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Climate Change and the World's Sacred SeaLake Baikal, SiberiaAuthor(s): Marianne V. Moore, Stephanie E. Hampton, Lyubov R. Izmest'Eva, Eugene A. Silow,Ekaterina V. Peshkova, and Boris K. PavlovSource: BioScience, 59(5):405-417. 2009.Published By: American Institute of Biological SciencesDOI: http://dx.doi.org/10.1525/bio.2009.59.5.8URL: http://www.bioone.org/doi/full/10.1525/bio.2009.59.5.8
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Lake Baikal in southeastern Siberia, the Sacred Sea, incitesstrong emotions and action in Russia. In March 2006,5000 people in Irkutsk, Russia, protested the proposed con-struction of an oil pipeline scheduled to pass within 800 me-ters (m) of Lake Baikals shoreline, and, within days, President Putin announced the pipeline would be reroutedoutside the lakes watershed (Cullison 2007). In July 2007, en-vironmental activists protested against the expansion of anuranium enrichment plant in Angarsk, Russia, located withinthe airshed of Lake Baikal; one protester was killed and several were seriously injured by young men allegedly hiredby regional authorities who favor expansion of the plant(Cullison 2007).
Russians are strongly attached emotionally to Lake Baikal,in part because it represents the natural unspoiled beauty ofthe Russian motherland. Indeed, this natural phenomenon wasthe birthplace of the Russian environmental movement in themid-1960s (Weiner 1999), a movement that endures today.
Lake Baikal is a treasure trove for biologists. In part becauseof its great antiquity (it is approximately 25 million years old)and its deep, oxygenated water, this lake harbors more speciesthan any other lake in the world, and many of them are en-demic (Martin 1994). More than half of the approximately2500 animal species (Timoshkin 1995) and 30% of the 1000
plant species are endemic (Bondarenko et al. 2006a); 40% ofthe lakes species are still undescribed (Timoshkin 1995).The presence of oxygen down to its deepest depths (1642 m),a trait shared with the ocean but unique among deep lakes (>800 m), explains the presence of multicellular life and the evo-lution of an extensive, mostly endemic fauna in the lakes pro-fundal depths. For example, hydrothermal vent communitiesdependent on access to oxygen for chemoauto trophy occuron the lake floor (Crane et al. 1991). In recognition of its bio-diversity and endemism, UNESCO (United Nations Educa-tional, Scientific and Cultural Organization) declared LakeBaikal a World Heritage site in 1996. The lakes biotic richnessis matched by physical distinctions: it is the largest lake in theworld by depth and volume. Reaching oceanic depths, LakeBaikal holds 20% of Earths liquid freshwater (equivalent toall of the North American Great Lakes combined).
Unfortunately, multiple and diverse anthropogenic stres-sors threaten this extraordinary lake, as the recent protests inSiberia illustrate. Among these stressors, climate change is arguably the most insidious because of its seemingly inexorablemomentum and the many ways in which it can create syn-ergisms with other anthropogenic stressors currently con-fronting the lake. In this article, we (a) describe contemporaryclimate change in the Lake Baikal region and future climate
Climate Change and the WorldsSacred SeaLake Baikal, Siberia
MARIANNE V. MOORE, STEPHANIE E. HAMPTON, LYUBOV R. IZMESTEVA, EUGENE A. SILOW, EKATERINA V. PESHKOVA, AND BORIS K. PAVLOV
Lake Baikalthe worlds largest, oldest, and most biotically diverse lakeis responding strongly to climate change, according to recent analyses ofwater temperature and ice cover. By the end of this century, the climate of the Baikal region will be warmer and wetter, particularly in winter. Asthe climate changes, ice cover and transparency, water temperature, wind dynamics and mixing, and nutrient levels are the key abiotic variablesthat will shift, thus eliciting many biotic responses. Among the abiotic variables, changes in ice cover will quite likely alter food-web structure andfunction most because of the diverse ways in which ice affects the lakes dominant primary producers (endemic diatoms), the top predator (theworlds only freshwater seal), and other abiotic variables. Melting permafrost will probably exacerbate the effects of additional anthropogenicstressors (industrial pollution and cultural eutrophication) and could greatly affect ecosystem functioning.
Keywords: Lake Baikal, climate change, ice dynamics, anthropogenic stressors, synergistic effects
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BioScience 59: 405417. ISSN 0006-3568, electronic ISSN 1525-3244. 2009 by American Institute of Biological Sciences. All rights reserved. Request
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projections for this part of the world; (b) illustrate the potentialecological effects of climate change, while highlighting howthese effects differ from those in other lakes (e.g., Smol andDouglas 2007); and (c) discuss synergistic effects between cli-mate change and other anthropogenic stressors that are par-ticularly important for the Sacred Sea. This article builds onrecent climate-change projections for the Baikal diatom com-munity (Mackay et al. 2006) by discussing the potential re-sponses of all pelagic trophic levels, physical mixing processes,and synergisms with other anthropogenic stressors.
Evidence of climate changeLocated in southeastern Siberia (figure 1), Lake Baikal is ad-jacent to the Central Siberian Plateau, one of three areas inthe world experiencing the most rapid climate change; theother two regions are the Antarctic Peninsula and north-western North America (Clarke et al. 2007). All three areas aredistinguished by long, cold winters. For example, winter airtemperatures at Lake Baikal reach 37 degrees Celsius (C) to40C, and the lake freezes for four to five months each year;
summer air temperatures soar briefly to 25C to 30C in thisstrongly continental climate (Kozhova and Izmesteva 1998).Spatial variation in precipitation is high across the watershed,with the western coast receiving about 400 millimeters (mm)of precipitation annually, while as much as 600 to 800 mm aredeposited on the southeastern coast (Shimaraev et al. 1994).
Evidence of rapid climate change in the Baikal region is nowabundant (figure 2). Annual air temperatures increased 1.2Cover the last centurytwice the global averagewith winter temperatures increasing more (2C) than those insummer (0.8C) (Shimaraev et al. 2002). Furthermore, sur-face waters of Lake Baikal warmed rapidly and significantlyto a depth of 25 m during the last 60 years (Hampton et al.2008). In addition, the ice-free season lengthened 18 days from1869 to 2000, and ice thickness decreased 12 centimeters(cm) between 1949 and 2000 in the southern basin (Shi-maraev et al. 2002). As air temperatures warmed, annualprecipitation and snow depth increased 0.59 mm per year (83to 130 mm) and 0.135 cm per year (24 to 30 cm), respectively,over northern Eurasia between 1936 and 1995 (Kitaev et al.
406 BioScience May 2009 / Vol. 59 No. 5 www.biosciencemag.org
Figure 1. Lake Baikal, the largest (by depth and volume), oldest, and most biotically rich lake on Earth, is located at asubarctic latitude (52N to 56N latitude) within southeastern Siberia. The lakes watershed, situated within Russia andMongolia, lies mostly to the east and south of the lake while the airshed extends west of the lake to include an industrialcorridor (delineated by a black oval) along the Angara River, the sole river draining the lake. The Trans-Siberian railroadbisects this corridor, continuing around the southern end of the lake, and a large pulp mill built in the late 1960s is locatedin the town of Baikalsk. The Selenga River, draining much of Mongolia, is the lakes major tributary, delivering more than50% of the lakes surface inflow.
2002). Concomitantly, river inflow into Lake Baikal increasedsignificantly, by 300 m3 per second (0.4% of total river inputs),during the last century (Shimaraev et al. 2002).
Projected climate change Climatic changes of the past century are likely to intensify inthe Baikal region, becoming warmer and wetter by the latterpart of the 21st century, particularly during winter months(December, January, and February) (table 1; Christensen etal. 2007). According to climate projections for the Baikal region (Northern Asia, 5070N, 40180E) in Christensenand colleagues (2007), by the years 20802099, annual air temperatures will have increased by a median of 4.3C rel ativeto average temperatures of 19801999, with greater warmingexpected in winter (6.0C = median projected increase for winter months) than in summer (3.0C = median projectedincrease for June, July, and August). Air temperature increasesof a similar magnitude are projected for Alaska, the Arctic,Greenland, and Iceland (Christensen et al. 2007).
Median winter precipitation is expected to increase by26% (12% to 55% = minimum to maximum) by the end ofthe 21st century (table 1; Christensen et al. 2007). Only oneother region of the worldthe Arcticis predicted to exceedthe increase in frequency of wet winters projected for theBaikal region. The projected increase in summer precipitation(i.e., median = 9%) is one-third of that projected for winter(table 1). Importantly, more precipitation may fall as rain thanas snow, influencing ice transparency, during the springmonths (March, April, and May) of some years when airtemperatures, currently averaging 5.0C (Shimaraev et al.1994), rise above freezing.
Projections of changes in wind dynamics (speed, direction,frequency) do not yet exist, but as local differences in at-mospheric pressure between land and water grow, it is likelythat warming will generate greater wind activity (Shimaraevet al. 1994). Enhanced wind activity is particularly importantfor large lakes that already experience augmented wind fetch(i.e., wind speed increases by a factor of two or more formoderate winds over large bodies of water), as compared withland or small lakes with shoreline sheltering.
Response to climate changeA variety of abiotic drivers strongly influence ecosystemprocesses in Lake Baikal, and the magnitude of their re-sponses to climate change will largely determine how this lakefunctions in the late 21st century. Key drivers include ice du-ration and transparency, water temperature, wind and mix-ing dynamics, and nutrient loading (figure 3).
Ice duration and transparency. Unlike the case with many lakesin the world, ice is arguably the single most important abi-otic driver in Lake Baikal, because the lakes dominant primaryproducers and its top predator require ice for populationgrowth (box 1). In temperate-zone lakes, the spring phyto-plankton bloom begins shortly after ice off (when the last icebreakup before summers open waters is observed); but in LakeBaikal, the spring bloom occurs under the ice, and ice is essential for initiating and sustaining this bloom (figure 4).Large endemic diatoms (e.g., Aulacoseira baicalensis) fre-quently dominate the bloom, living and reproducing within
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Figure 2. Long-term trends in winter ice duration (data
from Benson and Magnuson 2000); air temperature (data
from NOAA 1994); water surface temperature, density of
cladocerans (individuals per liter), and summer mean
chlorophyll a (chl a; Izmesteva 2006) at or near Lake
Baikal, Siberia. The trend in winter ice duration is highly
significant for the period 18692000 (Shimaraev et al.
2002, Todd and Mackay 2003), but only data for 1945
1996 are shown here. Three annual average water tem-
perature values were missing two or more winter months
of data, and these points are noted as hollow circles. Air
temperature data are from the city of Irkutsk, ending in
1994. Summer values are averages for July, August, and
September, the months in which stratifi cation can occur.
the interstitial spaces of the ice (Obolkina et al. 2000) andforming filaments more than 10 cm in length that hang fromthe ice into the water below. When currents dislodge the diatom filaments in the littoral zone, the filaments aggregateand form large flakes that sink and cover the substrate. Herethe mucopolysaccharide coating of the flakes and filaments
presumably provides an important food source for benthicanimals, including gammarids and mollusks (Bondarenko etal. 2006b).
Climate change could threaten the under-ice algal bloomin Lake Baikal primarily through two mechanisms: shorten-ing the period of ice cover and changing the ice transparency. Ice establishes the requisite abiotic conditions (convectivemixing, dim light; figure 4) for growth of Baikals endemic diatoms, and shortening the seasonal duration of ice could curtail or prevent the under-ice phytoplankton bloom. Theduration of ice cover is predicted to shorten dramatically bythe end of the 21st century, from at least two to four weeks(Todd and Mackay 2003), to possibly two months (Shimaraevet al. 2002). Recent experimental work in the Baltic Sea (Som-mer and Lengfellner 2008) and empirical results from LakeBaikal (Izmesteva et al. 2006) suggest the lakes endemic diatoms may continue blooming in April, as they currentlydo, rather than advancing their time of bloom formation toprecede earlier ice-out dates of mid-April or earlier by the endof this century. Thus, the endemic diatoms could bloomwhen ice is absent and conditions for growth are unfavorable,because ice recession exposes them to stressfully high levelsof irradiance at the water surface (Mackay et al. 2006) and promotes warming and stratification of surface waters, whichadversely affect large heavy diatoms. Also, thinner ice hasbeen observed already at Lake Baikal (Shimaraev et al. 2002),and this may reduce the under-ice convective mixing that suspends these large diatoms in the photic zone (figure 4;Granin et al. 2000). Therefore, reductions in both i...