Lake archives: reconstructing long-term response to global change. Lami Andrea

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1 Lake archives: reconstructing long-term response to global change Lami Andrea CNR- Is1tuto per lo Studio degli Ecosistemi (ISE) Verbania, Italia Climate variability in Italy during the last two millennia Italy 2k

2 Proxy- records Virtually all biological, chemical and physical processes that are studied in limnology leave evidence in sediments, but sedimentary records are subject to informa1on loss because of many factors, including those that affect variable distribu1on of sedimentary cons1tuents and post- deposi1onal changes (Cohen, 2003). Sediments and sedimentation Glass shard Tephras Volcano Carbonaceous particles Urban area Tributaries 40 µm Dusts Slump Redissolution Pollutants Bioturbation Resuspension d) Carbonaceous Particles Biochemical laminae Clastic laminae Climate variability in Italy during the last two millennia Italy 2k

3 Sediment: an ecosystem s memory a) b) Lake sediment cores are taken using corers operated from a boat or platform (Photo a). Cores are then cut longitudinally to reveal their internal structure (Photo b). Aims To provide high-resolution, paleoenvironmental (e.g. ph, P) and paleoclimatic inferences using a range of chemical and biological proxies. To measure the temporal effect of climate change and anthropogenic impact on lake ecosystem structure and processes. To establish historical data that can be used to calibrate and validate numerical models. Climate variability in Italy during the last two millennia Italy 2k

4 Lake Maggiore cores Proxy-records Trophic status Organic matter N, P, CaCO 3 Biogenic silica Clastic inputs Metals Water depth 25 m 59 m 148 m 113 m 120m Glacier fluctuations Erosion Pigments Pigmenti Cladocera Biodiversity Trophic status Ostracods Chironomids Water temperature Lake water fluctuations Trophic status Primary production UV radiations Redox conditions Diatoms ph Phosphorus Salinity Geochemical and biological indicators we commonly analyze in sediment cores. Climate variability in Italy during the last two millennia Italy 2k

5 Climate variability in Italy during the last two millennia Italy 2k December 1st-2nd Accademia dei Lincei, Roma

6 One example is the increase in small planktonic diatoms with climate warming (e.g. Cyclotella sensu lato, including representa1ves of Cyclotella, Discostella, and Punc1culata) (Ru hland et al. 2008). Many studies have reported their increase and, in some cases, a concomitant decline of large filamentous diatoms (e.g. Aulacoseira taxa). Increase in the length of the growing season and periods of high stability of the water column (compared to those of intense mixing). These species, as any other respond neither directly to weather nor climate, but to proximal growing condi1ons hytoplankton species, respond (nutrients, light, temperature, mixing regimes, grazing), which can appear or disappear under different combina1ons of actors forcing the lake system. Therefore, Cyclotella or any other diatom taxon cannot be used as a lake thermometer by itself. Ruhland K, Paterson AM, Smol JP (2008) Hemispheric-scale patterns of climate-related shifts in planktonic diatoms from North American and European lakes. Glob Change Biol 14: Climate variability in Italy during the last two millennia Italy 2k

7 SubmiVed to Ecology LeVers Increases in atmospheric temperature and nutrients from land are thought to results in the expansion of harmful cyanobacteria in lakes worldwide, yet to date there has been no quan1ta1ve synthesis of long- term trends. To test whether cyanobacteria have increased over the past ~200 years and evaluate the rela1ve influence of poten1al causal mechanisms, we synthesized 108 highly- resolved sedimentary 1me series and 18 decadal- scale monitoring records from north temperate- subarc1c lakes. We demonstrate that 1) cyanobacteria have increased significantly since ca CE 2) they have increased dispropor1onately rela1ve to other phytoplankton 3) cyanobacteria increased more rapidly post ca CE. 4) Varia1on among lakes in the rates of increase was best explained by nutrient concentra1on, and temperature was of secondary importance. Analysis of fossil records containing biomarkers of both phytoplankton groups showed that non-linear increases after ca CE were significantly (χ 2 year-pigment =14.3, P<0.0001) and disproportionately larger for cyanobacteria than for diatoms. Climate variability in Italy during the last two millennia Italy 2k

8 Climate variability in Italy during the last two millennia Italy 2k

9 The ques?on: Reference condi1on for phosphorus in the large Italian lakes Paleolimnological apporach: Fossil diatoms Sedimentary pigments Climate variability in Italy during the last two millennia Italy 2k

10 Maggiore Garda Asterionella formosa Aulacoseira islandica Diatoma tenuis Cyclotella comensis Fragilaria crotonensis Stephanodiscus minutulus & S. hantzschii

11 89% 89% 96% 87% 97% 96% Cyclotella comensis C. cyclopuncta 95% 95% Climate variability in Italy during the last two millennia Italy 2k

12 Climate variability in Italy during the last two millennia Italy 2k

13 100 Segrino Maggiore Como Garda Iseo Sirio 75 Inferred TP (ppb) P D P D P D P D P D P D Climate variability in Italy during the last two millennia Italy 2k

14 Climate variability in Italy during the last two millennia Italy 2k

15 150 Viverone Varese P Pusiano N - limited Comabbio P - limited 1 : 16 Albano N

16 150 Viverone Varese P Pusiano N - limited Comabbio P - limited 1 : 16 Albano N

17 P Viverone N - limited Pusiano Varese Comabbio 0 Inferred TP (ppb) Albano N - limited N Depth (cm) 40 P - limited diatoms pigments 60 Pusiano 80

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20 Lago Maggiore Lago di Avigliana 2008 Lago Lugano 2010 Bolsena Bracciano, Albano Nemi (Paliclas 1994) Varese, Comabbio, Monate, Pusiano, Tovel, 2001 Colbricon, 2010 Ledro, 2012 Garda 2011 Mon1cchio 2006 NEXTDATA Special project: lake

21 Local human perturba1ons increase lakes vulnerability to climate changes - A pan- - European test 1. comparing the responses of pelagic biological communi1es to climate change between the 15 lakes and quan1fying the synchronicity or in contrast the idiosyncracy in pelagic responses to CC 2. To assess whether and to what extent the variability of responses depend on geomorphological characteris1cs and intensity of local human pressures of lakes.

22 ... take-home messages paleolimnology relies on interdisciplinary approaches to compensate for informa1on loss, and to resolve the complexity of differen1al interpreta1ons about ecosystem changes and driving forces. (Withmore Jlimnol 2014) morphologically comparable ecosystems under similar climate forcing are not evenly sensi1ve and these differences in vulnerability to climate warming depend on local stressors. Contribute to the debate about the predictability of the impacts of climate change on ecosystems understanding the role of local vs global forcing when extrapola1ng from one site to another.

23 with contribu1on of people CNR- Is1tuto per lo Studio degli Ecosistemi (ISE) R. Piscia M. Manca P. Guilizzoni S. Musazzi A. Marche1o S. Gerli C. Barbante J. Gabrielli M. Toloi Limnology and Fresh Water Ecology research group Fondazione Edmund Mach, S. Michele (TN) W. Finsinger M.E. Perga IPER- RETRO - Impact des perturba1ons sur les réseaux trophiques en lacs : approche paléo- écologique Laurent Millet - UMR 6249 Chrono- environnement Besançon, France Zofia E. Taranu McGill University Canada Centre de Bio- Archeologie et d Ecologie (CBAE) CNR- IDPA, Venezia Thanks for your attention!