Ans. The oxygen content in the abyssal water depends majorly depends upon the amounts that are dissolved into it at its polar site of origin and the absence of photosynthesis thus precludes the introduction of new oxygen in this zone. Abyssal waters retain several cubic centimetres of the dissolved oxygen per litre, as the sparse animal populations do not consume the oxygen faster than it is being introduced into the abyssal zone. Abyssal life is thus concentrated at the seafloor and the water nearest the floor may essentially be lack oxygen.