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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.
Evaluation of dried amorphous ferric hydroxide CFH-12® as agent for binding bioavailable phosphorus in lake sediments
(Elsevier, 2018) Fuchs, Elisabeth; Funes, Ana; Saar, Katrin; Reitzel, Kasper; Jensen, Henning S.; Centre for Limnology. Estonian University of Life Sciences
Metal hydroxides formed from aluminum (Al) and iron (Fe) salts can be used as phosphorus (P) adsorbents in lake restoration, but the application entails problems in low-alkaline lakes due to acid producing hydrolysis and potential formation of toxic metal ions. Therefore, we tested the potential of applying CFH-12® (Kemira) – a dried, amorphous Fe-oxide with no pH effect – in lake restoration. Since Fe3+ may become reduced in lake sed- iments and release both Fe2+ and any associated P we also evaluated the redox sensitivity of CFH-12® in com- parison with freshly formed Fe(OH)3. CFH-12® was added to undisturbed sediment cores from three Danish lakes relative to the size of their mobile P pool (molar Fe:PMobile dose ratio of ~10:1), and P and Fe fluxes across the sediment-water interface were compared with those from untreated cores and cores treated with freshly formed Fe(OH)3. Under anoxic conditions, we found that CFH-12® significantly reduced the P efflux from the sediments (by 43% in Lake Sønderby, 70% in Lake Hampen and 60% in Lake Hostrup) while the Fe 2+ efflux remained unchanged relative to the untreated cores. Cores treated with freshly formed Fe(OH)3 retained more P, but released significantly more Fe 2+ , indicating continued Fe3+ reduction. Finally, experiments with pure phases showed that CFH-12® adsorbed less P than freshly formed Fe(OH)3 in the short term, but was capable of adsorbing up to 70% of P adsorbed by Fe(OH)3 over 3 months. With product costs only 30% higher than Al salts we find that CFH-12® has potential for use in restoration of low-alkaline lakes.
Towards understanding the abundance of non-pollen palynomorphs : A comparison of fossil algae, algal pigments and sedaDNA from temperate lake sediments
(Elsevier, 2018) Stivrins, Normunds; Soininen, Janne; Tõnno, Ilmar; Freiberg, Rene; Veski, Siim; Kisand, Veljo; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Given the increased interest in non-pollen palynomorphs (microscopic objects other than pollen identified from pollen slides) in palaeoecological studies, it is necessary to seek a deeper understanding of the reliability of these results. We combined quantitative information of algal pigments and sedimentary ancient DNA (sedaDNA) of phylotaxonomical resolution to validate the richness and abundance of fossil algae in the sediment of a small temperate lake. For the first time, fossil and sedaDNA algae data were combined in a composite data-set and used to reconstruct algae turnover rates over the last 14,500 years. This comparison serves as both an example of howfossil algae can be used to answer various research questions and as a method of revealing towhat extent we can rely on palaeoecological interpretations based solely on the fossil algae record from pollen slides.
Introduced alien signal crayfish (Pacifastacus leniusculus) in Finland - uncontrollable expansion despite numerous crayfisheries strategies
(EDP Sciences, 2018) Ruokonen, Timo J.; Sjövik, Rosanna; Erkamo, Esa; Tulonen, Jouni; Ercoli, Fabio; Kokko, Harri; Jussila, Japo; Centre for Limnology. Institute of Agricultural and Environmental Sciences
In Finland, massive signal crayfish introductions started towards the end of 1980s, with an estimated total of 2.2 million signal crayfish been stocked before year 2016. During that period, Finnish fisheries authorities have implemented three national management strategies setting guidelines for the crayfish introductions. The main aims of the strategies have been conservation of native noble crayfish stocks and a controlled spreading of the alien signal crayfish within a designated region. In this study, we report the current distribution of signal crayfish in Finland in comparison to the guidelines set in these three national strategies. The present distribution area of the signal crayfish covers most of the Southern Finland. The signal crayfish has been introduced with a stocking permits to over 480 water bodies. In addition, there have been numerous stockings without permits, which are often next to the region designated for signal crayfish. Based on the results, we conclude that crayfisheries strategies adopted in Finland have only had limited effect on the spread of signal crayfish. We presume that main causes for the uncontrolled spreading of the signal crayfish in Finland have been lack of strict official supervision and general lack of awareness about the risks associated with the alien species spreading.
A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters
(Springer, 2018) Engel, Fabian; Farrell, Kaitlin J.; McCullough, Ian M.; Scordo, Facundo; Denfeld, Blaize A.; Dugan, Hilary A.; De Eyto, Elvira; Hanson, Paul C.; McClure, Ryan P.; Nõges, Peeter; Nõges, Tiina; Ryder, Elizabeth; Weathers, Kathleen C.; Weyhenmeyer, Gesa A.; Centre for Limnology. Estonian University of Life Sciences
The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precip- itation in lakes, we estimated that the global lateral DIC export can lie within the range of 0:70þ0:27 −0:31 to 1:52þ1:09 −0:90 Pg C yr−1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.
Linking atmospheric, terrestrial and aquatic environments : Regime shifts in the Estonian climate over the past 50 years
(PLOS, 2018) Kotta, Jonne; Herkül, Kristjan; Jaagus, Jaak; Kaasik, Ants; Raudsepp, Urmas; Alari, Victor; Arula, Timo; Haberman, Juta; Järvet, Arvo; Kangur, Külli; Kont, Are; Kull, Ain; Laanemets, Jaan; Maljutenko, Ilja; Männik, Aarne; Nõges, Peeter; Nõges, Tiina; Ojaveer, Henn; Peterson, Anneliis; Reihan, Alvina; Rõõm, Rein; Sepp, Mait; Suursaar, Ülo; Tamm, Ottar; Tamm, Toomas; Tõnisson, Hannes; Institute of Agricultural and Environmental Sciences; Institute of Forestry and Rural Engineering
Climate change in recent decades has been identified as a significant threat to natural environments and human wellbeing. This is because some of the contemporary changes to climate are abrupt and result in persistent changes in the state of natural systems; so called regime shifts (RS). This study aimed to detect and analyse the timing and strength of RS in Estonian climate at the half-century scale (1966−2013). We demonstrate that the extensive winter warming of the Northern Hemisphere in the late 1980s was represented in atmospheric, terrestrial, freshwater and marine systems to an extent not observed before or after the event within the studied time series. In 1989, abiotic variables displayed statistically significant regime shifts in atmospheric, river and marine systems, but not in lake and bog systems. This was followed by regime shifts in the biotic time series of bogs and marine ecosystems in 1990. However, many biotic time series lacked regime shifts, or the shifts were uncoupled from large-scale atmospheric circulation. We suggest that the latter is possibly due to complex and temporally variable interactions between abiotic and biotic elements with ecosystem properties buffering biotic responses to climate change signals, as well as being affected by concurrent anthropogenic impacts on natural environments.
Shifting Diatom-Dinoflagellate Dominance During Spring Bloom in the Baltic Sea and its Potential Effects on Biogeochemical Cycling
(Frontiers, 2018) Spilling, Kristian; Olli, Kalle; Lehtoranta, Jouni; Kremp, Anke; Tedesco, Letizia; Tamelander, Tobias; Klais, Riina; Peltonen, Heikki; Tamminen, Timo; Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
The Baltic Sea is affected by a range of human induced environmental pressures such as eutrophication. Here we synthesize the ongoing shift from diatom dominance toward more dinoflagellates in parts of the Baltic Sea during the spring bloom and its potential effects on biogeochemical cycling of key elements (e.g., C, N, and P). The spring bloom is the period with the highest annual primary production and sinking of organic matter to the sediment. The fate of this organic matter is a key driver for material fluxes, affecting ecosystem functioning and eutrophication feedback loops. The dominant diatoms and dinoflagellates appear to be functionally surrogates as both groups are able to effectively exhaust the wintertime accumulation of inorganic nutrients and produce bloom level biomass that contribute to vertical export of organic matter. However, the groups have very different sedimentation patterns, and the seafloor has variable potential to mineralize the settled biomass in the different sub-basins. While diatoms sink quickly out of the euphotic zone, dinoflagellates sink as inert resting cysts, or lyse in the water column contributing to slowly settling phyto-detritus. The dominance by either phytoplankton group thus directly affects both the summertime nutrient pools of the water column and the input of organic matter to the sediment but to contrasting directions. The proliferation of dinoflagellates with high encystment efficiency could increase sediment retention and burial of organic matter, alleviating the eutrophication problem and improve the environmental status of the Baltic Sea.
Functional Assemblages of Macroinvertebrates in Pools and Ditches in Drained Forest Landscape
(Springer, 2018) Vaikre, Maarja; Remm, Liina; Rannap, Riinu; Voode, Margus; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Artificially drained commercial forests are hydrologically novel ecosystems, where the array of aquatic habitats consists of ditches and remnant pools. In general the network of ditches has been found to have longer hydroperiod, the knowledge, however, about aquatic invertebrates in this system is scarce. We examined which environmental factors are impacting the biomass and abundance of functional feeding groups. Scrapers and shredders were aggregated to ditches and gatherers to pools. Filterers’ distribution pattern suggested that the function of filtering is carried out by different taxa in pools and ditches. Ditches were rather more suitable for feeding groups that rely on autochthonous resources. Acidity was a major driver of functional community composition, for example, one of the causes for higher scraper frequency in ditches. Predators exhibited greater quantities in extensive macrophyte cover regardless of water body type. Our results suggest that the trophic organization in ditches and pools is different because habitat factors select the feeding groups directly through food resources, but also because of the environmental filter on the other biological traits of the organisms. To support complex ecosystems with several trophic levels also in commercial forests, we suggest to avoid destroying macrophyte rich pools and ditches during silvicultural management.
Factors behind the variability of phosphorus accumulation in Finnish lakes
(Springer, 2018) Tammeorg, Olga; Haldna, Marina; Nõges, Peeter; Appleby, Peter; Möls, Tõnu; Niemistö, Juha; Tammeorg, Priit; Horppila, Jukka; Centre for Limnology
Purpose Phosphorus retention (TPacc) is one of the major water quality regulators in lakes. The current study aimed at ascer- taining the specific lake characteristics regulating TP acc . Moreover, we were interested whether NAO (North Atlantic Oscillation), a proxy of climatic forcing, can explain variability in TPacc, additionally to that ascribed to lake characteristics. Materials and methods Sediment cores were obtained from 21 Finnish lakes, subject to radiometric dating and measurements of TP concentrations. Principal components (PCs) were generated using lake characteristics that are usually included into the modelling of TPacc (e.g. lake area, lake depth, catchment area, P inflow) but also the parameters that the classical models usually missed (e.g. anoxic factor). We used significant principal components (PCs), specific combinations of lake characteristics and monthly NAO values as predictors of TPacc. Results and discussion Lake characteristics explained the bulk of TPacc variability. The most influential factors (positive drivers) behind TPacc included PC1 (representing mainly deep lakes), PC2 (small lakes with high levels of anoxia and water column stability), PC3 (productive lakes with large catchment area and short water residence time), PC4 (lakes with high water column stability, low anoxic factor and relatively high sediment focusing) and PC5 (lakes with high levels of P inflow, anoxia and long water residence time). Additionally, we found a potential negative effect of NAO in October on the annual TPacc. This NAO was significantly positively related to temperatures in surface and near-bottom water layer (also their difference) in autumn, suggest- ing the possible implications for the internal P dynamics. Increased mineralization of organic matter is the most likely explanation for the reduced TPacc associated with NAO-driven water temperature increase. Conclusions The analysis presented here contributes to the knowledge of the factors controlling P retention. Moreover, this spatially and temporally comprehensive sediment data can potentially be a valuable source for modelling climate change implications.
Macrophyte assessment in European lakes : Diverse approaches but convergent views of ‘good’ ecological status
(Elsevier, 2018) Poikane, Sandra; Portelje, Rob; Denys, Luc; Elferts, Didzis; Kelly, Martyn; Kolada, Agnieszka; Mäemets, Helle; Phillips, Geoff; Sondergaard, Martin; Willby, Nigel; Van den Berg, Marcel S.; Estonian University of Life Sciences. Institute of Agricultural and Environmental Science
The European Water Framework Directive has been adopted by Member States to assess and manage the ecological integrity of surface waters. Specific challenges include harmonizing diverse assessment systems across Europe, linking ecological assessment to restoration measures and reaching a common view on ‘good’ ecological status. In this study, nine national macrophyte-based approaches for assessing ecological status were compared and harmonized, using a large dataset of 539 European lakes. A macrophyte common metric, representing the average standardized view of each lake by all countries, was used to compare national methods. This was also shown to reflect the total phosphorus (r 2 = 0.32), total nitrogen (r 2 = 0.22) as well as chlorophyll-a (r 2 = 0.35–0.38) gradients, providing a link between ecological data, stressors and management decisions. Despite differing assessment approaches and initial differences in classification, a consensus was reached on how type-specific macrophyte assemblages change across the ecological status gradient and where ecological status boundaries should lie. A marked decline in submerged vegetation, especially Charophyta (characterizing ‘good’ status), and an in- crease in abundance of free-floating plants (characterizing ‘less than good’ status) were the most significant changes along the ecological status gradient. Macrophyte communities of ‘good’ status lakes were diverse with many charophytes and several Potamogeton species. A large number of taxa occurred across the entire gradient, but only a minority dominated at ‘less than good’ status, including filamentous algae, lemnids, nymphaeids, and several elodeids (e.g., Zannichellia palustris and Elodea nuttallii). Our findings establish a ‘guiding image’ of the macrophyte community at ‘good’ ecological status in hard-water lakes of the Central-Baltic region of Europe.
Geographic and temporal variations in turbulent heat loss from lakes : A global analysis across 45 lakes
(Wiley, 2018) Woolway, R. Iestyn; Verburg, Piet; Lenters, John D.; Merchant, Christopher J.; Hamilton, David P.; Brookes, Justin; de Eyto, Elvira; Kelly, Sean; Healey, Nathan C.; Hook, Simon; Laas, Alo; Pierson, Don; Rusak, James A.; Kuha, Jonna; Karjalainen, Juha; Kallio, Kari; Lepistö, Ahti; Jones, Ian D.
Heat fluxes at the lake surface play an integral part in determining the energy budget and thermal structure in lakes, including regulating how lakes respond to climate change. We explore patterns in turbulent heat fluxes, which vary across temporal and spatial scales, using in situ high-frequency monitoring data from 45 glob- ally distributed lakes. Our analysis demonstrates that some of the lakes studied follow a marked seasonal cycle in their turbulent surface fluxes and that turbulent heat loss is highest in larger lakes and those situated at low latitude. The Bowen ratio, which is the ratio of mean sensible to mean latent heat fluxes, is smaller at low lati- tudes and, in turn, the relative contribution of evaporative to total turbulent heat loss increases toward the tro- pics. Latent heat transfer ranged from ~ 60% to > 90% of total turbulent heat loss in the examined lakes. The Bowen ratio ranged from 0.04 to 0.69 and correlated significantly with latitude. The relative contributions to total turbulent heat loss therefore differ among lakes, and these contributions are influenced greatly by lake location. Our findings have implications for understanding the role of lakes in the climate system, effects on the lake water balance, and temperature-dependent processes in lakes.
Fish predation pressure on zooplankton in a large northern temperate lake : impact of adult predators versus juvenile predators
(Estonian Academy Publishers, 2018) Ginter, Kai; Blank, Kätlin; Haberman, Juta; Kangur, Andu; Kangur, Külli; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
In recent decades, a marked decrease in planktivorous fish (Osmerus eperlanus eperlanus m. spirinchus Pallas and Coregonus albula (L.)) in Lake Peipsi has stimulated research into the potential effect of fish predation on zooplankton. The abundance of planktivorous fish and the abundance and biomass of zooplankton were studied from 1986 to 2014, and the diet of plankton-eating fish was analysed from 2007 to 2013. A linear regression model was used to establish possible trends in the zooplankton assemblages (biomass, abundance, mean weight of individuals) and in the abundance of zooplankton-eating fish. The ANOVA test was used to evaluate differences in the zooplankton assemblages and in fish consumption in the years with large and small fish cohorts. Despite the collapse of the smelt and vendace populations, the abundance of plankton-eating fish remained high due to an increase in the abundance of juvenile fish. Fish juveniles consumed as much as or even more zooplankton than adult planktivores. Since 1986, a significant decrease was observed in the cladoceran and copepod biomass and in the mean body weight of cladocerans. Large cladocerans such as Leptodora kindtii (Focke) and Bythotrephes longimanus Leydig were rare in zooplankton samples and the biomass of Bosmina spp. decreased. Changes in the structure of the zooplankton community were most likely caused by the feeding of juvenile fish as the calculated consumption by fish was high, especially in years with particularly large fish cohorts.
Response of primary producers to water level fluctuations of Lake Peipsi
(Estonian Academy Publishers, 2018) Mäemets, Helle; Laugaste, Reet; Palmik, Kadi; Haldna, Marina; Centre for Limnology. Institute of Agricultural and Environmental Sciences
The amplitude of natural fluctuation between annual averages of the water level (WL) of Lake Peipsi (3555 km 2) is 1.5 m. A study aimed to examine the impact of WL fluctuations on phytoplankton, macrophytes, and their epiphyton was performed annually at littoral stations during 2005–2015. Also the characteristics of pelagic water were collated with the WL. Changes in littoral and pelagial phytoplankton were similar, with the exclusion of massive wind-caused accumulations of cyanobacteria in the littoral. At the lowest WL a significant increase occurred in (a) the biomass of phytoplankton and the share of phytoplankton-derived organic carbon in water and (b) the species richness and biomass of macrophytes, including submerged plants and macroalgae. The abundance of epiphytes did not reveal a clear relation with the WL. The ratios of biomasses in the years with the lowest and the highest average WL were 2.2 for Potamogeton spp. and 2.6 for phytoplankton. The assessment of ecological status at the minimum and the maximum WL differs at least by one quality class. Decisions about ecological status based on phytoplankton and large filamentous green algae at low water may be contrary to decisions based on macrophytes: high biomasses of phytoplankton and macroalgae indicate hypertrophic status, but species-rich macrovegetation and high biomasses of charophytes and elodeids are considered to be characteristic of meso- to eutrophic water bodies.
Phyto- and Bacterioplankton During Early Spring Conditions in the Baltic Sea and Response to Short-Term Experimental Warming
(Frontiers, 2018) von Scheibner, Markus; Herlemann, Daniel P.R.; Lewandowska, Aleksandra M.; Jürgens, Klaus; Center of Limnology
Predicted increases in sea surface temperatures are expected to shift the balance between autotrophic production and the heterotrophic degradation of organic matter toward a more heterotrophic system. For early phytoplankton spring blooms at low water temperature the impact of rising temperatures has been mainly investigated in mesocosm experiments, while field observations are scarce. During a Baltic Sea research cruise we examined early spring bloom conditions, characterized by low temperatures (0–3◦C), and performed on-board warming experiments to compare the responses of phyto- and bacterioplankton production to an increase in temperature. In the northern Baltic Sea, the low phytoplankton biomass indicated pre-bloom conditions. In the southern Baltic Sea, a diatom-dominated phytoplankton bloom with increased primary production (PP) occurred. Associated with this bloom were increases in bacterial production (BP) and bacterial abundance as well as shifts in bacterial community composition toward an increased proportion of Gammaproteobacteria and Bacteroidetes. However, the low BP/PP ratios (average: 1.2 ± 0.14%) indicated weak coupling between the bacterial and phytoplankton communities. Short-term warming (6 h, 1+6◦C) significantly enhanced PP (mean Q10 1.4) and especially BP (mean Q10 2.3). Hence, the higher water temperature increased both carbon flow into the bacterial community and bacterial processing of organic matter, thereby confirming previous experimental studies. By contrast, BP/PP ratios remained relatively low after warming (average: 1.7 ± 0.5%), unlike in previous mesocosm experiments performed at comparable temperatures and with similar plankton communities. Overall, these results imply that bacterial activities are suppressed during early phytoplankton blooms at low temperatures in the Baltic Sea and are not substantially altered by short-term warming events.
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.
Impact of a Major Inflow Event on the Composition and Distribution of Bacterioplankton Communities in the Baltic Sea
(Frontiers, 2018) Bergen, Benjamin; Naumann, Michael; Herlemann, Daniel P. R.; Gräwe, Ulf; Labrenz, Matthias; Jürgens, Klaus; Centre for Limnology. Estonian University of Life Sciences
Major Baltic inflow (MBI) events carry highly saline water from the North Sea to the central Baltic Sea and thereby affect both its environmental conditions and its biota. While bacterioplankton communities in the Baltic Sea are strongly structured by salinity, how MBIs impact the composition and distribution of bacteria is unknown. The exceptional MBI in 2014, which brought saline and oxygenated water into the basins of the central Baltic Sea, enabled the linkage of microbiological investigations to hydrographic and modeling studies of this MBI. Using sequence data of 16S ribosomal RNA (rRNA) and 16S rRNA genes (rDNA), we analyzed bacterioplankton community composition in the inflowing water and in the uplifted former bottomwater at stations reached by the MBI. Bacterial diversity data were compared with respective data obtained from previous, non-inflow conditions. Changes in bacterial community composition following the 2014 MBI were mainly apparent at the genus level. A number of specific taxa were enriched in the inflowing water, with large changes in the rRNA/rDNA ratios indicating the different activity levels between of the water masses. The relative similarity of the bacterial communities in the inflowing and uplifted waters as well as the results from an inflow-simulating numerical model showed that the inflowing water did not originate directly from the North Sea but mostly from adjacent areas in the Baltic Sea. This suggested that the inflow event led to a series of shifts in Baltic Sea water masses among the Baltic Sea basins and a gradual mixing of the water bodies. Dramatic changes in the bacterial community composition occurred when the bottomwater inflow reached the anoxic, sulfidic deep basins, resulting in an uplifting of the formerly anoxic bacterial community, dominated by Epsilonproteobacteria. Our study of the impact of MBIs on bacterioplankton communities therefore highlights two relevant underlying mechanisms that impact the distribution and possibly also the activities of planktonic bacteria in the Baltic Sea: (1) the successive dilution of inflowing North Sea water with ambient waters and (2) the uplifting of former bottom-water communities to higher water strata.
Otsekülvi mõju mulla kvaliteedile Eesti tootmispõldudel
(Eesti Maaülikool; Eesti Taimekasvatuse Instituut, 2018) Reintam, Endla; Sutri, Merit; Kahu, Greete; Are, Mihkel; Stagerescu, Gheorge; Selge, Are; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Mullateaduse õppetool; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Taimekasvatuse ja taimebioloogia õppetool
Finding out the best agricultural management practices for certain climatic regions and soils is crucial to maintain soils quality. One of the practices, to stop soil erosion, reduce leaching and increase soil organic carbon content, is no-tillage. No tillage is coming more popular also in Estonia. It helps to reduce fuel and labour costs. However, as there is missing decades long practice of no-tillage in Estonia, its effect on soil quality is not clear. At the same time, easy methods to detect soil quality are needed next to the laboratory analyses. During the project iSQPER the visual assessment tool was developed for easy detection of soil quality. The aim of the current study was to compare visual assessment with laboratory measurements on Estonian no-till fields in the 2016. The study was done on sandy loam Gleyic Stagnic Luvisol in Põlva and sandy loam Stagnic Luvisol in Tartu County. Visual assessment was made from the soil upper 30 cm layer, laboratory measurements from 5–10 cm and 25–30 cm depth. The parameters studied were: erodibility, water logging, soil structure and slaking, colour, porosity, plough pan, organic carbon content, penetration resistance and amount of earthworms. The study revealed slightly better soil quality under no-tillage by visual assessment. In most cases laboratory analyses confirmed these results. Structural distribution was better by ploughing compared with no tillage. However, fine aggregate (0.25–2 mm) stability was higher under no-tillage compared with ploughing. There were no significant differences in number of earthworms between practices.
The interaction of soil aggregate stability with other soil properties as influenced by manure and nitrogen fertilization
(Lithuanian Research Centre for Agriculture and Forestry, Vytautas Magnus University, 2018) Are, Mihkel; Kaart, Tanel; Selge, Are; Astover, Alar; Reintam, Endla; Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences; Institute of Veterinary Medicine and Animal Sciences. Estonian University of Life Sciences
Soil water-stable aggregate (WSA) stability is one of the most important indicators of soil health, because it influences chemical, biological and other physical properties. At the same time, WSA formation, stabilization and degradation are also some of the most complex processes that occur in the soil, making them difficult to fully understand. In particular, there is a lack of research on WSA stability in the Baltic region. To gain a better understanding how aggregation occurs in Estonian pedo-climatic conditions, this study was conducted in 2014– 2015 in a sandy loam Stagnic Luvisol (LV-st) (WRB, 2014). Potato and barley plots were analysed in a three-year crop rotation (potato → spring wheat → barley) with straw removal. The nitrogen (N) fertilization treatments were 0, 40, 80, 120 and 160 kg ha-1 yr-1 N, both without and with 40 Mg ha-1 fermented cattle farmyard manure (FYM) application prior to potato planting in the previous autumn. WSA stability was determined by Eijkelkamp’s wet sieving apparatus from air-dried soil samples of less than 2 mm in diameter. The study revealed a negative correlation (r = −0.16) between increased N rates and WSA stability, regardless of FYM applications. Although soil organic carbon (SOC) content increased with additional N fertilization rates, the reduction in soil acidity (pHKCl) levels caused by N fertilization, most likely repealed the positive SOC content effect on WSA stability. In general, compared with sole N fertilization, FYM application had a positive effect on WSA stability. However, even though WSA stability did not always increase with FYM applications, it still had a positive effect on bulk density, SOC content and soil acidity levels. Further research is needed in Estonia due to the complexities involved in the soil aggregation process.
A new species of Enchytraeus (Enchytraeidae, Oligochaeta) from the profundal of Lake Van, the world's largest soda Lake (Turkey, East Anatolia)
(Magnolia Press, 2018) Arslan, Naime; Timm, Tarmo; Rojo, Veronica; Vizcaino, Anton; Schmelz, Rüdiger M.; Estonian University of Life Sciences. Centre for Limnology
Enchytraeus polatdemiri sp. nov. (Enchytaeidae, Oligochaeta) was discovered in the framework of a sampling campaign of the benthic invertebrate fauna of the hyperalkaline Lake Van in Eastern Anatolia, Turkey, the third-largest closed lake and the largest soda lake on Earth. It was the only oligochaete species found in all samples. DNA sequencing included a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene, and a fragment of the nuclear histone 3 (H3) gene. For comparison, specimens from laboratory cultures of E. albidus Henle, 1837, a widespread and morphologically similar species, were sequenced as well. The new species differs from E. albidus in comparatively small body size, 2 or 3 chaetae per bundle, saddle-shaped clitellum, absence of a copulatory field between the male pores and vasa deferentia usu- ally not extending beyond the clitellum. The individual gene trees of COI and H3, as well as the combined phylogenetic analysis of both trees, recovered Enchytraeus polatdemiri sp. nov. as a monophyletic group within the genus Enchytraeus, closely related to E. albidus, but with an average p-distance for COI of 14.5 %. E. polatdemiri sp. nov. may have evolved from a local population of Enchytraeus albidus, a species well-adapted to changing salinity conditions, or from a common ancestor into an extremophile species that dwells and reproduces in the profundal of a strongly alkaline soda lake.
Global patterns in the metacommunity structuring of lake macrophytes: regional variations and driving factors
(Springer, 2018) Alahuhta, Janne; Lindholm, Marja; Bove, Claudia P.; Chappuis, Eglantine; Clayton, John; De Winton, Mary; Feldmann, Tõnu; Ecke, Frauke; Gacia, Esperança; Grillas, Patrick; Hoyer, Mark V.; Johnson, Lucinda B.; Kolada, Agnieszka; Kosten, Sarian; Lauridsen, Torben; Lukács, Balázs A.; Mjelde, Marit; Mormul, Roger P.; Rhazi, Laila; Rhazi, Mouhssine; Sass, Laura; Søndergaard, Martin; Xu, Jun; Heino, Jani; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
We studied community–environment relationships of lake macrophytes at two metacommunity scales using data from 16 regions across the world. More specifically, we examined (a) whether the lake macrophyte communities respond similar to key local environmental factors, major climate variables and lake spatial locations in each of the regions (i.e., within-region approach) and (b) how well can explained variability in the community–environment relationships across multiple lake macrophyte metacommunities be accounted for by elevation range, spatial extent, latitude, longitude, and age of the oldest lake within each metacommunity (i.e., across-region approach). In the within-region approach, we employed partial redundancy analyses together with variation partitioning to investigate the relative importance of local variables, climate variables, and spatial location on lake macrophytes among the study regions. In the across-region approach, we used adjusted R2 values of the variation partitioning to model the community–environment relationships across multiple metacommunities using linear regression and commonality analysis. We found that niche filtering related to local lake-level environmental conditions was the dominant force structuring macrophytes within metacommunities. However, our results also revealed that elevation range associated with climate (increasing temperature amplitude affecting macrophytes) and spatial location (likely due to dispersal limitation) was important for macrophytes based on the findings of the across-metacommunities analysis. These findings suggest that different determinants influence macrophyte metacommunities within different regions, thus showing context dependency. Moreover, our study emphasized that the use of a single metacommunity scale gives incomplete information on the environmental features explaining variation in macrophyte communities.

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