No description available.

Apis mellifera is an important pollinator for agriculture, with a large distribution across the globe, generalist feeding behaviour, and high efficiency as a pollinator. The recent decline of Apis mellifera is affected by deforestation, climate change, spillover of pathogens, and a high demand for honey. The gut microbiota of honey bees can be a key to improving the health of the colonies and stopping the decline. This project aims to determine whether the gut microbiota of honey bees changes over winter and analyze the similarities and differences in the gut microbiota of the Apis mellifera mellifera subspecies by comparing samples collected in early autumn and spring. The study will specifically focus on the impact of the honey bee's diet, which varies between honey and sugar-water intake. This was accomplished by sequencing the 16S rRNA gene using nanopore sequencing technology. As a result, it was determined that the gut microbiota changes during the winter season, and Bartonella may play a crucial role in honey bees’ well-being in winter. The honey-fed group contained the most diverse bacterial composition, including species that were not determined in the sugar-fed and reference groups. Thus, it is believed, the diet affected the gut microbiota composition. The honey-fed group also contained a novel species Novisyntrophococcus fermenticellae, which was not previously found in honey bees.

Honey bee are immensely important pollinators, but their numbers are in decline due to both known pathogens, such as Nosema ceranae and Varroa destructor, and the yet not fully understood phenomenon called Colony Collapse Disorder. The overwintering process is straining for the hive and is a time where many hives are lost, therefore it is of importance to understand how to best care for the colonies during this time. This study was performed to try to determine how the composition of the intestinal microbiome of the Buckfast hybrid of the honey bee, Apis mellifera, living in Sweden, changes from autumn to during overwintering and if the diet affects the composition of the intestinal microbiome during overwintering. The composition of the intestinal microflora was investigated through Nanopore sequencing of the 16S rRNA gene. The data clearly indicates a shift in the composition of the intestinal microbiome from autumn to during overwintering in the form of declining abundance of the genera Lactobacillus, Bombilactobacillus, Gilliamella and Frischella, and an increasing abundance of the Bartonella genus. The data also clearly reveals that diet does affects the composition of the intestinal microbiome, with the group being fed a substituted diet of sugar-water having more species of and a larger abundance of opportunistic bacterial colonizers compared to the group being fed a natural diet of the colonies own produced honey. The data also shows that the individuals within the group being fed sugar were less homogenous than those that were fed honey.

The reproductive potential of an organism, also known as fecundity, is determined by several factors. In fish, theory suggests that individual size would have the strongest influence on both the number of eggs and the size of eggs. In turn, there are also several factors influencing individual size. I tested how individual size, growth, size distribution and population density in seven single species populations of brown trout (Salmo trutta) influence both individual fecundity and population fecundity in seven small oligotrophic lakes located near Stekenjokk. The field work was conducted in the summer of 2021 by Pär Byström with colleagues where brown trout were caught with gillnets. My results show that individual size and growth had an influence on both the number of eggs as well as the size of the eggs while population density did not. This is suggested to be a result of either a trade-off between the number and size of eggs or possibly a display of the higher metabolic cost following being a large sized brown trout.

Urbanization presents some serious challenges to stream ecosystems, frequently leading to degradation of water quality and loss of biodiversity. To mitigate these impacts, restoration efforts have been implemented worldwide. However, the effectiveness of such restoration projects in high latitude urban streams remains poorly understood. I investigated the influence of restoration on high latitude urban streams by comparing the ecological conditions, using macroinvertebrates as indicators within urban unrestored streams, urban restored streams, and forested streams within and around Umeå, Sweden. My results indicate no significant difference between urban and urban restored streams in terms of key parameters, including water chemistry as well as macroinvertebrate community abundance, richness, and biomass. By comparison, both categories of urban streams were generally distinct from forested counterparts. In particular, the abundance and biomass of insects within the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) were notably elevated in forested streams, were driving forces of the dissimilarity between these and urban streams and were negatively correlated with measures of nutrient enrichment and acidity across sites. By comparison, community biomass in urban streams tended to be dominated by isopods. Overall, my results indicate that efforts to modify or restore urban stream had little influence on benthic communities. However, stream restoration in this case was done largely to 1) provide flood prevention and 2) be aesthetically pleasing, which are also relevant goals. Nevertheless, my findings underscore the complexity of restoring urban streams and highlight the need for further research to improve restoration strategies tailored to these environments.

Benthic macroinvertebrates are usually small animals living in our lentic and lotic ecosystems, they have been used as indicators of water quality and biodiversity for a long time. Dam removals have become one of the “go-to” conservation methods for restoring connectivity in lotic ecosystems and thereby enabling passage upstream for migrating species. In Sweden, a large part of rivers and streams have dams present which act as migration barriers. Hushållningssällskapet Halland runs a project, LIFE-Goodstream in which a dam considered a migration barrier was removed in the stream Trönningeån. This report has three focus areas 1) the ecological effects of the dam removal while 2) considering the effect on the species composition of the orders Ephemeroptera (Mayflies), Plecoptera (Stoneflies), Trichoptera (Caddisflies) and Odonata (Dragonflies) in the stream Trönningeån with two tributaries and finally 3) suggest appropriate conservation methods for the future. By examining the benthic macroinvertebrate community our study showed that a small dam removal can have a clear positive effect on water quality, changing the water status classification from low water quality to high. Although there was no effect on the species diversity by the dam removal, a turnover in species composition became obvious after the examination. Moreover, we learned that Trichoptera was the most present order in two out of the three streams while Odonata was the least represented order. Also, bottom substrate, velocity and riparian zone have larger impact on species composition than adjacent environments. Re-meandering streams to further increase biodiversity while also ensuring water quality, is an essential method for a thriving conservation work in the future.

<p>Med rysk sammanfattning</p>

The pike (Esox lucius) is a major predator and top-down regulator in the Baltic Sea where it exists in two sympatric forms. One spawn in streams and rivers and the other one spawn in the sea. During the last decades, the habitats for both of these forms have developed in a negative way. In some freshwater systems, up to 90 % of the water areas have disappeared, mainly through drainage and straightening of watercourses for agricultural purposes. In the sea, reproduction habitats decrease due to construction of harbours and human activities that create disturbances. The perhaps largest single factor negatively affecting recruitment of pike in the sea is the eutrophication. Bottoms are overgrown with filamentous algae and shallow bays are covered with dense Phragmites belts decreasing the habitats suitable for spawning. Further on, a predator on egg and fish larvae, the three-spined stickleback (Gasterosteus aculeatus) has increased in abundance. It is difficult to restore and enhance pike production in the sea and probably the only economically viable alternative is to make restorations in freshwater. However, there is a limited knowledge about the freshwater spawning pike in the Baltic Sea. Thus in this thesis I, together with my coauthors, set out with an aim to increase the knowledge base regarding anadromous pike behaviour. We found that pike of natal freshwater origin were common in the Baltic Sea. Through Sr:Ca studies in otoliths, about 45 % of the pike were interpreted to be of freshwater origin. The majority of the pike had emigrated out of freshwater at a length below 6 cm. These results indicate that freshwater recruitment is successful, contrasting the vast areas available for spawning in the sea. This creates incitements that restoration measures in these watercourses could have a significant effect on the pike population in the Baltic Sea. Further, in four streams running out in the Baltic Sea, more than three thousand pike were marked to study spawning migration. About 30-40 % returned to the same river the subsequent year. Most of the pike used the lower parts of the stream for spawning. The homing of pike to a watercourse indicate that freshwater pike in the Baltic Sea consist of specific populations and this is crucial information when taking decisions on fish restoration measures. Three wetlands adjacent to streams were restored for pike production. The most successful restoration involved minimal digging, with flooded grasslands providing optimal conditions for spawning. The first spawning season after restoration increased the pike production hundredfold. In conclusion, the anadromous pike are numerous in the Baltic Sea. To compensate for the decline in pike populations in the sea, “pike-factories” created along the coastline are probably the most justifiable option.

No description available.

<p>Rates of habitat alteration and degradation are increasing worldwide due to anthropogenic influence. On coral reefs, the loss of live coral reduces structural complexity while facilitating algal increase. In many coastal lagoons seagrass and corals are cleared to make room for cultivated macroalgae. This thesis deals with reef and lagoon habitat structure and how fish assemblage patterns may be related to physical and biological features of the habitat. It further examines assemblage change following habitat disturbance. Four studies on East African coral reefs concluded that both the abundance and species richness of recruit and adult coral reef fish were largely predicted by the presence of live coral cover and structural complexity (Papers I-III, VI). Typically, recruits were more selective than adults, as manifested by limited distributions to degraded sites. Paper VI compared short- and long-term responses of fish assemblages to the 1997-1998 bleaching event. The short-term response to coral mortality included the loss of coral dwelling species in favour of species which feed on algae or associated detrital resources. Counterintuitively, fish abundance and taxonomic richness increased significantly at one of two sites shortly after the bleaching. However, the initial increase was later reversed and six years after the death of the coral, only a limited number of fish remained. The influence of fleshy algae on fish assemblages was studied in algal farms (Paper IV), and examined experimentally (Paper V). The effects of algal farming in Zanzibar were significant. Meanwhile, manually clearing algal-dominated patch reefs in Belize from macroalgae resulted in short-term increases of abundance, biomass and activity of a few species, including major herbivores. The findings of this thesis demonstrate the significance of habitat as a structuring factor for tropical fish assemblages and predicts that coral death, subsequent erosion and algal overgrowth may have substantial deleterious impacts on fish assemblage composition, abundance and taxonomic richness, with recovery being slow and related to the recovery of the reef framework.</p>