Investigating Past Ocean Ecosystem Variability with δ13C and δ15N Records in Long Lived Deep Sea Proteinaceous Corals from the Central Equatorial Pacific

Abstract:

The Central Tropical Pacific Ocean may experience large, abrupt climate variations on a century to millennial time scale that greatly impact ocean ecosystem structure and function, including primary productivity, plankton community composition, and biogeochemical cycling. Stable carbon and nitrogen isotope analyses of exported production are valuable proxies for past ocean plankton community composition, trophic structure, and nutrient utilization. However, very few long-term, high-resolution records exist from the tropics, which can establish how millennial climate variability is inherently linked to tropical ecosystem dynamics. Sediment cores are valuable archives of past ocean ecosystem dynamics, but have limited temporal resolution. In contrast, deep-sea proteinaceous corals act as living sediment traps due to direct incorporation of sinking organic matter into their organic skeletons. Since colonies can live for thousands of years, proteinaceous coral archives can significantly extend the length and resolution of δ¹³C and δ¹⁵N records in the open ocean. Here we present three δ¹³C and δ¹⁵N records obtained from the coral species Kulamanamana haumeaae that provide multi-decadal scale resolution δ¹³C and δ¹⁵N records, for the first time extending up to ~2600 years into the past. We observed large-scale oscillations in δ¹³C and δ¹⁵N values on century to millennial time scales that correspond to known major climate events, including the Medieval Climate Anomaly, the Little Ice Age, and the onset of the Industrial Revolution. These records will provide new insights into the variations in plankton community structure and nutrient dynamics in the equatorial pacific linked to long-term climate oscillations.