Kiselalger i vattendrag i Dalarnas län

Generellt indikerar kiselalgsamhällen i de flesta av de undersökta vattendragen i Dalarnas län god till hög. Bara tre vattendrag hamnar i klass måttligt (Mässingsboån, Broån, Anstaån), vilket kan förklaras av en måttlig påverkan av övergödning och en möjlig påverkan av en ringa organisk förorening, troligtvis pga. lantbruk åtminstone för Broån och Anstaån. Alla bakgrundsvariablerna tillsammans förklarade 43 % av provpunkternas kiselalgssammansättning och variation i de undersökta vattendragen. pH och TOC var de viktigaste parametrar som förklarar artsammansättningen och variation, följd av ARO areans storlek, Tot-N och Tot-P. Andra parametrar som substrat, vattendragsbredd, kalkningen och metallhalter förklarar i mindre omfattning skillnader mellan olika samhällen. 302 taxa hittades i Dalarnas vattendrag, varav många ovanliga taxa. De tio vanligaste taxa var Achnanthes minutissima grupp II (medelbredd 2,2-2,8μm), Achnanthes minutissima grupp III (medelbredd >2,8μm) (AMI3), Fragilaria gracilis Østrup, Tabellaria flocculosa (Roth) Kützing, Brachysira neoexilis Lange-Bertalot, Eunotia incisa var. incisa Gregory, Navicula minima Grunow, Gomphonema exilissimum Lange-Bertalot & Reichardt, Achnanthes subatomoides (Hustedt) Lange-Bertalot & Archibald och Frustulia crassinervia (Brébisson) Lange-Bertalot & Kramme

Benthic diatoms in lakes

In order to protect or improve surface waters ecosystem response to pressures needs to be quantified. Diatoms are frequently used for assessing ecological status in streams and for reconstructing water quality of lakes. However, ecological status assessment of European lakes based on extant diatom assemblages is rare. The overall aim of this thesis is to facilitate the application of benthic diatoms in water quality assessment of boreal lakes, using methods developed for stream assessment. Therefore, I investigated (i) the main environmental drivers of lentic diatom assemblages, (ii) the structural differences between lentic and lotic diatom assemblages (iii) the implications of differences between lake and stream diatom assemblages for assessment, (iv) the power of different aquatic organisms as indicators of nutrient and acidity status in lakes, and (v) ecological thresholds of diatom and phytoplankton assemblage structure along a nutrient gradient in boreal lakes. The major environmental drivers of benthic diatom assemblage composition in boreal lakes were gradients in acidity and nutrient status. In contrast, the distribution of ecological diatom guilds seems to be decoupled from nutrient availability in acidic compared to high pH aquatic systems. Diatom assemblage composition can thus be recommended for ecological status assessment of boreal lakes, whereas species-specific growth morphology and the drivers affecting growth morphology need further study. Most diatom taxa occurred in Swedish lakes and streams, but differences in frequency and abundance among lakes and streams were noted. However, the diatom indices IPS and ACID, developed for streams, responded similarly to nutrient and acidity gradients, respectively, in Swedish lakes and streams and can thus also be recommended for ecological status assessment of lakes. In nutrient poor boreal lakes, both primary producers and primary consumers were correlated with nutrient concentrations. Primary producers, especially diatoms, displayed a stronger response to pH than macro-invertebrates, possibly due to shorter generation times implying faster response. Nutrient thresholds in taxonomic and guild structure of benthic diatom assemblages in boreal lakes were found at low TP concentrations (18-26 μg L⁻¹). However, caution is advised in interpreting the response of some species to nutrients, as pH dependencies might obscure the response of some nutrient sensitive diatom species to TP

Pesticide Mixtures Cause Short-Term, Reversible Effects on the Function of Autotrophic Periphyton Assemblages

In a laboratory experiment we investigated the effects of pesticide mixtures on the structure and function of freshwater biofilms, with focus on their photoautotrophic component. We identified 6 herbicides and 1 fungicide commonly found in Swedish streams at relatively high concentrations and created 3 ternary mixtures that were tested in concentration series ranging from observed environmental concentrations to up to 100 times higher. Biofilms were exposed to these pesticide mixtures for 8 d and then allowed to recover for another 12 d. Our results show a rapid and consistent inhibition of photosynthesis after just 24-h exposure to the highest test concentration of pesticides, as well as in some treatments with lower concentrations (i.e., 10 times the environmental level), on exposure. Interestingly, the observed effects were reversible because biofilm photosynthesis recovered rapidly and completely in clean media in all but one treatment. In contrast to the functional response, no effects were observed on the algal assemblage structure, as assessed by diagnostic pigments. We conclude that the pesticide mixtures induce a rapid but reversible inhibition of photosynthesis, without short-term effects on biofilm structure. Environ Toxicol Chem 2020;00:1-8. (c) 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC

EU reference conditions in Swedish lakes identified with diatoms as palaeoindicators - a review

This study aims to assess the reference conditions and reference diatom communities for Swedish lakes by summarizing 36 performed palaeolimnological studies. The following results can serve as a tool in the discussion about reference conditions according to the European Water Framework Directive. (1) Finding one general fixed time of prevailing reference conditions for all Swedish lakes is impossible. (2) 1850 AD, as an often applied fixed reference time, is not an appropriate reference time for all Swedish lakes. (3) Reference nutrient and pH conditions for many southern Swedish lakes were prevailing until about 2300 BP. (4) Reference nutrient and pH conditions for many northern Swedish lakes prevailed longer and may even prevail today. (5) Different reference diatom communities can be found: either benthic (both acidophilous and alkaliphilous) or planktonic communities

Benthic diatoms in lakes : environmental drivers and ecological assessment [Elektronisk resurs]

In order to protect or improve surface waters ecosystem response to pressures needs to be quantified. Diatoms are frequently used for assessing ecological status in streams and for reconstructing water quality of lakes. However, ecological status assessment of European lakes based on extant diatom assemblages is rare. The overall aim of this thesis is to facilitate the application of benthic diatoms in water quality assessment of boreal lakes, using methods developed for stream assessment. Therefore, I investigated (i) the main environmental drivers of lentic diatom assemblages, (ii) the structural differences between lentic and lotic diatom assemblages (iii) the implications of differences between lake and stream diatom assemblages for assessment, (iv) the power of different aquatic organisms as indicators of nutrient and acidity status in lakes, and (v) ecological thresholds of diatom and phytoplankton assemblage structure along a nutrient gradient in boreal lakes. The major environmental drivers of benthic diatom assemblage composition in boreal lakes were gradients in acidity and nutrient status. In contrast, the distribution of ecological diatom guilds seems to be decoupled from nutrient availability in acidic compared to high pH aquatic systems. Diatom assemblage composition can thus be recommended for ecological status assessment of boreal lakes, whereas species-specific growth morphology and the drivers affecting growth morphology need further study. Most diatom taxa occurred in Swedish lakes and streams, but differences in frequency and abundance among lakes and streams were noted. However, the diatom indices IPS and ACID, developed for streams, responded similarly to nutrient and acidity gradients, respectively, in Swedish lakes and streams and can thus also be recommended for ecological status assessment of lakes. In nutrient poor boreal lakes, both primary producers and primary consumers were correlated with nutrient concentrations. Primary producers, especially diatoms, displayed a stronger response to pH than macro-invertebrates, possibly due to shorter generation times implying faster response. Nutrient thresholds in taxonomic and guild structure of benthic diatom assemblages in boreal lakes were found at low TP concentrations (18-26 μg L⁻¹). However, caution is advised in interpreting the response of some species to nutrients, as pH dependencies might obscure the response of some nutrient sensitive diatom species to TP

Differences in benthic diatom assemblages between streams and lakes in Sweden and implications for ecological assessment

Benthic diatom assemblages from 179 streams and 98 lakes in Sweden were compared to identify differences in taxonomic composition, growth form, cell size, diversity and richness, and ultimately, to assess the effects of differences between streams and lakes on assessments. Streams and lakes with similar environmental background variables were chosen to avoid an overriding effect of factors, such as nutrients and pH, on taxonomic composition. Generic and species composition differed significantly between streams and lakes. Richness was significantly higher in lakes than in streams, and the average diatom cell was significantly longer in streams than in lakes. No other measures analyzed differed significantly. Diatom assemblages in both habitats were related to pH and nutrients, and the diatom indices studied responded similarly to the main environmental gradients in both habitats. Thus, despite differences in taxonomic composition between streams and lakes, the resulting diatom assemblages are similar, enabling use of the same diatom indices in both habitats

Kiselalger som indikatorer i sjöar

Slutsatser: Våra första resultat tyder på att de existerade kiselalgsindexen IPS och ACID även kan användas i sjöar för att bedöma vattenkvaliteten. Variationen mellan olika lokaler från samma sjö ligger inom gränserna för felmarginaler, vilket betyder att en lokal antas räcka för att bedöma en sjö. Tidsvariationen är större, men orsakerna är inte undersökta än. Mera forskning behövs framförallt på näringsrika sjöar, på sjöar med pH-värde under 6, på sjöar norr om Limes Norrlandicus och på sjöar med en god planktonprovtagning för att verifiera resultate