Aim and main questions: We will investigate the evolutionary potential of representative Harmful Algae Bloom (HAB) species relative to that of resident key species. Phytoplankton – even from extreme environments – evolve rapidly, but it is likely that resident key species and invasive HAB species may differ in how fast they evolve, and the phenotypes that the evolved species will display. Additionally, they will not only have to evolve either in the presence of a species already being there (this is what it looks like from the point of view of the HAB forming species), or a new species arriving in their living room (this what it looks like from the perspective of the resident species), but the abiotic environmental conditions will also be changing at great speed. For example, we expect the future Arctic surface waters to be characterised by lower salinity, but higher temperatures, with strong regional differences as to how large these changes in salinity and temperature are going to be. 

Approach: We use freshly isolated algal strains from Disko Bay for laboratory experiments in Hamburg (experimental evolution) and Konstanz (competition assays). Some of these samples have already been taken by the University of Copenhagen in 2022, and more will be collected during field campaigns in the years to come. In this part of the project, we will investigate reaction norms of representative pre-isolated HAB strains prior and after experimental evolution (100 phytoplankton generations – roughly one year on human time scales) in environments characterised by warming and changes in salinity. The former will give us a baseline for the salinities and temperatures  they can survive (their thermal tolerance) and the phenotypes they display in these environments (their thermal performance). Crucially, this tells us what phytoplankton can do today, with the genetic set-up they have today, and tell us something about the stepping stones that will lead to evolution. As the environment changes on timescales that amount to evolutionary timescales for the fast-lived phytoplankton, the phenotypes they will display in the future, and the speed at which phenotypes change or become more common, will depend on both physiological limits and evolutionary potential. Experimental evolution will help us find out more about the latter.  Some of the target HAB species will be Pseudo-nitzschia seriata, Alexandrium ostenfeldii and Phaeocystis, while some of the non-harmful taxa are  vs Thalassiosira rotula , Heterocapsa, Scripsiella and Chrysochromulina leadbeateri. Our phenotypic traits of interest willinclude but are not limited to cell size, photosynthesis rates, and toxin production of all species.

Output and deliverables: The first explicit comparison of differences in the speed and magnitude of evolutionary responses, and the resulting phenotypes, for HAB and non HAB species under warming and reduced salinity.