A diverse cocktail of pharmaceuticals is spreading via water treatment plants’ effluent to surface water with known and unknown consequences of individual organisms and the ecosystem. In prior research on what consequences the pharmaceutical discharge can have, the antihistamine diphenhydramine has been found in surface waters and has been linked to alteration in organisms’ behaviours. In this study, Dytiscidae larvae were filmed before and after being exposed to diphenhydramin with a concentration of 1 µg/l. The exposure was done using four different treatments: no diphenhydramine, diphenhydramine in water, in their food or in both water and food. This was done to observe whether the behaviour, specifically activity and boldness, of Dytiscidae larvae would change with the exposure of the antihistamine and therefore potentially be a problem in aquatic ecosystems exposed to effluent. The experiment showed a significant difference (P = 0.015) between larvae in the control group and larvae only exposed to diphenhydramine through water, where exposed larvae were less active than the control group. Also, a trend pointed to a potential difference in exploration between the same groups, where the group exposed to diphenhydramine explored more than the control group. No behavioural change was found when larvae was exposed via food or food and water. The changed behaviour found here could influence fitness of the larvae and potentially also other parts of the ecosystem through cascading effects. Further research is required to confirm the dangers and consequences of diphenhydramine in surface waters, but my results suggest that it can alter the organism’s behaviour in aquatic ecosystems.

The aim with this review was to investigate whether a reconnection of an oxbow lake can contribute to higher biodiversity. However, oxbow lakes can be divided in three categories: Lentic- (connected with both ends to the river bed), semi-lentic- (connected with one end) and lotic oxbow lakes (Isolated from the riverbed). Aquatic organisms such as fish, aquatic invertebrates, amphibians and macrophytes has been studied. The result showed that hydrological connectivity determines both biodiversity and water quality in oxbow lakes. Lotic oxbow lakes consisted low biodiversity and it’s dominated by amphibians. Semi-lentic oxbow lakes contributes with highest biodiversity of macrophytes, fish and aquatic invertebrates. Lentic oxbow lakes consisted less biodiversity and was dominated by fish. In conclusion, reconnection of an oxbow lake can be used as a restoration project to improve biodiversity.

Wetlands are globally important biogeochemical hotspots, and their roles as either significant sources of greenhouse gas or carbon sinks are strongly controlled by environmental drivers such as carbon, nitrogen, and phosphorus availability, which can stimulate emission of three greenhouse gases: nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4). Mounting evidence suggests that aquatic invertebrate activity can enhance wetland greenhouse gas flux, through bioturbation and bioirrigation of surrounding sediments. However, waterbirds reduce the density of aquatic invertebrates, which could potentially reduce greenhouse gas flux. Alternatively, the nutrient contents of waterbird guano may stimulate microbial activity responsible for these gas fluxes. The research project FLAMMINGGOS (Functional Links in Avian, Microbial, Macrophyte, and INvertebrate Greenhouse Gas Output Stimulation) aims to test the relative strength of top-down and bottom-up effects of predatory waterbirds on wetland greenhouse gas fluxes. This study is a part of the FLAMMINGGOS project and studied the bottom-up stimuli effects of methane flux, through addition of waterbird guano to sediment cores sampled from three sites in Doñana, Spain. Guano did not enhance methane flux; on the contrary, the overall flux rates decreased after guano addition for one site. There was also a positive correlation between methane flux and the presence of benthic invertebrates. This suggests that the top-down gas-stimuli effects of waterbirds may be stronger than the bottom-up; benthivorous waterbirds, such as flamingos, may lessen the emissions of CH4 through predation on benthic invertebrates. Further research is however required to fully understand these interactions and gas flux stimuli effects. / FLAMMINGGOS

Wood ash application (WAA) has been recommended mainly for two reasons; i) to avoid depletion of minerals in the soil due to whole tree harvest in the forestry and ii) to mitigate harmful effects of acidification of soil and surface waters. In conclusion, the effects on terrestrial ecosystems and, especially, tree growth, can be attributed to the properties of the ash, the dose applied and the specific site at which the ash is applied. The research conducted on the effects of WAA on limnological ecosystems is very limited, and the major purpose of the present thesis was to gain knowledge of the effects of wood ash to different freshwater organisms, and the more comprehensive, limnological effects of WAA in the first stream in Bispgården, Sweden. Effects of wood ash solutions on the unicellular alga Euglena gracilis Klebs, the amphipod Gammarus pulex L., and the moss Fontinalis antipyretica Hedw. were investigated under laboratory conditions. Common in all three species was the decline in performance (growth/velocity/respiration/oxygen evolution) when the concentration of wood ash exceeded 5 g/l and no adjustment of pH was done (alkaline solution). In contrast, different movement parameters (motility, upwards swimming and velocity) in E. gracilis (neutral conditions), and increased growth of F. antipyretica with increased concentrations of wood ash indicated that nutrients in the ash was bioavailable for these organisms. There was no evidence of toxic effects on the organisms from metals or other compounds as a result from exposure to wood ash solutions in the present studies. The field study was conducted in a forest area close to Bispgården, about 100 km NW from Sundsvall, Sweden. The catchment area (50 ha) of the stream Fanbergsbäcken was treated with wood ash in September of 2004 (3,000 kg/ha;selfhardened crush-ash). In general, both biological (diatoms) and chemical (pH, alkalinity, and aluminum (Al) measurements) indicators have shown no significant effect on acidification parameters from the addition of wood ash. There was, however, evidence of an increased pH during spring flood, accompanied with a decrease in the frequency of low pH values (<5.6) during spring flood. In addition to this, alkalinity was significantly higher in the period 2005-2006, compared to that of 2003. High concentrations of toxic forms of Al repeatedly occured in the stream Fanbergsbäcken, and the WAA did not affect the frequencies of high concentrations of toxic Al forms (<50 μg/l). Both the moss F. antipyretica and the leaves from Alnus incana displayed increased potassium (K) concentrations, although other nutrients did not increase from WAA. In conclusion, no evidence of WAA being effective in restoring or improving the ecological status of freshwater environments has been established, either in the literature or in the present field study. On the other hand, there were no indications of harmful effects due to WAA, either. However, we still do not know the effects of wood ash on several organisms (predominantly invertebrates) inhabiting small ponds and other, temporary or permanent, freshwater ecosystems. In the context of WAA, these environments and organisms have not attended any attention in the research published to date, and future studies are strongly encouraged.

Hydropower is an important source of renewable energy, but is often a cause of degradation to river ecosystems. Hydropeaking, i.e. the frequent alteration of discharge, is a process involved in hydropower generation and has been proven to affect aquatic organisms negatively. However, it’s unclear exactly what effects hydropeaking has on riverine ecology, in combination with important geomorphological characteristics. In this study, the interaction of hydropeaking and geological substrate (fine or coarse material) on aquatic macroinvertebrates was evaluated, while also assessing the influence of river width and water chemistry. Studies were conducted in 27 sites at rivers, 15 of which were exposed to hydropeaking, in central Sweden during June and August 2020. Sampling of macroinvertebrates was conducted using Hester-Dendy samplers. The following variables were investigated: i) total species richness, ii) species diversity, iii) macroinvertebrate density, iv) EPT (Ephemeroptera, Plecoptera, and Trichoptera) species richness, v) % EPT, vi) EPT/Chironomidae ratio, and vii) % Oligochaeta. The effects of hydropeaking and geological substrate on these variables were assessed using AIC model selection. Results did not indicate interaction effects of hydropeaking and geological substrate on any variable, and this did not concur with stated hypotheses. The results reaffirm the complexity of disentangling the effects that are in play during these processes. Studies of this kind is important in understanding how hydropower affects macroinvertebrates, and provides information on where and how most effective mitigation measures should be applied and provides valuable information for improving hydropower management protocols. / Vattenkraft är en viktig källa till förnybar energi, men är ofta en orsak till försämring av ekosystem hos älvar. Korttidsreglering, dvs. den frekventa förändringen av vattenflöde, är en process som är involverad i vattenkraftsproduktion och har visat sig påverka vattenlevande organismer negativt. Det är dock oklart exakt vilka effekter korttidsreglering har på älvens ekologi, i kombination med viktiga geomorfologiska egenskaper. I denna studie utvärderades interaktionen mellan korttidsreglering och geologiskt substrat (fint eller grovt material) på akvatiska makroevertebrater, samtidigt som påverkan av älvbredd och vattenkemi utvärderades. Studier utfördes på 27 platser lokaliserade vid älvar, av vilka 15 var utsatta för korttidsreglering, i centrala Sverige under juni och augusti 2020. Provtagning av makroevertebrater utfördes med Hester-Dendy-provtagare. Följande responsvariabler undersöktes: i) total artrikedom, ii) artdiversitet, iii) densitet av makroevertebrater, iv) artrikedom av EPT (Ephemeroptera, Plecoptera och Trichoptera), v) % EPT, vi) EPT/Chironomidae-förhållande samt vii) % Oligochaeta. Effekterna av korttidsreglering och geologiskt substrat på dessa variabler bedömdes med hjälp av AIC-modellval. Resultaten indikerade inte interaktionseffekter av korttidsreglering och geologiskt substrat på någon responsvariabel, och detta överensstämde inte med angivna hypoteser. Resultaten bekräftar komplexiteten i att utvärdera de effekter som har en påverkan under dessa processer. Studier av detta slag är viktiga för att förstå hur vattenkraft påverkar makroevertebrater, och ger information om var och hur de mest effektiva åtgärderna bör tillämpas och ger värdefull information för att förbättra hantering av vattenkraft. / Korttidsregleringens påverkan på biologin varierar med vattendragets geomorfologi

Hydropeaking is important to meet peak demand of electricity on the Swedish powergrid. The rapid changes in discharge may affect the ecology of streams and rivers negatively downstream of hydropeaking powerplants. In this study, the composition of five functional feeding groups (FFG) was investigated in the families Ephemeroptera, Plecoptera and Trichoptera (EPT) in samples collections by Hester-Dendy-sampler in 27 locations in streams and rivers with and without hydropeaking. The groups shredders, grazers, gatherers, filter feeders and predators were identified for each toxon. I expected that the flow regime downstream of a hydropeaking powerplant would affect the composition of FFG compared to non-hydropeaking streams and rivers, except for the group predators. No significant differenses in FFG between the streams and rivers with and without hydropeaking was found. These results indicate that effects from hydropeaking on FFG is not general and that spatially-explicit investigations may be needed to shed light on the effects of hydropeaking. / För att reglera effektbehovet på det svenska elnätet är korttidsregleringen från vattenkraftverk en viktig faktor. Dessa snabba förändringar i flödesregimen medför dock en påverkan på ekologin i vattendraget. I den här studien undersöktes sammansättningen av fem olika funktionella födosöksgrupper (FFG) hos Ephemeroptera, Plecoptera och Trichoptera (EPT) från insamling av evertebrater med Hester-Dendy-provtagare i 27 lokaler i vattendrag med och utan korttidsreglering. Identifiering av grupperna shredders, grazers, gatherers, filter feeders och predators gjordes för varje taxon. Jag förväntade mig att flödesregimen som förekommer nedströms korttidsreglerade vattenkraftverk skulle påverka sammansättningen av FFG i jämförelse med ett icke korttidsreglerat vattendrag, förutom för gruppen predators. Data visade att det inte fanns någon signifikant skillnad hos FFG mellan vattendragen med vs. utan korttidsreglering. Detta visar att påverkan på FFG av korttidsreglering inte är generell och att platsspecifika undersökningar kan behövas för att belysa regleringens effekter.

Climate change affects lakes, seas and running water globally, but the long-term effects on aquatic ecosystems, including fish communities, are complex and difficult to predict. Previous research has shown that changes in temperature, for example, can lead to shifts in fish species distribution and reductions in body size within fish communities. This study aims to investigate the impact of temperature on size distribution of individuals in fish communities by examining variations in so-called size spectrum and mean body size in ten Swedish lakes over the period 1994-2023. Data were collected from Swedish monitoring programs and analyzed using linear mixed-effects models. The result indicates a significant negative effect of temperature on the size spectrum and mean body size, meaning the number of small individuals increases while the number of large ones decreases. The size spectrum also shows a declining trend over time in several of the lakes, highlighting a shift in the size distribution of fish. These findings support the use of the size spectrum as an indicator of the impacts of climate change on freshwater ecosystems. The results of this study found a clearer link between temperature changes and size distribution compared to biomass, which supports the usefulness of size distribution as an indicator. Understanding these relationships is crucial for informing management and conservation strategies aimed at preserving lake ecosystems and the functions and ecosystem services that fish provide, including food and recreational opportunities. The study further contributes to the existing evidence that climate change is reshaping fish communities and aquatic ecosystems, underscoring the need for adaptive management to mitigate these effects and ensure sustainability of fish stocks for future generations. / Klimatförändringarna påverkar sjöar, hav och rinnande vatten globalt, men långsiktiga effekter på akvatiska ekosystem, inklusive fisksamhällens, är komplexa och svåra att förutse. Tidigare studier har visat att förändringar i temperatur till exempel kan leda till skiften i fiskarters utbredning och minskningar i kroppsstorlek i fisksamhällen. Denna studie syftar till att undersöka temperaturens inverkan på storleksfördelningen av individer i fisksamhällen genom att undersöka variation i det så kallade storleksspektrumets lutning och medelstorlek i tio svenska sjöar under perioden 1994–2023. Data samlades in från svenska övervakningsprogram för sjöar och analyserades med hjälp av linjära mixade effektmodeller. Resultaten indikerar en signifikant negativ effekt av temperatur på storleksspektrumets lutning och medelkroppsstorlek, dvs. antalet små individer ökar relativt antalet stora. Storlekspektrumets lutning visar också en nedåtgående trend över tid i flera av sjöarna, vilket belyser att fiskarnas storleksfördelning har skiftat mot relativt fler små individer i vissa sjöar. Dessa fynd styrker användningen av storleksspektrum som en indikator på klimatförändringarnas effekter på sötvattensekosystem. Resultat från denna studie visar också en tydligare koppling av förändrad temperatur på storleksfördelning än biomassor av fisk och växtplankton, vilket styrker nyttan av storleksfördelning som indikator. Att förstå dessa samband är avgörande för att vägleda förvaltnings- och bevarande strategier som syftar till att bevara sjöekosystem, de funktioner samt ekosystemtjänster som fiskar tillhandahåller, såsom mat och rekreationsmöjligheter. Studien bidrar till redan existerande bevis på att klimatförändringarna omformar fisksamhällen och akvatiska ekosystem, vilket tydliggör behovet av adaptiv förvaltning för att mildra dessa effekter och säkerställa starka fiskbestånd för framtida generationer.

A regional survey of environmentally harmful substances in fish in autumn 2013 revealed elevated levels of polychlorinated biphenyls (PCBs) in perch from Lake Oxundasjön, north of Upplands Väsby in Stockholm County. Follow-up studies have shown that the quantity of PCBs contained in the lake is unique of its kind in Sweden, and that the area of influence also includes downstream Rosersbergsviken, a bay of Lake Mälaren. The elevated concentrations in fish exceed today's market limits and environmental quality standards for PCBs, as of this, responsible authorities discourage from consumption of fish from Lake Oxundasjön and Rosersbergsviken. The aim has been to use statistical analyses and mass-balance modelling to study the current state of the lake system and how it may evolve in the future under different circumstances. There is a statistically significant correlation between PCB levels in sediment and perch from 21 different sites in the Stockholm-Mälaren region, including Lake Oxundasjön and Rosersbergsviken, this was demonstrated with a linear regression model. With the multivariate analysis method principal component analysis (PCA), it was illustrated how the contaminant levels in fish from Lake Oxundasjön and Rosersbergsviken differed on contaminant levels in fish from other sites. The difference mainly concerned the size and composition of PCBs. Mass-balance modelling of quantities and flows of PCBs in Lake Oxundasjön and Rosersbergsviken was made in the simulation program STELLA®. The modelling indicated that the system currently serves as a secondary distribution source of PCBs to the environment. The recovery of PCB levels is slow in the system, it will take more than 25 years for concentrations in fish to reach today’s market limits and environmental quality standards for PCBs. The model was used to evaluate three different treatment methods for Lake Oxundasjön: dredging, capping and activated carbon treatment. Simulations of these treatments led to a substantial improvement of the PCB situation in Lake Oxundasjön. Moreover, they also had a positive impact on the recovery process in the downstream Rosersbergsviken. Future climate changes, with warmer temperatures and higher run off, led to a slightly faster recovery progress of PCBs in the system.