Ingmar Ott | Estonian University of Life Sciences (original) (raw)

Papers by Ingmar Ott

Proceedings of the Estonian Academy of Sciences. Biology. Ecology

Changes of phyto-and zooplankton in 205 and bacterioplankton in 304 Estonian lakes in 1951-93 are... more Changes of phyto-and zooplankton in 205 and bacterioplankton in 304 Estonian lakes in 1951-93 are discussed. In eutrophic lakes the average values of the total count of bacteria in bacterioplankton were lower in the 1990 s than in the 19705. The deterioration of the regime in lakes is characterized by changes in the structure of bacterial communities in the bottom water layers and increasing total count of bacteria. Relatively extensive changes occurred in phyto-and zooplankton species composition, specifically replacement of species with larger dimensions by smaller ones. The concentration of nutrients and the amount of plankton were on the highest level in the 19705. Subsequently these values, as well as the trend of precipitation, fell. It means that there existed the effect of dilution. The values of the parameters of the ecological state were the highest in the 1980 s. The response of biota to the influence of eutrophic factors was shifted in time. The recent improvement demonstrates the self-purification capability of Estonian lakes.

Springer eBooks, Jan 12, 2006

The vertical and temporal distribution of metazooplankton in the small hypertrophic, strongly str... more The vertical and temporal distribution of metazooplankton in the small hypertrophic, strongly stratified, temperate Lake Verevi (Estonia) was studied during 1998-2001. The zooplankton of Lake Verevi is characteristic of hypertrophic lakes, with a small number of dominant species, rotifers being the main ones, and juveniles prevailing among copepods. In 1999-2001, the average abundance of metazooplankton in the lake was 1570 • 10 3 ind m)3 ; in the epilimnion 2320 • 10 3 ind m)3 , in the metalimnion 2178 • 10 3 ind m)3 , and in the hypolimnion 237 • 10 3 ind m)3. The average biomass of metazooplankton was 1.75 g m)3 ; in the epi-, meta-and hypolimnion, accordingly, 2.16, 2.85 and 0.26 g m)3. The highest abundances-19,136 • 10 3 ind m)3 and 12,008 • 10 3 ind m)3-were registered in the lower half of the metalimnion in 24 May and 5 June 2001, respectively. Rotifer Keratella cochlearis f. typica (Gosse, 1851) was the dominating species in abundance. In biomass, Asplanchna priodonta Gosse, 1850, among the rotifers, and Eudiaptomus graciloides (Lilljeborg, 1888), among the copepods, dominated. According to the data from 2000-2001, the abundance and biomass of both copepods and rotifers were highest in spring. Zooplankton was scarce in the hypolimnion, and no peaks were observed there. During the summers of 1998 and 1999, when thermal stratification was particularly strong, zooplankton was the most abundant in the upper half of the metalimnion, and a distinct peak of biomass occurred in the second fourth of the metalimnion. Probably, the main factors affecting the vertical distribution of zooplankton in L. Verevi are fish, Chaoborus larvae, and chemocline, while food, like phytoplankton, composition and abundance may affect more the seasonal development of zooplankton.

The seasonal dynamics of water chemistry, temperature, adenosintriphosphate (ATP), and chlorophyl... more The seasonal dynamics of water chemistry, temperature, adenosintriphosphate (ATP), and chlorophyll a (Chl) congentration, and the biomass and production of phyto-, zoo-and bacterioplankton was investigated during the vegetation periods of 1985 and 1986. Statistical analysis revealed that the intensity and balance of production processes were chiefly affected by water temperature. Seasonal observations of ATP and Chl concentrations showed an accumulation of "dead" chlorophyll in autumn. This was evidently caused by the predominance of large algae, non-edible for zooplankton, and reduced destruction activity in cold water. The decay of the algal mass during winter may cause oxygen deficiency and the appearance of HyS on the bottom of the lake. The average production values per vegetation period for the years studied were as follows: phytoplankton-203.5 g C-m~2% bacterioplankton-379 g Cm -2; filterfeeding zooplankton-20.6 в С.т-?; and predatory zooplankton-1.5 g Cm -2 Herbivorous zooplankton production constituted 10.1% of primary production. This ratio indicates that filtrators feed mostly on living algae while the deirital food chain seems to be of little importance. Bacteria meet on ап average 11% о zooplankton food requirements. The mean destruction activity (D) was 2.166 g C-m~2-day~!. D exceeded gross primary production in almost all cases. Evidently, the sharp peaks of primary production were missed because of long measuring intervals; the organic matter, produced during these peaks, raises D for a longer period. Moreover, the early phytoplankton maximum during the under-ice or ice-break period was not observed, which could cause an underestimation of the yearly phytoplankton production value.

Springer eBooks, Jan 12, 2006

The small strongly stratified hard-water hypertrophic lake Verevi (max. depth 11.0 m, surface are... more The small strongly stratified hard-water hypertrophic lake Verevi (max. depth 11.0 m, surface area 12.6 ha, mean depth 3.6 m) was investigated in 2000 and in 2001. The lake is sheltered from winds, and the role of waves in mixing the water column is minimal. Eutrophication favours the strengthening of stratification. Early warm springs cause a fast stagnation of the water column forming partly meromictic conditions. Seston content of water and in sediment traps in 3 layers was measured several times during the formation of stratification. Besides measuring particulate matter, in 2001, the nutrient content of the trapped sediment was analysed. During the first 7 days of the investigation, 30% of the total particle sedimentation took place. The sedimentation rate of particulate matter was 0.4-6.3 g m-2 d)1 dry weight in different layers of the water column. Daily average sedimentation loss rate was 27% of the total amount of seston of the epilimnion, whilst from the meta-and hypolimnion the settling was much slower (9.6 and 7.3%, respectively). In our experiments with twin sediment traps, to one of which formaldehyde was added, the PO 4 3)-P concentration was 19% smaller in the trap without formaldehyde, probably due to planktonic uptake. The relationship between primary and export production is loop-like. The shape was irregular, indicating a high grazing rate of zooplankton.

Springer eBooks, Jan 12, 2006

Changes in the phytoplankton community of the hypertrophic, sharply stratified Lake Verevi have b... more Changes in the phytoplankton community of the hypertrophic, sharply stratified Lake Verevi have been studied over eight decades. Due to irregular discharge of urban wastewater, the trophic state of the lake has changed from moderately eutrophic to hypertrophic. We found that the trophic state in summer increased in the 1980s and remained at a hypertrophic level since then. Planktothrix agardhii was recorded first in the 1950s and became the dominant species in the 1980s, forming biomass maxima under the ice and in the metalimnion during the vegetation period. In summer 1989, P. agardhii contributed almost 100% of the phytoplankton biomass. Generally, the highest biomass values occurred in the metalimnion. In spring, when P. agardhii was less numerous, diatoms and cryptophytes prevailed. In springs 2000 and 2001 different diatoms dominated-Synedra acus var. angustissima (18.6 g m)3) and Cyclostephanos dubius (9.2 g m)3), respectively. In recent years, the spring overturn has been absent. In the conditions of strong thermal stratification sharp vertical gradients of light and nutrients caused a large number of vertically narrow niches in the water column. During a typical summer stage, the epilimnion, dominated by small flagellated chrysophytes, is nearly mesotrophic, and water transparency may reach 4 m. The lower part of the water column is hypertrophic with different species of cryptophytes and euglenophytes. A characteristic feature is the higher diversity of Chlorococcales. Often, species could form their peaks of biomass in very narrow layers, e.g. in August 2001 Ceratium hirundinella (18.6 g m)3) was found at a depth of 5 m (the lower part of the metalimnion with hypoxic conditions), Cryptomonas spp. (56 g m)3) at 6 m (with traces of oxygen and a relatively high content of dissolved organic matter) and euglenophytes (0.6 g m)3) at 7 m and deeper (without oxygen and a high content of dissolved organic matter).

HAL (Le Centre pour la Communication Scientifique Directe), 2014

MS Conclusion on compliance Boundary setting procedure BE-FL Compliant Chlorophyll boundaries mat... more MS Conclusion on compliance Boundary setting procedure BE-FL Compliant Chlorophyll boundaries match IC phase 1. % Cyanobacteria boundaries based on expert judgment DK Compliant Chlorophyll boundaries match IC phase 1. EQR values taken from values agreed for phase 1 intercalibration. Taxonomic metric boundaries are based on distribution of species along a pressure gradient of TP. Final selection of taxa based on expert judgement. EE Compliant Chlorophyll GM EQR boundary very slightly higher than values agreed in IC phase 1. Estonian phytoplankton method uses pressure response relationship. Phytoplankton scores vs. land-use index reveals model describability r 2 0.53. Boundary setting procedure uses expert judgement, palaeolimnological data, historical records and information from reference sites. FR Compliant Chlorophyll boundary EQR values vary with mean depth of the lake. And for lakes with depth >3m are within range agreed in phase 1. Chlorophyll HG boundary for lakes with depth <3m is lower than value agreed for phase 1. Boundaries for both Chlorophyll (biomass MBA) and species composition metric (MCS) defined from pressure response relationship with equal size status class for log total phosphorus DE Compliant Chlorophyll boundary values fall within range agreed for phase 1. Boundaries for other metrics derived from pressure response relationships using German LAWA and Total P index, supported by expert judgement. IE Compliant, although LCB2 chlorophyll boundaries are tighter than used for phase 1 Chlorophyll boundary EQR values for LCB1 taken from values agreed for phase 1. Boundary for LCB2 based on expert judgement and is lower than the range agreed in phase 1. Boundary for IPI metric derived from discontinuity in relationship between pressure and biological response. LT Compliant Chlorophyll boundary values significantly lower than values agreed for LCB2 lakes and slightly lower for LCB1 lakes. EQR for combined chlorophyll mean and max metric lower than those agreed for mean chlorophyll a in phase 1. Boundaries derived by equal division along EQR gradient for chlorophyll and taxonomic metrics LV Compliant Chlorophyll boundary values fall within range agreed for phase 1. Boundaries for other metrics derived from EE method NL Compliant Chlorophyll boundary values taken from values agreed in phase 1 intercalibration. Taxonomic boundaries based on expert judgement. PL Compliant Chlorophyll boundary values fall within range agreed for phase 1. Boundaries for total biomass and cyanobacteria biomass derived from classifications based on chlorophyll.

Archiv für Hydrobiologie, Aug 1, 2003

... and hydrochemical samples were treated by a number of researchers (MAIA PORK, VIIVE KÕVASK, R... more ... and hydrochemical samples were treated by a number of researchers (MAIA PORK, VIIVE KÕVASK, REET LAUGASTE, INGMAR OTT). ... BROOKS,AS; WARREN, G.; BORAAS, ME; SCALE, DB & EDGINGTON, DN (1985): Long-term phytoplankton changes in Lake Michigan ...

Hydrobiologia, Sep 1, 2005

Journal of Applied Ecology, Mar 11, 2014

The implementation of the Water Framework Directive requires EU member states to establish and ha... more The implementation of the Water Framework Directive requires EU member states to establish and harmonize ecological status class boundaries for biological quality elements. In this paper, we describe an approach for defining ecological class boundaries that delineates shifts in lake ecosystem functioning and, therefore, provides ecologically meaningful targets for water policy in Europe. 2. We collected an extensive data set of 810 lake-years from nine Central European countries, and we used phytoplankton chlorophyll a, a metric widely used to measure the impact of eutrophication in lakes. Our approach establishes chlorophyll a target values in relation to three significant ecological effects of eutrophication: the decline of aquatic macrophytes, the dominance of potentially harmful cyanobacteria and the major functional switch from a clear water to a turbid state. 3. Ranges of threshold chlorophyll a concentrations are given for the two most common lake types in lowland Central Europe: for moderately deep lakes (mean depth 3-15 m), the greatest ecological shifts occur in the range 10-12 lg L À1 chlorophyll a, and for shallow lakes (<3 m mean depth), in the range 21-23 lg L À1 chlorophyll a. 4. Synthesis and applications. Our study provides class boundaries for determining the ecological status of lakes, which have robust ecological consequences for lake functioning and which, therefore, provide strong and objective targets for sustainable water management in Europe. The results have been endorsed by all participant member states and adopted in the European Commission legislation, marking the first attempt in international water policy to move from physico-chemical quality standards to harmonized ecologically based quality targets.

Archiv für Hydrobiologie, Aug 1, 2003

The occurrence and coexistence of Planktothrix agardhii and Limnothrix, redekei were studied base... more The occurrence and coexistence of Planktothrix agardhii and Limnothrix, redekei were studied based on pooled long-term databases of Danish and Estonian lakes. P. agardhii was more common in Denmark and L. redekei in Estonian lakes. Most of the variables, which mean values differed while grouped by species (Secchi depth, Chl a, light attenuation coefficient, phosphates and total P contents, N/P ratio, pH) showed a higher trophic status associated with the occurrence of P agardhii compared with L. redekei. The analysis showed that the higher water transparency in redekei lakes could not be the factor explaining the success of L. redekei but was rather a phenomenon accompanying the lower phosphorus level. The often observed later invasion of L. redekei into lakes inhabited by P. agardhii cannot be explained by differences in the species nutrient requirements. L. rededkei developed seasonally earlier than P. agardhii but still signs of competition could be revealed in cases of their mass occurence. For L. redekei the coexistence with P agardhii was more common than the occurrence without P. agardhii.

Opik on valminud riikliku programmi „Eestikeelsete korgkooliopikute koostamine ja valjaandmine (2... more Opik on valminud riikliku programmi „Eestikeelsete korgkooliopikute koostamine ja valjaandmine (2008–2012)“ raames ning Eesti Maaulikooli ja Sihtasutuse Archimedes osalisel toel.

KäsiraamatEessõna järvede tervendamise käsiraamatule Kui veel 1950 – 60-ndatel aastatel võis enam... more KäsiraamatEessõna järvede tervendamise käsiraamatule Kui veel 1950 – 60-ndatel aastatel võis enamiku Eesti järvede seisundit pidada looduslikuks, siis 21. sajandi alguseks on paljude järvede seisund peamiselt tugeva inimmõju tagajärjel märkimisväärselt halvenenud. Hinnanguliselt 10 – 12% meie järvedest on halvas seisundiklassis ja vajaks kindlasti tervendamist. Lisaks on veel palju järvi , mille seisund ei ole küll päris halb, aga vajab siiski parandamist. Euroopa Liidus 2000. aastal rakendunud veepoliitika raamdirektiiv seab eesmärgiks saavutada aastaks 2015 liikmesriikide kõigi vete, sh pinnavee, põhjavee, reovee ja joogivee, hea seisund. Pinnaveekogudes tuleb lisaks vee heale keemilisele seisundile saavutada ka hea ökoloogiline seisund. Kui veekogu seisund pole hinnatud heaks või väga heaks, tuleb kasutusele võtta meetmed vähemalt hea seisundi saavutamiseks. Selleks võib olla piisav veekogu majandamise ümberkorraldamine, kuid enamasti tähendab see vajadust astuda konkreetseid samme valgalalt saabuva reostuskoormuse vähendamiseks ja ka veekogu enese tervendamiseks. Järvede kui suure loodusväärtuse hea seisund on oluline ka inimese tervise seisukohast. Terved ja kaunid järved pakuvad puhkamiseks ja töövõime taastamiseks mitmekülgseid võimalusi, mille hulgas on kalastamine kindlasti üks märkimisväärsemaid. Keskkonnaministeeriumi korraldatud küsitlusel harrastuspüüdjate seas selgus, et enim häirivad hobikalureid veekogudele ligipääsu puudumine ja väike vääriskalavaru, kuid ka veekogude halb olukord ja üldine kala vähesus. Tervendamine võimaldab lisaks järvede olukorra parandamisele tervikuna taastada või tõsta ka nende kalamajanduslikku väärtust. Nagu igal elualal, on ka järvede tervendamise alases sõnavaras kasutusel palju sama või osaliselt kattuva tähendusega mõisteid. Levinuim vaste järvede tervendamisele on olnud „restaureerimine” , mis on eesti keelde tulnud ingliskeelsest mõistest restoration , otsetõlkena on palju kasutatud ka „taastamist”. Võõrsõna ja selle sisult ebatäpsete eestikeelsete vastete asemel on järveteadlased üsna edukalt suutnud juurutada hoopis kodusema kõlaga ja pehmema sisuga mõistet „tervendamine”. Käsiraamatu esimeses peatükis soovitatakse tervendamise terminoloogiat vastavalt sellele, kui põhjalikku sekkumist on järve seisundi parandamiseks vaja. Seal leiab käsitlemist tervendamise kitsam tähendus. Nii selle käsiraamatu pealkirjas kui tekstis kasutame enamasti seda mõistet laiemas tähenduses, mis hõlmab kõiki järvede olukorra parandamisega seotud tegevusi ja viise olenemata sellest, kui põhjalikke muutusi läbi viiakse. Eestis jõudsalt hoogu koguv järvede tervendamine on seni põhinenud üsna lünklikel ja juhuslikel teadmistel, kuna meil on puudunud seda teemat tervikuna ja põhjalikult käsitlev eestikeelne kirjandus. Heal juhul on järvede tervendajad leidnud üles järveteadlased ja lasknud enne järve kallale asumist teha uuringud, saamaks teada, mis on järve seisundi halvenemise tegelikud põhjused. Keskkonnainvesteeringute Keskuse toel Eesti Maaülikoolis valminud artiklite kogum on „Järvede tervendamise käsiraamatu” käsikiri, mis vajab enne päris raamatuks saamist veel toimetamist. Kuna vajadus sellise juhend- ja õppematerjali järele on suur, siis on käsikirjalised artiklid juba avalikult kättesaadavaks tehtud. Esimene peatükk tutvustab järveteaduse ehk limnoloogia aluseid, mis aitavad mõista järvede tervendamise põhimõtteid. Teises peatükis antakse ülevaade Eesti järvede tervendamisvajadusest. Kolmas peatükk käsitleb kogu tervendamisega kaasnevat protsessi, alates idee tekkimisest ja asja kohasest seadusandlusest ning lõpetades järelseirega. Järgnevad peatükid käsitlevad tervendamise meetodeid: biomanipulatsioon (peatükk 4), vee hapnikuga rikastamine (peatükk 5) , veerežiimi muutmine (peatükk 6) , makrofüüdijärvede tervendamine (peatükk 7), vee ja setete keemilise töötlemise meetodid (peatükk 8) ja setete eemaldamine (peatükk 9). Peatükk 10 tutvustab järve veetaseme tõstmise ja sette eemaldamise ehitusprojektidega seonduvat. Peatükis 11 leiavad käsitlemist keskkonnamõjude hindamine ja järvede hooldus. Kuigi näiteid järvede tervendamisest leidub igas konkreetseid meetodeid käsitlevas peatükis, annab viimane, 12. peatükk veel ülevaate veekogude tervendamise senistest kogemustest Eestis ja mujal Euroopas ning kirjeldab põhjalikumalt mõnd huvitavamat tervendamise näidet nii meilt kui mujalt maa ilmast. Käsikirja autorid loodavad, et kirjapandust on abi järvede tervendamisega seotud inimestele ja lõppkokkuvõttes meie paljude järvede tervisele. Kõik täiendused, parandused ja ettepanekud, mis võiksid kaasa aidata sisuka ja kasuliku käsiraamatu valmimisele, on teretulnud aadressile: Lea Tuvikene, Limnoloogiakeskus, Rannu 61117, Tartumaa , või e - posti aadressile lea.tuvikene@emu.eeKeskkonnainvesteeringute Kesku

Hydrobiologia, Oct 30, 2012

Analysis of phytoplankton data from about 1500 lakes in 20 European countries has revealed that t... more Analysis of phytoplankton data from about 1500 lakes in 20 European countries has revealed that two-thirds of the species that dominate lakes during the summer are dominant right acrossEurope. Using Canonical Correspondence Analyses, we have examined how both habitat conditions within lakes and environmental factors over broad geographical scales explained the distribution of the 151 most common summer dominant species. The distributions of these species were best explained by water colour and latitude, although alkalinity and total phosphorus also appeared to be important explanatory factors. Contrary to our original hypothesis, summer water temperatures had a negligible impact on the distribution of dominants, although, due to the restricted summer season we examined, only a limited temperature gradient was present in the dataset. Cryptophytes occurred more frequently among dominants in Northern Europe whereas cyanobacteria and dinophytes dominated more in Central and Southern Europe. Our analyses suggest that besides nutrient concentrations, other water chemistry variables, such as alkalinity and the content of humic substances, have at least as important a role in determining the distribution of the dominant phytoplankton species in European lakes.

Aquatic Conservation-marine and Freshwater Ecosystems, Mar 31, 2003

1. The European Water Framework Directive requires the determination of ecological status in Euro... more 1. The European Water Framework Directive requires the determination of ecological status in European fresh and saline waters. This is to be through the establishment of a typology of surface water bodies, the determination of reference (high status) conditions in each element (ecotype) of the typology and of lower grades of status (good, moderate, poor and bad) for each ecotype. It then requires classification of the status of the water bodies and their restoration to at least 'good status' in a specified period. 2. Though there are many methods for assessing water quality, none has the scope of that defined in the Directive. The provisions of the Directive require a wide range of variables to be measured and give only general guidance as to how systems of classification should be established. This raises issues of comparability across States and of the costs of making the determinations. 3. Using expert workshops and subsequent field testing, a practicable pan-European typology and classification system has been developed for shallow lakes, which can easily be extended to all lakes. It is parsimonious in its choice of determinands, but based on current limnological understanding and therefore as cost-effective as possible. 4. A core typology is described, which can be expanded easily in particular States to meet local conditions. The core includes 48 ecotypes across the entire European climate gradient and incorporates climate, lake area, geology of the catchment and conductivity. 5. The classification system is founded on a liberal interpretation of Annexes in the Directive and uses variables that are inexpensive to measure and ecologically relevant. The need for taxonomic expertise is minimized. 6. The scheme has been through eight iterations, two of which were tested in the field on tranches of 66 lakes. The final version, Version 8, is offered for operational testing and further refinement by statutory authorities.

Euroopa Liidu Veepoliitika Raamdirektiiv (VRD) reguleerib vee kasutamise ja selle hea seisundi sä... more Euroopa Liidu Veepoliitika Raamdirektiiv (VRD) reguleerib vee kasutamise ja selle hea seisundi säilitamisega seotud seaduseid ning regulatsioone liikmesriikides. Vesi on hindamatu ressurss, mistõttu nõuab dokument liikmesriikidelt pingutusi ja tegevusi, et saavutada pinnavete hea keemiline ja ökoloogiline seisund. Pullijärv1 on pehme ja heleda veega eutrofeerunud oligotroofne järv ning siin elavad mitmed haruldased looduskaitsealused liigid. Lisaks on järv olulise rekreatsioonilise väärtusega kohalike seas. Viimaste uuringute käigus on järve ökoloogiline seisund olnud kesine ja mitmed kvaliteedinäitajad on oluliselt halvenenud. Seetõttu on vajalik uurida “mittehea” seisundi põhjuseid ja töötada välja tõhusad meetmed järve seisundi parandamiseks. Eesti Maaülikool esitas Keskkonnainvesteeringute Keskuse (KIK) poolt läbiviidud taotlusvooru projekti nr 14705 “Järvede seisundi parandamiseks vajalike uuringute teostamine ja meetmekavade väljatöötamine” taotluse, mis rahastati pooles mahus. Läbirääkimiste tulemusel kooskõlastati uus lähteülesanne Keskkonnaameti poolt 28.09.2018. a (nr 7-18/18/3808-6). Uus lähteülesanne keskendub Pullijärve (VEE2155200) mittehea seisundi põhjuste väljaselgitamisele. Uuringute käigus selgitati olemasolevate andmete alusel Pullijärve seisundi dünaamikat alates 1950. aastatest tänapäevani, uuriti sise- ja väliskoormust ning pakuti välja meetmed järve seisundi parandamiseks. Uurimismeetodid, mida kasutati hüdrokeemilistel analüüsidel ja elustiku uuringutel, on standardiseeritud või interkalibreeritud ja vastavad seadustes äratoodud nõuetele ning nendega on võimalik tutvuda põhjalikumalt töö metoodika peatükkides. Parameetrite seisundi klassipiirid pärinevad keskkonnaministri määrusest nr 44 (Pinnaveekogumite…, 2009). Töö eesmärk on välja töötada meetme- ja tegevuskava Pullijärve hea ökoloogilise seisundi saavutamiseks järgmise veemajanduskava perioodi jooksul (2020-2027). Uuringu lõpparuanne koosneb kahest osast: Esimeses osas (järve seisundi dünaamika) antakse ülevaade Pullijärve funktsioneerimisest ja kvaliteedielementide dünaamikast. Esitatakse välis- ja sisekoormuse uuringute tulemused. Teises osas (meetme- ja tegevuskava) kirjeldatakse kliima mõju pehme- ja heledaveelisele järvele, antakse ülevaade ökosüsteemiteenustest ning pakutakse välja meetme- ja tegevuskava koos ajakavaga. Uuringut viisid läbi ja aruande koostasid Eesti Maaülikooli Põllumajandus- ja keskkonnainstituudi Hüdrobioloogia ja kalanduse õppetooli teadlased: prof. Ingmar Ott, Ph.D. (vastutav täitja), M.Sc. Ronald Laarmaa, M.Sc. Kairi Maileht, Ph.D. Sirje Vilbaste, Ph.D. Margot Sepp, M.Sc. Katrin Saar, Ph.D Henn Timm, M.Sc. Anu Palm ja Katrin Ott

Ilmastikumuutused on väga laiahaardelised ja mõjutavad kõiki Maa ökosüsteeme. Ühe põhilise kasvuh... more Ilmastikumuutused on väga laiahaardelised ja mõjutavad kõiki Maa ökosüsteeme. Ühe põhilise kasvuhoonegaasi, süsihappegaasi (CO2), kontsentratsioon võib 2050. aastateks kahekordistuda, ületades 700 ppm (George 2010) ning IPCC (Intergovernmental Panel of Climate Change 2018) andmetel võib selle sajandi lõpuks õhutemperatuur tõusta kuni 7 kraadi (Nõges, Nõges 2011), mis tähendab olulist survet nii maismaa kui ka vee ökosüsteemidele. Riigid seisavad silmitsi üha enam süvenevate probleemidega, kus kliimasurve ühelt poolt muudab kvaliteedinäitajate dünaamikaid ja teisalt raskendab veekogude hea ökoloogilise seisundi saavutamist. Mitmete stressorite koosmõju mõjutab tugevalt magevee ökosüsteeme, see kandub edasi toiduahela kaudu, mõjutades otseselt ökosüsteemi funktsioneerimist, dünaamikat ja struktuuri (Li et al. 2019). Eesti järvi on uuritud üle saja aasta, mis sobiks kliimast tingitud muutuste jälgimiseks ja selgitamiseks. Paraku tuleb aru saada, et järjepidevat aegrida uuringuandmetest saaks koostada ehk meie suurjärvede kohta. Pikem aegrida on ka Ülemiste kohta. Selle järve haldamine on erafirma käes ja andmete kasutamine teatavate piirangutega. Hiljuti valmis meie asutuse poolt tehtud Ülemiste järve käsitlev uurimus („Ülemiste järve limnoloogiline eksperthinnang“), mis sobib hästi antud projekti konteksti ja soovitame sellekohaseid tulemusi küsida aktsiaseltsilt Tallinna Vesi. Enamuse väikejärvede kohta on andmeid küll üsna varajasest ajast, st inventuurides möödunud sajandi 1920ndaist ja 1930ndaist, kuid enamasti on andmeid vaid ühekordsetest vaatlustest kasvuperioodil. Põhjalikke kompleksseid uuringuid tehti alates 1951. aastast, kuid taas uuriti erinevatel aastatel erinevaid järvi ja enamasti korra suvel. Väikejärvede püsivaatlusi alustati alles 1992. aastal hüdrobioloogilise seire käigus. Tollest ajast on siiani pidevas uurimises ainult kuus järve. Sellises olukorras saame teha ülevaateid suhteliselt lühikese aja jooksul ja väheste järvede kohta. See tähendab, et pigem saame käsitleda ilma mõju veekogudele ja saame esitada ekspertarvamusi kliima mõju kohta. Hindasime kliima ja ilma mõju kuue erineva väikejärve keemilise ja bioloogilise seisundi kujunemisele kasutades väikejärvede hüdrobioloogilise ja hüdrokeemilise varasemate uuringute raames kogutud andmeid ja uurimistulemusi. Järvede füüsikalis-keemiliste parameetrite ja elustiku dünaamika muutuste selgitamiseks kasutati väikejärvede hüdrobioloogilise ja hüdrokeemilise seire käigus kogutud andmeid ja eksperthinnanguid. Ilmastiku mõju hindamiseks kasutati Riigi Ilmateenistuse ajaloolisi andmeid õhutemperatuuri ja sademete kohta. Peamised küsimused, millele püüdsime vastust leida: - Millised on kliima ja ilma muutumise (keskmine õhutemperatuur, sademed ja neist tulenevad näitajad) otsesed ja kaudsed mõjud väikejärve ökosüsteemi funktsioneerimisele? - Muutuste ja põhjuste selgitamine ning tulevikustsenaariumite kirjeldamine. - Ettepanekute tegemine väikejärvede seisundi säilitamiseks. Võimalusel tehakse prognoose järvede kliimamuutustega kohanemiseks

Fundamental and Applied Limnology, 2010

With 4 fi gures and 3 tables

Archiv für Hydrobiologie, Oct 27, 1995

Vegetation History and Archaeobotany, Nov 29, 2017

This study demonstrates the power of multiproxy palaeolimnological analyses in investigating envi... more This study demonstrates the power of multiproxy palaeolimnological analyses in investigating environmental changes in the Lake Kooraste Linajärv ecosystem through historical time in response to flax retting. Flax retting history was proven by applying pollen and macrofossil evidence and by using several biotic and geochemical proxies on a sediment core. Continuous findings of flax pollen and macrofossil remains in lake sediments were considered as strong evidence for the occurrence of retting. Analyses of the welldated sediment core show the consequences of flax retting in the lake. As a result, the once clear soft water oligotrophic endorheic lake with limited sedimentation has turned into a hypertrophic high-sedimentation lake with anoxic bottom water, strong stratification and intense water blooms. Despite the fact that flax retting was forbidden in Estonia around ad 1950s and retting has not occurred over the last six decades, anthropogenic alterations were so pervasive in the past, that they have prevented any lake water improvements until the present-day. Communicated by M.-J. Gaillard.

Proceedings of the Estonian Academy of Sciences. Biology. Ecology

Springer eBooks, Jan 12, 2006

HAL (Le Centre pour la Communication Scientifique Directe), 2014

Archiv für Hydrobiologie, Aug 1, 2003

Hydrobiologia, Sep 1, 2005

Journal of Applied Ecology, Mar 11, 2014

Archiv für Hydrobiologie, Aug 1, 2003

Hydrobiologia, Oct 30, 2012

Aquatic Conservation-marine and Freshwater Ecosystems, Mar 31, 2003

Fundamental and Applied Limnology, 2010

With 4 fi gures and 3 tables

Archiv für Hydrobiologie, Oct 27, 1995

Vegetation History and Archaeobotany, Nov 29, 2017