Dr. Emmanuel Okuma

With a background in Geology and Marine Geosciences, my research explores the variability of past and present climate, oceanographic, and environmental conditions. My work spans diverse marine settings, from deep ocean trenches to high-latitude glacial fjords and biodiverse cold-water coral ecosystems.

My scientific career began with the study of biogeochemical cycling in the hadal zone of the Atacama Trench in the Southeast Pacific. By analyzing geochemical parameters (pore water and solid phase profiles) in subseafloor sediments, I demonstrated that microbial carbon turnover rates in this deep-sea environment are unexpectedly high—comparable to shallower, more productive settings. This discovery, driven by the efficient downslope transport of organic material via frequent mass-wasting events, highlighted deep-sea trenches as significant but previously overlooked hotspots for organic matter degradation and burial.

During my PhD, I investigated the complex polar marine environment of Baffin Bay (between Greenland and Canada), where ice-ocean-atmosphere interactions have shaped sedimentary systems since the Last Glacial Maximum. Using sedimentological and geochemical analyses, I reconstructed the timing and spatial shifts of sediment deposition in response to ice-sheet retreat. My research revealed that ice sheets at the shelf edge restricted sedimentation to the slope and deep basin until approximately 15,000 years ago. As deglaciation progressed, the main sediment depocenters shifted landward, leading to sediment starvation in deeper basins—a critical insight into glacially influenced sediment dynamics.

Currently, my research focuses on framework-forming cold-water corals (CWC), which support high-biodiversity reef ecosystems. Specifically, I am investigating the long-term development of CWC mounds along the eastern New Zealand continental margin in the Southwest Pacific—an area that has never before been studied in this context. By employing a range of sedimentological and paleoceanographic methods—including computed tomography, geochemical proxies, and U/Th and radiocarbon (¹⁴C) dating—I aim to reconstruct CWC growth phases and identify the environmental drivers that have influenced their proliferation and decline over time.

Through my research, I seek to improve our understanding of how past climate and oceanographic changes have shaped marine ecosystems, providing insights that are increasingly relevant in the context of ongoing global change.