Award: OCE-1030149

Recent studies provide contrasting views of roles played by gelatinous and crustacean zooplankton in open-ocean food webs and carbon export to the deep ocean. The overall objective of this section of the proposal is to better understand how phyto and zooplankton community structure relates to the structure and bioavailability and transfer of energy within oligotrophic food webs and subsequent export to the shallow mesopelagic. We conducted field sampling and experiments during four process-oriented cruises in the Sargasso Sea in spring and summer of 2011 and 2012. Transects were conducted in all cruises along gradients in four types of eddies, cyclonic warm water with downwelling (cruise 1: X1101), anticyclonic with cold core and upwelling (cruise 2: X1108), cyclonic cold water with upwelling (cruise 3: AE1206) and anticyclonic with warm core water and downwelling (AE1219). Within each cruise the following parameters were characterized: zooplankton community structure, biomass, grazing, excretion and gut evacuation rates, including crustacean and gelatinous communities, phytoplankton and microbial abundances and metabolism (production), as well as basic biogeochemistry (particulate and dissolved nutrient concentrations) and particle export dynamics through use of surface tethered sediment traps and in situ pumps. In addition, colleagues from other institutions collaborated in the project to characterize the role of ichthyoplankton in open-ocean food webs and fish communities associated with Sargassum mats. Results from production and grazing experiments and stable isotope analyses suggest that autotrophic and zooplankton community structure (e.g., crustacean vs. gelatinous zooplankton dominated biomass) are driven by nutrient and primary production gradients (i.e., new vs. regenerated production) that are inherent across different types of mesoscale eddies, which in the case of gelatinous plankton may increase carbon export to depth relative to the baseline flux. Further examination of archived samples from sediment traps and grazing experiments are required to verify these findings. All data from processed samples have been quality checked and uploaded to the Trophic BATS section of the BCO-DMO data repository (http://www.bco-dmo.org/project/2150). Data from unprocessed and archived samples will be added to this data repository as they are completed and quality checked in the future. The scope of this collaborative research project has extended beyond the research based in the Sargasso Sea and several products have been produced relating to research into global jellyfish blooms. These products include a global database and several publications in press and in preparation. The formation of the Jellyfish Database Initiative (JEDI) has provided the wider scientific community with a valuable research tool and has provided information on the global biomass and baselines of the various gelatinous taxa worldwide. JEDI has also been designed as a future repository of datasets so that the baseline can be assessed in the future. JEDI currently holds over 500,000 metadata records on global jellyfish populations, including all those generated from the Trophic BATS project, and this NSF sponsored effort will be made open access with a launch date expected in early 2014. Several significant publications have been generated from JEDI including an analysis of global gelatinous biomass (Lucas et al. In Review) and an meta-analysis of the global trends in jellyfish for the past 200 years (Condon et al. 2013). The inclusion of BATS data in this analysis was invaluable given the lack of long-term information on jellyfish from open ocean environments. The most significant finding from this project was that rather than a sustained increase, as speculated, global jellyfish populations exhibit synchronous oscillations of approximately 22 years periodicity that are most probably driven by climate and solar flux cycles (see Condon et al....