Phytoplankton mortality in a changing thermal seascape. (10th July 2021)

• Record Type: Journal Article
• Authors: Baker, Kirralee G.; Geider, Richard J.
• Is Part Of: Global change biology. Volume 27:Number 20(2021)
• Page Start: 5253
• Page End: 5261
• Publication Date: 2021-07-10
• Subjects: cell death -- global warming -- mortality rate -- Phaeodactylum tricornutum -- thermal acclimation -- thermal response -- tipping points; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15772
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Predicting spatiotemporal distributions of phytoplankton biomass and community composition heavily relies on experimental studies that document how environmental conditions influence population growth rates. In unicellular phytoplankton, the net population growth rate is the difference between the cell division rate and the death rate. Along with predation and disease, phytoplankton mortality arises from abiotic stress. Although the effect of temperature on the net population growth rate is well understood, studies examining thermally induced death rates in phytoplankton are scarce. We investigated how cell division and death rates of the diatom Phaeodactylum tricornutum varied within its thermal tolerance limits (thermal niche), and at temperatures just above its upper thermal tolerance limit. We show that death rates were largely independent of temperature when P. tricornutum was grown within its thermal niche, but increased significantly at temperatures that approached or exceeded its upper thermal tolerance limit. Furthermore, the sensitivity of mortality increased with the duration of exposure to heat stress and was affected by the pre‐acclimation temperature. Heat waves can be expected to significantly affect phytoplankton mortality episodically. The increasing frequency of heat waves accompanying global warming can be expected to drive changes in phytoplankton community structure due to interspecific variability of thermal niches with potential implications for food web dynamics and biogeochemical cycles. Abstract : We demonstrate that within the thermal niche of Phaeodactylum tricornutum death rates are independent of temperature but increase significantly upon exposure to its upper thermal tolerance limits. We find that thermal thresholds can be influenced by pre‐acclimation temperatures and the duration of exposure; meaning heat waves can be expected to affect phytoplankton mortality episodically.