The trophic history of Sacrower See (NE Germany)

Are pristine lakes always nutrient poor?

The trophic history of Sacrower See (NE Germany)

Kirilova E. P.

, Heiri O.

, Enters D.

, Cremer H.

, Lotter A. F.

, Zolitschka B.

, and Hübener T.

1Palaeoecology, Laboratory of Palaeobotany and Palynology, Utrecht University, The Netherlands, ²UMR CNRS 5204, EDYTEM, Université de Savoie, France, ³Netherlands Organization, for Applied Scientific Research TNO, Utrecht, The Netherlands, ⁴Geopolar, Geomorphology and Polar Research, University of Bremen, Germany, ⁵Department of Biodiversity, University of Rostock, Germany

Age (cal. BP)

0 2000 4000 6000 8000 10000 12000 14000

Depth (cm)

0 100 200 300 400 500 600 700 800 900 1000 1100 1200

Onset of modern varve formation

Onset of Holocene

Laacher See tephra

*

*

NATURAL EUTROPHICATION

DURING THE COLD YOUNGER DRYAS (12 700 - 11 600 cal. BP)

During cold periods prolonged ice cover may lead to reduced mixing of lakes with increased oxygen depletion, which leads to prolongated phases of anoxia and can consequently prompt phosphorus release from the sediments.

CULTURAL EUTROPHICATION

FROM 3000 cal. BP TO THE PRESENT

The trophic state was regulated by human activities, hydrological connection with the eutrophic river Havel, hypolimnetic anoxia and phosphorus loading. Since AD 1871 the lake sediments has been annually

laminated.

EU WATER FRAMEWORK DIRECTIVE

IMPLICATIONS

We conclude that the definition of reference conditions should take into account climatic influence on pristine lakes, in the periods without human impact.

We suggest that the early to mid- Holocene represents a sensible

TP reference condition for lowland lakes that have a long history of anthropogenic and natural eutrophication.

Stephanodiscus parvus

5µm

Stephanodiscus alpinus Stephanodiscus neoastraea

Aulacoseira islandica Cyclotella cyclopuncta

Monodiamesa Limnophyes

Corynoneura Tanytarsus

Tanytarsus

Age (cal. BP)

µg/l

Total phosphor us

Total diatom accumulation

rates

Chrysophyte cycts Fragilaria s.l.

Periphyton Plankton

(10⁷ valves/cm²/yr)

Hypertrophic

Eutrophic

Mesotrophic

Oligotrophic Indifferent

Unknown

Profundal taxa

(hc/100 cm²/yr) Littoral taxa

Late Glacial

Younger Dryas cold phase

Early Holocene Middle Holocene

Late Holocene

C h i r o n o m i d s

Trophic groups Habitat forms

13000 12000 11000 10000

9000 8000 7000 6000 5000 4000 3000 2000 1000 0

40 80 50 150 20 20 60 20 60 100 40 20 60 20 60 20 20 20 60 20 60 MESOTROPHIC

ANOXIC HYPOLIMNION HYPERTROPHIC

ANOXIC HYPOLIMNION MESOTROPHIC

OXIC HYPOLIMNION

MESO - TO OLIGOTROPHIC OXIC HYPOLIMNION

EU - TO HYPERTROPHIC ANOXIC HYPOLIMNION

D i a t o m s

Habitat forms

20

10

0 500 m

105 1520 2530 35 Depth (m)

Sacrower See Sacrower See

54°N

6°E6 10°E 14°E

52°N

48°N 50°N

- Altitude 29.5 a.s.l.

- Depth 38m

- Eutrophic waters

Sacrower See Aim Sediment core

Reconstruction tools

Total phosphorus reconstruction (WAPLS) is based on diatoms.

Hypolimnetic oxygen availability is assessed by chironomids.

To assess the lake’s baseline conditions before the onset of cultural eutrophication and to reconstruct

the past effects of natural and anthropogenic factors on the lake’s nutrient concentrations.

Transfer function

The TP inferences were estimated using a transfer function based on weighted-averaging partial least

squares regression and 429 modern diatom samples.