The ecology of marine snow starts in the surface ocean, where growing phytoplankton fix carbon dioxide into organic matter. A very small fraction of that carbon eventually ends up in the deep ocean and seafloor, where it is sequestered away from the atmosphere for long time periods.  Quantifying this component of the global carbon cycle is difficult because of the complex ecological interactions involved in transporting this carbon thousands of meters deep.  This challenge leads to major unknowns in how the ocean’s ecosystems and chemistry might respond as our global climate continues to change.  Our goal is to improve the quantification of the global carbon cycle by resolving microscopic (and oftentimes beautiful) interactions that control carbon export, and the organisms involved.  This research spans across ocean ecosystems, starting in the surface ocean where phytoplankton produce organic carbon, then into the mesopelagic where sinking particles are transformed, and finally into the bathypelagic and seafloor where carbon is sequestered for long time periods.

Export from the surface ocean:

We use drifting sediment traps to collect sinking particles. These samples are analyzed by DNA sequencing and microscopy. These methods enable us to identify the mechanisms that produced and transported carbon out of the surface ocean.  Underwater imaging and optical instruments allow us to expand the time and space scales over which we can observe sinking particles and help link our observations to the global scale.

Transformation of sinking particles in the mesopelagic:

Sinking particles are an important source of food for deep sea animals, protists, and bacteria. Grazing by these “twilight zone” organisms can reduce the amount of carbon that reaches the deep sea, but can also repackage carbon into fast sinking particles (e.g. fecal pellets). These organisms are often difficult to study, but serve as the gatekeepers to deep sea carbon sequestration.  We study their physiology and distribution to identify key mesopelagic organisms and their relative role in either attenuating or enhancing carbon export.  These creatures can be delicate and difficult to collect, so we use innovative technologies and approaches such as ROVs, imaging systems, and growth chambers.

Long-term sequestration of carbon in the deep ocean:

What controls whether sinking particles make it all the way to the deep sea? In the California Current, carbon export has been increasing over the last 3 decades at the Station M time-series location. This deep sea (4000 m) time series has been maintained and studied by the Benthic-Pelagic Coupling team. We are using DNA sequencing and microscopy to search for clues in sediment trap samples archived over the past 30 years to identify the ecological mechanisms driving this long term change in carbon sequestration.




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