(Sajjad Abdullajintakam)
Research Themes
Some of the driving motivations to my research involve the curiosity towards questions like
(i) What is the role of methane cycling in aquatic and sedimentary carbon cycling? How has it changed over the geological past? And how will it change in the future?
(ii) How do carbon and associated elements cycle through different geosystems, especially the aquatic and shallow sedimentary regimes? How do these processes link together in our climate system over short and long (geological) time scales?
(iii) How can we use sediment/rock records to evaluate these biogeochemical processes in the geological past and further the possibility of such processes in other habitable planets/moons?
(iv) How can we channel our understanding of biogeochemical complexities in the Earth system towards sustainability goals under rapid global change?
A few recent research projects involve:
(i) Methane-carbon cycling in ocean margins and inland waters (especially stratified lakes).
(ii) Carbon and associated elemental budgets in lacustrine and marine settings
(iii) Biogeochemical impacts of offshore hydrocarbon and methane seep on the shallow marine sediments-seafloor-water column-atmosphere system.
(iv) Role of methane-derived authigenic carbonates (MDAC) on the marine carbon budget at present and over the geological history
(v) Bottom-up perspective of ocean acidification - the role of benthic carbon flux to the water column and how it affects the carbonate chemistry of the water (marine and inland waters).
(v) Geological signatures of microbial life and their implication to Astrobiology
Research Projects
Authigenic Carbonate Precipitation at Cold Seeps
Methane-derived authigenic carbonates (MDAC) are unique storytellers of biogeochemical processes in the deep sea sites impacted by hydrocarbon seeps. Read more here
Carbon Cycling at Methane Seeps
Marine methane seeps are sites characterized by the transport of methane from deep sediments towards the shallow sediment-seafloor-water column-atmosphere system. These sites host unique biosphere-geosphere coupling that results in complex carbon cycling networks, which are important to the chemical and biological composition of our oceans. Read more here and here.
Hydrocarbon Seeps in the Gulf of Mexico
This project looked at the C-S coupling at hydrocarbon seeps in the Gulf of Mexico, recorded in near seafloor sediments, particularly on authigenic carbonate rocks.
Key findings involve:
1. Paired stable isotope plot of carbon and sulfur (δ13C of DIC and δ34S of sulfide) can be used to classify the C-S coupling modes resulting in authigenic carbonate precipitation.
2. Asphalt seeps in the southern GoM have been ongoing for 1000s of years (at least ~13.5 kyrs).
Read more here and here. (Link to Manuscript pdf)
Biomarkers
Molecular fossil records (biomarkers) are excellent recorders of biogeochemical processes in the water column and sediments of oceans and lakes. This study looked at GDGT compounds, lipid membranes primarily from Archaea that are preserved in sediments. To our interest, we found that novel GDGT isomers were present at sediment depths characterized by sulfate-driven anaerobic methane oxidation (AOM). The results show a substantial foundation to (i) improve existing paleo-proxy records to identify past methane flux events and (ii) to refine the existing GDGT based paleoproxies like TEX86. Read an abstract here (https://www.essoar.org/doi/abs/10.1002/essoar.10508771.1)
Ongoing and Upcoming Works
Methane and Carbon Cycling in Lake Settings
Most recent developments involve expanding from the methane-induced carbon cycling in marine settings to inland wetlands, especially lake settings. A particular interest involves ferruginous (Fe-rich) lakes that offer a unique window to Earth's past time periods, where such conditions prevailed in the ocean under the low-oxygen atmosphere. This is an exciting development with my postdoc mentor, Betsy Swanner at Iowa State, and an exciting team. Read more about my new lab group here. Stay tuned!