Research Article

Determining reference conditions of hemiboreal lakes in Latvia, NE Europe: a palaeolimnological approach

¹ Department of Geography, Faculty of Geography and Earth Sciences, University of Latvia, Riga, Jelgavas street 1, 1004, Latvia
² Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, Helsinki 00014, Finland
³ Lake and Peatland Research Centre, Alojas district, Puikule, Purvisi, Latvia
⁴ Institute of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
⁵ Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland
⁶ Oeschger Centre for Climate Change Research, University of Bern, Falkenplatz 16, CH-3013 Bern, Switzerland
⁷ Institute of Biology, University of Latvia, Miera iela 3, Salaspils 2169, Latvia

^* Corresponding author: normunds.stivrins@lu.lv

Received: 28 November 2017
Accepted: 7 May 2018

Abstract

The current status of a lake can be evaluated via monitoring, but such data can only provide information about the last few decades to a century at best. In most cases, the natural state of a lake cannot be ascertained. This is even more challenging if the apparent anthropogenic effects on the environment over the last millennia are considered. We used data on fossil algae from five evenly distributed hemiboreal lakes in geographically different regions in Latvia, NE Europe to assess the amount of compositional change or turnover (i.e., the beta-diversity) in the algae datasets for the last 2000 years by using a Detrended Canonical Correspondence Analysis. Our results show that the algae turnover increases towards the present day with distinct shifts during times characterised by extensive and intensive agriculture establishment, and political and economic changes. Because the anthropogenic impact on the landscape and lakes before AD 1200 was relatively minor, we propose that algae composition at that time can be assumed to represent the natural reference conditions for most Latvian lakes.