Deciphering long‐term records of natural variability and human impact as recorded in lake sediments: a palaeolimnological puzzle

Abstract

Global aquatic ecosystems are under increasing threat from anthropogenic activity, as well as being exposed to past (and projected) climate change, however, the nature of how climate and human impacts are recorded in lake sediments is often ambiguous. Natural and anthropogenic drivers can force a similar response in lake systems, yet the ability to attribute what change recorded in lake sediments is natural, from that which is anthropogenic, is increasingly important for understanding how lake systems have, and will continue to function when subjected to multiple stressors; an issue that is particularly acute when considering management options for aquatic ecosystems. The duration and timing of human impacts on lake systems varies geographically, with some regions of the world (such as Africa and South America) having a longer legacy of human impact than others (e.g., New Zealand). A wide array of techniques (biological, chemical, physical and statistical) is available to palaeolimnologists to allow the deciphering of complex sedimentary records. Lake sediments are an important archive of how drivers have changed through time, and how these impacts manifest in lake systems. With a paucity of ‘real‐time’ data pre‐dating human impact, palaeolimnological archives offer the only insight into both natural variability (i.e., that driven by climate and intrinsic lake processes) and the impact of people. While there is a need to acknowledge complexity, and temporal and spatial variability when deciphering change from sediment archives, a palaeolimnological approach is a powerful tool for better understanding and managing global aquatic resources. WIREs Water 2017, 4:e1195. doi: 10.1002/wat2.1195 This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Science of Water > Water and Environmental Change Water and Life > Methods

First human impacts and responses of aquatic systems: A review of palaeolimnological records from around the world

“…Over the course of the Holocene, SAR in temperate and high latitude regions generally show a gradual decline as soils began to stabilise over the postglacial period as a result of increasing vegetation cover (Dearing, 1991). Abrupt and large perturbations to this pattern are often attributed to anthropogenic triggers whereas gradual changes in accumulation rates are attributed to climate forcing (Mills et al, 2017). Basin morphometry and geology play key roles in determining the timing of initial recording of a perturbation linked to soil erosion.…”

“…While lake sediment records can provide local and regional evidence about environmental changes, detecting human influence throughout history can be challenging because of the subtlety, complexity and variable nature of many early human impacts on the environment (see Mills et al, 2017). The nature of disturbance, preservation of the impact signal and, not least, the provision of a reliable chronology all affect our ability to detect changes.…”

Diatom community responses to long‐term multiple stressors at Lake Gusinoye, Siberia

“…Freshwater lakes are under threat globally from interacting stressors (Mills et al, 2017), including contamination from human activity (Malaj et al, 2014), enrichment from catchment agriculture (Mekonnen & Hoekstra, 2018) and aquaculture (Legaspi et al, 2015), increased warming of surface waters from climate change (O'Reilly et al, 2015), increased deposition of reactive nitrogen (Nr) (Bergstöm & Jansson, 2006), increased hypoxia due to human activities (Jenny et al, 2016), alterations to local biodiversity from biological introductions and invasions (Gallardo et al, 2016), hydrological modifications (Kominoski et al, 2018), and falling water levels from abstraction and shifting precipitation patterns (Wurtsbaugh et al, 2017). Due to long-range transport of pollutants, even remote lakes are no longer truly pristine (Catalan et al, 2013;Wolfe et al, 2013).…”

Regional versus local drivers of water quality in the Windermere catchment, Lake District, United Kingdom: The dominant influence of wastewater pollution over the past 200 years

“…However, the magnitude and synchrony of lake responses to regional environmental forcings, such as climate, will also depend on basin and catchment characteristics, such as elevation, size, depth and geology (Leavitt et al., ). Acknowledging the importance of catchment characteristics as “filters” of multiple stressors (sensu Blenckner, ) can help detect sites more vulnerable to stressor effects than others (Leavitt et al., ; Mills et al., ).…”