THETHE INFLUENCE EFFECT OF OF NATURAL GROWTH VARIABILITY CONDITIONS ON ON PHYSICO-MECHANICALTHE ASSESSMENT OF ECOLOGICAL PROPERTIES STATUS OF SCOTS OF PINESHALLOW (Pinus sylvestris LAKES L.) WOOD IN ESTONIA LOODUSLIKUKASVUTINGIMUSTE MUUTLIKKUSE MÕJU MÕJU HARILIKU MADALATE MÄNNI JÄRVEDE (PinusÖKOSEISUNDI sylvestris L.) PUIDU HINDAMISELE FÜÜSIKALIS- MEHAANILISTELE OMADUSTELE EESTIS LEAREGINO TUVIKENE KASK AA Thesisthesis for applying for thefor degreeapplying of forDoctor the degree of Philosophy of in Forestry Doctor of Philosophy in Applied Biology Väitekiri Filosoofiadoktorifilosoofiadoktori kraadi kraadi taotlemiseks taotlemiseks rakendusbioloogia metsanduse erialal erialal Tartu 20152018 Eesti Maaülikooli doktoritööd Doctoral Theses of the Estonian University of Life Sciences THE EFFECT OF NATURAL VARIABILITY ON THE ASSESSMENT OF ECOLOGICAL STATUS OF SHALLOW LAKES LOODUSLIKU MUUTLIKKUSE MÕJU MADALATE JÄRVEDE ÖKOSEISUNDI HINDAMISELE LEA TUVIKENE A thesis for applying for the degree of Doctor of Philosophy in Applied Biology Väitekiri Filosoofiadoktori kraadi taotlemiseks rakendusbioloogia erialal Tartu 2018 Institute of Agricultural and Environmental Sciences Estonian University of Life Sciences According to the verdict 6-14/13-9 of December 12, 2017, the Doctoral Committee for Environmental Sciences and Applied Biology of the Estonian University of Life Sciences has accepted the thesis for the defence of the degree Doctor of Philosophy in Applied Biology. Opponent: Prof. Brigitte Nixdorf, Dr. rer. nat. habil. Brandenburg University of Technology, Germany Pre-opponent: Fabio Ercoli, PhD Estonian University of Life Sciences, Estonia University of Jyväskylä, Finland Supervisor: Peeter Nõges, PhD Estonian University of Life Sciences, Estonia Defence of the thesis: Estonian University of Life Sciences, Karl Ernst von Baer House, Veski 4, Tartu, on 16th of February 2018, at 13.15. The English and Estonian was edited by Tiina Nõges. Publication of this thesis is supported by the Estonian University of Life Sciences. © Lea Tuvikene 2018 ISBN 978-9949-629-13-8 (publication) ISBN 978-9949-629-14-5 (pdf) CONTENTS LIST OF ORIGINAL PUBLICATIONS .................................................7 ABBREVIATIONS .......................................................................................9 GRAPHICAL ABSTRACT .......................................................................11 1. INTRODUCTION .................................................................................12 2. AIMS AND HYPOTHESES OF THE STUDY ..............................14 3. REVIEW OF THE LITERATURE ....................................................17 3.1. Principles of ecological status assessment in lakes .....................17 3.2. Confidence of status classes and risk of misclassification due to natural variability of indicators ................................................19 3.3. Types of natural variability ............................................................20 3.3.1. Spatial variation ........................................................................20 3.3.2. Temporal variation ...................................................................22 3.3.2.1. Daily variation ....................................................................22 3.3.2.2. Seasonal variation ..............................................................23 3.3.2.3. Year-to-year variation ........................................................24 3.3.2.4. Multi-annual periodicity ....................................................24 3.3.2.5. Evolutionary and climate-related trends .......................25 3.3.2.6. System shifts .......................................................................28 3.3.3. Combining data with different variability ............................30 3.4. Anthropogenic influence and its distinction from natural variability ..................................................................................................31 3.4.1. Challenges ..................................................................................32 3.4.1.1. Weak trends and the question of causality ....................32 3.4.1.2. Common chains of influence .........................................32 3.4.1.3. Lag periods between impact and response ...................34 3.4.1.4. Climate sensitivity of lake type parameters and status indicators ...............................................................................36 3.4.2. Ways forward .............................................................................39 3.4.2.1. Monitoring of reference sites ..........................................39 3.4.2.2. Coherence studies ............................................................39 3.4.2.3. Comparison of contrasting years ....................................42 3.4.2.4. Detrending of long-term data for known sources of variability .....................................................................................43 5 3.4.2.5. Using multivariate statistics .............................................44 3.4.2.6. Model calculations .............................................................45 4. MATERIAL AND METHODS ...........................................................47 5. RESULTS ..................................................................................................49 5.1. Effect of water level and seasonality on water quality parameters in Võrtsjärv (I) ....................................................................49 5.2. Spacial and annual variability of environmental and phytoplankton indicators of Võrtsjärv (II) ........................................50 5.3. Contemporary climatic, hydrological and loading trends in Võrtsjärv and Peipsi (III) ..................................................................52 5.4. Relationships between DOC and other water and environmental variables (IV) ..................................................................53 5.5. Phytoplankton productivity in shallow lakes (V) .........................54 5.6. Effects of coloured dissolved organic matter on the attenu- ation of photosynthetically active radiation in Lake Peipsi (VI) ......54 6. DISCUSSION AND SYNTHESIS OF ORIGINAL PUBLICATIONS ........................................................................................55 6.1. Distinction of effects of natural factors on common water quality indicators in shallow lakes .........................................................55 6.1.1. Influence of water level and seasonality I( ) ..........................55 6.1.2 Spatial and temporal variability (II) ........................................58 6.2. Contemporary climatic, hydrological and loading trends at shallow lakes Peipsi and Võrtsjärv (III) ...............................................60 6.3. Underwater light field and its determinants in shallow lakes (IV, V, VI) .......................................................................................63 7. CONCLUSIONS ...................................................................................67 REFERENCES ..........................................................................................69 SUMMARY IN ESTONIAN ..................................................................102 ACKNOWLEDGEMENTS ...................................................................107 ORIGINAL PUBLICATIONS...............................................................109 CURRICULUM VITAE ...........................................................................213 ELULOOKIRJELDUS ............................................................................220 6 LIST OF ORIGINAL PUBLICATIONS I. Tuvikene, L., Nõges, T. & Nõges, P. 2011. Why do phytoplankton species composition and “traditional” water quality parameters indicate different ecological status of a large shallow lake? Hydrobiologia, 660(1): 3–15, doi: 10.1007/s10750-010-0414-5. II. Nõges, P. & Tuvikene, L. 2012. Spatial and annual variability of environmental and phytoplankton indicators in Lake Võrtsjärv: implications for water quality monitoring. Estonian Journal of Ecology, 61(4): 227–246, doi: 10.3176/eco.2012.4. III. Nõges, T., Tuvikene, L. & Nõges, P. 2010. Contemporary trends of temperature, nutrient loading and water quality in large lakes Peipsi and Võrtsjärv, Estonia. Journal of Aquatic Ecosystem Health and Management, 13(2): 143–153, doi: 10.1080/14634981003788987 IV. Toming, K., Kutser, T., Tuvikene, L., Viik, M. & Nõges, T. 2016. Dissolved organic carbon and its potential predictors in eutrophic lakes. Water Research, 102: 32−40, doi: 10.1016/j. watres.2016.06.012. V. Kauer, T., Arst, H., Nõges, T. & Tuvikene, L. 2009. Estimation of the phytoplankton productivity in three Estonian lakes. Estonian Journal of Ecology, 58(4): 297–312, doi: 10.3176/eco.2009.4.05. VI. Reinart, A., Paavel, B. & Tuvikene, L. 2004. Effects of coloured dissolved organic matter on the attenuation of photosynthetically active radiation in Lake Peipsi. Proceedings of the Estonian Academy of Sciences. Biology, Ecology, 53(2): 88–105. 7 Author’s contribution to the papers: Paper I II III IV V VI TK, PN, KT; LT, TN, HA, AR, Concept LT, TN, PN PN LT, BP, LT TN TKu TN TN, TK, Design PN PN KT AR PN LT AR, Data LT, LT, LT, LT, TK, LT, collection PN, * PN, * PN, * MV, * LT BP Data LT, PN, TN, KT TK AR analyses PN LT PN TK, PN, TN, KT, AR, Manuscript PN, HA, LT, PN, LT, LT, preparation LT LT, TN LT TN, + BP TN LT – Lea Tuvikene; TN – Tiina Nõges; PN – Peeter Nõges; KT – Kaire Toming; TKu – Tiit Kutser; MV – Malle Viik; TK – Tuuli