Climate variability promotes unprecedented cyanobacterial blooms in a remote, oligotrophic Ontario lake: evidence from paleolimnology

Dickson Lake, located in Algonquin Provincial Park, Ontario, is a remote, oligotrophic lake, where cyanobacterial blooms of the genus Dolichospermum (Ralfs ex Bornet & Flahault) P. Wacklin, L. Hoffmann and J. Komárek were reported for the first time in the fall of 2014, and subsequently in the l...

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Bibliographic Details
Published in:Journal of paleolimnology 2019-06, Vol.62 (1), p.31-52
Main Authors: Favot, Elizabeth J., Rühland, Kathleen M., DeSellas, Anna M., Ingram, Ron, Paterson, Andrew M., Smol, John P.
Format: Article
Language:English
Subjects:
Air temperature
Akinetes
Algae
Algal blooms
Anoxia
Aquatic ecosystems
Chlorophyll
Chlorophyll a
Climate
Climate Change
Climate variability
Climatic conditions
Cyanobacteria
Density stratification
Diatoms
Earth and Environmental Science
Earth Sciences
Eutrophication
Freshwater & Marine Ecology
Geology
Lakes
Lead isotopes
Mineral nutrients
Nutrient loading
Oligotrophic lakes
Original Paper
Oxygen
Palaeolimnology
Paleolimnology
Paleontology
Physical Geography
Pollution load
Proliferation
Provincial parks
Sediment
Sedimentology
Sediments
Spring
Spring (season)
Stratification
Water quality
Water quality assessments
Water temperature
Wind speed
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Summary:Dickson Lake, located in Algonquin Provincial Park, Ontario, is a remote, oligotrophic lake, where cyanobacterial blooms of the genus Dolichospermum (Ralfs ex Bornet & Flahault) P. Wacklin, L. Hoffmann and J. Komárek were reported for the first time in the fall of 2014, and subsequently in the late spring of 2015. To investigate the potential environmental triggers of these bloom events, we assessed long-term trends in water quality using a multi-proxy paleolimnological approach, examining sedimentary diatoms, chironomids, cladocerans, spectrally inferred chlorophyll a, and cyanobacterial akinetes preserved in a 210 Pb-dated sediment core. Assemblage changes were modest in all biological proxies. A subtle increase in the abundance of warm-water chironomid taxa (T opt  > 15 °C) commences in the year ~ 2000, with further increases in the most recent years of the sediment record (~ 2013–2015). End-of-summer volume-weighted hypolimnetic oxygen concentrations (CI-VWHO), inferred from chironomid remains, reveal a decline in oxygen concentrations over the last two decades coincident with the highest levels of sedimentary chlorophyll a and cyanobacterial akinetes in the sediment record. These paleolimnological findings corroborate observed reports of the onset of cyanobacterial blooms in Dickson Lake in late 2014 and are consistent with increasingly favourable bloom-forming conditions over the past few decades that are related to warmer air temperatures, sharp declines in wind speed, and a lengthening of the ice-free season by 2 weeks since 1975. It is plausible that late ice-out and a quick onset to stratification in 2014 may have resulted in incomplete spring mixing, early onset of hypolimnetic anoxia, and increased internal nutrient loading, that, occurring during a period when climate conditions were particularly ideal for cyanobacterial proliferation, may have fueled the unprecedented algal blooms in this remote lake. Collectively, the factors causing algal blooms in remote lakes such as Dickson Lake are not yet fully understood, and it is worrisome that with continued warming the triggering conditions may become a more common feature of Algonquin Park and other minimally impacted Boreal Shield lakes in the coming years.
ISSN:0921-2728
1573-0417
DOI:10.1007/s10933-019-00074-4