49 research outputs found
Piilevien aiheuttamat kalanpyydysten likaantumisongelmat - PyhÀjÀrven etelÀosa, Kulovesi ja Roine
Kalanpyydysten likaantuminen on ongelma erÀissÀ sÀÀnnöstellyissÀ reittivesistöissÀ, missÀ se haittaa kalastusta avovesikauden lisÀksi jÀÀpeitteisenÀ aikana. Myös joillain suuremmilla sÀÀnnöstelemÀttömillÀ jÀrvillÀ, esimerkiksi Roineella ilmiön on koettu pahentuneen. Pirkanmaalla talvista kalanpyydysten likaantumista on raportoitu enenevÀssÀ mÀÀrin 1900-luvun lopulta lÀhtien. Kalastajien havaintojen mukaan pÀÀasiallinen syy sÀÀnnöstellyissÀ vesistöissÀ olisi nk. kevÀtkuopan tekoon liittyvÀt juoksutukset, mutta syy-seuraussuhteita ei ole voitu osoittaa aikaisemmissa tutkimuksissa selvÀsti.
TÀssÀ tutkimuksessa kalanpyydysten likaantumista ja sen syitÀ tarkasteltiin kolmella Pirkanmaan jÀrvellÀ: PyhÀjÀrvellÀ, KulovedellÀ ja Roineella. Tutkimus on jatkoa aiemmille Pirkanmaan ympÀristökeskuksen ja Suomen ympÀristökeskuksen toteuttamille likaantumis-selvityksille, jotka on tehty osana alueen keskeisten jÀrvien sÀÀnnöstelyn kehittÀmistÀ. Tutkimuksen ensimmÀisessÀ osiossa kalanpyydysten likaantumista tarkasteltiin kirjanpito-kalastajien merkintöjen avulla. Toisessa osiossa likaantumista tarkasteltiin havaskokeiden tulosten perusteella. Tutkimuksen pÀÀasiallisena tarkoituksena oli lisÀtÀ ymmÀrrystÀ vedenkorkeuden ja virtaaman vaihtelujen merkityksestÀ kalanpyydysten likaantumisessa.
Tutkimuksen tulokset tukevat kalastajien havaintoihin pohjautuvaa lĂ€htöoletusta, ettĂ€ havasten likaantuminen voimistuu kevĂ€tkuoppajuoksutusten aikaan kasvavien virtaamien ja vedenkorkeuden alenemisen seurauksena. Likaantuminen on selvĂ€sti voimakkain PyhĂ€jĂ€rven pÀÀvirtausalueella, KirkkojĂ€rvi-ToutosenselĂ€n ja SĂ€ijĂ€nselĂ€n-SorvanselĂ€n alueella, kun taas pÀÀvirtausalueen ulkopuolella sijaitsevalla HuhtaanselĂ€llĂ€ piilevien aiheuttamaa talvista likaantumisongelmaa ei havaittu. Syksyinen likaantumishaitta ajoittuu samoihin aikoihin syyskierron kanssa, jolloin alle 10â12 °C lĂ€mpötilassa esiintyvĂ€ rihmamainen Aulacoseira islandica -piilevĂ€ oli selvĂ€sti merkittĂ€vin kalanpyydyksiĂ€ likaava tekijĂ€. Syyskierron aikainen piilevien aiheuttama verkkohavasten likaantuminen oli selvĂ€sti havaittavissa paitsi PyhĂ€jĂ€rven pÀÀvirtausalueella sijaitsevilla Aniansaaren ja Salonsaaren alueilla myös Roineella molemmilla havaskoealueilla
Suitability of Phytosterols Alongside Fatty Acids as Chemotaxonomic Biomarkers for Phytoplankton
The composition and abundance of phytoplankton is an important factor defining ecological status of marine and freshwater ecosystems. Chemotaxonomic markers (e.g., pigments and fatty acids) are needed for monitoring changes in a phytoplankton community and to know the nutritional quality of seston for herbivorous zooplankton. Here we investigated the suitability of sterols along with fatty acids as chemotaxonomic markers using multivariate statistics, by analyzing the sterol and fatty acid composition of 10 different phytoplankton classes including altogether 37 strains isolated from freshwater lakes. We were able to detect a total of 47 fatty acids and 29 sterols in our phytoplankton samples, which both differed statistically significantly between phytoplankton classes. Due to the high variation of fatty acid composition among Cyanophyceae, taxonomical differentiation increased when Cyanophyceae were excluded from statistical analysis. Sterol composition was more heterogeneous within class than fatty acids and did not improve separation of phytoplankton classes when used alongside fatty acids. However, we conclude that sterols can provide additional information on the abundance of specific genera within a class which can be generated by using fatty acids. For example, whereas high C-16 omega-3 PUFA (polyunsaturated fatty acid) indicates the presence of Chlorophyceae, a simultaneous high amount of ergosterol could specify the presence of Chlamydomonas spp. (Chlorophyceae). Additionally, we found specific 4 alpha-methyl sterols for distinct Dinophyceae genera, suggesting that 4a-methyl sterols can potentially separate freshwater dinoflagellates from each other.Peer reviewe
Water level regulation in winter triggers fouling of fishing nets by the diatom Aulacoseira islandica in a boreal lake
Water level regulation related to hydroelectric power production and flood prevention
is an important hydro-morphological pressure on many watercourses around the world.
Fouling of fishing nets in autumn during the open water period and in winter under the ice
is a common phenomenon in large Finnish lakes where the water level is regulated. This
fouling of fishing nets can sometimes be so extensive that fishing has to be stopped. Based
on the practical experiences of fishermen, the main cause for the under-ice fouling has
been proposed to be the winter draw-down of water causing low water level and stronger
currents in lakes, but no conclusive relationship between fouling and water level regulation
has yet been demonstrated. Here we show, using long-term winter data from a boreal
lake and short-term netting experiments, that fouling of fishing nets results from increased
water draw-down during winter (JanuaryâMarch). Our results also show that fouling of
fishing nets takes place only if the high water flow rates are accompanied by an intensive
lowering of the water level. We also discuss the relevance of our results to other regulated
lakes with ice cover.peerReviewe
Development of phytoplankton of Lake Vesijarvi during recovery from eutrophication
Wastewaters discharged to Lake Vesijarvi ruined its recreational value and demanded mitigation measures. In the mid-1970s, the diversion of wastewaters elsewhere reduced epilimnetic total phosphorus concentration by similar to 40% from > 100 mg P m(-3) in 5 years, but this was not enough to eliminate cyanobacterial blooms. In 1979-1984, hypolimnetic oxygenation was applied to decrease internal nutrient loading, but pumping warm surface water to the hypolimnion probably intensified gas ebullition from the sediment, carrying nutrients to the epilimnion and intensifying cyanobacterial blooms. Intensive fish removal in 1989-1994 was more successful. Five years of summer trawling removed over three-quarters of roach and smelt stock, and after the two most intensive fishing years, TP and chlorophyll concentrations abruptly decreased by similar to 35%. During subsequent years fish removal continued at similar to 30% intensity and maintained chlorophyll and total nutrient concentrations at a lower level until the end of the study. At the same time, the frequency of cyanobacterial blooms decreased from annual to twice per decade. Larger-scale oxygenation after 2010 no longer resulted in ebullition, and its effect on phytoplankton was indistinguishable from natural variability. Consequently, it was abandoned. The intensity of fish removal needed to maintain the present status of the lake is still awaiting evaluation.Peer reviewe
Eutrophication reduces the nutritional value of phytoplankton in boreal lakes
Eutrophication (as an increase in total phosphorus [TP]) increases harmful algal blooms and reduces the proportion of high-quality phytoplankton in seston and the content of Ï-3 long-chain polyunsaturated fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) in fish. However, it is not well-known how eutrophication affects the overall nutritional value of phytoplankton. Therefore, we studied the impact of eutrophication on the production (as concentration; ÎŒg Lâ1) and content (ÎŒg mg Câ1) of amino acids, EPA, DHA, and sterols, i.e., the nutritional value of phytoplankton in 107 boreal lakes. The lakes were categorized in seven TP concentration categories ranging from ultra-oligotrophic (50âŻÎŒgâŻLâ1). Phytoplankton total biomass increased with TP as expected, but in contrast to previous studies, the contribution of high-quality phytoplankton did not decrease with TP. However, the high variation reflected instability in the phytoplankton community structure in eutrophic lakes. We found that the concentration of amino acids increased in the epilimnion whereas the concentration of sterols decreased with increasing TP. In terms of phytoplankton nutritional value, amino acids, EPA, DHA, and sterols showed a significant quadratic relationship with the lake trophic status. More specifically, the amino acid contents were the same in the oligo- and mesotrophic lakes, but substantially lower in the eutrophic lakes (TPâŻ>âŻ35âŻÎŒgâŻLâ1/1.13âŻÎŒmolâŻLâ1). The highest EPA and DHA content in phytoplankton was found in the mesotrophic lakes, whereas the sterol content was highest in the oligotrophic lakes. Based on these results, the nutritional value of phytoplankton reduces with eutrophication, although the contribution of high-quality algae does not decrease. Therefore, the results emphasize that eutrophication, as excess TP, reduces the nutritional value of phytoplankton, which may have a significant impact on the nutritional value of zooplankton, fish, and other aquatic animals at higher food web levels.peerReviewe
Kasviplanktonanalyysin laadunvarmistus
Biologisten mÀÀritysten laadunvarmennuksen merkitys on korostunut EU:n vesipuitedirektiivin (VPD) voimaantulon myötÀ, sillÀ vesistöjen ekologisen tilan luokittelu edellyttÀÀ, ettÀ kÀytössÀ on laadukasta ja vertailukelpoista tietoa biologisista laatutekijöistÀ.
Suomen ympÀristökeskus SYKE on toiminut vuodesta 2001 kansallisena ympÀristöalan vertailulaboratoriona pÀtevyysalueena vesien ja kiinteiden ympÀristönÀytteiden ympÀristökemiallinen ja ekotoksikologinen mittaus-, testaus- ja nÀytteenottotoiminta. SYKEssÀ alkoi vuonna 2005 hanke vertailulaboratorion pÀtevyysalueen laajentamiseksi kolmella biologisella laatutekijÀllÀ, kasviplankton, vesikasvit ja pohjaelÀimet.
TÀmÀ julkaisu sisÀltÀÀ kasviplanktonin laadunvarmistusta koskevan osahankkeen kuvauksen ja tulokset sekÀ suositukset laadunvarmistustoimenpiteiksi. Raportissa tarkastellaan kasviplanktonanalyysin toteutusta Suomessa ja muualla Euroopassa. Tarkastelun painopisteenÀ ovat tulosten vertailtavuus ja siihen vaikuttavat tekijÀt sekÀ SYKEn sisÀ- ja rannikkovesien kasviplanktonanalyysin nykytila, valmiudet ja kehittÀmislinjat. Raportissa linjataan SYKEn rooli sisÀ- ja rannikkovesien kasviplanktonmÀÀrityksen kansallisessa ja kansainvÀlisessÀ laadunvarmennuksessa osana vertailulaboratoriotoimintaa.
Kasviplanktonin analysointi edellyttÀÀ hyvÀÀ lajintuntemusta, yhtenÀisten ja hyvÀksyttyjen analyysimenetelmien kÀyttöÀ sekÀ kykyÀ tulkita saatuja tuloksia. KasviplanktonmÀÀrityksiÀ tehdÀÀn Suomessa viranomaisten lisÀksi konsulttityönÀ sekÀ tutkimushankkeissa. On myös todennÀköistÀ, ettÀ biologinen analyysitoiminta laajenee jatkossa useamman toimijan piiriin. VPD:n toteutuksen kannalta on tÀrkeÀÀ, ettÀ kasviplanktonin mÀÀritystulokset ovat mahdollisimman laajasti hyödynnettÀvissÀ ekologisen tilan luokittelussa. TÀmÀ asettaa vaatimuksia tulosten keskinÀiselle vertailtavuudelle ja laadulle ja edellyttÀÀ sÀÀnnöllistÀ mÀÀritystulosten testaamista ja vertailua toimijoiden kesken. Suomalaiset kasviplanktontutkijat ovat olleet edellÀkÀvijöitÀ laadunvarmistuksessa verkostoitumalla ja kokoontumalla vuosittain työseminaareihin, joissa on kÀsitelty menetelmien harmonisointia ja vertailtavuutta. Vertailulaboratoriotoiminnan tarkoituksena on vahvistaa ja koordinoida toteutettua laadunvarmennusta ja saada mahdollisimman moni kasviplanktonmÀÀrityksiÀ tekevÀ mukaan toiminnan piiriin
Lake zooplankton delta C-13 values are strongly correlated with the delta C-13 values of distinct phytoplankton taxa
Analyses of carbon stable isotopes are often used to estimate the contributions of allochthonous and autochthonous dietary resources to aquatic consumers. Most pelagic food web studies assume that all phytoplankton taxa have a similar delta C-13 value. We studied pelagic food web compartments (dissolved inorganic carbon [DIC], phytoplankton, bacteria, seston, cladoceran zooplankton) in 12 small (<0.1 km(2)) lakes in southern Finland. These lakes were classified as oligotrophic, mesotrophic, eutrophic, and dystrophic based on their concentrations of total phosphorus and dissolved organic carbon. Additionally, we studied phytoplankton photosynthetic carbon fractionation (epsilon(p)) in laboratory conditions. The photosynthetic fractionation in 28 phytoplankton cultures from nine different phytoplankton classes varied significantly at the class level, and fractionation correlated significantly with the DIC concentration of the growth media. In small boreal lakes, the delta C-13 values of different phytoplankton taxa, as directly measured or estimated from the delta C-13 values of biomarker fatty acids, varied greatly (-18 parts per thousand to - 44.5 parts per thousand). Phytoplankton delta C-13 values varied significantly by lake type and were most depleted in dystrophic lakes even though the delta C-13 values of the DIC was similar to mesotrophic lakes. Further within-taxa variation was found between lakes and between different depths within a lake. Vertical samples from dystrophic lakes also showed lower ep in the phytoplankton from meta-and hypolimnion, possibly as a result of reduced light intensity. Altogether, in nine of the 10 sampled lakes, the delta C-13 values of cladoceran zooplankton were between the minimum and the maximum phytoplankton delta C-13 value of each lake, and thus, phytoplankton alone could explain zooplankton delta C-13 values. We conclude that stable isotope mixing models should take into account carbon variation among different phytoplankton taxa.Peer reviewe