Award: OCE-1851222

Intellectual merit.  Cyanobacteria are crucially important marine micro-organisms, as they support ocean food chains through their photosynthesis, drive the cycling of key nutrient elements like nitrogen and iron, and ultimately help to determine how much carbon can be removed from the atmosphere and stored in the ocean. In much of the ocean, however, the growth of cyanobacteria is constrained by the very low levels of the required limiting nutrient iron that are present in seawater. At the same time, cyanobacteria are also being forced to cope with stressful environmental changes as the ocean grows warmer and warmer, including episodes of extreme heat waves.  Very little is known, though, about how iron limitation may interact with ocean warming to influence the many key biological roles that cyanobacteria fill in marine ecosystems, or how this multiple stressor effect may change with progressive heating of the ocean in the decades to come. 

This project addressed this open question using laboratory cultures of important marine cyanobacteria groups grown in future ocean simulation experiments. Some of these experiments were maintained for several years to allow the cyanobacteria to adapt to the changes in iron limitation and temperature, thus offering insights into the evolutionary processes involved.  As part of this effort, molecular biology techniques were employed to evaluate how cellular-level responses like gene expression and protein abundance react to fluctuations in iron and temperature conditions. We also used computer modeling methods to help predict the net effect of these interactions for future ocean ecosystems.

Results from these experiments demonstrated that the combined effects of iron and temperature on cyanobacteria often cannot be predicted by simply adding their separate effects together, as their interactive influence can be quite different than the sum of the parts. For some cyanobacteria groups, warmer temperatures tend to counteract the negative effects of iron limitation, meaning they may gain an advantage from future ocean heating (to a point!). For other groups, the effects of seawater heating and low iron together are negative, or neutral.  This means that the interactions between these two crucial growth-controlling factors may help to determine which groups of cyanobacteria will be winners in the future ocean, and which will be climate change losers, with implications for shifts in the ocean food webs that provide humans with important harvested resources.

Broader impacts. This project offers new insights into how a key group of marine organisms may respond to a changing ocean, and fills in knowledge gaps that will lead to better projections of how the life of the ocean will react to multiple climate stressors.  Educational impacts included support for many graduate, undergraduate and K-12 researchers, thereby helping to train the next generation of ocean scientists for the future.

 

Last Modified: 12/19/2024
Modified by: David A Hutchins