From controversy to consensus: making the case for recent climate change in the Arctic using lake sediments

Abstract

w ww ww w. .f fr ro on nt ti ie er rs si in ne ec co ol lo og gy y. .o or rg g © © The Ecological Society of America E cologists and environmental scientists are constantly faced with the challenge of working at the most appropriate temporal and spatial scales to reach defendable conclusions. Few recent questions have elicited more discussion and debate than those concerning the nature, magnitude, and effects of global climate change. Although there is no longer any serious scientific debate about the influence of greenhouse-gas emissions on climate, many questions remain concerning the relative importance of natural versus anthropogenic causes of climate change, as well as the spatial and temporal scales of climate-related effects on ecosystems. Each of these questions has a temporal component, yet long-term monitoring data, which will help us to find the answers, are often scarce or non-existent. Fortunately, a variety of natural archives preserve proxy data of past environmental and ecological changes, some examples of which are highlighted in this issue of Frontiers. Here, we focus on paleolimnology -the multidisciplinary science that uses the physical, chemical, and biological information preserved in lake and river sediments to reconstruct past environmental conditions (Cohen 2003; Smol in press). We also summarize the development of ideas (and associated challenges) following an earlier paper (Douglas et al. 1994), which proposed that a worrisome record of recent climate warming is preserved in Arctic sediments.The lack of long-term instrumental data in polar regions is especially disconcerting, because Arctic ecosystems, due in part to a variety of positive-feedback mechanisms, are warming at a faster rate than are other parts of the planet (ACIA 2004). In fact, based on the brief temporal windows of available instrumental meteorological data, average temperatures in the Arctic have risen at twice the rate of the rest of the world over the past few decades (ACIA 2004). Not surprisingly, polar regions are therefore often referred to as the "miners' canary" of the planet. Using a variety We live in a constantly changing environment, yet tracking ecological change is often very difficult. Long-term monitoring data are frequently lacking and are especially sparse from Arctic ecosystems, where logistical difficulties limit most monitoring programs. Fortunately, lake and pond sediments contain important archives of past limnological communities that can be used to reconstruct environmental change. Here, we summarize some of the paleolimnological studies that have documented recent climate warming in Arctic lakes and ponds. Several hypotheses have been evaluated to determine if warming, resulting in changes in ice cover and related variables (eg increased habitat availability), was the factor most strongly influencing recent diatom and other biotic changes. Striking and often unprecedented community changes were evident in post-1850 sediments, and could be linked to ecological shifts consistent with warming. Be...

Cultural eutrophication, anoxia, and ecosystem recovery in Meretta Lake, High Arctic Canada

“…However, several characteristics that distinguish Arctic lakes from their temperate counterparts have important implications for eutrophication-related processes, including the duration of thick ice cover and its control of light penetration and plankton dynamics, and the disproportionate importance of benthic communities in lake food webs (Sierszen et al 2003;Smol and Douglas 2007). While the benthos often dominates production in polar lakes (Vincent and Laybourn-Parry 2008), the response of these communities to eutrophication is poorly understood relative to that of the plankton (Vadeboncoeur et al 2003).…”

“…Past studies of Meretta Lake have included those on general limnology and the effects of eutrophication (Schindler et al 1974), phytoplankton ecology Kalff et al 1975), bacterial dynamics (Morgan and Kalff 1972), rates of photosynthesis and respiration , and diatom paleolimnology (Douglas and Smol 2000;Miche-lutti et al 2002). Although few studies exist from Arctic sites that chronicle long-term limnological responses to cultural eutrophication (Douglas and Smol 2000;Michelutti et al 2007), paleolimnology is ideally suited to reconstructing past changes in such lakes (Smol 2008) and, thereby, to providing insight into both past variability and future limnological trajectories in polar freshwaters.…”

Late Holocene changes in cyanobacterial community structure in maritime Antarctic lakes

“…Many of these regions have recently entered a period of rapid warming, which has already had an impact on the physical and chemical structure, biodiversity and functioning of their aquatic ecosystems (Quayle et al 2002;Smol et al 2005;Smol and Douglas 2007). Polar lakes have therefore been recognised as 'early warning systems' because they respond very quickly to climate-induced environmental changes (Hodgson and Smol 2008).…”

“…Polar lakes have therefore been recognised as 'early warning systems' because they respond very quickly to climate-induced environmental changes (Hodgson and Smol 2008). The consequences of the rising temperatures include increased lake water-column stability and chemical properties (Hodgson et al 2006;Parker et al 2008;Verleyen et al 2012), ecological reorganizations of algal and invertebrate communities, including the dominance of planktonic over benthic diatoms (Smol et al 2005), invasions by low-altitude and lowlatitude species (Rautio et al 2008), increased nutrient concentrations and primary production (Quayle et al 2002) and even complete desiccation (Smol and Douglas 2007). In contrast to these ecosystem-level changes, which were mainly studied in Arctic lakes, comparatively little is known about changes in the diversity and community structure of the dominant photoautotrophs in Antarctic water bodies, i.e.…”

Implications for the use of sedimentary invertebrate communities to infer past presence of fish

“…Therefore, changes in various external factors, such as in temperature and nutrients influencing limnological and ecological status of lakes have gained much attention among paleolimnologists (e.g. Lotter et al, 1997Lotter et al, , 1998Jeppesen et al, 2001a;Smol et al, 2005;Smol and Douglas, 2007). Reconstructions of past internal changes in lakes and their food-web structures have been performed using fossil remains of aquatic organisms in lake sediments, mostly remains of phytoplankton (diatoms and chrysophytes), zooplankton and zoobenthos (Cladocera, Chironomidae, Chaoboridae) (e.g.…”