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The Distribution and Seasonality of Benthic Macro-Invertebrates in Sombreiro River, Niger Delta, Nigeria
並列摘要
The distribution and seasonality of benthic macroinvertebrates in Sombreiro River was studied for a perion of two years (August, 2007 - July, 2009). Of the twenty-eight (28) species observed in the area, all the species of the class Oligochaeta did not occur in station1 (Degema) but occurred in the remaining three stations 2 (Ogbele), 3 (Ihuaba) and 4 (Odiemudie). The species recorded were relatively abundant in stations 2, 3 and 4. In station 2 (Ogbele) Paranais sp. (Naididae) was the highest 40.5%; ＂Styleria lacustris＂ (Naididae) 40.6% in station 3 and ＂Uncinais uncinata＂ (Naididae) in station 4.All the species of the class Polychaeta occurred only in station 1 (Degema) but did not occur in the remaining three stations. In terms of percentage all species had 100% but numerically ＂Nephthys hombergi＂ (257) was the highest followed by ＂Notomastus latericeus＂ (124).The only species of the family chironomidae (Chironomus sp.) did not occur in station 1 but occurred in the remaining three stations. The highest percentage occurrence (49.1%) was recorded at station 3 (Ihuaba). Tympanotonus fuscatus and Pachymelania fusca (Potomidae) occurred only in station1 (Degema). Tellina nymphalis, Loripes sp. and Tegalus andersoni occurred only in station 1 (Degema). Station 1 (Degema) had twenty (20) species while stations 2, 3, and 4 had 8species each. The result showed that Ophidonais sapentina had the highest mean value 20.917±11.147, (August 2007-July 2008); 20.500±7.891 (August 2008-July 2009). This was followed by ＂Eiseniella tetrahidra＂ 17.917±9.179 (August 2007-July 2008); 17.417±7.476, (August 2008 - July 2009) and ＂Uncinais uncinata＂ 14.667±6.443 (August 2007-July 2008), 14.417±5.017 (August 2008-July 2009). The least was ＂Tellina nymphalis＂ 0.583±1.505 (August 2007-July 2008); 0.333±0.651, (August 2008-July 2009). There was no significant variation in the mean values of the two years studied 5.900±0.4168 (August 2007-July 2008). 5.717±0.3704 (August 2008-July 2009). Seasonal variations occurred in the abundance of Dero sp. (11.00±5.20 wet, 17.71±3.72 dry), Stylera lacustris (11.82±5.15 wet, 18.50±10.57 dry) and Eiseniella tetrahidra (18.76±9.16 wet, 15.00±4.69 dry). The other species did not show significant variation. However, there was significant variation between the mean of the wet season and that of the dry season 5.32±0.30 wet and 6.99±0.58, respectively. The result showed that Ophidonais sapentina had the highest mean value 20.917±11.147, (August 2007-July 2008); 20.500±7.891 (August 2008-July 2009). This was followed by Eiseniella tetrahidra 17.917±9.179 (August 2007-July 2008); 17.417±7.476, (August 2008-uly 2009) and Uncinais uncinata 14.667±6.443 (August 2007-July 2008), 14.417±5.017 (August 2008-July 2009). The least was Tellina nymphalis 0.583±1.505 (August 2007-July 2008); 0.333±0.651, (August 2008-July 2009). There was no significant variation in the mean values of the two years studied 5.900±0.4168 (August 2007-July 2008). 5.717±0.3704 (August 2008-July 2009).Seasonal variations occurred in the abundance of Dero sp. (11.00±5.20 wet, 17.71±3.72 dry), ＂Stylera lacustris＂ (11.82±5.15 wet, 18.50±10.57dry) and Eiseniella tetrahidra (18.76±9.16 wet, 15.00±4.69 dry). The other species did not show significant variation. However, there was significant variation between the mean of the wet season and that of the dry season 5.32±0.30 wet and 6.99±0.58, respectively.