Phytoplankton as Bioindicators of Water Quality in Saminaka

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Phytoplankton as Bioindicators of Water Quality in Saminaka Powered By Docstoc
					Proceedings of the 2011 INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Dongguan, Guangdong
Province, China. Published by Science Press USA pp 318-322.[Type the document title]




        Phytoplankton as Bioindicators of Water Quality in Saminaka Reservoir,

                                                               Northern-Nigeria
                                 TANIMU Y.1*, BAKO S. P. 1, ADAKOLE J. A1. & TANIMU J. 2
                                (1 Department of Biological Sciences, Ahmadu Bello University, Zaria, Nigeria;
                                 2 Division of Agricultural Colleges, Ahmadu Bello University, Zaria, Nigeria)


Abstract: A small reservoir constructed in 1975 for domestic and agricultural water supply was studied for 12 months which covered six months of wet season

(May to October 2008) and dry season November 2008 to April 2009). Phytoplankton and water samples were collected and analysed using standard methods

at three sampling stations. Number of Phytoplankton species and class abundance showed the order Bacillariophyceae > Cholorophyceae > Cyanophyceae >

Euglenophyceae. The physico-chemical characteristics (Nitrate-Nitrogen, Phosphate-phosphorus, Total Hardness, Total Alkalinity, Electrical Conductivity,

Dissolved Oxygen, biochemical Oxygen Demand and Seechi disc Transparency) of the water in the reservoirs showed significant relationship with

phytoplankton abundance. Shannon-Weiner diversity index showed that species diversity was higher in the dry season than the wet season, the number of

individuals was also higher in the dry season. The presence of organic pollution indicators Euglena gracillis and Oscillatoria sp and a bloom of cyanotoxin

producing Microcystis aeruginosa is a warning sign of the deteriorating condition of the water quality in the reservoir. The concentrations of NO3-N and PO4-P

were high enough to stimulate phytoplankton growth. Conservatory measures need to be enforced to reduce the rate of siltation and further pollution of the

reservoir arising from the human activities in the catchment of the Saminaka reservoir.

Keywords: phytoplankton; reservoir; water quality



1     Introduction
       The droughts of the 1960s in Nigeria led to the construction of a number of small reservoirs to reduce the impact of any further
occurrence on drinking water supply and irrigation. The Saminaka reservoir was constructed in 1975 to provide portable drinking
water to the catchment communities but its location downstream a major human settlement has led to its rapid siltation and sewage
from such communities greatly impair the water quality. Phytoplankton are microscopic plants containing chlorophyll A, that float
or swim on the upper sufaces of water or are suspended in the water column, where they are dependant on sunlight for
photosynthesis[1]. In addition to light and oxygen they require basic inorganic nutrients such as phosphates, nitrates and silicates in
the case of diatoms[2]. They require carbon in the form of carbondioxide and are primary producers in the aquatic environment
serving as food for zooplankton and fish[3]. Phytoplankton growth and periodicity are known to be limited by physical and chemical
variations. Phytoplankton are a concern in water supplies and reservoirs, some algae such as Microcystis, Anabaena, Anabaenopsis,
Aphanizomenon, Cylindrospermopsis are known to produce toxins. A bloom of species belonging to any one or more of the above
genera may result in high risk to health, as they have been reported to accumulate in some aquatic organisms in the Mediterranean
regions[4-5]. They can also alter taste and cause odor problems, water discoloration, or form large mats that can intefere with boating,
swimming, and fishing[6].
2     Materials and Methods
2.1 Study area
       Saminaka reservoir is located in Lere Local Government of Kaduna State. Kaduna State is located in the northern guinea
savannah vegetative zone of Nigeria and has a tropical continental climate, with distinct wet and dry seasons. Three sampling stations
were studied in the reservoir based on the diffrent activities in the catchment during the wet season (May to October 2008) and dry
season (November, 2008 to April 2009).
2.2 Phytoplankton Collection
       Phytoplankton was collected using a conical shape plankton net of 20 cm diameter with a 50 ml collection vial attached to it [7].
Samples were collected at three sampling points. Phytoplankton was identified by consulting texts by [8] and Perry [1].

*
    Corresponding author: yahuzatanimu@gmail.com.
Proceedings of the 2011 INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Dongguan, Guangdong
Province, China. Published by Science Press USA pp 318-322.[Type the document title]




2.3 Physico-chemical Characteristics
     Physico-chemical characteristics of water were analyzed once a month from May 2008 to April 2009. Surface water temperature
was measured in situ using a mercury thermometer. pH and Electrical Conductivity were measured using HANNA instrument
(pH/Electrical Conductivity/Temperature meter model 210). Total Hardness, Dissolved oxygen (DO), Biological Oxygen Demand
(BOD), Nitrate-Nitrogen (NO3-N) and Phosphate-phosphorus (PO4-P) were determined by methods described by [9].
2.4 Statistical Analysis
     Pearson’s correlation coefficient was used to determine the relationship between physicochemical characteristics and
phytoplakton abundance. Seasonal abundance and diversity was compared using PAST (Paleontological Statistics) ver.1.81.
3 Results
     Mean monthly Air Temperature in Saminaka reservoir ranged between 25℃ and 36.67℃ with mean ± SE of (30.96±0.97)℃.
The mean ± SE of Surface water temperature was (26.19±1.07)℃. Secchi Disc Transparency values ranged from 4.36 to 19.33cm,
with a mean ± Standard Error of (7.29±2.19)cm. The highest observed pH value was 8.21 and lowest was 6.46 during the study
period. The mean±SE Electrical of Conductivity (EC) observed was 128.07± 40.00 S/cm. Dissolved Oxygen (DO) varied between
9.1 mg/L to 3.52 mg/L with a mean±SE of (6.16± 0.53)mg/L. Biochemical Oxygen Demand (BOD) values ranged from 0.37 mg/L
to 5.57 mg/L with a mean±SE of (2.60± 0.50)mg/L. The mean ± SE of Alkalinity observed was (4.29± 0.31)mg/L while was (1.46±
0.30) mg/L. Nitrate-nitrogen concentration a highest value of 0.16 mg/L and lowest of 0.02mg/L while phosphate-phosphorus
concentration, had a highest concentration of 0.76 mg/L and lowest of 0.04 mg/L (Table 1).


                           Table 1 Physico-chemical characteristics of the water in Saminaka reservoir
 Months           Water       Transpa-      pH            EC/         DO/        BOD/       Alkalinity/   Hardness/     N03-N/       P04-P/
                Temp/℃       rency/ cm                  (µScm-1)   (mgL-1)    (mgL-1)     (mgL-1)     (mgL-1)     (mgL-1)     (mgL-1)
   May            30           8.17         7.5           93.8        5.82        4.55         7.7          1.07         0.13            0.56
    Jun           28             0         8.21          106.33        4.5         1.2         6.03          1.1        0.08            0.49
    Jul          22.33         19.33       6.75            42          3.6        1.08         2.43          1          0.02            0.76
   Aug           27.33         15.33       6.46          51.77        5.33        2.23         2.43         4.53        0.07               0
    Sep          23.67         4.36        6.82           39.9        3.52        2.13         3.37          1.1        0.07            0.65
    Oct           29             0          7.1          62.97         7.1        0.49         4.87         1.53        0.14            0.59
   Nov            20             0         7.38           60.6        7.65        3.15         4.4           1.6        0.05            0.54
    Dec           21             0         7.36          97.23        6.55        1.98         7.87          1.9        0.03            0.04
    Jan          24.67          16         7.55          12.33         4.9        0.37         9.33         0.83        0.08              0.3
    Feb          28.33         15.67        7.8          180.6         9.1         4.1        13.17         0.97        0.11            0.59
    Mar           29             0         7.93          293.33       8.53        5.57         14.8          1.4        0.16            0.06
    Apr           31           8.67        7.05           496         7.27        4.43         4.8          0.43        0.11              0.1
 Mean±SE      26.19±1.07     7.29±2.19   7.33±0.15   128.07±40.00   6.16±0.53   2.61±0.50   6.77±1.16     1.46±0.30   0.01± 0.01   0.39± 0.08



     Phytoplankton divisions and species observed are shown on Table 2.
     In Bacillariophyta a higher number of Taxa (23), individuals (1652), Shannon (2.5) and dominance (0.87) in the dry season than
in the wet season (16, 864, 2.11 and 0.83 respectively). Dominance was higher in the wet season (0.17) than the dry season.
For the chlorophyta, the number of Taxa (23), number of individuals (436) Shannon Index (2.48) and Simpson Index (0.87) observed
in the dry season were higher than that observed in the wet season (16,813, 2.11 and 0.83 respectively). Dominance in the wet season
(0.17) was higher than that of the dry season (0.13).
     The number of individuals (464), Shannon Index (0.97) and Simpson index (0.56) observed for the Cyanophyta during the dry
season was higher than that observed in the wet season (236, 0.81 and 0.41 respectively), dominance was higher in the wet season
(0.38) than dry season (0.24). The only exception was that the number of taxa observed in both seasons was equal (5).
Proceedings of the 2011 INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Dongguan, Guangdong
Province, China. Published by Science Press USA pp 318-322.[Type the document title]



     In the Euglenophyta, a taxon comprising of eight (8) individuals was observed in the wet season which is lower than the two
taxa and 76 individuals observed in the dry season. For the dry season, dominance was 0.64, Shannon Index 0.55 and Simpson Index
0.36 (Table 3).


                                  Table 2 Phytoplankton species observed in Saminaka reservoir
                Bacillariophyta                             CHLOROPHYTA                 CYANOPHYTA           EUGLENOPHYTA
Actinocyclus sp         Meridion sp           Scenedesmus spp      Cosmarium spp        Oscillatoria spp     Euglena gracilis
Amphora sp              Navicula spp          Oedegonium spp       Coelastrum sp        Saccconema sp        Phacus spp
Chaetoceros spp         Neidium sp            Ulothrix spp         Pediastrum simplex   Rivularia spp
Coconeis sp             Nitzchia spp          Crucigenia sp        Mougeotia spp        Ticodesmium spp
Coscinodiscus spp       Pinnularia spp        Haematococcus sp     Gleocystis sp        Microcystis spp
Cyclotella sp           Pleurosigma sp        Ulothrix spp         Polyedriopsis sp     Spirulina mjor
Cymatopleura spp        Pseudonitzchia sp     Docidium sp                               Merismopedia elegance
Cymbella spp            Rhizosolenia sp       Staurastum spp
Denticula elegance      Rhopalodia sp         Closterium spp
Diatomella spp          Stephanodiscus sp     Tetraedron sp
Fragillaria spp         Surirella ovalis      Micrasterias sp
Gomphonema spp          Synedulnara           Euastrum spp
Gyrosigma sp            Terpsinoe americana   Ankistrodesmus spp
Melosira spp


                       Table 3 Seasonal diversity profile of phytoplankton divisions in Saminaka reservoir
                      Taxa                    Diversity Index       Wet Season             Dry Season
                      Bacillariophyta         Taxa S                     16                    23
                                              Individuals               864                   1652
                                              Dominance                 0.17                  0.13
                                              Shannon H                 2.11                  2.48
                                              Evenness e^H/S           0.5969                0.5165
                                              Simpson indx              0.83                  0.87
                      Chlorophyta             Taxa S                     16                    23
                                              Individuals               813                    436
                                              Dominance                 0.17                  0.13
                                              Shannon H                 2.11                  2.48
                                              Evenness e^H/S            0.38                 0.7664
                                              Simpson indx              0.83                  0.87
                      Cyanophyta              Taxa S                     5                      5
                                              Individuals               236                    464
                                              Dominance                 0.59                  0.44
                                              Shannon H                 0.81                  0.97
                                              Evenness e^H/S            0.42                  0.36
                                              Simpson indx              0.41                  0.56
                      Euglenophyta            Taxa S                     1                      2
                                              Individuals                8                     76
                                              Dominance                  1                    0.64
                                              Shannon H                  0                    0.55
Proceedings of the 2011 INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Dongguan, Guangdong
Province, China. Published by Science Press USA pp 318-322.[Type the document title]


                                                Evenness e^H/S                  1                   0.5
                                                Simpson indx                    0                  0.36


     Dissolved oxygen showed significant positive with Amphora sp (r = 0.46), Melosira sp (r = 0.50), Fragillaria sp (r = 0.65),
Sirurella sp (r = 0.45), Ankistrodesmus sp (r = 0.41), Coelastrum sp (r = 0.40), Gleocystis sp (r = 0.41), Oscillatoria sp (r = 0.51),
Microcystis sp (r = 0.42) and Spirulina sp (r = 0.50). It showed significant negative correlation with Coscinodiscus sp (r = -0.48),
Cymatopleura sp (r = -0.45) and Gomphonema sp (r = -0.58).
     Biochemical oxygen demand showed significant positive correlation with Amphora sp (r = 0.46), Coconeis sp (r = 0.44),
Fragillaria sp (r = 0.65), Sirurella sp (r = 0.45), Scenedesmus sp (r = 0.65), Closterium sp (r = 0.47), Ankistrodesmus sp (r = 0.71),
Pediastrum sp (r = 0.66), Mougeotia sp (r = 0.52), Gleocystis sp (r = 0.57), Oscillatoria sp (r = 0.73), Microcystis sp (r = 0.49) and
Merismopedia sp (r = 0.52). It showed significant negative correlation with Actinocyclus sp (r = -0.41), Coscinodiscus sp (r = -0.65)
and Diatomella sp (r = -0.41).
     Alkalinity showed significant positive correlation with Coconeis sp (r = 0.67), Fragillaria sp (r = 0.66), Gyrosigma sp (r =
0.60), Scenedesmus sp (r = 0.60), Ankistrodesmus sp (r = 0.89), Coelastrum sp (r = 0.47), Pediastrum sp (r = 0.52), Gleocystis sp (r =
0.63) Microcystis sp (r = 0.64) and Spirulina sp (r = 0.50).
     Secchi disc transparency showed significant positive correlation Coscinodiscus sp (r = 0.42) Haematococcus sp (r = 0.54),
Ulothrix sp (r = 0.60), and Phacus sp (r = 0.46). It showed significant negative correlation Navicula sp (r = -0.44) and Microsystis sp
(r = -0.40).
     pH showed significant positive correlation with Coconeis sp (r = 0.40), Scenedesmus sp (r = 0.44), Oedogonium sp (r = 0.56)
Crucigenia sp (r = 0.54), Ankistrodesmus sp (r = 0.44), and Coelastrum sp (r = 0.46). It showed significant negative correlation with
Docidium sp (r = -0.53).
     Electrical conductivity showed significant positive correlation with Fragillaria sp (r = 0.48), Meridion sp (r = 0.81), Neidium sp
(r = 0.80), Sirurella sp (r = 0.48) and Euastrum sp (r = 0.81). It showed significant negative correlation with Coscinodiscus sp (r = -
0.41)
     Alkalinity showed significant positive correlation with Coconeis sp (r = 0.67), Fragillaria sp (r = 0.66), Gyrosigma sp (r =
0.60), Scenedesmus sp (r = 0.60), Ankistrodesmus sp (r = 0.89), Coelastrum sp (r = 0.47), Pediastrum sp (r = 0.52), Gleocystis sp (r
= 0.63) Microcystis sp (r = 0.64) and Spirulina sp (r = 0.50).
4 Discussion
     Bacillariophyta was the dominant flora of the Saminaka reservoir, the dominance of Bacillariophyta over other divisions is
associated with well-mixed waters [10], high pollution, and Electrical Conductivity [11-12].
     The higher abundance of all divisions of phytoplankton in the reservoirs could be as a result of concentration of nutrients
(nitrates and phosphates) in the water during perods of extensive dry season. The increase in abundance of the Cyanophyta and
Euglenophyta in the dry season is an indication of the higher trophic status of the reservoir during the season. These divisions are
indicators of organic pollution organic. The reservoir receives sewage from a number of a number of canals from the human
settlement along its catchment.
     The differences in number of Taxa and number of individuals, Dominance, Shannon-Weiner diversity index (Shannon-H) and
Evenness between seasons may be due differences in temperatures and pH as different phytoplankton divisions obtain nutrition at
different pH and temperatures.
     The observed significant positive correlation between DO and the abundance of some phytoplankton species may be due to the
fact that oxygen is produced during photosynthesis, therefore an increase in phytoplankton abundance comes with a resultant increase
in DO concentration. The observed significant negative correlation between DO and the abundance of some other phytoplankton
species may be due to the reason that increased abundance of phytoplankton may result in increased utilization of DO during
respiration.
Proceedings of the 2011 INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL SCIENCE AND TECHNOLOGY, Dongguan, Guangdong
Province, China. Published by Science Press USA pp 318-322.[Type the document title]



        The observed significant positive correlation between BOD and phytoplankton abundance may be due to the reason that
increased BOD is an indication of increased nutrient load, nutrients are also a vital requirement for phytoplankton growth.
Conversely the observed significant negative correlation between BOD and the abundance of some phytoplankton species may be
due to the reason that increased organic pollution may lead to the death of phytoplankton species that cannot withstand such levels of
pollution.
        The observed significant positive correlation between EC and Hardness with some species of phytoplankton may be due to the
fact that increase in conducting ions which include nutrients and essential elements are required for metabolic processes of
phytoplankton. The observed significant negative correlation between EC and Hardness with some other phytoplankton species may
be due to the fact that increased abundance may also result in increased uptake of these ions.
        The significant positive correlation observed between nutrient load and phytoplankton abundance may be due to the reason that
increased nutrient concentrations leads to a resultant increase in phytoplankton abundance. The observed significant negative
correlation between nutrient load and the abundance of some other phytoplankton species may due to the reason that an increase in
the phytoplankton abundance may lead to increased utilization of such nutrients by these phytoplankton species.
        A significant positive correlation between Transparency and abundance of some phytoplankton species was observed. Increased
Transparency increases the intensity of solar radiation that can be captured by phytoplankton, hence increased photosynthesis and
other metabolic activities with a subsequent increase in population density of phytoplankton. On the other hand, an increase in the
abundance of some other phytoplankton species may reduce transparency and consequently a negative correlation between the
abundance of such phytoplankton species with transparency.
5      Conclusion
        Phytoplankton diversity and abundance is a very important tool in the monitoring of the seasonal changes in the Saminaka
reservoir, showing its deteriorating condition during the dry season. This could be a viable tool both for long term and community
based monitoring putting into consideration of its inexpensive nature and ease to collect data.


References
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[9]     APHA. Standard Methods for the Analysis of Water and Wastewater. New York: American Public Health Association, 1998: 1287.

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