Search results for "järvet"
showing 10 items of 116 documents
Impact of increased dissolved organic carbon and nutrient loading on humic lake phytoplankton
2011
Lisääntyneen liuenneen orgaanisen hiilen (DOC) kuormituksen vaikutuksia humusjärven (Alinen Mustajärvi) kasviplanktoniin tutkittiin koko järven manipulaatio -kokeessa 2007–2009. 2007 oli tutkimuksen kontrollivuosi ilman manipulaatiota, 2008–2009 järveen lisättiin kerran kuukaudessa ruokosokeria, ja lisäksi ravinnelisäysten vaikutuksia tutkittiin pussikokeissa kolme kertaa avovesikaudella 2009. Tarkoituksena oli lisätä heterotrofisten bakteerien ravintona käyttämän helposti hajotettavan DOC:in määrää ilman, että se vaikuttaisi kasviplanktonin kokemiin valaisuolosuhteisiin. Autotrofisten ja miksotrofisten levien reaktioita vertailtiin kokeissa keskenään. Kasviplanktonyhteisöissä oli suuria er…
Planktivorous vendace (Coregonus albula) utilise algae-derived fatty acids for biomass increase and lipid deposition
2018
Spatial and seasonal variation in the abundance and composition of phytoplankton and other basal resources (bacteria, terrestrial detritus) influence the availability of essen-tial polyunsaturated fatty acids (PUFA) for upper trophic levels in lake food webs. We studied accumulation, composition and content of fatty acids in planktivorous ven-dace (Coregonus albula) muscle tissue during the summer feeding period (May to late September) in six boreal lakes. Vendace muscle fatty acid content increased from ~17.7 mg/g DW to ~28.1 mg/g DW from spring to summer, corresponding to a ~59% increase in total fatty acids. PUFA accounted for 45%–65% of all fatty acids, and the most abundant fatty acid …
An extended Benthic Quality Index for assessment of lake profundal macroinvertebrates: addition of indicator taxa by multivariate ordination and weig…
2014
The chironomid Benthic Quality Index (BQI) is a widely used metric in assessments of lake status. The BQI is based on 7 indicator taxa, which like most profundal fauna, often occur sporadically in low densities. Hence, a major weakness of the index is that it cannot be calculated when indicator taxa are not captured. Thus, an extension of the BQI that incorporates more macroinvertebrate taxa is desirable. We used 2 statistical approaches (Detrended Correspondence Analysis and Weighted Averaging) to estimate new benthic quality indicator scores for profundal macroinvertebrate taxa and to construct modified BQIs called Profundal Invertebrate Community Metrics (PICMs). We calibrated the PICMs …
Trophic role of marbled crayfish in a lentic freshwater ecosystem
2019
Species’ introductions may cause severe adverse effects on freshwater ecosystems and their biota. The marbled crayfish, Procambarus virginalis Lyko, 2017, is an invasive parthenogenetically reproducing crayfish with rapid reproduction, maturation and tolerance to a wide range of environmental conditions, which was introduced to many sites across Europe during the last decade. Due to its recent speciation and limited number of field studies, the knowledge of trophic interactions of the marbled crayfish in freshwater food webs is scarce. An invaded area located in Central Europe was studied to identify the marbled crayfish food web interactions using analysis of carbon 13 C and nitrogen 15N i…
Vertical stratification of bacteria and archaea in sediments of a small boreal humic lake
2019
A comparison of the impacts of introduced signal crayfish and native noble crayfish in boreal lake ecosystems
2014
Temperature, phosphorus and species composition will all influence phytoplankton production and content of polyunsaturated fatty acids
2023
Temperature increases driven by climate change are expected to decrease the availability of polyunsaturated fatty acids in lakes worldwide. Nevertheless, a comprehensive understanding of the joint effects of lake trophic status, nutrient dynamics and warming on the availability of these biomolecules is lacking. Here, we conducted a laboratory experiment to study how warming (18–23°C) interacts with phosphorus (0.65–2.58 μM) to affect phytoplankton growth and their production of polyunsaturated fatty acids. We included 10 species belonging to the groups diatoms, golden algae, cyanobacteria, green algae, cryptophytes and dinoflagellates. Our results show that both temperature and phosphorus w…
Nitrogen removal by microbial processes in aquatic systems
2012
Biodegradation of microplastic in freshwaters : a long‐lasting process affected by the lake microbiome
2022
Plastics have been produced for over a century, but definitive evidence of complete plastic biodegradation in different habitats, particularly freshwater ecosystems, is still missing. Using 13C-labeled polyethylene microplastics (PE-MP) and stable isotope analysis of produced gas and microbial membrane lipids, we determined the biodegradation rate and fate of carbon in PE-MP in different freshwater types. The biodegradation rate in the humic-lake waters was much higher (0.45±0.21% per year) than in the clear-lake waters (0.07±0.06% per year) or the artificial freshwater medium (0.02±0.02% per year). Complete biodegradation of PE-MP was calculated to last 100-200 years in humic-lake waters, …
Impacts of biomanipulation on lake ecosystem structure revealed by stable isotope analysis
2008
Rehevöityneiden järvien ravintoketjukunnostus epäonnistuu useinJärvien ravintoketjukunnostusta eli biomanipulaatiota on käytetty paljon rehevöityneiden järvien kunnostuksessa. Biomanipulaatiossa pyritään poistamaan järvestä pieniä eläinplanktonia syöviä kalalajeja, lähinnä eri särkikaloja ja pieniä ahvenia, jolloin eläinplanktonin määrä ja yksilökoko kasvavat. Tällöin kasviplanktonia ravintonaan käyttävä eläinplankton pystyy paremmin kontrolloimaan kasviplanktonin määrää järvessä. Biomanipulaation onnistumisen kriteerinä voidaan siis pitää kasviplanktonin määrän vähenemistä ja siitä aiheutuvaa veden kirkastumista. - Varsin suoraviivaisesta teoriasta huolimatta saavutetut tulokset eivät aina…