A Preliminary Observation on Water Quality and Plankton of an Earthen Fish Pond in Bangladesh: Recommendations for Future Studies
Md. Yeamin Hossain,
Abu Hanif Md. Ibrahim,
Zoarder Faruque Ahmed,
Mohamed A.H. El-Kady
Md. Abdul Wahab
The present study provides a characterization of water quality and plankton samples in earthen fish pond in Rajshahi, Bangladesh. Sampling was done over a period of six months, running from October, 2004 through March, 2005. All the water quality parameters were within the optimal ranges for plankton productivity. Temperatures varied from 19.75 to 27.25°C; transparency, 24.75-29.50 cm; pH, 6.62-7.85; Dissolved Oxygen (DO), 3.87-5.85 mg L-1; free CO2, 5.25-7.25 mg L-1 and bicarbonate (HCO3) alkalinity, 81.25-147.5 mg L-1. Analyses of plankton samples recorded a total of 5 classes phytoplankton viz.; Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae, Euglenophyceae and 2 classes of zooplankton; Crustacea and Rotifera. The phytoplankton population was comprised of 17 genera belonging to Cyanophyceae (5 classes, 34.47%), Bacillariophyceae (3, 13.87%), Cyanophyceae (3, 34.48%), Euglenophyceae (3, 10.68%) and 1 to Dinophyceae (6.50%). The zooplankton population consisted of 10 genera belonging to Rotifera (4, 40.13%) and Crustacea (6, 59.87%). Phytoplankton and zooplankton abundance varied from 60800 to 239400 units/1 and 7620 to12160 units/1, respectively. It is concluded that the phytoplankton groups provide the main support for earthen pond aquaculture in the pond compared to zooplankton classes. The information provides for more research to compare water quality and pond plankton characteristics in earthen aquaculture systems with and without fish stocking. Further studies on the seasonal changes of water quality parameters and its effects on plankton production in the fish ponds and all year extended monitoring is recommended in future studies.
to cite this article:
Md. Yeamin Hossain, Saleha Jasmine, Abu Hanif Md. Ibrahim, Zoarder Faruque Ahmed, Jun Ohtomi, Bernerd Fulanda, Momtaz Begum, Abdullahil Mamun, Mohamed A.H. El-Kady and Md. Abdul Wahab, 2007. A Preliminary Observation on Water Quality and Plankton of an Earthen Fish Pond in Bangladesh: Recommendations for Future Studies. Pakistan Journal of Biological Sciences, 10: 868-873.
Water quality, i.e., the physico-chemical and biological characteristics
of water, plays a big role in plankton productivity as well as the biology
of the cultured organisms and final yields. Water quality determines the
species optimal for culture under different environments (Dhawan and Karu,
2002). The overall productivity of a water body can easily be deduced
from its primary productivity, which forms the backbone of the aquatic
food chains (Ahmed and Singh, 1989). The plankton community is comprised
of the primary producers or phytoplankton and zooplankton; the secondary
producers (Battish, 1992). The phytoplankton population represents the
biological wealth of a water body, constituting a vital link in the food
chain. The zooplankton forms the principal surce of food for fish within
the water body (Prasad and Singh, 2003). Both the qualitative and quantitative
abundance of plankton in a fish pond are of great importance in managing
the successful aquaculture operations, as they vary from location to location
and pond to pond within the same location even within similar ecological
conditions (Boyd, 1982). The physico-chemical attributes of a water body
are principle determinants of fish growth rates and development (Jhingran,
1991). Climate has a major influence on water quality and consequently,
the biodiversity within the water bodies (Boyd and Tucker, 1998). Good
water quality in fish or shrimp ponds is essential for survival and adequate
growth (Burford, 1997).
Little or no studies on water quality and plankton in ponds within Rajshahi
region of Bangladesh have been done, though similar experiments have been
in fish ponds from the Indian sub-continent (Bose and Philops, 1994; Wahab
et al., 1994; Hossain et al., 2006). Therefore, this research
reports on preliminary analyses of the water quality parameters and plankton
composition and abundance, with some recommendations for further studies
in the earthen fish ponds within the Rajshahi region, Bangladesh.
MATERIALS AND METHODS
The experimental pond and physico-chemical parameters: The experiment
was carried out over a period of 6 months, ranging from October, 2004
through March, 2005 on rectangular earthen fish pond of area 120 sqare
decimal and average water depth of 1.2 m in Rajshahi University Campus,
Bangaldesh. The pond was stocked with exotic and indigeous fishes. Lime
was applied before the start of the experiments and cow manure, urea and
triple super phosphate fertilizers used to enhance plankton productivity.
The experimental pond was free from any shading and adequate sunlight
through out the day. Water quality parameters and sampling for plankton
analyses was done once a week between 09.00-11.00 h from specific points
of the pond at a depth of 20 cm below the surface. A mercury thermometer
was used to measure both water and air temperature (°C), while Transparency
(cm) was measured with a secchi disc of 20 cm diameter. Digital electronic
meters (Model YSI-58, USA and Jenway Model-3020) were used to measure
dissolved oxygen (DO) (mg L–1) and pH on site, respectively
while Total alkalinity (mg L–1) and free carbondioxide
(CO2) (mg L–1) were determined titrimetrically
in the laboratory on collected water samples, according to the standard
procedures and methods define in APHA (1992).
Plankton sampling and analyses: Sampling of pond water for plankton
analyses was done on ten-liter water samples sampled from different areas
and depths of the pond and filtered through a 25 μ mesh plankton
net. Preservation of the samples before analyses was done by addition
of 5% buffered formalin in small plastic bottles, before analyses on a
Sedgewick-Rafter counting cell, under a compound binocular microscope
(SWIFT M 4000-D).
Analyses involved transfer of 1 mL sub-sample from each of the samples
to the Sedgewick-Rafter counter and counting of cells within 10 squares
of the cells, chosen randomly. The cell counts were used for compute the
cell density using the Striling (1985) formula where the plankton density
is estimated by-
||No. of plankton cells or units per litre of original
||Total No. of plankton counted.
||Volume of final concentrate of the samples in ml.
||Volume of a field in cubic mm.
||No. of fields counted.
||Volume of original water in liters.
The plankton were then identified up to the genus level and enumerated
by the following (APHA, 1992; Bellinger, 1992). The mean number of plankton
was recorded and expressed numerically per litre of water of the pond.
Statistical analysis: The statistical analysis of different physico-chemical
and plankton parameters were carried out by using one-way ANOVA and any
difference at 5% level of significance using the statistical package of
Statgraphics Version 7, while the Microsoft exell® 2002 was used to
plots graphs for decimination of the results. The results of the plankton
density were expressed as mean±SD.
Physico-chemical parameters: During the study period, water temperatures
varied from 30°C at the initial period of the study to lows of 18°C
in January with related decrease in Secchi disk depth from 29.59 cm in
October to 24.75 cm in February (Table 1). Although
temperatures were within the suitable range for plankton production among
the months, but the variations were significantly differences (p<0.05).
Water depths also decreased from 136.9 cm at the start of the experiment
in October to 85.5 cm in March and was found to vary significantly (p<0.05)
among the months during the experimental period. The lowest and highest
pH levels were recorded in March and December, at 6.0 and 8.2, respectively.
At the start of the experiment, DO levels were generally low, at 3.0 mg
L–1 in October,increasing to 6.1 mg L–1
||Mean±SD values of water quality parameters of
freshwater man-made earthen fish ponds of Bangladesh
|WT, Water Temperature; AT, Air Temperature; DO, Dissolved
Oxygen; CO2, Carbon Dioxide; TA, Total Alkalinity
||Monthly abundance and composition (%) of phytoplankton
and zooplankton (cells L–1) of the pond
However, free CO2 showed a downward trend during the study,
from 7.5 measured in November to 5.2 in February. The variations in pH,
DO and CO2 in the experimental ponds were similar and within
the productive range during study period, although bicarbonate alkalinity
which increased from 70 to 165.0 mg L–1 and was found
to vary significantly (p<0.05) among the months during the same study
Plankton: The plankton population was identified up to genus level
and re-grouped into the various classes or groups as shown in Table
2. Monthly variations of total phytoplankton and zooplankton in the
fish ponds of Bangladesh during October, 2004 to March, 2005 are shown
in Fig. 1 and 2, respectively. The
phytoplankton population was comprised of 17 genera of which falling into
five major groups; Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae
and Euglenophyceae. Within these groups, Chlorophyceae was the most dominant
at 34.48% followed by Cyanophyceae at 34.46%; Bacollariophyceae, 13.87%);
Eulenophyceae, 10.68% and Dinophyceae, 6.50%. Comparison of percentage
among different phytoplankton groups of the fish pond during October,
2004 to March, 2005 is shown in Fig. 3.
||Monthly variations of total phytoplankton in the fish
pond of Bangladesh
||Monthly variations of total zooplankton in the fish
pond of Bangladesh
||Comparison of percentage among different phytoplankton
groups of the fish pond
The zooplankton population consisted of 10 genera, with 4 belonging to
Rotifera (40.13%) and 6 to Crustacea (59.87%). Total phytoplankton population
were significantly higher (p<0.05) in the month of February followed
by March, October, November, December and January. On contrast, in case
of zooplankton abundance, total zooplankton was significantly (p<0.05)
higher in the month of November followed by October, December, January,
February and March.
Water quality parameter and plankton density: During the study
period, variations in water temperature are attributed to weather conditions
and statistical tests showed significant differences (p<0.05) in temperatures
over the months. The observed temperatures are within the optimal ranges
for (18.3-37.8°C) for production of plankton in tropical ponds (Jhingran,
1991; Begum et al., 2003). However Boyd (1982) recommends optimal
temperatures for fish culture, in the range of 26.06-31.97°C, if fish
growth and consequently yields are to be optimized. Similarly, secchi
disk depths recorded (24-30 cm) showed no significant difference, implying
that plankton abundance and productivity levels were similar through out
all months during the study period. Reid and Wood (1979) reported that
the transparency of water depends on several factors such as silting,
plankton density, suspended organic matter, latitude, season and the angle
and intensity of incident light. Measurements of both air and water temperature
showed similar trends and this may be attributed to the small size of
ponds, with water temperatures responding fast to any changes in air temperature
as observed in Table 1. Similar resultings are reported
by Welch (1952) who add that water temperatures in small ponds shows similar
variations as the atmospheric temperatures. A similar correlation was
also observed between temperature and plankton abundance with hotter months
recording higher plankton abundance. However Sreenivasan (1964) further
reported that peaks of plankton abundance occur at different periods in
different years. It should also be noted that temperature alone may not
account for variations in plankton densities as other factors such as
high pH, alkalinity, carbon dioxide and nutrients are also responsible
for the organic production (Pulle and Khan, 2003).
The variations in monthly densities of total phyto- and zooplankton are
therefore attributed to wide range of physico-chemical parameters including
as temperature, dissolved oxygen, carbon dioxide and total alkalinity.
The dominance in plankton species during the various months of the study
period was observably attributed to variations in the optimal conditions
for the particular species. Phytoplankton and zooplankton abundance varied
from 60800 to 239400 cells L–1 and 7620 to 12160 cells
L–1, respectively in the pond and the mean abundance
of phytoplankton was significantly higher (p<0.05) than zooplankton
during the study period. The results of the present study showed that
acceptable ranges of water quality parameters influence the growth of
both phyto- and zooplankton groups. Margalef (1964) also reported that
the phytoplankton population in nutrient rich waters is more diverse than
those in nutrient deficient waters. Verma and Shukla (1970) recorded 30
genera of phytoplankton from Kamala Nehru Tank, Muzaffarnagar, India.
Similarly, Hossain et al. (2006) recorded 38 genera of phytoplankton
and 13 genera of zooplankton during a three month study period in earthen
fish ponds within the Mymensingh region, Bangladesh.
In the study, Chlorophyceae dominated the phytoplankton groups, followed
by Cyanophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae in
the pond. This is attributed to favorable water quality attributes, particularly
high levels of total alkalinity recorded during the study. Similar findings
where high phytoplankton density is recorded are also reported by Seenayya
(1971). The effects of fertilizer application and frequent water change
to avoid development of anoxic pockets within the pond are also to account
for these high levels of plankton productivity observed in the pond. Hossain
et al. (2006) also reports high densities of plankton while working
on fish ponds within the Mymensingh region, Bangladesh Mainly 2 groups
of zooplankton Rotifera and Crustacea were identified in present study.
The results of the present study showed that optimal water quality attributes
especially in relation to total alkalinity has a strong positive influences
the growth of phytoplankton and zooplankton groups in earthen fish pond.
A detailed description of the dynamics of plankton within the pond hasn’t
been given in this study since the samples only cover a period of 6 months.
Hence there is a need to carry out successive studies to look at the dynamics
of the plankton groups within the earthen ponds sampled over several years
in order to fully characterize the variations both due to water quality
and variability in climatic conditions. This information is useful for
the future research as a foundation study towards characterization of
these dynamics within the ponds of the Rajshahi, Bangladesh.
The authors wish to acknowledge the Chairman, Department of Fisheries,
University of Rajshahi, Bangaldesh for the financial supports to carry
out this research. This research is the part of Thesis for A.H.M. Ibrahim,
Masters student of the University of Rajshahi, Bangaldesh. Also the authors
would like to express the acknowledgments to the Editor-in-Chief, PJBS
and anonymous referees for their useful comments.
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