Ife Journal of Science vol. 13, no.1 (2011) 93 CHECKLIST OF THE AQUATIC MACROPHYTES OF JEBBA LAKE, NIGERIA Adesina, G.O.1*, Akinyemiju, O.A.2 And Muoghalu, J.I.3 1. Department of Agronomy, Ladoke Akintola University, Ogbomoso, 2. Professor, Department of Plant Science, Obafemi Awolowo University, Ile Ife, Osun State. 3. Professor, Department of Botany, Obafemi Awolowo University, Ile Ife, Osun State. (Received: October, 2010; Accepted: May, 2011) ABSTRACT The occurrence and diversity of aquatic macrophytes on Jebba Lake were documented during the rainy and dry seasons from 1999 to 2001. Analyses showed that the species diversity increased by 20, from 26 in 1988 to 46 in 2001. The number of species encountered during the dry and wet seasons during the period of sampling between 1999 and 2001 differed only marginally. The emergent macrophytes formed 93.3% of the total macrophyte population with the dominant species irrespective of season being Vossia cuspidata Griff., Eichhornia crassipes (Mart.) Solms, Mimosa pigra Linn, Vetiveira nigritana (Benth.) Stapf, and Mariscus longibracteatus Cherm., Sesbania dalzielii. E. Philip & Hutch. which is an annual, was found to be dominant only during the rainy period. Key words: Aquatic Macrophytes, Diversity, Abundance, Vossia cuspidata, Eichhornia crassipes, Sesbania dalzielii. INTRODUCTION MATERIALS AND METHODS Aquatic plant infestation of water bodies Study Area. is a worldwide problem. Many aquatic plants The study was carried out on Jebba Lake, grow as weeds in paddy crops, drainage systems which lies between 9o 10' and 9 o 55'N and 4 o 30' and waterways (Akobundu, 1987). Weeds of and 4 o 50'E. The Lake, which was impounded in paddy crops (Akobundu, 1987) and aquatic 1983, has a drainage basin extending 100 km from macrophytes occurring in Lake Kainji, Nigeria Fakun, immediately below Kainji Reservoir, to the (Obot and Ayeni 1987) have been reported. Jebba dam site. The hydrological pattern of Jebba Massive occurrence of water hyacinth on Lake Lake, which is closely linked with that of the Kainji (Akinyemiju, 1995), Itoikin irrigation Kainji Lake, experiences two annual floods. channel, Lagos state (Akinyemiju, 1989) and Between June and July at the onset of the annual Kofawei creek, Ondo State (Akinyemiju and rainy season, water drawn from rivers and streams Imevbore, 1990) have also been reported. Jebba within the catchment area is discharged into the Lake, impounded in 1983 for hydroelectric power Lake (Obot and Mbagwu, 1988). The second generation and flood control in Nigeria flood originates from areas around the source of (Anonymous, 1983) is currently threatened by River Niger in Guinea, comes in as black flood aquatic macrophytic infestation. into Kainji Lake and subsequently enters Jebba Water hyacinth invasion of water body is a lake as excess discharges from the lake (Obot, biological stressor which endanger other aquatic 1984). The black flood which reaches Kainji flora and fauna (Akinyemiju, 1987; Olaleye and Lake in early November finds its way into the Akinyemiju, 1999) and impair physico-chemical Jebba Lake by the end of November or early quality of water bodies (Olaleye, 2002). A market December. Six major tributaries which empty into survey around fishing communities in Nigeria Jebba Lake: the Oli, Wuruma, Moshi and Awuru revealed a sharp decline in the tonnage of fishes Rivers on the western side and the Kontangora of economic importance in aquatic vegetation and Eku Rivers on the Eastern side (Figure 1). infested areas (Alimi and Akinyemiju, 1991). This study was carried out to document the changes in Methods the aquatic macrophytic composition of Jebba An initial field reconnaissance survey was Lake which is one of the biggest artificial lakes in carried out along both banks of Jebba Lake Nigeria. between June and July 1999. Sampling was done at approximately 3 km interval such that 68 94 Adesina et al.: Checklist of the Aquatic Macrophytes of Jebba Lake Figure 1: Map of Jebba, Lake Nigeria (Source: Natioanl Institute for Freshwater Fisheries Research, New Bussa, Niger State, Nigeria) Adesina et al.: Checklist of the Aquatic Macrophytes of Jebba Lake 95 designated stations were sampled along the rainy season is shown in Figure 2. The result shoreline and the open water. Based on the showed that the dominant species during the rainy preliminary results, a systematic-sampling season include Vossia cuspidata, Sesbania dalzielii, technique was then adopted to map out sampling Eichhornia crassipes and Mimosa pigra with 10.7%, points on the lake during the field survey between 10.3%, 8.7%, and 8.2% occurrence respectively. August 1999 and August 2001. With the aid of Other less prominent species arranged in the line transects, 20 sampling points were then descending order of occurrence were Mariscus established at 10 km intervals with the aid of a longbracteatus, Ipomoea aquatica, Vetiveria nigritana and GPS, on the eastern and western sides of the lake Polygonum lanigerium. Comparatively, the following (Figure 1). Sampling was carried out over two were prominent species during the dry period: years (1999-2001) during the rainy season, which Vossia cuspidata, Eichhornia crassipes, Echinochloa spp. corresponds to the period of drawdown or lower and Mimosa pigra with 10.3%, 10.3%, 9.1% and water regime over the lake, and during the dry 8.3% occurrence respectively. Analysis further season, which corresponded to the high water showed that irrespective of the season of regime (when the lake holds the highest volume of sampling, the dominant aquatic macrophytic water). species were Vossia cuspidata, Eichhornia crassipes, Sesbania dalzielii, Mariscus longibracteatus, Echinochloa A 5 x 5 m sampling plot which was established at spp., Mimosa pigra, Polygonum lanigerium, Ipomoea spp. each location, extends from the open water (with a and Vetiveria nigritana. Comparative analysis also depth of 5-10 m) up to the shoreline. Across each showed that the low number of macrophytes sampling plot, a perpendicular line transect was species on the Jebba Lake between 1986 and 1988 laid. A 1 m2 quadrat was then laid at 1 m interval to has increased from 18 species (in 1986) to 30 facilitate a complete littoral and open water plant species (in 1988) and to 46 species between 1999 species data collection. Herbaceous and woody and 2001. Analysis also showed that twenty new species within each transect were also identified to species have established in the lake while sixteen species level according to Hutchinson and Dalziel species were no longer present in the lake 13 years (1954-1972). The encountered plant species after (Table 2). composition was then compared with earlier documented aquatic plant species composition on DISCUSSION the Jebba Lake (Obot and Mbagwu, 1986; 1988). Comparative studies showed that the macrophytic species composition of the Jebba RESULTS Lake was similar to those of plants encountered A total of 46 plant species belonging to 22 on the Kainji Lake. This was probably because families were recorded (Table 1) during the period Kainji Lake supplies a lot of plant propagules to of study. The floristic composition consist of 21 Jebba Lake (Obot and Mbagwu, 1988). However, perennial plants species, 18 annual species while factors responsible for the development of many only three species were either annual or perennial, of new species encountered on the Jebba Lake depending on the prevailing environmental was probably reduction in the hydraulic water conditions. A total of 45 aquatic species were turnover in Jebba Lake which allows for extended observed during the rainy season, while 47 species water retention period, consequently allowing for were observed during the dry period (Table 1). On new plant development. the basis of life forms, macrophytic species The effect of human impacts in terms of accounted for about 4.4% of the total species non-fishing activities like crop farming and animal composition, submerged aquatic species husbandry in the riparian communities indirectly accounted for 2.2% while emergent species with enrich the lake through application of inorganic 93.30% of the total number of species and organic fertilizers. Both Jebba and Kainji Lake encountered across the seasons. Ludwigia catchment basins service several thousand hyssopifolia was encountered only during the dry livestock especially cattle, sheep and goats as season. grazing and water holes (Adesina et al., 2004). Comparison of the aquatic macrophytic These animals through grazing of diverse species found on the Jebba Lake during the 1986, vegetation deposit viable seeds in addition which 1988 and 2001 samplings is shown in Table 2. The end up in the nearest riparian waterbody and later occurrence of the macrophytic species during the germinate thereby adding to the species diversity % Occurrence 1 1 0 2 0 2 4 6 8 Vossia cuspidata F Echinochloa spp i g u r e 2 Polygonum lanigarium : P e r c Ipomoea aquatica e n t a g e Maricus lonbracteatus O c c u Andropogon gayanus r r e n c e Ludwigia hypsopfolia o f A q u Pennisetum polystachion a t i c M Ludwigia decurrens a c r o p 1 Alternanthera sessilis h 9 y 9 t e 9 S - p S Sporobolus pyramidalis 2 p e 0 e c c 0 i i 1 e e s s . Urena lobata o n J e b Sphenoclea zeylanica b a L a k Sesbania dalzielii e D u r i Rottboellia cochinchinensis n g t h e Panicum repens D r y a n Loudetia arundinacea d R a i n Hyperrhenia rufa y S e R D a Heterotis rotundifolia s a r o y i n n S y s e b S a e Commelina benghalensis e s t o a w s n o e e n n Senna obtusfolia Lemna aequinoctialis Adesina et al.: al.: et Adesina klist of klist Chec the Aquatic Macroph Aquatic the ytes of ytes ebba Lak ebba J e 96 Adesina et al.: Checklist of the Aquatic Macrophytes of Jebba Lake 97 of vegetation within the lake catchment.