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Thesis (doctoral)--Universität Bremen, 2006. / Includes bibliographical references.

The benthic animals have important roles in benthic communities. Indicator organisms can tell things about a lakes status. Many of them are sensitive to acidification but there are also tolerant taxa. Some prefer eutrophic environments. The benthic fauna can therefore decide a lakes status since some species prefer different environments. The focus of this study was to compare benthic fauna within the littoral in the lakes Sidsjön and Vintertjärnen. They are situated a little south of Sundsvall, central Sweden and belong to the water system of Selångersån. The comparison was done at eight random locals in each lake at two occasions, during early and late summer to analyze if the benthic fauna differed between the two lakes and if it changed through the season. Five of the locals in each lake were protected and had soft bottoms and the remaining were exposed locals with hard bottom. Sidsjön is bigger than Vintertjärnen and has more variated bottom types so the biodiversity should be higher in Sidsjön. I also expect that the number of taxa should decrease during the later occasion due to hatchings. Three statistical analyses were done to see if these hypotheses were right or if they should be rejected. The two first analyses were ANOVA analyses, two-way with replication. The first ANOVA was for number of taxa and the second was for number of animals. The third analysis was a DCA analysis with the variables lakes, bottom types and emergent plants. ASPT index and Eq was also calculated and pH was measured during autumn for the lakes. The conclusion is that the there is no difference between the lakes but a significant effect when it comes to seasons according to the first ANOVA analysis. The second ANOVA analysis show that the lakes are not differing, that no factor is significant and there are no interactions. According to the DCA analysis there are differences between lakes and occasions when it comes to the variables. / <p>Datum för godkännande 2016-03-31</p>

<p>The aim of the study was to examine if the benthos in a restored portion of a small lowland stream south of Linkoping differed from two non</p><p>restored reference areas two years after restoration. The reference areas were one stretch downstream and one upstream stretches of the restored</p><p>stream. The benthic invertebrates were collected using standardized kick sampling. In order to classify the communities and estimate any</p><p>differences, three different indices were exercised. In addition rank-abundance curves and checklists were used to get a picture of species</p><p>composition. The only index that showed a difference between areas was the Berger-Parker diversity index showing that the downstream reference</p><p>stretch differed from the other two. None of the analyses showed that the restored area was different from the other two, probably due to too short</p><p>a time since the restoration. To allow for the bottom substrate to develop and stabilize so that species can re-colonize the area.</p>

Rivers are among the most anthropogenically affected ecosystems in the world by irrigation, transportation, channelizing, and hydropower. Habitat restorations have become a popular method to restore the heterogeneity and complexity of rivers aiming for improvement of biodiversity. In this master thesis, I studied the effects of restoration in a regulated and channelized river in the middle of Sweden. Differences in fish abundance and diversity together with hatching success and survival rate from egg to smolt of Seatrout (Salmo trutta) and Atlantic salmon (Salmo salar) were tested between restored and unrestored reaches. In addition, differences in abundance, biomass, diversity, and composition of benthic species between restored and unrestored areas were studied.  The study design consisted of three restored and three unrestored locations where artificial spawning grounds (redds) were placed, electrofishing was conducted, and an inventory of abundance, biomass and diversity metrics of benthic fauna was performed. Whitlock-Vibert boxes were used in the artificial redds and were used to calculate hatching success. The inventory of benthic fauna consisted of kick-sampling and sampling of stones followed by identification and measuring of length in the lab.  The findings in this study suggest that the survival of salmonids is not limited by the hatching success but that the lack of migration possibilities and the low survival rate from egg to smolt makes it unlikely with a successful reintroduction of Atlantic salmon and seatrout in Dalälven. Furthermore, one could argue that the habitat restorations have not increased the diversity of benthic fauna. However, it is possible that there is an ongoing shift in the benthic fauna towards a more diverse community in the restored areas and it is possible it will be more visible in a few years which supports maintaining long-term monitoring. Lastly, this study enlightens consequences with anthropogenically affected rivers and leaves opportunities for further studies.

The aim of the study was to examine if the benthos in a restored portion of a small lowland stream south of Linkoping differed from two non restored reference areas two years after restoration. The reference areas were one stretch downstream and one upstream stretches of the restored stream. The benthic invertebrates were collected using standardized kick sampling. In order to classify the communities and estimate any differences, three different indices were exercised. In addition rank-abundance curves and checklists were used to get a picture of species composition. The only index that showed a difference between areas was the Berger-Parker diversity index showing that the downstream reference stretch differed from the other two. None of the analyses showed that the restored area was different from the other two, probably due to too short a time since the restoration. To allow for the bottom substrate to develop and stabilize so that species can re-colonize the area.

Metal pollution from Acid Mine Drainage (AMD) is one of the most serious environmental challenges associated with mining operations as well as a potential threat to biological life. Effects of AMD from mining regions are site-specific and depend on several biotic and abiotic factors in the recipient waters. The aim of this thesis was to assess the effects of metals (As, Cd, Cr, Cu, Ni, Pb, U, Zn) on mayfly (Ephemeroptera) larvae presence in recipient waters in Norr- and Västerbotten counties, Sweden. To fulfil this aim I used data from recipient surveys that has sampled benthic fauna with the kick-net method and collected water samples for chemical analysis. Regression analyses were performed to determine the relationships between dissolved and bioavailable concentrations of Cu, Ni, Pb and Zn. Additional regression analyses were performed to assess the relationships between the dissolved concentration of each metal and number of mayfly species as. Lastly, a regression analysis was performed for number of mayfly species and water pH. Results revealed that the number of mayfly taxa decreased exponentially as metal concentrations increased. There was also a correlation between number of mayfly taxa and pH, with the highest number of species in the pH interval 6,7 – 7,7. The ability to draw any definitive conclusions about the effects of metal pollution on mayflies in this geographical area are complicated by water pH, which for some sites is quite low. Further studies may be needed to determine how much of the effect can be attributed to high metal concentrations and how much is a consequence of low water pH.

Dams are a typical example of how watercourses are being used, especially for production of electricity. Negative consequences that follows are that the character of the watercourse is altered, which in turn affects the composition of organisms. In the summer of 2017, a hydroelectric plant was removed in Nianån. A project started with the purpose to investigate the effects on benthic fauna, one year after the removal. In this study, the watercourse Gnarpsån was also used as a control. It was assumed that the proportion of silt and sand, as well as the water depth had decreased while the water velocity had increased in the habitat of the former reservoir in Nianån. It was also assumed that a change in the density of the benthic fauna should have occurred in Nianån, downstream in the riffle. The abundance of organisms with a burial lifestyle should have decreased in the habitat of the former reservoir, while the abundance of scrapers and filters should increase in the riffle. The result showed few significant physical changes. A difference in substrate composition could be seen in Nianån, however it was the proportion of fine substrates that increased in all habitats (gravel, fine gravel and sand). The water velocity was unchanged in Nianån, and the depth only decreased in the flowing habitat upstream. In both watercourses, 38 different families of macroinvertebrates were found. The proportion of burial animals in the habitat of the former reservoir decreased significantly, but no change in the total density was found. A possible effect may already have been recovered, or more time may need to pass before expected results can be seen. Many factors affect the conditions in the watercourses. To be able to provide better general predictions about the effects of dam removal, further studies are needed, both at the organism level and with a large-scale approach to get a uniform picture of this restoration measure. / Dammar är typiska exempel på hur vattendrag utnyttjas, framförallt för elproduktion. Negativa följder är att vattendragets karaktär förändras, vilket i sin tur påverkar sammansättningen av organismer. Sommaren 2017 togs ett kraftverk bort i Nianån. Ett projekt startade med syftet att undersöka effekterna på bentisk fauna ett år efter dammutrivningen. I denna studie används också vattendraget Gnarpsån som en kontroll. Det antogs att andelen silt och sand, samt vattendjupet hade minskat medan vattenhastigheten hade ökat i habitatet i den före detta regleringsdammen i Nianån. Det antogs även att en förändring av tätheten av bottenfauna borde ha skett i Nianån, nedströms i torrfåran. Andelen nedgrävande djur borde ha minskat i habitatet i den före detta regleringsdammen, medan andelen skrapare och filtrerare ökat i torrfåran. Resultatet visade på få signifikanta fysiska förändringar. En viss skillnad i substratsammansättning kunde ses i Nianån, dock var det andelen fint substrat som ökat i samtliga habitat (grus, fint grus och sand). Vattenhastigheten var oförändrad i Nianån, och djupet minskade endast i det strömmande habitatet uppströms. I vattendragen återfanns 38 olika familjer av makroevertebrater. Andelen nedgrävande djur i habitatet i den före detta regleringsdammen minskade signifikant, men någon förändring i total individtäthet påvisades inte. En eventuell effekt kan redan ha återhämtats, eller så behöver mer tid gå innan förväntade resultat kan ses. Många faktorer påverkar förhållandena i vattendragen. För att kunna ge bättre generella förutsägningar om effekter av dammutrivning behövs vidare studier, både på organismnivå och med ett storskaligt synsätt för att få en enhetlig bild över denna restaureringsåtgärd.