The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate

Abstract

Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacialinterglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 14.7-6.9 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, followed by a post-Medieval loss of diversity which is consistent with cooling, but not definitive. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced Correspondence to: J. M. Reed (j.m.reed@hull.ac.uk) variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom accumulation data in future studies.

Differential resilience of ancient sister lakes Ohrid and Prespa to environmental disturbances during the Late Pleistocene

“…Moreover, they are remarkably well-preserved in the sediment records of lakes Ohrid and Prespa (e.g., Reed et al, 2010;Cvetkoska et al, 2012Cvetkoska et al, , 2014Cvetkoska et al, , 2015aZhang et al, 2016). These aspects make diatoms excellent proxies for studying how the lakes responded to environmental disturbances.…”

The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid

“…Apparently close correlation with geochemical proxies, and carbonate in particular, suggests that major shifts in diatom-species assemblage composition are driven by glacial/interglacial climate cycles in the latter part of the record. Our previous diatom-based palaeoclimate analysis of sequences spanning the last 134 ka, from the last interglacial to present (Wagner et al, 2009;Reed et al, 2010;Cvetkoska et al, 2012), demonstrates the high sensitivity of diatoms to glacial/interglacial and interstadial climate change, driven primarily by temperature-induced productivity shifts. This is supported by modern ecological data, which define the epilimnetic vs. hypolimnetic life habit of dominant planktonic taxa (Allen and Ocevski, 1976).…”

Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep and oligotrophic Lake Ohrid (Macedonia and Albania)

“…Diatom results are compared with sedimentological and geochemical data from the same core (Wagner et al, 2012;Lacey et al, 2015). We also compare core Co1262 diatom results with low-resolution diatom data from core Lz1120 (southeastern Lake Ohrid; Wagner et al, 2009), core Co1202 (northeastern Lake Ohrid; Reed et al, 2010;Cvetkoska et al, 2012), the DEEP site (central Lake Ohrid; Cvetkoska et al, 2015) and core 9 (north-central Lake Ohrid; Roelofs and Kilham, 1983) and with palynological data from the region (Wagner et al, 2009;Panagiotopoulos et al, 2013).…”

“…Quantitative climate reconstruction methods have their own strengths and weaknesses Juggins and Birks, 2012), and pollen-based temperature reconstructions can show different patterns and amplitudes of change depending on the technique used Peyron et al, 2013). Deep Lake Ohrid, for which no major lake-level change during the Lateglacial and Holocene has been reported (Wagner et al, 2009;Reed et al, 2010), is arguably an ideal site for using palaeolimnological proxies such as diatoms to improve understanding of temperature change in this region.…”

“…To date, diatom-based palaeoclimate research in Lake Ohrid has focused on low-resolution analysis of response to the last glacial-interglacial cycle (Wagner et al, 2009;Reed et al, 2010;Cvetkoska et al, 2012Cvetkoska et al, , 2015. Fluctuations in diatom composition between glacial or stadial and interglacial or interstadial stages have suggested a strong and simple response to temperature-induced changes in lake productivity.…”