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Phytoplankton and Physical Disturbance: Seasonal dynamics in temperate Lake Erken, Sweden
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. (Erken Laboratory)ORCID iD: 0000-0002-8935-9583
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Phytoplankton mirrors changes in the environment and plays an important role in biogeochemical processes. Phytoplankton dynamics is the outcome of both autogenic succession and external disturbances. This thesis focused on the seasonal variation of water column stability and its effects on phytoplankton, particularly considering the influence of mixing events on phytoplankton development. Lake Erken is a dimictic lake with weak and often interrupted summer stratification, which represents an intermediate case between a polymictic lake and a lake with strong summer stratification.

There are two diatom phases annually. The spring bloom is caused by pioneer centric diatoms, and the autumn diatom phase is dominated by meroplanktonic diatoms induced by turnover. A summer Cyanobacteria bloom – mainly Gloeotrichia echinulata, depended on the length and stability of stratification.

Winter and spring air temperature is found to play an important role in the annual succession of phytoplankton by initiating changes in ice/snow-cover and lake thermal stability and setting the basic status. Instead of starting from zero, the vernal phytoplankton piles up on the overwintering community, this trans-annual ecological memory influences both the composition and diversity and taxonomic distinctness of spring phytoplankton.

Water column stability during summer in Lake Erken is mainly influenced by wind-induced turbulence and internal seiches. As thermal stratification develops from early until late summer, variations in stability and gradual deepening of the thermocline depth influence phytoplankton dynamics directly by changing its distribution, and also indirectly by altering the nutrient and light availability. A new disturbance index (DI) was defined to quantify environmental stability/disturbance and tested well to indicate phytoplankton equilibrium status in two summer stratification periods. The concept of species and functional groups was generally used in this study. However, a next generation sequencing based approach was also tested and proved to provide an excellent candidate for revealing distribution patterns of phytoplankton in inland waters.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 43 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1292
Keyword [en]
Phytoplankton dynamics, high-frequency measurements, thermal stratification, water column stability, equilibrium, disturbance
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-262461ISBN: 978-91-554-9345-5 (print)OAI: oai:DiVA.org:uu-262461DiVA: diva2:853856
Public defence
2015-11-06, Friessalen, Evolutionary Biology Center, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2015-10-09 Created: 2015-09-15 Last updated: 2015-10-29
List of papers
1. Unveiling Distribution Patterns of Freshwater Phytoplankton by a Next Generation Sequencing Based Approach
Open this publication in new window or tab >>Unveiling Distribution Patterns of Freshwater Phytoplankton by a Next Generation Sequencing Based Approach
Show others...
2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 1, e53516- p.Article in journal (Refereed) Published
Abstract [en]

The recognition and discrimination of phytoplankton species is one of the foundations of freshwater biodiversity research and environmental monitoring. This step is frequently a bottleneck in the analytical chain from sampling to data analysis and subsequent environmental status evaluation. Here we present phytoplankton diversity data from 49 lakes including three seasonal surveys assessed by next generation sequencing (NGS) of 16S ribosomal RNA chloroplast and cyanobacterial gene amplicons and also compare part of these datasets with identification based on morphology. Direct comparison of NGS to microscopic data from three time-series showed that NGS was able to capture the seasonality in phytoplankton succession as observed by microscopy. Still, the PCR-based approach was only semi-quantitative, and detailed NGS and microscopy taxa lists had only low taxonomic correspondence. This is probably due to, both, methodological constraints and current discrepancies in taxonomic frameworks. Discrepancies included Euglenophyta and Heterokonta that were scarce in the NGS but frequently detected by microscopy and Cyanobacteria that were in general more abundant and classified with high resolution by NGS. A deep-branching taxonomically unclassified cluster was frequently detected by NGS but could not be linked to any group identified by microscopy. NGS derived phytoplankton composition differed significantly among lakes with different trophic status, showing that our approach can resolve phytoplankton communities at a level relevant for ecosystem management. The high reproducibility and potential for standardization and parallelization makes our NGS approach an excellent candidate for simultaneous monitoring of prokaryotic and eukaryotic phytoplankton in inland waters.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-194906 (URN)10.1371/journal.pone.0053516 (DOI)000314019100023 ()
Available from: 2013-02-20 Created: 2013-02-19 Last updated: 2017-12-06Bibliographically approved
2. Repetitive baselines of phytoplankton succession in an unstably stratified temperate lake (Lake Erken, Sweden): a long-term analysis
Open this publication in new window or tab >>Repetitive baselines of phytoplankton succession in an unstably stratified temperate lake (Lake Erken, Sweden): a long-term analysis
2016 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 764, no 1, 211-227 p.Article in journal (Refereed) Published
Abstract [en]

The seasonal development of phytoplankton is a sequence of consecutive events with waxes and wanes of biomass and compositional shifts. This study analyzed 16 years data in Lake Erken, Sweden and revealed four baselines of phytoplankton succession with their underlying drivers. Results showed that there were two diatom-dominated phases annually. The vernal community was dominated by centric diatoms larger than 15 A mu m (functional groups B and C) which were fast-growing diatoms being highly efficient in the use of nutrients. The autumn community was comprised mainly meroplanktonic mixing-dependent Aulacoseira granulata and Fragilaria sp. (MP and P) or/and large centric diatoms (B). Between the two mixing-phases with diatoms, a Gloeotrichia echinulata (H 2) bloom occurred due to its preference for a stratified water column with elevated water temperatures and high light availability. The summer stratification in Lake Erken was weak and short, thus, favoring meroplanktonic diatoms to peak once the lake turned over in early autumn. Lake Erken represents an intermediate case between a highly mixed polymictic lake and a lake with strong summer stratification, where the observed stratification patterns allowed the development of an autumn diatom phase similar, by extent, to the vernal one and mainly dominated by meroplanktonic diatoms.

National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-262459 (URN)10.1007/s10750-015-2314-1 (DOI)000365727500017 ()
Available from: 2015-09-15 Created: 2015-09-15 Last updated: 2017-12-04Bibliographically approved
3. Water column stability and summer phytoplankton dynamics in a temperate lake (Lake Erken, Sweden)
Open this publication in new window or tab >>Water column stability and summer phytoplankton dynamics in a temperate lake (Lake Erken, Sweden)
2016 (English)In: INLAND WATERS, ISSN 2044-2041, E-ISSN 2044-205X, Vol. 6, no 4, 499-508 p.Article in journal (Refereed) Published
Abstract [en]

Phytoplankton development in aquatic ecosystems is caused by interactions among multiple environmental factors. Physical processes, particularly development of thermal stratification, have been proposed to be important factors for regulating phytoplankton composition and abundance during summer. This study examined the temporal pattern of thermal stratification during summer in Lake Erken, Sweden, based on 21 years of historical data spanning 23 years and investigated the role played by water stability on phytoplankton development. Water column stability indexes were calculated from high frequency measurements during periods of summer thermal stratification. Clustering and ordination analyzed the dissimilarities between communities during different periods and extracted the significant environmental gradients controlling phytoplankton succession. Wind introduced the major external disturbance to Lake Erken during summer and played an important role for the progression of thermocline depth. Species-specific thermal stability preference or tolerance determined the response of individual species to the stratification and constitutes a mechanism of species selection in phytoplankton dynamics. Lake Erken is an unstably stratified lake during summer, caused by wind-induced turbulence and internal seiches. Adaptation to these unstable conditions is the major determinant of phytoplankton dynamics. Hydrodynamic variability, characterized by different stability indexes in early, mid, and late summer, was the key factor regulating phytoplankton dynamics, directly by changing phytoplankton distribution and indirectly by altering both the light and nutrient availability in the epilimnion.

Keyword
Gloeotrichia echinulata, hydrodynamics, Lake Analyzer, phytoplankton dynamics, succession, thermal stratification and mixing
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-262451 (URN)10.5268/IW-6.4.874 (DOI)000388608700003 ()
Available from: 2015-09-15 Created: 2015-09-15 Last updated: 2017-12-04Bibliographically approved
4. Development of a disturbance index based on high frequency temperature measurements and its test on phytoplankton assemblage equilibrium during summer stratification in Lake Erken
Open this publication in new window or tab >>Development of a disturbance index based on high frequency temperature measurements and its test on phytoplankton assemblage equilibrium during summer stratification in Lake Erken
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-262454 (URN)
Available from: 2015-09-15 Created: 2015-09-15 Last updated: 2015-10-12
5. Effects of physical factors on spring phytoplankton in a temperate lake (Lake Erken, Sweden)
Open this publication in new window or tab >>Effects of physical factors on spring phytoplankton in a temperate lake (Lake Erken, Sweden)
(English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117Article in journal (Other academic) Submitted
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-262455 (URN)
Available from: 2015-09-15 Created: 2015-09-15 Last updated: 2017-12-04

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