PARTICULATE ORGANIC MATTER I N SEA WATER
109
better than any other calculations for deep sea fauna and flora, and
they vary by an order of magnitude or more. Riley (1951) noted that
the oxygen concentration decreases toward the bottom, indicative of
utilization on or near the bottom. Computations of eddy diffusivity
combined with observed oxygen gradients indicated that transfer of
oxygen toward the bottom was equivalent to a utilization of 0.4 mg
C/m2 of bottom in a day.
ZoBell and Morita (1956) arrived at a larger estimate based upon
observed quantities of bacteria in deep sea sediments. They postulated
an annual yield of 0.5 g of bacterial carbon/m2 of deep ocean sediment
(1.4 mg/day). The bacterial population probably would have to utilize
about 3 mg of organic carbon per day in order to maintain this level
of production, and in a steady state situation their production would be
utilized by benthic animals. Thus Riley et al. (1965) concluded that
this kind of estimate involves a total utilization of about 4.4 mg
C. m - .day -
This calculation is subject to the same kind of difficulties that were
apparent in the discussion of bathypelagic populations. It is based
on a realistic estimate of the biomass of bacteria in deep ocean sediments, but there is no assurance that their metabolic rate is assessed
properly. Kriss et al. (1966) have noted some alterations in metabolic
processes of bacteria that are induced by high pressure, but there is
little information on total oxygen consumption and energetic requirements of the natural population.
The wide discrepancy between these two estimates given above
might be resolved if we knew more about the biomass and food requirements of deep sea benthic fauna. Vinogradova (1962) has summarized
much of the available information on quantitative collections. She
found that the biomass is generally between 0.1 and 1 g/m2 wet weight
at depths in excess of 2 000 m, although samples of 0.05 g/m2 or even
less have been obtained, particularly in deep tropical waters. The
range is large enough so that an average may not be very meaningful,
but Vinogradova suggested that the " approximate mean biomass "
in waters of greater than 3 000 m is about 0.2 g/m2. This presumably
would correspond to a carbon content of about 20 mg, and a general
range of 10--100 mg C/m2 is indicated for most deep ocean communities.
Normally one would expect the daily food requirement to be at least
1-2% of the biomass of the fauna, so that the average consumption
might be of the order of 0.2-0.4 mg C.m-2.day-1, and the total range
might be about 0.1-2 mg/day.
These numbers are of the same order of magnitude as the estimates
derived earlier for total utilization. The minimum estimate of
109
better than any other calculations for deep sea fauna and flora, and
they vary by an order of magnitude or more. Riley (1951) noted that
the oxygen concentration decreases toward the bottom, indicative of
utilization on or near the bottom. Computations of eddy diffusivity
combined with observed oxygen gradients indicated that transfer of
oxygen toward the bottom was equivalent to a utilization of 0.4 mg
C/m2 of bottom in a day.
ZoBell and Morita (1956) arrived at a larger estimate based upon
observed quantities of bacteria in deep sea sediments. They postulated
an annual yield of 0.5 g of bacterial carbon/m2 of deep ocean sediment
(1.4 mg/day). The bacterial population probably would have to utilize
about 3 mg of organic carbon per day in order to maintain this level
of production, and in a steady state situation their production would be
utilized by benthic animals. Thus Riley et al. (1965) concluded that
this kind of estimate involves a total utilization of about 4.4 mg
C. m - .day -
This calculation is subject to the same kind of difficulties that were
apparent in the discussion of bathypelagic populations. It is based
on a realistic estimate of the biomass of bacteria in deep ocean sediments, but there is no assurance that their metabolic rate is assessed
properly. Kriss et al. (1966) have noted some alterations in metabolic
processes of bacteria that are induced by high pressure, but there is
little information on total oxygen consumption and energetic requirements of the natural population.
The wide discrepancy between these two estimates given above
might be resolved if we knew more about the biomass and food requirements of deep sea benthic fauna. Vinogradova (1962) has summarized
much of the available information on quantitative collections. She
found that the biomass is generally between 0.1 and 1 g/m2 wet weight
at depths in excess of 2 000 m, although samples of 0.05 g/m2 or even
less have been obtained, particularly in deep tropical waters. The
range is large enough so that an average may not be very meaningful,
but Vinogradova suggested that the " approximate mean biomass "
in waters of greater than 3 000 m is about 0.2 g/m2. This presumably
would correspond to a carbon content of about 20 mg, and a general
range of 10--100 mg C/m2 is indicated for most deep ocean communities.
Normally one would expect the daily food requirement to be at least
1-2% of the biomass of the fauna, so that the average consumption
might be of the order of 0.2-0.4 mg C.m-2.day-1, and the total range
might be about 0.1-2 mg/day.
These numbers are of the same order of magnitude as the estimates
derived earlier for total utilization. The minimum estimate of