Dominant environmental drivers, such as naturally high pCO2/low pH conditions partially coupled to naturally low O2 or anoxic waters, must be crucial in shaping ecosystem and biogeochemical functioning in the ESP. Additionally, as the global ocean is both acidifying (due to absorption of anthropogenic CO2) and losing O2 (due to warming and increased stratification), the ESP also provides one of the most important natural laboratories for predicting future ocean function in the Anthropocene by understanding how biological systems
adapt to and function under these conditions. The first 5 years period showed us the need to more effectively integrate the physical and chemical oceanographic understanding of the drivers of ocean variability, at the (sub)mesoscale (former Line 1) and on inter-annual to longer time scales (former line 2), with investigation of the consequences and responses at biogeochemical, ecological, and even organismal levels (former line 3). While the physical drivers are relatively well understood, the frontier of investigation is to understand the consequences for chemical, biogeochemical, and biological function, including potential adaptive responses.
Theme I will be organized around three grand questions:
A: How well do biogeochemical flows, community composition, and even population structure of key species correlate with physical oceanographic drivers? It is not yet clear at what scale physical variability in the ocean, either due to mesoscale and sub-mesoscale structures (eddies, fronts, and jets) or due to inter-annual and longer-scale variability, impact carbon and energy flow and community composition, and it is completely unknown at what level physical processes structure populations, gene flow, and adaptations at
the organism level. The output goal is to determine the scales at which biogeochemical function, plankton community composition, and population structure of key zooplankton and phytoplankton are correlated with the physical structure of the ocean.
B: How does biogeochemical function differ among norm-oxic, OMZ, and AMZ marine systems?
Nearly a decade ago it was proposed that acidification expands OMZs by affecting their biogeochemical function, but this remains unproven. Meanwhile, it becomes increasingly clear that AMZs may function differently than OMZs: In OMZs, bacterial metabolism is still largely aerobic, while in AMZs, truly anaerobic metabolisms become prominent, and effects of changes in metal cycling in anoxic waters might profoundly affect microorganism biochemistry and thus C and N flows. The output goal is to compare biogeochemical function in norm-oxic, OMZ, and AMZ waters.
C: What is the resilience of key communities and organisms to a changing ocean, and can that be predicted by their origin?
Continued focus will be on testing both natural plankton communities (phyto- and zooplankton) and cultured phytoplankton from different origins, comparing their resilience to stressors with the ranges and natural variability (i.e. hours, weeks, months) of such stressors
experienced in their local habitat. We will focus on exploring how environmental hardening upon low pH/high pCO2 conditions can provide intra-generational acclimatization upon Ocean Acidification scenarios, and how it may vary depending on generation time of marine organisms (e.g. phyto vs. zooplankton). Global scale “Common-garden” experiments with cosmopolitan species (inter-hemisphere studies) will allow to understand how natural variability across the ocean can determine the resilience of marine communities upon ocean changing conditions not only at regional, but also for the world ocean scale.