Abundance and distribution of nematodes in petroleum hydrocarbon polluted soil in Okrika Local Government Area, Rivers State, Nigeria

Abstract

This study examined the abundance of nematodes in petroleum hydrocarbon polluted soils in Okrika region. A total of 80 soil samples were collected at various depths in several sites of the region during the dry and rainy seasons. Three of the sites (Ekerekana, Ogoloma and Okari) were polluted by petroleum hydrocarbon while the control (Abam) was unpolluted. A total of 15 genera containing 749 individual nematodes were extracted from both polluted and unpolluted sites. The highest abundance was recorded at the control site, Abam with 327 (43.7%), followed by Ekerekana with 272 (36.3%), Ogoloma with 97 (12.9%) and Okari with 53 (7.1%) nematodes. In comparison to the dry season, more nematodes, 561 (74.9% out of total population) individuals were extracted during the wet season. During the wet season, nematode abundance was considerably higher (p<0.05) in the unpolluted site than those in polluted sites, but during the dry season, there was no significant difference (p>0.05) between the seasons. Similarly, more nematodes (51.3%) were extracted from the core depth of 0-5 cm than 6-10 cm (33.2%) and 11-15 cm (15.5%). At the depth of 0-5 cm, the control site had a significant (p<0.05) nematode abundance than the polluted sites while at the depths of 6-10 cm and 11-16 cm, although there was a higher numerical abundance of nematodes in the unpolluted sites than the control site, but these were not significant (p>0.05). This study showed that nematodes at the studied sites were relatively sensitive to petroleum hydrocarbon pollution especially at the depth of 0-5 cm in both dry and rainy seasons.