input to the benthos is high. M. arctia, M. neglecta and M. viridis had density-dependent effects on bioturbation metrics and solute fluxes, implying spatial and temporal variation in their impact on nutrient cycling following seasonal and spatial changes in their densities and biomass. The impact could be modified by the composition of the surrounding macrofauna community and the variation in abiotic factors. Combining the observational and experimental results implies a possible enhancement of phosphorus binding capacity by Marenzelleria spp. in deeper areas especially during summer when oxygen conditions deteriorate and densities increase, but an enhancement of phosphate effluxes in normoxic areas through enhanced remineralization of organic matter. Through density-dependent effects on bioirrigation and directly on ammonium fluxes, the genus also has an impact on nitrogen cycling. The results from this thesis imply spatial and seasonal differences in the impact of Marenzelleria spp. on nutrient cycling related to the environmental conditions and to the densities and biomasses of Marenzelleria spp. and other macrofauna. At disturbed sites Marenzelleria spp. could possibly enhance phosphorus burial and thus remove nutrients from primary production, whereas at undisturbed, normoxic sites they could enhance organic matter remineralization thus preventing deposition of large quantities of organic matter on the sea floor. The results also highlight the need to study the effects on non-native species in the natural environment incorporating the spatial and seasonal variability, and natural community composition in order to accurately estimate their contribution to ecosystem function.
  • Wang, Cui (Helsingin yliopisto, 2018)
    Pleistocene glaciations have profoundly influenced the genetic diversity of organsims in the Northern Hemisphere. Large ice sheets covered vast areas of the Eurasian continent, driving species southward to different isolated refugia, often resulting in deep divergences within species. Phylogeographic studies carried out on Pungitius species based on mitochondrial DNA (mtDNA) support profound intraspecific genetic divergence in refugia during glaciation cycles. However, compared to species distributed at lower latitudes, those distributed at higher latitudes may have also occurred in cryptic refugia in periglacial areas during glaciations, complicating the inferences of the phylogeographic patterns of the fish species with a circumpolar distribution, such as the Pungitius sticklebacks. Moreover, comprehensive phylogenetic studies of Pungitius species have been lacking in the sense that not all extant species have been included into analyses. In this dissertation, I carried out phylogeographic studies on seven Pungitius species using both mtDNA and genome-wide nuclear SNP markers, with worldwide sampling of populations to shed light on intra- and interspecific divergence in this genus, as well as to study their historical demography and interspecific hybridization. By sequencing five mtDNA regions, I found six highly divergent Pungitius lineages including those corresponding to P. pungitius, P. platygaster, P. tymensis and P. kaibarae, and two independent monophyletic lineages of P. laevis. I also found a third lineage of P. laevis that clustered together with P. pungitius. To understand whether this clustering of the P. laevis lineage III and P. pungitius mtDNA was a result of convergence or interspecific introgression, I conducted phylogeographic and population genetic analyses using both mtDNA and nuclear gene sequences. The results indicated asymmetric mitochondrial introgression from P. pungitius to P. laevis and genetic admixture of these species. Hence, the results suggest that the P. laevis lineage III has experienced historical hybridization. Deep intraspecific mitochondrial divergence was found within P. laevis in central and southern France, coinciding with major drainages, suggesting that these areas correspond to distinct glacial refugia for the species explaining the observed intraspecific divergence. To further clarify evolutionary relationships between different Pungitius species and populations, as well as to study the prevalence and extent of introgression among recognized species, phylogenomic datasets were constructed from restriction-site associated DNA in combination with mitochondrial genomes. All divergences in the Western Palearctic were estimated to have occurred during the Pleistocene (≤ 2.6 Ma). The phylogenetic patterns suggest a major split in Pungitius genus occurred early in history, resulting in an East Asian group (P. kaibarae, P. tymensis, P. sinensis) and European - North America group (P. hellenicus, P. platygaster, P. laevis and P. pungitius). The genus probably originated from the Western Pacific and spread to Europe and North America through the Arctic Ocean in several waves after the opening of the Bering Strait. Four cases of incongruence between nuclear and mtDNA-based trees revealed evidence for frequent hybridizations and mitogenome capture during the evolutionary history of this genus. Further analyses of these four cases of cytonuclear incongruence also revealed evidence for nuclear introgression, but the estimated levels of autosomal introgression were low.
  • Kovac, Bianca (Helsingin yliopisto, 2018)
    Actin cytoskeleton is essential in generating mechanical forces together with the associated adhesions and transmitting signals that impact processes such as cell migration. Cell migration is necessary for numerous biological processes including wound healing and embryonic development. Moreover, aberrant cell migration promotes cancer invasion and metastasis. Cell migration events require dramatic spatial and temporal reorganization of the actin cytoskeleton that involves coordinated formation and regulation of multiple structures such as actin stress fibers. Actin stress fibers are dynamic structures, which differ in their subcellular localization, connection to substratum and their dynamics. However, these actin stress fibers are less characterized in terms of the molecules required for assembly-disassembly and the signaling pathways involved in regulating their functions in mesenchymal and epithelial cells. This thesis focuses on characterizing key players and signaling pathways involved in regulating actin stress fiber assembly-disassembly, cell adhesion and contractility. Understanding these cell plasticity changes is essential as in cancer context they are likely to be deregulated thus leading to increased migratory and invasive potential of the cells. During this thesis study, NUAK2 a novel serine-threonine kinase was identified to associate with myosin phosphatase Rho-interacting protein (MRIP) on actin stress fibers. Association between NUAK2 and MRIP increases cells contractility and promotes formation of actin stress fibers through phosphorylation of myosin light chain (MLC). The identified NUAK2-MRIP association reveals a novel mechanism for the maintenance of actin stress fibers. Our findings implicate NUAK2 as an important regulator of cell contractility and actin stress fiber assembly. Thus providing further knowledge of how actin stress fibers and cell contractility can be regulated in mesenchymal cells. To further characterize the specificity of molecules required for the assembly of actin stress fibers, we studied the function of most abundant actin crosslinking proteins in non-muscle cells, α-actinin-1 and α-actinin-4. Our findings reveal that specifically α-actinin-1 and not α-actinin-4, is required to assemble dorsal stress fibers found at the leading edge of mesenchymal cells. In addition, loss of α-actinin-1 modulates cell-matrix adhesions leading to decreased cell migration without altering cells contractility. Contrary to traditional views, dorsal stress fibers assembled by α-actinin-1 are non-contractile and are induced by Rac1 signaling. Rac1 is essential in regulating polymerization of actin filaments. Thus suggesting that force required for cell migration is at least partially generated through actin polymerization. Interestingly, we found α-actinin-1 to be upregulated in various cancers and especially associates with decreased survival in estrogen receptor (ER) negative breast cancer patients. In mammary epithelial cells, α-actinin-1 levels regulate epithelial cell plasticity, reorganize actin stress fibers and destabilize cell-cell adhesions accompanied with increased cell migration. This thesis extends the knowledge of especially α-actinin-1 in regulating actin stress fiber assembly and cell plasticity in both epithelial and mesenchymal cells. Furthermore, identifying α-actinin-1 as a candidate prognostic biomarker in ER negative breast cancer patients.
  • Tauscher, Petra (Helsingin yliopisto, 2018)
    The variety of species in the animal kingdom notwithstanding, early embryogenesis frequently relies on the same set of molecules. These highly conserved molecules are considered genetic toolkit genes; a set of genes that determines the body plan in various species. For example, the determination of the dorsal-ventral (D/V) axis often relies on bone morphogenetic proteins (BMPs). Studies in various organisms, vertebrates as well as invertebrates, established that the BMP signaling network is crucial for localizing the position of the central nervous system. Given that the same set of molecules is used repeatedly in different species, the question of how animal diversity could evolve arises. In this study, I focused on BMP signaling in the fruit fly Drosophila melanogaster. In Drosophila, BMP signaling takes place at various stages of development. Amongst others, it is crucial for D/V patterning of the early embryo, for growth and patterning of the larval wing imaginal disc, as well as for formation of longitudinal and posterior crossveins (PCV) in the pupal wing. The Drosophila genome contains three BMP-type ligands, Decapentaplegic (Dpp), a BMP2/4 type ligand, and the paralogs Screw (Scw) and Glass bottom boat (Gbb), both of which are BMP5-8-type ligands. Interestingly, Scw is exclusively found in higher Dipterans such as Drosophila, and is expressed only in the early embryo, whereas Gbb is repeatedly used during fly development. Previous studies revealed that Scw can replace Gbb in PCV formation in the pupal wing. On the other hand, Gbb cannot function in the context of early embryogenesis. Based on these facts, Gbb and Scw constitute a highly suitable model to study protein divergence and evolution. Here, I examined how post-translational modifications of BMP-type ligands may affect the signaling outcome, and hence, animal development; the focus was on proteolytic processing and N-glycosylation. BMP-type ligands are produced as inactive pro-proteins and need to be proteolytically processed in order to become mature ligands. Scw has two cleavage sites crucial for fly viability. I showed in a cell–based signaling assay that proteolytic processing of both cleavage sites is needed for rapid, peak-level BMP signaling. Furthermore, there exists one highly conserved N-glycosylation motif in the mature BMP ligand domain. In addition, Scw exhibits a unique N-glycosylation site which is not present in other BMP-type ligands. Cell culture-based signaling assays revealed that both N-glycosylation motifs of Scw ligand are needed for peak level signaling. In addition, lack of N-glycosylation motifs negatively affects the BMP signaling outcome in the early embryo, as well as fly viability. In contrast, fewer N-glycosylations appear to be beneficial in the context of PCV formation. These findings suggest that post-translational modifications of BMP ligands play a role in signal transduction and therefore in animal development. Furthermore, I propose that post-translational modifications can act as flexible modules to allow adaption of conserved molecules to different developmental contexts. Besides, understanding how post-translational modifications affect BMP signaling outcome may improve the chances to develop more signaling-efficient BMPs needed in clinical applications.
  • Mätlik, Kärt (Helsingin yliopisto, 2018)
    The human genome contains approximately 20,000 protein-coding genes and tens of thousands of genes for non-coding RNA. Understanding the function of these genes in a living organism is crucial for learning about key processes in early development, mechanisms of organ function and human behavior. Importantly, many human diseases are caused by abnormal gene expression. Therefore, understanding the causes and pathological processes behind these disorders could provide means for early diagnosis, prevention or treatment. The main aim of this thesis was to develop new strategies for studying gene function and regulation in experimental animals. The techniques described in this work allow increasing gene expression specifically in those cell types, which naturally express the gene. The results presented in this thesis suggest that increasing gene expression in correct physiological context may potentially have widespread applications in basic biological studies and for understanding human disease.
  • Gui, Jinghua (Helsingin yliopisto, 2018)
    In this thesis, I mainly investigate how BMP/Dpp signaling is involved in development of the early pupal wing of Drosophila, and the mechanisms coupling Dpp signaling with morphogenesis.
  • Lume, Maria (Helsingin yliopisto, 2018)
    Neurotrophic factors are small secretory proteins with important functions both in the nervous system and in peripheral tissues. Glial cell line-derived neurotrophic factor (GDNF) is best known for its ability to support the survival of midbrain dopaminergic neurons and enteric neurons. Also, GDNF is essential for the development of kidney and testis. It has been shown that both the absence and excessive amounts of GDNF protein negatively regulate kidney morphogenesis, highlighting the importance of proper spatiotemporal regulation of GDNF. Despite the wealth of knowledge regarding GDNF functions both in and outside the nervous system, relatively little is known about the trafficking mechanisms of GDNF. GDNF is synthesized as a precursor protein, proGDNF. In this thesis, we characterized the cellular localization and secretion of two GDNF splice variants, pre-(α)pro-GDNF and pre-(β)pro-GDNF, that differ in their pro-regions. Both precursor forms were shown to be secreted from cell lines. However, while (α)pro-GDNF co-localized mainly with the Golgi markers, the (β)pro-GDNF was found primarily in the secretogranin-II positive vesicles of the regulated secretory pathway. In accordance, the two splice isoforms responded differently to KCl-induced depolarization that is known to trigger the secretion of neurotrophin family members in neuronal cells. Only (β)pro-GDNF and corresponding mature GDNF were secreted activity-dependently, whereas (α)pro-GDNF and its corresponding mature GDNF were secreted via the constitutive secretory pathway. In addition, we determined which enzymes are responsible for the proteolytic cleavage of proGDNF into mature GDNF. To elucidate, whether secreted proGDNF has any biological activity, the recombinant cleavage-resistant proGDNF mutant protein was expressed in mammalian CHO cells and next purified from the media. Our results demonstrate that proGDNF is biologically active. Furthermore, similarly to mature GDNF, proGDNF can signal via the GDNF receptor α1/RET receptor tyrosine kinase complex and activate downstream MAPK and AKT pathways. Interestingly, proGDNF is not able to activate RET via the GFRα2 receptor. Finally, we identified a novel sorting receptor for GDNF and its receptors. Our results show that SorLA, a member of the vacuolar protein sorting 10-p domain receptor family, can internalize GDNF and GFRα1. While GDNF is subsequently degraded in lysosomes, GFRα1 is recycled back to the cell membrane. In the presence of SorLA and GFRα1, also RET is internalized and directed to early endosomes. By regulating the availability of GDNF and its co-receptors, SorLA can inhibit GDNF-induced neurotrophic activity in SY5Y cells. Moreover, SorLA seems to regulate intracellular localization of GFRα1 in hippocampal neurons. In summary, results of this thesis characterize the cellular regulation of GDNF regarding its secretion, processing, internalization and subsequent degradation. Furthermore, this is the first time that biological functions of the GDNF precursor protein proGDNF are described. Our findings indicate that the trafficking of GDNF is very different from that of other neurotrophic factors, and in contrast to apoptotic proneurotrophins, proGDNF is a trophic protein with increased specificity to GDNF receptor complex GFRα1-RET.
  • Rosa, Elena (Helsingin yliopisto, 2018)
    Variation in biotic and abiotic ecological factors unavoidably shapes the life history of living organisms. The ability to integrate environmental cues and respond adequately can mark the difference between life and death. Phenotypic plasticity consists of a rapid response to variation in environmental variables, and it entails the ability of one genotype to generate multiple phenotypes over an environmental gradient. However, the degree of plasticity a phenotypic trait can display is limited by physiological and ecological constraints, which may impose trade-offs on other traits. Insects are an excellent system to explore phenotypic plasticity, because of their presence at all ecosystem levels making them important bio-indicators, and their occurrence in large numbers with a fast generation time making them optimal study subjects. The aim of this thesis is to uncover the degree of phenotypic plasticity in immunity and life-history traits displayed by a butterfly occurring in the temperate zone, the Finnish Glanville fritillary (Melitaea cinxia), in response to variation in the following ecological factors: food quality, larval density, susceptibility to a pupal parasitoid, food limitation and exposure to cold spells. The ecological factors were tested on different life stages of the butterfly, based on their ecological relevance. Particular importance is given to potential trade-offs among life-history traits, with special attention to the immune response. The immune system entails a complex of processes and structures that are activated any time insects interact with their environment, and hence its regulation and maintenance are costly. Therefore, extremely plastic immune responses may not be optimal. The study approach involved a combination of laboratory manipulation of the ecological factors tested, collection of observational data of adult life history and mobility in a semi-natural enclosure, and three different immune assays (encapsulation rate, phenoloxidase activity and immune gene expression). Interactions with two components of the natural community were also included: the host plant pathogen powdery mildew (Podosphaera plantaginis), and the generalist pupal parasitoid wasp Pteromalus apum. Key findings include a poorer performance of larvae fed on a diet including powdery mildew, and the upregulation of two immune genes on the same diet. This suggests that larvae feeding on infected host plants may pay a twofold cost of poor nutrient intake and unnecessary immune activation, potentially due to interaction with the plant pathogen. Moreover, larvae reared in high density showed a better performance and a greater ability to kill brood members of a pupal parasitoid wasp, which, however, did not help butterfly survival. This finding indicates that larvae of this species benefit from group living and do not suffer from stressful interactions in absence of food limitation. Further, a trade-off between pupal investment in the encapsulation immune response and adult mobility was detected, indicating potential costs of immunity in regard to expensive activities such as flight. Finally, cold spells during the pupal stage induced an increased melanisation of adult wings. In males, this response also led to a strong immune reaction to a bacterial challenge and markedly reduced lifespan, suggesting a condition-dependent cost of immunity. The findings indicate that the immune system is affected to some extent by most of the factors tested, but the degree of plasticity displayed may be constrained by costs arising from indiscriminate immune activation.
  • Aarnio-Linnanvuori, Essi (Helsingin yliopisto, 2018)
    This doctoral dissertation discusses environmental education integrated into social school subjects and the challenges of teaching a cross-curricular, value-laden topic, with a data-set consisting of school textbooks and teacher interviews. The study concentrates on environmental education in school subjects of Lutheran religion, secular ethics, history, social studies, and geography. This is a qualitative study, where the main analysis methods were abductive content analysis and phenomenological analysis. The findings reveal difficulties in constructing suitable environmental subject-matter for social school subjects, originating from the wicked nature of environmental problems, especially climate change. The analyzed textbooks gave little space for environmental issues, and they included inaccurate information. Both textbook authors and social subject teachers seemed to have difficulties in recognizing the specific environmental content of their own disciplines. However, some interviewees had found such perspectives to environmental issues that draw on their discipline, and were able to use it for promoting critical thinking. Enthusiasm towards the topic and professional agency seemed to promote success in interdisciplinary education. The interviewees presented different perspectives to teaching value-laden issues. Some preferred neutrality, some aimed for plurality in educational discussion, and some preferred educational advocacy. Self-confidence and an identity as a value educator seemed to support pluralist education and educational advocacy. In addition, the findings support the view that that environmental education often concentrates too much on promoting insignificant individual behaviors. Even though the interviewees were well aware of significant environmental behaviours, they viewed their pupils’ range of action possibilities as narrow. Current school practices and traditions do not support environmental action integrated in school work. Based on the results, I suggest that collective responsibility be promoted in environmental education, and practitioners should develop easy options for youth participation. Key words: environmental education, interdisciplinarity, crosscurricular education, environmental responsibility, critical thinking, environmental citizenship
  • Raissadati, Alireza (Helsingin yliopisto, 2018)
    Heart transplantation is often the last resort for end-stage heart disease. Despite increasing success in this medical field, transplant recipients remain at significant risk for both early and late allograft failure. The cascade of events leading to heart transplant rejection are initiated by donor brain death, progress throughout ex vivo preservation of the organ, are exacerbated during reperfusion, and culminate in cardiac allograft vasculopathy (CAV). The aim of this thesis was to evaluate the efficiency of adeno-associated virus (AAV) as a vector for gene therapy of the heart transplant, elaborate on the role of vascular endothelial growth factor B (VEGF-B) in heart transplant ischemia-reperfusion injury (TX-IRI) and hypoxia-inducible factor (HIF) in the inflammatory properties of allograft-infiltrating myeloid-derived cells. The long-term kinetics and safety of AAV serotypes 2, 8, and 9 were evaluated by perfusing the coronary tree of rat heart transplants with each serotype and comparing the reporter gene expression at set time-points and inflammatory response at the end-point of the study. We studied the role of VEGF-B in ischemia-reperfusion injury of cardiac allografts by transgene- and AAV-mediated overexpression of VEGF-B in rat cardiac allografts. The significance of HIF as an immunoregulatory switch in myeloid-derived cells was determined by using transgenic mice with myeloid cell-targeted activation or knock-out (KO) of HIF-1α and -2α as heart transplant recipients. We found that AAV2 was most effective in transducing heart transplants after intracoronary injection, whereas AAV9 was most effective when injected systemically into the transplant donor. Adeno-associated virus serotype 9 caused a mild inflammatory response in cardiac allografts, whereas AAV2 and 8 did not. Chronic, but not short-term, VEGF-B overexpression in rat cardiac transplants resulted in cardiomyocyte hypertrophy and higher energy demands, with subsequent higher susceptibility towards TX-IRI. HIF-1α and -2α activation in recipient myeloid cells established an immunoregulatory phenotype that significantly suppressed both TX-IRI and acute rejection and prolonged allograft survival. Our results highlight the importance of the route of administration on heart transplant AAV gene therapy and suggest AAV2 as the preferred vector for intracoronary perfusion and AAV9 for systemic delivery in experimental rat heart transplant models. Vascular endothelial growth factor B may regulate heart energy demand and thus might play an important role in transplant ischemic tolerance. Hypoxia-inducible factor-1α and -2α act as important switches for the immunoregulatory phenotype of myeloid cells, and may offer a viable therapeutic target to alleviate allograft rejection.
  • Svensson, Jonas (Helsingin yliopisto, 2017)
    Snow and ice are essential components of the Earth system, modulating the energy budget by reflecting sunlight back into the atmosphere, and through its importance in the hydrological cycle by being a reservoir for fresh water. Light-absorbing impurities (LAI), such as black carbon (BC) and mineral dust (MD), have a unique role in influencing the reflectance of the cryosphere. Deposition of the anthropogenic and natural LAI constituents onto these bright surfaces initiates powerful albedo feedbacks that will accelerate melt. This is important globally, but especially for regions such as the Arctic and the Himalaya. In this thesis, observations from both ambient and laboratory experiments are presented. The overarching research goal has been to better understand the climatic effect of LAI on snow. More specifically, an emphasis has been placed on exploring the process-level interactions between LAI and snow, which will enable better comprehension of LAI affecting the cryosphere. Key findings in this thesis involves the investigations on the horizontal variability of BC concentrations in the surface snow that indicate a larger variability on the order of meter scale at a pristine Arctic site compared to a polluted site nearby a major urban area. In outdoor experiments, where LAI were used to artificially dope natural snow surfaces, the snow albedo was observed to decrease following LAI deposition. The albedo decrease was on the same order as in situ measurements of LAI and albedo conducted elsewhere. As snow melted during the experiment, the snow density was observed to decrease with increasing LAI concentration, while this effect was not observed in non-melting snow. The water retention capacity in melting snow is likely to be decreased by the presence of LAI. Measurements examining the absorption of BC indicate that BC particles in the snow have less absorbing potential compared to BC particles generated in the laboratory. The LAI content of snow pit investigations from two glaciers in the Sunderdhunga valley, northern India, an area not previously examined for LAI, presented high BC and MD content, affecting the radiative balance of the glacier snow. At different points, MD may be greater than BC in absorbing light at the snow surface. A continued monitoring of LAI in the cryosphere, both on the detailed scale explored here, as well as on the larger modelling perspective is needed in order to understand the overall response of the cryosphere to climate change.
  • Lehtimäki, Jenni (Helsingin yliopisto, 2017)
    Biodiversity on earth is threatened and already drastically decreased due to anthropogenic actions. The ravenous utilization of natural resources has reached the point of payback in the forms of climate change, diseased crops, and disturbed water cycles. Obviously, these changes influence wellbeing of mankind. Besides these measurable problems, an invisible world, which covers all surfaces on earth, is altering. Loss of diversity in macroscopic organisms is repeated at the level of micro-organisms, many of which may have disappeared before ever described. The human body is a lively ecosystem hosting millions of microbial organisms, which together form the microbiota. These bacterial, viral, fungal, and other microscopic residents are faced with our immune system, challenging their survival. However, the relationship between the host and the residents is often not hostile, but in most cases reciprocal. Actually, the human immune system has partly shared the responsibility of immune-regulation with commensals. This evolved dependency between human and microbial residents highlights that several health problems may arise if this ancient collaboration is disturbed. Indeed, numerous inflammatory diseases coincide with disturbed host microbiota. These diseases, such as allergies, asthma, inflammatory bowel disease, and cancers, have increased rapidly since recent modernization of human habitats and lifestyle. Still, in traditional farming and hunter-gatherer communities allergies are almost absent. The biodiversity hypothesis, which is the concept tested in this thesis, suggest that change in the invisible world can seriously increase morbidity in human populations. This hypothesis states that the destruction of natural environments has altered our contact with microbial world, which can disturb our immune function, potentially leading to the development of inflammatory diseases. In this thesis, the emphasis is on the effect of exposure to environmental microbes, via the living environment and lifestyle, on health; central factors suggested by the biodiversity hypothesis. The key results from four separate projects, which are based on new datasets, are following. (I) Skin microbiota differs between rural and urban newborns and children. In teenagers this difference disappears, probably due to lifestyle-related changes. (II) Children who attend to nature-oriented outdoor-daycares have considerably more diverse skin microbiota than children in other daycares. However, their life differs in many ways from that of other children, indicating also the importance of lifestyle. (III) In the canine model, the prevalence of allergies is clearly lower in rural environments, also when the effect of dog-breed is controlled. Finally, (IV) the exposure to environmental microbes in residential environment, and through lifestyle, are concurrently related to the skin microbiota and allergies in the canine model. This thesis suggests the importance of living environment and lifestyle, which jointly influence the individual’s contact with environmental microbes, for health. Therefore, the human living environments, and the residing biodiversity in those, can either promote or disrupt human health. Currently, accumulating evidence projects that exposure to green environments, farms, children and animals, basically to all factors that increase microbial exposure directly or indirectly, are beneficial for human health. My thesis adds to this by showing interrelations between microbial exposure, microbiota and allergies. Therefore, people, especially children, and their fellow-animals, should increase their contact with diverse environments and lifeforms in order to support both microbial and immunological balance in their bodies. Finally, natural environments provide yet again one more invaluable ecosystem service, which should be recognized and protected.
  • Salomaa, Anna (Unigrafia, 2017)
    Scientific knowledge shows compelling evidence of intensifying global environmental problems such as biodiversity loss and climate change. Unfortunately, this knowledge has not been directly translated into actions that would have reversed these worrying trends. The effectiveness of conservation, i.e. its ability to produce a desired result, is the outcome of interaction between knowledge and policy process. Efforts have recently been made to use existing scientific knowledge to combine current policy instruments and to develop new innovative approaches to conservation. In this PhD thesis I empirically study the perspectives of various actors and their roles in topical Finnish conservation efforts: green infrastructure, voluntary forest conservation and conflicting peatland policy. I examine how different knowledge types and policy instruments contribute to conservation effectiveness. The study utilizes an expert survey, focus groups, combining multiple methods using the case study approach, and integrating social and ecological data. The results illustrate how actors may interpret differently complex concepts, such as ecosystem services and ecological connectivity; the use of these concepts may even be politically coloured. Ambiguity concerning the definition of green infrastructure may create obstacles for practical implementation. In the peatland conservation policy case, where actors’ interests differed, implemented policy instruments did not match existing knowledge. The role of other knowledge types along with ecological knowledge may be more important when designing voluntary rather than compulsory instruments, because participation to voluntary actions needs to be attractive. The collaboration of actors is an integral part of increasing conservation efforts in the voluntary conservation. Interaction and valuation of various knowledge types may have a complicating effect on conservation practices, but different knowledge types can be integrated for more effective results. The study shows that policies should be designed in a way that allows the practical application of knowledge. The study elucidates what kind of challenges and opportunities for increasing effectiveness are faced in different phases of a policy process. I argue that the use of scientific evidence must be combined with the usage of other knowledge types and involvement of various actors. In addition, potential interest differences of actors should be considered when planning participation. In this way a combination of policy instruments can be developed, which simultaneously increases evidence uptake, acceptance and effectiveness leading to a more sustainable future.
  • Le Tortorec, Anniina (Helsingin yliopisto, 2017)
    Phytoplankton constitute the basis of food webs and are responsible for almost all photosynthesis in the open sea. Occasionally, given suitable conditions, one phytoplankton species can increase in abundance and form a mass occurrence known as a bloom. Harmful Algal Blooms (HABs), in turn, can have adverse effects on the ecosystem, for example causing oxygen depletion, clogging of fish gills, or toxicity. HABs are common in shallow and stratified coastal waters and the number, frequency and coverage of areas affected by HABs are increasing globally mainly due to eutrophication, changes in nutrient ratios and global climate change. One of the main phytoplankton groups forming HABs are dinoflagellates. Among dinoflagellates the genus Alexandrium is particularly notorious with many species in this genus producing a variety of potent neurotoxins. Dinoflagellates are the only known photosynthetic organisms that can produce bioluminescence and the majority of bioluminescence in marine surface waters is produced by dinoflagellates. Bioluminescence in dinoflagellates is considered a defensive mechanism against grazing and many harmful dinoflagellate taxa produce bioluminescence. The dinoflagellate Alexandrium ostenfeldii forms dense bioluminescent blooms in shallow and sheltered areas of the Baltic Sea during the late summer. These blooms pose a potential threat to humans and ecosystems in the region due to observed production of toxins. The distribution and abundance of A. ostenfeldii is poorly known in the coastal waters of the Baltic Sea. The aim of this thesis was to study the variability of A. ostenfeldii bioluminescence production to evaluate whether bioluminescence can be used as an early warning signal of harmful dinoflagellate blooms in the Baltic Sea. More precisely, the aim was to study the expression of A. ostenfeldii bioluminescence to learn how much genetic, phenotypic and environmentally induced variability there is in bioluminescence production in the species. Studies conducted on luciferase genes and bioluminescence emission showed that bioluminescence is a prominent feature in Baltic A. ostenfeldii. Measurements on individual cell cultures and natural populations revealed large daily and seasonal variation in bioluminescence emission relating to the circadian rhythm in bioluminescence expression and seasonal changes in A. ostenfeldii abundance. Large intraspecific variation in bioluminescence production was observed in response to changes in temperature and salinity. A. ostenfeldii abundance, toxin concentrations and bioluminescence intensity were positively correlated in our field data. All tested A. ostenfeldii strains produced both bioluminescence and toxins and it can be assumed that concurrent production of both is a predominant property in Baltic A. ostenfeldii. The obtained results show that it is possible to relate bioluminescence to A. ostenfeldii bloom succession using automated measurements. However, the highly-localized distribution of blooms may require advance knowledge of potential bloom locations to be able to target the monitoring efforts. Species distribution modelling showed promise to address this problem by identifying potentially suitable habitats for A. ostenfeldii.