Climate and land-use as the main drivers of recent environmental change in a mid-altitude mountain lake, Romanian Carpathians

Abstract

Recent decades have been marked by unprecendented environmental changes which threaten the integrity of freshwater systems and their ecological value. Although most of these changes can be attributed to human activities, disentagling natural and anthropogenic drivers remains a challenge. In this study, surface sediments from Lake Ighiel, a mid-altitude site in the Carpathian Mts (Romania) were investigated following high-resolution sedimentological, geochemical, environmental magnetic and diatom analyses supported by historical cartographic and documentary evidence. Our results suggest that between 1920 and 1960 the study area experienced no significant anthropogenic impact. An excellent correspondence is observed between lake proxy responses (e.g., growth of submerged macrophytes, high detrital input, shifts in diatom assemblages) and parameters tracking natural hydroclimate variability (e.g., temperature, NAO). This highlights a dominant natural hydroclimatic control on the lacustrine system. From 1960 however, the depositional regime shifted markedly from laminated to homogenous clays; since then geochemical and magnetic data document a trend of significant (and ongoing) subsurface erosion across the catchment. This is paralleled by a shift in lake ecosystem conditions denoting a strong response to an intensified anthropogenic impact, mainly through forestry. An increase in detrital input and marked changes in the diatom community are observed over the last three decades, alongside accelerated sedimentation rates following enhanced grazing and deforestation in the

Carbon accumulation rates of Holocene peatlands in central–eastern Europe document the driving role of human impact over the past 4000 years

“…These conclusions are supported by other parameters such as chironomid-based summer temperatures and testate-amoebaderived measures of wetness (Onac et al, 2002;Schnitchen et al, 2006;Tóth et al, 2015). These contrasting trends reflect seasonal responses to changing local moisture sources, not only in the Carpathians but also throughout the Balkans (Haliuc et al, 2017;, indicating the particularities and dynamics of the regional climatic variability in southeastern Europe (see Haliuc et al, 2017Haliuc et al, , 2020Longman et al, 2019).…”

Challenges in Interpreting Geochemical Data: An Appraisal of Analytical Techniques Applied to a Karstic Lake Sediment Record

“…For Lake Ighiel, Ti and K were used as indicators of catchment dynamics, with their variability in the sediment column mainly controlled by runoff and changes in soil erosion. Their patterns appear to align with the forcing effects of past climate variability and, in the most recent 150 years, to reflect human-induced landscape changes enhancing soil erosion [5,41].…”

“…It has a small catchment area that comprises Jurassic limestones, but the southern inflow to the lake drains an area of Mesozoic molasse and volcanic rocks (diabase). Over time, changes in vegetation cover and the development of erosional features have occurred within the catchment; a detailed description is provided in References [5,41]. Sediment cores from Lake Ighiel were retrieved using a modified piston corer in 2013.…”

“…In recent decades, a proliferation in the availability of quantitative and qualitative geochemical analyses has resulted in a range of high-resolution research studies aiming to better understand long-and short-term lacustrine changes in relation to climate variability and human impacts. These studies focused on a variety of topics such as past climate variability [4], land-use changes [5,6], catchment dynamics, sediment delivery and lake responses [7][8][9][10][11][12], identifying rapid depositional events [13] and assessing the rate and amplitude of anthropogenic impacts [14][15][16][17].…”

“…To ensure high data reproducibility, the analysis focused on assessing the patterns in a set of lithogenic indicators, Ti, K, Ca, Fe. These elements are commonly used as paleoenvironmental proxies and have the potential to disentangle the past and recent hydroclimate variability from the land-use changes that controlled the input of sediment into Lake Ighiel [5,41]. This paper assessed the strengths and weaknesses of more recent and conventional techniques applied to a single lake sediment record and evaluated the suitability of a selected set of elements in respect to a given method and their potential use as paleoclimatic and paleoenvironmental proxies.…”