Diatom communities and ecological status classification in the upper Po River basin



  • Francesca Bona | francesca.bona@unito.it Department of Life Sciences and Systems Biology, University of Turin; ALPSTREAM - Alpine Stream Research Centre, Ostana, Italy. https://orcid.org/0000-0003-2260-8001
  • Valentina La Morgia ISPRA - Institute for Environmental Protection and Research, Ozzano Emilia (BO), Italy. https://orcid.org/0000-0001-9915-3194
  • Stefano Fenoglio Department of Life Sciences and Systems Biology, University of Turin; ALPSTREAM - Alpine Stream Research Centre, Ostana, Italy. https://orcid.org/0000-0001-6931-652X
  • Luana Morandi Department of Life Sciences and Systems Biology, University of Turin, Italy.
  • Elisa Falasco Department of Life Sciences and Systems Biology, University of Turin; ALPSTREAM - Alpine Stream Research Centre, Ostana, Italy. https://orcid.org/0000-0003-1529-0904


One of the main challenges in river management is the setting of nutrient thresholds that support good ecological status, which is the main objective to achieve for the European member states. This is a complex process, which needs an accurate analysis of the data collected so far for the ecological classification of rivers belonging to different typologies. We analysed the data of the multiannual monitoring concerning diatoms and nutrients in the upper Po River (NW Italy) with the aim of exploring the response of diatom community in terms of species composition, ecological guilds and indices. We considered data of 390 samples, of which 2/3 belonging to the “Central macrotype” (i.e. lowland stretches) and 1/3 to “Alpine siliceous”. We performed a Principal Coordinate Analysis to detect community patterns with respect to water chemical classification and macrotypes highlighting species and ecological guilds characteristic of samples along a water quality gradient. We then performed a partial RDA to focus on the role of environmental and spatial factors in shaping the diatom community in each of the two macrotypes. Finally, we investigated the concordance between the Italian normative indices ICMi (for diatoms) and LIMECO (a chemical index of water quality). We found significant differences in the diatom communities of the two macrotypes and in their response to water quality and to spatial factors. Communities resulted as much more uniform in sites with a low water quality, with characteristic species such as Navicula gregaria, Nitzschia palea and Sellaphora nigri. On the other hands, moderately disturbed sites (in terms of trophic level) were characterised by the highest guild diversity. The RDA confirmed the importance of spatial factors in shaping the diatom assemblages, especially in Alpine streams where the physical barriers may condition species dispersion. The comparison between the two normative indices highlights that the correspondence in the classification is achieved in the 57% (Alpine macrotype) and 43% (Central macrotype) of samples. According to our findings, we suggest the revision of the ICMi, both class boundaries and reference value. In addition, we recommend to lower LIMECO threshold for total phosphorus: indeed, several studies have shown significant changes in the diatom community composition starting from very low values (below the current LIMECO threshold, i.e. 50 µgL-1). Moreover, the extension of our study to the whole Po River basin will complete our knowledge of species not yet included in the diatom indices and of the community response to nutrient levels also in other macrotypes.



PlumX Metrics


Download data is not yet available.


Almeida SF, Elias C, Ferreira J, Tornés E, Puccinelli C, Delmas F, Dörflinger G, Urbanič G, Marcheggiani S, Rosebery J, Mancini L, Sabater S, 2014. Water quality assessment of rivers using diatom metrics across Mediterranean Europe: a methods intercalibration exercise. Sci. Total Environ. 476:768-776. DOI: https://doi.org/10.1016/j.scitotenv.2013.11.144

Anderson MJ, 2001. A new method for non-parametric multivariate analysis of variance. Austral. Ecol. 26:32-46. DOI: https://doi.org/10.1046/j.1442-9993.2001.01070.x

ARPA Piemonte, Regione Piemonte, 2020. [Stato dell’Ambiente in Piemonte. Relazione 2020].[in Italian]. Avallabile from: http://relazione.ambiente.piemonte.it/2020/it/acqua/stato/corsi-d-acqua

Battegazzore M, Morisi A, Gallino B, Fenoglio S, 2004. Environmental quality evaluation of alpine springs in NW Italy using benthic diatoms. Diatom Res. 19:149-165. DOI: https://doi.org/10.1080/0269249X.2004.9705868

Berthon V, Bouchez A, Rimet F, 2011. Using diatom life-forms and ecological guilds to assess organic pollution and trophic level in rivers: a case study of rivers in south-eastern France. Hydrobiologia 673:259-271. DOI: https://doi.org/10.1007/s10750-011-0786-1

Black RW, Moran PW, Frankforter JD, 2011. Response of algal metrics to nutrients and physical factors and identification of nutrient thresholds in agricultural streams. Environ. Monit. Assess. 175: 97-417. DOI: https://doi.org/10.1007/s10661-010-1539-8

Borcard D, Legendre P, Avois-Jacquet C, Tuomisto H, 2004. Dissecting the spatial structure of ecological data at multiple scales. Ecology 85:1826–1832. DOI: https://doi.org/10.1890/03-3111

Bottin M, Soininen J, Ferrol M, Tison-Rosebery J, 2014. Do spatial patterns of benthic diatom assemblages vary across regions and years? Freshw. Sci. 33:402-416. DOI: https://doi.org/10.1086/675726

Cantonati M, 1998. Diatom communities of springs in the Southern Alps. Diatom Res. 13:201-220. DOI: https://doi.org/10.1080/0269249X.1998.9705449

Çelekli A, Toudjani A, Gümüş EY, Kayhan S, Lekesiz H, Çetin T, 2019. Determination of trophic weight and indicator values of diatoms in Turkish running waters for water quality assessment. Turk. J. Bot. 43:90-101. DOI: https://doi.org/10.3906/bot-1704-40

CEMAGREF, 1982. [Étude des méthodes biologiques d’appreciation quantitative de la qualité des eaux. Rapport Q. E. Lyon].[Book in French]. Lyon, A.F. Bassin Rhône- Mediterranée Corse: 218 pp.

De Bie T, De Meester L, Brendonck L, Martens K, Goddeeris B, Ercken D, Hampel H, Denys L, Vanhecke L, Van der Gucht K, Van Wichelen J, Vyverman W, Declerck SAJ, 2012. Body size and dispersal mode as key traits determining metacommunity structure of aquatic organisms. Ecol. Lett. 15:740–747. DOI: https://doi.org/10.1111/j.1461-0248.2012.01794.x

Dell'Uomo A, Pensieri A, Corradetti D, 1999. Epilithic diatoms from the Esino river (central Italy) and their use for the evaluation of the biological quality of the water. Cryptogamie Algol. 20:253-269. DOI: https://doi.org/10.1016/S0181-1568(99)80018-X

Dell'Uomo A, Torrisi M, 2011. The eutrophication/pollution index-diatom based (EPI-D) and three new related indices for monitoring rivers: The case study of the river Potenza (the Marches, Italy). Plant Biosyst. 145:331-341. DOI: https://doi.org/10.1080/11263504.2011.569347

De Luca DA, Lasagna M, Debernardi L, 2020. Hydrogeology of the western Po plain (Piedmont, NW Italy). J. Maps 16:265-273. DOI: https://doi.org/10.1080/17445647.2020.1738280

Dong X, Li B, He F, Gu Y, Sun M, Zhang H, Tan L, Xiao W, Liu S, Cai Q, 2016. Flow directionality, mountain barriers and functional traits determine diatom metacommunity structuring of high mountain streams. Sci. Rep. 6:1-11. DOI: https://doi.org/10.1038/srep24711

Dray S, Legendre P, Peres-Neto PR, 2006. Spatial modelling: a comprehensive framework for principal coordinate analysis of neighbour matrices (PCNM). Ecol. Modell. 196:483–493. DOI: https://doi.org/10.1016/j.ecolmodel.2006.02.015

European Committee for Standardization, 2003. Norm EN 13946. Water Quality Guidance Standard for the Routine Sampling and Pretreatment of Benthic Diatoms from Rivers. European Standard European Committee for Standardization, Brussels: pp. 14.

European Committee for Standardization, 2004. [Norm UNI EN 14407:2004. Qualità dell’acqua - Linea guida per l’identificazione, il conteggio e la classificazione di campioni di diatomee bentoniche da acque correnti].[in Italian]. European Committee for Standardization, Brussels.

European Committee for Standardization, 2005. [Norm UNI EN 13946:2005. Qualità dell’acqua - Norma guida per il campionamento di routine ed il pretrattamento di diatomee bentoniche da fiumi].[in Italian]. European Committee for Standardization, Brussels.

European Communities, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. Official Journal L 327, 22/12/2000, pp. 73.

Falasco E, Bona F, 2011. Diatom community biodiversity in an Alpine protected area: a study in the Maritime Alps Natural Park. J. Limnol. 70:157. DOI: https://doi.org/10.4081/jlimnol.2011.157

Falasco E, Mobili L, Risso AM, Bona F, 2012. First considerations on the ICMi diatom index application in north-west Italy. Biologia Ambientale 26:21–28.

Falasco E, Bona F, 2013. Recent findings regarding non-native or poorly known diatom taxa in north-western Italian rivers. J. Limnol. 72:e4. DOI: https://doi.org/10.4081/jlimnol.2013.e4

Falasco E, Piano E, Bona F, 2016. Suggestions for diatom-based monitoring in intermittent streams. Knowl. Manag. Aquat. Ec. 417:38. DOI: https://doi.org/10.1051/kmae/2016025

Falasco E, Bona F, Monauni C, Zeni A, Piano E, 2019. Environmental and spatial factors drive diatom species distribution in Alpine streams: Implications for biomonitoring. Ecol. Indic. 106:105441. DOI: https://doi.org/10.1016/j.ecolind.2019.105441

Falasco E, Doretto A, Fenoglio S, Piano E, Bona F, 2020. Supraseasonal drought in an Alpine river: effects on benthic primary production and diatom community: Diatoms and chlorophyll a in an intermittent Alpine river. J. Limnol. 79:1933. DOI: https://doi.org/10.4081/jlimnol.2020.1933

Falasco E, Bona F, Risso AM, Piano E, 2021a. Hydrological intermittency drives diversity decline and functional homogenization in benthic diatom communities. Sci. Total Environ. 762:143090. DOI: https://doi.org/10.1016/j.scitotenv.2020.143090

Falasco E, Ector L, Wetzel CE, Badino G, Bona F, 2021b. Looking back, looking forward: a review of the new literature on diatom teratological forms (2010–2020). Hydrobiologia 848:1675-1753. DOI: https://doi.org/10.1007/s10750-021-04540-x

Government of Italy, 2010. [Regolamento recante i criteri tecnici per la classificazione dello stato dei corpi idrici superficiali, per la modifica delle norme tecniche del decreto legislativo 3 aprile 2006, n. 152 “Norme in materia ambientale, predisposto ai sensi dell’articolo 75, comma 3, del decreto legislativo medesimo”].[In Italian]. Gazzetta Ufficiale L. 30, 07/02/2011.

Hammer Ø, Harper DAT, Ryan PD, 2001. PAST: Paleontological Statistics Software Package for Education and Data Analysis. Palaeontol. Electronica 4:1-9.

Hausmann S, Charles DF, Gerritsen J, Belton TJ, 2016. A diatom-based biological condition gradient (BCG) approach for assessing impairment and developing nutrient criteria for streams. Sci. Total Environ. 562:914-927. DOI: https://doi.org/10.1016/j.scitotenv.2016.03.173

Hicks MB, Taylor JM, 2019. Diatom assemblage changes in agricultural alluvial plain streams and application for nutrient management. J. Environ. Qual. 48:83-92. DOI: https://doi.org/10.2134/jeq2018.05.0196

ISPRA, 2014. [Protocollo di campionamento e analisi delle diatomee bentoniche dei corsi d’acqua, p. 111]. In: [Metodi biologici per le acque superficiali interne].[in Italian]. Rome: ISPRA.

Kristensen P, Whalley C, Zal FNN, Christiansen T, 2018. European waters assessment of status and pressures 2018. EEA Report 7/2018.

Legendre P, Gallagher E D,2001. Ecologically meaningful transformations for ordination of species data. Oecologia 129:271–280. DOI: https://doi.org/10.1007/s004420100716

Licursi M, Gómez N, Sabater S, 2016. Effects of nutrient enrichment on epipelic diatom assemblages in a nutrient-rich lowland stream, Pampa Region, Argentina. Hydrobiologia 766:135–150. DOI: https://doi.org/10.1007/s10750-015-2450-7

Lu X, Liu Y, Fan Y, 2020. Diatom taxonomic composition as a biological indicator of the ecological health and status of a river basin under agricultural influence. Water 12:2067. DOI: https://doi.org/10.3390/w12072067

Mancini L, Sollazzo C, 2009. [Metodo per la valutazione dello stato ecologico delle acque correnti: comunità diatomiche].[in Italian]. Rapporti ISTISAN 09/19.

Novais MH, Morais MM, Rosado J, Dlas LS, Hoffmann H, Ector L, 2014. Diatoms of temporary and permanent watercourses in Southern Europe (Portugal). River Res. Appl. 30:1216-1232. DOI: https://doi.org/10.1002/rra.2818

Oksanen J, Blanchet FG, Friendly M, Kindt R, Legendre P, McGlinn D, Minchin PR, O'Hara RB, Simpson GL, Solymos P, Stevens MHH, Szoecs E, Wagner H, 2020. Vegan: Community Ecology Package. R package version 2.5-7. https://CRAN.R-project.org/package=vegan

Pan Y, Stevenson RJ, Hill BH, Herlihy AT, Collins GB, 1996. Using diatoms as indicators of ecological conditions in lotic systems: A regional assessment. J. N. Am. Benthol. Soc. 15:481-495. DOI: https://doi.org/10.2307/1467800

Passy SI, 2007. Diatom ecological guilds display distinct and predictable behavior along nutrient and disturbance gradients in running waters. Aquat. Bot. 86:171-178. DOI: https://doi.org/10.1016/j.aquabot.2006.09.018

Peres-Neto PR, Legendre P, Dray S, Borcard D, 2006. Variation partitioning of species data matrices: estimation and comparison of fractions. Ecology 87:2614-2625. DOI: https://doi.org/10.1890/0012-9658(2006)87[2614:VPOSDM]2.0.CO;2

Phillips G, Kelly M, Teixeira H, Salas Herrero MF, Free G, Leujak W, Lyche Solheim A, Varbiro G, Poikane S, 2018. Best practice for establishing nutrient concentrations to support good ecological status. EUR 29329 EN. Publications Office of the European Union, Luxembourg.

Piano E, Falasco E, Bona F, 2016. Mediterranean rivers: Consequences of water scarcity on benthic algal chlorophyll a content. J. Limnol. 76:1503. DOI: https://doi.org/10.4081/jlimnol.2016.1503

Piano E, Falasco E, Bona F, 2017. How does water scarcity affect spatial and temporal patterns of diatom community assemblages in Mediterranean streams? Freshwater Biol. 62:1276–1287. DOI: https://doi.org/10.1111/fwb.12944

Pillsbury R, Stevenson RJ, Munn MD, Waite I, 2019. Relationships between diatom metrics based on species nutrient traits and agricultural land use. Environ. Monit. Assess. 191:1-26. DOI: https://doi.org/10.1007/s10661-019-7357-8

Poikane S, Várbíró G, Kelly MG, Birk S, Phillips G, 2021. Estimating river nutrient concentrations consistent with good ecological condition: More stringent nutrient thresholds needed. Ecol. Indic. 121:107017. DOI: https://doi.org/10.1016/j.ecolind.2020.107017

Ponader KC, Charles DF, Belton TJ, 2007. Diatom based TP and TN inference models and indices for monitoring nutrient enrichment of New Jersey streams. Ecol. Indic. 7:79–93. DOI: https://doi.org/10.1016/j.ecolind.2005.10.003

Rimet F, Bouchez A, 2012. Life-forms, cell-sizes and ecological guilds of diatoms in European rivers. Knowl. Manag. Aquat. Ecosyst. 406:01. DOI: https://doi.org/10.1051/kmae/2012018

Rott E, Pfister P, van Dam H, Pipp E, Pall K, Binder N, Ortler K, 1999. [Indikationslisten für Aufwuchsalgen in Österreichischen Fliessgewässern, Teil 2: Trophieindikation und autökologische Anmerkungen Bundesministerium für Landund Forstwirtschaf].[Book in German]. Wien, Wasserwirtschaftskataster: 248 pp.

Salmaso F, Quadroni S, Compare S, Gentili G, Crosa G, 2019. Benthic diatoms as bioindicators of environmental alterations in different watercourses of northern Italy. Environ. Monit. Assess. 191:1-17. DOI: https://doi.org/10.1007/s10661-019-7290-x

Stenger-Kovács C, Lengyel E, Sebestyén, V, Szabó B, 2020. Effects of land use on streams: traditional and functional analyses of benthic diatoms. Hydrobiologia 847:2933–2946. DOI: https://doi.org/10.1007/s10750-020-04294-y

Stevenson RJ, Bothwell ML, Lowe RL, 1996. Algal ecology: Freshwater benthic ecosystems. Academic Press: 753 pp.

Torrisi M, Dell'Uomo A, 2006. Biological monitoring of some Apennine rivers (central Italy) using the diatom-based eutrophication / pollution index (epi-d) compared to other European diatom indices. Diatom Res. 21:159-174. DOI: https://doi.org/10.1080/0269249X.2006.9705657

Torrisi M, Dell'Uomo A, Ector L, 2008. Assessment of quality of the Apennine rivers (Italy) using the diatom indices: The River Foglia. Cryptogamie Algol. 29:45-61.

Trábert Z, Duleba M, Bíró T, Dobosy P, Földi A, Hidas A, Kiss KT, Óvári M, Takács A, Várbíró G, Záray G, Ács É, 2020. Effect of land use on the benthic diatom community of the Danube River in the Region of Budapest. Water 12:479. DOI: https://doi.org/10.3390/w12020479

Szczepocka E, Nowicka-Krawczyk P, Knysak P, Żelazna-Wieczorek J, 2016. Long term urban impacts on the ecological status of a lowland river as determined by diatom indices. Aquat. Ecosyst. Health 19:19-28. DOI: https://doi.org/10.1080/14634988.2016.1145029

U.S. Environmental Protection Agency, 2016. National rivers and streams assessment 2008‐2009: A Collaborative Survey (EPA 841‐R‐16/007). Washington, U.S. Environmental Protection Agency.

Vollenweider RA, 1968. Water management research. Paris, OECD: 183 pp.

Vollenweider RA, 1976. Advances in defining critical loading levels for phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobiol. 33:53-83.

Wagenhoff A, Liess A, Pastor A, Clapcott JE, Goodwin EO, Young RG, 2017. Thresholds in ecosystem structural and functional responses to agricultural stressors can inform limit setting in streams. Freshw. Sci. 36:178-194. DOI: https://doi.org/10.1086/690233

Yang Y, Cao JX, Pei GF, Liu GX, 2015. Using benthic diatom assemblages to assess human impacts on streams across a rural to urban gradient. Environ. Sci. Pollut. R. 22:18093-18106. DOI: https://doi.org/10.1007/s11356-015-5026-1

Additional Files

80 Years of the Journal of Limnology
diatom index, ICMi, LIMECO, nutrient thresholds, river macrotypes, WFD
  • Abstract views: 113

  • PDF_early view: 17
  • Annex 1: 0
How to Cite
Bona F, La Morgia V, Fenoglio S, Morandi L, Falasco E. Diatom communities and ecological status classification in the upper Po River basin. J Limnol [Internet]. 2021 Jul. 13 [cited 2021 Jul. 28];. Available from: https://jlimnol.it/index.php/jlimnol/article/view/2025

Most read articles by the same author(s)