Role of Clay-Gel Hybrids in Enhancing Carbon Sequestration

Creative out-of-the box solutions that permit large scale removal of atmospheric CO2 are urgently needed to combat problems of global warming and ocean acidification. The present rate of atmospheric C growth is 4.7 Pg yr-1. In comparison, marine biological pump removes 5-12 Pg yr-1 of atmospheric carbon in the form of particulate organic matter (POM). The pump is highly inefficient, however, in burying carbon below the euphotic zone. More than 90% of the sinking POM is oxidized back to CO2 by marine biota as it falls through the upper 1000m and thus can more readily return to atmosphere. A significant improvement in the transfer efficiency of POM through the upper 1000m could therefore remove a much larger fraction of POM to the deep-ocean where it can be stored for over centuries to millennia We have previously proposed the role of clay minerals in removing carbon from the euphotic zone and sequestering it in the deep ocean, thereby reducing the atmospheric CO₂ [1]. A key mechanism by which the clay minerals may remove carbon is via their interaction with dissolved organic matter (DOM) and bacteria near the ocean surface. Studies from the past 25 years have demonstrated that the ocean contains exudates (e.g., polysaccharides, proteins, lipids) from marine organisms that form three-dimensional networks of marine gel ranging from nanometer to micrometer in scale. These three-dimensional gels are in dynamic equilibrium but collapse in the presence of clays to form a clay-gel hybrid. The clay-gel hybrid encourages bacterial attachment and rapid removal. Thus clay minerals are likely involved in DOM to POM conversion and also in reducing bacterial activity in the water column. Here we present a set of laboratory experiments that combine microscopic, geochemical, and microbiological approaches to 1) characterize the formation of clay-gel hybrids and 2) assess the effectiveness of clay-gel hybrids to minimize bacterial oxidation of organic carbon and enhance carbon burial in the ocean.

[1] Sharma M (2019) Goldschmidt Abstracts, 2019