Limnological studies of two contrasting but closely linked springs in Nigeria,West Africa

ABSTRACT

An account is presented of the chemistry and algal flora of two streams in Ekiti State, Nigeria. The two streams, one of which is much warmer than the other, are separate upstream but subsequently merge. A comparison of the springs revealed that while they differed markedly in temperature, colour, turbidity, conductivity, solids, total alkalinity, total hardness, Ca, SiO₃, SO₄, Mg, Cl^- and dissolved oxygen, they showed some similarities in pH, Fe, Na, K, PO₄ and NO₃. In the cold spring, while total alkalinity, conductivity and silicate increased in the wet season, total hardness decreased slightly and other variables exhibited fluctuations with season. For the warm spring, except for increased total alkalinity and total hardness, dissolved oxygen and pH decreased in the wet season. However, most parameters of the warm spring were unaffected by season. Floristically, the springs were rich in species with a total of 84 taxa: 56 in the warm spring, 33 in the cold spring, 44 at the confluence and 40 beyond the confluence. The warm spring was dominated mainly by blue-green algae such as Lyngbya birgei, Synechococcus aequalis and Oscillatoria spp.; the cold spring was dominated by Rhizoclonium hieroglyphicum and Navicula spp. The confluence was dominated by Terpsinoe musica, R. hieroglyphicum and Lyngbya birgei, while the site downstream of the confluence was dominated entirely by R. hieroglyphicum. In most cases, the confluence and downstream area beyond the confluence of the springs exhibited intermediate characteristics between the two springs. This study is a contribution to the dearth of information on streams in West Africa.