Life in the shelf seas - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 168

Figure 5.18 Observations from the
coastal waters of the southern Kattegat,
Denmark, over 1 year. (a)
Phytoplankton chlorophyll biomass for
cells > 11 m m. (b) Egg production rate for
one species of copepod (Acartia). (c)
Total adult copepod abundance.
Adapted from (Kiørboe, 1993 ), with
permission from Elsevier.

>200

(a)

200

150

100

50

0

(b)

20

10

0

(c)

2

1

0

J F M A M J J A S O N D

Month

cyanobacteria has in comparison with these large cells because of the radius 2
dependence in the maximum uptake rate.
The answer to why diatoms can exist lies with the differences in the grazers
of the small and large cells. Earlier we described how the microzooplankton
that graze small phytoplankton cells have comparable growth rates to
their prey, and so are able to provide a significant top-down control on
concentrations of small phytoplankton. The production rates of the microzoo-
plankton are often lower than those of the larger phytoplankton that they
eat. For instance, there could be a significant delay between the start of
conditions more favourable to microzooplankton production (e.g. the onset