Fungal assemblages in predictive stream bioassessment: A cross-taxon comparison along multiple stressor gradients

Highlights • We compared fungi, invertebrates and diatoms in model-based stream bioassessment. • Fungal models virtually equaled the overall best model in precision and accuracy. • Fungi were superior in identifying streams degraded by multiple stressors. • Results strongly support the use of microbial communities in stream bioassessment.Degradation of freshwater ecosystems requires efficient tools for assessing the ecological status of freshwater biota and identifying potential cause(s) for their biological degradation. While diatoms and macroinvertebrates are widely used in stream bioassessment, the potential utility of microbial communities has not been fully harnessed. Using data from 113 Finnish streams, we assessed the performance of aquatic leaf-associated fungal decomposers, relative to benthic macroinvertebrates and diatoms, in modelling-based bioassessment. We built multi-taxon niche -type predictive models for fungal assemblages by using genus-based and sequence-based identification levels. We then compared the models’ precision and accuracy in the prediction of reference conditions (number of native taxa) to corresponding models for macroinvertebrates and diatoms. Genus-based fungal model nearly equalled the accuracy and precision of our best model (macroinvertebrates), whereas the sequence-based model was less accurate and tended to overestimate the number of taxa. However, when the models were applied to streams disturbed by anthropogenic stressors (nutrient enrichment, sedimentation and acidification), alone or in combination, the sequence-based fungal assemblages were more sensitive than other taxonomic groups, especially when multiple stressors were present. Microbial leaf decomposition rates were elevated in sediment-stressed streams whereas decomposition attributable to leaf-shredding macroinvertebrates was accelerated by nutrients and decelerated by sedimentation. Comparison of leaf decomposition results to model output suggested that leaf decomposition rates do not detect effectively the presence of multiple simultaneous disturbances. The rapid development of global microbial database may soon enable species-level identification of leaf-associated fungi, facilitating a more precise and accurate modelling of reference conditions in streams using fungal communities. This development, combined with the sensitivity of aquatic fungi in detecting the presence of multiple human disturbances, makes leaf-associated fungal assemblages an indispensable addition in a stream ecologist’s toolbox

Fungal assemblages in predictive stream bioassessment : A cross-taxon comparison along multiple stressor gradients

Highlights • We compared fungi, invertebrates and diatoms in model-based stream bioassessment. • Fungal models virtually equaled the overall best model in precision and accuracy. • Fungi were superior in identifying streams degraded by multiple stressors. • Results strongly support the use of microbial communities in stream bioassessment.Degradation of freshwater ecosystems requires efficient tools for assessing the ecological status of freshwater biota and identifying potential cause(s) for their biological degradation. While diatoms and macroinvertebrates are widely used in stream bioassessment, the potential utility of microbial communities has not been fully harnessed. Using data from 113 Finnish streams, we assessed the performance of aquatic leaf-associated fungal decomposers, relative to benthic macroinvertebrates and diatoms, in modelling-based bioassessment. We built multi-taxon niche -type predictive models for fungal assemblages by using genus-based and sequence-based identification levels. We then compared the models’ precision and accuracy in the prediction of reference conditions (number of native taxa) to corresponding models for macroinvertebrates and diatoms. Genus-based fungal model nearly equalled the accuracy and precision of our best model (macroinvertebrates), whereas the sequence-based model was less accurate and tended to overestimate the number of taxa. However, when the models were applied to streams disturbed by anthropogenic stressors (nutrient enrichment, sedimentation and acidification), alone or in combination, the sequence-based fungal assemblages were more sensitive than other taxonomic groups, especially when multiple stressors were present. Microbial leaf decomposition rates were elevated in sediment-stressed streams whereas decomposition attributable to leaf-shredding macroinvertebrates was accelerated by nutrients and decelerated by sedimentation. Comparison of leaf decomposition results to model output suggested that leaf decomposition rates do not detect effectively the presence of multiple simultaneous disturbances. The rapid development of global microbial database may soon enable species-level identification of leaf-associated fungi, facilitating a more precise and accurate modelling of reference conditions in streams using fungal communities. This development, combined with the sensitivity of aquatic fungi in detecting the presence of multiple human disturbances, makes leaf-associated fungal assemblages an indispensable addition in a stream ecologist’s toolbox

The importance of sedimenting organic matter, relative to oxygen and temperature, in structuring lake profundal macroinvertebrate assemblages

We quantified the role of a main food resource, sedimenting organic matter (SOM), relative to oxygen (DO) and temperature (TEMP) in structuring profundal macroinvertebrate assemblages in boreal lakes. SOM from 26 basins of 11 Finnish lakes was analysed for quantity (sedimentation rates), quality (C:N:P stoichiometry) and origin (carbon stable isotopes, d13C). Hypolimnetic oxygen and temperature were measured from each site during summer stratification. Partial canonical correspondence analysis (CCA) and partial regression analyses were used to quantify contributions of SOM, DO and TEMP to community composition and three macroinvertebrate metrics. The results suggested a major contribution of SOM in regulating the community composition and total biomass. Oxygen best explained the Shannon diversity, whereas TEMP had largest contribution to the variation of Benthic Quality Index. Community composition was most strongly related to d13C of SOM. Based on additional d13C and stoichiometric analyses of chironomid taxa, marked differences were apparent in their utilization of SOM and body stoichiometry; taxa characteristic of oligotrophic conditions exhibited higher C:N ratios and lower C:P and N:P ratios compared to the species typical of eutrophic lakes. The results highlight the role of SOM in regulating benthic communities and the distributions of individual species, particularly in oligotrophic systems

Maa- ja metsätalouden kuormittamien pintavesien ekologinen tila ja sen seuranta

Maa- ja metsätalouden hajakuormitus on laaja-alaisimmin Suomen vesien tilaa heikentävä tekijä, mutta tietämys kuormituksen vaikutuksista vesien ekologiseen tilaan on ollut puutteellista. Tähän julkaisuun on koottu Maa- ja metsätalousministeriön rahoittaman hajakuormituksen vesistövaikutusten seurannan (ns ”MaaMet-seuranta”) ensimmäisten vuosien 2007-2012 tulokset. Työssä tarkastellaan 152 hajakuormitetun joki-, järvi- ja rannikkovesimuodostuman ekologista tilaa fysikaalis-kemiallisten (ravinteet) ja biologisten laatutekijöiden (kasviplankton, vesikasvit ja päällyslevät, pohjaeläimistö, kalasto) perusteella. Tutkimuksessa selvitetään erityisesti laatutekijöiden tila-arvioiden suhdetta ihmistoiminnan aiheuttamiin ympäristöpaineisiin. Näiden yhteyksien ymmärtäminen on edellytys kustannustehokkaiden vesiensuojelutoimien suunnittelulle. Tulosten perusteella hajakuormitus on merkittävä ekologista tilaa huonontava tekijä. Tyydyttävässä tai sitä huonommassa tilaluokassa oli fysikaalis-kemiallisten laatutekijöiden perusteella 69 % joki-, 66 % järvi- ja 98 % rannikkokohteista, kun taas vähintään yhden biologisen laatutekijän mukaan tilaluokka oli hyvää huonompi 68 % jokikohteista, 87 % järvistä ja 100 % rannikkovesikohteista. Fysikaalis-kemiallisilla tilamuuttujilla oli voimakas yhteys valuma-alueen peltoisuuteen. Samoin useimmilla biologisilla tilamuuttujilla oli yhteys valuma-alueen peltojen osuuteen ja ravinnepitoisuuksiin. Selvimmin tämä ilmeni jokimuodostumissa. Karkeasti arvioiden jokikohteet olivat hyvää huonommassa ekologisessa tilassa niiden valuma-alueen peltoisuuden ylittäessä 10–15 % ja järvet peltoisuuden ylittäessä 5–10 %. Vasteiden voimakkuus ja muoto kuitenkin vaihtelivat merkittävästi sekä ekosysteemien (joet, järvet ja rannikot) että laatutekijöiden välillä. Useamman laatutekijään perustuva ekologisen tilan arviointi vähensi virhettä ja voimisti paineyhteyttä. Monipuolinen ekologisen tilan arviointi parantaakin ihmistoiminnan aiheuttaman ekologisen tilan muutoksen arviointia. Biologisten muuttujien arvoissa oli paljon vaihtelua. Tämä aiheutuu sekä luontaisista tekijöistä että näytteenoton ja luokittelujärjestelmän epätarkkuudesta. Tutkimus on tuonut esille useita oleellisia kehittämistarpeita ekologisen tilan arviointijärjestelmässä. MaaMet-seuranta tuottaa tärkeää uutta tietoa Suomen hajakuormitettujen vesien tilasta. Jatkossa kun ekologista tilaa kuvaavien muuttujien vaihtelun suuruus ja syyt tiedetään paremmin, voidaan tarkemmin ymmärtää hajakuormituksen vaikutukset pintavesien ekologiseen tilaan. Näin seurannan tulosten arvo kasvaa seurantavuosien karttuessa. Paikallisesti kattava ja ajallisesti jatkuva hajakuormitettujen vesien seuranta on välttämätön edellytys kustannustehokkaiden vesiensuojelutoimien suunnittelulle ja niiden vaikutusten luotettavalle todentamiselle pyrittäessä kohti jokien, järvien ja rannikkovesien hyvää ekologista tilaa

Ohje pintavesien ekologisen ja kemiallisen tilan luokitteluun vuosille 2012–2013 − päivitetyt arviointiperusteet ja niiden soveltaminen

Suomen ensimmäinen pintavesien ekologisen ja kemiallisen tilan luokittelu laadittiin vuonna 2008 vesienhoidon ensimmäisen suunnittelukauden ohjeistuksen (Ympäristöhallinnon ohjeita OH 3/2009) mukaisesti. Tässä oppaassa esitetään päivitetyt arviointiperusteet pintavesien ekologisen ja kemiallisen tilan arviointiin ja luokitteluun vesienhoidon toista suunnittelukautta varten. Ohje on ensisijaisesti tarkoitettu ELY-keskuksille vesienhoidon suunnittelussa käytettäväksi vesien tilan luokitteluun. ELY-keskusten on tärkeää huomioida ja ottaa systemaattisesti käyttöön ohjeessa esitetyt päivitetyt arviointiperusteet. Vesien tilan luokittelussa käytettäviä parametreja on tapauskohtaisesti sisällytettävä toiminnanharjoittajien velvoitetarkkailuihin ja YVA-selvityksiin. Ohjeessa esitetään ne muutokset ja lisäykset, jotka vuosien 2012–2013 aikana toteutettavassa luokittelussa tulee huomioida verrattuna ensimmäisen suunnittelukauden ohjeistukseen. Muilta osin noudatetaan ensimmäisen luokittelukierroksen ohjeistusta (Ympäristöhallinnon ohjeita OH 3/2009). Kaikki luokittelutekijöiden arviointiperusteet (vertailuarvot ja luokkarajat) ovat tässä ohjeessa liitteinä, eikä ohjeen OH 3/2009 liitetaulukoita tule käyttää

An extended Benthic Quality Index for assessment of lake profundal macroinvertebrates: addition of indicator taxa by multivariate ordination and weighted averaging

The chironomid Benthic Quality Index (BQI) is a widely used metric in assessments of lake status. The BQI is based on 7 indicator taxa, which like most profundal fauna, often occur sporadically in low densities. Hence, a major weakness of the index is that it cannot be calculated when indicator taxa are not captured. Thus, an extension of the BQI that incorporates more macroinvertebrate taxa is desirable. We used 2 statistical approaches (Detrended Correspondence Analysis and Weighted Averaging) to estimate new benthic quality indicator scores for profundal macroinvertebrate taxa and to construct modified BQIs called Profundal Invertebrate Community Metrics (PICMs). We calibrated the PICMs and evaluated their bioassessment performance with macroinvertebrate and environmental data from 735 lake basins in Finland. Both PICMs included 70 taxa and could be calculated for a substantially greater proportion (99.5%) of sites than the original BQI (83.5%). Compared to the BQI, the PICMs were more strongly correlated with whole-community variation and were more predictable from environmental factors independent of human activities in undisturbed reference lakes. PICMs were more specific in identifying undisturbed lakes and more sensitive in discriminating nonreference from reference lakes. The strength of relationships to total P concentration was equal among indices. These results suggest that the extension of BQI to incorporate more taxa will increase generality, accuracy, and representativeness of lake profundal macroinvertebrate assessment.peerReviewe

Does the buffer width matter:testing the effectiveness of forest certificates in the protection of headwater stream ecosystems

Abstract Forest harvest has multiple impacts on adjoining freshwater ecosystems, particularly headwater streams which typically receive minimal protection against forestry. However, evidence on the effectiveness of differently sized riparian buffers remains limited. Using data from two discrete regions of Finland, we assessed the effectiveness of riparian buffers in providing protection for the riparian and stream environment, benthic invertebrate diversity and species composition, and ecosystem functioning of boreal headwater streams. Our study included streams with both wide (>15 m) and narrow (<15 m) riparian buffers, enabling comparison of the two dominant forest certificates (FSC and PEFC). Compared to unharvested reference streams, nutrient concentrations as well as stream and riparian light intensity and temperature were higher at forestry-impacted sites. The amount of woody debris, cover of aquatic mosses and particulate organic matter standing stock were strongly reduced in streams draining harvested forests, especially in narrowly buffered streams. Changes in light and nutrient conditions induced a transition towards more autotrophic conditions. Organic matter decomposition rates were elevated in forestry-impacted sites only in the southern region. Forest harvest decreased macroinvertebrate diversity and evenness, and altered community composition in the northern region, but much weaker changes were observed in the southern region. Our findings support the retention of riparian buffers, but also confirm that their effectiveness depends on the environmental context and thus remains poorly predictable. Our results also suggest that the widely applied PEFC certification does not provide sufficient protection for stream ecosystems and more stringent protocols are needed to ensure ecological sustainability of forestry

Drainage‐induced browning causes both loss and change of benthic biodiversity in headwater streams

Abstract Concentrations of dissolved organic carbon (DOC) have increased over the past few decades, causing freshwater browning. Impacts of browning on biodiversity have been little studied, despite many of the individual stressors associated with browning being known to control freshwater communities. We explored the responses of benthic invertebrates along a wide gradient of DOC concentrations (3.6–27 mg L−1) in 63 boreal streams variously impacted by peatland drainage or peat production. DOC was a prime determinant of macroinvertebrate diversity and abundance, with the strongest negative response in algal scrapers. Threshold indicator taxa analysis indicated an abrupt community change at 12–13 mg DOC L−1, with only four taxa increasing, while 13 taxa decreased along the gradient. Our findings of both a gradual loss and abrupt change of biodiversity along a browning gradient provide a benchmark against which changes to stream biodiversity relative to the predicted browning trend can be gauged