Artiklid

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

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Effects of warming and nutrients on the microbial food web in shallowlake mesocosms
(Elsevier, 2018) Zingel, Priit; Cremona, Fabien; Nõges, Tiina; Cao, Yu; Neif, Érika M.; Coppens, Jan; Işkın, Uğur; Lauridsen, Torben; Davidson, Thomas A.; Søndergaard, Martin; Beklioglu, Meryem; Jeppesen, Erik; Centre for Limnology. Institute of Agricultural and Environmental Sciences
We analysed changes in the abundance, biomass and cell size of the microbial food web community (bacteria, heterotrophicnanoflagellates, ciliates) at contrasting nutrient concentrations and temperatures during a simulated heat wave. We used 24mesocosms mimicking shallow lakes in which two nutrient levels (unenriched and enriched by adding nitrogen and phosphorus)and three different temperature scenarios (ambient, IPCC A2 scenario and A2+%50) are simulated (4 replicates of each).Experiments using the mesocosms have been running un-interrupted since 2003. A 1-month heat wave was imitated by anextra 5◦C increase in the previously heated mesocosms (from 1st July to 1st August 2014). Changes in water temperatureinduced within a few days a strong effect on the microbial food web functioning, demonstrating a quick response of microbialcommunities to the changes in environment, due to their short generation times. Warming and nutrients showed synergisticeffects. Microbial assemblages of heterotrophic nanoflagellates and ciliates responded positively to the heating, the increasebeing largest in the enriched mesocosms. The results indicate that warming and nutrients in combination can set off complexinteractions in the microbial food web functioning.
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.
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.
Microbiome and Culture Based Analysis of Chronic Rhinosinusitis Compared to Healthy Sinus Mucosa
(Frontiers, 2018) Koeller, Kerstin; Herlemann, Daniel P. R.; Schuldt, Tobias; Ovari, Attila; Guder, Ellen; Podbielski, Andreas; Kreikemeyer, Bernd; Olzowy, Bernhard; Center of Limnology. Estonian University of Life Sciences
The role of bacteria in chronic rhinosinusitis (CRS) is still not well understood. Whole microbiome analysis adds new aspects to our current understanding that ismainly based on isolated bacteria. It is still unclear how the results of microbiome analysis and the classical culture based approaches interrelate. To address this, middle meatus swabs and tissue samples were obtained during sinus surgery in 5 patients with CRS with nasal polyps (CRSwNP), 5 patients with diffuse CRS without nasal polyps (CRSsNP), 5 patients with unilateral purulent maxillary CRS (upm CRS) and 3 patients with healthy sinus mucosa. Swabs were cultured, and associated bacteria were identified. Additionally, parts of each tissue sample also underwent culture approaches, and in parallel DNA was extracted for 16S rRNA gene amplicon-based microbiome analysis. From tissue samples 4.2 ± 1.2 distinct species per patient were cultured, from swabs 5.4 ± 1.6. The most frequently cultured species from the swabs were Propionibacterium acnes, Staphylococcus epidermidis, Corynebacterium spp. and Staphylococcus aureus. The 16S-RNA gene analysis revealed no clear differentiation of the bacterial community of healthy compared to CRS samples of unilateral purulent maxillary CRS and CRSwNP. However, the bacterial community of CRSsNP differed significantly from the healthy controls. In the CRSsNP samples Flavobacterium, Pseudomonas, Pedobacter, Porphyromonas, Stenotrophomonas, and Brevundimonas were significantly enriched compared to the healthy controls. Species isolated from culture did not generally correspond with the most abundant genera in microbiome analysis. Only Fusobacteria, Parvimonas, and Prevotella found in 2 unilateral purulent maxillary CRS samples by the cultivation dependent approach were also found in the cultivation independent approach in high abundance, suggesting a classic infectious pathogenesis of odontogenic origin in these two specific cases. Alterations of the bacterial community might be a more crucial factor for the development of CRSsNP compared to CRSwNP. Further studies are needed to investigate the relation between bacterial community characteristics and the development of CRSsNP.
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.
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.
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.
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.
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.
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.
Relationships between fisheries, foodweb structure, and detrital pathway in a large shallow lake
(Springer, 2018) Cremona, Fabien; Järvalt, Ain; Bhele, Upendra; Timm, Henn; Seller, Siim; Haberman, Juta; Zingel, Priit; Agasild, Helen; Nõges, Peeter; Nõges, Tiina; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
We modeled energy transfer and trophic position of fish, plankton, and macroinvertebrates and the relative importance of top-down versus bottom-up processes in Lake Võrtsjärv, a large shallow eutrophic lake in Estonia (northeastern Europe). We employed input values based on 37 years of biomass and fishing activity monitoring for calibrating the Ecopath with Ecosim (EwE) model. Energy flows from primary producers and detritus, represented by total system throughput, were nearly equal (51 and 49%, respec- tively). Simulation revealed that top-down and bot- tom-up forces were at play, metazooplankton was not efficiently grazing phytoplankton production, and a trophic cascade proceeded through macroinverte- brates rather than through zooplankton. Detritivory was responsible for the relatively low trophic position of Võrtsjärv fish compared to other lakes. Bottom-up processes were the main drivers for the dual, primary production- and detritus-based pathways in energy flow. Our findings suggest that the predicted biomass increase of cyanobacteria in shallow lakes in the future will strengthen the reliance of consumers on the detrital pathway at the expense of the primary production pathway.
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.
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.
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.
Factors controlling the three-decade long rise in cyanobacteria biomass in a eutrophic shallow lake
(Elsevier, 2018) Cremona, Fabien; Tuvikene, Lea; Haberman, Juta; Nõges, Peeter; Nõges, Tiina; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Estonian University of Life Sciences
We aimed at quantifying the importance of limnological variables in the decadal rise of cyanobacteria biomass in shallow hemiboreal lakes. We constructed estimates of cyanobacteria (blue-green algae) biomass in a large, eutrophic lake (Estonia, Northeastern Europe) from a database comprising 28 limnological variables and spanning more than 50 years of monitoring. Using a dual-model approach consisting in a boosted regression trees (BRT) followed by a generalized least squares (GLS) model, our results revealed that six variables were most influential for assessing the variance of cyanobacteria biomass. Cyanobacteria response to nitrate concentration and rotifer abundance was negative, whereas it was positive to pH, temperature, cladoceran and copepod biomass. Response to total phosphorus (TP) and total phosphorus to total nitrogen ratio was very weak, which suggests that actual in-lake TP concentration is still above limiting values. The most efficient GLS model, which explained nearly two thirds (r2 = 0.65) of the variance of cyanobacteria biomass included nitrate concentration, water temperature and pH. The very high number of observations (maximum n = 525) supports the robustness of the models. Our results suggest that the decadal rise of blue-green algae in shallow lakes lies in the interaction between cultural eutrophication and global warming which bring in-lake physical and chemical conditions closer to cyanobacteria optima.
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.
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.
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.
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.

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