Climate warming and consequent greening of subarctic landscapes increase the availability of organic carbon to the detrital food webs in aquatic ecosystems. This may cause important shifts in ecosystem functioning through the functional feeding patterns of benthic organisms that rely differently on climatically altered carbon resources. Twenty-five subarctic lakes in Finnish Lapland across a tree line ecotone were analysed for limnological and optical variables, carbon (delta C-13) and nitrogen (delta N-15) stable isotope (SI) composition of surface sediment organic matter (OM) and fossil Chironomidae (Diptera) remains to examine environmental controls behind chironomid functional feeding group (FFG) structure and their isotopic associations for assessing ecosystem functioning and carbon utilisation. We hypothesise that the chironomid SI signatures reflect increased allochthony with increasing allochthonous input, but the resource use may be altered by the functional characteristics of the assemblage. Multivariate analyses indicated that carbon geochemistry in the sediments (delta C-13, delta N-15, C/N), nutrients, indices of productivity (chlorophyll-a) and lake water optical properties, related to increasing presence of OM, played a key role in defining the chironomid FFG composition and isotopic signatures. Response modelling was used to examine how individual FFGs respond to environmental gradients. They showed divergent responses for OM quantity, dissolved organic carbon and nutrients between feeding strategies, suggesting that detritivores and filter feeders prefer contrasting carbon and nutrient conditions, and may thus hold paleoecological indicator potential to identify changes between different carbon fluxes. Benthic production was the primary carbon source for the chironomid assemblages according to a three-source SI mixing model, whereas pelagic and terrestrial components contributed less. Between-lake variability in source utilisation was high and controlled primarily by allochthonous OM inputs. Combination of biogeochemical modelling and functional classification is useful to widen our understanding of subarctic lake ecosystem functions and responses to climate-driven changes in limnology and catchment characteristics for long-term environmental change assessments and functional paleoecology.

Benthic macrofauna is regularly used in monitoring programmes, however the vast majority of benthic eukaryotic biodiversity lies mostly in microscopic organisms, such as meiofauna (invertebrates <1 mm) and protists, that rapidly responds to environmental change. These communities have traditionally been hard to sample and handle in the laboratory, but DNA sequencing has made such work less time consuming. While DNA sequencing captures both alive and dead organisms, environmental RNA (eRNA) better targets living organisms or organisms of recent origin in the environment. Here, we assessed the biodiversity of three known bioindicator microeukaryote groups (nematodes, foraminifera, and ciliates) in sediment samples collected at seven coastal sites along an organic carbon (OC) gradient. We aimed to investigate if eRNA shotgun sequencing can be used to simultaneously detect differences in (i) biodiversity of multiple microeukaryotic communities; and (ii) functional feeding traits of nematodes. Results showed that biodiversity was lower for nematodes and foraminifera in high OC (6.2%-6.9%), when compared to low OC sediments (1.2%-2.8%). Dissimilarity in community composition increased for all three groups between Low OC and High OC, as well as the classified feeding type of nematode genera (with more nonselective deposit feeders in high OC sediment). High relative abundant genera included nematodeSabatieriaand foraminiferaElphidiumin high OC, andCryptocaryon-like ciliates in low OC sediments. Considering that future sequencing technologies are likely to decrease in cost, the use of eRNA shotgun sequencing to assess biodiversity of benthic microeukaryotes could be a powerful tool in recurring monitoring programmes.

Tiivistelmä * Referat * Abstract Tutkimuksessa selvitettiin maan muokkausmenetelmien vaikutusta savimaalla. Tutkimus tehtiin Yara Suomen koetilalla Vihdissä. Siellä vuodesta 2007 käynnissä olleiden yhtäjaksoisten muokkauskokeiden jatkoksi haluttiin selvittää, miten muokkausmenetelmät ovat vaikuttaneet maahan. Kokeessa tutkittiin suorakylvetyn, sänkimuokatun ja kynnetyn maan eroja. Tutkimuksessa selvitettiin maan rakenteeseen liittyviä ominaisuuksia: maan kosteus keväällä, penetrometri läpäisevyys, lierojen kekolaskenta, maan orgaanisen hiilen pitoisuus, maan ravinneanalyysit sekä Peltomaan laatutesti. Mittaukset ja määritykset tehtiin kasvukauden 2015 aikana. Kokeista selvisi, että pitkäaikaiset muutokset muokkauksessa vaikuttivat maahan erilaisesti. Penetrometri mittauksissa kävi ilmi, että kynnetyn maan työntövastus oli pienin 0–25 cm syvyydessä, josta syvemmälle mentäessä kaikkien muokkaustapojen työntövastus oli lähes sama. Maan orgaanisen hiilen pitoisuus? 0–15 cm syvyydessä oli kevennetyillä muokkaustavoilla 26 % suurempi kuin kynnetyllä. Maan kosteus keväällä oli suorakylvetyssä maassa suurin ja kynnetyssä pienin. Lierolaskennassa kävi ilmi, että kynnetyllä maalla oli kekoja vähemmän kuin muissa muokkauksissa. Maan ravinneanalyyseissä ei löytynyt merkitsevää eroa eri muokkaustapojen välillä. Peltomaan laatutestissä tutkittiin maan ominaisuuksia fysikaalisesti ja biologisesti. Peltomaan laatutestin perusteella pintamaan vedenjohtavuus on kaikilla mailla hyvä, suorakylvetystä maasta ei löydy tiivistymää ja siinä on eniten lieroja. Lopuksi todettiin, että tämän tutkimuksen mukaan ei voida päätellä, mikä muokkaustavoista olisi paras savimaalla pohjoisissa olosuhteissa. Kuitenkin tutkimus viittaa siihen että, pitkään jatkunut suorakylvö saattaisi olla hyvä vaihtoehto savimaan viljelyssä.

Sustainability assessments can be a powerful tool in decision-making regarding technical innovations. In this study, a sustainability assessment of technical systems for recovering nutrients and carbon from domestic wastewater is presented. Multi-criteria analysis was used to calculate a sustainability score of three different technical systems compared to a baseline in two case-studies: the Fyriså river catchment in Sweden and the Słupia river catchment in Poland. Two participatory workshops with local stakeholders were held in each case-study, the first to co-develop the system alternatives and sustainability criteria and the second to collect stakeholder weighting of the criteria. Although the systems assessed in both case studies were similar, the resulting sustainability scores were different. In Fyris, although the differences in scores was small, the preferred alternative was introduction of source-separation followed by a large redesign of the treatment and phosphorus extraction from incinerated sludge was the least sustainable alternative. For the Słupia systems the scores varied more, and the preferred system was a large redesign of the wastewater treatment followed by ammonia stripping of the reject water and the source-separation alternative received the lowest score. In both case-studies, the more costly system received highest sustainability score indicating the large potential benefits of enhancing resource recovery from domestic wastewater. Stakeholders did not prioritize technical aspects over the other sustainability criteria, yet most of research on resource recovery interventions is focused on technical performance.