Page TABLE OF CONTENTS: 1 Abstract. 2 1.0 Introduction 4 2.0 Materials and Method 8 2.1 Study Area 8 2.2 Some Physical/Chemical Sample determinations 9 2.2.1 Total Dissolved Solid (TDS) 9 2.2.2 Total Suspended Solid (TSS) 9 2.2.3 Iron 10 2.2.4 Reactive Nitrogen 11 2.3 Collection of Samples 11 2.4 Chlorophyll-a Determination 12 2.5 Community structure Analysis 12 2.5.1 Margelef Index 12 2.5.2 Species Equitability or Evenness 13 2.5.3 Similarity/Dissimilarity Index 13 3.0 Results 14 3.1 Hydro climate Properties 14 1 3.2 Diatom Community 22 3.3 Community Structure Indices 37 4.0 Discussion 39 5.0 Conclusion 43 Acknowledgement 43 References 43-49 A Comparative Study of the Epiphyton and Phytoplankton Biomass in Yewa Lagoon at Iragbo in Relation to Environmental Characteristics. Effiong, K. S1,. and Inyang, A. I2. 1 Department of marine Sciences, Faculty of Natural and Applied Sciences, Akwa Ibom State University, Ikot Akpden, Nigeria. 2 Department of marine Sciences, Faculty of Natural and Applied Sciences, Akwa Ibom State University, Ikot Akpden, Nigeria. Email address: kokoetteeffiong@gmail.com (Effiong, Kokoette Sunday), aniefiokinyang@yahoo.com (Inyang, A. I). Abstract A comparative study of the phytoplankton and epiphyton biomass in relation to environmental characteristics at the Iragbo part of Yewa Lagoon were undertaken for six months (December, 2012- May, 2013). Water temperature (≤32.20C), air temperature (≤ 48.50C), transparency (≤ 48.5cm), pH (≤ 8.16), were higher in dry months while in the wet months total suspended solids (≤ 2 1.3mg/L) and total dissolved solids (≤ 49.0mg/L) values were higher. Dissolved oxygen values (≥ 2.8mg/L ≤ 7.6mg/L) were moderate in the Lagoon while biochemical oxygen demand varied between 7.0mg/L and 16.0mg/L, chemical oxygen demand also varied between 21.0mg/L and 40.0mg/L. Reactive silicates ranged between 0.002mg/L and 0.004mg/L throughout the sampling months. The heavy metal values; Copper (≤0.03mg/L), Lead (≤ 0.017mg/L), Zinc (≤ 0.62mg/L) and Iron (≤ 0.34mg/L) remained low throughout the sampling period.. Both the phytoplankton and epiphyton biomass were higher in the dry months. Phytoplankton chlorophyll-a values were highest in January while epiphyton chlorophyll-a value was highest in February. The pinnate diatoms dominated the epiphyton community while the centrales diatoms dominated the phytpplankton community. A total of 4885 individuals of 76 phytoplankton species belonging to 6 divisions were identified while a total of 2505 individuals of 39 epiphyton species belonging to 4 divisions were identified. For the phytoplankton community, a total of 1565 individuals (31.80%) represent bacillariophyta division while 635 (12.90%), 2535 (51.52%), 115 (2.33%), 15 (0.5%), and 20 (0.85%) represent chlorophyta, euglenophyta, chrysophyta and pyrophyta respectively. For the epiphyton community, a total of 2525 individuals (87.37%) represents bacillariophyta division while 105 (3.69%), 195(6.74%), and 65(2.24%) individuals represent chlorophyta, cyanophyta and euglenophyta respectively. Species used elsewhere for biomonitoring were observed in the lagoon, they include (Euglenoid) Euglena and Phacus species, Trachelomonas hispida, (Diatoms) Gomphonema parvulum, Synedra ovate, Pinnularia major and (Green algae) Chlorella sp. Keywords: Chlorophyll-a, Similarity, Bioindicator, Phytoplankton, Epiphyton. 3 INTRODUCTION: Planktonic algae are free-floating microscopic plants, which obtain chlorophyll and grow by photosynthesis in the presence of sunlight and lacks roots, stems and leaves (Lee, 1999; Nwankwo, 2004a). Phytoplankton are the plant components of plankton that photosynthesize, release oxygen to the environment and serve as food producers in aquatic ecosystems (Mader, 2001). Freely suspended microscopic plant forms are termed phytoplankton; they are photosynthetic organisms that float near the surface water. Whereas forms attached to aquatic macrophytes are termed epiphyton (Nwankwo 2004b). They absorb nutrients from the water or sediments, add oxygen to the water as a by-product and are usually the major source of organic matter at the base of food web in the aquatic environment (Lawson and John, 1987; Lee, 1999). Algae are almost ubiquitous throughout the world, being most common in aquatic habitats. They can be categorized ecologically by their habitats. Planktonic microscopic algae grow suspended in the water, whereas neustonic algae grow on the water surface. Cryophilic algae occur in snow and ice; thermophilic algae live in hot springs; edaphic algae live on or in soil; epizoic algae grow on animals, such as turtles and sloths; epiphytic algae grow on fungi, land plants, aquatic plants or other algae; corticolous algae grow on the bark of trees; epilithic algae live on rocks; endolithic algae live in porous rocks; and chasmolithic algae grow in rock fissures. Some algae live inside other organisms, and in a general sense these are called endosymbionts. Specifically, endozoic endosymbionts live in protozoa or other, larger animals, whereas endophytic endosymbionts live in fungi, plants, or other algae. There are quite a handful of records on the algal flora of south-western Nigeria. Adesalu and Nwankwo (2005), reported a prominent role played by phytoplankton in Ogbe creek. 4 Nwankwo (1984) observed seasonal changes of phytoplankton of Lagos Lagoon and adjacent sea in relation to environmental factors. Onyema and Nwankwo (2008) studied the epiphytic assemblage of a polluted estuarine creek in Lagos. Nwankwo et al. (2008) observed the hydrochemistry and plankton dynamics of Kuramo Lagoon in Nigeria. Plankton studies in the Lagoon also include those of Olaniyan (1957) who investigated the zooplankton, Inyang et al (2015a) who studied the composition of periphyton community on water hyacinth at Ejirin part of Epe Lagoon , Hendey (1964) who studied the phytoplankton and Inyang et al (2015b) who did a comparative study of periphyton on Eichhornia crassipes and Phytoplankton communities at Ejirin part of Epe Lagoon, The coastal area of south western Nigeria, more specifically is a meandering network of lagoons that angle approximately 45 0 to the prevailing south westerlies (Hill and Webb, 1958; Ibe,1988). Of these Lagos Lagoon complex stretches for 257km from Benin Republic to the west in the Niger Delta to the east and consist of nine lagoons. According to Nwankwo, 1993, the lagoons and creeks of south western Nigeria are linked to the sea through Lagos harbour which remains open all through the year. A well defined salinity gradient, linked with the rainfall pattern, extends far inland westwards and eastwards. This area therefore shows major floristic changes along salinity gradient (Nwankwo, 1988). Furthermore, the texture of the bottom sediment maybe described as muddy sand, sandy mud, muddy or coarse with shell material. Since the incursion of water hyacinth (Eichhonia crassipes) into Nigerian coastal waters in September 1984 from the Porto Novo creek (Benin Republic), it has continued to flourish especially in Yewa lagoon that has a direct influence from the Yewa River being fresh water. Some of the immediate problems created by this infestation include blockage of drainages, increase in breeding sites of mosquitoes 5 and snails, interference with fishing and even impairment of navigation (Nwankwo, 1993). Epiphyton is a complex mixture of algae, heterotrophic microbes, and detritus that are attached to submerged surfaces in most aquatic ecosystems. It serves as an important food source for invertebrates (Kadiri, 1992) tadpole and some fishes. It can also absorb contaminants removing them from the water column and limiting their movement through the environment. According to Nwankwo and Amuda (1993), the creeks of south-western Nigeria form part of numerous ecological niches associated with the Nigerian coastal environment. These creeks are of two types; the first is the tidal creek surrounded partly by fresh water swamp from places beyond the rich of tidal influence. The other is the non-tidal fresh water creek surrounded by fresh water swamps and infested with aquatic macrophytes all through the year. Epiphyton algal communities are important components of aquatic ecosystem. Their contribution to primary production varies from 0.2% to 41% in lakes (Laugaste and Reumanen, 2005). Furthermore, the epiphyton algae with macrophyte are employed as the buffering zone of lakes lagoons (Lakatos et al, 1999). They are important components of food webs (Michael et al, 2006). Epiphyton algae are good indicator of water quality and environmental changes due to their sensitivity to external sources of fertilization (Lowe, 1996). Epiphyton is also an indicator of water quality; response to this community to pollutants can be measured at a variety of scales representing physiological to community-level changes. For this reason, epiphyton has often been used as an experimental system in, example pollution induced community tolerant studies (Sladeckova, 1962; Patrick, 1965, 1967 1975; Wilkinson et al, 1976). The 6 importance of aquatics in providing suitable foci for epiphyton algae is well known (Odum, 1957; Saszka, 1975; Cattaneo and Kalff, 1978). Similarly reports by Zoebell and Allen (1933), Wilson (Barbour et al, 1999), Erth (1971) have shown relevance of artificial surfaces in the trapping and study of attached algae. Epiphyton algal communities are important components of aquatic ecosystem. Their contribution to primary production varies from 0.2% to 41% in lakes (Laugaste and Reumanen, 2005). Furthermore, the epiphyton algae with macrophyte are employed as the buffering zone of lakes lagoons (Lakatos et al, 1999). They are important components of food webs (Michael et al, 2006). Epiphyton algae are good indicator of water quality and environmental changes due to their sensitivity to external sources of fertilization (Lowe, 1996). The aim of the study is to carry out the comparative study of epiphyton and phytoplankton biomass of Yewa Lagoon at the Iragbo in relation to environmental characteristics. 7 2. MATERIALS AND METHODS 2.1 Study Area Fig 1. Map of Yewa Lagoon showing Sampling Site. Yewa lagoon is about 17km from the Nigeria-Benin Republic boarder (Egborge, 1988). It lies along the boundary between Ogun and Lagos states, and is perpendicular to Badagry Lagoon (Fig. 1). It lies approximately 6.21km upstream of River Yewa (Egborge, 1988). It experiences the characteristics seasonal rainfall that determines environmental gradients in South-Western Nigeria. River Yewa which is the major river emptying into the lagoos has 8 Ere and Iragbo as tributaries, (Effiong and Inyang, 2015). Mangrove vegetations such as the red mangrove (Rhyzophora sp) and black mangrove (Avicenia sp) are abundant. Some other species of other aquatic floral species also found in abundance include; Paspalum orbiculare, Acrostichum aureum, Phoenix rachinata and Nypa fructicans. Manatees, migratory birds, periwinkle aquatic crab, fishes of various species and snakes make the fauna of Yewa lagoon. Artisanal fishing and sand mining is the major economic activities of the indigenes. 2.2 Some Physical/Chemical samples determination 2.2.1 Total Dissolved Solids (TDS) This was carried out using the Gravimetric method 2540C (APHA, 1998). A wellmixed portion of the sample was filtered and evaporated to dryness (180 oC) in a weighed dish, dried to constant weight. The increase in weight of this dish determined the Total Dissolved Solid (TDS). Calculation mg Total Dissolved Solids (TDS)/L = (𝐴−𝐵)𝑥 1,000,000 𝑆𝑎𝑚𝑝𝑙𝑒 𝑣𝑜𝑙𝑢𝑚𝑒(𝑚𝑙) Where: A = Dish + Dry Sample (g) B = Dish before use (g) 2.2.2 Total Suspended Solids (TSS) This method was carried out using the Gravimetric method 2540D (APHA, 1998). A filter dish was dried at 103 ± 2oC, in an oven for 1hr. The filter was removed and 9 allowed to cool in a desiccator, before being weighed. 50ml of a well-mixed sample was filtered through the filter unit and allowed to drain. The filter dish was removed and dried at 103 ± 2oC in an oven for 1hr. The dish was removed and allowed to cool in a desiccator, and then re-weighed. The increase in weight represented the TSS, and was calculated as follows: TSS (mg/L) = (𝐴−𝐵)(106 ) 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝑡𝑎𝑘𝑒𝑛 (𝑚𝑙) Where: A = weight (g) of dish + residue B = weight (g) of dish before use. 2.2.3 Iron This was carried out using the Perkin Elmer 5000 atomic absorption spectrophotometer. 100ml of thoroughly well mixed water sample was transferred into a beaker and 5ml concentrated nitric acid was added. The beaker was placed on a hot plate and evaporated to dryness. The beaker was then cooled and another 5ml concentrated nitric acid was added. Heating was continued until a light – coloured residue was observed. Then, 1ml concentrated nitric acid was added and the beaker was warmed slightly to dissolve the residue. The walls of the beaker were then washed with distilled water. The volume was adjusted to 50ml. Iron was determined in the digested samples. Calculation: Concentration of iron (mg/L) = 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑥 𝐴𝑏𝑠𝑜𝑟𝑏𝑎𝑛𝑐𝑒 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 𝐴𝑏𝑠𝑜𝑟𝑏𝑎𝑛𝑐𝑒 𝑜𝑓 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 10 2.2.4 Reactive Nitrogen (NO3 - N) This method was carried out using the Colorimetric Cadmium Reduction Method. The pH was adjusted to acidic range by adding 2 drops of HCl to 25ml of filtered sample. A speck (or a drop) of NED reagent was added to the mixture. The mixture was allowed to stand for 5-10min., before being determined for NO2 at 520nm, using a calorimeter or at 543nm using HACH DR 2010 colorimeter. The difference between this result and that from NO2 (without reduction) indicated the concentration of NO3. The calorimeter simply displayed the result of NO3, having performed the computation. 2.3 Collection of Samples. Collection of water and phytoplankton samples for analyses were carried out between 9:00hrs and 12:30hrs monthly for six months (December, 2012- May, 2013). Water samples were collected 20cm below the surface water with 250ml screw capped plastic bottles for physical and chemical analysis. Chlorophyll-a sample, DO and BOD samples were collected in three 250ml amber bottles. Phytoplankton samples were collected using plankton net of 55µm mesh size towed for 7mins at low speed (< 4 knots) and was preserved in 4% unbuffered formalin. For the epiphyton community, the attached algae of interest were collected along Iragbo area of Yewa lagoon. Water hyacinth was harvested monthly from the central part of the lagoon away from the water edges including the fringes of "acadja" (artificial vegetation for fishing). Healthy plants were carefully selected to ensure uniformity in size before putting each into plastic containers with 500ml of fresh water. The attached algae were removed mechanically by shaking vigorously in water as suggested by Forester and Schlichting (1965), and was preserved in a well 11 labelled plastic container and 4% formalin added as a preservative. Another 500ml container was filled with an unfixed sample for chlorophyll-a determination. 2.4. Chlorophyll-a Determination Chlorophyll-a was determined using method described by Holm-Harsen (1978). 250ml of water sample was filtered and the chlorophyll-a was extracted by methanol. The extraction was centrifuged at 320rpm for 10mins and absorbance was measured at different wave length, the chlorophyll-a concentration was measured using the formula below. Chlorophyll-a (µg/L) = (𝐴𝑏𝑠[66𝑠𝑛𝑚]−𝐴𝑏𝑠[750𝑛𝑚])𝑥 𝐴 𝑥 𝑉𝑚 𝑣𝑓 𝑥 𝐿 (1) Where; A = Absorbance coefficient of chlorophyll-a in methanol Vm= Volume of methanol used for extraction Vf = Volume of sample filtered L = Path length of cuvette. 2.5. Community Structure Analysis Community structure analysis were determined by four indices 2.5.1. Margelef index (d): This is a diversity of species richness, which does not take into account dominant diversity, but is largely dependent on the species richness, that is, the more the species present in a sample the greater the diversity [Margelef, 1957]. d= 𝑠−1 𝑙𝑜𝑔𝑒𝑁 (2) Where: d = Diversity Index S = Number of Species N = Number of Individuals log = Natural logarithm H= 𝑁𝑙𝑜𝑔𝑁−∑𝑓𝑖𝑙𝑜𝑔𝑓𝑖 𝑁 (3) 12 Where: H = Shannon-Wiener Information Index ∑= Summation fi = Observed proportion of individuals that belong to the ith species loge = Natural logarithm. 2.5.2. Species Equitability or Evenness (j) Jaccard. This is a measure of how evenly the individuals are distributed among the species present in a sample. It ranges between 0 and 1, the maximum value. One represents a situation where individuals are spread evenly among the species present [Jaccard, 1912]. It was calculated as follows: j= 𝐻 𝐻𝑚𝑎𝑥 or 𝐻 (4) 𝑙𝑜𝑔𝑠 Where: j = Equitability measure H = Shannon-Wiener Information Index S = Number of species in the sample. 2.5.3. Similarity /Dissimilarity Index (Bray Curtis 1957) In a similarity index, a value of 1 means that the two communities you are comparing share all their species, while a value of 0 means they share none. Whereas, in a dissimilarity index the interpretation is the opposite. The Similarity Index (BC) between two samples is given by the equation: S= 2𝐶 𝐴+𝐵 (5) Where: S= Similarity index C= Number of species common to both samples A= Number of species in sample A B= Number of species in sample B, Dissimilarity = 1- Similarity. 13 3. Results 3.1. Hydro Climate Properties Data on some hydroclimatic features of the sample site at Yewa Lagoon is presented in table 1. The highest surface water temperature (32.2°C) was recorded in February while the lowest (30.2°C) was recorded in December. Similarly, higher pH, conductivity, DO and transparency values were recorded in the dry months than in the wet months (Table 1). On the other hand, Total Dissolved Solids (TSS), nutrients and Biochemical Oxygen Demand (BOD) values were higher in the wet months than during the dry months. Table 1. Variations in some physical and chemical parameters in Iragbo part of Yewa Lagoon (December, 2012-May 2013). MONTHS PARAMETERS JAN. FEB. MAR. APR. MAY. 30.2 30.8 32.2 31.8 31.3 30.5 Transparency (cm) 37.5 48.5 35 34 30.3 28 Ph 8.0 7.6 8.2 7.5 7.3 7.0 Conductivity (µS/cm) 94.0 97.0 99.0 83.0 80.0 78.0 Rainfall (mm) 13.2 0.0 28.0 50.1 165.3 340.8 49.0 46.0 37.0 45.0 56.0 0.53 0.67 0.53 6.8 10.1 6.9 0.1 0.2 3.1 16.8 18.1 33.0 Surface Water temperature (ºC) Total Suspended Solids (mg/L) Reactive Phosphate (mg/L) Reactive Nitrate DEC. 14 68.0 (mg/L) Sulphate (mg/L) 0.01 0.02 ND 7.0 8.0 7.82 Iron (mg/L) 0.072 0.07 0.07 0.34 0.208 0.068 Silicate (mg/L) 0.003 0.004 ND 0.003 0.002 0.003 2.8 7.6 5.1 4.1 5.5 4.5 7 10 10 16 13 13 32 38 21 37 38 40 Dissolved Oxygen (mg/L) Biochemical Oxygen Demand (mg/L) Chemical Oxygen Demand (mg/L) Chlorophyll a (phytoplankton) Chlorophyll a (Epiphyton) 0.001 0.004 0.001 0.001 0.003 0.003 0.002 0.005 0.014 0.012 0.003 0.002 ND =Not Detected Higher sicche disc readings in the dry months coincided with periods of drop in TSS values. Phosphates-phosphorus recorded a progressive increase into the wet months (≥0.5; ≤ 10.1) and nitrate level increases steadily and were very high during the wet months. Silicate values rose steadily in December and January, but fluctuated slightly in other months. 15 Rainfall (mm) Chlorophyll-a (Water sample) (µg/L) Chlorophyll-a (Epiphyton) (µg/L) 400 0.007 350 300 0.005 250 0.004 200 0.003 Rainfall (mm) Chlorophyll a (phytoplankton)(µg/L)/ Chlorophyll a (epiphyton)(µg/L) 0.006 150 0.002 100 0.001 50 0 0 DEC JAN FEB MAR APR MAY Months Fig. 2: Monthly variation in chlorophyll a (phytoplankton), chlorophyll a (epiphyton) and Rainfall at the Iragbo part of Yewa Lagoon (Deccember, 2012May, 2013). 16 Chlorophyll-a (Water sample) (µg/L) Chlorophyll-a (Epiphyton) (µg/L) Silicate (mg/L) 0.0045 0.004 0.006 0.0035 0.005 0.003 0.004 0.0025 0.003 0.002 Silicate (mg/L) chlorophyll a (phytoplankton)/ Chlorophyll a (epiphyton) 0.007 0.0015 0.002 0.001 0.001 0.0005 0 0 DEC JAN FEB MAR APR MAY Months Fig. 3: Monthly variation in chlorophyll a (phytoplankton), chlorophyll a (epiphyton) and Silicate at the Iragbo part of Yewa Lagoon (Deccember, 2012- May, 2013). 17 Chlorophyll-a (Water sample) (µg/L) Chlorophyll-a (Epiphyton) (µg/L) Conductivity (µS/cm) 120 0.007 100 0.005 80 0.004 60 0.003 40 Conductivity(µS/cm) Chlorophyll a (phytoplankton) (µg/L)/ Chlorophyll a (epiphyton)(µg/L) 0.006 0.002 20 0.001 0 0 DEC JAN FEB MAR APR MAY Months Fig. 4: Monthly variation in chlorophyll a (phytoplankton), chlorophyll a (epiphyton) and Conductivity at the Iragbo part of Yewa Lagoon (Deccember, 2012May, 2013). 18 Rainfall (mm) Chlorophyll-a (Water sample) (µg/L) Chlorophyll-a (Epiphyton) (µg/L) 400 0.007 350 300 0.005 250 0.004 200 0.003 Rainfall (mm) Chlorophyll a (phytoplankton)(µg/L)/ Chlorophyll a (epiphyton)(µg/L) 0.006 150 0.002 100 0.001 50 0 0 DEC JAN FEB MAR APR MAY Months Fig. 21: Monthly variation in chlorophyll a (phytoplankton), chlorophyll a (epiphyton) and Rainfall at the Iragbo part of Yewa Lagoon (Deccember, 2012May, 2013). 19 Chlorophyll-a (Water sample) (µg/L) Chlorophyll-a (Epiphyton) (µg/L) Transparency (cm) 60.0 0.006 50.0 0.005 40.0 0.004 30.0 0.003 20.0 Transparency (cm) chlorophyll a (phytoplankton)/ Chlorophyll a (epiphyton) 0.007 0.002 10.0 0.001 0 0.0 DEC JAN FEB MAR APR MAY Months Fig. 15: Monthly variation in chlorophyll a (phytoplankton), chlorophyll a (epiphyton) and Transparency at the Iragbo part of Yewa Lagoon (Deccember, 2012- May, 2013). 20 Calcium (mg/L) pH Magnesium (mg/L) Potassium (mg/L) 16 0.12 Magnesium (mg/L)/Calcium (mg/L)/pH 14 0.1 12 Potassium (mg/L) 0.08 10 0.06 8 6 0.04 4 0.02 2 0 0 DEC JAN FEB MAR APR MAY Months Fig. 8: Monthly variation in levels of Calcium, pH, Magnesium and Potassium in the Iragbo part of Yewa Lagoon (December, 2012 – May, 2013). 21 3.2 Diatom Community The phytoplankton of the Iragbo part of Yewa Lagoon belonged to seven main divisions: Bacillariophyta (32%), Chlorophyta (13%), Cyanophyta (51%), Euglenophyta (2%), Crysophyta (0.2%), and Pyrophyta (1%). A total of 55 species belonging to 35 genera were observed. Throughout the sampling period, the highest (2450 individuals per ml) (53%) phytoplankton occurrence was recorded in January, the least (414 individuals per ml) (9%)) was recorded in May. Thirteen phytoplankton orders were also recorded throughout the sampling months, namely; Centrales, Pennales, Chlorococcales, Volvocales, Zygnematales (Conjugales), Ulotricales, Chroococcales, Hormogonales, Euglenales, Mischoccocales, Dinokontae, Gonyaulacales and Nocticulales. The highest individual species (biomass) was Oscillatoria sp. which indicated a bloom in January. It is represented in the table 1below. Table 2: Species Abundance of Phytoplankton Species that occurred from December 2012 to May, 2013 at the Iragbo part of Yewa Lagoon DEC. JAN. FEB. MAR. APR. MAY Division: BACILLARIOPHYTA (DIATOMACEAE) Class: BACILLARIOPHYCEAE Order I: CENTRALES Family: COSCINODISCACEAE 22 Aulacoseira granulata 5 50 95 80 75 90 5 20 60 55 95 65 - 5 70 55 85 65 - 5 - - - Bacteriosira fragilis - - 30 - 25 10 Coscinodiscus concinnus - - - 5 5 - 5 - - - - - 5 5 - - - - Coscinodiscus nitidus - - 15 10 - - Cyclotella comta - 5 10 15 10 - Cyclotella stelligera - - 5 - 5 10 Melosira islandica - - - 10 5 - - 5 - - - - 5 10 70 35 - 20 Ehrenberg Aulacoseira granulata var. angustissima (Ehr.) Ralfs Aulacoseira granulata var. angustissima f. spiralis Muller Aulacoseira italica var. subarctica O. Muller Coscinodiscus lineatus Ehrenberg Coscinodiscus marginatus Ehrenberg Stephanodiscus astraea Grunow Family: LEPTOCYLINDRACEAE Leptocylindrus daniscus Family: RHIZOSOLENIACEAE 23 Rhizoselenia stolterfothii 5 - - - - - Diatoma vulgaris 5 - - - - - Synedra acus - 15 - - - - 5 - - - - - 5 - - - - - - 5 25 20 - 10 - - 15 5 - 10 - 5 - - - - 5 5 - - - - Navicula elliptica 5 - - - - - Pinnularia major 5 - - - - - 5 - - - - - Order II: PENNALES Family: FRAGILARIACEAE Synedra ulna (Nitzsch) Ehrenberg Tabellaria flocculosa (Roth) Kutzing Thalassiothrix nitzschioides Grun. Thalassiothrix spattulata Family: GOMPHONEMACEAE Gomphonema parvulum var. lagenula Family: ACHNANTHACEAE Cocconeis placentula Family: NAVICULACEAE Stauroneis phoenicentron f. gracilis Family: NITZSCHIACEAE 24 Nitzschia longissima 5 - - 40 30 15 - 5 - - - - - - 45 10 15 30 Chlorella vulgaris 150 5 - - - - Oocystis lacustris - 5 - - - - 25 - - - - - - - 5 - 5 - - 5 25 - 10 15 - 5 - - - - - 5 - 10 15 5 - - 15 - 5 - Nitzschia tryblionella var. victoriae Division: CHLOROPHYTA Class: CHLOROPHYCEAE Order I: CHLOROCOCCALES Family: CHLOROCOCCACEAE Chlorella sp. Butcher Palmellococcus minutus Kutz. Tetraëdron regulare var.incus Family: HYDRODICTYACEAE Hydrodictyon reticulatum Pediastrum biradiatum Meyen Pediastrum clathratum (A. Brawn) Lengerth Pediastrum duplex Family: SCENEDESMACEAE 25 Actinastrum hantzchii - - - 10 15 5 - - 10 15 10 - Crucigena minima - 5 - - - - Tetrastrum sp. - - - 5 5 - Pandorina morum 5 - - - - - Volvox globator - - - - 5 - Closterium arcuarium 5 - - - - - Closterium arcutum 5 - - - - - 5 - 10 5 - 10 5 - - - - - - 10 35 15 - 10 Golenkinia radiata Chodat - - 10 5 - 5 Gonatozygon kinahanii 5 - - - - - Actinastrum hantzchii var. fluviatile Order II: VOLVOCALES Family: VOLVOCACEAE Order III: ZYGNEMATALES (CONJUGALES) Family: DESMIDIACEAE Closterium cornu var. javanicum Hyalotheca dissiliens Order IV: Ulotrichales Family: Ulotrichaceae Stichococcus bacillaris Family: MESOTAENIACEAE Family: 26 ZYGNEMATACEAE Spirogyra africana Fritsch 5 - - - - - Chroococcus disperses - 10 - - - - Chroococcus pallidus Nageli 5 - - - - - - 5 - - - - 175 375 - - - - - - 15 - 10 20 - - 25 15 5 10 Oscillatoria sp. - 1850 - - - - Oscillatoria tenius Agardh 5 - - - - - Cruda Division: CYANOPHYTA Order I: CHROOCOCCALES Family: CHROOCOCCACEAE Microcystis aeruginosa f. flos-aquae Microcystis aeruginosa Kutzing Order II: NOSTOCALES Family: NOSTOCACEAE Anabaena spiroides Klebahn var. minima Nygaard Anabaena spiroides Klebahn var. tumida Nygaard Order III: OSCILLATORIALES Family: OSCILLATORIACEAE 27 Division: EUGLENOPHYTA Order: EUGLENALES Family: EUGLENACEAE Euglena ehrenbergii - - 15 10 5 - Phacus caudatus 5 - - - - - Phacus longicauda 5 - - - - - - - 15 10 5 - 5 - - - - - Phacus sp. 5 - - - - - Trachelomonas conica 5 5 - - - - Trachelomonas nigerica - 5 - - - - Trachelomonas robusta - 5 - - - - Trachelomonas volvocina 5 - - - - - Trachelomonas volvocinopsis 5 5 - - - - Centritractus belonophorus - 5 - - - - Ophiocytium capitatum Wolle 5 - - - - - Tetrasporopsis perforate 5 - - - - - Phacus longicauda var. rotundus Phacus oblonga var. planctonica Division: CHRYSOPHYTA Order: MISCHOCCOCALES Family: SCIADACEAE Division: PYRRHOPHYTA Class: DINOPHYCEAE 28 Order: DINOKONTAE Family: PERIDINIACEAE Peridinium cinctum 5 - - - - - - 5 - - - - 5 - - - - - Noctiluca scintillans 5 - - - - - Total species diversity (S) 38 30 23 22 23 19 Total abundance (N) 525 2450 630 440 460 415 Family: GYMNODINIACEAE Gymnodinium excavatum Order: GONYAULACALES Family: GONIODOMATACEAE Alexandrium catenella ORDER: NOCTILUCALES Family: NOCTILUCACEAE The epiphyton of the Iragbo part of Yewa Lagoon belonged to four main divisions: Bacillariophyta (87%), Chlorophyta (4%), Cyanophyta (8%), and Euglenophyta (3%). A total of 39 species belonging to 26 genera (535 individuals per ml) (35%) epiphyton occurrence was recorded in February, the least (265 individuals per ml (17%)) was recorded in April. Seven epiphyton orders were recorded throughout the sampling months, namely: Centrales, Pennales, Tetrasporales, Dismidiales, Volvocales, Hormogonales and Euglenales. The highest individual species of the 29 epiphyton algae is Aulacoseira granulate Var. angustissima. It is represented by table 2 below. Table 3: Species Abundance of Epiphyton Species that occurred from February to May, 2013 at the Iragbo part of Yewa Lagoon EPIPHYTON TAXA DEC. JAN. FEB. MAR. APR. MAY Division: BACILLARIOPHYTA Class: BACILLARIOPHYCEAE Order: CENTRALES Family: COSCINODISCACAEA Aulacoseira granulata var. 185 180 200 175 80 95 190 160 185 145 110 75 50 75 85 70 45 55 55 50 40 25 20 30 Coscinodiscus granii 10 - 5 - - 5 Coscinodiscus nitidus 15 20 15 10 - 5 Cyclotella comta Kutzing 10 15 15 10 5 - augustissima Aulacoseira granulata var. muzzanensis Aulacoseira italica var. supsp. Subarctica Aulacoseira granulata Ehrenberg Order: PENNALES 30 Family: FRAGILARIACAEA Diatoma elongatum 5 - - - 10 15 Fragilaria virescens - - 10 15 - - Gyrosigma scalproides 10 - 5 5 - - Pediastrum chlathratum - 10 10 - 10 5 10 15 20 10 - 5 Surirella ovate 15 20 15 - 5 - Surirella robusta 15 10 15 5 - 10 - 15 - 15 - 10 15 10 25 40 15 5 Synedra acus 15 10 30 25 5 20 Leptocylindrus daniscus 25 - 45 20 - 10 Leptocylindrus sp. 10 20 30 15 20 - Dentonula schroderi 20 30 20 10 15 5 20 15 25 10 15 5 20 15 20 25 - 15 10 10 30 20 15 20 Melosira islandica 55 70 45 75 50 35 Pinnularia divergens 10 - 10 25 - 15 - 15 10 - 10 5 Pediastrum duplex var. subgranulatum Surirella robusta var. armata Surirella robusta var. splendid Stephanodiscus astraea Grunow Stephanodiscus minutulus Tabellaria fenestrata var.intermediata Gomphonema dubravicense 31 Division: CHLOROPHYTA Class: CHLOROPHYCEAE Order: TETRASPORALES Family: TETRASPORACAEA Asterococcus superbus 10 20 25 - - 10 Desmidium sp. 5 - 5 5 - - Desmidium swartzii 20 10 - 5 10 5 - 5 5 - 15 5 Pandorina morum - 10 - - 5 - Volvox globator 5 - 5 - - 5 Order: DESMIDIALES Family: DESMIDIACAEA Hyalotheca dissiliens Order: VOLVOCALES Family: VOLVOCACAEA Division: CYANOPHYTA Class: CYANOPHYCEAE Order: NOSTOCALES Family: NOSTOCACAEA 32 Anabaena affinis 20 20 30 20 5 10 10 20 25 35 15 5 5 - - 5 - - - 5 - 5 - - Euglena ehrenberghii 10 - 15 - 10 5 Phacus longicauda 10 5 - 10 - 15 - 10 - - 5 5 Total species diversity (S) 31 29 26 23 20 25 Total abundance (N) 895 885 880 705 465 455 Anabaena spiroides var.tumida Calothrix pariatina Tetraëdron regulare var.incus Division: EUPHYTA Class: EUPHYCEAE Order: EUGLENALES Family: EUGLENACAEA Trachelomonas hispida 33 115, 2% 20, 1% Bacillariophyta 15, 0% Chlorophyta Cyanophyta Euphyta Chrysophyta Pyrhophyta 1565, 32% 2535, 52% 635, 13% Fig. 4: Relative abundance of phytoplankton divisions that occurred at the Iragbo part of Yewa Lagoon from December, 2012 to May, 2013. 34 105, 4% 195, 7% 65, 2% Bacillariophyta Chlorophyta Cyanophyta Euphyta 2525, 87% Fig. 5: Relative abundance of Epiphyton divisions that occurred at the Iragbo part of Yewa Lagoon from December, 2012 to May, 2013. 35 Phyto-taxa Epi-Taxa 40 35 30 25 20 15 10 Variation in Taxa 5 0 Dec. Epi-Taxa Jan. Feb. March Phyto-taxa April May Months Fig. 6 Variations in taxa for Phytoplankton and Epiphyton communities from Dec. 2012- May 2013 at Irabgo part of Yewa Lagoon. 36 3.3 Community Structure Indices The indices of species richness (d), Shannon-Wiener diversity (Hs), Evenness or Equitibility (J), Bray Curtis similarity/dissimilarity index (BC) were calculated to estimated the monthly variation in phytoplankton and epiphyton diversity. Table 4: Variations in species richness (d), Shannon-Wiener index(H), Bray Curtis index(BC) and Equitibility index(J) in phytoplankton community across months Iragbo part Yewa Lagoon. MONTHS INDICES DEC. JAN. FEB. MAR. APR. MAY Shannon-Wiener Index (Hs) 1.05 0.43 1.22 1.18 1.10 1.09 Margalef Index (d) 5.91 3.72 3.41 3.45 3.59 2.99 Bray Cutis Index 0.45 0.58 0.49 0.55 0.60 0.54 Equitability Index (j) 0.67 0.29 0.90 0.88 0.81 0.85 37 Table 5: Variations in species richness (d), Shannon-Wiener index(H), Bray Curtis index(BC) and Equitibility index(J) in epiphyton community across months Iragbo part Yewa Lagoon. MONTHS INDICES Shannon-Wiener Index DEC. JAN. FEB. MAR. APR. MAY 1.40 1.36 1.34 1.25 1.21 1.30 Margalef’s Index (d) 4.02 4.00 3.98 3.62 3.41 4.27 Bray Cutis Index 0.49 0.50 0.52 0.48 0.51 0.47 Equitability Index (j) 0.91 0.94 0.95 0.92 0.93 0.93 (Hs) All through the sampling period, both species richness (d) and Shannon-Wiener index (H) decreased as wet months approached in both phytoplankton and epiphyton communities. Generally, diversity was low between April and May in both communities, a pattern possibly related to low light penetration caused by high turbidity. 38 4. Discussion The physical and chemical changes observed in the Lagoon may have been as a result of hydroclimatic changes linked to the seasons. For instance, the dry months concentrated between December and April was accompanied by higher conductivity, higher temperature and higher transparency. On the other hand, changes may be linked to impact of leacheates into the Lagoon from Yewa River, associated creeks and wetlands in the wet months. Similar observations have been reported by Nwankwo (1993,1996) in the Lagos Lagoon. The higher surface water temperature observed in the dry months maybe due to less cloud cover and high insulation. Nwankwo et al. (2008) made similar observations. The decrease in total dissolved solids, total suspended solids and turbidity during the dry months may be attributed to decrease in the influx of flood waters from the rivers, creeks and wetlands. This observation supports the view of Egborge (1988) in Yewa Lagoon. Conductivity was relatively stable all through the sampling months possibly due to lack of any intrusion of sea water. Lagoons of South West Nigeria are known to be of two types, some like the Lagos and Iyagbe Lagoons directly influenced by tidal sea water are said to be physical while others like Epe, Kuramo, Lekki, Yewa, Badagry are said to be biologically controlled Onyenekan (1987). Though the concentration of oil pollution here is very minimal there are still some traces of effects that it has especially on phytoplankton biomass. The effect of this oil pollution of the coastal waters is more noticeable during rainy season when spilled products are washed from drains and drainage channels into the water bodies (Odiete, 1999) The pH range of between 6.95-8.16 maybe due to the influence of high carbonate leacheates draining part of Ewekoro cement factory in Ogun state into the Yewa river that empties into the Yewa Lagoon. The buffering effect of carbonate in coastal 39 waters of south western Nigeria is well known (Nwankwo et al 2008). The higher COD values throughout the sampling months and low BOD could be an indication of some levels of pollution. The BOD values recorded for the Lagoon during the sampling period lie below the acceptable limits set by WHO for international water quality standard in coastal waters (15.9-37.5mg/L) with warning levels from (18.934.5mg/L). The Lagoon could be said to be slightly organically polluted. According to Hynes (1960) working in a river, biochmical oxygen demand values less than 2.0 mg/L indicate clean water, 2.0 to 4.0mg/L indicates moderate pollution while above 8.0 mg/L indicates severe stress. However, Yewa Lagoon is not a river and Hynes criterium may not be relevant. Since Yewa Lagoon is fresh and lotic and since there is no direct connection to the sea, it is still possible that standards higher than 8.0mg/L but lower than 16.5mg/L may point towards pollution stress. The rising values of micro nutrients between February and April maybe due to reduction of water inflow from the creeks and rivers, it may also be as a result of an increase in water temperature and possible increase in bacterial oxidation. Similar observations were made by Thomas (1966) in a small man-made Lake in Ghana. Reactive silicate all through the sampling months remained comparatively stable possibly due to non influence from sea water, although reactive silicate values was less in months where there is high diatom biomass, this may be due to the fact that diatoms use reactive silicate to build its (frustules). The higher values of nitratenitrogen recorded in the study may account for the relatively higher phytoplankton abundance. Similar report was found in Nwankwo et al (2013) working in temporal variations in water chemistry and chlorophyll-a at Tomaro creek. The impacts of Copper, Lead and Zinc on the growth of both phytoplankton and epiphyton algae were not specifically felt, the reason maybe that their presence did not exceed 0.62mg/L in all the sampling months. Bilgrami and Kumar (1997), 40 studying the effect of Copper, Lead and Zinc on phytoplankton growth found out that at concentrations 0.1mg/L, these metals were not toxic. However, at concentrations 10.0mg/L, the growth of phytoplankton was inhibited, Cu was the most toxic, followed by Pb and Zn. The rising values of Iron between March and April showed an increase in plankton biomas, this may confirm the fact that algae especially diatoms require Iron for growth. Similar observations were also made by Bilgrami and Kumar (1997). The abundance of aquatic machrophytes like Ipomoea aquatic Forsk, Eichhornia crassipis and Pistia stratiotes by the Yewa Lagoon side as well as the water surface is an indication of the eutrophic level of the Lagoon. Nwankwo and Akinsoji (1988) made similar observations while working on benthic algal community on water hyacinth in south western Nigeria. With the nutrient loads mainly from domestic and industrial which drains into the Lagoon through creeks, rivers and wetlands, it would be expected that the algae present would be pollution-tolerant and hence indicator species. Diatoms dominated the water hyacinth epiphyton community possibly because of their ability to develop rapidly on newly submerged surfaces or due to their ability to successfully adapt to fresh water habitat. According to Shevchenco (2000), it has been found that the most favorable condition for epiphyton development are formed on submerged plants, where the number of algal species and their intraspecific taxa is higher than that on plants of other ecological groups. Nwankwo and Onitiri (1992), while working on periphyton community on submerged aquatic macrophytes (Horn-wort and Bladder-wort) in Epe Lagoon reported the dominance of diatoms. Chlorophyll-a (phytoplankton) abundance showed positive correlation with COD and DO although not significant while chlorophyll-a (epiphyton) showed significant positive relationship with P,N and S. The phytoplankton community has a higher 41 species richness than the epiphyton but the epiphyton has a better spread across the months. A higher population of central diatoms are found in the phytoplankton community whereas the epiphyton community has a higher population of pinnate diatoms, this maybe as a result of the ability of the pinnate diatoms to attach easily to aquatic machrophytes. The similarity between phytoplankton and epiphyton is 0.49. this may mean that about half of the species found in the phytoplankton community may also be found in the epiphyton community. The dissimilarity index also indicates that half of the species in the two communities may not be found in both. Since many of the species observed were found in almost all the months regardless of the water status, their presence may not make them satisfactory indicators of any particular pollution. However, it may be possible to relate the abundance of some species with changes in water quality. For instance the presence of species like Gomphonema parvulum (diatom), Synedra acus (diatom), trachelomonas hispida (Euglenoid), Phacus longicauda (Euglenoid), surivella ovata (Diatom), Pinnularia major(Diatom),Chlorella vulgaris(green algae), Actinastrum hintzschii(green algae), Pandorina morum(green algae) are known to be indicators of organic pollution (Butcher 1947, Palmer, 1969), this may be a pointer that the Iragbo part of Yewa` Lagoon is gradually being enriched probably due to several tributaries connected to it. Nwankwo and Amuda (1993), while working on periphytic diatom on three floating aquatic macrophytes in a polluted south-west Nigerian creek also made similar observations. Some algal species like Actinastrum hantzzchii(Green algae), Pediastrum clathratum(Green algae), Pinnularia divergens( Diatom), Euglena ehrenbergii(Euglena) and Golenkinia radiate (Green algae) are threatened by the pollution status of the Lagoon. 42 5.0 Conclusion Both phytoplankton and epiphyton biomass were higher in the dry months due to relative stability of the lagoon water and higher light penetration, this may imply that during wet months the lagoon receives substantial amount of inland waters through its many tributaries, resulting to light penetration, high turbidity and high TSS thereby resulting to paucity of diatoms in the lagoon. Naturally the pH of fresh water like the Yewa Lagoon is well known to be more acidic but in this work it is seen to be more alkaline due to lechaets from Ewekoro cement factory. Almost half of the species identified during the investigation belong to both plankton communities. Phytoplankton algal species that could be used as indicator of organic pollution identified include: Diatoms- Gomphonema parvulum, Synedra acus, Pinnularia major. Green algae- Chlorella vulgaris, Actinastrum hantzschii. Euglenoids- Phacus longicauda while Epiphyton species that could be used as indicator of organic pollution identified include: Diatoms- Synedra acus, surivella ovata, Green algaePandorina morum, Euglenoids- Trachelomonas hispida, Phacus longicauda. Acknowledgement The authors are grateful to the staff of Marine Biology Laboratory, University of Lagos for field assistance and sample analysis. Special thanks go to Prof. Nwankwo, D. I. for this expertise advice and meticulous assessment of the work. 43 References Adesalu, T. A. and Nwankwo, D. I. (2005). Studies on the phytoplanktonof Olero Creek and parts of Benin River, Nigeria. The Ecologia. 3(2): 21-30. APHA (1998). Standard Methods for the Examination Water and Sewage, 16th ed. 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