The not-so-dead of winter: underwater light climate and primary productivity under snow and ice cover in inland lakes

Although previously overlooked, winter is now seen as a period of significant biological activity in the annual cycle of north‐temperate lakes. Research suggests a future of reduced ice cover duration and altered snow conditions could significantly change the functioning of aquatic ecosystems. This study seeks to explore the possible repercussions of changing ice and snow dynamics on aquatic biological communities, particularly at lower trophic levels. To explore plankton community responses to changing under‐ice light conditions, we performed a whole‐lake manipulation by removing all of the snow from the surface of a north temperate bog lake in northern Wisconsin. Over three winters, samples were collected under ice in the study lake, South Sparkling Bog. The first winter, 2018–2019, served as a reference year during which snow was not removed from the lake and was followed by two subsequent winters of snow removal during 2019–2020 and 2020–2021. Data collected included phytoplankton and zooplankton abundances and taxa, chlorophyll a, dissolved organic carbon, light, Secchi depth, and ice and snow thickness. In our snow removal years, increased light availability in the water column shifted the phytoplankton community from low‐biomass, mixed community of potential mixotrophs, unicellular cyanobacteria and Chlorophytes to dominance by photoautotrophs, and rotifer zooplankton densities increased. Ice condition, specifically the thickness of white ice vs. black ice, was a major driver in the magnitude of change between years. This research improves our understanding of how plankton communities might respond to climate‐change driven shifts in winter dynamics for north temperate systems.

Section: Discussioncontrasting

confidence: 99%

Section: Discussionsupporting

confidence: 72%

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Under‐ice plankton community response to snow removal experiment in bog lake

Socha

Gorsky

Lottig

et al. 2023

“…Many previous studies showed that phytoplankton biomass and production diminish during winter (e.g., Hampton et al 2017; Shchapov et al 2021). However, high under ice phytoplankton biomass and production has been documented in many systems including Lakes Baikal, Michigan, and Erie and smaller lakes in Poland, Japan, and the USA (Maeda and Ichimura 1973; Vanderploeg et al 1992; Mackay et al 2006; Twiss et al 2012; Kalinowska et al 2019; Bramburger et al 2022). While all of our stations showed relatively low seston concentrations during winter, there were important differences among them.…”

Section: Discussionmentioning

confidence: 99%

Opening the black box of winter: Full‐year dynamics of crustacean zooplankton along a nearshore depth gradient in a large lake

Shchapov

Ozersky

2023

Self Cite

Past studies of zooplankton seasonality in large temperate lakes have often neglected the winter period. Winter conditions are rapidly changing (e.g., reduced ice cover extent and duration, altered thermal and mixing regimes) in northern lakes, making it important to fill the existing winter knowledge gap. In this study, we sampled five stations in Lake Superior across a nearshore depth gradient through the full year to assess the phenology of crustacean zooplankton communities and the effect of environmental drivers on them. Across stations, zooplankton densities were the lowest in winter (0.9 AE 0.6 Ind. L À1 ) and highest in summer (14.2 AE 15.1 Ind. L À1 ). Zooplankton abundances and community composition were less seasonally variable at deeper stations compared to shallower and more terrestrially affected regions. Cladocerans were the dominant taxonomic group during the summer across all stations, while cyclopoid and calanoid copepods were more important during the fall, winter, and spring. Among feeding groups, herbivores were most abundant in summer while omnivores and carnivores dominated in winter. We found that water temperature and food availability were the main drivers of total zooplankton densities through the year and during the cold seasons, but the effect of these factors varied among the main taxonomic groups. Our study demonstrates seasonal and spatial variation in crustacean zooplankton and environmental parameters, with the highest fluctuation at shallower stations. This study offers new information on seasonal crustacean zooplankton dynamics and contributes to understanding the effects of climate change on large lake ecosystems.

“…In this case, with water temperatures below the temperature of maximum density, solar radiation warming near‐surface water would increase its density causing instability and mixing as has been observed in spring (Farmer 1975; Austin 2019; Bouffard et al 2019; Austin et al 2022). Any increases in oxygen below the ice, for instance oxygen excluded on formation of the ice (Scholander et al 1953; Huang et al 2021) or produced by photosynthesis as has been observed in spring or in temperate lakes when sufficient light penetrates through the ice (Jewson et al 2009; Bramburger et al 2022), could be mixed downwards to depths where it can be detected by sensors below the ice. Thus, while respiration is expected to dominate oxygen budgets under the ice in arctic lakes, increases in oxygen induced by exclusion from the ice or by photosynthesis in the water column or in the sediments could depress depletion rates following ice‐on.…”

mentioning

confidence: 99%

Oxygen depletion and sediment respiration in ice‐covered arctic lakes

Schwefel

MacIntyre

Cortés

et al. 2023

Processes regulating the rate of oxygen depletion determine whether hypoxia occurs and the extent to which greenhouse gases accumulate in seasonally ice-covered lakes. Here, we investigate the oxygen budget of four arctic lakes using high-frequency data during two winters in three shallow lakes (9-13 m maximal depth) and four winters in 24 m deep main basin of Toolik Lake. Incubation experiments measured sediment metabolism. Volume-averaged oxygen depletion measured in situ was independent of water temperature and duration of the ice-covered period. Average rates were between 0.2 and 0.39 g O 2 m À2 d À1 in the shallow lakes and between 0.03 and 0.14 g O 2 m À2 d À1 in Toolik Lake, with higher rates in smaller lakes with their larger sediment area to volume ratio. Rates decreased to $ 20%-50% of initial values in late winter in the shallow lakes but less or not at all in Toolik. The lack of a decline in Toolik Lake points to continued oxygen transport to the sediment-water interface where oxygen consumption occurs. In all lakes, lower in situ oxygen depletion than in incubation measurements points toward increasing anoxia in the lower water column depressing loss rates. In Toolik, oxygen loss during early winter was less in years with minimal snow cover. Penetrative convection occurred, which could mix downwards oxygen produced by photosynthesis or excluded during ice formation. Estimates of these terms exceeded photosynthesis measured in sediment incubations. Modeling under ice-oxygen dynamics requires consideration of optical properties and biological and transport processes that modify oxygen concentrations and distributions.