International Journal of Marine Science 2016, Vol.6, No.01, 1-8
2
Growth rate of microalgae is influenced by environmental
conditions (Renaud et al., 2002). Microalgae growth
and composition may be influenced by nutrients like
nitrate, phosphate and silicate (Paerl, 2009). The
influence of nitrate and phosphate concentrations on
growth, extracellular polysaccharide production, and
fatty acid profile of marine diatoms has been reported
(Liang et al., 2006). Modifications in culture medium
such as nitrogen, phosphorus and silicate
concentrations affect the growth rate of microalgae,
cellular composition and fatty acid profile of the lipid
fraction (Sanchez et al., 2000). Fried et al. (2003)
evaluated the effects of nine different combinations of
nitrate and phosphate concentrations on the algal
growth by measuring relative chlorophyll levels. They
concluded that both nitrates and phosphates have
positive effects on the algal growth. However, these
variables affect the algal growth independently of each
other and there is no interaction between the two. This
implies that both nitrates and phosphates are effective
limiting nutrients that can be reduced to control algal
profile. Hemalatha et al. (2012) studied the combined
effects of temperature, nitrate and silicate on growth
of the marine diatom,
Chaetoceros simplex
. The
growth rate was directly proportional to nutrient
concentration and temperature, whereas chlorophyll-
a
and biochemical composition were directly
proportional
to
the
nutrient concentrations.
Karthikeyan et al. (2013) investigated the suitability of
the marine diatoms,
Chaetoceros curvisetus
and
Chaetoceros
simplex
for
the
removal
of
macronutrients from different wastewater. The growth
and nitrate-phosphate removal properties were studied
with nitrate, ammonium and urea nitrogen sources.
The results indicated the
Chaetoceros simplex
was
more efficient than
Chaetoceros curvisetus
and
suitable for the removal of macronutrients when
cultured with urea and nitrate nitrogen sources.
Recently,
Chaetoceros simplex
was examined for its
growth and biochemical compositions in different
nitrate, phosphate and silicate concentrations by
Hemalatha et al. (2014).
Aim of the work
The aim of the present work is to study the response
of growth, photosynthetic pigments, carbohydrates,
total soluble proteins and total lipids of
Chaetoceros
simplex
Ostenfeld to different treatments of nitrates
and phosphates.
Materials and Methods
Isolation and purification of the organism
One liter of sub-surface seawaters was collected from
Hurgada in carefully cleaned polyethylene bottle and
passed immediately through plankton net of 100 μm
mesh size to eliminate the macrozooplankton. This
water was supplemented in the laboratory with F/2
medium (Guillard and Ryther, 1993 ). This is a
common and widely used general enriched seawater
medium designed for growing coastal marine algae,
especially diatoms. This culture was poured in several
conical flasks of 500 ml capacity (250 ml were added
in each one) and incubated for 12 days at 25±1 °C
under day light fluorescent lamps of about 6400 LUX.
The algal cultures were supplied with dry air to
provide CO
2
necessary for photosynthesis, to prevent
the settling of the cells at the bottom of the containers
and to maintain the algae in suspension without
mechanical stress. The grown cells were examined
under a binocular research microscope and identified
as
Chaetoceros simplex
Ostenfeld. For accurate
identification of the isolated cells; scanning electron
microscope (SEM–JEOL-JSM5300) was used
according to Ashour (2011) (Fig.1). Generally, the
isolation and purification of
C. simplex
was carried
out by the dilution method (Droop, 1954) and Picking
up Capillary method (Stein, 1973).
Preparation of different treatments of nitrate and
phosphate
In the collected water samples from Hurgada; the
concentration of nitrate was 2.27μM and the phosphate
value was 0.5 µM (Nassar et al., 2014). Thus, in this
study, a six different treatments of nitrate were used as
follows; 1 µM (below detected concentration), 5 µM,
50 µM, 100 µM, 200 µM and 300 µM (above detected
concentration). Whereas, five different concentrations
of phosphate were used as follows; 0.3 µM (below
detected concentration), 1 µM, 5 µM, 25 µM and 50
µM (above detected concentration). Totally three
triplicate experiments at the different treatments of
phosphate and nitratewere carried out separately for 12
days under temperature 25±1 °C and day light
fluorescent lamps of about 6400 LUX, pH 8.0–8.4 and
salinity 35 ‰.
