Made available in DSpace on 2017-07-10T14:38:28Z (GMT). No. of bitstreams: 1 tassia.pdf: 1244152 bytes, checksum: 94c85e90bbbe81a039be502cd6b74f66 (MD5) Previous issue date: 2015-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Different land uses directly affect the characteristics of a river basin, reflecting the health and integrity of the aquatic environment, and consequently influence the aquatic biota and ecosystem processes. This study aimed to analyze the structure and community composition of aquatic invertebrates and the role of these organisms in the process of decomposition of leaf litter in streams with different land uses. Samples were collected in the period from September to December 2013 in five streams of western Paraná. At each stream were placed 18 bags containing litter for colonization by aquatic invertebrates during the exposure times of 15, 30, 45, 60, 75 and 90 days. Significant spatial differences in the structure and composition of the community of aquatic invertebrates in the studied streams were recorded. There were no significant differences in the activity of aquatic invertebrates in the leaf decomposition process streams with different land uses. But there were differences in the variability of decomposition between the streams, and the reference stream showed lower variability in the decomposition process. This result may have been influenced by habitat quality, availability of organic matter, and the structure and composition of benthic community present in the reference stream, which differs significantly between locations with different types of land use. The results of this study demonstrate that human interference in the aquatic environment through land use can influence negativity in ecosystem processes, particularly in invertebrate activity during the processing of allochthonous material, as well as modify the structure and composition of the biota. / Diferentes usos do solo afetam diretamente as características de uma bacia hidrográfica, refletindo na saúde e integridade do ambiente aquático, e, consequentemente, influenciam a biota aquática e os processos ecossistêmicos. Este trabalho teve como objetivo analisar a estrutura e composição da comunidade de invertebrados aquáticos e o papel desses organismos no processo de decomposição de detritos foliares em riachos com diferentes usos do solo. As coletas foram realizadas no período de setembro a dezembro de 2013 em cinco riachos da região oeste do Paraná. Em cada riacho foram colocadas 18 bolsas contendo folhiço para a colonização por invertebrados aquáticos durante os tempos de exposição de 15, 30, 45, 60, 75 e 90 dias. Foram registradas diferenças espaciais significativas na estrutura e composição da comunidade de invertebrados aquáticos entre os riachos estudados. Não houve diferenças significativas na atividade de invertebrados aquáticos durante o processo de decomposição foliar em riachos com diferentes usos do solo. Porém houve diferenças na variabilidade da decomposição entre os riachos, sendo que o riacho de referência apresentou menor variabilidade no processo de decomposição. Esse resultado pode ter sido influenciado pela qualidade do hábitat, disponibilidade de matéria orgânica, e pela estrutura e composição da comunidade bentônica presente no riacho de referência, a qual difere significativamente entre os locais com diferentes tipos de ocupação do solo. Os resultados deste estudo demonstram que a interferência humana no ambiente aquático, por meio do uso do solo, pode influenciar negatividade nos processos ecossistêmicos, em especial na atividade de invertebrados durante o processamento de material alóctone, além de modificar a estrutura e composição da biota.

Climate change scenarios predict that seawater temperature and precipitation will increase in the Baltic Sea region during the next century. In the northern part of the Baltic Sea, increasing inflows of the terrestrial allochthonous dissolved organic matter (ADOM) are expected to be a major consequence of elevated rainfall, which can alter light and nutrient availability for phytoplankton. The aim of my thesis was to elucidate effects of ADOM on phytoplankton production, community, size-structure and nutritional strategy along offshore south-north gradients in the Baltic Sea, as well as in estuarine systems exposed to seasonal variation in river discharge. Field studies, a mesocosm experiment and a modeling study were used to explore these issues. Results from the field studies and mesocosm experiment illustrated that the nutritional strategy, size-structure and cellular pigment content of the phytoplankton were governed by changes in ADOM, and thus in light and nutrient availability. A summer study along an offshore south-north gradient showed that the proportion of mixotrophic phytoplankton increased towards the north. In this area the concentrations humic substances (proxy for ADOM) were high, while the light availability and phosphorus concentrations were relatively low. The phytoplankton cells responded to reduced light availability by increasing their chlorophyll a: carbon ratio. Additionally, the levels of photoprotective pigments decreased from south to north, as a result of acclimation to a low-light environment and reduced exposure to ultraviolet radiation. According to ecological assumptions picophytoplankton should be favored in light- and nutrient-limited environments. However, the results did not follow that pattern, the proportion of picophytoplankton being highest in the relatively nutrient rich Baltic Proper. The study was performed during the decline of an extensive bloom of filamentous cyanobacteria, a successional phase in which picophytoplankton often dominate the phytoplankton community. The estuarine studies performed in the Bothnian Bay (Råne estuary) and in the Bothnian Sea (Öre estuary) showed different successions. In the Råne estuary no spring phytoplankton bloom occurred and highest primary production was observed during the summer. This absence of a spring bloom was explained by low phosphorus and high ADOM concentrations, while the summer maximum could be explained by higher temperature and nutrient concentrations. In the Öre estuary a marked phytoplankton spring bloom was observed as well as an ADOM sustained bacterial production phase. The later secondary peak of bacterial production observed in summer, concomitant with an extended secondary primary production peak, suggests that autochthonous dissolved organic matter supported the bacterial growth Furthermore, the photosynthetic efficiency (i.e. phytoplankton growth rates) was lower during spring, indicating that high ADOM, and thus lower light and phosphorus availability, disfavored phytoplankton growth. Our modeling study showed that climate change can impact the food web; however effects will be different between basins. In the southern Baltic Sea elevated temperature and nutrient discharge may promote nutrient recycling and oxygen consumption, potentially extending anoxic areas, sediment nutrient release and cyanobacteria blooms. In the north, increased inflow of ADOM may promote heterotrophic bacterial production and decrease primary production due to light attenuation and lower phosphorus availability. This will favor the heterotrophic microbial food web and consequently lead to lower food web efficiency of the ecosystem.

Autotrophs and heterotrophs differ in their demand, acquisition and use of materials, but fundamentally nutrient demand is inherently linked to metabolism based on the stoichiometry of biochemical reactions. The differences between these two groups of organisms confound straightforward regression approaches to quantifying the relationship between nutrient demand and metabolism at an ecosystem level. We address how nutrient demand in headwater streams changes with shifts in organic matter supply and associated microbial activity by investigating these relationships in the predominantly heterotrophic conditions of a southern Appalachian stream. We measured litter input, organic matter standing crops, litter respiration rates and nitrate demand several times during the course of decomposition. There was a strong relationship between leaf standing crop and nitrate uptake efficiency across dates with maximal efficiency occurring when litter standing crops were highest. There was also an increase in nitrogen (N) uptake rate relative to respiration rates as breakdown progressed, which appears to be due to a shift in nutrient supply from the substrate to the water column associated with the depletion of labile, high quality organic matter in the substrate. It is our contention that streams establish a gradient of resource supply from particulate to dissolved sources that coincides with the movement of materials from terrestrial to marine systems. / Master of Science

Climate change is expected to increase the precipitation ~30% in higher latitudes during the next century, increasing the land runoff via rivers to aquatic ecosystems. The Baltic Sea will receive higher river discharges, accompanied by larger input of allochthonous dissolved organic matter (DOM) from terrestrial ecosystems. The salinity will decrease due to freshwater dilution. The allochthonous DOM constitute a potential growth substrate for microscopic bacterioplankton and phytoplankton, which together make up the basal trophic level in the sea. The aim of my thesis is to elucidate the bacterial processing of allochthonous DOM and to evaluate possible consequences of increased runoff on the basal level of the food web in the Baltic Sea. I performed field studies, microcosm experiments and a theoretical modeling study. Results from the field studies showed that allochthonous DOM input via river load promotes the heterotrophic bacterial production and influences the bacterial community composition in the northern Baltic Sea. In a northerly estuary ~60% of bacterial production was estimated to be sustained by terrestrial sources, and allochthonous DOM was a strong structuring factor for the bacterial community composition. Network analysis showed that during spring the diversity and the interactions between the bacteria were relatively low, while later during summer other environmental factors regulate the community, allowing a higher diversity and more interactions between different bacterial groups. The influence of the river inflow on the bacterial community allowed “generalists” bacteria to be more abundant than “specialists” bacteria.    Results from a transplantation experiment, where bacteria were transplanted from the northern Baltic Sea to the seawater from the southern Baltic Sea and vice versa, showed that salinity, as well as the DOM composition affect the bacterial community composition and their enzymatic activity. The results showed that α-proteobacteria in general were favoured by high salinity, β-proteobacteria by low salinity and terrestrial DOM compounds and γ-proteobacteria by the enclosure itself. However, effects on the community composition and enzymatic activity were not consistent when the bacterial community was retransplanted, indicating a functional redundancy of the bacterial communities.  Results of ecosystem modeling showed that climate change is likely to have quite different effect on the north and the south of the Baltic Sea. In the south, higher temperature and internal nutrient load will increase the cyanobacterial blooms and expand the anoxic or suboxic areas. In the north, climate induced increase in riverine inputs of allochthonous DOM is likely to promote bacterioplankton production, while phytoplankton primary production will be hampered due to increased light attenuation in the water. This, in turn, can decrease the production at higher trophic levels, since bacteria-based food webs in general are less efficient than food webs based on phytoplankton. However, complex environmental influences on the bacterial community structure and the large redundancy of metabolic functions limit the possibility of predicting how the bacterial community composition will change under climate change disturbances.

科学研究費補助金 研究種目:基盤研究(C)(2) 課題番号:10640474 研究代表者:吉岡 崇仁 研究期間:1998-1999年度