Browsing by Subject "eutrophication"

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  • Harrison, Jesse P.; Chronopoulou, Panagiota-Myrsini; Salonen, Iines S.; Jilbert, Tom; Koho, Karoliina A. (2021)
    Metabarcoding analyses of bacterial and eukaryotic communities have been proposed as efficient tools for environmental impact assessment. It has been unclear, however, to which extent these analyses can provide similar or differing information on the ecological status of the environment. Here, we used 16S and 18S rRNA gene metabarcoding to compare eutrophication-induced shifts in sediment bacterial and eukaryotic community structure in relation to a range of porewater, sediment and bottom-water geochemical variables, using data obtained from six stations near a former rainbow trout farm in the Archipelago Sea (Baltic Sea). Shifts in the structure of both community types were correlated with a shared set of variables, including porewater ammonium concentrations and the sediment depth-integrated oxygen consumption rate. Distance-based redundancy analyses showed that variables typically employed in impact assessments, such as bottom water nutrient concentrations, explained less of the variance in community structure than alternative variables (e.g., porewater NH4+ inventories and sediment depth-integrated O2 consumption rates) selected due to their low collinearity (up to 40 vs. 58% of the variance explained, respectively). In monitoring surveys where analyses of both bacterial and eukaryotic communities may be impossible, either 16S or 18S rRNA gene metabarcoding can serve as reliable indicators of wider ecological impacts of eutrophication.
  • McCrackin, Michelle L.; Muller-Karulis, Baerbel; Gustafsson, Bo G.; Howarth, Robert W.; Humborg, Christoph; Svanbäck, Annika; Swaney, Dennis P. (2018)
    There is growing evidence that the release of phosphorus (P) from legacy stores can frustrate efforts to reduce P loading to surface water from sources such as agriculture and human sewage. Less is known, however, about the magnitude and residence times of these legacy pools. Here we constructed a budget of net anthropogenic P inputs to the Baltic Sea drainage basin and developed a three-parameter, two-box model to describe the movement of anthropogenic P though temporary (mobile) and long-term (stable) storage pools. Phosphorus entered the sea as direct coastal effluent discharge and via rapid transport and slow, legacy pathways. The model reproduced past waterborne P loads and suggested an similar to 30-year residence time in the mobile pool. Between 1900 and 2013, 17 and 27 Mt P has accumulated in the mobile and stable pools, respectively. Phosphorus inputs to the sea have halved since the 1980s due to improvements in coastal sewage treatment and reductions associated with the rapid transport pathway. After decades of accumulation, the system appears to have shifted to a depletion phase; absent further reductions in net anthropogenic P input, future waterborne loads could decrease. Presently, losses from the mobile pool contribute nearly half of P loads, suggesting that it will be difficult to achieve substantial near-term reductions. However, there is still potential to make progress toward eutrophication management goals by addressing rapid transport pathways, such as overland flow, as well as mobile stores, such as cropland with large soil-P reserves.
  • Meier, H. E. Markus; Edman, Moa; Eilola, Kari; Placke, Manja; Neumann, Thomas; Andersson, Helén C.; Brunnabend, Sandra-Esther; Dieterich, Christian; Frauen, Claudia; Friedland, René; Gröger, Matthias; Gustafsson, Bo G.; Gustafsson, Erik; Isaev, Alexey; Kniebusch, Madline; Kuznetsov, Ivan; Müller-Karulis, Bärbel; Naumann, Michael; Omstedt, Anders; Ryabchenko, Vladimir; Saraiva, Sofia; Savchuk, Oleg P. (2019)
    Following earlier regional assessment studies, such as the Assessment of Climate Change for the Baltic Sea Basin and the North Sea Region Climate Change Assessment, knowledge acquired from available literature about future scenario simulations of biogeochemical cycles in the Baltic Sea and their uncertainties is assessed. The identification and reduction of uncertainties of scenario simulations are issues for marine management. For instance, it is important to know whether nutrient load abatement will meet its objectives of restored water quality status in future climate or whether additional measures are required. However, uncertainties are large and their sources need to be understood to draw conclusions about the effectiveness of measures. The assessment of sources of uncertainties in projections of biogeochemical cycles based on authors' own expert judgment suggests that the biggest uncertainties are caused by (1) unknown current and future bioavailable nutrient loads from land and atmosphere, (2) the experimental setup (including the spin up strategy), (3) differences between the projections of global and regional climate models, in particular, with respect to the global mean sea level rise and regional water cycle, (4) differing model-specific responses of the simulated biogeochemical cycles to long-term changes in external nutrient loads and climate of the Baltic Sea region, and (5) unknown future greenhouse gas emissions. Regular assessments of the models' skill (or quality compared to observations) for the Baltic Sea region and the spread in scenario simulations (differences among projected changes) as well as improvement of dynamical downscaling methods are recommended.
  • Rousi, Heta; Korpinen, Samuli; Bonsdorff, Erik (Frontiers Media, 2019)
    Frontiers in Marine Science
    We studied the spatio-temporal impacts of physical and chemical environmental variables (depth, sediment type, salinity, temperature, oxygen, total phosphorus, and total nitrogen) on soft-sediment zoobenthos in the open coastal Gulf of Finland during 2001–2015. The study included 55 sampling-stations covering the east-west gradient of the Finnish coastal zone. The chosen environmental variables significantly influenced the distribution of the species in space and over time. Some zoobenthic taxa formed assemblages with each other, occurring in similar environmental conditions, while Gammarus spp. and Chironomidae clearly differed from other taxa in regards to ecological requirements. We showed the critical influence of oxygen (normoxia, hypoxia, anoxia) on individual species, some better adapted to low oxygen conditions (e.g., Chironomidae) than others (e.g., Monoporeia affinis). The nutrient concentrations in the surface sediment also significantly affected the benthic assemblage patterns. The number of species in space and time increased with increasing oxygen concentrations. This study clearly shows that in order to maintain healthy marine communities, it is essential to counteract excess nutrient inputs and their indirect effects on sufficient O2 conditions for the benthic habitats.
  • Schumacher, Johanna; Bergqvist, Lisa; van Beest, Floris M.; Carstensen, Jacob; Gustafsson, Bo; Hasler, Berit; Fleming, Vivi; Nygård, Henrik; Pakalniete, Kristîne; Sokolov, Alexander; Zandersen, Marianne; Schernewski, Gerald (Frontiers in Marine Science, 2020)
    Frontiers Marine Science 7 (2020)
    Decision support tools (DSTs), like models, GIS-based planning tools and assessment tools, play an important role in incorporating scientific information into decision-making and facilitating policy implementation. In an interdisciplinary Baltic research group, we compiled 43 DSTs developed to support ecosystem-based management of the Baltic Sea and conducted a thorough review. Analyzed DSTs cover a wide variety of policy issues (e.g., eutrophication, biodiversity, human uses) and address environmental as well as socio-economic aspects. In this study, we aim to identify gaps between existing DSTs and end-user needs for DSTs for supporting coastal and marine policy implementation, and to provide recommendations for future DST development. In two online surveys, we assess the awareness and use of DSTs in general, as well as policy implementation challenges and DST needs of representatives of public authorities from all Baltic countries, in particular. Through a policy review we identify major policy issues, policies, and general implementation steps and requirements and develop the synthesis-matrix, which is used to compare DST demand and supply. Our results show that DSTs are predominantly used by researchers. End-users from public authorities use DSTs mostly as background information. Major obstacles for DST use are lacking awareness and experiences. DST demand is strongest for the policy issue eutrophication. Furthermore, DSTs that support the development of plans or programs of measures and assess their impacts and effectiveness are needed. DST supply is low for recently emerging topics, such as non-indigenous species, marine litter, and underwater noise. To overcome existing obstacles, a common database for DSTs available in the BSR is needed. Furthermore, end-users need guidance and training, and cooperation between DST developers and end-users needs to be enhanced to ensure the practical relevance of DSTs for supporting coastal and marine policy implementation. To fill existing gaps, DSTs that address impacts on human welfare and link environmental and socio-economic aspects should be developed. The Baltic Sea Region serves as a best practice case for studying DSTs and their practical use. Hence, our results can provide insights for DST development in other marine regions. Furthermore, our methodological approach is transferable to other areas.
  • Momigliano, Paolo; Jokinen, Henri; Calboli, Federico; Aro, Eero; Merilä, Juha (2019)
    Unobserved diversity, such as undetected genetic structure or the presence of cryptic species, is of concern for the conservation and management of global biodiversity in the face of threatening anthropogenic processes. For instance, unobserved diversity can lead to overestimation of maximum sustainable yields and therefore to overharvesting of the more vulnerable stock components within unrecognized mixed-stock fisheries. We used DNA from archival (otolith) samples to reconstruct the temporal (1976-2011) genetic makeup of two mixed-stock flounder fisheries in the angstrom land Sea (AS) and the Gulf of Finland (GoF). Both fisheries have hitherto been managed as a single stock of European flounders (Platichthys flesus), but were recently revealed to target two closely related species: the pelagic-spawning P. flesus and the newly described, demersal-spawning P. solemdali. While the AS and GoF fisheries were assumed to consist exclusively of P. solemdali, P. flesus dominated the GoF flounder assemblage (87% of total) in 1983, had disappeared (0%) by 1993, and remained in low proportions (10%-11%) thereafter. In the AS, P. solemdali dominated throughout the sampling period (>70%), and P. flesus remained in very low proportions after 1983. The disappearance of P. flesus from the GoF coincides in time with a dramatic (similar to 60%) decline in commercial landings and worsening environmental conditions in P. flesus' northernmost spawning ground, the Eastern Gotland Basin, in the preceding 4-6 years. These results are compatible with the hypothesis that P. flesus in the GoF is a sink population relying on larval subsidies from southern spawning grounds and the cause of their disappearance is a cessation of larval supply. Our results highlight the importance of uncovering unobserved genetic diversity and studying spatiotemporal changes in the relative contribution of different stock components, as well as the underlying environmental causes, to manage marine resources in the age of rapid anthropogenic change.
  • Nygård, Henrik; van Beest, Floris M.; Bergqvist, Lisa; Carstensen, Jacob; Gustafsson, Bo G.; Hasler, Berit; Schumacher, Johanna; Schernewski, Gerald; Sokolov, Alexander; Zandersen, Marianne; Fleming, Vivi (Springer Link, 2020)
    Environmental Management 66(6) (2020)
    Decision-support tools (DSTs) synthesize complex information to assist environmental managers in the decision-making process. Here, we review DSTs applied in the Baltic Sea area, to investigate how well the ecosystem approach is reflected in them, how different environmental problems are covered, and how well the tools meet the needs of the end users. The DSTs were evaluated based on (i) a set of performance criteria, (ii) information on end user preferences, (iii) how end users had been involved in tool development, and (iv) what experiences developers/hosts had on the use of the tools. We found that DSTs frequently addressed management needs related to eutrophication, biodiversity loss, or contaminant pollution. The majority of the DSTs addressed human activities, their pressures, or environmental status changes, but they seldom provided solutions for a complete ecosystem approach. In general, the DSTs were scientifically documented and transparent, but confidence in the outputs was poorly communicated. End user preferences were, apart from the shortcomings in communicating uncertainty, well accounted for in the DSTs. Although end users were commonly consulted during the DST development phase, they were not usually part of the development team. Answers from developers/hosts indicate that DSTs are not applied to their full potential. Deeper involvement of end users in the development phase could potentially increase the value and impact of DSTs. As a way forward, we propose streamlining the outputs of specific DSTs, so that they can be combined to a holistic insight of the consequences of management actions and serve the ecosystem approach in a better manner.
  • Lehtoranta, Jouni; Bendtsen, Jørgen; Lännergren, Christer; Saarijärvi, Erkki; Lindström, Magnus; Pitkänen, Heikki (Elsevier BV, 2022)
    Ecological Engineering
    We studied the effects of pumping surface water down through the pycnocline (i.e. artificial ventilation) on hydrodynamics, oxygen concentrations, hydrogen sulfide, and nutrients in two anoxic coastal basins (Lännerstasundet and Sandöfjärden). In addition, in a corresponding laboratory aquarium experiment, pumping of less saline surface water entrained dense bottom water with a mixing ratio of 6.8 and illustrated dispersal below the pycnocline. Oxygen saturation increased from 0 to 20%; oxygen penetrated poorly into the sediment of the aquarium. In the salinity-stratified Lännerstasundet basin, ventilation also oxidized the anoxic bottom water. The ventilation removed hydrogen sulfide and decreased the sub-pycnocline water pools of phosphorus and ammonium, which was not observed in a neighboring reference basin. The summertime ventilation warmed and made the sub-pycnocline water less saline. In the autumn, the inflows of cooled water from the surroundings with equal or higher salinity promoted its sinking in the relatively warm ventilated basin. The inflows maintained oxygen concentrations between 4 and 8 mg L−1 for months after the ventilation ended. In contrast to Lännerstasundet, ventilation did not prevent formation of anoxia and release of nutrients in the temperature-stratified Sandöfjärden. Here, the ventilation capacity was less than that in Lännerstasundet and ventilation expanded the sub-thermocline bottom area, warmed the bottom sediments, and probably displaced oxic water from the experimental area. The ventilation did not promote density conditions for inflows and no marked inflow-induced oxidation was observed after midsummer. We conclude that a significant amount of anoxic water was entrained into the ascending plume which reduced the oxygen content below the pycnocline ventilation in aquarium experiment. Additionally, summertime ventilation may improve the status of the salinity-stratified basins for further oxidation. The improvement occurs due to autumn cooling and favorable basin topography, which promote inflows of oxic water with larger density and thereby, renewal of bottom water in the pumped basin. The semi-enclosed and temperature-stratified basin cannot form such favorable density conditions for inflows and thus ventilation is less efficient.
  • Söderquist, Pär; Dessborn, Lisa; Djerf, Henric; Elmberg, Johan; Gunnarsson, Gunnar; Holopainen, Sari (2021)
    Common practices in current game management are wetland restoration and creation, as well as releases of quarry species. We studied the impact of releases of mallard ducklings on species richness of wild waterbirds and amphibians on three types of wetlands: natural, constructed and restored. Data on species richness, macrophyte cover and water characteristics (total phosphorous and pH) were collected at 32 sites in an agricultural landscape in southern Sweden. In total, 14 species of waterbirds were recorded, ranging from zero to seven per wetland and survey. Amphibians were present in 24 of the 32 wetlands; in total five species were found, ranging from zero to three per wetland. By using generalized linear modelling we found that wetland type best predicted waterbird species richness. Constructed wetlands had significantly more waterbird species, regardless of whether they were used for mallard releases or not. There were breeding amphibians in 62% of natural, 100% of restored and 77% of constructed wetlands. Breeding amphibians were present in 84% of wetlands without, and in 62% of wetlands with releases. However, included variables did not explain amphibian species richness in the wetlands. Releasing large numbers of mallards on a wetland and providing food ad libitum is likely to affect water quality, nutrient availability and predation pressure. Indeed, phosphorous levels were significantly higher in release wetlands, but no differences were found between wetland types.This means that mallard releases may increase nutrient loads in environments that are already eutrophied. However, in our study system releases did not influence species richness of waterbirds and amphibians locally. Constructing wetlands for mallard releases can thus have positive local effects on species richness.
  • Schaedig, Eric (Helsingin yliopisto, 2020)
    The Baltic Sea is a unique and delicate brackish water ecosystem with high primary productivity driven by oceanic biogeochemical cycles of oxygen, iron, silicon, nitrogen and phosphorus. Elevated anthropogenic nutrient loading into the Baltic ecosystem has resulted in a large-scale increase in destructive cyanobacterial blooms in the open Baltic Sea over the past century. The toxic cyanobacterium Nodularia spumigena is a major component of surface blooms in the open Baltic Sea and continues to bloom even after the depletion of phosphate from the surrounding waters. This phenomenon has been attributed to an ability to scavenge phosphorus from recalcitrant sources. However, the exact phosphorus species that sustain N. spumigena growth in the Baltic Sea remain largely unknown. Here, I employ a comparative genomics approach to determine the evolutionary dynamics of phosphorus scavenging in eight strains of N. spumigena and predict the range of phosphorus sources that may support their growth. Then, I test these predictions by growing six strains of N. spumigena on a number of potentially bioavailable phosphorus sources. Among the phosphorus scavenging genes identified by the genomic analysis, putative pathways for the enzymatic degradation of phytic acid, phosphite, and phosphonates were present and highly conserved in the species. Subsequent growth experiments demonstrated that the organism may grow using phytic acid and phosphite, as well as the phosphonates methylphosphonic acid, ethylphosphonic acid, and nitrilotris(methylenephosphonic acid), as sole phosphorus sources. These results indicate that N. spumigena blooms may be supported by several phosphorus sources previously not known to contribute to eutrophication in the Baltic Sea. While additional growth experiments and further research on the environmental prevalence of these compounds are necessary, the findings presented in this study expand our knowledge of how N. spumigena dominates phytoplankton blooms in a phosphorus-scarce environment and may help to inform future eutrophication mitigation efforts in the Baltic Sea region.
  • Candolin, Ulrika; Bertell, Elina; Kallio, Jarkko (2018)
    1. Alien species are altering ecosystems around the globe. To predict and manage their impacts, the underlying mechanisms need to be understood. This is challenging in ecosystems undergoing multiple disturbances as unexpected interactions can alter the impact of individual disturbances. Such interactions are likely to be common in disturbed ecosystems, but have so far received little attention. 2. We investigated whether interactions between an invading shrimp Palaemon elegans and another human-induced disturbance, the population growth of a native mesopredator, the threespine stickleback, influences a third human-induced disturbance, the increase in biomass of filamentous algae. Increases in both the native mesopredator population and algal biomass have been promoted by eutrophication and a trophic cascade triggered by declining predatory fish stocks. 3. We used mesocosm and field enclosure experiments, combined with analyses of long-term trends in the abundance of the invader and the native mesopredator, to dissect the influence of the two species on algal biomass when alone and when co-occurring. 4. The impact of the invader on algal biomass depended on the native mesopredator; shrimp on their own had no effect on algal growth, but mitigated algae accumulation when competing with the stickleback for resources. Competition caused the shrimp to shift its diet from grazers to algae, and its habitat choice from open to vegetated habitats. The native mesopredator, in contrast, increased algal biomass irrespective of the presence of the invader, by preying on grazers and inducing a trophic cascade. 5. Our results show that the presence of a native mesopredator causes an invader to alter its behaviour and thereby its ecological impact. This demonstrates that interactions between invaders and other anthropogenic disturbances can alter the ecological impact of invaders, and, notably, that the impact of invaders can be positive and stabilize disturbed ecosystems. These results stress the importance of considering interactions among disturbances when investigating the ecological impact of alien species.
  • Poikane, Sandra; Kelly, Martyn G.; Várbíró, Gábor; Borics, Gábor; Erős, Tibor; Hellsten, Seppo; Kolada, Agnieszka; Lukács, Balázs András; Lyche Solheim, Anne; Pahissa López, José; Willby, Nigel J.; Wolfram, Georg; Phillips, Geoff (Elsevier BV, 2022)
    Science of The Total Environment
    Nutrient targets based on pressure-response models are essential for defining ambitions and managing eutrophication. However, the scale of biogeographical variation in these pressure-response relationships is poorly understood, which may hinder eutrophication management in regions where lake ecology is less intensively studied. In this study, we derive ecology-based nutrient targets for five major ecoregions of Europe: Northern, Central-Baltic, Alpine, Mediterranean and Eastern Continental. As a first step, we developed regressions between nutrient concentrations and ecological quality ratios (EQR) based on phytoplankton and macrophyte communities. Significant relationships were established for 13 major lake types; in most cases, these relationships were stronger for phosphorus than for nitrogen, and stronger for phytoplankton than for macrophytes. Using these regressions, we estimated the total phosphorus (TP) and total nitrogen (TN) concentrations at which lakes of different types are likely to achieve good ecological status. However, in the very shallow lakes of the Eastern Continental region, relations between nutrient and biological communities were weak or non-significant. This can be attributed to high nutrient concentrations (in the asymptotic zone of phosphorus-phytoplankton models) suggesting other factors (light, grazing) limit primary production. However, we also show that fish stocking is a major pressure on Eastern Continental lakes, negatively affecting ecological status: lakes with low fish stocking show low chlorophyll-a concentrations and good ecological status despite high nutrient levels, while the lakes with high fish stocking show high chlorophyll-a and low ecological status. This study highlights the need to better understand lakes in biogeographic regions that have been, for historical reasons, less studied. This, in turn, helps reveal factors that challenge the dominant paradigms of lake assessment and management.
  • Wang, Huan; García Molinos, Jorge; Heino, Jani; Zhang, Huan; Zhang, Peiyu; Xu, Jun (Pergamon, 2021)
    Environment International 153 (2021), 106494
    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.
  • Belinskij, Antti; Iho, Antti; Paloniitty née Korvela, Tiina; Soininen, Niko (2019)
    Animal agriculture is shifting toward larger farms and regional agglomerations in many countries. In step with this development, manure nutrients have started accumulating regionally, and are leading to increasing eutrophication problems. Nevertheless, the same trend may also prompt innovations in manure treatment. For example, Valio Ltd (the largest dairy processer in Finland) is planning a network of facilities that would remove water from manure, fraction the nutrients in it, and produce biogas from the excess methane. One of the main hurdles in developing this technology is that the current regulatory framework does not support a shift from diffuse loading, which is seen in the traditional application of manure on fields, to point-source loading; the regulations may even prevent such a change. This article analyzes a governance framework that addresses this dilemma in EU–Finland, and discusses how the governance described could curtail the nutrient loading of agriculture to waters. The approach is based on adaptive governance theory. We argue that traditional top–down regulation, which emphasizes food security, contains serious shortcomings when it comes to managing agricultural nutrient loading to waters, and that the current regulatory framework does not necessarily have the adaptive capacity to facilitate new, bottom–up solutions for manure treatment. Interestingly, the strict water quality requirements of the EU Water Framework Directive (2000/60/EC) open new windows of opportunity for such solutions, and thus for improving the overall sustainability of animal agriculture.
  • Andersson, Anna; Brady, Mark V.; Pohjola, Johanna (Royal Swedish Academy of Sciences, 2022)
    Ambio
    This paper systematically reviews the literature on how to reduce nutrient emissions to the Baltic Sea cost-effectively and considerations for allocating these costs fairly among countries. The literature shows conclusively that the reduction targets of the Baltic Sea Action Plan (BSAP) could be achieved at considerably lower cost, if countries would cooperate to implement the least costly abatement plan. Focusing on phosphorus abatement could be prudent as the often recommended measures—wastewater treatment and wetlands—abate nitrogen too. An implication of our review is that the potential for restoring the Baltic Sea to good health is undermined by an abatement strategy that is more costly than necessary and likely to be perceived as unfair by several countries. Neither the BSAP nor the cost-effective solution meet the surveyed criteria for fairness, implying a need for side-payments.
  • Salminen, Sarianna; Tammelin, Mira; Jilbert, Tom; Fukumoto, Yu; Saarni, Saija (Kluwer Academic, 2021)
    Journal of Paleolimnology 2021
    The influence of lake restoration efforts on lake bottom-water conditions and varve preservation is not well known. We studied varved sediments deposited during the last 80 years along a water-depth transect in the Enonsaari Deep, a deep-water area of the southernmost Enonselkä Basin, Lake Vesijärvi, southern Finland. For the last few decades, the Enonselkä Basin has been subject to ongoing restoration efforts. Varve, elemental, and diatom analyses were undertaken to explore how these actions and other human activities affected varve preservation in the Enonsaari Deep. In contrast to most varved Finnish lakes, whose water columns have a natural tendency to stratify, and possess varve records that span thousands of years, varve formation and preservation in Lake Vesijärvi was triggered by relatively recent anthropogenic stressors. The multi-core varve analysis revealed that sediment in the Enonsaari Deep was initially non-varved, but became fully varved in the late 1930s, a time of increasing anthropogenic influence on the lake. The largest spatial extent of varves occurred in the 1970s, which was followed by a period of less distinguishable varves, which coincided with diversion of sewage from the lake. Varve preservation weakened during subsequent decades and was terminated completely by lake aeration in the 2010s. Despite improvements in water quality, hypolimnetic oxygen depletion and varve preservation persisted beyond the reduction in sewage loading, initial aeration, and biomanipulation. These restoration efforts, however, along with other human actions such as harbor construction and dredging, did influence varve characteristics. Varves were also influenced by diatom responses to anthropogenic forcing, because diatoms form a substantial part of the varve structure. Of all the restoration efforts, a second episode of aeration seems to have had the single most dramatic impact on profundal conditions in the basin, resulting in replacement of a sediment accumulation zone by a transport or erosional zone in the Enonsaari Deep. We conclude that human activities in a lake and its catchment can alter lake hypolimnetic conditions, leading to shifts in lake bottom dynamics and changes in varve preservation.
  • Rankinen, Katri; Enrique, José; Bernal, Cano; Holmberg, Maria; Vuorio, Kristiina; Granlund, Kirsti (Elsevier, 2019)
    Science of The Total Environment 658 (2019), 1278-1292
    In Finland, a recent ecological classification of surface waters showed that the rivers and coastal waters need attention to improve their ecological state. We combined eco-hydrological and empirical models to study chlorophyll-a concentration as an indicator of eutrophication in a small agricultural river. We used a modified story-and-simulation method to build three storylines for possible changes in future land use due to climate change and political change. The main objective in the first storyline is to stimulate economic activity but also to promote the sustainable and efficient use of resources. The second storyline is based on the high awareness but poor regulation of environmental protection, and the third is to survive as individual countries instead of being part of a unified Europe. We assumed trade of agricultural products to increase to countries outside Europe. We found that chlorophyll-a concentration in the river depended on total phosphorus concentration. In addition, there was a positive synergistic interaction between total phosphorus and water temperature. In future storylines, chlorophyll-a concentration increased due to land use and climate change. Climate change mainly had an indirect influence via increasing nutrient losses from intensified agriculture. We found that well-designed agri-environmental measures had the potential to decrease nutrient loading from fields, as long as the predicted increase in temperature remained under 2 °C. However, we were not able to achieve the nutrient reduction stated in current water protection targets. In addition, the ecological status of the river deteriorated. The influence of temperature on chlorophyll-a growth indicates that novel measures for shading rivers to decrease water temperature may be needed in the future.
  • Taipale, Sami J.; Kuoppamäki, Kirsi; Strandberg, Ursula; Peltomaa, Elina; Vuorio, Kristiina (SpringerLink, 2020)
    Hydrobiologia 847 21 (2020)
    Food quality is one of the key factors influencing zooplankton population dynamics. Eutrophication drives phytoplankton communities toward the dominance of cyanobacteria, which means a decrease in the availability of sterols and long-chain polyunsaturated fatty acids (EPA and DHA). The effects of different restoration measures on the nutritional quality of the phytoplankton community and subsequent impacts on zooplankton biomass have rarely been considered. We analyzed the nutritional quality of phytoplankton in the eutrophic Lake Vesijärvi in southern Finland over a 37-year period, and studied the impacts of two restoration measures, biomanipulation and hypolimnetic aeration, on the abundance of high-quality phytoplankton. We found that biomanipulation had a positive impact on the abundance of taxa synthesizing sterols, EPA, and DHA and, concurrently, on the biomass of the keystone species Daphnia. In contrast, hypolimnetic aeration did not result in such a beneficial outcome, manifested as a decrease in the abundance of Daphnia and frequent phytoplankton blooms dominated by cyanobacteria suggesting reduction in the nutritional quality of food for Daphnia. Our analysis shows that the determination of the nutritional value of algae and the contribution of essential fatty acids and sterols is an effective method to evaluate the success of various restoration measures.
  • Kortelainen, Pirkko; Larmola, Tuula; Rantakari, Miitta; Juutinen, Sari; Alm, Jukka; Martikainen, Pertti J. (2020)
    Abstract Estimates of regional and global freshwater N2O emissions have remained inaccurate due to scarce data and complexity of the multiple processes driving N2O fluxes the focus predominantly being on summer time measurements from emission hot spots, agricultural streams. Here we present four-season data of N2O concentrations in the water columns of randomly selected boreal lakes covering a large variation in latitude, lake type, area, depth, water chemistry and land use cover. Nitrate was the key driver for N2O dynamics, explaining as much as 78% of the variation of the seasonal mean N2O concentrations across all lakes. Nitrate concentrations varied among seasons being highest in winter and lowest in summer. Of the surface water samples 71% were oversaturated with N2O relative to the atmosphere. Largest oversaturation was measured in winter and lowest in summer stressing the importance to include full year N2O measurements in annual emission estimates. Including winter data resulted in four-fold annual N2O emission estimates compared to summer only measurements. Nutrient rich calcareous and large humic lakes had the highest annual N2O emissions. Our emission estimates for Finnish and boreal lakes are 0.6 Gg and 29 Gg N2O-N y-1, respectively. The Global Warming Potential (GWP) of N2O cannot be neglected in the boreal landscape, being 35% of that of diffusive CH4 emission in Finnish lakes.
  • Wade, Andrew J.; Skeffington, Richard A.; Couture, Raoul-Marie; Erlandsson Lampa, Martin; Groot, Simon; Halliday, Sarah J.; Harezlak, Valesca; Hejzlar, Josef; Jackson-Blake, Leah A.; Lepistö, Ahti; Papastergiadou, Eva; Riera, Joan Lluís; Rankinen, Katri; Shahgedanova, Maria; Trolle, Dennis; Whitehead, Paul G.; Psaltopoulos, Demetris; Skuras, Dimitris (MDPI AG, 2022)
    Water
    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.