Abstract:

Dissolved oxygen is essential for aerobic respiration and the cycling of Fe, an important micronutrient for primary productivity, in the ocean. However, once oxygen becomes hypoxic or anoxic, Fe can be released from the sediments and accumulate in the bottom water and then transported through the ocean for phytoplankton growth. Dissolved oxygen has been declining along the coast and open ocean for decades, including within the Santa Barbara Channel (SBC), a low-oxygen channel in the Southern California borderland. To determine the impact dissolved oxygen has on benthic Fe flux in the SBC and on phytoplankton productivity along the West Coast, there first needs to be a quantitative analysis on the spatial distribution and temporal variability of oxygen in the SBC, along with simulating the impact of benthic Fe flux from low oxygen sediments have on phytoplankton productivity and ocean biogeochemistry.

In this talk I will first introduce field observation on R/V Atlantis in the SBC in which we measured the highest benthic Fe flux (0.23 and 4.9 mmol m−2 d−1) ever recorded in the region and from other oxygen minimum zones, along with dissolved oxygen measurements from Autonomous Underwater Vehicle (AUV) Sentry and the Remotely Operated Vehicle (ROV) Jason. Next, I will discuss and introduce 3-D mapping of the spatial distribution of oxygen in the SBC, and the full water column temporal variability of oxygen from 1985-2023 by using a new compiled data-set from Cooperative Oceanic Fisheries Investigation (CalCOFI), AUV Sentry and ROV Jason. Finally, I will discuss applying the benthic Fe flux measurements from the SBC to develop an updated benthic Fe parametrization, to simulate phytoplankton productivity and ocean biogeochemistry using Regional Ocean Modeling System coupled to the Biogeochemical Elemental Cycling (ROMS-BEC) model.