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1. Long-Term and Ontogenetic Patterns of Heavy Metal Contamination in Lake Baikal Seals ( Pusa sibirica )

   https://doi.org/10.1021/acs.est.7b00995  

   Ozersky, Ted ; Pastukhov, Mikhail V. ; Poste, Amanda E. ; Deng, Xiu Y. ; Moore, Marianne V. ( September 2017 , Environmental Science & Technology)
2. Atmospheric stilling and warming air temperatures drive long‐term changes in lake stratification in a large oligotrophic lake

   https://doi.org/10.1002/lno.11654  

   Stetler, Jonathan T. ; Girdner, Scott ; Mack, Jeremy ; Winslow, Luke A. ; Leach, Taylor H. ; Rose, Kevin C. ( November 2020 , Limnology and Oceanography)

   Lake surface temperatures are warming in many regions and have the potential to alter seasonal thermal stratification. However, the effects of climate change on thermal stratification can be difficult to characterize because trends in thermal stratification can be regulated by changes in multiple climate variables and other characteristics, such as water clarity. Here, we use long‐term (1993–2017) data from near‐pristine Crater Lake (Oregon) to understand long‐term changes in the depth and strength of summer stratification, measured by the center of buoyancy and Schmidt Stability, respectively. The depth of stratification has shoaled significantly (2.4 m decade⁻¹), while stratification strength exhibited no long‐term trend. Empirical observations and modeling scenarios demonstrate that atmospheric stilling at Crater Lake is associated with the 25‐year shoaling trend as spring wind speeds declined over the observation period. While summer lake surface water and air temperatures warmed during the study period, spring air temperatures were variable and correlated with summer Schmidt Stability. Our results indicate that warmer spring air temperature resulted in earlier onset of stratification and stronger summer stratification. The observed shoaling of stratification depth at Crater Lake may have important ecological consequences, especially for non‐motile primary producers who can become constrained within a thinner epilimnion and exposed to higher solar radiation and reduced upwelling of nutrients. Driven by climate changes, many large lakes may be experiencing similar trends in seasonal stratification.

    

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3. Year‐Round and Long‐Term Phytoplankton Dynamics in Lake Bonney, a Permanently Ice‐Covered Antarctic Lake

   https://doi.org/10.1029/2020JG005925  

   Patriarche, J. D. ; Priscu, J. C. ; Takacs‐Vesbach, C. ; Winslow, L. ; Myers, K. F. ; Buelow, H. ; Morgan‐Kiss, R. M. ; Doran, P. T. ( April 2021 , Journal of Geophysical Research: Biogeosciences)

   Lake Bonney (McMurdo Dry Valleys, east Antarctica) represents a year‐round refugium for life adapted to permanent extreme conditions. Despite intensive research since the 1960s, due to the logistical constraints posed by 4‐months of 24‐h darkness, knowledge of how the resident photosynthetic microorganisms respond to the polar winter is limited. In addition, the lake level has risen by more than 3 m since 2004: impacts of rapid lake level rise on phytoplankton community structure is also poorly understood. From 2004 to 2015 an in situ submersible spectrofluorometer (bbe FluoroProbe) was deployed in Lake Bonney during the austral summer to quantify the vertical structure of four functional algal groups (green algae, mixed algae, and cryptophytes, cyanobacteria). During the 2013–2014 field season the Fluoroprobe was mounted on autonomous cable‐crawling profilers deployed in both the east and west lobes of Lake Bonney, obtaining the first daily phytoplankton profiles through the polar night. Our findings showed that phytoplankton communities were differentially impacted by physical and chemical factors over long‐term versus seasonal time scales. Following a summer of rapid lake level rise (2010–2011), an increase in depth integrated chlorophyll a (chl‐a) occurred in Lake Bonney caused by stimulation of photoautotrophic green algae. Conversely, peaks in chl‐a during the polar night were associated with an increase in mixotrophic haptophytes and cryptophytes. Collectively our data reveal that phytoplankton groups possessing variable trophic abilities are differentially competitive during seasonal and long‐term time scales owing to periods of higher nutrients (photoautotrophs) versus light/energy limitation (mixotrophs).

    

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4. Long-term studies and reproducibility: Lessons from whole-lake experiments: Reproducibility of whole-lake manipulations

   https://doi.org/10.1002/lno.11012  

   Pace, M. L. ; Carpenter, S. R. ; Wilkinson, G. M. ( August 2018 , Limnology and Oceanography)
5. Short-Term Variability in Alaska Ice-Marginal Lake Area: Implications for Long-Term Studies

   https://doi.org/10.3390/rs13193955  

   Hengst, Anton M. ; Armstrong, William ; Rick, Brianna ; McGrath, Daniel ( October 2021 , Remote Sensing)

   Lakes in direct contact with glaciers (ice-marginal lakes) are found across alpine and polar landscapes. Many studies characterize ice-marginal lake behavior over multi-decadal timescales using either episodic ~annual images or multi-year mosaics. However, ice-marginal lakes are dynamic features that experience short-term (i.e., day to year) variations in area and volume superimposed on longer-term trends. Through aliasing, this short-term variability could result in erroneous long-term estimates of lake change. We develop and implement an automated workflow in Google Earth Engine to quantify monthly behavior of ice-marginal lakes between 2013 and 2019 across south-central Alaska using Landsat 8 imagery. We employ a supervised Mahalanobis minimum-distance land cover classifier incorporating three datasets found to maximize classifier performance: shortwave infrared imagery, the normalized difference vegetation index (NDVI), and spatially filtered panchromatic reflectance. We observe physically-meaningful ice-marginal lake area variance on sub-annual timescales, with the median area fluctuation of an ice-marginal lake found to be 10.8% of its average area. The median signal (slow lake growth) to noise (physically-meaningful short-term area variability) ratio is 1.5:1, indicating that short-term variability is responsible for ~33% of observed area change in the median ice-marginal lake. The magnitude of short-term area variability is similar for ice-marginal and nonglacial lakes, suggesting that the cause of observed variations is not of glacial origin. These data provide a new context for interpreting behaviors observed in multi-decadal studies and encourage attention to sub-annual behavior of ice-marginal lakes even in long-term studies. 

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