Award: OCE-1635527

Oceanic biological-ecosystem variability is most often linked to changes in sea surface temperature (SST) but SST is a reflection of dynamic processes which influence: the stability of the water column, nutrient input, entrainment, and advection. Our central goal was to couple high resolution paleorecords derived from deep-sea proteinaceous coral together with new compound-specific amino acid isotope (CSIA-AA) measurements to create reconstructions of both biogeochemical change (e.g., source of nitrogen) and basic plankton ecosystem shifts in the Northeast Pacific, focusing on the California Current Ecosystem. Under this project we compared sediment trap and live-collected Isididae (bamboo coral) samples and convincingly showed that the skeletons of deep-sea proteinaceous corals are indeed acting like living sediment traps: accurately recording the CSIA-AA signature of sinking particulate organic matter on which the corals feed. We compared the CSIA-AA signature of the live animal (polyp) and the outermost proteinaceous skeleton of three different deep-sea coral taxons (Kulamanamana, Isididae, and Primnoa) and showed that there was no difference between the polyps and skeleton for source amino acid nitrogen isotope values and for essential and non-essential amino acid carbon isotope values. This result confirmed that we can use the CSIA-AA isotope values in the skeleton to directly track baseline nitrogen isotope values (equal to source amino acid isotope values) and the carbon isotope value of export production (equal to essential amino acid isotope values). We documented a reproducible offset between polyp and skeleton in the nitrogen isotope value of trophic amino acids. This most likely is a result of the synthesis of polyp tissue which has a fast turnover time and the creation of skeletal material which is essentially unidirectional incorporation of amino acids. Analyzing a sub-fossil proteinaceous deep-sea coral specimen which accreted its skeleton nearly 11,000 years ago, we studied the effects of diagenesis on the skeletal matrix, amino acid composition, and the skeletal isotope values. Although the outer portion of the skeleton showed evidence of chemical diagenesis which confounds direct interpretation of the isotope values, the physically protected inner skeleton exhibited minimal evidence of chemical diagenesis with amino acid isotope patterns implying interpretable values. The diagenetic horizon was easily identified using carbon to nitrogen ratios and an amino acid isotope proxy for bacterial resynthesis. Recorded in the proteinaceous skeleton of Central California corals are multi-decadal changes in baseline 15N, as recorded in phenylanaline and 'source AA' averages, that are intimately linked to well-known climate regimes and patterns in sea level pressure, surface winds, sea surface temperature, and upwelling dynamics. There is no centennial scale, secular linear trend in bulk 13C, 15N or in the CSIA-AAs of interest: source 15N AA, and essential 13C AA. Mixed digital media art exhibits were created to capture the imagination of deep-sea corals and other denizens of the mesopelagic. They can be viewed at https://www.modernobysaulvillegas.com/deep-sea-coral https://www.modernobysaulvillegas.com/deep-sea-coral-ii https://www.modernobysaulvillegas.com/wmuh-deep-sea-hub Last Modified: 11/27/2022 Submitted by: Thomas P Guilderson