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[{"key": "dc.contributor.advisor", "value": "H\u00e4m\u00e4l\u00e4inen, Heikki", "language": "", "element": "contributor", "qualifier": "advisor", "schema": "dc"}, {"key": "dc.contributor.advisor", "value": "Jyv\u00e4sj\u00e4rvi, Jussi", "language": "", "element": "contributor", "qualifier": "advisor", "schema": "dc"}, {"key": "dc.contributor.author", "value": "Vesala, Inka", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2016-04-06T13:40:03Z", "language": "", "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2016-04-06T13:40:03Z", "language": "", "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2016", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1525279", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/49263", "language": "", "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "J\u00e4rvien vedenlaatua ja ekologista tilaa voidaan pyrki\u00e4 parantamaan erilaisilla kunnostusmenetelmill\u00e4, joista alusveden hapetus on yksi k\u00e4ytetyimmist\u00e4. Alusvett\u00e4 hapetetaan kierr\u00e4tt\u00e4m\u00e4ll\u00e4 p\u00e4\u00e4llysvett\u00e4 pohjanl\u00e4heisyyteen, ja menetelm\u00e4n avulla pyrit\u00e4\u00e4n ehk\u00e4isem\u00e4\u00e4n j\u00e4rven sis\u00e4ist\u00e4 kuormitusta. Hapetus kuitenkin nostaa alusveden l\u00e4mp\u00f6tilaa ja est\u00e4\u00e4 j\u00e4rven luontaisen kerrostumisen. Tieteellisi\u00e4 tutkimuksia hapetuksen pitk\u00e4aikaisista vaikutuksista j\u00e4rvien tilaan on niukasti, vaikka hapetus on ollut suosittu kunnostusmenetelm\u00e4 jo 1970-luvulta l\u00e4htien. T\u00e4ss\u00e4 tutkimuksessa tarkasteltiin kolmen keskisuomalaisen j\u00e4rven (Jyv\u00e4sj\u00e4rvi, Tuomioj\u00e4rvi ja Alvaj\u00e4rvi) syv\u00e4nnepohjael\u00e4inyhteis\u00f6iss\u00e4 tapahtuneita muutoksia vuosina 2000\u20132014, huomioiden erityisesti hapetuksen vaikutukset el\u00e4inyhteis\u00f6ihin. Jyv\u00e4sj\u00e4rvess\u00e4 yli 30 vuotta kest\u00e4nyt alusveden hapetus lopetettiin vuonna 2011, kun taas Tuomioj\u00e4rvell\u00e4 hapetusta tehostettiin aloittamalla ymp\u00e4rivuotinen hapetus kes\u00e4ll\u00e4 2013. Alvaj\u00e4rvi, jossa alusvett\u00e4 ei ole hapetettu, toimi tutkimuksessa vertailukohteena. Tausta-aineistona k\u00e4ytettiin tutkimusj\u00e4rvist\u00e4 mitattuja alusveden happi- ja l\u00e4mp\u00f6tilatietoja sek\u00e4 p\u00e4\u00e4llysveden fosforipitoisuuksia. Jyv\u00e4sj\u00e4rven p\u00e4\u00e4syv\u00e4nteen alusveden l\u00e4mp\u00f6tila kes\u00e4kerrostuneisuuskauden lopussa oli hapetetulla jaksolla keskim\u00e4\u00e4rin 16,6 \u00b0C ja hapettamattomalla jaksolla 7,8 \u00b0C ja hapetuksen pys\u00e4ytys pienensi my\u00f6s pohjanl\u00e4heisen veden happipitoisuutta merkitt\u00e4v\u00e4sti. Jyv\u00e4sj\u00e4rven p\u00e4\u00e4syv\u00e4nteen pohjael\u00e4imist\u00f6n monimuotoisuus v\u00e4heni ja yhteis\u00f6 muuttui surviaiss\u00e4\u00e4ski- ja harvasukasmatovaltaisesta yhteis\u00f6st\u00e4 sulkas\u00e4\u00e4skivaltaiseksi yhteis\u00f6ksi. Vastaava kehitys oli havaittavissa my\u00f6s matalassa Ainolan syv\u00e4nteess\u00e4. P\u00e4\u00e4syv\u00e4nteell\u00e4 pohjael\u00e4inyhteis\u00f6n ekologisen tilan luokitus parani hapetuksen loputtua, mutta havaitut yhteis\u00f6muutokset voivat liitty\u00e4 osin jo aiemmin alkaneeseen Jyv\u00e4sj\u00e4rven pitk\u00e4aikaiseen j\u00e4tevesikuormituksesta toipumiskehitykseen. Tuomioj\u00e4rvess\u00e4 hapetuksen tehostaminen nosti alusveden l\u00e4mp\u00f6tilaa ja happipitoisuutta. Tuomioj\u00e4rven syv\u00e4nnepohjael\u00e4inyhteis\u00f6ss\u00e4 havaitut muutokset olivat pieni\u00e4, mutta k\u00e4\u00e4nteisi\u00e4 Jyv\u00e4sj\u00e4rvest\u00e4 saatujen tulosten kanssa. Tutkimustulosten perusteella Jyv\u00e4sj\u00e4rven hapetuksen pys\u00e4ytt\u00e4minen paransi j\u00e4rven syv\u00e4nnepohjael\u00e4imist\u00f6n ekologista tilaa. Pit\u00e4vi\u00e4 p\u00e4\u00e4telmi\u00e4 voidaan tehd\u00e4 vasta pidemm\u00e4n seurannan tuloksena, mink\u00e4 vuoksi hapetuksen vaikuttavuutta j\u00e4rvien ekologiseen tilaan tulisi tutkia laajemmin.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Several techniques have been developed for water resources management to help lakes recover from anthropogenic pollution and stress. One of the most frequently used techniques is hypolimnetic oxygenation (HLO). HLO aims to control the eutrophication by preventing internal phosphorus loading and in Finland, this is typically done by pumping well-oxygenated surface water to the hypolimnion. As a side effect, this circulation of water warms up the hypolimnion and prevents the natural thermal stratification of the lake. Even though HLO has been a popular technique for more than four decades, there is little independent research on the long-term effects of the practice. In this study, benthic macroinvertebrate assemblages were examined in three small humic lakes (Lake Jyv\u00e4sj\u00e4rvi, Lake Tuomioj\u00e4rvi and Lake Alvaj\u00e4rvi) annually between the years 2000 and 2014, to investigate the effects of HLO on structure and status of communities. In Lake Jyv\u00e4sj\u00e4rvi, oxygenation was the main management technique for 32 years, until in 2012 the oxygenation process was ceased. In Lake Tuomioj\u00e4rvi, the performance of oxygenation was increased in 2012. Lake Alvaj\u00e4rvi represents a reference lake that has never been oxygenated. Data on oxygen and phosphorus concentration and temperature, were collected from the study lakes to serve as background information. The ceasing of the oxygenation in Lake Jyv\u00e4sj\u00e4rvi lowered the hypolimnetic water temperature (by 8.2 C\u00b0) and oxygen concentrations in the main basin. The diversity of benthic macroinvertebrates decreased and the community became dominated by Chaoborus at the expense of chironomids and oligochaetes. Similar effects were detected also in the shallower Ainola basin. Although the ecological state of communities improved after the oxygenation process was ceased, this might be at least partly a continuation of the recovery trend started before the ceasing of the oxygenation process. The concentration of oxygen increased and temperature increased in Lake Tuomioj\u00e4rvi after the oxygenation was enhanced. Changes in the macroinvertebrate community were small but quite consistently reversal to the changes in Lake Jyv\u00e4sj\u00e4rvi. The results suggest that the ceasing of HLO improved the ecological state of macroinvertebrates in Lake Jyv\u00e4sj\u00e4rvi. More extensive research should be conducted on the effects of the oxygenation process to the ecological state of lakes, and more reliable conclusions can only be drawn as a result of long-term monitoring of lakes.", "language": "en", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Inka Vesala (inmivesa) on 2016-04-06 13:40:02.725029. Form: Pro gradu -lomake (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake). 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