Catchment land cover and soil as predictors of organic carbon, nitrogen, and phosphorus levels in temperate lakes : [presentation]

The presentation took place at the 10th International Conference on Shallow Lakes in 2021.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program

Whole-genome sequencing illuminates multifaceted targets of selection to humic substances in Eurasian perch

Extreme environments are inhospitable to the majority of species, but some organisms are able to survive in such hostile conditions due to evolutionary adaptations. For example, modern bony fishes have colonized various aquatic environments, including perpetually dark, hypoxic, hypersaline and toxic habitats. Eurasian perch (Perca fluviatilis) is among the few fish species of northern latitudes that is able to live in very acidic humic lakes. Such lakes represent almost "nocturnal" environments; they contain high levels of dissolved organic matter, which in addition to creating a challenging visual environment, also affects a large number of other habitat parameters and biotic interactions. To reveal the genomic targets of humic-associated selection, we performed whole-genome sequencing of perch originating from 16 humic and 16 clear-water lakes in northern Europe. We identified over 800,000 single nucleotide polymorphisms, of which >10,000 were identified as potential candidates under selection (associated with >3000 genes) using multiple outlier approaches. Our findings suggest that adaptation to the humic environment may involve hundreds of regions scattered across the genome. Putative signals of adaptation were detected in genes and gene families with diverse functions, including organism development and ion transportation. The observed excess of variants under selection in regulatory regions highlights the importance of adaptive evolution via regulatory elements, rather than via protein sequence modification. Our study demonstrates the power of whole-genome analysis to illuminate the multifaceted nature of humic adaptation and provides the foundation for further investigation of causal mutations underlying phenotypic traits of ecological and evolutionary importance

Humic-acid-driven escape from eye parasites revealed by RNA-seq and target-specific metabarcoding

Background: Next generation sequencing (NGS) technologies are extensively used to dissect the molecular mechanisms of host-parasite interactions in human pathogens. However, ecological studies have yet to fully exploit the power of NGS as a rich source for formulating and testing new hypotheses.Methods: We studied Eurasian perch (Perca fluviatilis) and its eye parasite (Trematoda, Diplostomidae) communities in 14 lakes that differed in humic content in order to explore host-parasite-environment interactions. We hypothesised that high humic content along with low pH would decrease the abundance of the intermediate hosts (gastropods), thus limiting the occurrence of diplostomid parasites in humic lakes. This hypothesis was initially invoked by whole eye RNA-seq data analysis and subsequently tested using PCR-based detection and a novel targeted metabarcoding approach.Results: Whole eye transcriptome results revealed overexpression of immune-related genes and the presence of eye parasite sequences in RNA-seq data obtained from perch living in clear-water lakes. Both PCR-based and targeted-metabarcoding approach showed that perch from humic lakes were completely free from diplostomid parasites, while the prevalence of eye flukes in clear-water lakes that contain low amounts of humic substances was close to 100%, with the majority of NGS reads assigned toTylodelphys clavata.Conclusions: High intraspecific diversity ofT. clavataindicates that massively parallel sequencing of naturally pooled samples represents an efficient and powerful strategy for shedding light on cryptic diversity of eye parasites. Our results demonstrate that perch populations in clear-water lakes experience contrasting eye parasite pressure compared to those from humic lakes, which is reflected by prevalent differences in the expression of immune-related genes in the eye. This study highlights the utility of NGS to discover novel host-parasite-environment interactions and provide unprecedented power to characterize the molecular diversity of cryptic parasites.</div

Reoveepuhastuse käsiraamat

Vett vajavad eluks kõik meie planeedil elavad organismid, sh inimesed. Eestis kasutatakse olmes ja tootmises nii pinna- kui ka põhjavett. Suur osa sellest jõuab kanalisatsiooni ning tuleb enne loodusesse tagasi juhtimist või taaskasutamist puhastada. Seda tehakse reoveepuhastis, milles kulgevate keerukate protsesside rakendamiseks on vaja mitmesuguseid seadmeid ning haritud insenere ja töömehi. Aegade jooksul on Eestis välja antud palju juhendeid ning mõni kanalisatsiooni ja veekaitset käsitleva õpikki, aga kõiki reovee puhastamisega seotud aspekte ühiste kaante vahel varem käsitletud ei ole. Ometi on meil olemas hulk spetsialiste, kes oma lausa legendaarsetelt vanema põlvkonna õpetlastelt ja inseneridelt saadud erialateadmisi järjepidevalt täiendavad ja edasi annavad. Reoveekäitlus on kallis ning selle areng sai Eestis suure tõuke käesoleva sajandi alguses, mil tekkis võimalus kasutada Keskkonnainvesteeringute Keskuse (SA KIK) ja Euroopa Liidu tugiprogrammide toetusi. Kuigi veevarustuse ja kanalisatsiooni suuremad projektid on tänaseks lõppenud ning veevarustus- ja kanalisatsioonitööde hüppelist kasvu ei ole ette näha, tuleb neid süsteeme siiski käigus hoida, arendada ja optimeerida. Keskkonnaministeerium on aastaid korraldanud hankeid reoveepuhastite operaatorite koolitamiseks. Alates 2017. aastast on võimalik Järvamaa Kusehariduskeskuses omandada veekäitlusoperaatori kutse ning Tallinna Tehnikaülikoolis, Eesti Maaülikoolis ja Tartu Ülikoolis koolitatakse reoveekäitluse insenere ja tehnolooge. Kuigi reoveekäitluse eriala on võimalik õppida erineva taseme (kutse- või kõrghariduse vormis) õppekavade järgi, on puudu tänapäevasel tasemel õppekirjandusest, sest viimased põhjalikumad eestikeelsed õpikud pärinevad 1980-ndate esimesest poolest. Nagu muudki majandusvaldkonnad, areneb reovee puhastamine tänapäeval väga kiiresti. Täienevad standardid ning õigusaktidki. Et ajaga kaasas käia, peavad vee- ja reoveevaldkonnas tegutsejad end pidevalt täiendama: lugema erialaõpikuid, tuhlama internetis, külastama reoveepuhasteid ja messe ning tundma huvi selle vastu, mida teevad erialaorganisatsioonid. Meie vee puhtus põhineb ju erialasel pädevusel. Käesolev käsiraamat on valminud projekti LIFE IP CleanEST raames, mida rahastavad Euroopa Komisjoni LIFE-programm ja Eesti riik. Raamatu koostamisel püüti olla nii põhjalik, et seda saaks kasutada kutse- ja kõrgkoolis õpetamisel, oleks aga arusaadav ka neile veemajanduse valdkonna inimestele, kelle töökohustuste hulka reovee puhastamine ei kuulu. Et reoveekäitlus on väga lai ning kiiresti arenev valdkond, ei pruugi raamatus olla kajastatud kõik puhastustehnoloogiad ja -võtted, ent 4 andsime endast parima, et peamine käsitletud saaks. Kuigi raamatu kirjutamisel tugineti suuresti erialastandarditele (peamiselt Saksa normidele) ning välismaistele kõrgkooliõpikutele, arvestati ka teadusuuringute tulemusi, milles on varasemaid teadmisi oluliselt täpsustatud või lausa ümber kujundatud. Erilist rõhku on pööratud eestikeelsele oskussõnavarale, et aidata ühtlustada eri erialade inimeste keelepruuki. Eestikeelsed terminid seoti peamiselt maailma teaduskeele lingua franca'ks kujunenud inglise keelega, ent ka vene keelega, sest arvestatav osa reoveepuhastite operaatoritest on venekeelsed. Oskussõnavalimiku koostasid Aleksander Maastik, Raili Kärmas, Karin Pachel, Vallo Kõrgmaa, Mait Kriipsalu ja Vjačeslav Mutavči, tuginedes peamiselt standardile EVS-EN 16323. Käsiraamatu koostasid Eesti juhtivad teadlased ja erialaspetsialistid, kelle põhitöökohaks on mõni Eesti õppeasutus või projekteerimis- ja konsultatsiooniettevõte. Raamat valmis tänu nende inimeste pikaajalisele ja heale koostööle. Suur tänu kõigile, kes oma pingelise töö kõrvalt leidsid piisavalt aega peatükkide kirjutamiseks ja/või kolleegide kirjutatu retsenseerimiseks. Avaldame siirast tänu emeriitprofessor Aleksander Maastikule, kes ühtlustas autorite esialgsed tekstid lihtsamini loetavaks. Illustreerivad fotod püüdsime valida autorite isiklikest arhiividest ning valdav osa skeemidest on autorite koostatud. Muude autorite jooniseid on vajadusel eestindanud või kohandanud. Kasutatud allikatele on viidatud õpiku põhijaotiste kaupa. Lugeja peab silmas pidama, et viidatud on õigusaktide 2023. aastal kehtivale versioonile, ning et alati on vaja kontrollida, ega seda muudetud ole. Head lugemist! Vallo Kõrgmaa ja Mait KriipsaluKäsiraamat on valminud LIFE IP CleanEST projekti raames, mida rahastavad Euroopa Komisjoni LIFE programm ja Eesti riik. LIFE programmi rahastusleping nr LIFE17 IPE/EE/000007. Käsiraamat kajastab autorite seisukohti ja Euroopa Komisjon ei vastuta sisu kasutamise eest.Käsiraamat on valminud LIFE IP CleanEST projekti raames, mida rahastavad Euroopa Komisjoni LIFE programm ja Eesti riik. LIFE programmi rahastusleping nr LIFE17 IPE/EE/000007. Käsiraamat kajastab autorite seisukohti ja Euroopa Komisjon ei vastuta sisu kasutamise eest

Do organic matter metrics included in lake surveillance monitoring in Europe provide a broad picture of brownification and enrichment with oxygen consuming substances?

Organic matter (OM) has numerous geochemical and ecological functions in inland waters and can affect water quality. Different parameters of aquatic OM are measured with various methods as no single analytical tool can provide definitive structural or functional information about it. In the present paper we review different OM met- rics used in the European Union (EU) lake surveillance monitoring programmes and assess their suitability to provide sufficient data about the brownification and enrichment with oxygen consuming substances in European lakes. In the EU Water Framework Directive (WFD), metrics of OM are not mandatory physico- chemical parameters, but only recommended parameters to characterize water transparency, oxygenation con- ditions or acidification status. Our analysis shows that, as lake OM is monitored under the WFD in only 14 coun- tries, no Europe-wide conclusions on the situation regarding brownification and organic enrichment can be drawn based on these data. Applied parameters in lake surveillance monitoring programmes are biochemical ox- ygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), dissolved organic carbon (DOC), water colour (WCol), and yellow substance. Different national OM metrics used avoid getting a broad pic- ture of lake OM concentration changes in Europe over the last decades. Furthermore, our results demonstrate that the possibilities to convert different OM parameters to each other are limited because empirical relationships between them are region-specific. OM sensors for continuous measurements and remote sensing surveys could improve the effectiveness of lake OM monitoring, especially its temporal and spatial representativeness. It would be highly suggested to include in lake monitoring programmes also methods (e.g. absorbance or fluorescence spectroscopy) allowing to characterize the composition of OM as it influences strongly the biogeochemical role of OM in lakes.This research was supported by Estonian Ministry of Education and Research through the institutional project IUT 21-2 and personal research grant PUT777, by the MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), by Estonian Science Founda tion grant ETF9102 and by national scholarship program Kristjan Jaak, which is funded and managed by Archimedes Foundation in collaboration with the Ministry of Education and Research.This research was supported by Estonian Ministry of Education and Research through the institutional project IUT 21-2 and personal research grant PUT777, by the MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), by Estonian Science Foundation grant ETF9102 and by national scholarship program Kristjan Jaak, which is funded and managed by Archimedes Foundation in collaboration with the Ministry of Education and Research

The role of catchment soils and land cover on dissolved organic matter (DOM) properties in temperate lakes

Dissolved organic matter (DOM) is a critical component in freshwater ecosystem functioning. The main sources of DOM in lakes are allochthonous inputs from the catchment and autochthonous in-lake production. This study focused on the role of catchment characteristics on the qualitative and quantitative properties of DOM in small temperate lakes along a gradient of alkalinity. We examined DOM properties based on the optical absorbance and fluorescence measurements of water from 34 Estonian lakes. The content and composition of DOM were highly diverse in the lakes studied, e.g. the dissolved organic carbon (DOC) concentrations varied from 3.2 to 53.0 mg L−1 . Land cover, soil, and catchment hydrology and geology had substantial effects on DOM in lakes. Stock of soil organic carbon (SOC) in the catchment and water exchange rate (a descriptor of catchment hy- drology, reciprocal of water residence time) had major positive effects on DOC concentrations. The aromaticity and molecular weight of DOM, i.e. the relative abundance of humic substances, and the dominance of al- lochthonous DOM increased with the drainage ratio (catchment area/lake area) and the percentages of bogs, and Dystric and Fibric Histosols (peat soils in transitional mires and bogs, respectively) in the catchments. Dominance of non-humic over humic substances and autochthonous over allochthonous DOM in lakes corre- sponded to calcareous catchments and higher percentages of Gleyic Rendzinas (thin soils on calcareous rock), Sapric Histosols (peat soils in mires) and open spaces (areas with little vegetation). Our results showed that soil variables had in general a greater effect than land cover and were more informative for describing the role of catchment characteristics on DOM in lakes. Patterns in DOM quantity and quality found in our study were similar to patterns found in other temperate lakes; therefore, our results have important implications for un- derstanding catchment-lake interactions across the temperate region.This work was supported by Estonian Ministry of Education and Research through the institutional project IUT 21-2 and the grant PUT1598, by the European Regional Development Fund through the scholarship programme Dora Plus. The Estonian Ministry of Environment and Estonian Environment Agency supported data collection in the national monitoring programme.This work was supported by Estonian Ministry of Education and Research through the institutional project IUT 21-2 and the grant PUT1598, by the European Regional Development Fund through the scholarship programme Dora Plus. The Estonian Ministry of Environment and Estonian Environment Agency supported data collection in the national monitoring programme

How light conditions influence theoretical pelagic to benthic primary production ratios in small lakes

Theoretical pelagic primary production of phytoplankton and benthic primary production of periphyton were modelled for two small lakes in Estonia (Northeast Europe). Although located only 500 m apart, the water colour and light attenuation of these two lakes differed markedly. The Secchi depth (SD) in the clear-water lake was 4.5 m and only 0.47 m in the dark-water lake. The total phosphorus (TP) concentrations were, respectively, 15 μg/l and 28 μg/l. An empirical model whose inputs were morphometric, light conditions and dissolved organic carbon parameters obtained from in situ measurements was employed for the present study. The model calculated primary production with a time-step of 10 min, and a spatial resolution of 10 cm, from sunrise to sunset and from lake surface to lake bottom. The primary production of periphyton and phytoplankton was almost equal in the clear lake, whereas only phy- toplankton contributed to whole-lake primary production in the dark lake because of the stronger light attenuation in the water column. The results of the present study indicated the depth-distribution profiles differed dramatically between the two lakes. The clear lake had a deep, U-shaped curve, with the productive layer reaching considerable depth soon after sunrise and maintaining a similar profile throughout the light hours. In contrast, the dark lake production declined rapidly with increasing depth, whereas the profile changed over the day reaching the greatest depth at noon.The authors are thankful to the 16th World Lake Conference Organizing Committee for having given them the opportunity to present the results of their research in Bali, Indonesia. This re- search was supported by Estonian Research Council Grants PUT 777, PSG 32 and IUT 21-2 of the Estonian Ministry of Education and Research, and by MARS project (Managing Aquatic ecosys- tems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract No. 603378 (http://www.mars-project. eu).The authors are thankful to the 16th World Lake Conference Organizing Committee for having given them the opportunity to present the results of their research in Bali, Indonesia. This re- search was supported by Estonian Research Council Grants PUT 777, PSG 32 and IUT 21-2 of the Estonian Ministry of Education and Research, and by MARS project (Managing Aquatic ecosys- tems and water Resources under multiple Stress) funded under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract No. 603378 (http://www.mars-project. eu)

General Description of Partly Meromictic Hypertrophic Lake Verevi, its Ecological Status, Changes during the Past Eight Decades, and Restoration Problems

Lake Verevi (surface 12.6 ha, mean depth 3.6 m, maximum depth 11 m, drainage area 1.1 km2, water exchange 0.63-times per year) is a hypertrophic hardwater lake located in town Elva (6400 inhabitants). Long-term complex limnological investigations have taken place since 1929. The lake has been contaminated by irregular discharge of urban wastewaters from oxidation ponds since 1978, flood from streets, and infiltrated waters from the surrounding farms. The so-called spring meromixis occurred due to extremely warm springs in recent years. The index value of buffer capacity of Lake Verevi calculated from natural conditions is on the medium level. Water properties were analysed according to the requirements of the EU Water Framework Directive.JRC.H.5-Rural, water and ecosystem resource

Algal Diet of Small-Bodied Crustacean Zooplankton in a Cyanobacteria-Dominated Eutrophic Lake.

Small-bodied cladocerans and cyclopoid copepods are becoming increasingly dominant over large crustacean zooplankton in eutrophic waters where they often coexist with cyanobacterial blooms. However, relatively little is known about their algal diet preferences. We studied grazing selectivity of small crustaceans (the cyclopoid copepods Mesocyclops leuckarti, Thermocyclops oithonoides, Cyclops kolensis, and the cladocerans Daphnia cucullata, Chydorus sphaericus, Bosmina spp.) by liquid chromatographic analyses of phytoplankton marker pigments in the shallow, highly eutrophic Lake Võrtsjärv (Estonia) during a seasonal cycle. Copepods (mainly C. kolensis) preferably consumed cryptophytes (identified by the marker pigment alloxanthin in gut contents) during colder periods, while they preferred small non-filamentous diatoms and green algae (identified mainly by diatoxanthin and lutein, respectively) from May to September. All studied cladoceran species showed highest selectivity towards colonial cyanobacteria (identified by canthaxanthin). For small C. sphaericus, commonly occuring in the pelagic zone of eutrophic lakes, colonial cyanobacteria can be their major food source, supporting their coexistence with cyanobacterial blooms. Pigments characteristic of filamentous cyanobacteria and diatoms (zeaxanthin and fucoxanthin, respectively), algae dominating in Võrtsjärv, were also found in the grazers' diet but were generally avoided by the crustaceans commonly dominating the zooplankton assemblage. Together these results suggest that the co-occurring small-bodied cyclopoid and cladoceran species have markedly different algal diets and that the cladocera represent the main trophic link transferring cyanobacterial carbon to the food web in a highly eutrophic lake