P. Tarrats, M. Rieradevall, N. Prat, M.P. Mata, M. Morellón, J. Vegas, J. Sánchez, B.L. Valero, A. Moreno Geneva 5-10 July 2015 : Global Change in Mountain Lakes Study and understand the present to explain the past “Paleoecological reconstructions using biological registers need a good knowledge of the actual ecology and autoecology of the species” (Birks and Birks, 2004). “It is important to combine paleoecological data with those obtained from instrumental series and collected from ecological techniques used in the study of actual ecosystems conditions” (Peng et al., 2011) CHIRONOMIDAE What? . Insecta:Diptera . Aquatics and semi-aquatic . Larvae inhabit lake’s benthos . In paleo: larvae head capsules Why? . High taxonomic diversity and abundances . The presence of different species reflects different ecological conditions . Taxonomy (identification): . Preservation (Paleo): Chironomid life cycle and larvae We aim to study and understand the actual Chironomidae community in order to improve the interpretation of the chironomid subfossil record To characterize the modern chironomid community of Enol Lake. To evaluate which factors are responsible of changes in community: . Abundance . Composition Enol Lake Location North Spain (Asturias) Picos de Europa National Park Origin Glacial Altitude 1070 m asl Max depth 22 m Surface Area 12.2 ha Location map of Enol Lake Enol Lake T (ºC) DO (%) 5 10 15 20 25 0 25 50 75 100 125 150 Lake type Warm monomictic 0 0 Trophic state Oligotrophic 2 2 4 4 6 6 Lake water chemistry 8 8 Hard water HCO - & Ca ) (m) 3 10 (m 10 12 12 Depth Alkaline Depth 2- 2- 14 14 Low nutrient NO3 , NO 16 May 16 contents NH4+ &PO 3- May 4 July 18 18 July September 20 20 September November November 22 22 No depth patterns Temperature and DO profiles of 4 samplings (May, July, September and November) of 2013 in Enol Lake. Project CLAM-1 (unpublished data) 8 fieldwork samplings in 2013 and 2014: May, July, September and November. Depth transect: samples every 2m of depth, 3 replicates Profundal zone: Ekman grab (15cm2) Littoral zone: kick-sampling (1m2) Profile of Enol Lake showing sampling metods and Ekman grab. A total of 204 samples were analyzed Samples cleaning Macroinvertebrate Chironomidae Chironomidae and sediment sorting (Family larvae morphotype larvae mounting sieving level) classification and identification -KOH digestion -Mounting in slides -Identification under a microscope (400x) A total of 14,248 Chironomidae larvae were identified 26 species, 4 sub-families: . Chironominae ▪ Tribe Chironomini: 11 species ▪ Tribe Tanytarsini: 4 species . Orthocladiinae: 7 species . Tanypodinae: 3 species . Prodiamesinae: 1 specie Rare taxa (<2% in at least 2 samples) were removed in the data analysis 16 species Chironomus plumosus, Einfeldia pagana, Procladius choreus and Paratanytarsus bituberculatus from Enol Lake. Profundal Littoral Environmental variables: • Temperature • Dissolved Oxygen Species • pH matrix DCA length of gradients <3 • Depth • Chara Redundancy Analysis (RDA) Are there significant differences between… (ANOSIM Test) •Years p-value=0.57 Stability of the community • Samplings p-value=0.26 •Depths p-value= 0.01 R= 0.6 Chara zone Profundal RDA Axis Axis 2 RDA zone Littoral RDA analysis of Enol Lake data. Axis 1 explains the zone 29.9% of species variance and the 65.1 % of species – environment relation variance. Axis 2 explains the 10.3% of species variance and the 22.6% of species- RDA Axis 1 environment relation variance. Chara and Oxygen main drivers Chara-related taxa Always high DO values Littoral taxa and sub-littoral taxa -Great variability in Chara -High DO values, although less than in Chara-related taxa Profundal taxa Always no Chara and low DO The community is quite stable: there are not significant differences along the year and between years. Changes in the Chironomidae community composition and abundance are mainly driven by the presence of Chara and changes in the DO content . This results will allow us to improve the interpretation and inference of the paleo record. ▪ Analyse the recent paleo record (1cm of sediment) at every depth to understand the deposition of the chironomid head capsules. ▪ Analyse two sediment cores . ▪ Apply what we are learning from these studies when interpreting the subfossil record..