Abstract
Waterfalls gives the impression of a lifeless zone because researchers have historically focused on the hydrology, ecotourism and geological features. Effective management will require an understanding of changes in species composition and distribution of macro-biota. Monthly samples were taken in wet and dry seasons, over two year period in three regions along the 6817.7m length of the Agbokum waterfalls. Macro-biota exhibited distinct pattern in respect of seasonal and spatial changes. Trachelomonas volzii, the most abundant phytoplankton species reduced from 686 in the dry season to 143 in the wet, and from 455 downstream to 91, midstream (waterfalls region). Zooplankton species Calanus finmarchicus decreased from 511 during dry season to 36 in the wet and from 334 downstream to7, midstream. 71.7 percent of the total macro-invertebrates were recorded from downstream reaches while only 6.3 percent were contributed by midstream. Among the three dominant fish species Tilapia zillii, Clarias gariepinus and Labeo coubie, constituting 45.5% of total catch, two benthic fishes (L. coubie and C. gariepinus) showed inverse distributional patterns. Clariid fish (C. gariepinus) was most abundant downstream and least represented upstream. Cyprinid (L.coubie), on the other hand, dominated the upstream reaches and scarce downstream. Percentage cover of marginal vegetation by Bambusasp, Symphonia and Elaeis guineesis displayed progressive increase from upstream reaching a maximum of 38.5 mean percent cover in the relatively undisturbed downstream. In contrast, Raphia vinifera, Havea brasiliensis, Grewia sp and Cocos nucifera shrank in size from 34% to 8% at the midstream stretches of the river while only nymphia- rich vegetation becomes more frequent in the middle reaches. Nymphia has become a biological invader and has exhibited a full range of impact and abundance in this disturbed midstream reaches. The disturbance regimes of the midstream reaches of Agbokum waterfalls combined with its very low faunal and floral diversity has made the environment unstable therefore susceptible to the invasion of disturbance tolerant biota.
Highlights
Waterfalls, most of which are formed from stream or river which cascade from a high elevation over a cliff or rock, had very little attention from researchers the world over
Raphia vinifera, Havea brasiliensis, Grewia sp and Cocos nucifera shrank in size from 34% to 8% at the midstream stretches of the river while only nymphia- rich vegetation becomes more frequent in the middle reaches
This study presents an analysis of the occurrence, distribution and dynamics in the fauna and flora resources of Agbokim waterfalls to reduce our over- dependence on es
Summary
Waterfalls, most of which are formed from stream or river which cascade from a high elevation over a cliff or rock, had very little attention from researchers the world over. In Africa, the reason being that, waterfalls were named after deities and were used as places of traditional and ancestral worships. The intensity of waterfalls andpressure generated from it due to gravity has given the im- pression of a lifeless zone[1]. Knowledge of waterfalls systems in Africa are limited to hydrology and geological features[2,3], as natural monuments for revenue generation, because of their ecotourism potentials[4] and as source for drinking, irrigation and other domestic purposes. It is possible that the biodiversity of Cross river fishes is much higher than reported[5, 6] and could yield records of undiscovered and un-described species if the Agbokim Waterfalls and other water bodies such as Crater lakes, flood plains, lakes and mountain streams which link up with the Cross River, are investigated
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