Atmospheric stilling offsets the benefits from reduced nutrient loading in a large shallow lake

Janatian, Nasime; Olli, Kalle; Cremona, Fabien; Laas, Alo; Nõges, Peeter

doi:10.1002/lno.11342

Cited by 31 publications

(34 citation statements)

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“…The proliferation of Limnothrix spp. was related to improved light conditions caused by sharp regional atmospheric stilling and reduced sediment resuspension since 1997 (Janatian et al, 2019). Diatoms form the second abundant group in Võrtsjärv, in which most of the biomass is built up by large filamentous Aulacoseira spp.…”

Section: Site Descriptionmentioning

confidence: 99%

“…Finally, the decadal scale shifts in hydrometeorological variables, like a sudden increase in water level at 1978/1979 (Nõges et al, 2010) and wind stilling in 1996/97 split the 54-year time series into three periods, 1964-1978, 1979-1996, and 1996-2017 (Fig. 3), with differing by phytoplankton community structure (Janatian et al, 2019).…”

Section: Hierarchical Temporal Structure Of the Time Seriesmentioning

confidence: 99%

“…The residuals of the three models were considered as the detrended hydrometeorological variables. Correlating the respective detrended variables with phytoplankton emphasises the (i) long-term and interannual scale effect, (ii) seasonal scale effect, and (iii) episodic short scale effect of the hydrometeorological forcing on phytoplankton (O'Farrell et al, 2011;Ho et al, 2019;Janatian et al, 2019;Stockwell et al, 2020). Finally, as wind data were available at a daily resolution, we were able to test the daily effect of wind forcing.…”

Section: Associations Between Hydrometeorological Variables and Phytoplanktonmentioning

confidence: 99%

“…The nutrient loading and in-lake concentrations have decreased since 1980s, yet the phytoplankton-inferred water quality has not improved (Nõges et al, 2010). Phytoplankton in Võrtsjärv is strongly light limited and an increase in phytoplankton biomass has been promoted by improved underwater light climate due to reduced amount of suspended sediments followed by a significant wind stilling since 1997 (Janatian et al, 2019). For this reason, we included in the analysis PAR in the mixed layer and wind speed.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, at longer time scales, the relationships may be mediated by other factors like food-web relations and contain time lags. Ultimately, at the decadal scale, wind forcing may overhaul the phytoplankton community structure, as shown by Janatian et al (2019). Hence, the time scale of appearing an effect bears important information on the kind of the relationship.…”

Section: Introductionmentioning

confidence: 99%

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Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales

2021

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One of the challenges for predicting global change effects on aquatic ecosystems is the vague understanding of the mechanisms of multiple controlling factors affecting phytoplankton dynamics at different time scales. Here we distinguish between hydrometeorological forcing of phytoplankton dynamics at time scales from days to decades based on a 54-year monthly phytoplankton time series from a large shallow Lake Võrtsjärv (58°16′N, 26°02′E) in Estonia, combined with daily data on forcing factors—thermal-, wind-, light- and water-level regimes. By using variance partitioning with linear mixed effect modelling (LME), we found a continuum from the large dominant K-selected filamentous cyanobacteria with strongest decadal scale variation (8–30%) to r-selected phytoflagellates with large stochastic variability (80–96%). External forcing revealed strong seasonal variation (up to 80%), while specifically water level and wind speed had a robust decadal variation (8% and 20%, respectively). The effect of external variables was proportionally manifested in the time scales of phytoplankton variation. Temperature, with a clear seasonal variation, had no impact on the dominant cold tolerant filamentous cyanobacteria in Lake Võrtsjärv. We found the LME as a reliable method for resolving the temporal cross-scale problem. It yielded quantitative results that matched our intuitive understanding of the dynamics of different variables.

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Section: Site Descriptionmentioning

confidence: 99%

Section: Hierarchical Temporal Structure Of the Time Seriesmentioning

confidence: 99%

Section: Associations Between Hydrometeorological Variables and Phytoplanktonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales

2021

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Atmospheric stilling and warming air temperatures drive long‐term changes in lake stratification in a large oligotrophic lake

Stetler

Girdner

Mack

et al. 2020

Limnology & Oceanography

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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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Synergistic impacts of nutrient enrichment and climate change on long‐term water quality and ecological dynamics in contrasting shallow‐lake zones

Zhang

McGowan

et al. 2021

Limnology & Oceanography

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Anthropogenic and climatic stressors on freshwater ecosystems are of global concern. However, the interactions and effects of multiple stressors (e.g., nutrient enrichment, climate warming, altered wind and precipitation) acting over different spatial and temporal scales are often complex and remain controversial. Here, we reconstructed one‐century dynamics of eutrophication and primary producer communities in algal‐dominated and macrophyte‐dominated zones of a large shallow lake (Taihu, China), by integrating sedimentary photosynthetic pigments and geochemical records with water monitoring and historical archives. We aimed to explore the long‐term underlying mechanisms of the responses of water quality and lake biota to multiple environmental perturbations. We found that water quality degradation and algal community modification showed similar trends but distinct timings and trajectories in contrasting ecological zones. Onset and intensity of eutrophication in north Meiliang Bay (since the 1950s) exceeded far beyond that of macrophyte‐dominated Eastern Taihu (~1990s). Anthropogenic nutrients overtook past climatic control on production and composition of phototrophic assemblages. More importantly, lake phytoplankton responded markedly to climate warming, decreasing wind speed, and extreme weathers after cultural eutrophication. Synergistic interactions of nutrients and climate on lake ecosystems became increasingly significant in promoting harmful algal blooms (HABs) dominated by Microcystis, close to the hyper‐eutrophic north lake zones. The asynchronous limnological and ecological responses also indicated the modulating roles of lake ecological regime and catchment hydrogeomorphic characteristic. Collectively, our findings suggest that mitigation of eutrophication and HABs calls for a triple management strategy integrating anthropogenic nutrients, climate change, and lake‐catchment setting.

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Atmospheric stilling offsets the benefits from reduced nutrient loading in a large shallow lake

Cited by 31 publications

References 58 publications

Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales

Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales

Atmospheric stilling and warming air temperatures drive long‐term changes in lake stratification in a large oligotrophic lake

Synergistic impacts of nutrient enrichment and climate change on long‐term water quality and ecological dynamics in contrasting shallow‐lake zones

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