Publications by authors named "Sanni L Aalto"

16 Publications

  • Page 1 of 1

Microbial communities in full-scale woodchip bioreactors treating aquaculture effluents.

J Environ Manage 2022 Jan 27;301:113852. Epub 2021 Sep 27.

Technical University of Denmark, DTU Aqua, Section for Aquaculture, The North Sea Research Centre, P.O. Box 101, DK-9850, Hirtshals, Denmark.

Woodchip bioreactors are being successfully applied to remove nitrate from commercial land-based recirculating aquaculture system (RAS) effluents. In order to understand and optimize the overall function of these bioreactors, knowledge on the microbial communities, especially on the microbes with potential for production or mitigation of harmful substances (e.g. hydrogen sulfide; HS) is needed. In this study, we quantified and characterized bacterial and fungal communities, including potential HS producers and consumers, using qPCR and high throughput sequencing of 16S rRNA gene. We took water samples from bioreactors and their inlet and outlet, and sampled biofilms growing on woodchips and on the outlet of the three full-scale woodchip bioreactors treating effluents of three individual RAS. We found that bioreactors hosted a high biomass of both bacteria and fungi. Although the composition of microbial communities of the inlet varied between the bioreactors, the conditions in the bioreactors selected for the same core microbial taxa. The HS producing sulfate reducing bacteria (SRB) were mainly found in the nitrate-limited outlets of the bioreactors, the main groups being deltaproteobacterial Desulfobulbus and Desulfovibrio. The abundance of HS consuming sulfate oxidizing bacteria (SOB) was 5-10 times higher than that of SRB, and SOB communities were dominated by Arcobacter and other genera from phylum Epsilonbacteraeota, which are also capable of autotrophic denitrification. Indeed, the relative abundance of potential autotrophic denitrifiers of all denitrifier sequences was even 54% in outlet water samples and 56% in the outlet biofilm samples. Altogether, our results show that the highly abundant bacterial and fungal communities in woodchip bioreactors are shaped through the conditions prevailing within the bioreactor, indicating that the bioreactors with similar design and operational settings should provide similar function even when conditions in the preceding RAS would differ. Furthermore, autotrophic denitrifiers can have a significant role in woodchip biofilters, consuming potentially produced HS and removing nitrate, lengthening the operational age and thus further improving the overall environmental benefit of these bioreactors.
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http://dx.doi.org/10.1016/j.jenvman.2021.113852DOI Listing
January 2022

Vertical stratification patterns of methanotrophs and their genetic controllers in water columns of oxygen-stratified boreal lakes.

FEMS Microbiol Ecol 2021 01;97(2)

Department of Environmental and Biological Sciences, University of Eastern Finland, Yliopistonranta 1 E, FI-70210, Kuopio, Finland.

The vertical structuring of methanotrophic communities and its genetic controllers remain understudied in the water columns of oxygen-stratified lakes. Therefore, we used 16S rRNA gene sequencing to study the vertical stratification patterns of methanotrophs in two boreal lakes, Lake Kuivajärvi and Lake Lovojärvi. Furthermore, metagenomic analyses were performed to assess the genomic characteristics of methanotrophs in Lovojärvi and the previously studied Lake Alinen Mustajärvi. The methanotroph communities were vertically structured along the oxygen gradient. Alphaproteobacterial methanotrophs preferred oxic water layers, while Methylococcales methanotrophs, consisting of putative novel genera and species, thrived, especially at and below the oxic-anoxic interface and showed distinct depth variation patterns, which were not completely predictable by their taxonomic classification. Instead, genomic differences among Methylococcales methanotrophs explained their variable vertical depth patterns. Genes in clusters of orthologous groups (COG) categories L (replication, recombination and repair) and S (function unknown) were relatively high in metagenome-assembled genomes representing Methylococcales clearly thriving below the oxic-anoxic interface, suggesting genetic adaptations for increased stress tolerance enabling living in the hypoxic/anoxic conditions. By contrast, genes in COG category N (cell motility) were relatively high in metagenome-assembled genomes of Methylococcales thriving at the oxic-anoxic interface, which suggests genetic adaptations for increased motility at the vertically fluctuating oxic-anoxic interface.
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http://dx.doi.org/10.1093/femsec/fiaa252DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840105PMC
January 2021

Hurricane Disturbance Stimulated Nitrification and Altered Ammonia Oxidizer Community Structure in Lake Okeechobee and St. Lucie Estuary (Florida).

Front Microbiol 2020 10;11:1541. Epub 2020 Jul 10.

Department of Earth and Environmental Sciences, Wright State University, Dayton, OH, United States.

Nitrification is an important biological link between oxidized and reduced forms of nitrogen (N). The efficiency of nitrification plays a key role in mitigating excess N in eutrophic systems, including those with cyanobacterial harmful algal blooms (cyanoHABs), since it can be closely coupled with denitrification and removal of excess N. Recent work suggests that competition for ammonium (NH ) between ammonia oxidizers and cyanoHABs can help determine microbial community structure. Nitrification rates and ammonia-oxidizing archaeal (AOA) and bacterial (AOB) community composition and gene abundances were quantified in Lake Okeechobee and St. Lucie Estuary in southern Florida (United States). We sampled during cyanobacterial () blooms in July 2016 and August 2017 (2 weeks before Hurricane Irma) and 10 days after Hurricane Irma made landfall. Nitrification rates were low during cyanobacterial blooms in Lake Okeechobee and St. Lucie Estuary, while low bloom conditions in St. Lucie Estuary coincided with greater nitrification rates. Nitrification rates in the lake were correlated ( = 0.94; = 0.006) with AOA abundance. Following the hurricane, nitrification rates increased by an order of magnitude, suggesting that nitrifiers outcompeted cyanobacteria for NH under turbid, poor light conditions. After Irma, AOA and AOB abundances increased in St. Lucie Estuary, while only AOB increased in Lake Okeechobee. AOA sequences clustered into three major lineages: (NP), (NS), and (NT). Many of the lake OTUs placed within the uncultured and uncharacterized NS δ and NT β clades, suggesting that these taxa are ecologically important along this eutrophic, lacustrine to estuarine continuum. After the hurricane, the AOA community shifted toward dominance by freshwater clades in St. Lucie Estuary and terrestrial genera in Lake Okeechobee, likely due to high rainfall and subsequent increased turbidity and freshwater loading from the lake into the estuary. AOB community structure was not affected by the disturbance. AOA communities were consistently more diverse than AOB, despite fewer sequences recovered, including new, unclassified, eutrophic ecotypes, suggesting a wider ecological biogeography than the oligotrophic niche originally posited. These results and other recent reports contradict the early hypothesis that AOB dominate ammonia oxidation in high-nutrient or terrestrial-influenced systems.
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http://dx.doi.org/10.3389/fmicb.2020.01541DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7366250PMC
July 2020

CH oxidation in a boreal lake during the development of hypolimnetic hypoxia.

Aquat Sci 2020 28;82(2):19. Epub 2019 Dec 28.

1Department of Environmental and Biological Sciences, University of Eastern Finland, Yliopistonranta 1 E, 70210 Kuopio, Finland.

Freshwater ecosystems represent a significant natural source of methane (CH). CH produced through anaerobic decomposition of organic matter (OM) in lake sediment and water column can be either oxidized to carbon dioxide (CO) by methanotrophic microbes or emitted to the atmosphere. While the role of CH oxidation as a CH sink is widely accepted, neither the magnitude nor the drivers behind CH oxidation are well constrained. In this study, we aimed to gain more specific insight into CH oxidation in the water column of a seasonally stratified, typical boreal lake, particularly under hypoxic conditions. We used CH incubations to determine the active CH oxidation sites and the potential CH oxidation rates in the water column, and we measured environmental variables that could explain CH oxidation in the water column. During hypolimnetic hypoxia, 91% of available CH was oxidized in the active CH oxidation zone, where the potential CH oxidation rates gradually increased from the oxycline to the hypolimnion. Our results showed that in warm springs, which become more frequent, early thermal stratification with cold well-oxygenated hypolimnion delays the period of hypolimnetic hypoxia and limits CH production. Thus, the delayed development of hypolimnetic hypoxia may partially counteract the expected increase in the lacustrine CH emissions caused by the increasing organic carbon load from forested catchments.
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http://dx.doi.org/10.1007/s00027-019-0690-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7181431PMC
December 2019

Nitrate removal microbiology in woodchip bioreactors: A case-study with full-scale bioreactors treating aquaculture effluents.

Sci Total Environ 2020 Jun 21;723:138093. Epub 2020 Mar 21.

Department of Biological and Environmental Science, Nanoscience Center, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland.

Woodchip bioreactors are viable low-cost nitrate (NO) removal applications for treating agricultural and aquaculture discharges. The active microbial biofilms growing on woodchips are conducting nitrogen (N) removal, reducing NO while oxidizing the carbon (C) from woodchips. However, bioreactor age, and changes in the operating conditions or in the microbial community might affect the NO removal as well as potentially promote nitrous oxide (NO) production through either incomplete denitrification or dissimilatory NO reduction to ammonium (DNRA). Here, we combined stable isotope approach, amplicon sequencing, and captured metagenomics for studying the potential NO removal rates, and the abundance and community composition of microbes involved in N transformation processes in the three different full-scale woodchip bioreactors treating recirculating aquaculture system (RAS) effluents. We confirmed denitrification producing di‑nitrogen gas (N) to be the primary NO removal pathway, but found that 6% of NO could be released as NO under high NO concentrations and low amounts of bioavailable C, whereas DNRA rates tend to increase with the C amount. The abundance of denitrifiers was equally high between the studied bioreactors, yet the potential NO removal rates were linked to the denitrifying community diversity. The same core proteobacterial groups were driving the denitrification, while Bacteroidetes dominated the DNRA carrying microbes in all the three bioreactors studied. Altogether, our results suggest that woodchip bioreactors have a high genetic potential for NO removal through a highly abundant and diverse denitrifying community, but that the rates and dynamics between the NO removal pathways depend on the other factors (e.g., bioreactor design, operating conditions, and the amount of bioavailable C in relation to the incoming NO concentrations).
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http://dx.doi.org/10.1016/j.scitotenv.2020.138093DOI Listing
June 2020

Consistency of Targeted Metatranscriptomics and Morphological Characterization of Phytoplankton Communities.

Front Microbiol 2020 6;11:96. Epub 2020 Feb 6.

Department of Biological and Environmental Sciences, Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland.

The composition of phytoplankton community is the basis for environmental monitoring and assessment of the ecological status of aquatic ecosystems. Community composition studies of phytoplankton have been based on time-consuming and expertise-demanding light microscopy analyses. Molecular methods have the potential to replace microscopy, but the high copy number variation of ribosomal genes and the lack of universal primers for simultaneous amplification of prokaryotic and eukaryotic genes complicate data interpretation. In this study, we used our previously developed directional primer-independent high-throughput sequencing (HTS) approach to analyze 16S and 18S rRNA community structures. Comparison of 83 boreal lake samples showed that the relative abundances of eukaryotic phytoplankton at class level and prokaryotic cyanobacteria at order level were consistent between HTS and microscopy results. At the genus level, the results had low correspondence, mainly due to lack of sequences in the reference library. HTS was superior to identify genera that are extensively represented in the reference databases but lack specific morphological characteristics. Targeted metatranscriptomics proved to be a feasible method to complement the microscopy analysis. The metatranscriptomics can also be applied without linking the sequences to taxonomy. However, direct indexing of the sequences to their environmental indicator values needs collections of more comprehensive sample sets, as long as the coverage of molecular barcodes of eukaryotic species remains insufficient.
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http://dx.doi.org/10.3389/fmicb.2020.00096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7016081PMC
February 2020

Eutrophication reduces the nutritional value of phytoplankton in boreal lakes.

Environ Res 2019 12 29;179(Pt B):108836. Epub 2019 Oct 29.

Department of Biological and Environmental Science, Nanoscience Center, University of Jyväskylä, P.O. Box 35 (YA), 40014, Jyväskylä, Finland. Electronic address:

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 ω-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; μg L) and content (μg mg C) 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 (<5 μg L) to highly eutrophic (>50 μg L). 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 (TP > 35 μg L/1.13 μmol L). 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.
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http://dx.doi.org/10.1016/j.envres.2019.108836DOI Listing
December 2019

High Nitrogen Removal in a Constructed Wetland Receiving Treated Wastewater in a Cold Climate.

Environ Sci Technol 2018 11 5;52(22):13343-13350. Epub 2018 Nov 5.

University of Helsinki , Faculty of Biological and Environmental Sciences, Ecosystems and Environment Research Programme , Lammi Biological Station, Pääjärventie 320 , Lammi FI-16900 , Finland.

Constructed wetlands provide cost-efficient nutrient removal, with minimal input of human labor and energy, and their number is globally increasing. However, in northern latitudes, wetlands are rarely utilized, because their nutrient removal efficiency has been questioned due to the cold climate. Here, we studied nutrient retention and nitrogen removal in a boreal constructed wetland (4-ha) receiving treated nitrogen-rich wastewater. On a yearly basis, most of the inorganic nutrients were retained by the wetland. The highest retention efficiency was found during the ice-free period, being 79% for ammonium-nitrogen (NH-N), 71% for nitrate-nitrogen (NO-N), and 88% for phosphate-phosphorus (PO-P). Wetland also acted as a buffer zone during the disturbed nitrification process of the wastewater treatment plant. Denitrification varied between 106 and 252 mg N m d during the ice-free period. During the ice-cover period, total gaseous nitrogen removal was 147 mg N m d, from which 66% was removed as N, 28.5% as NO through denitrification, and 5.5% as N through anammox. Nearly 2600 kg N y was estimated to be removed through microbial gaseous N-production which equaled 72% of NO-N and 60% of TN yearly retention in the wetland. The wetland retained nutrients even in winter, when good oxygen conditions prevailed under ice. The results suggest that constructed wetlands are an efficient option for wastewater nitrogen removal and nutrient retention also in cold climates.
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http://dx.doi.org/10.1021/acs.est.8b03032DOI Listing
November 2018

Novel Autotrophic Organisms Contribute Significantly to the Internal Carbon Cycling Potential of a Boreal Lake.

mBio 2018 08 14;9(4). Epub 2018 Aug 14.

Department of Ecology and Evolution, Limnology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.

Oxygen-stratified lakes are typical for the boreal zone and also a major source of greenhouse gas emissions in the region. Due to shallow light penetration, restricting the growth of phototrophic organisms, and large allochthonous organic carbon inputs from the catchment area, the lake metabolism is expected to be dominated by heterotrophic organisms. In this study, we test this assumption and show that the potential for autotrophic carbon fixation and internal carbon cycling is high throughout the water column. Further, we show that during the summer stratification carbon fixation can exceed respiration in a boreal lake even below the euphotic zone. Metagenome-assembled genomes and 16S profiling of a vertical transect of the lake revealed multiple organisms in an oxygen-depleted compartment belonging to novel or poorly characterized phyla. Many of these organisms were chemolithotrophic, potentially deriving their energy from reactions related to sulfur, iron, and nitrogen transformations. The community, as well as the functions, was stratified along the redox gradient. The autotrophic potential in the lake metagenome below the oxygenic zone was high, pointing toward a need for revising our concepts of internal carbon cycling in boreal lakes. Further, the importance of chemolithoautotrophy for the internal carbon cycling suggests that many predicted climate change-associated fluctuations in the physical properties of the lake, such as altered mixing patterns, likely have consequences for the whole-lake metabolism even beyond the impact to the phototrophic community. Autotrophic organisms at the base of the food web are the only life form capable of turning inorganic carbon into the organic form, facilitating the survival of all other organisms. In certain environments, the autotrophic production is limited by environmental conditions and the food web is supported by external carbon inputs. One such environment is stratified boreal lakes, which are one of the biggest natural sources of greenhouse gas emissions in the boreal region. Thus, carbon cycling in these habitats is of utmost importance for the future climate. Here, we demonstrate a high potential for internal carbon cycling via phototrophic and novel chemolithotrophic organisms in the anoxic, poorly illuminated layers of a boreal lake. Our results significantly increase our knowledge on the microbial communities and their metabolic potential in oxygen-depleted freshwaters and help to understand and predict how climate change-induced alterations could impact the lake carbon dynamics.
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http://dx.doi.org/10.1128/mBio.00916-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6094481PMC
August 2018

Resistant ammonia-oxidizing archaea endure, but adapting ammonia-oxidizing bacteria thrive in boreal lake sediments receiving nutrient-rich effluents.

Environ Microbiol 2018 10 9;20(10):3616-3628. Epub 2018 Sep 9.

Department of Biological and Environmental Science, University of Jyväskylä, 40014, Jyväskylä, Finland.

Climate change along with anthropogenic activities changes biogeochemical conditions in lake ecosystems, modifying the sediment microbial communities. Wastewater effluents introduce nutrients and organic material but also novel microbes to lake ecosystems, simulating forthcoming increases in catchment loadings. In this work, we first used 16s rRNA gene sequencing to study how the overall sediment microbial community responds to wastewater in six boreal lakes. To examine forthcoming changes in the lake biogeochemistry, we focused on the ammonia-oxidizing archaea (AOA) and bacteria (AOB), and examined their functional and compositional community response to wastewater. Although we found the least diverse and least resistant prokaryotic communities from the most wastewater-influenced sediments, the community changed fast toward the natural composition with the diminishing influence of wastewater. Each lake hosted a unique resistant AOA community, while AOB communities were adapting, responding to environmental conditions as well as receiving new members from WWTPs. In general, AOB dominated in numbers in wastewater-influenced sediments, while the ratio between AOA and AOB increased when moving toward pristine conditions. Our results suggest that although future climate-change-driven increases in nutrient loading and microbial migration might significantly disrupt lake sediment microbiomes, they can promote nitrification through adapting and abundant AOB communities.
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http://dx.doi.org/10.1111/1462-2920.14354DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221106PMC
October 2018

The influence of oxygen and methane on nitrogen fixation in subarctic Sphagnum mosses.

AMB Express 2018 May 5;8(1):76. Epub 2018 May 5.

Department of Microbiology, Radboud University, Nijmegen, The Netherlands.

Biological nitrogen fixation is an important source of bioavailable nitrogen in Sphagnum dominated peatlands. Sphagnum mosses harbor a diverse microbiome including nitrogen-fixing and methane (CH) oxidizing bacteria. The inhibitory effect of oxygen on microbial nitrogen fixation is documented for many bacteria. However, the role of nitrogen-fixing methanotrophs in nitrogen supply to Sphagnum peat mosses is not well explored. Here, we investigated the role of both oxygen and methane on nitrogen fixation in subarctic Sphagnum peat mosses. Five species of Sphagnum mosses were sampled from two mesotrophic and three oligotrophic sites within the Lakkasuo peatland in Orivesi, central Finland. Mosses were incubated under either ambient or low oxygen conditions in the presence or absence of methane. Stable isotope activity assays revealed considerable nitrogen-fixing and methane-assimilating rates at all sites (1.4 ± 0.2 µmol N-N g DW day and 12.0 ± 1.1 µmol C-CH g DW day, respectively). Addition of methane did not stimulate incorporation of N-nitrogen into biomass, whereas oxygen depletion increased the activity of the nitrogen-fixing community. Analysis of the 16S rRNA genes at the bacterial community level showed a very diverse microbiome that was dominated by Alphaproteobacteria in all sites. Bona fide methane-oxidizing taxa were not very abundant (relative abundance less than 0.1%). Based on our results we conclude that methanotrophs did not contribute significantly to nitrogen fixation in the investigated peatlands.
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http://dx.doi.org/10.1186/s13568-018-0607-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5936483PMC
May 2018

Sediment diffusion method improves wastewater nitrogen removal in the receiving lake sediments.

Water Res 2018 07 27;138:312-322. Epub 2018 Mar 27.

Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland.

Sediment microbes have a great potential to transform reactive N to harmless N, thus decreasing wastewater nitrogen load into aquatic ecosystems. Here, we examined if spatial allocation of the wastewater discharge by a specially constructed sediment diffuser pipe system enhanced the microbial nitrate reduction processes. Full-scale experiments were set on two Finnish lake sites, Keuruu and Petäjävesi, and effects on the nitrate removal processes were studied using the stable isotope pairing technique. All nitrate reduction rates followed nitrate concentrations, being highest at the wastewater-influenced sampling points. Complete denitrification with N as an end-product was the main nitrate reduction process, indicating that the high nitrate and organic matter concentrations of wastewater did not promote nitrous oxide (NO) production (truncated denitrification) or ammonification (dissimilatory nitrate reduction to ammonium; DNRA). Using 3D simulation, we demonstrated that the sediment diffusion method enhanced the contact time and amount of wastewater near the sediment surface especially in spring and in autumn, altering organic matter concentration and oxygen levels, and increasing the denitrification capacity of the sediment. We estimated that natural denitrification potentially removed 3-10% of discharged wastewater nitrate in the 33 ha study area of Keuruu, and the sediment diffusion method increased this areal denitrification capacity on average 45%. Overall, our results indicate that sediment diffusion method can supplement wastewater treatment plant (WWTP) nitrate removal without enhancing alternative harmful processes.
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http://dx.doi.org/10.1016/j.watres.2018.03.068DOI Listing
July 2018

Microbial Community Response on Wastewater Discharge in Boreal Lake Sediments.

Front Microbiol 2017 25;8:750. Epub 2017 Apr 25.

Department of Biological and Environmental Science, University of JyväskyläJyväskylä, Finland.

Despite high performance, municipal wastewater treatment plants (WWTPs) still discharge significant amounts of organic material and nitrogen and even microbes into the receiving water bodies, altering physico-chemical conditions and microbial functions. In this study, we examined how nitrified wastewater affects the microbiology of boreal lake sediments. Microbial community compositions were assessed with next generation sequencing of the 16S rRNA gene, and a more detailed view on nitrogen transformation processes was gained with qPCR targeting on functional genes (, , , and ). In both of the two studied lake sites, the microbial community composition differed significantly between control point and wastewater discharge point, and a gradual shift toward natural community composition was seen downstream following the wastewater gradient. SourceTracker analysis predicted that ∼2% of sediment microbes were of WWTP-origin on the study site where wastewater was freely mixed with the lake water, while when wastewater was specially discharged to the sediment surface, ∼6% of microbes originated from WWTP, but the wastewater-influenced area was more limited. In nitrogen transformation processes, the ratio between nitrifying archaea (AOA) and bacteria (AOB) was affected by wastewater effluent, as the AOA abundance decreased from the control point (AOA:AOB 28:1 in Keuruu, 11:1 in Petäjävesi) to the wastewater-influenced sampling points, where AOB dominated (AOA:AOB 1:2-1:15 in Keuruu, 1:3-1:19 in Petäjävesi). The study showed that wastewater can affect sediment microbial community through importing nutrients and organic material and altering habitat characteristics, but also through bringing wastewater-originated microbes to the sediment, and may thus have significant impact on the freshwater biogeochemistry, especially in the nutrient-poor boreal ecosystems.
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http://dx.doi.org/10.3389/fmicb.2017.00750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5403825PMC
April 2017

Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency.

Sci Rep 2016 08 11;6:30897. Epub 2016 Aug 11.

Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland.

Freshwater food webs can be partly supported by terrestrial primary production, often deriving from plant litter of surrounding catchment vegetation. Although consisting mainly of poorly bioavailable lignin, with low protein and lipid content, the carbohydrates from fallen tree leaves and shoreline vegetation may be utilized by aquatic consumers. Here we show that during phytoplankton deficiency, zooplankton (Daphnia magna) can benefit from terrestrial particulate organic matter by using terrestrial-origin carbohydrates for energy and sparing essential fatty acids and amino acids for somatic growth and reproduction. Assimilated terrestrial-origin fatty acids from shoreline reed particles exceeded available diet, indicating that Daphnia may convert a part of their dietary carbohydrates to saturated fatty acids. This conversion was not observed with birch leaf diets, which had lower carbohydrate content. Subsequent analysis of 21 boreal and subarctic lakes showed that diet of herbivorous zooplankton is mainly based on high-quality phytoplankton rich in essential polyunsaturated fatty acids. The proportion of low-quality diets (bacteria and terrestrial particulate organic matter) was <28% of the assimilated carbon. Taken collectively, the incorporation of terrestrial carbon into zooplankton was not directly related to the concentration of terrestrial organic matter in experiments or lakes, but rather to the low availability of phytoplankton.
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http://dx.doi.org/10.1038/srep30897DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4980614PMC
August 2016

A three-way perspective of stoichiometric changes on host-parasite interactions.

Trends Parasitol 2015 Jul 12;31(7):333-40. Epub 2015 May 12.

Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland.

Changes in environmental nutrients play a crucial role in driving disease dynamics, but global patterns in nutrient-driven changes in disease are difficult to predict. In this paper we use ecological stoichiometry as a framework to review host-parasite interactions under changing nutrient ratios, focusing on three pathways: (i) altered host resistance and parasite virulence through host stoichiometry (ii) changed encounter or contact rates at population level, and (iii) changed host community structure. We predict that the outcome of nutrient changes on host-parasite interactions depends on which pathways are modified, and suggest that the outcome of infection could depend on the overlap in stoichiometric requirements of the host and the parasite. We hypothesize that environmental nutrient enrichment alters infectivity dynamics leading to fluctuating selection dynamics in host-parasite coevolution.
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http://dx.doi.org/10.1016/j.pt.2015.04.005DOI Listing
July 2015

Food stoichiometry affects the outcome of Daphnia-parasite interaction.

Ecol Evol 2013 May 2;3(5):1266-75. Epub 2013 Apr 2.

Department of Biological and Environmental Sciences, University of Jyväskylä Jyväskylä, Finland.

Phosphorus (P) is an essential nutrient for growth in consumers. P-limitation and parasite infection comprise one of the most common stressor pairs consumers confront in nature. We conducted a life-table study using a Daphnia-microsporidian parasite model, feeding uninfected or infected Daphnia with either P-sufficient or P-limited algae, and assessed the impact of the two stressors on life-history traits of the host. Both infection and P-limitation negatively affected some life-history traits tested. However, under P-limitation, infected animals had higher juvenile growth rate as compared with uninfected animals. All P-limited individuals died before maturation, regardless of infection. The numbers of spore clusters of the microsporidian parasite did not differ in P-limited or P-sufficient hosts. P-limitation, but not infection, decreased body phosphorus content and ingestion rates of Daphnia tested in separate experiments. As parasite spore production did not suffer even under extreme P-limitation, our results suggest that parasite was less limited by P than the host. We discuss possible interpretations concerning the stoichiometrical demands of parasite and suggest that our results are explained by parasite-driven changes in carbon (C) allocation of the hosts. We conclude that the impact of nutrient starvation and parasite infection on consumers depends not only on the stoichiometric demands of host but also those of the parasite.
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http://dx.doi.org/10.1002/ece3.545DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3678481PMC
May 2013
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