Bamboo corals as unique high-resolution archives of ocean processes: Evidence from the California margin.

The California margin is home to one of the major upwelling systems in the world, productive marine fisheries, diverse benthic habitats and state and federal protected areas, including four national marine sanctuaries. Sanctuary staff are actively managing this important region for which they have limited long term data. As such, the need to contextualize modern productivity is of import. Here, we utilize deep sea corals to probe the recent biogeochemical past of this region. Specifically, we present a latitudinal gradient of bamboo corals (Isidella sp.) comprised of previously reported North-Central California (38˚N, 123.5˚W) corals and novel Central California (35.7˚N, 123.7˚W) and Southern California (33.1˚N, 120.9˚W) specimens that span the past century. We observe shifts in δ¹³C and δ¹⁵N isotopic signatures during the mid-20th century. We provide evidence that the shift can largely be attributed to changes in wind stress, and we explore the impact of this to indicate change in depth of the mixed layer, change in plankton community composition, and/or change in upwelling strength and timing. This work highlights the variability of the California Current System both spatially and temporally over decadal timescales, and the value of high-resolution ocean archives.