International Journal of Marine Science 2016, Vol.6, No.28, 1-9
3
maximum was found at station 7 (Table 1). Generally, temperature is influenced by the intensity of solar radiation,
evaporation, freshwater influx and cooling and mix up with ebb and flow from adjoining neritic waters. The
variation of temperature is attributed by humidity and solar radiation (Das,
et al
., 1997). Low atmospheric
temperature is mainly based on the high rate of humidity. However, high temperature might be due to higher solar
radiation.
It was noticed that, pH of water varied from 7.08 to 8.60 with an average of 8.15 ±0.34 around the study area.
The maximum pH was noticed in station 3 which might be due to the influence of seawater penetration and high
biological activity (Das
et al
., 1997) and the minimum value was observed in stations 5 &7 (Table 1). Variations
in pH of oceanic waters are attributed to factors like removal of CO
2
by photosynthesis through bicarbonate
degradation and high biological activity (Subramanian and Mahadevan, 1999).
Table 1 Physicochemical and biological characteristics of chosen sampling sites in Gulf of Mannar region.
Station
code
Station
Name
At.Tem
°C
Wat.
Tem °
C
pH
Salinity
‰
DO
mg
l
-1
Nitrit
e
µmol
/l
-1
Nitrate
µmol/l
-1
Phosp
hate
µmol/
l
-1
Silica
te
µmol/
l
-1
Densit
y
(No/m
3
Taxa
(Nos)
Diversit
y
Evenness
S1
Vembar
30.3
30.1
8.3
35.0
5.4 2.64
6.30
08.5 12.0 8571
48
3.50
0.960
S2
Periyaku
lam
33.0
32.2
8.4
36.2
4.28 3.33
7.40
29.5 32.0 11733 56
3.42
0.949
S3
Valinoa
kkam
31.5
31.0
8.6
35.0
4.3 1.98
4.30
07.08 08.6 6347
52
3.29
0.942
S4
Ervadi
33.2
32.8
8.5
36.1
4.47 2.40
4.35
06.95 10.1 5520
83
3.97
0.966
S5
Keelaka
rai
32.5
32.0
7.8
35.0
4.36 3.18
4.15
10.05 07.9 4187
33
2.51
0.833
S6
Periyapa
ttinam
33.0
34.0
8.1
33.0
5.2 1.58
3.50
09.15 08.0 1913
34
2.97
0.925
S7
Puduma
dam
32.0
32.1
7.8
34.0
4.52 3.20
6.30
09.00 17.0 2767
36
2.75
0.892
S8
Ramesw
aram
33.5
33.2
7.9
34.5
5.3 3.40
6.80
08.50 21.0 7036
54
3.35
0.928
S9
Dhanush
kodi
31.3
31.5
8.0
34.0
6.5 7.50 19.00 08.10 18.0 6000
43
3.17
0.929
The salinity of oceanic water acts as a limiting factor in the distribution of living organisms. Dissimilarity of
salinity is caused by dilution and evaporation of oceanic water, which is most likely to influence the fauna
(Gibson, 1982). From the nine study areas, salinity was observed to be within the range of 33 to 36.2 ‰ with an
average of 34.75 ± 1.02 ‰ (Table 1). Among all the studied areas station 2 oceanic waters has maximum salinity,
which might be attributed to the low rainfall, higher rate of evaporation at this station.
The observed dissolved oxygen concentration varied from 4.28 to 6.5mg l
-1
with an average of 4.28 ±0.77.
