Plain Language Summary
Marine snow are microscopic particles that form in the surface of the
ocean and sink into the deep ocean. Most of these particles are the
remains of dead algae and feces of tiny animals (zooplankton). The
deeper the particles sink into the ocean before microbes or animals
consume them, the longer it takes before the carbon in those particles
can return to the atmosphere. In parts of the ocean where there is no
oxygen, more particles sink to greater depths, for reasons that are not
well-understood. We used an underwater camera to observe marine snow
particles in the ocean just west of Mexico where there is little to no
oxygen at depth. We compared the observations to predictions from
several computer simulations representing hypothesized mechanisms to
explain why particles are consumed less in water without oxygen. Our
measurements suggest that one reason that particles sink to deeper
depths here is because microbes consume the particles slowly when there
is no oxygen. Meanwhile, zooplankton still break large particles into
smaller ones and produce fecal pellets in these low oxygen waters.