ABSTRACT

The reservoir of National Root Crops Research Institute (NRCRI), Umudike was examined in order to establish plankton occurrence and water quality over a period of time. Plankton was studied for eight (8) months (June 2011 — January, 2012). Five (5) sampling sites were located on the reservoir. Physico-chemical parameters investigated include: temperature which ranged from 24.60 — 31.20 ± 1.91 °C, depth 42.00-60.70 + 5.73 cm, transparency 17.40-32.60 + 5.53 cm. pH 5.00 —6.80 ± 0.67, dissolved oxygen 3.72— 12.03 ± 2.57 mg/I, biochemical oxygen demand 0.94-5.71 + 1.55 mg/l, total dissolved solids 0.01 —98.16 + 42.16 mg/I, total alkalinity 5.00-8.00 ± 0.96 ppm and total hardness 17.60-28.00 + 3.80 mg/I. Water sample was collected 10 cm depth of the reservoir with I-litre plastic bottles, fixed with Lugol's solution and taken to the laboratory for plankton identification. Phytoplankton identified from the reservoir included Spirogyra (25.69%), Euglena (21 .02°A), Micrasierias (15.33%), Zygnema (12.99%), Spirit//na (11.83%) and Cryplonionas (13.14%). The phytoplankton occurrence followed the order: Spirogyra > Euglena > il'Iiciasierias > Crvptoinonas > Zygnenia and Spirulina. Zooplankton identified from the reservoir included Daphnia (37.24%), Brachionus (12.30%), Cpris (9.66%), Mesocyclops (15.63%), Cyclops (11.62%) and Mo/nc, (13.56%). The zooplankton abundance followed the order Daphnia > Mesocyclops > Moina > Brachiornes > Cyclops > Cypris. The heavy occurrence of plankton in the reservoir was due to the favourable conditions maintained by the physicochemical parameters investigated. The plankton community composition of the reservoir also showed the reservoir to be productive and would support diverse species and population of fishes. It is therefore recommended that proper and routine sampling should be carried out in order to maintain the abundance of plankton for sustainable fisheries and agriculture.