Amy Maas
Assistant Scientist, Bermuda Institute of Ocean Sciences

Refining our Understanding of Zooplankton Contributions to Biogeochemistry
Many zooplankton and nekton make daily migrations below the ocean’s euphotic zone and mixed layer. In the darkness of the “twilight zone” they respire and excrete, releasing surfaced derived CO2 and waste products into the midwater. Globally, these migrations account for 15 – 40% of the total organic carbon export from the surface to ocean interior, exceeding in many cases the carbon flux associated with passively sinking particles, while similar percentages have been reported for the nitrogen-related processes. These zooplankton also contribution to midwater fragmentation and repackaging of sinking surface material; this influences the attenuation of flux (nutrient transport) from the surface to the deep ocean. Variability in the vertical distribution and physiology of zooplankton can thus substantially affect community ecology and biogeochemical cycles in the open ocean. Technological advances, including imaging technologies, high-throughput molecular sequencing and ultrahigh resolution mass spectrometry, are providing innovative opportunities to investigate the details of how zooplankton both influence and are constrained by midwater (100 – 1000 m) processes. Leveraging the multi-decadal Bermuda Atlantic Time Series (BATS) and collaborations among zooplankton ecologists, physical, microbial, and chemical oceanographers (BIOSSCOPE, EXPORTS), these new tools are enabling novel observations and analyses that have the potential to revolutionize our understanding of the roles that zooplankton play in the midwater ecosystem. Current investigations are focusing on identifying the spatial/temporal distributions of organisms in the water column, how their physiology changes over daily time scales (via transcriptomic, proteomic and organismal level metrics), determining the composition of their excreta (including the use of metabolomics), and exploring how these factors collectively influence the microbial community and the cycling of organic matter.