(2000) and others, the overall production rate is roughly set by the trophic richness of
the system. Thus, TdR-uptake increases steadily from the most oligotrophic, oceanic
waters in subtropical gyres to the most eutrophic estuarine waters. There is no
necessary relationship between the number of bacteria and this measure of new-cell
production rate. In a suitably arranged system, stocks could be the same everywhere,
with huge variation in turnover rates. That does not occur; much of the variation in
production is reflected in variation of bacterial stocks (Fig. 5.8). Clearly, richer
habitats support larger standing stocks. Elaborate arguments (e.g. Thingstad 2000)
have been developed from the fact that biomass covers two to three orders of
magnitude, while production covers five. The relationship actually curves upward to
the right: the ratio of biomass to production is higher in the more eutrophic habitats,
suggesting a weaker coupling of production and grazing there as compared to more
oligotrophic habitats.
Fig. 5.8 Comparisons of bacterial biomass and bacterial production rates. (a) Open-
ocean sites and Chesapeake Bay sites – most of the latter with production rates greater
than 1 μg C liter−1 h−1. (b) Just open-ocean sites (also shown in A). Lines are least-
squares fits.
(^) (After Ducklow 1992.)
In addition to study of cell-number increase by TdR, other labeled substrates are