Habitat patchiness, ecological connectivity and the uneven recovery of boreal stream ecosystems from an experimental drought

Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post-drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world's vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms

Anthropogenic impacts and restoration of boreal spring ecosystems

Abstract Human activities have increasingly altered freshwater ecosystems. Land use is a major driver of habitat loss and land use-related input of nutrients and other pollutants from agriculture, forestry and urbanization have deteriorated water quality. Freshwater research has mainly focused on lakes and streams while the effects of anthropogenic stressors on groundwater-dependent ecosystems (GDEs) are poorly known. Likewise, the effectiveness of ecological restoration in mitigating human disturbance in GDEs remains understudied. In this thesis, I studied the effects of two main anthropogenic stressors – land drainage and groundwater contamination – on boreal spring ecosystems and evaluated the recovery of spring biodiversity and ecosystem functioning after habitat restoration. I applied several structural (macroinvertebrates, bryophytes, leaf-decomposing fungi and groundwater bacteria) and functional (organic matter decomposition and primary productivity) measures to provide a comprehensive insight into these issues. Both stressors modified spring ecosystems. Land drainage reduced the key ecosystem processes. Long-term monitoring of drainage-impacted springs showed a marked biodiversity loss and change of spring-dwelling bryophytes, and no signs of recovery were observed after about 20 years since the intial land drainage. Groundwater contamination, indicated by elevated nitrate and chloride concentrations, altered the structure of spring biota, reduced their taxonomic diversity and suppressed primary productivity in the most severely contaminated springs. Spring restoration improved habitat quality by reducing drainage-induced inflow of surface water, thus re-establishing groundwater-dominated hydrological conditions. Restoration increased abundance of habitat-specialist bryophytes and shifted macroinvertebrate composition towards natural conditions, despite the restoration actions being fairly recent. Anthropogenic activities can thus cause severe structural and functional degradation of spring ecosystems, and their self-recovery potential from these stressors seems low. Habitat restoration bears great promise as a cost-effective approach to mitigate drainage-induced impacts on spring ecosystems, but protection and co-management of groundwater resources are urgently needed to secure the role of springs as biodiversity hotspots in the boreal forest landscape.Tiivistelmä Ihmistoiminta muuttaa yhä enemmän vesiekosysteemejä. Maankäyttö on johtanut elinympäristöjen häviämiseen, ja siihen liittyvä ravinne- ja haitta-ainekuormitus maa- ja metsätaloudesta sekä kaupunkiympäristöistä on merkittävästi huonontanut veden laatua johtaen maailmanlaajuiseen vesiluonnon monimuotoisuuden heikentymiseen. Vesiekosysteemien tutkimus on keskittynyt pääasiassa järvi- ja jokiympäristöihin, kun ihmistoiminnan vaikutukset pohjavesiriippuvaisiin ekosysteemeihin tunnetaan edelleen huonosti. Samoin kunnostusten merkitys pohjavesiriippuvaisten ekosysteemien tilan parantamiseksi on selvittämättä. Väitöskirjassani tarkastelin kahden keskeisen ihmistoiminnan – metsäojituksen ja pohjaveden laadun heikkenemisen – vaikutuksia lähde-ekosysteemeihin sekä arvioin elinympäristökunnostusten vaikutuksia niiden rakenteeseen ja toimintaan. Sovelsin työssäni rakenteellisia (pohjaeläimet, sammalet, lehtikariketta hajottavat sienet ja pohjavesibakteerit) ja toiminnallisia (eloperäisen aineksen hajoaminen ja perustuotanto) mittareita tuottamaan kattavan käsityksen tutkimuskysymyksiini. Sekä metsäojitukset että pohjaveden laadun heikkeneminen aiheuttavat muutoksia lähteiden rakenteessa ja toiminnassa. Metsäojitukset hidastavat keskeisiä ekosysteemitoimintoja ja johtavat lähdesammallajiston muutokseen ja monimuotoisuuden taantumiseen. Pohjaveden pilaantuminen, jota työssä ilmennettiin kohonneilla nitraatti- ja kloridipitoisuuksilla, heikentää lähdelajiston monimuotoisuutta, muuttaa lajikoostumusta ja johtaa perustuotannon laskuun voimakkaimmin kuormitetuissa lähteissä. Kunnostus parantaa lähde-elinympäristön laatua vähentämällä metsäojien aiheuttamaa pintavesivaikutusta palauttaen pohjavesivaltaisen hydrologisen tilan. Lähdekunnostusten myötä lähdesammaleet runsastuvat ja pohjaeläinyhteisön rakenne palautuu luonnontilaisten lähteiden kaltaiseksi, vaikka kunnostuksista on kulunut vasta muutamia vuosia. Väitöskirjan tulokset osoittavat, että ihmisen toiminta voi aiheuttaa muutoksia lähde-ekosysteemien rakenteessa ja toiminnassa ja lähteiden luontainen palautuminen häiriöstä on hidasta. Lähde-elinympäristöjen kunnostus vaikuttaa lupaavalta suojelutoimenpiteeltä metsäojitusten vaikutusten vähentämisessä, mutta lähteiden säilyttäminen monimuotoisena ja suojelullisesti arvokkaana luontotyyppinä edellyttää pohjavesivarojen hallinnan ja tilan suojelun tehostamista

Bacterial communities in a subarctic stream network:spatial and seasonal patterns of benthic biofilm and bacterioplankton

Abstract Water-column bacterial communities are assembled by different mechanisms at different stream network positions, with headwater communities being controlled by mass effects (advection of bacteria from terrestrial soils) while downstream communities are mainly driven by environmental sorting. Conversely, benthic biofilms are colonized largely by the same set of taxa across the entire network. However, direct comparisons of biofilm and bacterioplankton communities along whole stream networks are rare. We used 16S rRNA gene amplicon sequencing to explore the spatiotemporal variability of benthic biofilm (2 weeks old vs. mature biofilm) and water-column communities at different network positions of a subarctic stream from early summer to late autumn. Amplicon sequence variant (ASV) richness of mature biofilm was about 2.5 times higher than that of early biofilm, yet the pattern of seasonality was the same, with the highest richness in midsummer. Biofilm bacterial richness was unrelated to network position whereas bacterioplankton diversity was negatively related to water residence time and distance from the source. This pattern of decreasing diversity along the network was strongest around midsummer and diminished greatly as water level increased towards autumn. Biofilm communities were phylogenetically clustered at all network positions while bacterioplankton assemblages were phylogenetically clustered only at the most downstream site. Both early and mature biofilm communities already differed significantly between upstream (1st order) and midstream (2nd order) sections. Network position was also related to variation in bacterioplankton communities, with upstream sites harbouring substantially more unique taxa (44% of all upstream taxa) than midstream (20%) or downstream (8%) sites. Some of the taxa that were dominant in downstream sections were already present in the upmost headwaters, and even in riparian soils, where they were very rare (relative abundance <0.01%). These patterns in species diversity and taxonomic and phylogenetic community composition of the riverine bacterial metacommunity were particularly strong for water-column communities, whereas both early and mature biofilm exhibited weaker spatial patterns. Our study demonstrated the benefits of studying bacterioplankton and biofilm communities simultaneously to allow testing of ecological hypotheses about biodiversity patterns in freshwater bacteria

Streams and riparian forests depend on each other:a review with a special focus on microbes

Abstract In this review, we draw together the research on the two-way connection of streams and their riparian forests of the boreal zone from ecological points of view. Although the knowledge about stream-riparian interactions has increased considerably recently, in practice, riparian zones are still mainly seen as buffers for nutrient and sediment loading. However, recent research has shown that riparian forests disproportionately foster regional biodiversity and maintain stream ecosystem functions and diversity. On the other hand, streams contribute to riparian diversity and ecosystem functions. Microbes are key drivers of global biochemical cycles, and they also interact with plants and animals. The knowledge on microbial communities and understanding of processes they drive has considerably increased due to recent development in microbial profiling methods. However, microbes have been largely neglected in former reviews. Thus, this overview has a special focus on the role of microorganisms in controlling stream-riparian interaction. We also review the land-use pressures that are threatening biodiversity and ecosystem processes of riparian zones in forested landscapes. In addition, we review the possible effects of climate change on stream-riparian interactions. Finally, we outline the research gaps that call for future research

Bacterial communities at a groundwater-surface water ecotone:gradual change or abrupt transition points along a contamination gradient?

Summary Microbial communities contribute greatly to groundwater quality, but the impacts of land-use practices on bacteria in groundwaters and groundwater-dependent ecosystems remain poorly known. With 16S rRNA gene amplicon sequencing, we assessed bacterial community composition at the groundwater-surface water ecotone of boreal springs impacted by urbanization and agriculture, using spring water nitrate-N as a surrogate of contamination. We also measured the rate of a key ecosystem process, organic matter decomposition. We documented a recurrent pattern across all major bacterial phyla where diversity started to decrease at unexpectedly low nitrate-N concentrations (100–300 μg L−1). At 400 NO3−-N μg L−1, 25 bacterial exact sequence variants showed a negative response, resulting in a distinct threshold in bacterial community composition. Chthonomonas, Acetobacterales and Hyphomicrobium were the most sensitive taxa, while only three taxa (Duganella, Undibacterium and Thermoanaerobaculaceae) were enriched due to increased contamination. Decomposition rate responded unimodally to increasing nitrate-N concentration, with a peak rate at ~400 NO3−-N μg L−1, parallelly with a major shift in bacterial community composition. Our results emphasize the utility of bacterial communities in the assessment of groundwater-dependent ecosystems. They also call for a careful reconsideration of threshold nitrate values for defining groundwater ecosystem health and protecting their microbial biodiversity

Host species shape the community structure of culturable endophytes in fruits of wild berry species (Vaccinium myrtillus L., Empetrum nigrum L. and Vaccinium vitis-idaea L.)

Abstract Wild berries are interesting research subjects due to their rich sources of health-beneficial phenolic compounds. However, the internal microbial communities, endophytes, associated with the wild berry fruits are currently unknown. Endophytes are bacteria or fungi inhabiting inside plant tissues, and their functions vary depending on the host species and environmental parameters. The present study aimed to examine community composition of fungal and bacterial endophytes in fruits of three wild berry species (bilberry Vaccinium myrtillus L., lingonberry Vaccinium vitis-idaea L. and crowberry Empetrum nigrum L.) and the effects of host plant species and their growth sites on shaping the endophytic communities. We found that the endophytic community structures differed between the berry species, and fungi were predominant over bacteria in the total endophytic taxa. We identified previously unknown endophytic fungal taxa including Angustimassarina, Dothidea, Fellozyma, Pseudohyphozyma, Hannaella coprosmae and Oberwinklerozyma straminea. A role of soluble phenolic compounds, the intracellular components in wild berry fruits, in shaping the endophytic communities is proposed. Overall, our study demonstrates that each berry species harbors a unique endophytic community of microbes

Habitat patchiness, ecological connectivity and the uneven recovery of boreal stream ecosystems from an experimental drought

Abstract Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post‐drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8‐day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short‐term droughts can have extended consequences for stream ecosystems in the world‘s vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms

Arktisten alueiden typpi- ja raskasmetallipitoisten valumavesien puhdistaminen hybridipuhdistusratkaisuilla (TypArkt) -hankkeen loppuraportti

Abstract In Finland, many human-derived processes, including mining, municipal wastewater treatment, urban runoff, agriculture, forestry and peat extraction, lead to nitrogen and/or heavy metal loads to recipient water bodies. It is often not cost-effective to build active water treatment units for many of these operations. This is true e.g., for mining operations (especially after mine closure), municipalities producing small amounts of wastewater (e.g., in holiday resorts), urban runoffs, peat extraction and agriculture. When active treatment options are not economically feasible, passive treatment options (bioreactors, moss pools) in various combinations with active treatment can be used to treat the water in a cost-efficient manner. It is expected that the demand for passive treatment options will increase in the future, because the quality limits required in water purification are being tightened and there is a need for year-round control of contaminant load to recipient water bodies. In the TypArkt-project, the year-round monitoring of the hybrid purification systems built for the Pyhäsalmi mine in 2018 and in 2019 for the Kallo village wastewater treatment plant in Kittilä municipality has been continued to obtain longer-term performance data. In addition, the pilot structure designed for Levi’s stormwater treatment has been monitored, along with the mixed woodchip bioreactor built by the mine in October 2022 at the Kevitsa mine. Based on the results, target metals can be well removed in Pyhäsalmi in the hybrid purification system, when the last part of the hybrid purification unit, wetland is left out from the study. However, the wetland, and especially the root clumps of lake sediment brought there from a metal-contaminated area, cause an increase in the concentration of metals when the water flows through the wetland. In the hybrid purification structure of Kallo village’s wastewater treatment plant, nitrogen can be removed by an average of slightly more than 30%, which is very good compared to the initial situation, where there was practically no removal at all. In Levi’s stormwater treatment, there has been a small purification box with moss and mushroom-woodchip units, and there are clear reductions in the concentration of nitrite+nitrate nitrogen, but there is variation of purification efficiency between the sampling times in terms of the small concentrations of metals. Nitrogen can be removed in the woodchip bioreactor built at the Kevitsa mine. As a conclusion from the research results, it can be said that the retention of iron, in particular, requires a large settling tank volume. Birch-woodchip bioreactors in the purification units have worked well in the removal of both metals and nitrate nitrogen, and the community of sulfate-reducing bacteria in the bioreactor has formed over time. Moss accumulates metals in its biomass, e.g., the content of iron in dry biomass increased approximately 8 times in 14 months, and mushroom shavings accumulate metals especially over the long term. At the wetland, it is important to pay attention to the cleanliness of the materials brought there.Tiivistelmä Suomessa ja erityisesti myös Suomen pohjoisosissa kylmissä olosuhteissa on monenlaista typpi ja/tai raskasmetallipitoista kuormitusta aiheuttavaa ihmistoimintaa, kuten kaivostoiminta ja jätevedenpuhdistamot. Erilaisia aktiivisia ja asianmukaisia vedenpuhdistusmenetelmiä on käytössä erityisesti toiminnassa olevilla kaivoksilla ja isoilla jätevedenpuhdistamoilla. Kustannusten vuoksi ei kaikkialle kuitenkaan ole järkevää rakentaa kokonaan aktiivista menetelmää vaan erilaiset passiivisten menetelmien (esim. bioreaktorit, sammalaltaat) sekä passiivisten ja aktiivisten menetelmien yhdistelmät voivat olla toimivia ratkaisuja esim. kaivosten jälkikäyttövaiheeseen, muutaman talon kyläyhteisön tai lomakylän jätevesienkäsittelyyn tai taajamien hulevesien käsittelyyn. Passiivisten puhdistusratkaisujen tarpeen ja kysynnän, yhdistettynä mahdollisesti aktiivisiin menetelmiin, odotetaan yhä kasvavan tulevaisuudessa, sillä vedenpuhdistukselle asetettavat vaatimukset tiukkenevat ja ympärivuotiselle kuormituksen hallinnalle on tarvetta. TypArkt-hankkeessa on jatkettu vuonna 2018 Pyhäsalmen kaivokselle ja vuonna 2019 Kittilän kunnan, Kallon kylän, jätevedenpuhdistamolle rakennettujen hybridipuhdistusratkaisujen ympärivuotista seurantaa pidempiaikaisen toimivuustiedon saamiseksi. Lisäksi on seurattu Levin hulevesien käsittelyyn suunniteltua pilottirakennetta, ja Kevitsan kaivokselle kaivoksen lokakuussa 2022 rakentamaa sekapuuhakebioreaktoria. Tulosten perusteella Pyhäsalmella saadaan hyvin poistettua tavoitemetalleja hybridipuhdistusrakenteessa, kun ei oteta huomioon hybridipuhdistusrakenteen viimeistä yksikköä, kosteikkoa. Kosteikko, ja erityisesti sinne metalleilla kontaminoituneelta alueelta tuodut järviruon juuripaakut, aiheuttavat kuitenkin metallien pitoisuuden lisääntymistä, kun vesi virtaa kosteikon läpi. Kallon kylän jätevedenpuhdistamon hybridipuhdistusrakenteessa saadaan typpeä poistumaan keskimäärin vähän yli 30 %, mikä on erittäin hyvä verrattuna lähtötilanteeseen, jossa poistumia ei käytännössä ollut juuri ollenkaan. Levin hulevesien käsittelyssä on ollut pieni puhdistuslaatikko sammal- ja sienihakeyksikköineen, ja siellä nitriitti+nitraattitypen pitoisuuden osalta saadaan selvästi vähenemiä, mutta metallien pienien pitoisuuksien vuoksi esiintyy vaihtelua näytteenottokertojen välillä. Kevitsan kaivokselle rakennetussa puuhakebioreaktorissa saadaan typpeä poistumaan. Johtopäätöksenä tutkimustuloksista voidaan sanoa, että erityisesti raudan pidättäminen vaatii isoa laskeutusallastilavuutta. Puhdistusyksiköissä koivupuuhakebioreaktorit ovat toimineet hyvin sekä metallien, että nitraattitypen poistossa ja sulfaatinpelkistäjäbakteeriyhteisö bioreaktoriin muodostuu ajan kanssa. Sammal kerryttää biomassaansa metalleja, esim. raudan pitoisuus kuivabiomassassa noussut noin 8 kertaiseksi 14 kk aikana, ja sienihake kerryttää etenkin pitkäaikaisesti metalleja. Kosteikolla on tärkeä kiinnittää huomiota sinne tuotavien materiaalien puhtauteen

Latitude dictates plant diversity effects on instream decomposition

Abstract Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes