Abstract In this thesis, I studied the patterns in the assemblage composition as well as the biogeography and ecology of spring macroinvertebrates and bryophytes in Finland. My main objectives were to assess the importance environmental variables to macroinvertebrate and bryophyte assemblage composition in springs at the level of multiple spatial scales. In addition, I assessed the importance of springs in the boreal mire landscape, and sought the ecological and environmental determinants of a key species in boreal springs. In a large-scale study, I also examined the concordance between macroinvertebrates and bryophytes across boreal ecoregions, and assessed how macroinvertebrate assemblage variation corresponds to terrestrially-based ecoregions. Locally, spring macroinvertebrate assemblage structure displays high variation between different kinds of mesohabitats within springs, highlighting the importance of careful sampling of all habitat types in spring surveys. Helocrenes and other aquatic-terrestrial ecotone habitats harbour the highest species diversity and most spring-dependent species among spring habitat types. Further, spring-influenced mire patches were shown to have distinct cranefly assemblages in the mire landscape and to harbour higher cranefly diversity than mire types with lower trophic status, emphasising the importance of springs for mire biodiversity. Regionally, a red-listed spring-dependent caddisfly species appeared to be a surrogate for a high spring conservation value, indicating high overall species diversity and the occurrence of additional red-listed species. On a large geographical scale, intersecting the boreal ecoregions, a pattern of gradual change of benthic macroinvertebrate assemblage composition from south to north was detected, largely corresponding to terrestrially-derived ecoregions. However, the physical attributes of springs also need to be taken into account in bioassessment studies. Macroinvertebrate assemblage variation also correlated with physical habitat-scale variables, but not with changes in water chemistry. In contrast, spring bryophyte assemblages showed a distinct response to variation in water chemistry, but not to variation in physical habitat characteristics. Bryophytes and insect assemblages were concordant with each other on the large geographical scale, although the concordance was rather weak. Because of their different kind of responses to the physical and chemical variables, insects and bryophytes of springs are poor surrogates for each other in boreal springs.

For marine fishes, the early larval phase is considered a critical stage for survivorship and recruitment. The spatial and temporal dynamics of larval fish assemblages can influence their success and trophic structure of marine communities and entire ecosystems. This thesis will provide the first characterization of larval fish assemblage in the Strait of Georgia (SoG) in terms of diversity, abundance and composition, and their variability over multiple temporal scales, as well as the first quantification of variability in larval fish distribution in the SoG across multiple spatial scales. On the interdecadal scale, a significant decrease in larval abundance of several dominant fish taxa (Pacific hake, walleye Pollock, northern smoothtongue and rockfishes) contributed to a decline in total larval abundance and turnover in the composition structure between the early 1980s and the late 2000s. In contrast, both abundance and the relative composition of flatfishes and several demersal forage fish taxa increased during the same period. On interannual scales, abundance, diversity and community structure of the spring larval assemblages varied dramatically through 2007-2010, a period which alternated between strong La Niña and El Niño events. Higher overall larval concentrations were associated with warm conditions in the SoG in 2007 and 2010, while the lowest larval concentration was associated with cooler condition in 2009. Examination of associations between larval fish assemblages and environmental fluctuations suggests a potential influence of large-scale climate processes between the early 1980s and the late 2000s, but a primary association with local environmental factors on interannual scales. Spatial patterns in larval density of three dominant fish taxa (Pacific herring, Pacific hake and northern smoothtongue) were mostly structured on predefined broad (> 40km) and medium (20~40km) scales. Although their scale-dependent associations with environmental factors varied interannually, larval distributions in the central-southern SoG were generally associated with salinity, temperature and vertical stability of water column in the upper layer (0-50m). Our results emphasize the role of local estuarine circulation in structuring hierarchical spatial distributions of planktonic fish larvae in the SoG. These findings will provide considerable implications in fisheries resource management and conservation strategies. / Graduate / 0416 / 0329 / guanlu129@gmail.com

Made available in DSpace on 2016-06-02T19:26:21Z (GMT). No. of bitstreams: 1 PERESSIN_Alexandre_2013.pdf: 3061472 bytes, checksum: c6d89398da14de75e2b51d1412049dd6 (MD5) Previous issue date: 2013-04-05 / Universidade Federal de Minas Gerais / Aquatic ecosystems have suffered strong anthropogenic pressure, through the construction of dams, water exploitation, chemical pollution, destruction of the surrounding environment, especially riparian vegetation, and structural changes such as channeling and siltation. Fish assemblages may respond in different ways to these environmental changes, because species exhibit different constraints, e.g., habitat demands, physiological tolerance. Thus, some species may be favored in detriment of others. Aware of the need to understand and identify the patterns response of fish assemblages and individual organisms to impact factors, this study aimed to investigate how fish biodiversity (i.e., assemblages and population-scale) respond to urbanization. Fish samples were collected in four stretches located in urban areas and six located in non-urban areas of the upper Paranapanema river basin. Chapter I focused on detecting changes in physical habitat variables, structure and composition of the fish assemblage. Multivariate analyses ordered stretches in a urbanized non urbanized gradient. Non urbanized stretches exhibited greater values of shading, vegetated surronding and coarser substrate. Assemblage structure, i.e., Shannon diversity index, Pielou evenness and Margalef richness, did not change in response to urbanization, as well as the relationship between abundance and biomass. In contrast, assemblages composition was different, as well as richness estimates based on rare species, which was lower in urban stretches. The patterns herein obtained illustrate the process of species replacement, already demonstrated in disturbed environments, in which species pre-adapted to the new conditions increase in abundance, while otherspreviously absent establish successfully. Therefore, diversity values maintain, but composition varies. In general, midwater omnivorous species were more abundant in urban areas, while loricarids and benthic invertivores presented higher average abundance in nonurban stretches. Chapter II aimed to identify changes in the trophic structure, substrate composition and its influence on trophic structure and body condition. For this, species diet was quantified according to the Degree of Food Preference (DFP) method, based on six items: plant material, algae, detritus, invertebrates, insects and fish. According to the items consumed, species were classified in trophic groups. Fourteen species were considered invertivorous/detritivorous, seven herbivorous/detritivorous, seven omnivorous and one piscivorous. Four invertivores/insectivores were exclusive of nonurban stretches and one species exclusive of urban stretches. Three herbivores/detritivores were exclusive of the nonurban stretches, whereas three omnivores were exclusive to urban stretches. Trophic structure richness, abundance and biomass were compared between urban and nonurban stretches. Abundance was not affected by urbanization, whereas richness and biomass varied between stretch groups. Substrate composition differed according to stretch type, and was positively related to invertivores/insectivores and herbivore/detritivores richness, whereas negatively related to omnivore biomass. These results suggest complex relationships between food availability, trophic plasticity and species foraging habits. It is known that coarser substrates such as rocks, branches and trunks are useful as surface for periphyton algae growth as well as shelters for aquatic macroinvertebrates. Thus, changes in substrate may alter resources availability for certain species. Omnivores, in turn, can find other sources of food items due to its trophic plasticity. In general, almost all species absent from urban stretches exhibit some trophic specialization and often depend on heterogeneous substrate for foraging. Moreover, species exclusive to urban stretches are mid-water foragers that do not depend on substrate and present high trophic plasticity. Our conclusions were supported by Astyanax fasciatus body condition analysis, an omnivorous nektonic species which demonstrated higher mean weight in urban stretches, when discounted length. / Ecossistemas aquáticos têm sofrido forte pressão antropogênica, que se manifesta na construção de barragens, captação de água, poluição química, destruição do ambiente de entorno, principalmente mata ripária, e alterações estruturais como canalizações e aporte de sedimentos. A assembleia de peixes pode responder de diversas formas a estas alterações ambientais, dado que as espécies possuem diferentes exigências fisiológicas e de habitats. Com isso, algumas espécies podem ser eliminadas e outras favorecidas. Cientes da necessidade de compreender e identificar o padrão das respostas da assembleia e organismos aos vetores de impacto, neste trabalho buscamos investigar como a ictiofauna responde à urbanização. Para isso, os peixes foram coletados em quatro trechos localizados em áreas urbanas e cinco localizados em áreas não urbanas, sempre em riachos da parte superior da bacia do alto rio Paranapanema. O capítulo I buscou detectar alterações nas variáveis físicas do hábitat, na estrutura e na composição da assembléia de peixes. Utilizando as variáveis ambientais, os trechos foram ordenados no sentido urbanizado-não urbanizado, sendo que estes últimos apresentaram valores maiores de sombreamento, área, substrato e vegetação de entorno. Verificamos que a estrutura da assembleia, representada pelos índices de diversidade de Shannon, equabilidade de Pielou e riqueza de Margalef, não sofreu alterações em resposta à urbanização, bem como a relação entre abundância e biomassa. No entanto, a composição da assembleia foi diferente e a riqueza estimada com base nas espécies raras foi menor nos trechos urbanos. Simultaneamente, a variação nos componentes ambientais explicou a variação na composição da assembleia. Estes resultados evidenciam um processo de substituição de espécies descrito para ambientes alterados, no qual espécies pré-adaptadas às novas condições aumentam em abundância e outras antes ausentes se estabelecem. Assim, a diversidade é mantida, porém, alterando a composição. Em geral, espécie onívoras forrageadoras de meia água foram mais abundantes em áreas urbanas, ao passo que loricarídeos e invertívoros bentônicos apresentaram maior abundancia média em trechos não urbanos. No Capítulo II, o objetivo foi identificar alterações na estrutura trófica, composição do substratro, influência deste na estrutura trófica e condição corporal. Para isso, a dieta das espécies foi quantificada de acordo com o método do Grau de Preferência Alimentar (GPA) para seis itens: material vegetal, algas, detrito, invertebrados, insetos e peixe. De acordo com os itens consumidos, as espécies foram classificadas em categorias tróficas. Quatorze espécies foram consideradas invertivoras/detritívoras, sete herbívoras/detritívoras, sete onívoras e uma piscívora. Quatro espécies de invertívoros/insetívoros foram exclusivas de trechos não urbanos e uma dos urbanos. Três espécies herbívoras/detritívoras foram exclusivas de riachos do tipo não urbano, o inverso dos onívoros, com 3 espécies exclusivas de riachos do tipo urbano. A partir da classificação trófica, os trechos urbanos e não urbanos foram comparados quanto à estrutura trófica em relação à riqueza, abundância e biomassa. A abundância não foi alterada pela urbanização, no entanto a riqueza e a biomassa diferiram entre os tipos de riacho. A composição do substrato, que foi diferente entre os tipos de riacho, esteve positivamente relacionada com a riqueza de invertívoros/insetívoros, de herbívoros/detritívoros e negativamente relacionada com a biomassa de onívoros. Estes resultados ilustram um processo intrincado de relações entre a disponibilidade de alimentos, plasticidade trófica e hábitos de forrageamento das espécies. Sabe-se que substratos como rochas, galhos e troncos são úteis como superfície de crescimento de algas do perifíton e também como abrigos para macroinvertebrados aquáticos. Desse modo, alterações na composição do substrato podem modificar a disponibilidade de recursos para determinadas espécies, dependentes de algas e invertebrados aquáticos, especialmente insetos imaturos. Os onívoros, por sua vez, podem encontrar outras fontes de recurso devido a sua conhecida plasticidade trófica. De maneira geral, praticamente todas as espécies ausentes dos trechos urbanos possuem alguma especialização trófica e costumam ser dependentes do substrato para o forrageamento. Por outro lado, as espécies que ocorreram apenas nos trechos urbanos são forrageadoras de meia água, não depedentes do substrato e com alta plasticidade na dieta. Esta conclusão foi amparada pela análise da condição corporal de Astyanax fasciatus, um onívoro nectônico que, quando teve descontado o comprimento do corpo, apresentou maior peso médio nos trechos urbanos.