O A

466
Advances in Environmental Biology, 7(3): 466-470, 2013
ISSN 1995-0756
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLE
Spatio-temporal Distribution to Phytoplankton in the Industrial Area of Calabar River,
Nigeria
1
E.E. Ewa, 2A.I. Iwara, 1A.O. Alade and 2J.A. Adeyemi
1
Dept. of Geography & Environmental Science, University of Calabar, Nigeria
Dept. of Geography, University of Ibadan, Nigeria
3
Institute of Geosciences & Space Technology, UST, Port Harcourt, Nigeria
2
E.E. Ewa, A.I. Iwara, A.O. Alade and J.A. Adeyemi; Spatio-temporal Distribution to Phytoplankton in
the Industrial Area of Calabar River, Nigeria
ABSTRACT
Phytoplankton is an important microscopic organism that sustains majority of aquatic life forms with its
primary productivity. Literature on the abundance and distributional pattern of phytoplankton in the Calabar
River is not readily available. A study was carried out to examine the spatio-temporal distribution, species
abundance and diversity of phytoplankton in the Calabar River. Phytoplankton samples were collected by
trawling plankton net behind an engine boat across six (6) sampling stations. Result obtained showed that a total
of 35 phytoplankton species and 35 taxa representing 6 families were recorded. Chlorophyceae (green algae)
and Bacillariophyceae (diatom) were the most abundant phytoplankton families constituting 57.2% of total
phytoplankton taxa density, the least encountered families were Cyanophyceae (blue-green algae),
Chrysophyceae and Xanthophyceae with 8.6% respectively. The result showed seasonal variation in
phytoplankton species, as its abundance increased in the dry season than in the wet season primarily due to the
increase in photic depth as well as the reduction in input turbid materials from other tributaries of the Calabar
River. The study therefore reveals pollution of the Calabar River characterized by the abundance of
phytoplankton taxa.
Key words: Calabar River, Water Pollution, Phytoplankton, Distribution Pattern, Abundance, Diversity
Introduction
The Calabar River is the major sink of industrial
and municipal wastes, but despite its hydrological
importance, not much study has been carried out to
investigate the distributional pattern and density of
phytoplankton. Previous studies by Akpan[3], Moses
[22], Ekwu and Sikoki [12] concentrated primarily
on the Cross River neglecting the Calabar River
which transverses human settlements, farmlands and
industries. In Nigeria and elsewhere, studies have
been carried out to examine the spatial distribution,
abundance and diversity of phytoplankton
[18,8,24,2,21,7,23,25], these studies identified
different factors based primarily on the nature of
anthropogenic activities predominate in the area to
influence phytoplankton growth, composition and
abundance. However, some of the factors reported in
literature to influence phytoplankton growth,
composition and abundance include dissolved
oxygen, salinity, transparency, water temperature,
calcium and total hardness, increase in river flow,
wastes and oil pollution, silicates among others
factors.
Phytoplankton is an important microscopic
organism that synthesizes and sustains the majority
of aquatic life forms. Phytoplankton is thus, the
pioneer of an aquatic food chain; as the productivity
of an aquatic ecosystem directly depends on the
density of phytoplankton. The population of
phytoplankton in any aquatic ecosystem constitutes a
vital energy flux in the food chain. As the lowest
members of the most aquatic food chain,
phytoplankton is usually very numerous in numbers
and of diverse shapes. Though, they constitute the
starting point of energy transfer. It is however highly
sensitive to allochthonously imposed changes in the
environment [12,20,13] as a result of oil pollution
and municipal waste disposal. Thus, the
spatiotemporal distribution of the species, relative
abundance and composition are an expression of the
environmental health and quality of the existing
water body. On this note, Forsberg [15] argued that
phytoplankton diversity, distribution, abundance and
variation provide vital information of energy
turnover in the aquatic systems.
Indeed, in the aquatic system, Laskar and Gupta
[21] reported that phytoplankton is of immense
importance as a major source of organic carbon
Corresponding Author
E.E. Ewa, Dept. of Geography & Environmental Science, University of Calabar, Nigeria
Email: [email protected]; Phone: +2347058219232
467
Adv. Environ. Biol., 7(3): 466-470, 2013
found at the base of the system (aquatic ecosystem).
Therefore, the variations in the species composition
give a reflection of inherent modification in the
ambient condition within the aquatic ecosystem [8].
Calabar River, a major tributary of the Cross River is
identified to have contributed one of the highest
quotas of fish production and income for most
households [3], and it forms the basis for the earliest
settlement [11,12]. This study was therefore carried
out to examine the spatio-temporal distribution,
species abundance and diversity of phytoplankton in
the Calabar River.
Materials and Methods
Qualitative and quantitative analysis of
phytoplankton was performed using Zeiss invented
plankton microscope. Subsamples were mixed by
swirling and filled into Hdro-Bios plankton
sedimentation chambers. After allowing for complete
sedimentation (4 hrs), microscopic analysis was then
performed following UNESCO [30] using
identification schemes of Edmondson [10], Prescott
[27] and Sharma [29]. The numerical abundance of
the phytoplankton was done by direct count method,
while percentage abundance was calculated using the
formula % = n/N x 100. Species diversity index was
determined by the formula Shannon-Wiener’s
Diversity Index [28], while species evenness was
calculated also using Shannon’s Equitability (E).
Study area:
Results and Discussion
The study was carried out in the Calabar River.
Cross River is located on latitude 50 6′ N and
longitude 80 9′ E enclosing Esuk Nsidung in Calabar
South and Adiabo Bridge in Odukpani Local
Government Area. Calabar River, a major tributary
of the Cross River originates from the Oban Hills in
Cross River State and flows through black shale and
siltstone, clayey, sand and silt deposits before
entering the estuary at Alligator Island [14]. It
stretches about 25km to the north and south. The
Calabar River is hydro-dynamically homogenous.
The current velocity is measured to the range of 2 –
25 cm/sec upstream and 20cm/sec downstream [5].
The current is said to be higher during ebb tide and
decreases during flood tide. Dissolved particulate
materials are transported by surface current from
estuary into creek and upper reaches of the Calabar
River within the industrial area of Esuk Nsidung to
Adiabo Bridge during semi-diurnal tides. The major
occupation of peoples in the area is artisanal fisheries
and trading. Rainfall is the major climatic factor that
affects the hydrology of the Calabar River system
and temperature in the area ranges between 180 C
and 260 C [5]. Vegetation around the area is typical
of tropical rainforest. The land has an undulating
topography and the environment is swampy.
Sampling:
Phytoplankton samples were collected by
trawling plankton net of 55µm mesh size of 5 knots
per minutes for ten minutes across each equidistant
station of 3,340.3m behind an engine boat. Plankton
filtered from such catch was washed into 2 litres
plastic bottles and immediately preserved with 5
drops of 4% formalin [26]. This was followed by the
addition of 3 drops of lugols solution and allowed to
settle for 30 minutes. All the samples were kept in
ice-boxes of 400 C before taken to the laboratory for
analysis.
Analysis:
A total of 35 phytoplankton species and 35 taxa
representing 6 families were recorded during the
study (Table 1). 35 phytoplankton taxa were
recorded of which 10 (28.6%) belong to
Chlorophyceae (green algae) and Bacillariophyceae
(diatom) respectively, 6 (17.1%) to Euglenophyceae
(green flagellates), 3 (8.6%) to Cyanophyceae (bluegreen algae), Chrysophyceae and Xanthophyceae
respectively. The table shows there is seasonal
variation in phytoplankton taxa, as its abundance
increased in the dry season than in the wet season.
Across the sampling stations, the major taxa of
phytoplankton in terms of diversity and abundance
for the family Chlorophyceae were Eudorina spp,
Chlorocoum
spp,
Closterium
spp
and
Acanthosphaera spp. There were high density and
abundance of Chlorophyceae in station 2, followed
by station 4 and 5, while station 6 recorded the
lowest abundance of Chlorophyceae in the two
seasons. In addition, the Margelef’s Index showed
that stations 1 and 6 were the richness in terms of the
number of species of the family Chlorophyceae
across the seasons (Table 1).
The highest abundance of Chlorophyceae
between the seasons and sequence decreased in
station 2 – 6. For the family Euglenophyceae,
Euglena spp, Cyptoglena spp, Phacus pleuroneites
and Trachelomonas spp were more abundant species
across the sampling stations; while stations 5, 4 and 6
recorded the highest species composition belonging
to Euglenophyceae in the two seasons, while station
recorded the least (2 & 3) abundance (Table 1). In
addition, Nitizohia spp, Fragilaria spp, Bacillria spp
and Melosira granulate were the dominant species of
Bacillariophyceae across the sampling stations.
There were high composition and abundance of
Chlorophyceae in station 4, followed by station 5 and
2, while station 6 recorded the lowest abundance of
Chlorophyceae in the two seasons (table 1). The
family Chrysophycea, Pyaetharminon and Chrysapsi
were the dominant or more occurring species across
the sampling stations, with stations 2 recording the
468
Adv. Environ. Biol., 7(3): 466-470, 2013
highest species composition and abundance of the
family Chrysophycea, followed by 5 and 6, while
station 3 had the least abundance of Chrysophycea in
the two seasons.
For the family Cyanophyceae, Microcystic spp
and Oscillatoria spp were species with high
abundance across the sites, with station 5 recording
the highest abundance of the family Chrysophycea,
followed by station 1, while station 6 recorded the
lowest. The Margalef’s Index reveals that stations 2
and 3 were more diverse and richer than other
stations across the seasons. The high abundance of
Cyanophyceae which is noted as an estuarine species
is attributable to the occasional insurgence of
discharge from the estuary during tidal perturbation.
For the family Xanthophyceae, Chlorocloster spp and
Monocillia spp were species with high level of
abundance across the sites. Station 4 had the highest
abundance of the family Xanthophyceae, followed by
station 6 and station 3, while station 2 recorded the
lowest (Table 1). Table 2 represents the summary of
the percentage composition of phytoplankton during
the dry season. The information depicts that in the
dry season, the family Bacillariophyceae had the
highest percentage composition across the sampling
stations, and this was closely followed by
Chlorophyceae and Euglenophyceae respectively.
Furthermore, the information in table 3 shows that
during the wet season, the family Bacillariophyceae
exhibited the highest density and composition
followed by the families Chlorophyceae and
Euglenophyceae. In all, the information in tables 2
and
3
indicates
that
Bacillariophyceae,
Chlorophyceae and Euglenophyceae had the highest
level of composition in the two seasons.
Table 1: Seasonal variation in the composition, diversity and abundance of phytoplankton taxa.
Phytoplankton
Stn 1
Stn 2
Stn 3
Stn 4
Abundance
Abundance
Abundance
Abundance
Dry
Wet
Dry
Wet
Dry
Wet
Dry
Wet
Euglenophyceae
Phacus pleuroneites
4132
916
1104
904
1001
608
1507
963
Trachelomonas spp
1038
832
1043
834
1073
876
1443
841
Pedinipsis spp
542
248
464
219
368
109
548
231
Euglenopsis spp
586
342
828
528
738
447
801
643
Euglena acus
2504
952
2689
964
2904
448
2904
986
Cyptoglena spp
1508
924
1568
108
1698
782
1660
914
No. of taxa (s)
6
6
6
6
6
6
6
6
Total abundance (N)
7610
4214
7696
3575
7782
3270
8863
4578
Margalef”s Index (d)
0.26
0.27
0.26
0.28
0.26
0.27
0.25
0.26
Species evenness (E)
0.24
0.25
0.24
0.25
0.24
0.25
0.24
0.24
Bacillariophyceae
Diatomella spp
Denticula thernalis sp
Coscinodiscus spp
Aulocadiscus spp
Actinocydus spp
Melosira granulate
Tribonema spp
Nitizohia spp
Fraqlatia spp
Bacillaria spp
No. of taxa (s)
Total abundance (N)
Margalef’s Index (d)
Species evenness (E)
692
639
639
368
438
1001
830
1670
1604
1401
10
9282
1.0
0.46
464
613
481
194
278
826
617
908
914
846
10
6141
1.0
0.46
752
705
659
481
593
1934
898
1706
1348
898
10
9974
1.0
0.46
646
568
369
174
505
1000
448
944
905
706
10
6265
1.0
0.46
634
844
706
498
447
1030
849
1449
1403
1340
10
9200
1.0
0.42
441
553
407
518
316
841
216
908
911
941
10
6052
1.0
0.46
689
809
811
698
690
980
782
1503
1433
1368
10
9763
1.0
0.46
541
735
603
517
481
511
509
918
933
914
10
6663
1.0
0.46
Stn 5
Abundance
Dry
Wet
Stn 6
Abundance
Dry
Wet
1802
1708
624
412
2801
1812
6
9159
0.26
0.24
814
922
314
141
1441
814
6
4446
0.28
0.25
1662
1720
638
802
2602
1443
6
8867
0.26
0.24
824
914
316
573
1009
944
6
4630
0.27
0.25
693
938
938
734
738
1007
698
1630
802
934
10
1012
1.0
0.46
473
388
531
273
588
591
448
908
948
994
10
6142
1.0
0.46
898
848
748
866
498
1080
993
1938
950
1090
10
9909
1.0
0.46
681
608
507
404
209
911
465
814
621
926
10
4146
1.0
0.46
Table 2: Summary of the percentage composition of phytoplankton during the dry season.
Phytoplankton
Stn 1
Stn 2
Stn 3
Stn 4
A
%Ra
A
%Ra
A
%Ra
A
%Ra
Bacillariophyceae
9282
28.5
9974
87.3
9200
28.4
9763
26.6
Chrysophyceae
2620
8.1
3910
10.7
2317
7.1
2478
6.7
Cyanophyceae
2586
8.0
258
6.9
2123
6.6
2892
7.8
Chlorophyceae
8244
25.3
10340
3.31
8707
26.9
9342
25.4
Euglenophyceae
7610
23.4
7696
2.07
7782
24
8863
24.1
Xanthophyceae
2205
6.8
2086
5.71
299
7.1
3412
9.3
Total
32547
100
36519
100
32430
99.9
36750
100
Stn 5
A
%Ra
10112
27.1
3774
10.1
2526
7.7
9649
25.9
9159
24.5
2112
5.7
37332
100
Stn 6
A
%Ra
9909
28.1
3620
10.3
2101
6.0
8342
23.7
8867
25.2
2418
6.9
35254
100
Table 3: Summary of the percentage composition of phytoplankton during the wet season.
Phytoplankton
Stn 1
Stn 2
Stn 3
Stn 4
A
%Ra
A
%Ra
A
%Ra
A
%Ra
Bacillariophyceae
6141
29.4
6265
31.1
6055
31.8
6662
28.3
Chrysophyceae
1400
6.7
2028
10.1
1233
6.5
1723
7.3
Cyanophyceae
1708
8.2
1373
6.8
1268
6.7
2395
10.2
Stn 5
A
%Ra
6142
29.3
2063
9.9
1355
6.5
Stn 6
A
%Ra
6146
30.1
2193
10.7
980
4.8
469
Adv. Environ. Biol., 7(3): 466-470, 2013
Chlorophyceae
Euglenophyceae
Xanthophyceae
Total
5795
1646
4214
20904
27.7
7.9
20.2
100
5879
1019
3557
20121
29.2
5.1
17.7
100
5604
1591
3270
19018
Discussion:
The
seasonal
distribution
pattern
of
phytoplankton density reveals it to be high in the dry
season than during the wet season. The high of
phytoplankton in the dry season may be attributed to
the increase in photic depth due to solar radiation
intensity as well as the reduction in input turbid
materials from other tributaries of the Calabar River.
The abundance of phytoplankton density during the
dry season is contrary to those of Wojciechowska et
al., [32], when they observed that in the floodplain
lakes of Bug river, eastern Poland, both diversity and
abundance of phytoplankton were highest in summer.
Similarly, Garcia de Emiliani, [17] observed high
density of phytoplankton during the summer in the
floodplain lakes of Argentina. The drastic reduction
in the population of Euglenophyceae in dry could be
attributed to the use up of essential nutrients during
their
boom
[9].
Maximum
growth
of
Bacillariophyceae in dry could be linked to the
increased water temperature as has also been shown
by Kant and Anand [19], Laskar and Gupta [21]. The
high level of Bacillariophyceae may be probably due
to the present of high concentration of silicates
intrusion from the estuarine region during tidal
incursion. Its high level could also indicate pollution
in the water system. Akpan [2,3] noted that such
pollution includes oxygen deficiencies leading to fish
mortality, release of poisonous chemicals by toxic
dinoflagellates leading to food poisoning through
contaminated shellfish and reduction in aesthetic
value of water. Flagellates like diatoms are proficient
in their ability to reproduce. By splitting into half, a
dinoflagelate can reproduce thirty three million
offspring in only twenty-five divisions.
Ekeh and Sikoku [11] also reported abundant
level of Bacillariophyceae in the lower reach of the
estuary. In a similar way, Akpan [3] reported a strong
correlation between silicates and diatom abundance.
The present study reveals that the percentage
composition of Chlorophyceae is quite high in both
seasons. Despite a low percentage composition in
wet season, they have a sizeable population. The
boom of Chlorophyceae in dry could be attributed to
high water temperature and resultant dilution of
water [31]. Gabellone et al., [16] suggested that the
four major regulatory factors of the ecology of the
pond of floodplain ecosystem are dry season, a high
and sudden increase of river flow, increase in
particulate material and clear water conditions. The
decrease in abundance of Chlorophyceae from
stations 2 – 6 may be attributed to the prevalence of
freshwater from the upstream to the downstream of
the river. A study in a shallow lake in the south of
Brazil identifies transparency and water temperature
29.5
8.4
17.2
100
6274
1897
4578
23529
26.7
8.1
19.5
100
5593
1341
4446
20940
26.7
6.4
21.2
100
4655
1806
4630
20410
22.8
8.8
22.7
99.9
as environmental variables influencing the variation
of phytoplankton composition [6]. Our study
attributed the density of phytoplankton taxa to
primarily the pollution of the water body as well as
the high concentration of silicate.
Conclusion:
The study shows the Calabar River has high
diversity of phytoplankton taxa as a result of nutrient
input mostly the discharge of organic wastes. The
variation in phytoplankton abundance across the
sampling station is attributed to oil pollution and the
discharge of organic waste into the river. The
presence and abundance of phytoplankton taxa is
indicative of water pollution.
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