In Ethiopia industrial effluents containing high contents of organic matter, nitrogen and heavy metals are discharged into inland surface waters with little or no pre-treatment. Significant pollution concerns related to these effluents include dissolved oxygen depletion, toxicity and eutrophication of the receiving waters. This has not only forced the government to formulate regulations and standards for discharge limits but also resulted in an increasing interest and development of methods and systems by which wastewater can be recycled and used sustainably. The need for technologies for environmentally friendly treatment of industrial wastes such as tannery wastewaters is therefore obvious. Biological processes are not only cost effective but also environmentally sound alternatives to the chemical treatment of tannery wastewaters. The aim of the research presented in this thesis was to develop and optimize processes for biological nitrogen removal from tannery wastewaters and to identify the most efficient denitrifying organisms in tannery wastewaters laden with toxic substances. A pilot plant consisting of a predenitrification anoxic system, aerated nitrification compartment and a sedimentation tank (clarifier) all arranged in series was developed and installed on the premises of Addis Ababa University, Ethiopia. In spite of high influent chromium and sulphide perturbations over the successive feeding phases, the performance of the pilot plant was encouraging. The overall removal efficiency of the pilot plant over the experimental feeding phases varied between 82-98% for total nitrogen, 95-98% for COD, 96-98% for BOD5, 46-95% for ammonia nitrogen, 95-99% for sulphide and 93-99% for trivalent Chromium. Six isolates from over 1000 pure cultures were identified as the most efficient denitrifying bacteria. From both cellular fatty acid profiles and 16S rRNA gene sequencing, the six selected strains were phylogenetically identified as Brachymonas denitrificans in the β-subdivision of the Proteobacteria. All the six strains contain cd1-type nitrite reductase. The efficient isolates characterized in this study are of great value because of their excellent denitrifying properties and high tolerance to the concentrations of toxic compounds prevailing in tannery wastewaters. Bio-augmentation of the pilot plant with this bacterium showed a clear correlation between in situ denitrifying activities measured by nitrate uptake rate, population dynamics of the introduced B.denitrificans monitored by fluorescent in situ hybridization and the pilot plant performance, suggesting that the strategy of introducing this species for enhancing process performance has potential applications. Moreover, the nitrate-reducing, sulphur-oxidizing bacteria (NR-SOB) were also found in the pilot plant in abundance with steady sulphide removal efficiency during the study period. This could provide opportunities for the application of biologically mediated simultaneous removal of sulphide and nitrogen from tannery effluents. In addition to enriching high consortia of denitrifiers in the anoxic system to attain high denitrification efficiency and also improving the overall nitrification efficiency of the system, the predenitrification-nitrification pilot process plant stimulated the activity of indigenous NR-SOB to simultaneously remove sulphide from the system. Thus, the pilot plant was found to be operationally efficient for the removal of nitrogen, organic matter and other pollutants from tannery wastewaters. Keywords: Biological nitrogen and sulphide removal, denitrifying bacteria, nitrate-reducing, sulphur-oxidizing bacteria, nitrate uptake rate, fluorescent in situ hybridization, pollution, tannery effluents.

The aim of this Thesis was to improve our understanding and assessment of feeding conditions for zooplanktivorous fish in the Baltic Sea. We investigated (papers I, II) the usefulness of biochemical proxies for assessments of growth and metabolic rates in the dominant Baltic copepod Acartia bifilosa. A predictive model (paper I) for egg production rate (EPR), based on body size, RNA content, and water temperature, was established using females of different geographical origin. This model demonstrates the usefulness of RNA content as a proxy for growth in zooplankton and, together with abundance data, it could be used to evaluate fish feeding conditions. Further (paper II), using A. bifilosa exposed to a food gradient, we evaluated responses of physiological rates and other biochemical proxies for growth and established correlations between physiological and biochemical variables. EPR and ingestion rate were most significantly correlated with RNA content. As assayed variables saturated at different food concentrations, food availability may affect assessments of physiological rates using proxies. In paper III, we explored the effect of high EPR and ingestion rate on astaxanthin content in A. bifilosa. We found that the astaxanthin content decreased at high feeding rates, most likely due to decreased assimilation efficiency. This may impact the quality of zooplankton as prey. The invasion of Cercopagis pengoi, a zooplanktivorous cladoceran, has altered the trophic linkages in the Baltic Sea food web. In paper IV, we evaluated the feeding of zooplanktivorous fish on C. pengoi and found that irrespective of size both herring and sprat feed on it, with large herring being more selective. In turn, C. pengoi feeds mainly on older copepods (paper V), which are acknowledged important in fish nutrition. These results indicate that C. pengoi may compete with fish due to the diet overlap. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In progress. Paper 3: Submitted</p>

In this thesis I examine and evaluate the effects of a documented large-scale eutrophication on macroalgal vegetation on the Swedish coast. During the past century the load of nutrients has increased manifold in the Baltic Sea area, increasing primary production and organic sedimentation significantly. By re-investigating a unique reference material of macroalgal vegetation from the 1940-60s and by conducting new diving studies at the same sites, I showed that long-term trends in macroalgal community composition and species’ distributions are consistent with changes expected from an increased nutrient availability. In the Öregrund archipelago (northern Baltic Sea), I documented a declined depth distribution of the dominant canopy forming alga, Fucus vesiculosus, and an increased abundance of opportunistic ephemeral algae compared to 52-53 years ago. In the Gullmar Fjord area (Skagerrak), trends included increased abundances of functional groups with opportunistic algae, decreased abundances of large perennial algae and a general decline in the depth distribution of the vegetation compared to 36-57 years ago. Sediment removal experiments in the northern Baltic Sea confirmed the hypothesis that sedimentation influences macroalgal community composition. Species depending on short periods of reproduction were clearly favoured by sediment removal, especially F. vesiculosus that seemed limited in depth by the local sediment load. Species with long continuous periods of dispersal by spores and/or fragments (for example the ephemerals Cladophora glomerata, Ceramium tenuicorne and Enteromorpha spp.) were more tolerant to the natural sediment load. In general, sediment removal favoured macroalgal establishment and development, indicating that variation in the natural sediment load is an important constraint for sublittoral rocky-shore macroalgal community development. I conclude by suggesting that the documented long-term changes in macroalgal vegetation on the Swedish coast partly are explained by an increased organic sedimentation in these areas.

The main aim of this work was to identify local adaptation processes in amphibian populations, thereby improving the general understanding of genetics and mechanisms behind the evolution and maintenance of biological diversity. Phenotypic and genetic variation in life-history traits was studied within and between populations common frog (Rana temporaria) populations along a 1600 km transect from southern Sweden to northern Finland. Embryonic and larval development and growth was investigated both under field and laboratory conditions. The results suggest ample genetic diversity in larval life-history traits among Fennoscandian common frog populations. Larval developmental rate along the gradient has evolved a countergradient variation pattern of genotypes and phenotypes as indicated by the positive relationship between developmental rate and latitude under laboratory conditions and the lack of such a relationship in the field. The data suggest that this pattern has evolved because of time constraints due to decreasing length of growth season with latitude. Neither field-caught adults nor laboratory raised larvae displayed a linear latitudinal size cline as expected from the so called Bergmanns rule. Rather, size increased towards the mid-latitude populations and decreased thereafter, indicating that body size is a product of direct environmental induction or a trade-off with other life-history characters. Age and size at hatching showed no consistent latitudinal pattern, indicating that the embryonic stage is not as time constrained as the larval stage. A large part of the variation in age and size at metamorphosis among populations was due to additive genetic effects. However, small, but significant maternal effects, mostly due to variation in egg size and non-additive genetic effects also contributed to among population variation. A comparison of divergence in presumably neutral molecular genetic markers (FST) and quantitative characters (QST) revealed that although both estimates of divergence were relatively high, estimates of QST was generally higher than those of FST, indicating that the genetic variation observed in larval traits is primarily a result of natural selection rather than genetic drift. Hence, our results reinforce the conclusion that intraspecific genetic heterogeneity in the young northern European ecosystems may be more widespread than previously anticipated

Lichens are fascinating symbiotic systems, where a fungus and a unicellular alga, most often green (bipartite green algal lichens; 90% of all lichens), or a fi lamentous cyanobacterium (bipartite cyanobacterial lichens; 10% of all lichens) form a new entity (a thallus) appearing as a new and integrated organism: in about 500 lichens the fungus is associated with both a cyanobacterium and an alga (tripartite lichens). In the thallus, the lichen bionts function both as individual organisms, and as a symbiont partner. Hence, in lichens, the participating partners must both be able to receive and acquire resources from the other partner(s) in a controlled way. Lichens are particularly successful in harsh terrestrial environments. In part this is related to their poikilohydric nature and subsequent ability to repeatedly become desiccated and hydrated. Metabolic activity, i.e. photosynthesis, respiration, and for cyanobacterial lichens N2-fixation, is limited to periods when the thallus is suffi ciently hydrated. Mineral nutrients are mainly acquired from dry or wet deposition directly on the thallus. Taken together it then appears that lichens are to a large extent passively controlled by their environment, making their control over resource allocation and acquisition particularly challenging. The aim of this thesis was to investigate resource acquisition and allocation processes in different lichens, and to see how these respond to changes in resource availability. This was done by following lichen growth in the fi eld during manipulation of water, light, and nutrient supply, and by assessing the responses of both the integrated thallus as well as the individual bionts. As a fi rst step, resource allocation and acquisition was investigated for a broad range of lichens aiming to determine the magnitude of metabolic variation across lichens. Seventy-fi ve lichen species were selected to cover as broad a spectrum as possible regarding taxonomy, morphology, habitat, and nitrogen requirements. The lichens had invested their nitrogen resources so that photosynthetic capacity matched respiratory carbon demand around a similar equilibrium across the contrasting species. Regulation of lichen growth was investigated in another study, using the two tripartite species Nephroma arcticum and Peltigera aphthosa, emphasizing the contribution of both internal and external factors. The empirical growth models for the two lichens were similar, showing that weight gain is to a higher extent dependent on those external factors that regulate their photosynthesis, whilst area gain is more controlled by internal factors, such as their nitrogen metabolism. This might be inferred from another study of the same species, where nitrogen manipulations resulted in an undisturbed weight gain, a similar resource allocation pattern between the bionts, but a distorted area gain. Aiming to investigate lichen nitrogen relations even further, lichens’ capacities to assimilate combined nitrogen in the form of ammonium, nitrate and amino acids were assessed using 14 contrasting boreal species. All these had the capacity to assimilate all the three nitrogen forms, with ammonium absorption being more passive, and nitrate uptake being low in bipartite cyanobacterial lichens. Differences in uptake capacities between species were more correlated to photobiont than to morphology or substrate preferences. Finally, to investigate intra-specifi c plasticity in relation to altered nutrient supply, resource investments between photo- and mycobiont were investigated in the two bipartite green algal lichens Hypogymnia physodes and and Platismatia glauca in a low and a high nutrient environ- in a low and a high nutrient environ- ment. In both species, more of the resources had been directed to the photobiont in the high nutrient environment also increasing their overall carbon status. Taken together, my studies indicate that in spite of the apparent passive environmental control on lichen metabolism, these symbiotic organisms are able to both optimize and control their resource acquisition and allocation processes.

Multiple mating by females is common in nature. Yet, the evolution and maintenance of polyandry remains a bit of an evolutionary puzzle. It was my aim in this thesis to reach a greater understanding of this phenomenon as well as to investigate the consequences of polyandry on the evolution of reproductive divergence in insects. In an extensive meta analysis addressing the direct effects of multiple mating on female fitness in insects, I found that insects gain from multiple matings in terms of increased lifetime offspring production. In species without nuptial feeding, increased mating rate leads to decreased female lifespan and my results strongly support the existence of an intermediate optimal female mating rate. However, results from an experimental study where I examined the relationship between female fitness and mating rate in the bean weevil (Callosobruchus maculatus) showed that female fitness was maximized at two alternative mating rates, indicating that some species may exhibit a more complex relationship between the costs and benefits of mating. In the meta analysis on species with nuptial feeding, I found only positive effects of increased mating rate and the puzzle is rather what constrains the actual mating rates of females in these groups. Sexual selection is a very potent driver of rapid evolutionary change in reproductive characters. Most research has focussed on precopulatory sexual selection, but in promiscuous species sexual selection continues after copulation and variance in male fertilization success gives rise to postcopulatory sexual selection. In this thesis I found that three allopatric populations of the red flour beetle (Tribolium castaneum) have diverged in traits related to reproduction. Male genotype affected all aspects of female reproduction, but more interestingly, males and females interacted in their effect on offspring production and reproductive rate, showing that the divergence was due to the evolution of both male and female reproductive traits. When studying postcopulatory sexual selection, sperm competition has been put forward as the main source of variance in fertilization success. The results from a set of double-mating experiments, using the same populations of flour beetles, provided strong evidence that cryptic female choice is also important in generating variance in male fertilization success. I found not only main effects of female genotype on male fertilization success but also male-female interactions which provide more unambiguous evidence for cryptic female choice. Finally, I attempted to uncover which male signals-female receptors are involved in the reproductive divergence observed in the Tribolium populations. In a double-mating experiment I manipulated female perception of two male reproductive signals, copulatory courtship and cuticular hydrocarbons, and the results indicate that, within populations, both signals are sexually selected. However, only male cuticular hydrocarbons seem to be involved in the reproductive divergence between the populations. In conclusion, multiple mating by female insects can be understood solely in terms of direct fitness benefits resulting from increased offspring production. I have shown that postcopulatory sexual selection can lead to rapid divergence in reproductive traits related to mating and that cryptic female choice plays an important role in this divergence.

Temporal and spatial variations of pelagic microorganisms in the northern Baltic Sea were studied, as well as factors influencing their abundance and growth rates. Three main questions were asked 1) How does increased productivity influence the structure of the microbial food web? 2) Does predation limitation vary between trophic levels? 3) What is the relative importance of resource and predation limitation at different trophic levels? A field study in the northern Baltic Sea showed that dominating protozoa, flagellates and ciliates, increased with increasing primary productivity from north to south. Furthermore, relatively small protozoan cells dominated in the low productive north, while larger cells became more dominant in the south. The relationship between plankton size structure and productivity was further studied in an experimental system. In agreement with present theories regarding nutrient status of pelagic food webs, increased productivity caused a lengthening of the food chain as well as a change in plankton size structure. While microplankton dominated in nutrient rich treatments pico- and nanoplankton dominated during nutrient poor treament. The flagellate community was dominated by a potentially mixotroph, Chrysochromulina sp., at low nutrient concentrations. To our knowledge this is the first experimental study showing that Chrysochromulina sp. in resemblance with other mixotrophs is favoured by nutrient poor conditions compared to strict autotrophs and heterotrophs. During a stratified summer period autotrophic microorganisms in the northern Baltic Sea did not respond to removal of potential predators, indicating that they were primarily limited by inorganic nutrients. An exception was small eucaryotic picoplankton that showed a large response to predator removal. Among the heterotrophic microorganisms direct effect of predation seemed to increase from ciliates, heterotrophic bacteria, small heterotrophic flagellates, medium flagellates to large flagellates. No quick indirect effect was observed, but after four days trophic cascades were detected. The relative importance of resource and predation limitation was studied among heterotrophic bacteria, flagellates and ciliates in the northern Baltic Sea. For all these groups, resource limitation seemed to prevail during the summer period. The results also indicated that the relative importance of predation increased with the productivity of the system. To our knowledge there are no earlier measurements on the relative importance of resource and predation limitation for micoorganisms in the pelagic environment.

This thesis examines the relative importance of local conditions, dispersal and dynamics of the trees on epiphyte distribution patterns and colonization-extinction dynamics. Study species are the mosses Orthotrichum speciosum and O. obtusifolium, and the red-listed Neckera pennata. The thesis also includes an attempt to parameterize a model for a lichen metapopulation (Lobaria pulmonaria) in a dynamic landscape, based on only presence/absence data of the epiphyte and its host trees. The results show that epiphyte colonization of trees is affected by both local conditions, and by connectivity to occupied trees. The positive effect of connectivity, implying a restricted dispersal range, was established by both demographic and genetic studies. The important local conditions were tree diameter and vitality, and shade. Local extinctions from trees occurred among small trees with low local epiphyte abundance, but more often, were the results of tree fall. The observed importance of connectivity on epiphyte colonization agrees with the assumptions of the classic metapopulation model. However, the classic metapopulation model assumes that the landscape is static, and that local extinctions occur for stochastic reasons. The dynamics of epiphytes are different. A new conceptual model is therefore suggested, the patch-tracking metapopulation model. It differs from the classic metapopulation model in that it includes dynamics of the patches, and in that local extinctions only occur as patches are destroyed. Simulations of the dynamics of N. pennata showed that its future metapopulation size will be overestimated unless the dynamics of the trees are accounted for. The simulation results further suggest that the dynamics of N. pennata can be characterised by the patch-tracking metapopulation model. The attempt to parameterize the L. pulmonaria metapopulation model showed that more information are required for rigorous parameterization, preferably of the past historic fire regime.

Biological invasions are an important issue of global change and an increased understanding of invasion processes is of crucial importance for both conservation managers and international trade. In this thesis, I have studied the invasion of the brown seaweed Fucus evanescens, to investigate the fate and effect of a perennial, habitat-forming seaweed introduced to a coastal ecosystem. A long-term study of the spread of F. evanescens in Öresund (southern Sweden) showed that the species was able to expand its range quickly during the first 20 years after the introduction, but that the expansion has been slow during the subsequent 30 years. Both in Öresund and in Skagerrak, the species is largely restricted to sites where native fucoids are scarce. Laboratory experiments showed that the restricted spread of F. evanescens cannot be explained by the investigated abiotic factors (wave exposure and salinity), although salinity restricts the species from spreading into the Baltic Sea. Neither did I find evidence for that herbivores or epibiota provide biotic resistance to the invader. On the contrary, F. evanescens was less consumed by native herbivores, both compared to the native fucoids and to F. evanescens populations in its native range, and little overgrown by epiphytes. Instead, the restricted spread may be due to competition from native seaweeds, probably by pre-occupation of space, and the establishment has probably been facilitated by disturbance. The studies provided little support for a general enemy release in introduced seaweeds. The low herbivore consumption of F. evanescens in Sweden could not be explained by release from specialist herbivores. Instead, high levels of chemical anti-herbivore defence metabolites (phlorotannins) could explain the pattern of herbivore preference for different fucoids. Likewise, the low epibiotic colonisation of F. evanescens plants could be explained by high resistance to epibiotic survival. This shows that colonisation of invading seaweeds by native herbivores and epibionts depends on properties of the invading species. The large differences between fucoid species in their quality as food and habitat for epibionts and herbivores imply that invasions of such habitat-forming species may have a considerable effect on a number of other species in shallow coastal areas. However, since F. evanescens did not exclude other fucoids in its new range, its effect on the recipient biota is probably small.

This thesis is a summary of enclosure and microcosm experiments that aimed to study the impact of allochtonous subsidies on food web dynamics in a heterogeneous food web. In the enclosure studies, a three trophic level littoral food web was used. The food web consisted of two growth forms of primary producers: phytoplankton and periphyton and their associated herbivores: scraping and filtering herbivores. The predator used, YOY perch, affects both pathways in the food web. Manipulation of the openness for the different trophic levels showed that the inflow of phytoplankton and cross-habitat foraging by the herbivore level reinforced the compensatory response between the two growth forms of primary producers In the microcosm experiment, the response of an herbivore food web and a microbial community to inflow of resources and food web configuration was studied, using a model food web. The model food web consisted of two forms of primary producers, i.e. phytoplankton and periphyton, and two herbivores, i.e. Daphnia pulex feeding on phytoplankton, and Chydorus sphaericus feeding on both periphyton and phytoplankton. Three different food web configurations, all having the phytoplankton and periphyton, but either one of the herbivores, or both, were set up. The flow regimes consisted of an open treatment receiving a constant supply of phytoplankton, and a closed treatment with an initial resource pool. The effect of the inflow of phytoplankton was affected by the food web configuration. In the presence of D. pulex, the inflow of phytoplankton was made accessible to periphyton, and indirectly to C. sphaericus, which increased to such high densities that D. pulex was negatively affected. The inflow of phytoplankton had an indirect negative effect on the microbial community, since the biomass of herbivores increased, which imposed a higher grazing pressure on all parts of the microbial community.