Search results for "humusjärvet"

Influence of littoral periphyton on whole-lake metabolism relates to littoral vegetation in humic lakes

2017

The role of littoral habitats in lake metabolism has been underrated, especially in humic lakes, based on an assumption of low benthic primary production (PP) due to low light penetration into water. This assumption has been challenged by recent recognition of littoral epiphyton dominance of whole-lake PP in a small highly humic lake and of epiphyton as an important basal food source for humic lake biota. However, as these studies have mostly concerned single lakes, there is a need to test their wider generality. We studied the whole-lake PP and community respiration (CR) in eight small humic lakes in southern Finland during July 2015 using 14 C incorporation to measure pelagic PP and the c…

Vertical stratification of bacteria and archaea in sediments of a small boreal humic lake

2019

ABSTRACT Although sediments of small boreal humic lakes are important carbon stores and greenhouse gas sources, the composition and structuring mechanisms of their microbial communities have remained understudied. We analyzed the vertical profiles of microbial biomass indicators (PLFAs, DNA and RNA) and the bacterial and archaeal community composition (sequencing of 16S rRNA gene amplicons and qPCR of mcrA) in sediment cores collected from a typical small boreal lake. While microbial biomass decreased with sediment depth, viable microbes (RNA and PLFA) were present all through the profiles. The vertical stratification patterns of the bacterial and archaeal communities resembled those in mar…

Calibration of in situ chlorophyll fluorometers for organic matter

2019

AbstractOrganic matter (OM) other than living phytoplankton is known to affect fluorometric in situ assessments of chlorophyll in lakes. For this reason, calibrating fluorometric measurements for OM error is important. In this study, chlorophyll (Chl) fluorescence was measured in situ in multiple Finnish lakes using two sondes equipped with Chl fluorometers (ex.470/em.650–700 nm). OM absorbance (A420) was measured from water samples, and one of the two sondes was also equipped with in situ fluorometer for OM (ex.350/em.430 nm). The sonde with Chl and OM fluorometers was also deployed continuously on an automated water quality monitoring station on Lake Konnevesi. For data from multiple lake…

Vertical stratification of bacteria and archaea in sediments of a small boreal humic lake

2019

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, …

Influence of littoral periphyton on whole-lake metabolism relates to littoral vegetation in humic lakes

2017

The role of littoral habitats in lake metabolism has been underrated, especially in humic lakes, based on an assumption of low benthic primary production (PP) due to low light penetration into water. This assumption has been challenged by recent recognition of littoral epiphyton dominance of whole-lake PP in a small highly humic lake and of epiphyton as an important basal food source for humic lake biota. However, as these studies have mostly concerned single lakes, there is a need to test their wider generality. We studied the whole-lake PP and community respiration (CR) in eight small humic lakes in southern Finland during July 2015 using 14C incorporation to measure pelagic PP and the ch…

Littoral energy pathways in highly humic boreal lakes

2017

Littoral zones in lakes are among the most productive habitats in the world, but have been seriously understudied, as most limnological studies have concerned only pelagic habitats. The likely importance of littoral zones in clear lakes is widely acknowledged, but in contrast their role in dystrophic humic lakes has generally been assumed to be minor. In this thesis, littoral importance in whole-lake metabolism was studied in small and highly humic lakes in Southern Finland, where Lake Mekkojärvi was the principal study lake. Primary production (PP) measurements revealed that littoral periphyton, growing on surrounding aquatic vegetation, can dominate the whole-lake PP, and the highly autot…

Humuksen vaikutus järvien kalayhteisöihin sekä humusjärvien kalayhteisöperusteinen ekologinen luokittelu

2008

Automated water quality monitoring of humic lakes by using the optical properties of water

2016

Automated water quality monitoring (AWQM) is becoming increasingly common in lakes worldwide. The history of AWQM is relatively short and standard calibration procedures for the measured variables are largely yet to be established. The use of optical AWQM sensors, developed in oceanic environments, raises new questions on the diverse effects which humic compounds may have on the automated optical measurements in inlands waters. The focus of this thesis was to characterize the effects of coloured dissolved organic matter (CDOM) on optical in situ measurements of organic matter (OM) and chlorophyll (Chl) in lakes with varying humic content, and to use AWQM data as a part of traditional monito…

Factors affecting the distribution and abundance of the flagellated alga Gonyostomum semen (Ehrenberg) Diesing in Finland

2014

Limalevä Gonyostomum semen (Ehrenberg) Diesing on nykyisin laajalle levinnyt ja runsas siimalevä Pohjoismaiden järvien planktonleväyhteisöissä. Levää esiintyy etenkin humuspitoisissa järvissä ja se voi muodostaa runsaita kukintoja, jotka voivat haitata vedenpuhdistuslaitoksia ja uimareita. Järven pieni koko, tummavetisyys, vähän hapan vesi ja tyypilliset ravinnepitoisuudet ja lajin käyttäytymisen ominaispiirteet ovat olleet selityksinä lajin runsastumiselle. Tässä tutkimuksessa arvioidaan järvien vedenlaatutekijöitä jotka voivat mahdollisesti selittää lajin esiintymistä ja runsastumista Suomessa. Tässä työssä esitetään tyypilliset olosuhteet ja pintavesityyppiluokat kun pintavesinäytteissä …