226
diverse bacteria once the defenses of the phytoplankter are lost. Simon et aZ. (1990) showed that
diatom-based marine snow was largely detrital; phytoplankton plus bacteria biomass carbon
accounted for only 1-13 % of the total aggregate carbon, possibly (but not necessarily) the
detritus-dominance reflected mass-mortality of phytoplankton. Yet, the mass-mortality of
aggregated phytoplankton may in itself serve as an adaptive strategy via cryptic growth (Fig. 4).
Phytoplankton snow aggregates develop high nutrient levels, probably due to intense
remineralization of the dying cells. The regenerated nutrients could support robust growth (even
luxury uptake of nutrients) of a small fraction of the phytoplankton population in the aggregate
while the aggregate is in the euphotic zone. Some of these nutrients replete and the growing
fraction of phytoplankton might be released from the aggregate and serve to temporally stretch
out the persistence of the phytoplankton species in the environment. (Bacterial progeny may also
be released during this period; discussed later). Once below the euphotic zone, the aggregate's
metabolism will become dominantly heterotrophic; bacteria will take over and kill most (but
perhaps not all) phytoplankton. Some may survive to make resting stages as suggested by
Smetacek. Perhaps we should think in terms of multiple strategies of phytoplankton (and
bacteria) for survival and persistence in the wake of a bloom.
BACTERIA-DETRITUS INTERACTIONS
Bacteria as competitors with metazoa: biogeochemical implications
Bacterial colonization is often thought of as a way to enrich the detritus with Nand P to improve
its nutritional quality for detritivorous metazoa. This notion is simplistic when considered from
the standpoint of the biochemical adaptations of bacteria. The extensive literature (reviewed by
Hoppe, 1984; Pedr6s-Ali6 and Brock, 1983) on the adaptive value for bacteria that attach to
particles will not be recounted here. We note, however, that producing progeny on a particle so
it might all be eaten by the animals is difficult to rationalize as adaptive. A fundamental
departure from this view is the suggestion to consider bacteria not as "helpers" of metazoa but
as avid competitors with them for detritus as a common source of nutrition (Azam, 1984; Azam
and Cho, 1987; Pomeroy and Wiebe, 1988). In this section we further develop this argument
with focus on the probable biochemical adaptations of bacteria in POM utilization in an
diverse bacteria once the defenses of the phytoplankter are lost. Simon et aZ. (1990) showed that
diatom-based marine snow was largely detrital; phytoplankton plus bacteria biomass carbon
accounted for only 1-13 % of the total aggregate carbon, possibly (but not necessarily) the
detritus-dominance reflected mass-mortality of phytoplankton. Yet, the mass-mortality of
aggregated phytoplankton may in itself serve as an adaptive strategy via cryptic growth (Fig. 4).
Phytoplankton snow aggregates develop high nutrient levels, probably due to intense
remineralization of the dying cells. The regenerated nutrients could support robust growth (even
luxury uptake of nutrients) of a small fraction of the phytoplankton population in the aggregate
while the aggregate is in the euphotic zone. Some of these nutrients replete and the growing
fraction of phytoplankton might be released from the aggregate and serve to temporally stretch
out the persistence of the phytoplankton species in the environment. (Bacterial progeny may also
be released during this period; discussed later). Once below the euphotic zone, the aggregate's
metabolism will become dominantly heterotrophic; bacteria will take over and kill most (but
perhaps not all) phytoplankton. Some may survive to make resting stages as suggested by
Smetacek. Perhaps we should think in terms of multiple strategies of phytoplankton (and
bacteria) for survival and persistence in the wake of a bloom.
BACTERIA-DETRITUS INTERACTIONS
Bacteria as competitors with metazoa: biogeochemical implications
Bacterial colonization is often thought of as a way to enrich the detritus with Nand P to improve
its nutritional quality for detritivorous metazoa. This notion is simplistic when considered from
the standpoint of the biochemical adaptations of bacteria. The extensive literature (reviewed by
Hoppe, 1984; Pedr6s-Ali6 and Brock, 1983) on the adaptive value for bacteria that attach to
particles will not be recounted here. We note, however, that producing progeny on a particle so
it might all be eaten by the animals is difficult to rationalize as adaptive. A fundamental
departure from this view is the suggestion to consider bacteria not as "helpers" of metazoa but
as avid competitors with them for detritus as a common source of nutrition (Azam, 1984; Azam
and Cho, 1987; Pomeroy and Wiebe, 1988). In this section we further develop this argument
with focus on the probable biochemical adaptations of bacteria in POM utilization in an