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Increasing concentration of iron (Fe) is observed in many boreal lakes, such as for the present study in Oslo Østmark, SE-Norway (1983–2018). As Fe-regulating processes are complex and dynamic, the link between mobilizing and retention processes is still not well understood. A seasonal study (2017–2018) from two headwaters, with medium and high dissolved organic matter (DOM) concentrations, showed that the loading of Fe to the lakes was highly dependent on flow conditions. Significantly higher values of Fe were related to autumn and winter periods with high runoff of highly colored and aromatic DOM compared to a severe drought period with minimum Fe values in the lakes. Compared to DOM, a significantly larger part of Fe was in a colloidal form, and a size-selective process (dependent on flow and water retention time) seemed to preferentially settle Fe compared to DOM. In contrast to Fe, the variability in DOM concentrations was moderate through the whole year. However, there were significant changes in the spectroscopic properties of DOM, with decreased fluorescence intensity and increased spectral slope during the warm dry season, indicating increased importance of DOM turnover in the lake. As Fe was transported from the catchment during high flow condition, at the same time as the oxic form of sulfur (SO42−), there was no sign of retention of Fe as FeS. We conclude that the mobilization and retention of compounds that are mainly in a colloidal form, such as Fe, are especially vulnerable to changes in flow conditions, suggesting increased variation in Fe levels in a future climate with increased frequency of flooding and drought episodes.

Elevated concentrations of sulfate in waterways are observed due to various anthropogenic activities. Elevated levels of sulfate can have harmful effects on aquatic life in freshwaters: sulfate can cause osmotic stress or specific ion toxicity in aquatic organisms, especially in soft waters where Ca2+ and Mg2+ concentrations are low. Formerly, chronic toxicity test data in soft water have been scarce. The chronic and acute sulfate toxicity tests conducted with aquatic organisms from 10 families across various trophic levels in this study multiplied the number of tests conducted in soft freshwater conditions and enabled derivation of the species sensitivity distribution (SSD) and sulfate hazardous concentrations for soft freshwaters. The cladoceran Daphnia longispina and freshwater snail Lymnaea stagnalis were the most sensitive to sulfate among the studied species. Harmful effects on the reproduction of D. longispina were observed at 49 mg SO4 /L while growth of L. stagnalis was inhibited at 217 mg SO4 /L. Most studied organisms tolerated high sulfate concentrations: the median of chronic effective concentrations (EC10 or LC10) was 1008 mg/L for all the species tested in this study. Based on the species sensitivity distribution of the studied species the hazardous concentration for 5 % of aquatic organism (HC5) in soft waters was 117–194 mg SO4/L. Different data set combinations were used to demonstrate the data variability in SSD-based HC5 estimates. The lowest values were produced from combining biotest results from the present study and earlier literature, while the highest values were calculated from the present study only. The derived chronic no-effect concentrations (PNEC) varied between 39 and 65 mg SO4/L. peerReviewed

The depth of the mixed layer is a major determinant of nutrient and light availability for phytoplankton in stratified waterbodies. Ongoing climate change influences surface waters through meteorological forcing, which modifies the physical structure of fresh waters including the mixed layer, but effects on phytoplankton biomass are poorly known. To determine the responses of phytoplankton biomass to the depth of the mixed layer, light availability and associated meteorological forcing, we followed daily changes in weather and water column properties in a boreal lake over the first half of a summer stratification period. Phytoplankton biomass increased with the deepening of the mixed layer associated with high wind speeds and low air temperature relative to the temperature of the mixed layer (Tair−Tmix

Large freshwater mussels (Unionida) are long-lived, have large bodies, and produce thousands to millions of larvae (glochidia) that usually must attach to host fish tissue to complete their life cycle. This is an obligate parasitic stage of mussel larvae. However, less than one in onemillion find a suitable host and survive. The degree of host specificity varies among unionid species, from specialists that can successfully parasitize only one or a few closely related fish species to generalists that can complete development on a taxonomically broad range of fish species. In addition, freshwater mussels are among the most threatened groups of animals. This is due to habitat destruction, the introduction of non-native species, and the loss of host fish on which their larvae (glochidia) are obligate parasites. Glochidiosis harms fish by affecting their growth; on the other hand, freshwater mussels play an important role in freshwaters by improving water quality and ridding the water of bacteria, algae, and pollutants, they are an indicator species of water quality. During our parasitological survey of fish from the Macedonian part of Lake Prespa in April 2022, many glochidia were found on the gills, skin, and fins of two endemic fishes, Prespa roach (Rutilus prespensis) and Prespa nase (Chondrostoma prespense), in the range of tens to thousands on one host. We thus recorded these two endemic species as new hosts of A. cygnea.

In this study we measured the total concentration of BTCs using grab water sampling, dissolved concentration with passive samplers, and particle-bound fraction with sedimentation traps in a Finnish inland lake. The sampling was conducted from May to September over two study years. In grab water samples the average concentration of MBT at sampling sites varied between 4.8 and 13 ng L−1, DBT 0.9–2.4 ng L−1, and TBT 0.4–0.8 ng L−1 during the first study year and 0.6–1.1 ng L−1, DBT 0.5–2.2 ng L−1 and TBT < LOD-0.7 ng L−1 during the second year. The average BTC concentrations determined with passive samplers varied between 0.08 and 0.53 ng L−1 for MBT, 0.10–0.14 ng L−1 for DBT and 0.05–0.07 ng L−1 for TBT during the first study year and 0.03–0.05 ng L−1 for MBT, 0.02–0.05 ng L−1 for DBT and TBT 0.007–0.013 ng L−1 during the second year. The average BTC concentrations measured in sedimented particles collected with sedimentation traps were between 1.5 and 9.0 ng L−1 for MBT, 0.61–22 ng L−1 for DBT and 0.05–1.8 ng L−1 for TBT during the first study year and 3.0–12 ng L−1 for MBT, 1.7–9.8 ng L−1 for DBT and TBT 0.4–1.2 ng L−1 during the second year. The differences between sampling techniques and the detected BTCs were obvious, e.g., tributyltin (TBT) was detected only in 4%–24% of the grab samples, 50% of the sedimentation traps, and 93% of passive samplers. The BTC concentrations measured with grab and passive sampling suggested hydrological differences between the study years. This was confirmed with flow velocity measurements. However, the annual difference was not observed in BTC concentrations measured in settled particles which suggest that only the dissolved BTC fraction varied. The extreme value analysis suggested that grab sampling and sedimentation trap sampling results contain more extreme peak values than passive sampling. However, all high concentrations are not automatically extreme values but indicates that BTCs are present in surface water in trace concentrations despite not being detected with all sampling techniques.

Monodominant (one species dominates) or polidominant (multiple species dominate) cyanobacterial blooms are pronounced in productive freshwater ecosystems and pose a potential threat to the biota due to the synthesis of toxins. Seasonal changes in cyanobacteria species and cyanometabolites composition were studied in two shallow temperate eutrophic lakes. Data on cyanobacteria biomass and diversity of dominant species in the lakes were combined with chemical and molecular analyses of fifteen potentially toxin-producing cyanobacteria species (248 isolates from the lakes). Anatoxin-a, saxitoxin, microcystins and other non-ribosomal peptides formed the diverse profiles in monodominant (Planktothrix agardhii) and polidominant (Aphanizomenon gracile, Limnothrix spp. and Planktolyngbya limnetica) lakes. However, the harmfulness of the blooms depended on the ability of the dominant species to synthesize cyanometabolites. It was confirmed that P. agardhii produced a greater amount and diverse range of MCs and other NRPs. In the polidominant lake, isolates of the co-dominant A. gracile, L. planctonica and P. limnetica synthesized no or only small amounts of cyanometabolites. In general, the profile of cyanometabolites was greater in cyanobacteria isolates than in environmental samples, indicating a high potential for toxic cyanobacteria bloom.

Refers to Brownification affects phytoplankton community composition but not primary productivity in eutrophic coastal waters: A mesocosm experiment in the Baltic Sea Science of The Total Environment, Volume 841, 1 October 2022, Pages 156510 Kristian Spilling, Eero Asmala, Noora Haavisto, Lumi Haraguchi, Kaisa Kraft, Anne-Mari Lehto, Aleksandra M. Lewandowska, Joanna Norkko, Jonna Piiparinen, Jukka Seppälä, Mari Vanharanta, Anu Vehmaa, Pasi Ylöstalo, Timo Tamminen Climate change is projected to cause brownification of some coastal seas due to increased runoff of terrestrially derived organic matter. We carried out a mesocosm experiment over 15 days to test the effect of this on the planktonic ecosystem. The experiment was set up in 2.2 m3 plastic bags moored outside the Tvärminne Zoological Station at the SW coast of Finland. We used four treatments, each with three replicates: control (Contr) without any manipulation; addition of a commercially available organic carbon additive called HuminFeed (Hum; 2 mg L−1); addition of inorganic nutrients (Nutr; 5.7 µM NH4 and 0.65µM PO4); and a final treatment of combined Nutr and Hum (Nutr+Hum) additions. Water samples were taken daily, and measured variables included water transparency, organic and inorganic nutrient pools, chlorophyll a (Chla), primary and bacterial production and particle counts by flow cytometry.

Highlights •In this paper, the coordination of work with two EU directives in Nordic and Baltic countries is studied. •The potential for synergy effects is reached with varying success in the studied countries. •National legislation and organization of work affect the rate of success with coordination. •Our results confirm conclusions made by the European Commission. Abstract The European Union (EU) Water Framework Directive is of paramount importance for water management. According to the legal text, coordination with other directives like the Floods Directive is imperative and motivated by potential synergy effects. In this paper, the degree to which such coordination is achieved is evaluated for five Nordic and Baltic countries. The evaluation is based on legal documents, management plans, as well as on organizational structure in the five countries. The results show that the coordination between the Water Framework Directive and the Floods Directive (or flood management for Norway's case), have been successful for Estonia and Lithuania, whereas Norway, Finland, and especially Sweden need to improve more.

Marine environmental risk assessments rarely consider the cumulative risk from multiple contaminants and sources. Ships give rise to a range of contaminants, originating from different onboard sources, resulting in contaminant loads to the marine environment. Here, the Ship Traffic Emission Assessment Model (STEAM), in combination with the hydrodynamic and chemical fate model MAMPEC, was used to calculate loads and predicted environmental concentrations (PECs) of metals and polycyclic aromatic hydrocarbons, in four ports. PECs were compared to the predicted no effect concentrations (PNEC) to assess environmental risk from the different onboard sources, both separately and cumulatively. The results show that three out of four ports were subject to unacceptable risk. This study highlights the importance of accounting for multiple contaminant sources when assessing the marine environmental risks of shipping and challenges the suitability of the proposed new international guidelines on how to assess risk of scrubber water discharge.

We present an operational system for multi-sensor data fusion implemented at the Finnish Environment Institute. The system uses Ensemble Kalman filter and smoother algorithms, which are often used for probabilistic analysis of multi-sensor data. Uncertainty and spatial and temporal correlations present in the available observation data are accounted for to obtain accurate and realistic results. To test the data fusion system, daily chlorophyll-a concentration has been modelled across northern shoreline of Gulf of Finland over the period of August 1st – October 31st 2011. Chlorophyll-a data from routine monitoring stations, ferrybox measurements, and data derived from Medium Resolution Imaging Spectrometer (MERIS) instrument on board the ENVISAT satellite has been used as input. The data fusion system demonstrates the use of existing and well-known Ensemble Kalman filtering and smoothing methods for improving water quality monitoring programs and for ensuring compliance with ecological standards. Highlights • Operational data fusion system for coastal water quality monitoring was implemented. • Remote sensing and in-situ data sources are combined using ensemble Kalman smoother. • Result uncertainty is quantified to improve future data collection. • Simple process model captures relevant dynamics in presence of significant data gaps.

This paper reviews the current GeoAI and machine learning applications in hydrological and hydraulic modeling, hydrological optimization problems, water quality modeling, and fluvial geomorphic and morphodynamic mapping. GeoAI effectively harnesses the vast amount of spatial and non-spatial data collected with the new automatic technologies. The fast development of GeoAI provides multiple methods and techniques, although it also makes comparisons between different methods challenging. Overall, selecting a particular GeoAI method depends on the application’s objective, data availability, and user expertise. GeoAI has shown advantages in non-linear modeling, computational efficiency, integration of multiple data sources, high accurate prediction capability, and the unraveling of new hydrological patterns and processes. A major drawback in most GeoAI models is the adequate model setting and low physical interpretability, explainability, and model generalization. The most recent research on hydrological GeoAI has focused on integrating the physical-based models’ principles with the GeoAI methods and on the progress towards autonomous prediction and forecasting systems.

Land use in the Acid Sulphate (AS) soils induces metal and acidity pollution of aquatic ecosystems in coastal areas worldwide. Increasing utilization of AS soils poses increasing risks for deterioration of water bodies. We studied the effects of the coverage of AS soils, together with other catchment land cover attributes, on aquatic assemblages of fish, diatoms and benthic invertebrates in 42 sites along 15 lowland rivers in Finland during three subsequent years. Low pH and increasing content of several metals in the river water were related to high amount of AS soils in the catchment. Especially increasing iron content and water color were correlated to amount of forested areas in the catchment, whereas lower water color values and higher arsenic, chromium and iron concentrations were associated with wetlands. The assemblage structure of all three biological groups was strongly spatially structured among rivers and varied less temporally. The spatial structure of fish and diatoms were strongly affected by the acidic water, whereas invertebrates were more affected by low alkalinity and increasing concentrations of organic matter and iron. Especially fish and benthic invertebrate bioassessment metrics demonstrated for AS soil induced degradation in acidity by responding to low pH and high acidity, while the response from the diatoms index was weaker. The high metal concentrations alone did not seem to add to the degradation in biometrics without further increase in acidification. Our results highlight the importance of recognizing AS soil areas in the catchment to target the mitigation effects. A holistic approach in the mitigation of the adverse effects from AS soils is needed, using several mitigation methods in the catchment, and directing main efforts and protection from human disturbance to catchment areas with the highest proportion of AS soils. Our results suggest that status assessment of AS rivers should be based on multiple biological quality elements and that their metrics could be improved for better detection of impacts from acidity and metal pressures. The effects of metals and their concentrations on aquatic assemblages should be further examined. Highlights • The response of aquatic biological indicators to Acid Sulphate soils were studied. • Low pH and content metals were related to amount of AS soils in the catchment. • The assemblage structure of biological groups was strongly spatially structured. • Bioassessment metrics responded to low pH and high acidity differently. • Status assessment of AS rivers should be based on multiple biological elements.

Concentrations of terrestrial-derived dissolved organic carbon (DOC) in freshwater ecosystems have increased consistently, causing freshwater browning. The mechanisms behind browning are complex, but in forestry-intensive regions browning is accelerated by land drainage. Forestry actions in streamside riparian forests alter canopy shading, which together with browning is expected to exert a complex and largely unpredictable control over key ecosystem functions. We conducted a stream mesocosm experiment with three levels of browning (ambient vs. moderate vs. high, with 2.7 and 5.5-fold increase, respectively, in absorbance) crossed with two levels of riparian shading (70% light reduction vs. open canopy) to explore the individual and combined effects of browning and loss of shading on the quantity (algal biomass) and nutritional quality (polyunsaturated fatty acid and sterol content) of the periphytic biofilm. We also conducted a field survey of differently colored (4.7 to 26.2 mg DOC L-1) streams to provide a ‘reality check’ for our experimental findings. Browning reduced greatly the algal biomass, suppressed the availability of essential polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA), and sterols, but increased the availability of terrestrial-derived long-chain saturated fatty acids (LSAFA). In contrast, loss of shading increased primary productivity, which resulted in elevated sterol and EPA content of the biofilm. The field survey largely repeated the same pattern: biofilm nutritional quality decreased significantly with increasing DOC, as indicated particularly by a decrease of the ω-3:ω-6 ratio and increase in LSAFA content. Algal biomass, in contrast, was mainly controlled by dissolved inorganic nitrogen (DIN) concentration, while DOC concentration was of minor importance. The ongoing browning process is inducing a dramatic reduction in the nutritional quality of the stream biofilm. Such degradation of the major high-quality food source available for stream consumers may reduce the trophic transfer efficiency in stream ecosystems, potentially extending across the stream-forest ecotone. peerReviewed

Highlights • Modest brownification did not affect primary production, but increased bacterial production. • Concentration of inorganic nitrogen was the primary driver for the phytoplankton development. • Brownification benefitted picophytoplankton. Climate change is projected to cause brownification of some coastal seas due to increased runoff of terrestrially derived organic matter. We carried out a mesocosm experiment (15 d) to test the effect of this on the planktonic ecosystem expecting reduced primary production and shifts in the phytoplankton community composition. The experiment was set up in 2.2 m3 mesocosm bags using four treatments, each with three replicates: control (Contr) without any manipulation, organic carbon additive HuminFeed (Hum; 2 mg L−1), inorganic nutrients (Nutr; 5.7 μM NH4 and 0.65 μM PO4), and combined Nutr and Hum (Nutr + Hum) additions. Measured variables included organic and inorganic nutrient pools, chlorophyll a (Chla), primary and bacterial production and particle counts by flow cytometry. The bags with added inorganic nutrients developed a phytoplankton bloom that depleted inorganic N at day 6, followed by a rapid decline in Chla. Brownification did not reduce primary production at the tested concentration. Bacterial production was lowest in the Contr, but similar in the three treatments receiving additions likely due to increased carbon available for heterotrophic bacteria. Picoeukaryotes clearly benefited by brownification after inorganic N depletion, which could be due to more effective nutrient recycling, nutrient affinity, light absorption, or alternatively lower grazing pressure. In conclusion, brownification shifted the phytoplankton community composition towards smaller species with potential effects on carbon fluxes, such as sinking rates and export to the sea floor.

Nopeasti kehittyvissä kaupungeissa on suuri prosenttiosuus läpäisemättömiä pintoja. Nämä pinnat muuttavat rankkasateen veden hulevedeksi, joka kuljettaa haitta-aineita pintavesistöihin ilman käsittelyä. Hulevedet tunnetaan pääasiallisena fosforin (P) hajakuormituslähteenä, ja ne aiheuttavat pintavesien rehevöitymistä, joka heikentää veden laatua. Tässä työssä tutkitaan vuodenaikojen vaikutusta huleveden laatuun tiheästi rakennetussa ympäristössä keskittyen ravinteisiin (typpi ja fosfori) ja kiintoaineisiin (Total Suspended Solids). Työssä arvioidaan erilaisten kansallisten ja paikallisten kriteerien soveltuvuutta huleveden laadun arviointiin. Kaikki tutkitut paikat ovat Tampereen kaupungissa. Nämä ovat kolme Iidesjärveen laskevaa ojaa, kolme Pyhäjärveen laskevaa ojaa ja yksi tulva-altis hulevesiviemäri. TSS:n, sameuden ja ravinteiden laatuparametrien välisiä korrelaatioita hulevedessä on arvioitu kahdentyyppisten mittausten perusteella. Yksi tyyppi on jatkuvatoimiset sameuden ja virtauksen mittaukset, jotka tehdään 2–12 kuukauden jaksoissa vuoden 2021 aikana. Toinen mittaustyyppi on vedenottonäytteiden analyysi kiintoaineen, sameuden ja ravinteiden osalta. Raskasmetallit jätetään tämän työn ulkopuolelle. Hulevesien laadun mallintamiseen ja laskentaan käytettyjen menetelmien yksityiskohtaisen arvioinnin avulla valitaan lineaarinen regressiomenetelmä, jota käytetään sameuden ja kiintoaineen sekä sameuden ja kokonaisfosforin välisten korrelaatioiden määrittämiseen. Sameudella on vahva korrelaatio kiintoaineen kanssa (korrelaation selitysaste R2 > 0,7) kaikissa tutkituissa paikoissa. Sameuden ja kokonaisfosforin väliset korrelaatiot ovat kuitenkin olleet huonoja (R2 < 0,7) yli puolella tutkituista kohteista. Lähtötietojen asianmukainen käsittely parantaa korrelaatioiden luotettavuutta. Lähijärvien kiintoaineen ja kokonaisfosforin kuormituksen määrä on laskettu käyttämällä korrelaatioita ja jatkuvien virtamamittausten dataa. Tutkimustulokset osoittavat, että suurin kuormitus sekä kiintoaineesta että kokonaisfosforista kertyy kaikille tutkituille ojille yhtä lukuun ottamatta kevään aikana. Kuormitusintensiteetti laskee syksyllä 45–96 % välillä (TSS) ja 53–97% välillä (P). Suurin kuorma kevään aikana muodostuu Vuohenojalla (629 417,4 t TSS, 737,7 t P) ja syksyn aikana Vihiojalla (173 844,3 t TSS, 36,8 t P). Hulevesien hallintatoimenpiteet tulee kohdistaa tarkasti näihin kahteen ojaan kriittisimmän vuodenajan eli suurimman vastaavan kuormituksen mukaan. Nämä tulokset auttavat Tampereen kaupungin maankehitysalan ammattilaisia kehittämään parempia hulevesien hallintatoimenpiteitä ja kaavoitusta. Tulokset voivat olla hyödyllisiä myös hulevesien hallintaan tarvittavien käytettävissä olevien resurssien optimoinnissa.

Recent studies have demonstrated that projected climate change will likely enhance nitrogen (N) and phosphorus (P) loss from farms and farmland, with the potential to worsen freshwater eutrophication. Here, we investigate the relative importance of the climate and land use drivers of nutrient loss in nine study catchments in Europe and a neighboring country (Turkey), ranging in area from 50 to 12,000 km2 . The aim was to quantify whether planned large-scale, land use change aimed at N and P loss reduction would be effective given projected climate change. To this end, catchment-scale biophysical models were applied within a common framework to quantify the integrated effects of projected changes in climate, land use (including wastewater inputs), N deposition, and water use on river and lake water quantity and quality for the mid-21st century. The proposed land use changes were derived from catchment stakeholder workshops, and the assessment quantified changes in mean annual N and P concentrations and loads. At most of the sites, the projected effects of climate change alone on nutrient concentrations and loads were small, whilst land use changes had a larger effect and were of sufficient magnitude that, overall, a move to more environmentally focused farming achieved a reduction in N and P concentrations and loads despite projected climate change. However, at Beyşehir lake in Turkey, increased temperatures and lower precipitation reduced water flows considerably, making climate change, rather than more intensive nutrient usage, the greatest threat to the freshwater ecosystem. Individual site responses did however vary and were dependent on the balance of diffuse and point source inputs. Simulated lake chlorophyll-a changes were not generally proportional to changes in nutrient loading. Further work is required to accurately simulate the flow and water quality extremes and determine how reductions in freshwater N and P translate into an aquatic ecosystem response.

A selective method for preconcentration and determination of methylmercury (MeHg) and inorganic mercury (iHg) in natural water samples at the ng L−1 level has been developed. The method involves adsorption of Hg species into a 3D printed metal scavenger and sequential elution with acidic thiourea solutions before ICP-MS determination. Experimental parameters affecting the preconcentration of MeHg and iHg such as the sample matrix, effect of the flow rate on adsorption, eluent composition, and elution mode have been studied in detail. The obtained method detection limits, considering the preconcentration factors of 42 and 93, were found to be 0.05 ng L−1 and 0.08 ng L−1 for MeHg and iHg, respectively. The accuracy of the method was assessed with a certified groundwater reference material ERM-CA615 (certified total iHg concentration 37 ± 4 ng L−1). The determined MeHg concentration was below MDL while iHg concentration was determined to be 41.2 ± 0.5 ng L−1. Both MeHg and iHg were also spiked to natural water samples at 5 ng L−1 concentration and favorable spiking recoveries of 88–97% were obtained. The speciation procedure was successfully applied to two lake water samples where MeHg and iHg concentrations ranged from 0.18 to 0.24 ng L−1 and 0.50–0.62 ng L−1, respectively. The results obtained demonstrate that the developed 3D printed metal scavenger-based method for preconcentration and speciation of Hg is simple and sensitive for the determination of Hg species at an ultra-trace level in water samples. peerReviewed

Amphibian larvae typically inhabit relatively shallow freshwater environments, and within these boundaries there is considerable diversity in the structure of the habitats exploited by different species. This diversity in habitat structure is usually taken into account in relation to aspects such as locomotion and feeding, and plays a fundamental role in the classification of tadpoles into ecomorphological guilds. However, its impact in shaping the sensory worlds of different species is rarely addressed, including the optical qualities of each of these types of water bodies and the challenges and limitations that they impose on the repertoire of visual abilities available for a typical vertebrate eye. In this Perspective article, we identify gaps in knowledge on (1) the role of turbidity and light-limited environments in shaping the larval visual system; and (2) the possible behavioral and phenotypic responses of larvae to such environments. We also identify relevant unaddressed study systems paying special attention to phytotelmata, whose small size allows for extensive quantification and manipulation providing a rich and relatively unexplored research model. Furthermore, we generate hypotheses ranging from proximate shifts (i.e., red-shifted spectral sensitivity peaks driven by deviations in chromophore ratios) to ultimate changes in tadpole behavior and phenotype, such as reduced foraging efficiency and the loss of antipredator signaling. Overall, amphibians provide an exciting opportunity to understand adaptations to visually limited environments, and this framework will provide novel experimental considerations and interpretations to kickstart future research based on understanding the evolution and diversity of strategies used to cope with limited visibility.

Highlights •Agricultural ditches accumulate legacy P and present a risk for water quality. •Mehlich-3 soil test can identify P saturation and total legacy P amount. •Use of a common soil test allows broad scale mapping of high P risk hotspots. Abstract Agricultural soils have accumulated considerable phosphorus (P) reserves along the transport pathways within land-water continuum. Where P concentrations are excessive compared to the soil P sorption capacity, dissolved soluble P can leach to waterbodies. A phosphorus saturation ratio (PSR = P/(Fe + Al)) can be used to classify high and low risk soils based on a commonly applied Mehlich-3 soil test. PSR has been used for acid mineral soils, but in this study it was applied to sediments and drainage ditch bankside samples. Previous published data was converted to PSR and compared to P availability measurements. The results confirmed earlier findings, that a PSR threshold of 0.1 can delineate high and low P risk sites. By quantifying the amount of P in excess to the threshold, legacy P hotspots could be located in the network which would act as an additional source of P inputs to waters. In the study site, two soils contained over 80% of the excess legacy P, presenting a localized long-term risk to water quality. The findings support using the cost effective Mehlich-3 extraction to identify hotspots with most susceptible soil-P to losses and quantify the amount of potentially leachable legacy P.

Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and specific growth rates were higher, and the feed conversion ratio was lower than those grown in RAS. In spinach, there were no significant differences in growth between aquaponic and hydroponic treatments. The concentration of GSM was significantly higher in the roots and MIB in the shoots of spinach grown in aquaponics than in hydroponics. In fish, the concentrations of MIB did not differ, but the concentrations of GSM were lower in aquaponics than in RAS. The onset of nitrification was faster in the aquaponic system than in RAS. In conclusion, spinach grew equally well in aquaponics and hydroponic systems. However, the aquaponic system was better than RAS in terms of onset of nitrification, fish growth, and lower concentrations of GSM in fish flesh. peerReviewed

Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using 13C-labeled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.45±0.21% per year) than in the clear-lake waters (0.07±0.06% per year) or the artificial freshwater medium (0.02±0.02% per year). Complete biodegradation of PE-MP was calculated to last 100-200 years in humic-lake waters, 300-4000 years in clear-lake waters, and 2000-20000 years in the artificial freshwater medium. The concentration of 18:1ω7, characteristic phospholipid fatty acid in Alpha- and Gammaproteobacteria, was a predictor of faster biodegradation of PE. Uncultured Acetobacterioceae and Comamonadacea among Alpha- and Gammaproteobacteria, respectively, were major bacteria related to the biodegradation of PE-MP. Altogether, it seems that microbes in the humic lakes with natural refractory polymers have a better ability to decompose PE than in other waters. peerReviewed

Highlights • Amplicon Sequence Variants (ASVs) are a promising unit for diatom nutrient indices. • Diatom indices based on morphology, ASVs and traits were related to TotP concentrations. • Correlations of indices to TotP was best for ASVs, followed by morphology and traits. We developed and compared the performance of freshwater benthic diatom indices calculated from (i) traditional morphological species identification, (ii) Amplicon Sequence Variants (ASVs) obtained via DNA metabarcoding, and (iii) morphological traits to indicate eutrophication in rivers and lakes in Fennoscandia. Based on the results, we provided recommendations for the future routine use of diatom bioassessment tools in environmental monitoring and assessment. Our results show that ASVs are the most promising candidates to be used in environmental assessment. Indices based on ASVs correlated better with TotP concentrations than morphological taxa data, whereas the trait indices correlated least. We could see by studying the taxonomic assignments of the ASVs that traditional morphotaxa were divided up into several ASVs with different ecological profiles, which explained part of the better index performance and also encourages further studies on diatom diversity and ecological preferences. In general, ASV- and morphotaxon-specific optima differed slightly between streams and lakes, but were significantly correlated with each other. This means that it should be possible to develop a common index that is applicable in both streams and lakes, but boundary values with respect to TotP might need to be set separately for them. More knowledge on diatom traits is required to enable their use for environmental assessment.

Highlights • The invertebrate biodiversity across 261 lakes in the Lake Taihu basin was studied. • The α diversity was consistent with the intermediate disturbance hypothesis. • Significant cross-taxon congruence was found between zooplankton and zoobenthos. • Zoobenthos were more sensitive to nutrient increases compared with zooplankton. • Eutrophication causes biodiversity loss and decreases cross-taxon congruence. Eutrophication is a major problem currently impacting many surface water ecosystems. Impacts of increased nutrient concentrations on biodiversity may differ between different scales, different organism groups, and different trophic states. Surveys at different spatial scales have suggested that biodiversity of different taxa may exhibit significant cross-taxon congruence. In our study, we examined the diversity of zooplankton and zoobenthos across 261 lakes in the Lake Taihu watershed, an area that is undergoing a severe eutrophication process. We tested the cross-taxon congruence in species richness and Shannon-Wiener diversity between zooplankton and zoobenthos along a nutrient gradient across the lakes. Our findings were consistent with the intermediate disturbance hypothesis, considering nutrient input as the disturbance. Also, we found significant cross-taxon congruence between zooplankton and zoobenthos diversities. Our results confirmed that excess nutrient levels resulted in diversity loss and community simplification. Zoobenthos were more sensitive to nutrient increases compared with zooplankton, which decreased cross-taxon congruence because these organism groups did not respond similarly to the anthropogenic disturbance.

Organic matter (OM) other than living phytoplankton is known to affect fluorometric in situ assessments of chlorophyll in lakes. For this reason, calibrating fluorometric measurements for OM error is important. In this study, chlorophyll (Chl) fluorescence was measured in situ in multiple Finnish lakes using two sondes equipped with Chl fluorometers (ex.470/em.650–700 nm). OM absorbance (A420) was measured from water samples, and one of the two sondes was also equipped with in situ fluorometer for OM (ex.350/em.430 nm). The sonde with Chl and OM fluorometers was also deployed continuously on an automated water quality monitoring station on Lake Konnevesi. For data from multiple lakes, inclusion of water colour estimates into the calibration model improved the predictability of Chl assessments markedly. When OM absorbance or in situ OM fluorescence was used in the calibration model, predictability between the in situ Chl and laboratory Chl a assessments was also enhanced. However, correction was not superior to the one done with the water colour estimate. Our results demonstrated that correction with water colour assessments or in situ measurements of OM fluorescence offers practical means to overcome the variation due to OM when assessing Chl in humic lakes in situ.

Highlights • Catchment pollution limits water-related ecosystem services such as food production. • Water flow transports energy, substances and organisms downstream. • Organism behaviour causes bidirectional transport across the catchment. • Humans are modifiers of water and organismal transport. • Coupled transport-ecosystem models are essential for water quality assessment. Food production for a growing world population relies on application of fertilisers and pesticides on agricultural lands. However, these substances threaten surface water quality and thereby endanger valued ecosystem services such as drinking water supply, food production and recreational water use. Such deleterious effects do not merely arise on the local scale, but also on the regional scale through transport of substances as well as energy and biota across the catchment. Here we argue that aquatic ecosystem models can provide a process-based understanding of how these transports by water and organisms as vectors affect – and are affected by – ecosystem state and functioning in networks of connected lakes. Such a catchment scale approach is key to setting critical limits for the release of substances by agricultural practices and other human pressures on aquatic ecosystems. Thereby, water and food production and the trade-offs between them may be managed more sustainably.

Highlights • Reaching SDG 6 requires algal projection models applicable at a global scale. • There are currently no algal projection models similar to the ideal model. • Scientific challenges relate to spatial scales, data availability and uncertainty. • Recent developments provide opportunities for further development. • Global algal projection models will be highly relevant to global policymaking. Algal blooms increasingly threaten lake and reservoir water quality at the global scale, caused by ongoing climate change and nutrient loading. To anticipate these algal blooms, models to project future algal blooms worldwide are required. Here we present the state-of-the-art in algal projection modelling and explore the requirements of an ideal algal projection model. Based on this, we identify current challenges and opportunities for such model development. Since most building blocks are present, we foresee that algal projection models for any lake on earth can be developed in the near future. Finally, we think that algal bloom projection models at a global scale will provide a valuable contribution to global policymaking, in particular with respect to SDG 6 (clean water and sanitation).

The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhynchus mykiss). Three set-ups with triplicate tanks were used: 1. two consecutive fixed bed bioreactors (FF); 2. a fixed bed bioreactor followed by a moving bed bioreactor (FM) and 3. two consecutive moving bed bioreactors (MM). Fish performance was not influenced by the design of the bioreactor, specific growth rate (SGR) being between 1.59 and 1.64% d−1 and feed conversion ratio (FCR) between 0.95 and 0.98. Water nitrite concentration was higher in the FF systems compared to FM and MM systems, whereas the average total ammonia nitrogen concentration (TAN) was not influenced by the treatments. Nitrification rate, which was measured in the laboratory, followed the water nitrite levels, indicating highest total ammonium oxidation rates in the MM systems. UV254 absorbance and total organic carbon (TOC) concentrations were higher in the groups with moving bed systems, indicating accumulation of organic substances in the circulating water. The total volume of particles was higher in the MM systems as compared to the FF systems. The total solids balance was similar in all the bioreactor groups, since the removal of solids by the FBBR backwash was compensated by the drum filter in the FM and MM systems. In general, no significant histopathological difference in gill, kidney, heart and liver tissue were observed between the RAS treatment groups and the flow-through treatment.

The recirculating aquaculture system (RAS) is an ever-developing technology for producing fish with a low environmental impact. However, off-flavors can be a major problem in RAS fish production. Off-flavor compounds are of microbial origin and are accumulated in fish flesh. They typically cause a musty and earthy taste and odor, which consumers find unacceptable. Here we hypothesized that oxidizing compounds such as ozone (O3), hydrogen peroxide (H2O2), and their combinations, referred to as advanced oxidation processes (AOP)s, can remove or decrease these compounds in water and prevent their accumulation in fish. In this study, four different oxidative treatments (O3 low (0.4 mg O3 L−1), O3 high (0.8 mg O3 L−1), H2O2 (0.15 µl L−1), AOP (0.4 mg O3 L−1 & H2O2 0.10 µl L−1), and controls were applied to 10 experimental RASs for four months. The results showed that the treatments can reduce dissolved organic carbon (DOC) and the off-flavor compounds (geosmin, GSM and 2-methyl isoborneol, MIB) in circulating water, but they were not able to prevent the accumulated off-flavors in fish flesh below the sensory threshold. There was no significant difference in off-flavor removal between the treatments, which indicates that O3 treatment was ineffective in these conditions. However, H2O2 could still reduce the off-flavor concentrations in water. peerReviewed

The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples. We also used microscopy to identify the shapes of the main MPs. This allowed us to create a teaching set of samples to be characterized with our optical method. With the developed method, we clearly show that MPs from common plastics, such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyethylene (PE), are present in wastewater sludge and can be identified. Additionally, the results also indicate that the density of the plastics, which influences the sedimentation, is an essential parameter to consider in optical detection of microplastics in complex natural environments. All of the methods are in good agreement, thus validating the optics-based solution. peerReviewed

Kaivostoiminnassa mineraalien rikastuksessa muodostuva rikastushiekka sijoitetaan rikastus-hiekka-altaisiin, joiden haitallisten aineiden päästöt pohja- tai pintavesiin aiheutuvat altaan pohja- ja patorakenteiden läpi kulkeutuvan suotoveden leviämisestä ympäristöön tai käsiteltyjen jätevesien juoksutuksesta alapuoliseen vesistöön. Haitallisten aineiden liukeneminen rikastushiekasta suotoveteen ja niiden kulkeutuminen rikastushiekka-altaan ympäristöön ovat seurausta rikastushiekassa ja maaperässä tapahtuvista biologisista, kemiallisista ja fysikaalisista reaktioista haitallisten aineiden ja rikastushiekassa ja maaperässä olevien veden, huokosilman ja kiinteän aineen välillä. Näitä reaktioita säätelevät reaktio-olosuhteet, jotka ovat riippuvaisia ympäristön olosuhteista, kuten veden määrästä ja lämpötilasta. Suotoveden leviämistä rikastushiekka-altaan ympäristöön voidaan estää tai hidastaa suojapumppauksella, joka on pilaantuneen tai pilaantumisen vaarassa olevan pohjaveden aktiivinen kunnostamismenetelmä. Kevitsan kaivoksen toiminnan aikaisessa pohjavesitarkkailussa on havaittu, että vähärikkisen rikastushiekka-altaan A suotovedet ovat osittain sekoittuneet pohjaveteen allasalueen lähiympäristössä aiheuttaen näin joidenkin haitallisten aineiden pitoisuuksien nousua verrattuna alueen taustapitoisuuksiin. Tehtyjen mallinnusten tulosten pohjalta laadittiin suojapumppaussuunnitelma, jota noudattaen suurin osa rikastushiekka-altaan A suotovedestä saadaan kerättyä rikastushiekka-altaan A luoteiskulman padon läheisyyteen asennettujen 12 suotovedenkeräyskaivojen avulla ja johdettua käsittelyyn. Suojapumppauksilla pyritään estämään rikastushiekka-altaan A lähiympäristön veden laadun heikkeneminen ja pienentämään Mataraojan pilaantumisen riskiä. Diplomityön tavoitteena oli rikastushiekka-altaan A suotovesien suojapumppauksen aloituksen ja seurannan suunnittelu ja toteuttaminen. Seurannan tulosten perusteella arvioitiin pumppausjärjestelyn soveltuvuutta alueelle. Työssä laadittiin suojapumppausten alkuvaiheen tarkkailusuunnitelma ja toteutettiin tarkkailu. Suojapumppausten vaikutusta rikastushiekka-altaan A ympäristössä seurattiin vesinäytteenotolla ja vedenpinnan korkeusmittauksilla. Vesianalyysitulosten tulkinnassa huomioitiin alueen taustapitoisuudet ja tuotannon aikaisen tarkkailun tulokset. Haitallisten aineiden pitoisuuksia verrattiin asetusten 1040/2006 ja 1022/2006 mukaisiin ympäristönlaatunormeihin. Tutkimusalueella useimpien suotovedenkeräyskaivojen ja pohjavesiputkien vesien kloridin ja nikkelin pitoisuudet ylittivät ympäristönlaatunormin 1040/2006 vertailupitoisuuden, ja lähes kolmasosa ympäristönlaatunormin 1022/2006 vertailupitoisuuden. Tarkastelujakson aikana suojapumppauksilla ei ollut vaikutusta tutkimusalueen haitallisten aineiden pitoisuuksiin. Nykyisellä pumppausjärjestelyllä ei saavuteta haluttua pohjavedenpinnan alenemaa suotovedenke-räyskaivoissa eikä siten riittävän merkittävää ja tehokasta suojapumppausten vaikutusta rikas-tushiekka-altaan luoteiskulman ympäristön pohjavesiin. Tarkempien johtopäätösten tekemiseksi pumppausten vaikutuksista tarvitaan ympäristön haitallisten aineiden pitoisuuksien muutosten ja vedenpintojen korkeuksien pidempiaikaista, todennäköisesti vuosia kestävää seurantaa. Suojapumppausjärjestelyn tekniseen toteutukseen tulisi tehdä parannuksia: pumppujen lukumäärää ja niiden pumppaustehoja on kasvatettava ja pumppausten automatisoinnin mahdollisuuksia on tutkittava. The tailings from the mineral enrichment in the mining industry are placed in the basin-like tailings storage facilities. The groundwater and the surface waters near the facility can be contaminated via the seepage passing through the bottom of the dam and through the dam structures to the surrounding environment, or via discharging of the treated wastewater into the downstream water. The dissolution of the contaminants from the tailings into the seepage, and their transport into the vicinity of the tailings storage facility, are the result of the biological, chemical and physical reactions between the contaminants and the water, porous air and solids in the tailings and the soil. The reactions are connected to the environmental conditions, e.g. the water content and the temperature of the matrix. The spreading of the seepage to the vicinity of the tailings basin can be prevented or slowed down by protective pumping, pump-and-treat method, which is an active remediation method for contaminated, or at risk of being contaminated, groundwater. In the groundwater monitoring during the operation of the Kevitsa mine, it has been found that the seepage from the low-sulfur tailings storage facility A is partially mixed with the groundwater in the vicinity of the basin, thus causing an increase in some of the contaminant concentrations compared to the background concentrations in the area. Based on the results of the numerical modelling, a seepage capture plan was compiled. According to the modelling, most of the seepage from the tailings basin A can be collected via the 12 seepage capture wells and lead to the treatment. The purpose is to prevent the declining of the water quality in the vicinity of the tailings storage facility A and to reduce the risk of contamination of Mataraoja via pump-and-treat method. The goal of this thesis was to plan and implement the starting and monitoring of the pumping of the seepage of the tailings storage facility A. The suitability of the pumping arrangement for the area was assessed based on the results of the monitoring. A monitoring plan for the initial phase of protective pumping was compiled and implemented. The effects of the pumping on the surroundings of the tailings storage facility A were monitored by water sampling and water level elevation measurements. In the interpretation of the water analysis results the background concentrations and the results of monitoring during production were taken into consideration. Concentrations of the contaminants were compared with the environmental quality standards in the Decrees 1040/2006 and 1022/2006. In the study area, the concentrations of chloride and nickel in the waters of most seepage collection wells and groundwater observation pipes exceeded the environmental quality standard in 1040/2006, and almost one third the environmental quality standard in 1022/2006. During the period examined, the pumpings had no effect on the concentrations of the contaminants in the study area. With the current pumping arrangement, the desired water level reduction in the seepage collection wells will not be achieved, nor the desired impact of sufficient size and efficiency on the groundwater surrounding the northwest corner of the facility. In order to make valid conclusions of the effectiveness of the pump-and-treat method, longer-term, probably years-long monitoring of changes in the concentration of pollutants in the environment and in the heights of the water levels is needed. Some improvements for the technical implementation are recommended to be made: the amount and the capacities of the pumps must be increased, and the possibilities of automation of the pumpings should be examined.

A recent global meta‐analysis reported a decrease in terrestrial but increase in freshwater insect abundance and biomass (van Klink et al., Science 368, p. 417). The authors suggested that water quality has been improving, thereby challenging recent reports documenting drastic global declines in freshwater biodiversity. We raise two major concerns with the meta‐analysis and suggest that these account for the discrepancy with the declines reported elsewhere. First, total abundance and biomass alone are poor indicators of the status of freshwater insect assemblages, and the observed differences may well have been driven by the replacement of sensitive species with tolerant ones. Second, many of the datasets poorly represent global trends and reflect responses to local conditions or nonrandom site selection. We conclude that the results of the meta‐analysis should not be considered indicative of an overall improvement in the condition of freshwater ecosystems. This article is categorized under: Water and Life > Conservation, Management, and Awareness, Relying on abundance or biomass and examining nonrepresentative datasets limits our ability to infer the condition of freshwater insect communities globally. Photo by Jeremy Monroe, Freshwaters Illustrated: a caddisfly larva from an Oregon Coastal stream, USA (Limnephilidae: Dicosmoecus sp.)., Federal Agency for Nature Conservation (BfN) http://dx.doi.org/10.13039/100010606, NSF Macrosystems Biology Program, Leibniz‐Gemeinschaft http://dx.doi.org/10.13039/501100001664

Highlights • We compared fungi, invertebrates and diatoms in model-based stream bioassessment. • Fungal models virtually equaled the overall best model in precision and accuracy. • Fungi were superior in identifying streams degraded by multiple stressors. • Results strongly support the use of microbial communities in stream bioassessment. Degradation of freshwater ecosystems requires efficient tools for assessing the ecological status of freshwater biota and identifying potential cause(s) for their biological degradation. While diatoms and macroinvertebrates are widely used in stream bioassessment, the potential utility of microbial communities has not been fully harnessed. Using data from 113 Finnish streams, we assessed the performance of aquatic leaf-associated fungal decomposers, relative to benthic macroinvertebrates and diatoms, in modelling-based bioassessment. We built multi-taxon niche -type predictive models for fungal assemblages by using genus-based and sequence-based identification levels. We then compared the models’ precision and accuracy in the prediction of reference conditions (number of native taxa) to corresponding models for macroinvertebrates and diatoms. Genus-based fungal model nearly equalled the accuracy and precision of our best model (macroinvertebrates), whereas the sequence-based model was less accurate and tended to overestimate the number of taxa. However, when the models were applied to streams disturbed by anthropogenic stressors (nutrient enrichment, sedimentation and acidification), alone or in combination, the sequence-based fungal assemblages were more sensitive than other taxonomic groups, especially when multiple stressors were present. Microbial leaf decomposition rates were elevated in sediment-stressed streams whereas decomposition attributable to leaf-shredding macroinvertebrates was accelerated by nutrients and decelerated by sedimentation. Comparison of leaf decomposition results to model output suggested that leaf decomposition rates do not detect effectively the presence of multiple simultaneous disturbances. The rapid development of global microbial database may soon enable species-level identification of leaf-associated fungi, facilitating a more precise and accurate modelling of reference conditions in streams using fungal communities. This development, combined with the sensitivity of aquatic fungi in detecting the presence of multiple human disturbances, makes leaf-associated fungal assemblages an indispensable addition in a stream ecologist’s toolbox.

Contradictory results for the long-term evolution of nitrogen and phosphorus concentrations in waters discharging from drained peatland forests need reconciliation. We gathered long-term (10–29 years) water quality data from 29 forested catchments, 18 forestry-drained and 11 undrained peatlands. Trend analysis of the nitrogen and phosphorus concentration data indicated variable trends from clearly decreasing to considerably increasing temporal trends. While the variations in phosphorus concentration trends over time did not correlate with any of our explanatory factors, trends in nitrogen concentrations correlated positively with tree stand volume in the catchments and temperature sum. A positive correlation of increasing nitrogen concentrations with temperature sum raises concerns of the future evolution of nitrogen dynamics under a warming climate. Furthermore, the correlation with tree stand volume is troublesome due to the generally accepted policy to tackle the climate crisis by enhancing tree growth. However, future research is still needed to assess which are the actual processes related to stand volume and temperature sum that contribute to increasing TN concentrations.

Tämä tutkimus on toteutettu osana kansainvälistä ”Vedet ja ihmiset kohtaavat - opi, toimi ja vaikuta ”SEVIRA-hanketta (2018–2022), jonka tavoitteena on edistää Suomen ja Venäjän välistä yhteistyötä Suomenlahden alueella. Rahoitus on saatu Euroopan naapuruuspolitiikan rahoitusvälineestä (ENI CBC). SEVIRA-hankkeen toteuttavat Suomen ympäristökeskus SYKE, Kaakkois-Suomen ELY-keskus sekä Venäjän Tiedeakatemian Limnologinen Instituutti, kansalaisjärjestö Ecocentrum ja Luoteis Venäjän Hydrometeorologinen Monitorointikeskus. Hanke tähtää monin keinoin Suomenlahden tilan parantamiseen ja se kohdentuu kolmen Suomen ja Venäjän välisen raja-alueen jokiin. Hankkeen laajana tavoitteena on alan parhaiden asiantuntijoiden toimesta lisätä ihmisten tietoisuutta sekä kehittää veden virtaaman ja veden laadun seurantaa uusien laitteiden, mallintamisen, koulutuksen ja kansalaisseurannan parantamisen kautta Virojoen, Rakkolanjoen ja Sestrajoen alueella. SEVIRA-hankkeen tärkeänä tavoitteena on osallistaa kansalaisia alueensa vesien tilan parantamiseen. Suomessa toteutettiin taloudellisen arvottamisen menetelmin kaksi laajaa asukaskyselyä; vuodenvaihteessa 2020–2021 Virojoen ja alkuvuonna 2021 Rakkolanjoen vesistön alueilla. SEVIRA-hanke toi ajankohtaista tietoa alueen asukkaiden mielipiteistä ja osallistumishalukkuudesta alueen suunnittelijoille ja päättäjille, sillä samanaikaisesti kyselytutkimuksen ollessa käynnissä vesienhoitosuunnitelmat olivat alueella virallisesti esillä ja kommentoitavana. Asukaskyselyiden tuloksia esiteltiin Kaakkois-Suomen ELY-keskuksen vesien- ja merenhoidon yhteistyöryhmän kokouksessa 31.5.2021. Tässä raportissa kuvataan Rakkolanjoen vesistön alueelle tehdyn tutkimuksen tulokset. Virojoen vesistöalueella toteutettu tutkimus tuloksineen on esitetty omassa raportissaan (ks. Väisänen ym. 2021).

Colored dissolved organic matter (CDOM) in marine environments impacts primary production due to its absorption effect on the photosynthetically active radiation. In coastal seas, CDOM originates from terrestrial sources predominantly and causes spatial and temporal changing patterns of light absorption which should be considered in marine biogeochemical models. We propose a model approach in which Earth Observation (EO) products are used to define boundary conditions of CDOM concentrations in an ecosystem model of the Baltic Sea. CDOM concentrations in riverine water derived from EO products serve as forcing for the ecosystem model. For this reason, we introduced an explicit CDOM state variable in the model. We show that the light absorption by CDOM in the model can be improved considerably in comparison to approaches where CDOM is estimated from salinity. The model performance increases especially with respect to spatial CDOM patterns due to the consideration of single river properties. A prerequisite is high-quality CDOM data with sufficiently high spatial resolution which can be provided by the new generation of ESA satellite sensor systems (Sentinel 2 MSI and Sentinel 3 OLCI). Such data are essential, especially when local differences in riverine CDOM concentrations exist.

Maatalous ja metsätalous vaikuttavat Suomen vesistöjen tilaan laaja-alaisesti. Maatalouden vesistövaikutukset ovat seurausta etenkin vuotuisista lannoituksista ja maanmuokkauksesta. Metsätalouden vesistövaikutukset taas johtuvat erityisesti valuma-alueiden ojituksista ja uomien perkaamisesta sekä hakkuista. Molemmilla sektoreilla tehokas maankuivatus ja maaperän muokkaus aiheuttavat ravinteiden, kiintoaineen ja humuksen hajakuormitusta vesistöihin. Hajakuormituksen vesistövaikutukset ilmenevät rehevöitymisenä ja vesistöjen tummumisena, uomien liettymisenä ja ekologisen tilan heikkenemisenä. EU:n vesipuitedirektiivi edellyttää vesistövaikutusten seurantaa, jos maankäytön aiheuttama hajakuormitus muodostaa merkittävän riskin sille, että hyvän ekologisen tilan ympäristötavoitetta ei saavuteta. Maatalouden ja metsätalouden hajakuormituksen vaikutuksia vedenlaatuun ja vesien ekologiseen tilaan on seurattu valtakunnallisesti vuodesta 2008 lähtien yli sadan järvi- ja jokikohteen muodostaman ns. MaaMet-seurantaverkon avulla. Raporttiin koottiin MaaMet-seurantaohjelman vuosien 2008–2020 seurannan tulokset. Työn pääpaino on ekologisen tilan, vedenlaadun ja biologisten tekijöiden, ja maankäytön välisten yhteyksien sekä ajallisen vaihtelun tarkastelussa. Tilan arviointi perustui vesienhoidon kolmannen suunnittelukierroksen luokittelukriteereihin. Seurantaverkon tulokset rinnastettiin ihmistoiminnan vähiten vaikuttamien ympäristöhallinnon seurantakohteiden tuloksiin. Maatalousalueiden jokia ja -järviä luonnehtivat korkeat ravinnepitoisuudet, selvästi muuttuneet biologiset yhteisöt ja heikentynyt ekologinen tila. Valuma-alueen peltoisuus selitti merkittävästi vedenlaadun ja biologisten muuttujien vuosien 2008–2020 keskimääräistä tilaa. Peltojen suurempi osuus valuma-alueella johti heikompaan vedenlaatuun ja ekologiseen tilaan. Metsätalousalueiden jokikohteilla ja järvissä tapahtuneet muutokset olivat suhteessa pienempiä kuin maatalousalueilla, mutta myös niiden ekologinen tila oli selvästi heikentynyt. Metsätalouskohteita luonnehtivat etenkin korkeat orgaanisen typen ja hiilen pitoisuudet, jotka liittyivät valuma-alueen turvemaiden ojituksiin ja metsien hakkuisiin. Mitä suurempi osuus turvemaista oli ojitettu, sitä heikompi vedenlaatu jokivesissä oli. Metsätalouden vaikutukset ilmenivät voimakkaammin jokikohteilla kuin järvissä. Yhtenäistä muutosta vedenlaadussa ja ekologisessa tilassa ei seurantajaksolla 2008–2020 havaittu. Yksittäisillä jokikohteilla ja järvillä ekologinen tila oli muuttunut vaihtelevasti. Koska ekologisessa tilassa ei havaittu yhtenäistä paranevaa trendiä, ovat vesiensuojelutoimet todennäköisesti olleet riittämättömiä ja huonosti kohdennettuja. Jatkossa seurantaa tulisi kehittää erityisesti metsätalouden toimenpiteiden vaikutusten laajuuden ja intensiteetin tarkemmaksi kuvaamiseksi. Raportissa käsitellään hajakuormitettujen pintavesien vesiensuojelun ja -hoidon kehitystarpeita. Seuranta-aineiston arvo kasvaa seurantavuosien karttuessa. MaaMet-seurantaverkko tuottaa ensi-arvoisen tärkeää valtakunnallista tietoa maatalouden ja metsätalouden hajakuormituksen vaikutuksista vesien tilaan. Valtakunnallisesti kattava ja ajallisesti jatkuva vesistövaikutusten seuranta on välttämätön edellytys kustannustehokkaalle vesienhoidon suunnittelulle.

Highlights • TOC concentrations in waters from drained and undrained peatlands were compared. • TOC concentrations from drained peatlands were higher than from undrained peatlands. • Tree stand volume correlated positively with increasing TOC concentrations. • Intensifying wood production may enhance water brownification. Total Organic Carbon (TOC) concentrations in stream waters from peat-covered catchments have increased over the last 15–25 years, resulting in large-scale brownification of lakes and rivers in high latitudes. While this increase has primarily been attributed to decreased acid deposition and climatic warming in most regions, we studied whether peatland drainage in forested catchments has contributed to the increasing TOC concentrations. We analysed the spatial variability of average TOC concentrations from a total of 133 peatland dominated catchments in Sweden and Finland, of which 62 were pristine and 71 were drained during the last century. In addition, we performed a trend analysis on 37 catchments for which long-term data were available. We found about 14 mg l−1 higher TOC concentrations in streams discharging from drained than undrained sites in southern latitudes, and about 8 mg l−1 higher concentrations from drained sites in northern latitudes. Trend analysis did not indicate significant differences in TOC concentration trends between drained and undrained catchments but indicated that tree stand volume correlated with increasing trends. This supports earlier findings in that the general increase in forest cover and biomass that has occurred in high latitudes during the last decades is another factor that has contributed to brownification.

Tämä tutkimus on toteutettu osana kansainvälistä ”Vedet ja ihmiset kohtaavat - opi, toimi ja vaikuta” SEVIRA-hanketta (2018–22), jonka tavoitteena on edistää Suomen ja Venäjän välistä yhteistyötä Suomenlahden alueella. Rahoitus on saatu Euroopan naapuruuspolitiikan rahoitusvälineestä (ENI CBC). SEVIRA-hankkeen toteuttavat Suomen ympäristökeskus SYKE, Kaakkois-Suomen ELY-keskus sekä Venäjän Tiedeakatemian Limnologinen Instituutti, kansalaisjärjestö Ecocentrum ja LuoteisVenäjän Hydrometeorologinen Monitorointikeskus. Hanke tähtää monin keinoin Suomenlahden tilan parantamiseen ja se kohdentuu kolmen Suomen ja Venäjän välisen raja-alueen jokiin. Hankkeen laajana tavoitteena on alan parhaiden asiantuntijoiden toimesta lisätä ihmisten tietoisuutta sekä kehittää veden virtaaman ja veden laadun seurantaa uusien laitteiden, mallintamisen, koulutuksen ja kansalaisseurannan parantamisen kautta Virojoen, Rakkolanjoen ja Sestrajoen alueella. SEVIRA-hankkeen tärkeänä tavoitteena on osallistaa kansalaisia alueensa vesien tilan parantamiseen. Suomessa toteutettiin taloudellisen arvottamisen menetelmin kaksi laajaa asukaskyselyä vuodenvaihteessa 2020–21 ja alkuvuonna 2021 Virojoen ja Rakkolanjoen vesistön alueilla. SEVIRA-hanke toi ajankohtaista tietoa alueen asukkaiden mielipiteistä ja osallistumishalukkuudesta alueen suunnittelijoille ja päättäjille, sillä samanaikaisesti kyselytutkimuksen ollessa käynnissä vesienhoidon suunnitelmat olivat alueella virallisesti esillä ja kommentoitavana. Arvottamistutkimusten tuloksia esiteltiin alueen vesienhoidon yhteistyöryhmässä toukokuun lopussa 2021.

Highlights • Nutrient and SS estimations were predicted by comparing different approaches. • Peatland drainage strongly affected TN, TP, and SS loads and concentrations. • Uncertainty in estimates captured 29–90% of measured TN, TP, and SS values. • The uncertainty in export coefficients decreased with catchment size. Maintaining and improving surface water quality requires knowledge of nutrient and sediment loads due to past and future land-use practices, but historical data on land cover and its changes are often lacking. In this study, we tested whether land-use-specific export coefficients can be used together with satellite images (Landsat) and/or regional land-use statistics to estimate riverine nutrient loads and concentrations of total nitrogen (TN), total phosphorus (TP), and suspended solids (SS). The study area, Simojoki (3160 km2) in northern Finland, has been intensively drained for peatland forestry since the 1960s. We used different approaches at multiple sub-catchment scales to simulate TN, TP, and SS export in the Simojoki catchment. The uncertainty in estimates based on specific export coefficients was quantified based on historical land-use changes (derived from Landsat data), and an uncertainty boundary was established for each land-use. The uncertainty boundary captured at least 60% of measured values of TN, TP, and SS loads or concentrations. However, the uncertainty in estimates compared with measured values ranged from 7% to 20% for TN, 0% to 18% for TP, and 13% to 43% for SS for different catchments. Some discrepancy between predicted and measured loads and concentrations was expected, as the method did not account for inter-annual variability in hydrological conditions or river processes. However, combining historical land-use change estimates with simple export coefficients can be a practical approach for evaluating the influence on water quality of historical land-use changes such as peatland drainage for forest establishment.

Nordic water bodies face multiple stressors due to human activities, generating diffuse loading and climate change. The ‘green shift’ towards a bio-based economy poses new demands and increased pressure on the environment. Bioeconomy-related pressures consist primarily of more intensive land management to maximise production of biomass. These activities can add considerable nutrient and sediment loads to receiving waters, posing a threat to ecosystem services and good ecological status of surface waters. The potential threats of climate change and the ‘green shift’ highlight the need for improved understanding of catchment-scale water and element fluxes. Here, we assess possible bioeconomy-induced pressures on Nordic catchments and associated impacts on water quality. We suggest measures to protect water quality under the ‘green shift’ and propose ‘road maps’ towards sustainable catchment management. We also identify knowledge gaps and highlight the importance of long-term monitoring data and good models to evaluate changes in water quality, improve understanding of bioeconomy-related impacts, support mitigation measures and maintain ecosystem services.

In the future, the world is expected to rely increasingly on renewable biomass resources for food, fodder, fibre and fuel. The sustainability of this transition to bioeconomy for our water systems depends to a large extent on how we manage our land resources. Changes in land use together with climate change will affect water quantity and quality, which again will have implications for the ecosystem services provided by water resources. These are the main topics of this Ambio special issue on “Environmental effects of a green bio-economy”. This paper offers a summary of the eleven papers included in this issue and, at the same time, outlines an approach to quantify and mitigate the impacts of bioeconomy on water resources and their ecosystem services, with indications of useful tools and knowledge needs.

Microbial biofilters control water quality and enable the overall function of recirculation aquaculture systems (RAS). Changes in environmental conditions can affect the abundance and interactions of the diverse microbial populations of the biofilter, affecting nitrification of harmful ammonium and thus fish health. Here, we examined the effect of different application frequencies (0, 1, 2 and 4 times per week) of a common disinfectant, peracetic acid (PAA, applied 1.1 mg l−1 twice per day), on biofilter microbial communities, focusing especially on nitrifying microbial groups and using a high throughput sequencing of 16S rRNA gene and quantitative PCR (qPCR). In addition, we measured biofilter nitrification rates, water quality parameters, and fish performance. Although PAA additions did not significantly change the overall microbial community composition or abundance, the abundance of ammonia-oxidizing bacteria (AOB) and nitrate-oxidizing bacteria (NOB) first decreased at the beginning of the experiment but increased in numbers towards the end of the experiment with frequent PAA applications. PAA application decreased the nitrification rate, but increased the water quality in terms of reduced ammonium levels. PAA application did not significantly affect fish growth, but higher mortality was observed with the highest PAA application level of 4 times per week. These results suggest that when applied before the fish tank, PAA can be used for temporary water quality improvement without disturbing microbial communities. However, the application frequency required for persistent water quality improvement caused increased mortality. peerReviewed

In near future it is assumable that automated unmanned aerial platforms are coming more common. There are visions that transportation of different goods would be done with large planes, which can handle over 1000 kg payloads. While these planes are used for transportation they could similarly be used for remote sensing applications by adding sensors to the planes. Hyperspectral imagers are one this kind of sensor types. There is need for the efficient methods to interpret hyperspectral data to the wanted water quality parameters. In this work we survey the performance of neural networks in the prediction of water quality parameters from remotely sensed hyperspectral data in freshwater basins. The hyperspectral data consists of 36 bands in the wavelength range of 508–878 nm and the water quality parameters to be predicted are temperature, conductivity, turbidity, Secchi depth, blue-green algae, chlorophyll-a, total phosphorus, acidity and dissolved oxygen. The objective of this investigation was to study the behaviour of different types of neural networks with this kind of data. Study is a survey of the operation of neural networks on this problem, which can be used as a basis for the design of a more comprehensive study. The neural network types examined were multilayer perceptron and 1-, 2- and 3-dimensional convolutional neural networks with the effect of scaling the hyperspectral data with standard or min-max -scaler recorded. We also investigated investigated how the prediction of individual water quality parameter depends on whether the neural network model is done solely with respect to this one parameter or with several parameters predicted simultaneously with the same model. The results of the correspondence between the predicted and measured water quality parameters were presented with normalized root mean square error, Pearson correlation coefficient and coefficient of determination. The best models were obtained the 2-dimensional convolutional neural networks with standard scaling made separately for each parameter. The parameters showing good predictability were conductivity, turbidity, Secchi-depth, blue-green algae, chlorophyll-a and total phosphorus, for which the coefficient of determination was at least 0.96 (apart from Secchi-depth even 0.98). peerReviewed