Bioavailable iron concentrations regulate phytoplankton growth and bloom formation in low-nutrient lakes

Markus Dengg; Claudine H Stirling; Karl Safi; Niklas J Lehto; Susanna A Wood; Kyyas Seyitmuhammedov; Malcolm R Reid; Piet Verburg

doi:10.1016/j.scitotenv.2023.166399

Bioavailable iron concentrations regulate phytoplankton growth and bloom formation in low-nutrient lakes

Sci Total Environ. 2023 Dec 1:902:166399. doi: 10.1016/j.scitotenv.2023.166399. Epub 2023 Aug 21.

Authors

Markus Dengg¹, Claudine H Stirling², Karl Safi³, Niklas J Lehto⁴, Susanna A Wood⁵, Kyyas Seyitmuhammedov⁶, Malcolm R Reid⁶, Piet Verburg³

Affiliations

¹ Department of Geology, University of Otago, PO Box 56, 9016 Dunedin, New Zealand; Centre for Trace Element Analysis, University of Otago, PO Box 56, 9016 Dunedin, New Zealand. Electronic address: markus.dengg@orc.govt.nz.
² Department of Geology, University of Otago, PO Box 56, 9016 Dunedin, New Zealand; Centre for Trace Element Analysis, University of Otago, PO Box 56, 9016 Dunedin, New Zealand. Electronic address: claudine.stirling@otago.ac.nz.
³ National Institute of Water and Atmospheric Research (NIWA), 3251 Hamilton, New Zealand.
⁴ Faculty of Agriculture and Life Sciences, Lincoln University, 7647 Lincoln, New Zealand.
⁵ Cawthron Institute, 7010 Nelson, New Zealand.
⁶ Department of Geology, University of Otago, PO Box 56, 9016 Dunedin, New Zealand; Centre for Trace Element Analysis, University of Otago, PO Box 56, 9016 Dunedin, New Zealand.

PMID: 37611704
DOI: 10.1016/j.scitotenv.2023.166399

Abstract

The growth of phytoplankton in lakes is thought to be primarily controlled by macronutrient concentrations, but the availability of trace metal micronutrients, such as iron (Fe), are increasingly recognised as important regulators of lake primary production. This study evaluates the role of Fe in regulating phytoplankton growth in lakes of different nutrient status in New Zealand. The results of this unique year-long study, combining highly sensitive trace metal concentration analysis of waters and particulates with advanced trace metal bioavailability and speciation modelling, constrains thresholds for bioavailable Fe and colloidal Fe of 0.8 nmol·L^-1 and 30 nmol·L^-1, respectively, below which phytoplankton growth-limitation occurs. These thresholds specifically control diatom bloom formation and termination in lakes, thereby exerting a strong influence on freshwater carbon sequestration, given the dominance of diatoms in lake bloom assemblages. Importantly, potentially toxic cyanobacteria thrived only after events of bottom water anoxia, when additional dissolved Fe in concentrations ≥4 nmol·L^-1 was released into the water column. These new thresholds for bioavailable and colloidal Fe offer the potential to manage micronutrient levels in lakes for the purpose of regulating algal bloom formation and carbon sequestration, while at the same time, suppressing the formation of harmful cyanobacterial blooms.

Keywords: Bioavailability; Diatom; Global change; Toxic algae; Trace metal.

MeSH terms

Cyanobacteria*
Eutrophication
Iron
Lakes / microbiology
Nutrients
Phytoplankton
Trace Elements*
Water

Substances

Iron
Trace Elements
Water