School of Engineering and Science - Jacobs University

CHAPTER III
C
t24
C
t0
e
( k g ) t
(1)
Whereby C t0 is the concentration of phytoplankton biomass at the beginning of the
experiment, C t24 after 24 hours, k is the phytoplankton growth coefficient, g the
microzooplankton grazing coefficient and Δt the incubation time in days.
Where in our experiments non-linearity induced by saturated feeding of
microzooplankton (Gallegos, 1989) was seen, especially in Experiment 1 and 4 where
predator abundance was low, only the three most diluted samples (10, 25, 50%) were
used for regression analysis (Paterson et al., 2008). The obtained value of apparent
phytoplankton growth was used to calculate the grazing coefficient at 100% undiluted
seawater level. For comparisons between microzooplankton and mesozooplankton
grazing we normalized grazing parameters according to predator carbon concentration:
Daily carbon specific grazing rates g c , filtration rates F c and ingestion rates I c of the
microzooplankton community were calculated for average (during the time interval t 0 -
t 24 ) prey carbon concentrations [C prey ] after Frost (1972) with g and k obtained from the
dilution experiments.
F c and I c was adjusted for the growth of predators using mean predator carbon
concentration [C predator ] according to Heinbokel (1978a) with equations (2) – (5):
F
c
g [ C
]
1
predator
(2)
I
c
F
c
[ C
prey
]
(3)
[ C
prey
]
C
t
0
( e
( k g
) t
( k g)
t
1)
(4)
[ C
predator
]
C
ln C
predator , t
predator , t
24
24
C
ln C
predator , t
0
predator , t
0
(5)
The instantaneous (natural) growth rate of phytoplankton µ 0 was calculated by adding
grazing mortality to values of apparent phytoplankton growth obtained from the
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