Continuous modelling and discrete classification (aka typology) are two approaches commonly used to partition natural, spatial variability, and ultimately gauge anthropogenic effects on biodiversity loss and other valued ecosystem services. Using benthic invertebrate assemblages of boreal lakes and streams, we tested the efficacy of continuous modelling and discrete classification for partitioning natural variability of sites judged to be in reference condition. We anticipated that species distributions and assemblage composition would be more accurately predicted by models in general and specifically that models based on suites of predictor variables would outperform models based on a limited number of variables. Furthermore, we predicted that more flexible typologies would perform better than approaches using sets of mandatory categorical variables. Our results showed that models were more accurate at estimating species distributions and assemblage composition than typologies. Furthermore, models calibrated with only a few typology based variables were as accurate as full models, indicating that the main environmental gradients were captured by the classification variables used in our study. Continuous modelling also had lower incidences of false positives (< 7%) compared to typological approaches (3.8-56%), i.e. a lower frequency of classifying reference sites as possibly impaired. The findings that continuous modelling outperformed discrete classification and that the latter had substantially higher frequencies of false positives is somewhat disconcerting given the relatively widespread use of typologies in bioassessment and management. Misclassification results in the unnecessary use of resources to re-classify sites, or more seriously implementation of unwarranted measures of rehabilitation.

Inom overvakningsprogrammet Fjallvegetation inventeras vegetationen pa tolv svenska fjall. Inventeringarna utfors i provytor utlagda langs transekter som utgar fran toppen av fjallen och ar riktade at olika hall. Varje fjall inventeras var femte ar. Areskutan, som var det forsta fjallet att inventeras, har inventerats tre ganger. I den har rapporten presenteras resultaten fran analyser av de tre inventeringarna pa Areskutan. Det overgripande malet har varit att foresla metoder och tillvagagangssatt for att analysera och presentera data fran overvakningsprogrammet, samt tillhandahalla en vagledning som kan anvandas for analyser av data i framtiden. Analyserna av data visade att vegetationen som forvantat paverkas av bland annat hojd over havet och lutning, samt att vegetationen skiljer sig mellan de olika transekterna. Vi fann signifikanta forandringar i artsammasattning mellan inventeringarna, men forandringarna var sma jamfort med variationen mellan ytor, och det fanns ingen enhetlig riktning i forandringarna. Analys av omsattning av arter over tid visade pa skillnader mellan olika ytor, men den skillnaden kunde inte forklaras med ytornas hojd, lutning, riktning eller markfuktighet, och skiljde sig heller inte mellan transekterna. Sammantaget indikerarar dessa resultat att det annu inte finns nagra storskaliga riktade forandringar i vegetationen pa Areskutan. Analyser av enskilda arter visade att vissa arter var vanligare vissa ar, exempelvis var angsfryle vanligare 2006 an ovriga ar, och mattlummer vanligast vid inventeringen 2017. Manga arters forekomstfrekvens forandrades mellan inventeringarna, och manga av arterna med storsta forandringar var lavar. Den stora okningen av manga lavars forekomstfrekvens ar intressant, och bor undersokas ytterligare. Exempel pa arter vars forekomstfrekvens minskade mellan 2006 och 2017 ar odon, fjallglim och fjallskara. Medianhojd over havet for enskilda arters forekomster minskade for 60 arter, var oforandrad for 15, och okade for 56 mellan 2006 och 2017. Den storsta okningen observerades for revlummer, vars medianhojd okade med 223 meter. Den hogsta observationen pa fjallet var hogre 2017 an 2006 for 50 av 131 arter, oforandrad for 52 arter och lagre for 29 arter. Svartfibblors maxhojd minskade mest, med 328 meter, medan revlummers maxhojd okade mest, med 308 meter. Antalet trad per provyta och medelhojd pa traden forandrades inte signifikant under perioden 2006–2017. Daremot minskade bade tradskiktets tackningsgrad och faltskiktets tackningsgrad. Aven flera enskilda vegetationstypers tackningsgrad minskade mellan inventeringarna. Om de olika observerade forandringarna beror pa naturlig klimatvariation, skillnader i betestryck, klimatforandringar, andra manskliga aktiviteter, eller om den beror pa variation i inventeringarna, gar inte att klargora. Nar analyserna upprepas for fler fjall, och nar mer data finns tillgangliga, kommer det bli lattare att dra slutsatser om orsaker till observerade forandringar.

Land use often results in multiple pressures affecting the structure and function of aquatic ecosystems. Understanding how pressures interact to affect the biology of aquatic ecosystems is therefore a major challenge for freshwater management. Using a field survey approach, we studied individual and combined effects of impacts arising from agricultural land use and alteration of hydrology and geomorphology (HYMO) on benthic invertebrate assemblages in boreal streams. Variation partitioning of species and trait composition to pressures characterizing agriculture and HYMO revealed significant joint effects on the biota. Changes in species composition were significantly and uniquely related to agricultural pressures, whilst the variance component characterizing HYMO effects was not significant, confounding separation of unique pressure effects. In line with our predictions, the effects of HYMO on species and trait composition were largely negative. However, in contrast to predictions, ranking pressure variables showed that agricultural impacts explained more of the variability in species composition than HYMO impacts. Disturbance of riparian habitats was a strong predictor of shifts in species and trait composition. Interestingly, community responses were less pronounced at sites affected by both loss of riparian integrity and elevated nutrients, suggesting that HYMO effects were mitigated by moderate levels of elevated nutrients. Collectively, our results showed ecologically realistic, impact-specific changes on biodiversity of riverine environments. This knowledge allows managers to rank the importance of individual and combined pressure impacts when designing rehabilitation strategies.

Lakes are affected by a number of anthropogenic pressures, often resulting in biodiversity loss and impairment of ecosystem services. Here we analysed responses of littoral invertebrate assemblages in 589 temperate lakes to five anthropogenic pressures and combined pressure load. Over half of the lakes (n = 302) were deemed to be affected by one or more pressures. The most pervasive pressures were forestry (73% of the impacted lakes), agriculture (21%) and acidification (11%). Individually, agriculture and pH explained > 20% of the among-lake variability in littoral invertebrate assemblages. Ranking the importance of the five pressures on littoral invertebrate assemblages, after accounting for covariance with natural factors and other pressures, showed that acidity > agriculture > forestry > urbanization >= invasive species. Although about 10% of the lakes were acidified according to chemical criteria, our finding that acidity was ranked first is partly due to the naturally low pH of humic boreal lakes, and not acidification per se. Comparison of species composition to cumulative pressure load revealed no clear patterns. Species composition (CA axis 1 scores) in lakes with one or more pressures differed from sites with no pressures, but cumulative pressure effects were non-significant. A significant three-pressure impact was found for species composition characterized by CA axis 2 scores, related to the combined pressures of agriculture, invasive species and urbanization. Collectively, our results show that littoral invertebrate assemblages respond uniquely to several different pressures, underpinning their use as a biomonitoring tool for assessing the ecological status of lakes. Ranking the effects of individual pressures as done here is a critical step in designing and implementing measures to protect and mitigate anthropogenic effects on biodiversity loss.

Here, we use a novel space-by-time approach to study large-scale changes in phytoplankton species distribution in Swedish boreal lakes in response to climate variability. Using phytoplankton samples from 27 lakes, evenly distributed across Sweden, all relatively unimpacted by anthropogenic disturbance and sampled annually between 1996 and 2010, we found significant shifts in the geographical distribution of 18 species. We also found significant changes in the prevalence of 45 species (33 became more common and 12 less common) over the study period. Using species distribution models and phytoplankton samples from 60 lakes sampled at least twice between 1992 and 2010, we evaluated the importance of climate variability and other environmental variables on species distribution. We found that temperature (e.g., extreme events and the duration of the growing season) was the most important predictor for species detections. Many cyanobacteria, chlorophytes, and, to a lesser extent, diatoms and zygnematophytes, showed congruent and positive responses to temperature. In contrast, precipitation explained little variation and was important only for a few taxa (e.g., Staurodesmus spp., Trachelomonas volvocina). At the community level, our results suggest a change in community composition at temperatures over 20 °C and growing seasons longer than 40 days. We conclude that climate is an important driver of the distributional patterns of individual phytoplankton species and may drive changes in community composition in minimally disturbed boreal lakes.

•We examine changes in distribution, occurrence and bloom incidence of the noxious Gonyostomum semen.•G. semen was spreading in southern Sweden but not north of Limes Norrlandicus.•The occurrence of G. semen was mainly explained by climate variables (e.g. temperature).•pH and water color were the best predictors of bloom incidence.•Morphometry and catchment variables were only important at high dominance levels of G. semen (>90% total phytoplankton biomass).

Species distribution modeling is used in applied ecology; for example in predicting the consequences of global change. However, questions still remain about the robustness of model predictions. Here we estimate effects of landscape spatial configuration and organism flight ability—factors related to dispersal—on the accuracy of species distribution models. Distribution models were developed for 129 phytoplankton taxa, 164 littoral invertebrate taxa and 44 profundal invertebrate taxa sampled in 105 Swedish lakes, using six different modeling techniques (generalized linear models (GLM), multivariate adaptive regression splines (MARS), classification tree analysis (CTA), mixture discriminant analysis (MDA), generalized boosting models (GBM) and random forests (RF)). Model accuracy was not affected by dispersal ability (i.e., invertebrate flight ability), but the accuracy of phytoplankton assemblage predictions and, to a lesser extent, littoral invertebrate assemblages were related to ecosystem size and connectivity. Although no general pattern across species or spatial configuration was evident from our study, we recommend that dispersal and spatial configuration of ecosystems should be considered when developing species distribution models.

Species distribution models are used for a wide range of ecological applications, such as assessment of ecological status. For many such assessments, predictions of entire communities are preferred. When entire community compositions are modelled, two options are available: (1) to model all of the communities' species individually and (2) to incorporate community information into the models. Here, we compared the accuracy of these two modelling approaches for predicting boreal lake phytoplankton assemblages and their ability to detect human impact. The modelling approaches tested were specifically classification-then-modelling (here a RIVPACS-type model, using random forest to predict biological group membership) and species-by-species modelling, using a random forest model for each species.The species-by-species models performed better than the RIVPACS model according to the dissimilarity measure BC, the area under curve (AUC) and proportion of true positives. In contrast, the taxonomic completeness index (O/E), commonly used for freshwater assessments, indicated that the RIVPACS model performed better. However, we believe that O/E overestimates model performance, due to the index omitting false negative errors (i.e. errors where species are wrongly predicting as absent).No support was found for our hypothesis that rare species would be better modelled by the RIVPACS model. Indeed, the RIVPACS model predicted common species significantly better than the species-by-species models, whilst the species-by-species models predicted rare species better than the RIVPACS model.Both modelling methods were able to separate impaired sites (acidified and eutrophic) from reference sites.We suggest that classification-then-modelling is evaluated using data-set containing more possible biological interactions, e.g. phytoplankton, zooplankton and fish. We also suggest that AUC is used as a complement to taxonomic completeness when evaluating models for reference condition taxa composition. (C) 2012 Elsevier B.V. All rights reserved.

Species distribution models are a group of methods often used to estimate consequences of global change, to assess ecological status and for other ecological applications. The main idea behind species distribution models is that the geographical distributions of species can, to a large part, be explained by environmental factors and that species distributions therefore can be predicted in time or space. For robust and reliable applications, models need to be based on sound ecological principles, predictions need to be as accurate as possible, and model uncertainties need to be understood. Two approaches are available for modelling entire species communities: (1) each species can be modelled individually and independently of other species or (2) community information can be incorporated into the models. The first study in this thesis compares these two modelling approaches for predicting phytoplankton assemblages in lakes. The results showed that predictive accuracy was higher when species were modelled individually. The results also showed that phytoplankton can be used for model-based assessment of ecological status. This finding is important because phytoplankton is required for assessing the ecological status of European water bodies according to the European Water Framework Directive. Dispersal barriers in the landscape or limited dispersal ability of species might be a reason for species being absent from suitable habitats, and these factors might therefore affect model accuracy. The second study in this thesis examines the influence of dispersal and the spatial configuration of ecosystems on prediction accuracy of benthic invertebrate and phytoplankton distribution and assemblage composition. The results showed only a minor influence of spatial configuration and no effect of flight ability of invertebrates on model accuracy. However, the models used may partly account for dispersal constraints, since dispersal-related factors, such as lake surface area, are included as predictor variables. The result also showed that composition of littoral invertebrate assemblages was easier to predict at sites located in well-connected lake systems, possibly because the relatively unstable littoral zone necessitates a need for species to re-colonize disturbed habitats from source populations.

In this study, we report the results from a recently performed survey of zebra mussel in Sweden and present a risk model for the potential distribution of the species. The zebra mussel was found in 11 of the 30 surveyed lakes and rivers. Most of the observations were made in the north-eastern parts of Lake Mälaren, i.e., in the basins Ekoln, Skarven, and Görväln. Hierarchical partitioning and stepwise selection of water chemistry variables in a multiple logistic model identified pH and magnesium concentrations as the best predictors for zebra mussel occurrence. We conjecture that magnesium is an important predictor due to its crucial role in mussel physiology. The logistic model was applied on 2,781 lakes and in total 109 lakes (3.9%), most of them situated in specific areas in central Sweden, in the very south and on the island of Gotland, were predicted to be potentially at risk for zebra mussel invasions. The lakes potentially at risk for zebra mussel invasions are separated by the soft-water boreal lakes that constitute the vast majority of lakes on the Fennoscandian peninsula, thus forming barriers for further dispersal.

Detta ar en forsta delrapport fran undersokningen av lampliga indikatorarter for stabila vattenmiljoer och artrikedom.Den rodlistade makroskopiska cyanobakterien sjohjortron (Nostoc zetterstedtii) ...

Vandrarmusslan utbredning i Sverige ar idag begransad till kalkrika omraden. Utbredningen verkar begransas av vattenkemin. De vattenkemiska variabler som styr ar framst pH och kalciumkoncentration. For att predicera vandrarmusslans potentiella utbredning anvande vi data pa nuvarande utbredning och vattenkemi for att skapa en riskmodell. Nar modellen applicerades pa data fran riksinventeringen av sjoar och vattendrag visade det sig att vandringmusslan skulle kunna oka sin utbredning i mattlig utstrackning. Ett tjugotal vatten i jordbruksomraden kring Vanern och Vattern, ett storre antal vatten i Uppland, samt sjoar i Skane och pa Gotland har en vattenkemi som enligt modellen tillater att vandrarmusslan etablerar sig. For en etablering karvs dock aven att arten sprids till de aktuella vattnen. For att overvaka artens spridning ar det viktigt att regelbundna inventeringar gors framfor allt i de omraden som bedoms som mojliga for vandrarmusslan att kolonisera.

Denna rapport utgor rapportering av ett projekt med syfte att utfora olika analyserav vegetationsdata pa Areskutan, fran det regionala miljoovervakningsprogrammetFjallvegetation, och beskriva metod ...