Internal iron loading and warm temperatures are preconditions for cyanobacterial dominance in embayments along Georgian Bay, Great Lakes

Abstract

Previous work suggests that a high rate of internal ferrous iron (Fe2+) loading from anoxic sediments into overlying waters favours cyanobacteria dominance (>50% of the phytoplankton biomass) over eukaryotic algae. This Cyanobacteria–Ferrous conceptual model was assessed along the Georgian Bay coastline of Lake Huron, Ontario, in one meso-eutrophic and three oligotrophic embayments that experience natural hypolimnetic anoxia. Cyanobacteria dominated all embayments in the relatively warmer summer of 2012 but not in the much cooler summer of 2014, although hypolimnetic anoxia and internal Fe2+ loading were observed in both summers in all embayments. A cyanobacteria bloom large enough to turn the lake visibly green was observed only in warmer 2012 in the meso-eutrophic embayment. Results show that warm summer temperatures and internal Fe2+ loading are necessary preconditions for cyanobacteria dominance, while high nutrient levels are needed to form large blooms. There were no consistent patterns between dominance and total and dissolved phosphorus (P), total nitrogen, ammonium, and nitrate. Internal P loading was not a necessary precondition for dominance. While P removal programs will decrease phytoplankton biomass in eutrophic waters, oxidized surficial sediments must be maintained throughout an aquatic system to prevent cyanobacteria dominance.

Riverine transport and nutrient inputs affect phytoplankton communities in a coastal embayment

“…but coincident surveys farther offshore and along-shore would be needed to properly document the population responses and driving factors.Interestingly, the harmful bloom-forming cyanobacteria, Microcystis and Dolichospermum, were absent in the present study even though they have been identified in other embayments along the east coast of Georgian Bay (e.g. High TP is one of the major factors contributing to the large blooms of harmful cyanobacteria observed in Sturgeon Bay(Verschoor et al, 2017), but those embayments are more enclosed and less energetic than Nottawasaga Bay. High TP is one of the major factors contributing to the large blooms of harmful cyanobacteria observed in Sturgeon Bay(Verschoor et al, 2017), but those embayments are more enclosed and less energetic than Nottawasaga Bay.…”

“…Sturgeon Bay and North Bay, Honey Harbor;Verschoor et al, 2017). Sturgeon Bay and North Bay, Honey Harbor;Verschoor et al, 2017).…”

“…Sturgeon Bay and North Bay, Honey Harbor;Verschoor et al, 2017). High TP is one of the major factors contributing to the large blooms of harmful cyanobacteria observed in Sturgeon Bay(Verschoor et al, 2017), but those embayments are more enclosed and less energetic than Nottawasaga Bay.…”

Coupling Water Column and Sediment Biogeochemical Dynamics: Modeling Internal Phosphorus Loading, Climate Change Responses, and Mitigation Measures in Lake Vansjø, Norway

“…With a strong focus on coupled biogeochemical processes across the SWI, this code can serve as a stepping stone to generate lake restoration scenarios (Lürling et al, 2016), test hypotheses on the response of algal biomass to external and internal fluxes of P and Fe (Verschoor et al, 2017), and help with "climate-proofing" remediation measures, whose effectiveness will likely be modulated by ongoing climate change . To this end, further model development and evaluation avenues should focus on capturing the temporal (e.g., Amirbahman et al, 2012;Katsev and Dittrich ;2013) and, in particular, spatial heterogeneity in sediment P distributions and recycling efficiencies (e.g., Dittrich et al, 2013;Doan et al, 2018;Gudimov et al, 2015;Matisoff et al, 2017Matisoff et al, , 2016.…”

“…While the majority of management measures and practices focus on reducing external P loads to improve water quality in lakes, alternative mitigation approaches rely on the addition of reactive materials to the water column to sequester P in the sediments (Mackay et al, 2014). Because of the strong coupling of the early diagenetic cycling of P and Fe (Molot et al, 2014;Doolittle et al, 2018;Verschoor et al, 2017), materials that have been used include salts of ferric Fe (Engstrom, 2005;Orihel et al, 2016;Wilfert et al, 2015), but also Al (Huser et al, 2016;Schutz et al, 2017) and Ca phases (Gulati et al, 2012), as well as lanthanum clays (Dithmer et al, 2015).…”