Universität zu Köln

Zhang, X. S., Reed, J. M., Lacey, J. H., Francke, A., Leng, M. J., Levkov, Z. and Wagner, B. (2016). Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep and oligotrophic Lake Ohrid (Macedonia and Albania). Biogeosciences, 13 (4). S. 1351 - 1366. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 1726-4189

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Abstract

Lake Ohrid (Macedonia and Albania) is a rare example of a deep, ancient Mediterranean lake and is a key site for palaeoclimate research in the northeastern Mediterranean region. This study conducts the analysis of diatoms as a proxy for Lateglacial and Holocene climate and environmental change in Lake Ohrid at a higher resolution than in previous studies. While Lake Ohrid has the potential to be sensitive to water temperature change, the data demonstrate a highly complex diatom response, probably comprising a direct response to temperature-induced lake productivity in some phases and an indirect response to temperature-related lake stratification or mixing and epilimnetic nutrient availability in others. The data also demonstrate the possible influence of physical limnological (e.g. the influence of wind stress on stratification or mixing) and chemical processes (e.g. the influence of catchment dynamics on nutrient input) in mediating the complex response of diatoms. During the Lateglacial (ca. 12300-11800 cal yr BP), the low-diversity dominance of hypolimnetic Cyclotella fottii indicates low lake productivity, linked to low water temperature. Although the subsequent slight increase in small, epilimnetic C. minuscula during the earliest Holocene (ca. 11800-10600 cal yr BP) suggests climate warming and enhanced stratification, diatom concentration remains as low as during the Lateglacial, suggesting that water temperature increase was muted across this major transition. The early Holocene (ca. 10600-8200 cal yr BP) is characterised by a sustained increase in epilimnetic taxa, with mesotrophic C. ocellata indicating high water-temperature-induced productivity between ca. 10600-10200 cal yr BP and between ca. 9500-8200 cal yr BP and with C. minuscula in response to low nutrient availability in the epilimnion between ca. 10200-9500 cal yr BP. During the middle Holocene (ca. 8200-2600 cal yr BP), when sedimentological and geochemical proxies provide evidence for maximum Holocene water temperature, anomalously low C. ocellata abundance is probably a response to epilimnetic nutrient limitation, almost mimicking the Lateglacial flora apart from the occurrence of mesotrophic Stephanodiscus transylvanicus in the hypolimnion. During the late Holocene (ca. 2600 cal yr BP-present), high abundance and fluctuating composition of epilimnetic taxa are probably a response more to enhanced anthropogenic nutrient input, particularly nitrogen enrichment, than to climate. Overall, the data indicate that previous assumptions concerning the linearity of diatom response in this deep, ancient lake are invalid, and multi-proxy analysis is essential to improve understanding of palaeolimnological dynamics in future research on the long, Quaternary sequence.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Zhang, X. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Reed, J. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lacey, J. H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Francke, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Leng, M. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Levkov, Z. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wagner, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-292331
DOI:	10.5194/bg-13-1351-2016
Journal or Publication Title:	Biogeosciences
Volume:	13
Number:	4
Page Range:	S. 1351 - 1366
Date:	2016
Publisher:	COPERNICUS GESELLSCHAFT MBH
Place of Publication:	GOTTINGEN
ISSN:	1726-4189
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MEDITERRANEAN REGION; IOANNINA BASIN; PRESPA; POLLEN; EUTROPHICATION; RECONSTRUCTION; CYCLOTELLA; COMMUNITY; HISTORY; IMPACT Multiple languages Ecology; Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/29233