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International Journal of Marine Science 2013, Vol.3, No.15, 121-127
http://ijms.sophiapublisher.com
124
Table 1 The microzooplankton grazin of phytoplankton (g), the
concentration of chlorophyll-
a
(Chl
a
), specific diatom biomass
(B
diat.
) and dinophyta (B
dinof.
) algae in the studied coastal waters
of the Black Sea near Sevastopol
and Katsiveli
g/day
Chl
a
mg/m
3
B
diat.
%
B
dinof.
%
n
Cold
0.54 ±
0.36
0.57 ±
0.22
68 ±
29
30 ±
25
14
2006~
2007
Warm 1.19 ±
0.61
1.30 ±
0.79
50 ±
24
45 ±
24
20
Cold
0.46 ±
0.22
0.79 ±
0.60
45 ±
32
50 ±
29
21
2010
Warm 0.52 ±
0.45
0.46 ±
0.40
25 ±
21
67 ±
19
26
Figure 4 Dependence of the microzooplankton grazing from
chlorophyll-
a
concentration in the coastal waters of the Black
Sea near Sevastopol and Katsiveli in the warm period in 2010
Obviously, microzooplankton grazing rate increases
with growing content of chlorophyll-
a
. The curve
describing microzooplankton grazing rate shows the
fastest increase in the beginning, within the range of
chlorophyll-
a
concentration from 0.1 mg/m
3
to 0.4 mg/m
3
.
The content of this pigment growing on, the
microzooplankton grazing pressure slowed down; its
minimum was associated with the concentration of
chlorophyll-
a
close to 0.6 mg/m
3
. At the significance
level of p=0.05, the specific microzooplankton
grazing rate described by 66% of available prey
abundance. This equation and the plot were generated
using software Sigma Plot 2001 for Windows (Version
7.101). Important factor is the quality of the prey,
particularly the volume of microalgal cells. Equation
derived using multiple regression method indicates
that the variability of the specific grazing activity of
microzooplankton by as much as 71% depends on
chlorophyll-
а
content in the microplankton and on the
average volume of phytoplankton cells:
g = 0.32
1
•
chl
а
– 0.061
•
V
cell
+ 1.260
(R
2
= 0.71, SE = ± 0.20, p = 0.05)
where g is the specific microzooplankton grazing rate,
d
–1
; chl
а
–chlorophyll-
а
concentration, mg/m
3
, and
V
cell
– the average volume of phytoplankton cells, µm
3
.
1.2 The seasonal dynamics of phytoplankton
biomass and the primary production loss due to
microzooplankton
The records made for 2006~2007 evidence three
peaks of phytoplankton biomass which formed in the
Sevastopol bay over the year (Figure 1). Two first, in
June and in September 2006, were both generated
by blooming
Chaetoceros
spp. and estimated close
to 150 and 330 mg С/m
3
, correspondingly. The third,
in February 2007, was due to the small form of
S.
costatum
, with the largest estimate of 60 mg С/m
3
.
Next time the microalgal biomass increased to a
maximum of 250 mg С/m
3
in June 2007. At the
periods of biomass maximums in the bay, the ratio
between the phytoplankton loss and growth (g/µ) was
never greater than 50%~80%, being in conformity
with the relative percentage of primary production
consumed a day by the microzooplankton and
explaining the repeated increases of phytoplankton
production to highest. In July and December 2006 and
in March 2007, the plankton biomass decreased to
lowest whereas the ratio stayed as high as
100%~160%. It means that the quantity of organic
substance of the phytoplankton consumed by the
microzooplankton was equal to or greater than the
primary production, therefore the low phytoplankton
biomass. In Quarantine bay, at phytoplankton biomass
maximums g/µ ratio was estimated 55%~80%. In
November 2006 and in March 2007, the biomass
estimates dropped to lowest values (10~20 mg С/m
3
)
but g/µ ratio was as high as 120%~220%. These
months the daily loss of phytoplankton biomass due to
microzooplankton grazing was larger than the daily
primary production, therefore the low biomass
estimates. In the sea area off the Kruglaya bay’s shore