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

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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CLAM-1 (unpublished data)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.