increases in Hdinos. Regarding the February 1999 Lauderia bloom, they state,
“surprisingly, this high biomass was not eaten at all [take that to mean “significantly
eaten”] by either mesozooplankton or by microzooplankton”. Their sediment traps
showed that virtually all of the bloom was exported to the bottom uneaten. Other
observations are available (e.g. antarctic data in Archer et al. 1996) documenting
modest effects from Hdino grazing on diatoms during the decline of blooms. The
numerous but scattered data suggest Hdino grazing is sometimes significant,
sometimes not. Access to prey nearly as large as the predator apparently does not
extend to particle-feeding ciliate protists, which are largely limited to prey less than a
tenth of their body dimensions.
Micrometazoans
(^) In addition to larger protozoans, smaller metazoans are important as predators of
protists. Small copepods (Oithona, Paracalanus, Parvocalanus, Clausocalanus,
Microcalanus, Ctenocalanus, ...) are by far the most numerous small
mesozooplankton, much more abundant than usually shown with the classic nets of
200 and 333 μm mesh (Turner 2004). The adults are ∼0.6 to 1.2 mm long, but much
narrower and readily pass through the mesh. As a group they have relatively high
fecundity, for example, up to >80 eggs −1 d−1 for Paracalanus parvus in California
coastal waters when food is abundant (Checkley 1980). Thus, very large numbers of
nauplii <200 μm are part of the microplankton community, feeding partly as mid-level
predators on Hflag and other nanoplankton. Their importance relative to that of
ciliates and dinoflagellates remains to be adequately quantified. Copepods strongly
favor ciliates as food (Calbet & Saiz 2005), possibly a main transfer link from the
microbial to the mesozooplankton trophic levels.
(^) Certainly the feeding impacts of the various components of the very small grazing
community (2 to 200 μm) will vary greatly, so that a spectrum of possible
combinations of sizes and taxonomic relationships must be considered and
characterized. It turns out that experts on different groups are often also champions
for their significance, which may or may not help with moving this task toward
completion. At least they are out to sea gathering data for their teams.
Top-Down Cascades
(^) As will be discussed in the chapter on fisheries, stocks of large, predatory fish have
been dramatically reduced worldwide by fishing. For example, long-line catch rates of
yellowfin tuna in northeastern Brazil’s EEZ declined from 9.6 fish per 100 hooks in
1956 to 0.77 in 1971, stayed low for a decade, then recovered some to ∼1.5 fish per
100 hooks from 1988 to 2003 (Vaske et al. 2003). In reviewing fisheries, we learn