Anyanwu, D.C.

English

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A COMPARATIVE EVAWATION OF EARLY RAINS
PHYTOPL.ANKTON PRODUCTIVITY OF NWORIE AND
OTAMORI RIVERS. OWERRI IMO STATE, NIEROA.
Anyanwu ft C.
Department ofAgricultural Science
A Ivan Ikoku College of Education
Owerri, Imo State of Nigeria.
ABSTRACT
he primary productivity of Nworie and Otamiri Rivers were evaluated with the aim of comparing the
I primary food indices of the two rivers: Observations on major physicio-chemieal and primary
production indices were made once weekly between 0800 1400 hours for 10 weeks. The following mean
observationsviz 25.9°C. 59cm, 6.45, 1.9mg/i, 1.13 mg/i, 737.6mg/i, 19.5 rng/m2/hr, 13.57 mgfm2/hrand
5.16 mg/rn2/hr were made on temperature, turbidity, pH, dissolved oxygen, net photosynthesis,
phytoplanktons, gross production, net production and respiration respectively for Nworie river: while those
of Otamiri river were 27.1°C, 120cm. 5.95., 5.08 mg/i, 2.21 mg/i, 1913.8 mg/i 46.45 mg/m2/hr
27.67mg/m2/hr, 18.77 mg/m2/hr for temperation, turbidity, pH, dissolved oxygen, net photosynthesis,
phytoplanktons, gross production, net production and respiration respectively. The rate of primary
production was found to be significantly higher (P<0.0 1) for Otamiri than Nworie river. Such variation was
however partly attributed to the levels of dissolved oxygen, turbidity, photosynthetic activities and
phytoplankton abundance.
INTRODUCTION
Otaniiri and Nworie rivers are two major rives in
Owerri, Irno State Of Nigeria, and lie between
longitude 60 59' E and 7° 04' E; and latitudes 5028! N
and 5° 3 1' N (Atlas of Imo State) respectively, all
within the rainforest zone of Imo State. The extent
of usefulness of river waters for fish sustenance is a
function of the rate of primary production in such
rivers (IDRC 1987).
Phytoplankton. being the main primary food source
for aquatic organisms, its propagation is essentially
accelerated in relation to water physico-chernical
properties. Torell et al. (2001) recommends an
effective resource management, which they
identified as a major source of institutional
problem, but requires reliable management
information.
Deficiencies in any of these properties e.g. DO2, p11,
etc, however, may result to unproductivity of the
water body due to reduced growth of
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phytoplanktons, zooplantons, benthic organisms
ete, all in continuous symbiosis with fish. Besides,
the deleterious effect of pollutants on rivers and
other water bodies have been observed inimical;
causing reduction on primary productivity of the
waters and even a high level of fish mortality
(Andrew and Donald, 1998; Kyaw, 2001)
This study was therefore designed to compare the
primary productivity ofNworie and Otamiri rivers
with the view to establishing their comparative
advantage for sustenance of aquatic life forms.
Materials and methods
Otamiri river, originates from Egbu in Owerri
North Local government area of Imo State of
Nigeria and lies between longitudes 6° 59' F and 70
04'E, within the rainforest zone of Imo State, The
length of the river from its source to its confluence
at Emeabiam with Uramiriukwa river is 30km.
From there, it continues towards Ozuzu in Etche
local Government Area of Rivers State, where it
joined the Jmo river, which finally empties in the
Atlantic. On the other hand, Nworie river
originates at Egbeada in Mbaitoli Local
Government Area. Into State of Nigeria, and lies
between latitude 5°28N and 5° 3 1'N(Atlaiis of Imo
State). The riverjoins with Otarniri river atNekede
in Owerri West local Government Area of Imo
State at a length of about 8.2km from its origin. It
receives effluents from the Federal Medical Centre,
Alvan Ikoku College of Education, and Fuason
Industry, all in Owerri Municipal Council, Imo
State of Nigeria.
Temperature of the water body was taken using
mercury in glass thermometer at a depth of 10cm;
The pH was determined using pH meter; and
Otamiri Rivers
A temperature of 259°C was observed for Nworie
River while that of Otamiri, was 27.1°C. Similarly,
pH was 645 and 5.95 for Nworie and Otamiri rivers
respectively. There was however no significant
difference in tbese parameters (P>0.05) for Nworie
dissolved Oxygen (1)02) determined using
Dissolved Oxygen meter.
Turbidity was determined using a secchi disc; and.
Photosynthetic and Respiratory activities
determined using light and dark bottle;
Phytoplanton abundance was quantitatively
determined using a towing net, a little below the
surface waters. (stirling 1985; Boyd 1984;
Mackereth. Et all 978; Wetzel and Linkens 1979).
Data generated were analysed using the t-test
technique (steel and Torric, 1980)
Results and discussion
The primary productivity of Nworie and Otamiri
rivers were assesses using a comparative
evaluation of some primary food production
indices of the two rivers (Table 1).
and Otamiri rivers. The temperatures of the two
rivers however fall within desirable range for fish
culture (Raynold and Walsbry, 1975; Chakroff,
1976). Similarly the pH of the water bodies, fall
within the range prescribed by Stirling, (1985), to
55
Table 1: A comparative evaluation of some primary productivity indices of Nworie and
Primary Nworie OtaniiriS.E.M.
Productivity Indices
Temperature (°C) 25.9 27.1 0.83Ns
Turbidity (cm) 59. 0 120 4.03*
PH valve 6.45 5,95 0.28Ns
Dissolved Oxygen (rug/I) 1.90 5.08 0.28*
Net photosynthesis (mg/I) 1.13 2.21 0.13*
Photoplanktons (mg/I) 737.6 1913.8 71.88*
Gross Production (mg/rn2/hr) 19.57 46.45 2.21*
Net Production (mg/m2/hr) 13.83 27.67 4.07**
Respiration water body (mg/mIhr) 5.16 18.77 1 .36
P<O.O1 NS Not significant (P>0M5)
support life form, particularly fish in water.
There exist high significant differences (P<0.0 1)
between the two rivers for Turbidity, DO2, Net
photosynthesis. phytoplanktons, Gross
Production, Net Production, and Respiration. The
levels of Turbidity. dissolved oxygen, Net
photosynthesis, phytoplauktons, Gross production,
Net production. and Respiration (Water body) were
59M0. 1.90, 1.13, 737.6, 19.57, 13.83 5.16
respectively for Nworie River; and 120, 5.08, 2.21,
1913.8, 46.45, 27.67, 18.77 respectively for
Otamiri River.
The difference in turbidity between the two rives
may likely be due to differences in depth, runoff
from catchment areas and pollution. Turbidity is
more pronounced in Nworie than in Otamiri River.
The colour of Nworie River (yellow/brown
colouration) however suggest its turbidity to be as a
result of pollution and suspended materials; but for
Otamiri River, the greenish colouration of the
water is an indication of turbidity due to algae
(Onuoha and Adukwe, 1987).
Larkin (1976) noted that the speed at which water
flows helps in regular replenishment of oxygen.
Hence, based on water movement a river can be
lotic as in Otamiri River and limnetic as in Nworie
River. Pollution is therefore associatcd to limnetic
waters; the difference in DO, between the two rives
may principally be due to the water movements.
The photosynthetic activities of the two rivers were
significantly different (p<O.Ol) between them.
This difference may however be as a result of
turbidity differences between the two rivers.
56
Welcome (1985), and Onuoha and Adukwe
(1987) noted that turbidity affects photosynthetic
activity of a water body. Earlier, Beadle (1974)
noted a minimum of 50cm. The phytoplankton
abundance and primary production of the two
rivers were significantly different (p<0.O 1). The
growth of phytoplanktons requires light for
photosynthesis. The deficient light penetration
and limitation in photosynthetic activities create
room for differences in phytoplankton abundance
of the two rivers. The rate of primary production
of 19.52 mg/rn2/hr in Otamiri River if continued in
the same rate, yields a daily primary production o
1114.8mg/ni2 and 468.48 mg/rn' in Otamiri and
Nworie rivers respectively. There may however
be other sources of primary production other than
phytoplankton abundance. These may include
influx from atmosphere e.g. seeds and pollen
grains, fragments of disintegrated plants and
insets, as well as synthesis by land plants within
the eatchmcnts area, and transported to the river
by the inflow. This process is called
allochthonous (Beadle. 1974). Theiefore, based
on OEDC (1968) classification of water, Nworie
River is mesotrophic (245-540 mg/in') while
Otamiri River is eutrophic (600 mg/rn2 and
above). This corresponds to the orthograde and
heterograde distribution of dissolved oxygen for
Nworie and Otamiri rivers respectively. Based
on phytoplankton and primary production of the
rivers (OEDC 1968), Nworie River is poorly
productive, while Otamniri River is more
productive. The differences in primary
productivity of the two rivers were partly due to
the DO, photosynthetic activities, turbidity, and
phytoplankton abundance.
CONCLUSION
The rate of primary production was found to be turbidity, photosynthetic activities and
significantly higher (p<O.Ol) for Otamiri River phytoplankton abundance. Nworie River was
than Nworie River. Such variation was however therefore considered poorly productive, while the
partly attributed to the levels of dissolved oxygen, Otainiri River as riiore productive.
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A comparative evaluation of early rains phytoplankton productivity of Nworie and Otamiri rivers, Owerri, Imo State, Nigeria

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A comparative evaluation of early rains phytoplankton productivity of Nworie and Otamiri rivers, Owerri, Imo State, Nigeria

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