Anthropogenic climate change has altered primary productivity in Lake Superior

Abstract

Anthropogenic climate change has the potential to alter many facets of Earth's freshwater resources, especially lacustrine ecosystems. The effects of anthropogenic changes in Lake Superior, which is Earth's largest freshwater lake by area, are not well documented (spatially or temporally) and predicted future states in response to climate change vary. Here we show that Lake Superior experienced a slow, steady increase in production throughout the Holocene using (paleo)productivity proxies in lacustrine sediments to reconstruct past changes in primary production. Furthermore, data from the last century indicate a rapid increase in primary production, which we attribute to increasing surface water temperatures and longer seasonal stratification related to longer ice-free periods in Lake Superior due to anthropogenic climate warming. These observations demonstrate that anthropogenic effects have become a prominent influence on one of Earth's largest, most pristine lacustrine ecosystems.

Profound Changes in the Physical Environment of Lake Taihu From 25 Years of Long‐Term Observations: Implications for Algal Bloom Outbreaks and Aquatic Macrophyte Loss

“…Many previous studies have shown that the increases in phytoplankton primary production and algal blooms are associated with climate warming (Joehnk et al, ; Michalak et al, ; O'Beirne et al, ; Paerl & Huisman, ). Experiments, field observations and remote sensing monitoring in Lake Taihu confirmed that climate warming has promoted an advance of the date of the initial algal bloom, prolonged the growing season and the yearly duration, enlarged the area of algal blooms, and delayed the date of the last algal blooms (Deng et al, ; Duan et al, ; Ma et al, ; Zhang et al, ).…”

“…Many studies that have used either direct observations and experimental evidences or theoretical and model inferences have shown that anthropogenic global change is predicted to increasingly affect lake environments and ecosystems (Cohen et al, ; Farmer et al, ; O'Beirne et al, ; Pace et al, ; Smol et al, ). However, long‐term observations are more difficult to obtain in lake ecosystems than in terrestrial ecosystems, and presently available observation periods are very limited.…”

“…Recent studies based on long-term site-specific observations provide powerful examples and evidences of the role of long-term data in elucidating major ecosystem processes; revealing driving mechanisms; clarifying the relative contributions of physical, chemical, and biological factors in ecological processes; and predicting the future effects of global change on ecosystems (Clark et al, 2005;Farmer et al, 2015;Knapp & Smith, 2001;Posch et al, 2012;Schindler et al, 2008). environments and ecosystems (Cohen et al, 2016;Farmer et al, 2015;O'Beirne et al, 2017;Pace et al, 2016;Smol et al, 2005). However, long-term observations are more difficult to obtain in lake ecosystems than in terrestrial ecosystems, and presently available observation periods are very limited.…”

Intralake Heterogeneity of Thermal Responses to Climate Change: A Study of Large Northern Hemisphere Lakes

“…A direct impact of climate on lakes is climate-driven modulation of lake surface water temperature (LSWT), with potential consequences for a broad range of physical and ecological factors (De Stasio et al, 1996). Rising LSWTs can influence metabolic processes (Kraemer et al, 2017), enhance greenhouse gas emissions (Yvon-Durocher et al, 2014) and modify the key processes of vertical mixing and stratification leading to an increased occurrence of cyanobacterial blooms (Jöhnk et al, 2008), deepwater hypoxia (Jankowski et al, 2006;North et al, 2014) and changes in lake productivity (O'Beirne et al, 2017;O'Reilly et al, 2003). A detailed understanding of LSWT warming, and the factors that control it, is therefore essential for climate change impact studies.…”

Geographic and temporal variations in turbulent heat loss from lakes: A global analysis across 45 lakes

“…By modifying the key processes of mixing and stratification (Peeters et al 2002;Perroud and Goyette 2010;Stainsby et al 2011), climate-driven modulation of surface heat fluxes can alter key aspects of lake ecosystems, such as an increased occurrence of toxic cyanobacterial blooms (Jöhnk et al 2008), deep-water hypoxia (Jankowski et al 2006;North et al 2014), and changes in lake productivity (Verburg et al 2003;O'Beirne et al 2017). Evaporative heat fluxes also alter lake levels (Gronewold and Stow 2014), with consequences for water security and supply (Brookes et al 2014) and, in turn, water management strategies (Vörösmarty et al 2000;Immerzeel et al 2010;Vörösmarty et al 2010).…”