Under‐ice mesocosms reveal the primacy of light but the importance of zooplankton in winter phytoplankton dynamics

Hrycik, Allison R.; Stockwell, Jason D.

doi:10.1002/lno.11618

Cited by 24 publications

(18 citation statements)

References 61 publications

(83 reference statements)

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“…In both lakes, the light under the ice increased rapidly when ice started to melt and especially following snowmelt (Figure 7). There was, however, no indication of a spring bloom and higher Chl‐ a concentrations, despite the known light limiting effects of ice and snow cover on phytoplankton growth (Hrycik & Stockwell, 2021). It is likely that our water samples that were taken from the integrated water column prevented us from measuring increases in Chl‐ a that may have been restricted to close to the lit surface by radiative convection that initiates in late winter (Cortés & MacIntyre, 2019), or in subsurface convective cells (Bégin, Tanabe, Rautio, et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

et al. 2021

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Over the last few decades, global warming has led to widespread shrinking of the cryosphere and has brought a sense of urgency toward the study of ice habitats. One of the most heavily impacted cryospheric habitats is freshwater ice. Climate change is leading to substantial reductions in the thickness and duration of lake and river ice cover worldwide (Sharma et al., 2019;Wrona et al., 2016). In the northern hemisphere, ice in lakes and rivers freezes an average of 5.8 days later and melts 6.5 days earlier than 100 years ago, based on the measurements taken between the years 1846and 1995(Magnuson, et al., 2000. Global air temperatures increased 1.2°C during this period. The majority of boreal and Arctic lakes are still ice-covered for six to ten months a year, and the potential importance of this cold and dark period on ecosystem structure and function is increasingly recognized (Grosbois & Rautio, 2018;Hampton et al., 2017;Schneider et al., 2017). Considering that ice-covered lakes include nearly 50% of the world's lakes, there is a pressing Abstract Around 50% of the world's lakes freeze seasonally, but the duration of ice-cover is shortening each year and this is likely to have broad limnological consequences. We sampled freshwater ice and the underlying water in 19 boreal and polar lakes to evaluate whether lake ice contains an inoculum of algae, nutrients, and carbon that may contribute to lake ecosystem productivity. Boreal and Arctic lakes differed in ice duration (6 vs. >10 months), thickness (70 vs. 190 cm), and quality (predominantly snow ice vs. black ice), but in all lakes, there were consistent differences in biological and biogeochemical composition between ice and water. Particulate fractions were often more retained while most dissolved compounds were excluded from the ice; for example, the ice had more terrestrial particulate carbon, measured as fatty acid biomarkers (averages of 1.1 vs. 0.3 µg L −1 ) but lower dissolved organic carbon (2.2 vs. 5.7 mg C L −1 ) and inorganic phosphorus concentrations (4.0 vs. 7.5 µg C L −1 ) than the underlying water. The boreal ice further had three times higher chlorophyll-a, than the water (0.9 vs. 0.3 µg L −1 ). Of the dissolved fractions, the contribution of protein-like compounds was higher in the ice, and this in all lakes. These labile compounds would become available to planktonic microbes when the ice melts. Our results show that freshwater ice has an underestimated role in storage and transformation in the biogeochemical carbon cycle of ice-covered lake ecosystems.Plain Language Summary Winter ice cover of 1-2 m thickness can comprise 20%-70% of the total lake depth in boreal and Arctic lakes. While sea ice is known to contain substantial quantities of carbon and organisms that at ice melt contribute to biological production in the underlying water column, little is known about the composition of lake ice and its role in storage of organic carbon. Our analyses of 19 boreal and Arctic lakes revealed large but different stores of organic material in lake ...

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Section: Discussionmentioning

confidence: 99%

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

et al. 2021

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“…Snow-free ice can show a high transmittance for radiation (Bolsenga & Vanderploeg, 1992;Jewson et al, 2009), and thus light-driven mixing (Kirillin et al, 2012;Yang et al, 2017) and photosynthesis (Garcia et al, 2019) occur under ice. Especially, light differences determine the composition of under-ice phytoplankton (Charvet et al, 2014;Kalinowska & Grabowska, 2016;Hrycik & Stockwell, 2021), and the stimulation of under-ice primary production by increased light availability also enhances the activity of aerobic heterotrophic bacteria (Garcia et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Temporal and spatial differences of the under-ice microbiome are linked to light transparency and chlorophyll-a

Obertegger

2022

Hydrobiologia

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Under-ice community dynamics are barely understood. Temporal and spatial studies are needed to fully understand the consequences of a declining ice cover on microbial biodiversity. Here, bacterial communities of different years (2015, 2017–2021) and layers (upper and lower euphotic layer, euphotic layer, hypolimnion) were assessed by Illumina sequencing of the 16S rRNA gene. Alpha- and beta-diversity of summer and under-ice hypolimnetic communities were similar, and a seasonal difference was found only when excluding summer hypolimnetic communities. Similarly, in non-metric multidimensional scaling (NMDS), summer and under-ice communities were different even though hypolimnetic communities were similar. Investigating under-ice conditions, the year 2017 showed highest under-ice light and chlorophyll-a while 2021 showed no under-ice light and lowest chlorophyll-a. Under-ice communities were not linked to layer differences implying that a spatial distinction under ice was less important than in summer, especially in years with little or no under-ice light. Most under-ice bacterial classes and ASVs showed direct and indirect dependencies on light availability and primary production. Similarly in NMDS with only under-ice communities, light transparency and primary production were important. In the future, ice conditions with less snow cover might lead to bacterial communities similar to that of high-light years (2017, 2018, 2020).

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“…Consequently, water column NO 3 concentrations could decrease over time in frozen eutrophic lakes if NO 3 inputs to the lake water column from external (groundwater or riverine discharges) and internal (nitrification) sources are lower than NO 3 removal via denitrification. Furthermore, if light is not too low under the snow and ice, autotrophic uptake could also promote N removal in shallow eutrophic lakes (Hrycik and Stockwell 2021). Thus, studies that analyze temporally resolved under-ice monitoring data in N-rich lakes are necessary to assess this conceptual model.…”

Section: Introductionmentioning

confidence: 99%

Ice cover and thaw events influence nitrogen partitioning and concentration in two shallow eutrophic lakes

et al. 2021

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The frequency and duration of lake ice cover is rapidly declining in the Northern Hemisphere. Limited research in oligotrophic and mesotrophic lakes suggests that extended periods of ice cover influence nitrogen (N) cycling by promoting nitrate (NO 3 -) accumulation. However, ice cover impacts on N cycling in shallow, high-nutrient, eutrophic lakes remains poorly understood. To understand drivers of under-ice water column N concentrations, we examined concurrent under-ice N concentration, hydrometerological, and physicochemical time series from two shallow eutrophic systems during sustained cold and thaw periods. We compared data from both lakes during a historically cold winter to assess how different lake-watershed physical configurations and algal biomass affected under-ice N cycling. We also used time series data from consecutive winters to assess the influence of a mild versus a historically cold winter on under-ice N cycling in one of the lakes. We found that ice cover promoted NO 3 depletion when sustained cold disconnected lakes from watershed loading, but the amount of depletion varied between lakes and was enhanced during the colder winter. Thaw events increased NO 3 concentrations compared to late winter and altered the concentration and distribution of N species in the water column, but the degree and nature of increased NO 3 varied with thaw severity, the source of meltwater, timing, and lakewatershed morphometry. Our results suggest that winters with shorter ice duration and more thaw events may result in less NO 3 depletion and higher peak NO 3 concentrations in shallow eutrophic lakes, with potential implications for N cycling and phytoplankton ecology.

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Under‐ice mesocosms reveal the primacy of light but the importance of zooplankton in winter phytoplankton dynamics

Cited by 24 publications

References 61 publications

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

Hidden Stores of Organic Matter in Northern Lake Ice: Selective Retention of Terrestrial Particles, Phytoplankton and Labile Carbon

Temporal and spatial differences of the under-ice microbiome are linked to light transparency and chlorophyll-a

Ice cover and thaw events influence nitrogen partitioning and concentration in two shallow eutrophic lakes

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