Intertidal Polychaetes as Indicators of Pollution Resulting from Anthropogenic Activities along the Okpoka Creek, Upper Bonny Estuary, Nigeria

Abstract:

The Okpoka river and the Amadi creek are tributaries of the upper bonny estuary. The study is aimed at identifying the intertidal polychaete species and their abundance in these areas, and using them as indicators of pollution. Three stations were sampled for 6 months on a monthly basis at Marine Base, Abuloma and Kalio-Ama. Results gotten from Water samples collected from intertidal pools are as follows; Biochemical Oxygen Demand(BOD) (3.31-4.0)mg/l,, Dissolved Oxygen(DO) (6.40-6.44)mg/l, Conductivity (22.69-25.89)ms/cm, Total Dissolved Solids(TDS) (11.34-12.96)PPT, Salinity (13.65-15.74)PPT, pH (6.58-6.86), Turbidity (45.41-75.11)NTU, Temperature (28.30-31.82)oC, Nitrate(NO3) (2.11-4.10)mg/l, Phosphate(PO4) (0.82-1.10)mg/l, Sulphate(SO4,) (7.51-15.38)mg/l and Total Petroleum Hydrocarbon(TPH) (0.03-0.13)mg/l. The values of NO3, pH, Conductivity, TDS, Salinity showed significance in location and time. PO4 was significantly different between locations (p<0.05). BOD, SO4, TPH and DO showed significance in time while Turbidity and Temperature showed no significance. Results gotten from Analysis done for sediment nutrient parameters such as NO3(15.50-26.40)mg/l and PO4(13.32-15.90)mg/l showed significant variations in location and time, TPH(21.93-34.71)mg/l showed significant variations in location and SO4(15.85-19.71)mg/l had no significance in both location and time. Polychaete family and species identified in this study include: Eunicidae (Lumbrinereis aciculata, Lumbrinereis californiensis), Syllidae (Syllis ramosa, Syllis gracillis, Syllis armata), Capitellidae (Capitella Capitata), Spionidae, Glyceridae and Nereidae (Nereis diversicolor). The dry season witnessed a high number of polychaetes, about 65% of the total number of polychaetes collected from all study locations, while the wet season experienced a low count of about 34% of the total polychaetes collected from all sampled stations. The presence of lumbrinereis sp indicates negatively a poor benthic condition which was present with 25.8% abundance. The high abundance of Nereis sp with 45% abundance indicates heavy metals pollution and the presence of Glycera sp with 4% percentage abundance and Syllid sp with 15.6% percentage abundance indicates unpolluted conditions. In conclusion the abundance and diversity of polychaetes in Marine base, Abuloma and Kalio Ama were generally poor. This is evident by the poor abundance, composition and diversity of benthic fauna of the study area.