Browsing by study line "Ympäristömuutos"

Tiivistelmä * Referat * Abstract Brownification is a serious environmental problem, which means a substantial increase in water color. Suggested reasons for brownification are soil recovery from acidification, land-use change, especially ditching, climate change. Brownification changes the light conditions in the lakes, increases thermal stratification, and sedimentation. Despite the considerable effects of brownification on lake ecosystem, currently in the EU Water Framework Directive, there is no sufficient biological indicator for lake browning. Biological indicators of the Water Framework Directive are mainly targeted to eutrophication, and thus are not sufficient for measuring the effects of brownification. Macrophyte chlorophyll a:b ratio has been shown to decrease with decreasing light conditions, thus making it a potential indicator for browning. The seasonal variation of macrophyte chlorophyll content is not well studied. This master’s thesis aims to find out, how the chlorophyll content of yellow water lily (Nuphar lutea) changes during the growing season in lakes with variable water quality. N. lutea was chosen as a study species, as it is very common in different lakes in Finland. It is important to study the seasonal variation of the macrophyte chlorophyll content, because if the chlorophyll content reacts rapidly for example changes in the weather, it might be too sensitive to be used as a long-term indicator for lake browning. It is also needed to study, if the seasonal variation is different in lakes with variable water quality, so that in the future, the possible sampling can be timed right in different lakes. The study lakes were clear water lakes, humic and eutrophic lake, and their water quality and the chlorophyll content of N. lutea were examined with two weeks intervals from June to September. The concentration of chlorophyll a and chlorophyll b were measured from the floating leaf and from the petiole at 10 cm intervals. Based on these, the total chlorophyll concentration (CHL a+b) and CHL a:b ratio was calculated. In addition to macrophyte samples, water samples were taken from each lake from both epilimnion and hypolimnion. From the water samples, dissolved organic carbon, water color, iron concentration and specific ultraviolet absorbance at 254 nm were measured. In addition, water temperature, light intensity, oxygen concentration and water turbidity were measured at each sampling time. The results of this thesis showed, that the CHL a:b ratio, and total CHL concentration (a+b) were significantly lower in the humic than in the clear water lake. In the eutrophic lake, CHL a:b ratio and CHL a+b concentration was higher than in the humic lake but lower than in the clear water lake. In each lake, the CHL a:b ratio increased during the growing season, together with the increasing water clarity. The change in the CHL a:b ratio was detected best in the 10-30 cm petiole depth. In the floating leaf, CHL a:b ratio and CHL a+b concentration varied a lot, meaning that the floating leaf is not a sufficient indicator for brownification. The change in CHL a:b ratio took approximately 5 to 7 weeks, and the seasonal variation was similar in each lake. Based on the results of this thesis, the CHL a:b ratio of the N. lutea petiole seems to be a very promising long-term indicator for lake browning. In the future, it would be, however, important to study, how the carbon sequestration changes as a result of brownification, if the macrophyte chlorophyll concentration decreases, since this might have considerable effects on lake carbon sequestration. Also, the eutrophic study lake of this thesis had a water color over 100 mg Pt l-1, so it would be important to study, what is the macrophyte chlorophyll content in clear, but eutrophic lakes.

Underwater light climate in mountain lakes is controlled by dissolved organic carbon concentrations and by lake ice regimes. Both are affected by local, regional and global variables linked to anthropogenic disturbances such as climate change and atmospheric pollution. Aim of this work was to investigate changes in underwater light climate over the past ~200 years in two oligotrophic mountain lakes and how it reflects on diatom (Bacillariophyceae) guild distribution. For these aims, diatom communities and ecological guilds were analyzed from sediment core and contemporary habitat samples along a depth gradient. In addition, sediment inferred chlorophyll a (CHLa) and lake water total organic carbon (TOC) were analyzed to detect development of primary production and lake water carbon content. Results showed that acidification of the lakes together with climate induced changes have been important drivers of the ecology of the lakes. Lake water TOC showed a decline and subsequent increase in line with the acidification and subsequent recovery of the lakes, likely affecting underwater light climate in the lakes. However, this did not reflect unambiguously into changes in diatom functionality. Warming has likely contributed to diversification of the diatom community over the study period while no distinct increases were observed in whole lake primary production. Overall, if the present study could not distinguish the exact role of underwater light in driving changes in diatom communities and functional traits, the result show that human pressures have left distinct imprints in the development of biotic communities in these remote mountain lakes.

Mercury (Hg) is a heavy metal acknowledged as a worldwide contaminant that accumulates in organisms and biomagnifies in food webs. The organic methylmercury (MeHg) species is harmful to animals, including humans, and mainly derived from the diet. The dietary Hg consumed by fish is mostly removed through the intestine, but some of the MeHg bioaccumulates, especially in the white muscle tissue of fish. Perch (Perca fluviatilis) and roach (Rutilus rutilus) are commonly found fish species in Finland. Perch has additional im-portance as it is the national fish of Finland, a popular food fish, as well as a monitoring species used to evaluate the chemical status of lakes. Seasonal variation of Hg in muscle tissue of fish is supposedly caused by starvation in winter, which condenses Hg in the muscle, and growth dilution in summer, which refers to fast somatic growth during the growing season, which dilutes Hg in the muscle. Similar to winter, spawning has also been found to condense Hg in muscle tissue of fish due to high energy investment into gonad development. Seasonal variation of Hg and variables driving seasonal changes have been shown to differ between fish species. Seasonal variation has been studied mainly during the open-water season. However, less is known about how winter conditions under ice affect Hg levels in fish. In this MSc thesis, I asked (Q1) How total mercury (THg) content in the muscle tissue of perch and roach change annually? (Q2) How THg bioaccumulation in the muscle tissue of perch and roach change annually? (Q3) What are the factors explaining annual variation in THg content in the muscle tissue of perch and roach? The practical application of results was to discuss if annual variation should be considered in monitoring programs and human health questions. The materials used in this study were collected from Lake Pääjärvi monthly from March 2020 to March 2021. Fish were collected using gillnet series. Length, weight, sex, sexual maturity, stomach fullness, Fulton’s condition factor (K), and muscle THg were determined from each fish. The annual length-corrected THg content variation was tested using analysis of variance. The annual THg bioaccumulation variation in the relationship between muscle and fish length was tested using simple linear regression analysis, and the seasonal variation in THg bioaccumulation was tested with LOESS regression analysis. Variables affecting seasonal variation were tested with stepwise multiple linear regression analysis. THg content of perch was the highest in winter and spring and the lowest in fall, while roach showed no significant seasonal variation. THg bioaccumulation of both species was highest in winter, spring, and early summer and lowest in fall. Perch displayed more substantial seasonal variation than roach. Biological and environmental variables that explained the THg content of perch were length, ice thickness, gonadosomatic index (GSI), light, and condition factor. Variables that explained the THg content of roach were length, sex, and total phosphorus (Tot-P). This study confirmed that starvation in winter, growth dilution in summer, and spawning in spring/early summer are vital factors driving seasonal variation. Due to evident seasonal variation, monitoring month should be pre-set in current monitoring programs.

Cladocerans play a key role in the aquatic ecosystem. They are abundant in lakes and are an essential part in the carbon and energy transfer of the food webs. These species are, however, prone to various environmental changes. Estimates have shown that dissolved organic carbon (DOC) concentrations in northern lakes are likely to increase in the future. This increase of DOC in lakes has multiple impacts ranging from nutrient levels to shading impacts reducing primary productions. Investigating changes in cladocerans along a DOC gradient could help us understand how these species might develop in the future in our changing climate. In this Master’s Thesis, I studied how the cladoceran body length and community structure varied between 9 lakes with dissolved organic carbon (DOC) concentration ranging from 2.4-33.5 mg l-1. For the analyses, these lakes where divided into two groups with a threshold of 12 mg l-1 or into groups of three based on their DOC concentrations. Then, the results were compared with cladoceran length data from an earlier study. Additionally, the changes in phytoplankton abundances and communities as well as the relation between DOC concentration and other environmental variables were analysed. The results showed an increase in the cladoceran body length above the DOC threshold. Moreover, the changes in body length varied between the studied genera. Both Ceriodaphnia sp. and Diaphanosoma sp. body length decreased in groups with higher DOC concentrations while Bosmina sp. were larger at high DOC concentrations. DOC concentration did not have any significant effect on the community structure of zooplankton. The studied lakes varied from their environmental condition making comparisons and general statements challenging. The results indicated that DOC concentration regulates the planktonic communities, but it is solely an imprecise predictor for changes in zooplankton communities. However, cladoceran densities seemed to benefit from increased DOC concentrations as nutrient levels also increased. Changes in cladoceran body lengths were challenging to interpret, because there are multiple factors that can have an impact both alone and combined with others.

Microbial diversity can be found everywhere around us. The diversity is however declining globally and the diversity loss is most visible in highly urbanized areas. The lack of microbial biodiversity has been linked to increased risk of certain im-mune mediated diseases most prevalent within urban population. Understanding how diversity differs between urban and rural areas can help us to figure out mechanisms behind biodiversity loss and higher frequency of immune-mediated dis-eases and develop prevention methods for the latter. The aim of the thesis is to study how bacterial communities differ between urban and rural areas using indicator species as proxy. The aim is also to find out if the results support the biodiversity hypothesis. The results of the thesis found out significant differences in diversity indexes between bacterial communities in urban and rural areas, which supports the biodiversity hypothesis. The study also found differences in Proteobacteria diversity index-es, which have been linked to some immune mediated diseases in previous studies.

Northern peatlands have a major role in the global carbon cycle due to their carbon stocks and fluxes of carbon dioxide (CO2) and methane (CH4). Anthropogenic climate change may affect peatland carbon dynamics through changes in e.g. primary production, hydrology, and permafrost dynamics. It is uncertain whether these changes will lead to northern peatlands becoming significant sources of carbon to the atmosphere. Changes in moisture conditions especially can be an important factor in determining the carbon sink potential of northern peatlands. In this thesis I examine the palaeohydrology and peat accumulation over the past centuries in a permafrost peatland complex in Lovozero, Kola Peninsula, Russia. I used testate amoebae as a proxy of past changes in moisture conditions. Other study methods used here are detrended correspondence analysis (DCA) and 14C and 210Pb dating. The results were also supplemented with plant macrofossil and carbon accumulation data provided by other members of the research team. The results show varying responses of the peatland hydrology and peat accumulation to the past climatic shifts, suggesting that the changes have been driven more by autogenic factors rather than climate. However, all three sites indicated a drying trend and an increased peat accumulation for the last century. Yet, the last decade is charachterised by a wet shift. The wet shifts suggest that the peatlands may have crossed a threshold where increased evapotranspiration is exceeded by increased moisture due to thawing permfrost. The surface peat layers of all three sites were dominated by mixotrophic testate amoebae, which may have contributed to the high peat accumulation. The inconsistency of past successional pathways identified at Lovozero peatlands and the drying trend over the past century correspond to the previous studies from northern peatlands elsewhere. However, the most recent surface wetting during the last decade differs from what has been reported for the other northern sites. This suggests that the response mechanisms of peatlands to the anthropogenic climate change may not be uniform. Thus, further research is inevitably needed to increase our understanding of peatland-climate intercations.

Agroforestry is a collective name for land-use systems and technologies where woody perennials are deliberately used on the same land-management units as agricultural crops and/or animals. Silvopasture is a type of agroforestry that integrates trees, livestock, and forage crops on the same piece of land. This topic is specifically interesting because silvopasture is already present in Finland, mostly in the form of traditional biotopes, despite these being endangered habitats. Agroforestry is also recognized by the Kyoto Protocol as an afforestation practice that has several advantages. These include environmental benefits, increased productivity, and animal welfare. However, there has been discussion on detrimental effects of animal presence to the trees as well. This research aims to explore the effects of silvopasture on trees, cattle, and the environment in South-western Finland traditional biotopes. Several individual criteria are assessed in three categories: woodland, animal performance and biodiversity. Data was collected on three farms on four pastures through field surveys and farmer interviews. The data is analyzed through multi criterium decision analysis (MCDA) with normalized values from agriculture and forestry to assess performance of silvopastures on three separate categories. Results from four pastures follow a somewhat similar pattern but variation occurs. High scores of forest indicators are reached in woodland category whereas biodiversity category results are lower. Silvopasture negatively affects forest regeneration but otherwise does not have adverse effects. Cattle performance is positive outcome whereas biodiversity category has room for improvement. To get more accurate and comprehensive results the research should be conducted during growing season and with several farms around Finland. However, silvopasture is a meaningful measure to diversify habitats, contribute to animal wellbeing and strengthen ecosystem services.

Kiihtyvän ilmastonmuutoksen aikana on entistä tärkeämpää löytää tapoja vähentää päästöjä ja sitoa hiiltä. Biohiilen käyttö on yksi keino ilmastonmuutoksen hillitsemiseen, ja sillä on potentiaalia parantaa maatalouden satoja. Ennen kuin biohiilen käyttö voi yleistyä, sen mahdolliset ulkoisvaikutukset, kuten vaikutukset maaperän eliöstöön, on kuitenkin ensin selvitettävä. Tässä opinnäytetyössä tutkittiin biohiilen käytön vaikutuksia mikrobien suhteelliseen runsauteen, kastematoyhteisöihin ja mikrobibiomassaan. Vain lauhkean ja boreaalisen vyöhykkeen kenttätutkimukset olivat osana tutkimusta. Biohiilen vaikutukset mikrobiryhmien suhteelliseen määrään selvitettiin kirjallisuuskatsauksella. Kirjallisuuskatsaus tehtiin myös selvittäessä biohiilen vaikutuksia kastematoihin. Biohiilen vaikutukset mikrobibiomassaan selvitettiin meta-analyysillä. Meta-analyysissä käytetyt tutkimukset luokiteltiin muuttujien, kuten biohiilen raaka-aineen, pyrolyysilämpötilan, maaperän pH:n, SOC:n, maaperän rakenteen ja biohiilen levitysmäärän perusteella. Tätä kautta voitiin selvittää, voisiko jokin näistä muuttujista selittää meta-analyysin tulokset. Mikrobien suhteellisen runsauden havaittiin muuttuvan biohiilen lisäyksen myötä, mutta reagoivat organismiryhmät vaihtelivat suuresti ja vaikutus yleensä haihtui ajan myötä. Biohiilen lisääminen ei vaikuttanut kastematoihin merkittävästi. Meta-analyysien tulokset viittaavat siihen, että biohiilellä ei myöskään ole merkittävää vaikutusta mikrobien kokonaisbiomassaan. Eri muuttujilla tehdyt meta-analyysit viittaavat siihen, että biohiilen lisäyksellä on positiivisin vaikutus mikrobien biomassaan happamissa maaperissä, joissa on karkea rakenne ja korkea SOC-pitoisuus, kun biohiiltä tuotetaan 500 °C–700 °C:ssa ja levitetään määrinä, jotka ovat suurempia tai yhtä suuri kuin 30 t ha-1. Biohiilen raaka-aineella ei havaittu olevan merkittävää vaikutusta. Yhteenvetona voidaan todeta, että mikrobi- ja kastematoyhteisöt pysyvät yleensä vakaina biohiiltä käytettäessä. Tämä mahdollistaisi biohiilen käytön mm. hiilen sitomiseen ja maaperän hedelmällisyyden lisäämiseen maaperän eliöstöä vahingoittamatta. Lisätutkimusta kaivataan kuitenkin erityisesti boreaalisilla alueilla sekä biohiilen ja pääviljelykasvin mahdollisista vuorovaikutuksista. Tutkia kannattaisi myös mahdollisuuksia käyttää biohiiltä yhdessä muiden orgaanisten käsittelyjen, kuten lannan tai kompostin kanssa biologisen monimuotoisuuden ja sadon parantamiseksi.

The main motivator of this thesis was to discover the importance of Chaoborus in a eutrophic and dystrophic lake and evaluate suitable restoration methods to enhance the state of the study lake. The role of Chaoborus in the study lake, Lake Jouttenus, was studied with sampling of both the water column and the sediment, echo-surveys, and diet analyses of fish. The sampling was planned as comprehensive, and the sampling stations were distributed across the whole lake area to examine the density and distribution of Chaoborus. The deeper areas of the lake were emphasized more in sampling because Chaoborus tend to favor those areas. The Chaoborus density was calculated with stratified sampling, which gives a more precise mean density estimate than simple random sampling. In addition, fish were caught on four (4) study occasions to find out if they had included Chaoborus in their diets. The mean density of Chaoborus in Lake Jouttenus was a little lower than expected, only 271 individuals/m2 in areas ≥2 m depth. The highest density of larvae was found from mid-depths between 6.0-7.9 m in the sediment. Only the deepest areas (≥8 m depth) had limnetic Chaoborus and more limnetic than benthic larvae. The mean length of larvae was 8.4 mm in the sediment and 9.0 mm in the water column. The length distributions appeared to be unimodal. Echo-surveys confirmed that the larvae occurred in the water column only in the deepest area in the north of the lake where the hypolimnion had a low oxygen concentration below 4 m depth. The diet analyses showed that roach and perch had eaten Chaoborus but the number of Chaoborus was high only in the diet of roach in early July. In comparison with other studied lakes, the density of Chaoborus was the lowest in Lake Jouttenus. In addition, the mean length of benthic Chaoborus in Lake Jouttenus was lower than in the other studied humic lakes. The distribution of limnetic Chaoborus appeared as restricted to the deepest areas in the lake and elsewhere the larvae occurred only in the sediment. The slow growth of Chaoborus and their low mean density could be explained by the lack of an efficient refuge and probably also the lack of resources. The larvae were unable to reach the epilimnion and their prey safely at daytime and/or the amount and quality of food items for the larvae were poor. The darkness caused by humic substances and low oxygen concentration in the hypolimnion created a refuge for the limnetic larvae only in the deepest area of Lake Jouttenus. Roach and perch ate Chaoborus occasionally. However, mass removal of fish is not recommended as it would decrease the predation pressure by fish on Chaoborus and increase the risk of Chaoborus population growth at the deepest areas and enable their range to extend. Instead of mass removal of fish all methods that aim in reducing the humic substances in the water especially at the lake catchment area might enhance the state of the lake. The clarification of water would diminish the living conditions for Chaoborus in long-term and help with controlling the other troubling factors such as Gonyostomum semen blooms in the study lake.

Participatory budgeting (PB) is increasingly recognized as a democratic tool for citizens to make changes in their lives by directly affecting budget allocations. However, its effectiveness in tackling environmental change issues remains unclear. In this study, it was explored to which extent PB can be used to address environmental issues directly by examining the locality and themes of environmentally themed proposals made by citizens of Helsinki in its participatory budgeting program of 2018-2019. The research questions were two-fold: (1) what kind of environmentally themed proposals did the citizens of Helsinki propose in the participatory budgeting program, and (2) how globally, glocally or locally focused were the proposals? To address these questions, a qualitative analysis of the proposals made by citizens in the Helsinki participatory budgeting program was conducted. The proposals were categorized based on their environmentally related themes and the extent to which they were focused on local or global issues was examined. The key findings suggest that citizens in Helsinki propose ideas at both local and glocal levels. Citizens were found to vote for environmentally friendly ideas more often than they propose them initially. Additionally, a categorization system was developed that can be used by cities to categorize the environmental proposals made by their citizens. This research advances knowledge in the field of environmentally based PB by shedding light on the locality of environmental proposals and the potential for PB to address global environmental issues. The developed categorization system can help cities better understand the types of environmental proposals their citizens are interested in and support the development of more effective participatory budgeting programs. Overall, this research underscores the potential of participatory budgeting as a tool for addressing environmental issues and emphasizes the importance of citizen engagement in the policy-making process.