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Climate-driven glacial melt is altering polar ecosystems. Shifts in hydrological regimes have cascading effects on limno-terrestrial ecosystems. In the McMurdo Dry Valleys (Southern Victoria Land, Antarctica), year-round ice cover isolates lentic habitats, yet seasonal melt along the lake perimeter forms open-water “moats” during the short austral summer provide transient hydrological connectivity among soils, benthos, and the stratified water columns of the dry valley lakes. To investigate how connectivity influences biological communities, we tracked biodiversity, phytoplankton photosynthesis, and physicochemistry along lateral transects in two McMurdo Dry Valley lakes, Fryxell and Bonney. These lakes, shaped by distinct basin features (bathymetry, streams) and ecological legacies (nutrient status, chemistry), exhibited contrasting degrees of limno-terrestrial connectivity. Our data reveal that lake-specific hydrological linkages restructure microbial and invertebrate communities. We conclude that climate-induced hydrological changes destabilize previously stratified systems, altering ecological interactions and fundamental ecosystem processes across Antarctic limno-terrestrial ecosystems. Our findings provide critical insight into how polar freshwater ecosystems may reorganize under future climate scenarios, informing predictions of microbial community resilience in extreme environments.
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Dissolved organic carbon as a driver of seasonal and multiyear phytoplankton assembly oscillations in a subtropical monomictic lake
Phytoplankton assembly dynamics in lakes are highly sensitive to variability in climate drivers and resulting physicochemical changes in lake water columns. As climate change increases the frequency of major precipitation events and droughts, many lakes experience increased inputs of colored dissolved organic carbon (CDOC) and nutrients. How these CDOC-related changes in resources, transparency, and thermal stability affect phytoplankton assemblages, succession, and resilience is understudied, particularly in subtropical lakes. Here, we used time series, multivariate, and trait-based functional redundancy analyses to elucidate the roles of phytoplankton in ecosystem resilience and determine potential drivers of assemblage shifts in a subtropical monomictic lake with fluctuating CDOC inputs (Lake Annie, Highlands County, Florida, USA). We found that phytoplankton assemblages and successional patterns differed between two dark-water states (late 2005–mid-2007, late 2012–2019) bracketing a clear-water state (mid-2007–late 2012), caused by shifting CDOC and nutrient concentrations associated with oscillating groundwater levels. Diatoms (Bacillariophyta), which were dominant during the two dark-water states, nearly disappeared and were replaced by synurophytes during the clear-water state. Assemblages had greater interannual consistency in the dark-water states, while mean functional redundancy decreased in the clear-water state. Seasonal phytoplankton successional changes were also more pronounced and synchronized with seasonal hydrologic shifts in the dark-water states. Multiyear assemblage shifts occurred more quickly in clear-to-dark than dark-to-clear state transitions, suggesting phytoplankton in dark-water states may be more resistant to state transitions or even contribute to dark-water state resilience via feedback loops.
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- PAR ID:
- 10312407
- Date Published:
- Journal Name:
- Limnology and Oceanography
- ISSN:
- 0024-3590
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/lno.12004
