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P. Tarrats, M. Rieradevall, N. Prat, M.P. Mata, M. Morellón, J. Vegas,
J. Sánchez, B.L. Valero, A. Moreno
Geneva5-10 July 2015
: Global Change in Mountain Lakes
Study and understand the present to explain the past
“Paleoecological reconstructions using biological registers needa good knowledge of the actual ecology and autoecology of thespecies” (Birks and Birks, 2004).
“It is important to combine paleoecological data with thoseobtained from instrumental series and collected from ecologicaltechniques 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
To characterize the modern chironomid community of Enol Lake. To evaluate which factors are responsible of changes in
community:
Abundance
Composition
We aim to study and understand the actual Chironomidae community in order to improve theinterpretation of the chironomid subfossil record
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
Lake type Warm monomictic
Trophic state Oligotrophic
Lake water chemistry
Hard water HCO3- & Ca
Alkaline
Low nutrientcontents
NO32-, NO2-
NH4+ &PO43-
Enol Lake
0
2
4
6
8
10
12
14
16
18
20
22
0 25 50 75 100 125 150
De
pth
(m)
DO (%)
May
July
September
November
0
2
4
6
8
10
12
14
16
18
20
22
5 10 15 20 25
De
pth
(m)
T (ºC)
May
July
September
November
No depth patternsTemperature 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CLAM-1 (unpublished data)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 showingsampling metods and Ekman grab.
A total of 204 samples were analyzed
Samples cleaningand sediment
sieving
Chironomidaelarvae morphotype
classification
Macroinvertebratesorting (Family
level)
Chironomidaelarvae mounting
and identification
-KOH digestion-Mounting in slides
-Identification undera 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 thedata analysis 16 species
Chironomus plumosus, Einfeldia pagana, Procladius choreus and Paratanytarsus bituberculatus from Enol Lake.
Profundal Littoral
Are there significant differences between… (ANOSIM Test)
•Years p-value=0.57
• Samplings p-value=0.26
•Depths p-value= 0.01 R= 0.6
DCA length of gradients <3
Redundancy Analysis (RDA)
Environmental variables:
•Temperature• Dissolved Oxygen• pH• Depth•Chara
Speciesmatrix
Stability of the community
Littoralzone
Profundalzone
Chara zone
RDA Axis 1
RD
A A
xis
2
RDA analysis of Enol Lake data. Axis 1 explains the29.9% of species variance and the 65.1 % of species –environment relation variance. Axis 2 explains the10.3% of species variance and the 22.6% of species-environment relation variance.
Chara-related taxa
Always high DO values
Profundal taxa
Always no Chara and low DO
Littoral taxa and sub-littoral taxa
-Great variability in Chara-High DO values, although less than
in Chara-related taxa
Chara and Oxygenmain drivers
The community is quite stable: there are not significantdifferences along the year and between years.
Changes in the Chironomidae community composition andabundance are mainly driven by the presence of Chara andchanges 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 interpretingthe subfossil record.