Artiklid

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/6178

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Nüüd näidatakse 1 - 20 142

Abrupt rise in the contribution of CH₄-derived carbon to benthic secondary production of a shallow hemiboreal/boreal lake
(Wiley, 2018) Belle, Simon; Tõnno, Ilmar; Stivrins, Normunds; Freiberg, Rene; Veski, Siim; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
Understanding long-term carbon flows through aquatic food webs is essential to assess impact of climatic and environmental changes on lake ecosystems. We reconstructed temporal changes in carbon sources fuelling chironomid biomass in a small and shallow hemiboreal/boreal lake over the last 11 000 years. Results were compared with temporal dynamics of known potential controlling factors: summer air temperature, human activities, phytoplankton assemblages and organic matter composition. We report an abrupt rise in the contribution of methane-derived carbon to chironomid biomass. However, this sudden increase was not the consequence of drastic changes in the composition of sedimentary organic matter, mean air temperature, lake trophic state or human activities in the catchment area. Our results suggest that shallowing of the lake caused by sedimentary infilling processes was a possible driver of the expansion of anoxic zones, enhancing CH 4 cycling in lake sediments. However, complementary studies are needed to better understand the mechanisms by which lake shallowing could affect carbon flows to aquatic consumers, and then better assess the natural dynamics of past carbon processing in the benthic food web of shallow lakes.
Atmospheric stilling offsets the benefits from reduced nutrient loading in a large shallow lake
(Wiley, 2020) Janatian, Nasime; Olli, Kalle; Cremona, Fabien; Laas, Alo; Nõges, Peeter; Chair of Hydrobiology and Fishery, Institute of Agricultural and Environmental Sciences
As part of a global phenomenon, a 30% decrease in average wind speed since 1996 in southern Estonia together with more frequent easterly winds resulted in 47% decrease in bottom shear stress in the large (270 km 2 ), shallow (mean depth 2.8 m), and eutrophic Lake Võrtsjärv. Following a peak in eutrophication pres- sure in the 1970s–80s, the concentrations of total nutrients were declining. Nonmetric Multidimensional Scal- ing (NMDS) ordination of a 54-year phytoplankton community composition time-series (1964–2017) revealed three distinct periods with breaking points coinciding with changes in wind and/or water level. Contrary to expectations, we detected no decrease in optically active substances that could be related to wind stilling, whereas phytoplankton biomass showed an increasing trend despite reduced nutrient levels. Here we show how opening of the “light niche,” caused by declining amount of suspended sediments, was capitalized and filled by the light-limited phytoplankton community. We suggest that wind stilling is another global factor, complemen- tary to climate warming that counteracts eutrophication mitigation in lakes and may provide a challenge to assessment of the lake ecological status.
Atmospheric stilling offsets the benefits from reduced nutrient loading in a large shallow lake
(Wiley, 2019) Janatian, Nasime; Olli, Kalle; Cremona, Fabien; Laas, Alo; Nõges, Peeter; Estonian University of Life Sciences. Institute of Agricultural and Environmental Sciences. Chair of Hydrobiology and Fishery
As part of a global phenomenon, a 30% decrease in average wind speed since 1996 in southern Estonia together with more frequent easterly winds resulted in 47% decrease in bottom shear stress in the large (270 km2), shallow (mean depth 2.8 m), and eutrophic Lake Võrtsjärv. Following a peak in eutrophication pressure in the 1970s–80s, the concentrations of total nutrients were declining. Nonmetric Multidimensional Scaling (NMDS) ordination of a 54-year phytoplankton community composition time-series (1964–2017) revealed three distinct periods with breaking points coinciding with changes in wind and/or water level. Contrary to expectations, we detected no decrease in optically active substances that could be related to wind stilling, whereas phytoplankton biomass showed an increasing trend despite reduced nutrient levels. Here we show how opening of the “light niche,” caused by declining amount of suspended sediments, was capitalized and filled by the light-limited phytoplankton community. We suggest that wind stilling is another global factor, complementary to climate warming that counteracts eutrophication mitigation in lakes and may provide a challenge to assessment of the lake ecological status.
Bataadi kasvatustehnoloogia Põhjamaade tingimustesse
(Eesti Maaülikool; Maaelu Teadmuskeskus, 2026) Lääniste, Peeter; Rouhiainen, Markus; Eremeev, Viacheslav; Niinemets, Ülo; Runno-Paurson, Eve; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Taimebioloogia ja maaviljeluse õppetool
The field experiment was conducted in 2022 at the Eerika Experimental Field of the Estonian University of Life Sciences. Three sweet potato (Ipomoea batatas L.) cultivars bred in the USA—’Beauregard’, ‘Covington’, and ‘Evangeline’—were included in the study. The cultivars were grown under two cultivation systems: black plastic mulch and conventional furrow cultivation. The results demonstrated that all evaluated cultivars are suitable for cultivation under Estonian agroclimatic conditions. Sweet potato grown under black plastic mulch produced significantly higher yield than that grown in furrows. The mean yield obtained with black plastic mulch was 55.7 t ha⁻¹, whereas the mean yield under furrow cultivation was 16.4 t ha⁻¹. No statistically significant differences in yield were detected among the cultivars. In conclusion, the findings indicate that sweet potato cultivation is highly promising in Estonia. However, further studies are required to validate these results, refine optimal cultivation techniques and evaluate additional cultivars potentially suitable for Nordic climate conditions.
Bataadi säilitushaigus fusarioos
(Eesti Maaülikool; Maaelu Teadmuskeskus, 2026) Runno-Paurson, Eve; Vester, Laura; Lääniste, Peeter; Niinemets, Ülo; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Taimebioloogia ja maaviljeluse õppetool
The cultivation of sweet potato (Ipomoea batatas L.) under Estonian field conditions has been studied at the Estonian University of Life Sciences since 2018. A cultivation technology suitable for Nordic conditions has been developed under plastic mulch, and experience has been gained with various cultivation technologies, cultivars, and fertilization regimes. As sweet potato cultivation area expands in Estonia, postharvest handling, storage management, and yield losses during storage are expected to pose increasing challenges. This study evaluated the susceptibility of sweet potato grown in Estonia to major storage diseases, identified the most damaging pathogens, and assessed the effects of cultivar and fertilisation regime on disease incidence. A total of seven orange-fleshed, red-skinned cultivars were selected for the field trial in 2024: three bred in the USA (‘Beauregard’, ‘Covington’ and ‘Evangeline’) and four in Europe (‘Erato Early Orange’, ‘Erato Orange’, ‘Erato Compact Orange’ and ‘Erato Deep Orange’; Lubera, Volmary Ltd., Erato group). Two fertilization regimes were applied: unfertilized control and fertilized (50 kg N ha-1) treatment. The study revealed that the storability of sweet potato grown in Estonia was generally good. However, occasional infections of storage roots by Fusarium root rot were observed, with disease severity depending on cultivar and fertilisation regime. During 2024 growing season, no Fusarium root rot damage was detected at the harvest. Disease spots appeared later during storage (approximately 1.5 months after harvest) on the storage roots of cultivar ‘Erato Compact Orange’. Nearly five months after harvest, the cultivars with the least damaged storage roots were ‘Beauregard’, ‘Erato Deep Orange’, ‘Covington’ and ‘Evangeline’. Based on this field experiment, all tested cultivars can be recommended for field cultivation under Nordic climate conditions. However, the storage roots of ‘Erato Compact Orange’ might be more susceptible to Fusarium root rot during storage than those of the other cultivars tested.
Benthic Bacterial Community Composition in the Oligohaline-Marine Transition of Surface Sediments in the Baltic Sea Based on rRNA Analysis
(Frontiers, 2018) Klier, Julia; Dellwig, Olaf; Leipe, Thomas; Jürgens, Klaus; Herlemann, Daniel P. R.; Centre for Limnology. Estonian University of Life Sciences
Salinity has a strong impact on bacterial community composition such that freshwater bacterial communities are very different from those in seawater. By contrast, little is known about the composition and diversity of the bacterial community in the sediments (bacteriobenthos) at the freshwater-seawater transition (mesohaline conditions). In this study, partial 16S-rRNA sequences were used to investigate the bacterial community at five stations, representing almost freshwater (oligohaline) to marine conditions, in the Baltic Sea. Samples were obtained from the silty, top-layer (0–2.5 cm) sediments with mostly oxygenated conditions. The long water residence time characteristic of the Baltic Sea, was predicted to enable the development of autochthonous bacteriobenthos at mesohaline conditions. Our results showed that, similar to the water column, salinity is a major factor in structuring the bacteriobenthos and that there is no loss of bacterial richness at intermediate salinities. The bacterial communities of marine, mesohaline, and oligohaline sediments differed in terms of the relative rRNA abundances of the major bacterial phyla/classes. At mesohaline conditions typical marine and oligohaline operational taxonomic units (OTUs) were abundant. Putative unique OTUs in mesohaline sediments were present only at low abundances, suggesting that the mesohaline environment consists mainly of marine and oligohaline bacteria with a broad salinity tolerance. Our study provides a first overview of the diversity patterns and composition of bacteria in the sediments along the Baltic Sea salinity gradient as well as new insights into the bacteriobenthos at mesohaline conditions.
Biodiversity and functional trait effects on copper toxicity in a proof-of-concept multispecies microalgal assay
(Elsevier, 2021) Joonas, Elise; Olli, Kalle; Kahru, Anne; Aruoja, Villem
This study aimed to elucidate biodiversity effects on algal biomass production under toxicant stress and to increase environmental realism in ecotoxicological testing by exposing artificial algal communities to Cu2+. All 15 possible combinations of four functionally distinct microalgal species (green algae Chlamydomonas reinhardtii and Raphidocelis subcapitata, diatom Fistulifera pelliculosa and cyanobacterium Synechocystis sp.) were exposed to 0.01 and 0.02 mg Cu2+ l􀀀 1 in a modified algal growth inhibition assay (OECD 201). Compared to monocultures, the replicability of assays in multispecies communities decreased. Copper-induced inhibition of the biomass yield of individual species did not change due to interactions between species in multispecies tests, indicating that Cu toxicity was the driver of competitive outcomes. Biomass yield was increased at higher species richness in controls and Cu-exposed treatments. Selection effect is considered to prevail over trait complementarity in our experiments, because functional diversity, that expresses species trait variability and equality in species’ occurrence, had a negative effect on algal biomass yield, while species richness increased the yield. Algal functional traits related to cell size were the best predictors of microalgal biomass production. Species identity was identified as an important determinant of community-level outcomes.
Boosting the monitoring of phytoplankton in optically complex coastal waters by combining pigment-based chemotaxonomy and in situ radiometry
(Elsevier, 2019) Tamm, Marju; Ligi, Martin; Panksep, Kristel; Teeveer, Karolin; Freiberg, Rene; Laas, Peeter; Paavel, Birgot; Kutser, Tiit; Reinart, Anu; Tõnno, Ilmar; Nõges, Tiina; Chair of Hydrobiology and Fishery. Institute of Agricultural and Environmental Sciences
Research about the occurrence and extent of the cyanobacterial blooms in the Baltic Sea is critical due to their increased magnitude and frequency. Monitoring of the blooms is complicated due to their spatially and tem- porally heterogeneous nature. For adequate assessment of the water quality, phytoplankton dynamics needs to be tracked in large areas with high monitoring frequency. The main objectives of this study were (1) to describe phytoplankton community composition by pigment-based chemotaxonomy and validate the results with mi- croscopy; (2) to improve the retrieval of information about phytoplankton community by combining remote sensing with laboratory based approaches (3) to develop a region-specific algorithm to calculate cyanobacteria biomass from reflectance spectra; (4) to detect and quantify potentially toxic bloom-forming cyanobacteria with molecular methods. In our study the reflectance-based chlorophyll a (Chl a) values overestimated the High- performance Liquid Chromatography (HPLC) values although the correlations with HPLC Chl a measurements were very strong (rp ∼ 0.8, p < 0.001). We found that 709 nm/620 nm reflectance ratio correlated strongly (rp = 0.75, p < 0.01) to cyanobacteria wet biomass in CDOM-rich Väinameri even at low cyanobacterial bio- mass levels. Correlations between pigment-based chemotaxonomy and microscopy were significant in case of cyanobacteria (rp = 0.73, p < 0.01), cryptophytes (rp = 0.71, p < 0.05) and dinoflagellates (rp = 0.64, p < 0.05).
Both climate trends and short-term fluctuations affected algae–zooplankton interactions in a boreal lake during the late Holocene
(Wiley, 2021) Belle, Simon; Tõnno, Ilmar; Vrede, Tobias; Freiberg, Rene; Nilsson, Jenny L.; Goedkoop, Willem
1. Most studies aiming to explore the response of algae and zooplankton trophic interactions to climate variability have only been focused on unidirectional and very shortterm trends in temperature changes. As a result, the non-stationary aspect of climate change (warming and cooling periods, frequencies) remains completely unstudied. 2. We studied elemental and stable isotope composition of sedimentary organic matter, photosynthetic pigments, and carbon stable isotope composition of Cladocera resting eggs in a sediment record covering the last c. 2,600 years. We examined how past climate change acting at different timescales affected algal biomass and community composition, and carbon assimilation by zooplankton in a boreal lake. 3. Our study revealed major effects of both long-term climate trends and shorter term fluctuations on algae–zooplankton interactions in a boreal lake. We found the main climate trends, in particular the Little Ice Age, induced algal biomass and community composition changes and drastic changes in carbon assimilation by zooplankton. Interestingly, we found that temperature fluctuations could also contribute to regulating algae–zooplankton interactions. Specifically, we observed drastic changes in sedimentary markers and stable isotope composition of zooplankton remains during the most recent period, suggesting a strong influence of ongoing anthropogenic change on algae–zooplankton interactions. 4. Our study confirms previous findings showing close long-term linkage between the temporal dynamics of zooplankton diet and planktonic algae, and that both climate trends and short-term fluctuations are key in regulating consumer– resource trophic interactions. 5. Novel approaches that combine high temporal resolution paleolimnological reconstructions and contemporary monitoring studies are needed to better understand climate change effects on algae–zooplankton interactions and lake food webs.
Catchment properties and the photosynthetic trait composition of freshwater plant communities
(American Association for the Advancement of Science, 2019) Iversen, L. L.; Winkel, A.; Baastrup-Spohr, L.; Hinke, A. B.; Alahuhta, J.; Baattrup-Pedersen, A.; Birk, S.; Brodersen, P.; Chambers, P. A.; Ecke, F.; Feldmann, T.; Gebler, D.; Heino, J.; Jespersen, T. S.; Moe, S. J.; Riis, T.; Sass, L.; Vestergaard, O.; Maberly, S. C.; Sand-Jensen, K.; Pedersen, O.
Freshwater plants can be broadly divided into two major categories according to their photosynthetic traits: Some use carbon dioxide as their carbon source, whereas others use bicarbonate. Iversen et al. found that the relative concentrations of these two inorganic carbon forms in water determine the functional composition of plant communities across freshwater ecosystems (see the Perspective by Marcé and Obrador). They created global maps revealing that community composition is structured by catchment geology and not climate (in contrast to the terrestrial realm, where the trait composition is structured by temperature and rainfall). Anthropogenic influences from land-use change are causing large-scale increases in bicarbonate concentrations in freshwater catchments and are thus leading to wholesale changes in the composition of their aquatic plant communities.
Changes in particulate organic matter passing through a large shallow lowland lake
(Estonian Academy Publishers, 2018) Piirsoo, Kai; Laas, Alo; Meinson, Pille; Nõges, Peeter; Pall, Peeter; Viik, Malle; Vilbaste, Sirje; Nõges, Tiina; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Different sources of particulate organic matter (POM) as well as its composition affect the biological food web and hence the self-purification potential and water quality of rivers. We studied the effect of a large shallow lake on the POM pool of the water passing through it. Over four years, we analysed monthly the amount and composition of POM and a set of environmental variables in the inflows and in the outflow of Lake Võrtsjärv (Estonia). In the inflows, the live pool of POM consisted of phytoplankton – small crypto-, dino-, and chlorophytes. The concentration of chlorophyll a (Chl a), as a proxy of phytoplankton biomass, was positively correlated with temperature and total phosphorus and negatively with dissolved silica, total nitrogen, and discharge. In the outflow, the share of the live component of POM was much larger than in the inflows but was also dominated by phytoplankton represented by grazing resistant filamentous cyanobacteria. Chl a was positively correlated with total phosphorus, temperature, pH, and precipitation, and negatively with dissolved silica, total nitrogen, and discharge in the outflow. The different amounts, composition, and seasonal dynamics of POM in the inflows and in the outflow have potentially substantial impacts on the food web with a predominating classical pathway in the inflows versus a detrital pathway in the outflow.
Changing Plankton Communities: Causes, Effects and Consequences
(Frontiers, 2019) Spilling, Kristian; Tedesco, Letizia; Klais, Riina; Olli, Kalle
Marine ecosystems are changing in response to multiple stressors such as global warming, increasing carbon dioxide (CO2) and decreasing oxygen (O2) concentrations and eutrophication of coastal waters, among others. The direct effects of these changes on plankton physiology have been studied for decades; less are known about possible effects these changes might have on the composition of plankton communities, and even less about what effects any such shift in plankton community composition will have on marine ecosystems. The plankton community makes up the base of the marine food web (i.e., primary producers, decomposers, and primary consumers) and plays a pivotal role in global biogeochemical cycles (e.g., Falkowski and Raven, 2013). Any change of the plankton community structure, driven by natural or human induced changes, may consequently have indirect effects on marine ecosystem functioning. This Research Topic focused on causes, effects and consequences of changing composition of plankton communities. The 12 contributions to this volume include seven original research papers, one method paper, and four reviews; all touching the state-of-the-art in current plankton research, and each from a complementary angle. Several of the original research papers deal with changing phytoplankton communities, environmental drivers and ecosystem effects. Fernández-Méndez et al. analyzed sea-ice ridges and the snow-ice interface, which are algal hotspots in the Arctic Ocean. Both sea-ice ridges and the snow-ice interface are projected to increase due to thinning of the ice, and Fernández-Méndez et al. described the algal communities, mostly dominated by different diatoms, in these habitats in the Arctic. von Scheibner et al. examined the phytoplankton and bacterioplankton response to short-term warming. Warming increased carbon availability for the bacterial community, but the ratio between bacterial and primary production was still relatively low, suggesting it is not much changed by short-term warming events. Cohen et al. described diatom transcriptional and physiological responses to changes in iron availability in the open Northeast Pacific Ocean and in the California upwelling system. They found species specific differences in gene expression to changes in nutrient availability and taxa specific strategies for coping with Fe stress. Ajani et al. investigated the realized niches of phytoplankton using a long-term data set collected off Eastern Australia. They demonstrated that the ecological niches can be dynamic and that climate change models cannot use fixed niches when forecasting the phytoplankton community composition. There are three original research papers on zooplankton dynamics. Lips and Lips investigated the increasing importance of the mixotrophic ciliate Mesodinium rubrum in the Baltic Sea. The abundance of this species was higher in years of earlier warming and the authors suggest that it plays an important role in shaping the inorganic nutrient pools at the start of the summer (Lips and Lips). Haraguchi et al. studied the coupling between phytoplankton and ciliates in Danish waters over 2 years, and demonstrated a close coupling between these communities, suggesting top down control of the phytoplankton community by the ciliates. Karlsson and Winder examined ecosystem effects of two locally adapted populations of the filter feeding copepod Eurytemora affinis that differed in size. They demonstrated that morphologically divergent populations of the same species can perform different ecosystem functions through differences in quantitative and qualitative feeding, and by having different population response to changes in resource supply and the phytoplankton community composition. In the method paper by Engel et al., they tested three different ways to manipulate species loss in natural phytoplankton communities. Dilution, filtration, and heat stress was used to remove rare, large and sensitive species, respectively, and this can be used as a method for non-random species manipulation in experiments. The majority of research on species loss has used the approach of random species removal, which may not be a suitable approach for studies of fragile species. The method development and standardization of approaches suggested by Engel et al. are essential for more realistic species loss modeling. The review papers covered different aspects of plankton dynamics and trait-based approaches. Lindh and Pinhassi presented a comprehensive review of bacterioplankton communities in the Baltic Sea and environmental drivers for community changes based on field and experimental studies. Bartoli et al. reviewed the drivers of cyanobacterial blooms in the Curonian Lagoon (Baltic Sea), where cyanobacteria has benefitted from long term increase in the temperature and reduction in the inorganic N:P ratio. A comparison of the differences between freshwater and marine studies of phytoplankton traits and community assembly is presented by Weithoff and Beisner. Finally, Spilling et al. reviewed and synthesize state-of-the-art knowledge on the observed, long-term increase in dinoflagellate abundance in the Baltic Sea during spring bloom and the consequences the shift from diatom to dinoflagellate dominance has for biogeochemical cycles. The topics of the papers published in this Research Topic ranged from heterotrophic bacteria, phytoplankton to zooplankton and covered different marine ecosystems. The potential shift in community composition may have dramatic effects on ecosystem functioning, for example on trophic transfer, and on biogeochemical fluxes through changes in export of organic material, i.e., the biological pump. One of the key challenges for predicting changes to the plankton community is to understand the various functional groups and their niche separation in combination with individual taxa’s ability to acclimate, adapt and compete in a changing environment. This trait-based community ecology of plankton has started to gain traction (Litchman and Klausmeier, 2008; Litchman et al., 2013), and is a useful framework to investigate potential effects of environmental change on plankton community structure. In order to disentangle the potential consequences of shifts in plankton communities, more empirical studies of ecological interactions and export are needed. Hence, we consider the research papers in this Research Topic will be a valuable addition to the accumulating empirical evidence of how plankton communities are modulated by natural and human induced changes and the indirect effect this has on marine ecosystems.
Chironomid incorporation of methane‐derived carbon in plankton‐ and macrophyte‐dominated habitats in a large shallow lake
(Wiley, 2018) Agasild, Helen; Kisand, Anu; Ainelo, Epp; Feldmann, Tõnu; Timm, Henn; Karus, Katrit; Kisand, Veljo; Jones, Roger I.; Nõges, Tiina; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
1. While 13 C-depleted carbon derived from biogenic methane can substantially contribute to the benthic secondary production in deep stratified lakes, its role in shallow lakes is less clear. We investigated the dynamics of δ13 C and δ15 N in the larvae of Chironomus plumosus throughout an annual cycle in two ecologically distinct basins (open-water plankton-dominated and sheltered macrophyte- covered) of a large (270 km2 ), shallow, polymictic and eutrophic lake (Võrtsjärv, Estonia, North Europe). The larval stable isotopic compositions were linked to the presence of methane-oxidising bacteria (MOB) in larval guts and sediments. 2. Molecular detection of MOB revealed their presence in various sediment types, but stable isotope (SI) analysis revealed clear differences in the feeding of chironomid larvae between the plankton- and macrophyte-dominated habitats. 3. In the plankton-dominated habitat, the mean δ13 C values of larvae remained relatively constant (−38.3‰ to −35.5‰) and corresponded closely to the sediment δ13 C values. Mean δ13 C values of chironomid larvae were generally lower in macrophyte-dominated habitats (−43.4‰ to −33.0‰), and both seasonal and individual variation in larval δ13 C values were more pronounced. MOB presence in larval guts proved a dietary contribution from biogenic methane in macrophyte-dominated habitats. Both the SI and molecular results indicated that MOB could help support larvae even during the cold temperature-limited and ice- covered periods. 4. Our study indicates that methane-derived carbon makes a low but steady contri- bution to the larval chironomids throughout an annual cycle in large shallow Võrtsjärv. However, this contribution can be substantially higher in the lake habitats with abundant macrophytes. The study provides further evidence that a carbon flow pathway from biogenic methane can contribute to the benthic food web under variable habitat conditions in a shallow polymictic lake.
Climate-induced changes in carbon flows across the plant-consumer interface in a small subarctic lake
(Nature, 2019) Belle, Simon; Nilsson, Jenny L.; Tõnno, Ilmar; Freiberg, Rene; Vrede, Tobias; Goedkoop, Willem; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Reconstructions of past food web dynamics are necessary for better understanding long-term impacts of climate change on subarctic lakes. We studied elemental and stable isotopic composition of sedimentary organic matter, photosynthetic pigments and carbon stable isotopic composition of Daphnia (cladocera; crustacea) resting eggs (δ13cclado) in a sediment record from a small subarctic lake. We examined how regional climate and landscape changes over the last 5800 years affected the relative importance of allochthonous and autochthonous carbon transfer to zooplankton. Overall, δ13cclado values were well in line with the range of theoretical values of aquatic primary producers, confirming that zooplankton consumers in subarctic lakes, even in the long-term perspective, are mainly fuelled by autochthonous primary production. Results also revealed greater incorporations of benthic algae into zooplankton biomass in periods that had a warmer and drier climate and clearer water, whereas a colder and wetter climate and lower water transparency induced higher contributions of planktonic algae to Daphnia biomass. This study thus emphasizes long-term influence of terrestrial-aquatic linkages and in- lake processes on the functioning of subarctic lake food webs.
Conservation restocking of the imperilled European eel does not necessarily equal conservation
(Oxford University Press, 2021) Rohtla, Mehis; Silm, Maidu; Tulonen, Jouni; Paiste, Päärn; Wickström, Hakan; Kielman-Schmitt, Melanie; Kooijman, Ellen; Vaino, Väino; Eschbaum, Redik; Saks, Lauri; Verliin, Aare; Vetemaa, Markus; Institute of Agricultural and Environmental Sciences, Centre for Limnology
To stop the decline of the European eel population, one of the measures taken is translocating eels for restocking, despite its conservational value being largely unknown. We aimed to contribute to this knowledge gap by (i) investigating the origin of eels caught in coastal waters of Estonia and Finland using otolith microchemistry and (ii) directly estimating restocked eel escapement from Narva River Basin District (NRBD), which is part of the primary Eel Management Unit in Estonia. In Estonia, 74% of the sampled eels (n ¼ 140) were natural recruits and 26% were restocked. In Finland, 27% of the sampled eels (n ¼ 235) were natural recruits and 73% were restocked. Only 1% of all the coastally collected eels were originally restocked to NRBD. These new data together with the reported commercial landings from the escapement route conflict with the current silver eel escapement estimation for NRBD and question the accuracy and value of such indirect calculations com- piled for most Eel Management Units throughout the European Union. It is concluded that restocking eels to freshwaters may be futile as a conservation measure in some situations, and better escapement is likely achieved in restocking eels to coastal waters or undammed freshwa- ter systems with a direct connection to the sea.
Contrasting responses to long-term climate change of carbon flows to benthic consumers in two different sized lakes in the Baltic area
(Elsevier, 2018) Belle, Simon; Freiberg, Rene; Poska, Anneli; Agasild, Helen; Alliksaar, Tiiu; Tõnno, Ilmar; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
The study of lake sediments and archived biological remains is a promising approach to better under- stand the impacts of climate change on aquatic ecosystems. Small lakes have been shown to be strongly sensitive to past climate change, but similar information is lacking for large lakes. By identifying re- sponses to climate change of carbon flows through benthic food web in two different sized lakes, we aimed to understand how lake morphometry can mediate the effects of climate change. We recon- structed the dynamics of phytoplankton community composition and carbon resources sustaining chironomid biomass during the Holocene from the combined analysis of sedimentary pigment quanti- fication and carbon stable isotopic composition of subfossil chironomid head capsules (d13 C HC) in a large lake in the Baltic area (Estonia). Our results showed that chironomid biomass in the large lake was mainly sustained by phytoplankton, with no significant relationship between d13 C HC values and tem- perature fluctuations. We suggest that lake morphometry (including distance of the sampling zone to the shoreline, and lake volume for primary producers) mediates the effects of climate change, making large lakes less sensitive to climate change. Complementary studies are needed to better understand differ- ences in organic matter dynamics in different sized lakes and to characterize the response of the aquatic carbon cycle to past climate change.
Corestone lubiväetise efektiivsus happeliste muldade omaduste parandamisel
(Eesti Maaülikool; Maaelu Teadmuskeskus, 2026) Paat, Andreas; Tõnutare, Tõnu; Shanskiy, Merrit; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Mullateaduse õppetool
A deficiency of carbonate material in soil profiles necessitates the liming of agricultural soils, especially in southern Estonia, where soil acidity significantly influences agricultural productivity. Liming is a well-established practice for reducing soil acidity and improving plant growing conditions. The aim of this study was to evaluate the effectiveness of milled limestone produced by Corestone Agri OÜ in improving the properties of acidic soils. A pot experiment was conducted growing rapeseed (Brassica napus subsp. napus) plants on four acidic soils. The lime fertilizer was applied at two rates, corresponding to 50% and 100% of the calculated lime requirement. Soil macronutrient contents were analysed before the experiment and at the end of the trial. The results showed that Corestone lime fertilizer increased soil pH and enhanced calcium and magnesium concentrations, including the Ca:Mg ratio. However, it had a negative effect on soil potassium content. Rapeseed biomass generally increased following the use of lime fertilizer, although nutrient contents in the plants varied. The study demonstrated the potential of Corestone lime fertilizer to improve acidic soils, while also highlights the need for further research on micronutrient availability and nutrient balance in plant nutrition.
The crayfish distribution, feeding plasticity, seasonal isotopic variation and trophic role across ontogeny and habitat in a canyon-shaped reservoir
(Springer, 2020) Veselý, Lukáš; Ercoli, Fabio; Ruokonen, Timo; Bláha, Martin; Kubec, Jan; Buřič, Miloš; Hämäläinen, Heikki; Kouba, Antonín; Chair of Hydrobiology and Fishery, Institute of Agricultural and Environmental Sciences
Man-made reservoirs are important fresh-water ecosystems as they are globally common and share features of both standing and running waters. In streams and lakes, crayfish are an important component of freshwater ecosystems due to their habitat- modifying behaviour, substantial size, omnivorous feeding and often high abundance; however, their trophic role in reservoirs is not known. We evaluated the distribution and diet of noble crayfish (Astacus astacus) in the canyon-shaped, oligotrophic Nýrsko reservoir in West Bohemia region, Czech Republic. Using stable isotope analysis, we quantified the trophic level of all major components of the reservoir food web and investigated seasonal isotopic variation and how the trophic role of noble crayfish varied with habitat and ontogeny. Crayfish were an important food source for both predatory and omnivorous fish and consumed food sources from multiple trophic levels, including detritus, algae, zoobenthos and other crayfish. Throughout ontogeny, crayfish had similar levels of carnivory, but cannibalism was more prevalent in adult crayfish, while juveniles and sub-adults fed more on other zoobenthos. Moreover, crayfish had high feeding plasticity in time, as the relative importance of dominant food sources varied with season. Their feeding plasticity was especially evident in crayfish populations from different habitats, which adapted their feeding strategy to local resources. In addition, pelagic source usage increased with the depth as detritus and algae usage decreased. Proportion of females increased with the depth, while population density showed a unimodal response to the depth gradient. These findings indicate that crayfish are indeed ecologically important species with both direct and indirect roles in the trophic web of this reservoir ecosystem.
Data Descriptor : A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins
(Springer Nature, 2018) Mantzouki, Evanthia; Campbell, James; Van Loon, Emiel; Visser, Petra; Konstantinou, Iosif; Antoniou, Maria; Giuliani, Grégory; Machado-Vieira, Danielle; Gurjão de Oliveira, Alinne; Maronić, Dubravka Špoljarić; Stević, Filip; Pfeiffer, Tanja Žuna; Vucelić, Itana Bokan; Žutinić, Petar; Udovič, Marija Gligora; Plenković-Moraj, Anđelka; Tsiarta, Nikoletta; Bláha, Luděk; Geriš, Rodan; Fránková, Markéta; Christoffersen, Kirsten Seestern; Warming, Trine Perlt; Feldmann, Tõnu; Laas, Alo; Panksep, Kristel; Tuvikene, Lea; Kangro, Kersti; Häggqvist, Kerstin; Salmi, Pauliina; Arvola, Lauri; Fastner, Jutta; Straile, Dietmar; Rothhaupt, Karl-Otto; Fonvielle, Jeremy; Grossart, Hans-Peter; Avagianos, Christos; Kaloudis, Triantafyllos; Triantis, Theodoros; Zervou, Sevasti-Kiriaki; Hiskia, Anastasia; Gkelis, Spyros; Panou, Manthos; McCarthy, Valerie; Perello, Victor C.; Obertegger, Ulrike; Boscaini, Adriano; Flaim, Giovanna; Salmaso, Nico; Cerasino, Leonardo; Koreivienė, Judita; Karosienė, Jūratė; Kasperovičienė, Jūratė; Savadova, Ksenija; Vitonytė, Irma; Haande, Sigrid; Skjelbred, Birger; Grabowska, Magdalena; Karpowicz, Maciej; Chmura, Damian; Nawrocka, Lidia; Kobos, Justyna; Mazur-Marzec, Hanna; Alcaraz-Párraga, Pablo; Wilk-Woźniak, Elżbieta; Krztoń, Wojciech; Walusiak, Edward; Gagala, Ilona; Mankiewicz-Boczek, Joana; Toporowska, Magdalena; Pawlik-Skowronska, Barbara; Niedźwiecki, Michał; Pęczuła, Wojciech; Napiórkowska-Krzebietke, Agnieszka; Dunalska, Julita; Sieńska, Justyna; Szymański, Daniel; Kruk, Marek; Budzyńska, Agnieszka; Goldyn, Ryszard; Kozak, Anna; Rosińska, Joanna; Szeląg-Wasielewska, Elżbieta; Domek, Piotr; Jakubowska-Krepska, Natalia; Kwasizur, Kinga; Messyasz, Beata; Pełechata, Aleksandra; Pełechaty, Mariusz; Kokocinski, Mikolaj; Madrecka, Beata; Kostrzewska-Szlakowska, Iwona; Frąk, Magdalena; Bańkowska-Sobczak, Agnieszka; Wasilewicz, Michał; Ochocka, Agnieszka; Pasztaleniec, Agnieszka; Jasser, Iwona; Antão-Geraldes, Ana M.; Leira, Manel; Hernández, Armand; Vasconcelos, Vitor; Morais, João; Vale, Micaela; Raposeiro, Pedro M.; Gonçalves, Vítor; Aleksovski, Boris; Krstić, Svetislav; Nemova, Hana; Drastichova, Iveta; Chomova, Lucia; Remec-Rekar, Spela; Elersek, Tina; Delgado-Martín, Jordi; García, David; Cereijo, Jose Luís; Gomà, Joan; Trapote, Mari Carmen; Vegas-Vilarrúbia, Teresa; Obrador, Biel; García-Murcia, Ana; Real, Monserrat; Romans, Elvira; Noguero-Ribes, Jordi; Duque, David Parreño; Fernández-Morán, Elísabeth; Úbeda, Bárbara; Gálvez, José Ángel; Marcé, Rafael; Catalán, Núria; Pérez-Martínez, Carmen; Ramos-Rodríguez, Eloísa; Cillero-Castro, Carmen; Moreno-Ostos, Enrique; Blanco, José María; Rodríguez, Valeriano; Montes-Pérez, Jorge Juan; Palomino, Roberto L.; Rodríguez-Pérez, Estela; Carballeira, Rafael; Camacho, Antonio; Picazo, Antonio; Rochera, Carlos; Santamans, Anna C.; Ferriol, Carmen; Romo, Susana; Soria, Juan Miguel; Hansson, Lars-Anders; Urrutia-Cordero, Pablo; Özen, Arda; Bravo, Andrea G.; Buck, Moritz; Colom-Montero, William; Mustonen, Kristiina; Pierson, Don; Yang, Yang; M. H. Verspagen, Jolanda; De Senerpont Domis, Lisette N.; Seelen, Laura; Teurlincx, Sven; Verstijnen, Yvon; Lürling, Miquel; Maliaka, Valentini; Faassen, Elisabeth J.; Latour, Delphine; Carey, Cayelan C.; W. Paerl, Hans; Torokne, Andrea; Karan, Tünay; Demir, Nilsun; Beklioğlu, Meryem; Filiz, Nur; E. Levi, Eti; Iskin, Uğur; Bezirci, Gizem; Tavşanoğlu, Ülkü Nihan; Çelik, Kemal; Özhan, Koray; Karakaya, Nusret; Koçer, Mehmet Ali Turan; Yilmaz, Mete; Maraşlıoğlu, Faruk; Fakioglu, Özden; Soylu, Elif Neyran; Yağcı, Meral Apaydın; Çınar, Şakir; Çapkın, Kadir; Yağcı, Abdulkadir; Cesur, Mehmet; Bilgin, Fuat; Bulut, Cafer; Uysal, Rahmi; Köker, Latife; Akçaalan, Reyhan; Albay, Meriç; Alp, Mehmet Tahir; Özkan, Korhan; Sevindik, Tuğba Ongun; Tunca, Hatice; Önem, Burçin; Richardson, Jessica; Edwards, Christine; Bergkemper, Victoria; O'Leary, Sarah; Beirne, Eilish; Cromie, Hannah; Ibelings, Bastiaan W.; Institute of Agricultural and Environmental Sciences
Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.
Detecting Climate Driven Changes in Chlorophyll-a Using High Frequency Monitoring: The Impact of the 2019 European Heatwave in Three Contrasting Aquatic Systems
(MDPI, 2021) Free, Gary; Bresciani, Mariano; Pinardi, Monica; Giardino, Claudia; Alikas, Krista; Kangro, Kersti; Rõõm, Eva-Ingrid; Vaičiūtė, Diana; Bučas, Martynas; Tiškus, Edvinas; Hommersom, Annelies; Laanen, Marnix; Peters, Steef; Chair of Hydrobiology and Fishery
The frequency of heatwave events in Europe is increasing as a result of climate change. This can have implications for the water quality and ecological functioning of aquatic systems. We deployed three spectroradiometer WISPstations at three sites in Europe (Italy, Estonia, and Lithuania/Russia) to measure chlorophyll-a at high frequency. A heatwave in July 2019 occurred with record daily maximum temperatures over 40 ◦C in parts of Europe. The effects of the resulting storm that ended the heatwave were more discernable than the heatwave itself. Following the storm, chlorophyll-a concentrations increased markedly in two of the lakes and remained high for the duration of the summer while at one site concentrations increased linearly. Heatwaves and subsequent storms appeared to play an important role in structuring the phenology of the primary producers, with wider implications for lake functioning. Chlorophyll-a peaked in early September, after which a wind event dissipated concentrations until calmer conditions returned. Synoptic coordinated high frequency monitoring needs to be advanced in Europe as part of water management policy and to improve knowledge on the implications of climate change. Lakes, as dynamic ecosystems with fast moving species-succession, provide a prism to observe the scale of future change.

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