Regime shifts and the Biological Pump

Marine food web architecture influences everything from ocean productivity to biogeochemical cycling and the efficacy of the biological pump. Numerous lines of evidence suggest that shifts in climate and ocean condition play a critical role in structuring the plankton community composition that fuels marine food web architecture. However, our understanding of how plankton communities have shifted on centennial and longer time scales has been limited by paleoarchives of sufficient length and resolution. Deep-sea proteinaceous corals act as “living sediment traps,” preserving high resolution, long-term geochemical records of export production and the food web structure of the overlying euphotic zone. In these projects, we are applying CSIA to deep-sea proteinaceous corals to understand past changes in open ocean ecosystem food web structure and biogeochemical cycling. By understanding how and when plankton assemblages at the base of open ocean food webs have changed in the past, we can better understand future changes in food web architecture, biogeochemical cycling, and carbon sequestration in the modern era of rapid climate change.

Publications: (# indicates student author)

^#Glynn DS, McMahon KW, Guilderson TP, McCarthy MD (2019) Major shifts in nutrient and phytoplankton dynamics in the North Pacific Subtropical Gyre over the last 5000 years revealed by high-resolution proteinaceous deep-sea coral δ¹⁵N and δ¹³C records. Earth and Planetary Science Letters 515:145-153

Williams B, McMahon KW, ^#Barnes S, ^#Parks D, ^#Kim E, ^#Srebotnjak T, Etnoyer P (2019) Impact of skeletal heterogeneity and treatment method on interpretation of environmental variability from proteinaceous skeletons of deep-sea gorgonian octocorals. Chemical Geology 526:101-109

McMahon KW, Williams B, Guilderson TP, ^#Glynn DS, McCarthy MD (2018) Calibrating amino acid δ¹³C and δ¹⁵N offsets between polyp and protein skeleton to develop proteinaceous deep-sea corals as paleoceanographic archives. Geochimica et Cosmochimica Acta 220: 261-275

McMahon KW, Guilderson TP, Sherwood OA, Larsen T, McCarthy MD (2015) Millennial-scale plankton regime shifts in the subtropical North Pacific Ocean. Science 350:1530-1533

^#Schiff JT, Batista F, Sherwood OA, Guilderson TP, Hill TM, Ravelo AC, McMahon KW, McCarthy MD (2014) Compound specific amino acid d¹³C patterns in a deep-sea proteinaceous coral: implications for reconstructing detailed d¹³C records of exported primary production. Marine Chemistry 166:82-91